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Roberto ROSA
Professore Associato
Dipartimento di Scienze e Metodi dell'Ingegneria
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Pubblicazioni
2024
- Life cycle assessment of lattice structures: Balancing mass saving and productivity
[Articolo su rivista]
Colombini, Giulia; Rosa, Roberto; Ferrari, Anna Maria; Defanti, Silvio; Bassoli, Elena
abstract
Additive Manufacturing has revolutionized manufacturing processes, offering design flexibility and advances in various applications. The integration of lattice structures into lightweight designs has attracted attention due to their ability to optimize properties such as stiffness, strength and energy absorption. This paper explores the trade-off between mass reduction and productivity while evaluating the environmental sustainability of lattice structures manufactured with Laser-based powder bed fusion for metals Using Life Cycle Assessment, two design variants for an automotive component are compared: a topologically optimized version with a solid bulk section, and a second design with lattice structures for additional weight reduction. Experimental measurements and a detailed analysis of the laser strategy were performed to build the Life Cycle Assessment inventory. The integration of lattice structures allowed a weight reduction of 6 %, but resulted in a significant decrease in productivity and a higher environmental impact. Surprisingly, lattice geometries, often perceived as green solutions, can have negative sustainability implications due to longer manufacturing times and impact of auxiliary equipment. Successful implementation of environmentally sustainable designs requires a balance between mass reduction and productivity while addressing potential environmental consequences.
2023
- Flow-dependent shear stress affects the biological properties of pericyte-like cells isolated from human dental pulp
[Articolo su rivista]
Bertani, Giulia; Di Tinco, Rosanna; Bertoni, Laura; Orlandi, Giulia; Pisciotta, Alessandra; Rosa, Roberto; Rigamonti, Luca; Signore, Michele; Bertacchini, Jessika; Sena, Paola; De Biasi, Sara; Villa, Erica; Carnevale, Gianluca
abstract
Background: Human dental pulp stem cells represent a mesenchymal stem cell niche localized in the perivascular area of dental pulp and are characterized by low immunogenicity and immunomodulatory/anti-inflammatory properties. Pericytes, mural cells surrounding the endothelium of small vessels, regulate numerous functions including vessel growth, stabilization and permeability. It is well established that pericytes have a tight cross talk with endothelial cells in neoangiogenesis and vessel stabilization, which are regulated by different factors, i.e., microenvironment and flow-dependent shear stress. The aim of this study was to evaluate the effects of a pulsatile unidirectional flow in the presence or not of an inflammatory microenvironment on the biological properties of pericyte-like cells isolated from human dental pulp (hDPSCs). Methods: Human DPSCs were cultured under both static and dynamic conditions with or without pre-activated peripheral blood mononuclear cells (PBMCs). Pulsatile unidirectional flow shear stress was generated by using a specific peristaltic pump. The angiogenic potential and inflammatory properties of hDPSCs were evaluated through reverse phase protein microarrays (RPPA), confocal immunofluorescence and western blot analyses. Results: Our data showed that hDPSCs expressed the typical endothelial markers, which were up-regulated after endothelial induction, and were able to form tube-like structures. RPPA analyses revealed that these properties were modulated when a pulsatile unidirectional flow shear stress was applied to hDPSCs. Stem cells also revealed a downregulation of the immune-modulatory molecule PD-L1, in parallel with an up-regulation of the pro-inflammatory molecule NF-kB. Immune-modulatory properties of hDPSCs were also reduced after culture under flow-dependent shear stress and exposure to an inflammatory microenvironment. This evidence was strengthened by the detection of up-regulated levels of expression of pro-inflammatory cytokines in PBMCs. Conclusions: In conclusion, the application of a pulsatile unidirectional flow shear stress induced a modulation of immunomodulatory/inflammatory properties of dental pulp pericyte-like cells.
2023
- Life cycle assessment of chemical synthesis of genistein and its glucosyl derivatives to be employed in the modulation of angiogenesis of hepatocellular cancer
[Articolo su rivista]
Ruini, C.; Rigamonti, L.; Zanni, A.; Bertani, G.; Carnevale, G.; Ferrari, E.; Neri, P.; Ferrari, A. M.; Rosa, R.
abstract
This work is focused on the application of Life Cycle Assessment (LCA) methodology for the quantification of the potential environmental impacts associated to the obtainment of three glucosyl derivatives of genistein. Genistein is known to possess the ability in vitro to contribute to control signaling of some molecules like Angiopoietin-2 that has a key role in angiogenesis and fibrosis from which Hepatocellular cancer can arise. Therefore, a fine tuning of genistein uptake and bioavailability (e.g., through glycosylation) may provide innovative anti-angiogenic therapies with benefits for cancer chemoprevention and treatment.The production of pharmaceutical quality genistein, from which the derivatives are obtained, was modelled considering a recently optimized published procedure. The preparation of 7-O-(beta-Dglucosyl)genistein (or genistin) was experimentally conducted by exploiting a two-step synthetic protocol. During the work-up procedure, two further derivatives were isolated.In order to also comprise the potential human health benefits of the synthesized compounds, this work also proposes for the first time a potential damage assessment factor for genistein and its derivatives.
2023
- Life cycle impact assessment of solution combustion synthesis of titanium dioxide nanoparticles and its comparison with more conventional strategies
[Articolo su rivista]
Rosa, Roberto; Paradisi, Enrico; Gualtieri, Eva Magdalena; Mugoni, Consuelo; Cappucci, GRAZIA MARIA; Ruini, Chiara; Neri, Paolo; Ferrari, Anna Maria
abstract
This paper represents the first attempt to quantitatively and reliably assess the environmental sustainability of solution combustion synthesis (SCS) with respect to other soft chemistry strategies, which are more conventionally employed in the preparation of engineered oxide nanomaterials, namely hydrolytic and non-hydrolytic sol-gel syntheses (i.e., HSGS and NHSGS). Indeed, although SCS is well known to rely on significant reduction in the energy as well as time required for the obtainment of the desired nanocrystals, its quantitative environmental assessment and a detailed comparison with other existing synthetic pathways represents an absolute novelty of high scientific desirability in order to pursue a more sustainable development in the inorganic chemistry as well as materials science research fields. TiO2 nanoparticles were selected as the material of choice, for the production of which three slightly modified literature procedures were experimentally reproduced and environmentally evaluated by the application of the comprehensive Life Cycle Assessment (LCA) methodology. Particularly, SCS was compared from an environmental perspective with sol-gel approaches performed both in water and in benzyl alcohol. The results of the present study were also framed among those recently obtained in a systematic study assessing seven further chemical, physical and biological routes for the synthesis of TiO2 nanoparticles, comprising also flame spray pyrolysis (typically used in industrial productions), highlighting and quantifying the excellent environmental performances of SCS.
2022
- Microwave-assisted vacuum synthesis of tio2 nanocrystalline powders in one-pot, one-step procedure
[Articolo su rivista]
Paradisi, E.; Rosa, R.; Baldi, G.; Dami, V.; Cioni, A.; Lorenzi, G.; Leonelli, C.
abstract
A new method for fast and simple synthesis of crystalline TiO2 nanoparticles with photocat-alytic activity was developed by carrying out a classic sol–gel reaction directly under vacuum. The use of microwaves for fast heating of the reaction medium further reduces synthesis times. When the solvent is completely removed by vacuum, the product is obtained in the form of a powder that can be easily redispersed in water to yield a stable nanoparticle suspension, exhibiting a comparable photocatalytic activity with respect to a commercial product. The present methodology can, therefore, be considered a process intensification procedure for the production of nanotitania.
2022
- Principles and indicators for assessing the environmental dimension of sustainability within green and sustainable chemistry
[Articolo su rivista]
Rosa, R.; Pini, M.; Cappucci, G. M.; Ferrari, A. M.
abstract
In this current opinion, we travel through the evolution of the principles and indicators to assess environmental sustainability of chemical products and processes. Although the first ones were developed within Green Chemistry to account for the green characteristics of a chemical product/process, they are unable to quantify sustainability of that product/process, since they are more focused on synthetic aspects. These limitations, concurrently with the ever-greater pervasiveness of Sustainable Development, led to the development of more comprehensive principles, metrics, and indicators able to assess possibly all the phases of a chemical product/process life cycle, thus quantifying its environmental impact in a holistic manner, thus its belonging to Sustainable Chemistry (SC). This current opinion overviews these metrics/indicators limitedly to the environmental dimension of green and SC. Finally, the potentialities of selected metrics in covering the quantitative assessments of chemical products and processes circularity and their contributions to the seventeen Sustainable Development Goals, are highlighted.
2022
- Valorization of marble powder wastes using rice husk ash to yield enhanced-performance inorganic polymer cements: Phase evolution, microstructure, and micromechanics analyses
[Articolo su rivista]
Kamseu, E.; Akono, A. -T.; Rosa, R.; Mariani, A.; Leonelli, C.
abstract
The challenge for sustainable development is now constraining scientists, and policymakers to consider alternative materials and processes requiring low energy consumption and low emissions while prioritizing local materials and industrial waste recycling. This study investigates ways to valorize marble waste powders to design a new class of inorganic polymer cement. These powders are among the most important solid wastes globally, and in the Italian island of Sardinia they create a disposal problem. When these powders, which are rich in calcium silicate hydrate (C–S–H) phases, are incorporated into the geopolymer synthesis, this gives rise to a mix between C–S–H and alkali metal aluminosilicate hydrate (M-A-S-H) systems that are the focus of this study. In detail, C–S–H systems are prepared with various Ca/Si ratios, including CS, C2S, and C3S. The microstructure and mechanical properties are investigated using X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy, along with density methods (mercury intrusion porosimetry), macroscopy mechanical testing methods (flexural strength tests) and nanoscale mechanical testing methods (indentation testing and scratch testing). The resulting inorganic polymer cements exhibit both an amorphous and a crystalline phase containing sodium-calcium-aluminum-silicate hydrate N–C-A-S-H. The fraction of the crystalline phase increases when the silica content decreases, from CS to C3S, and when the C–S–H fraction increases. In turn, the crystalline phase dictates the pore structure and mechanical properties. Specifically, a homogeneous and compact microstructure with low porosity is observed. The flexural strength ranges from 5.8 to 8.7 MPa, the elastic modulus ranges from 10 to 17 GPa, and the fracture toughness ranges from 0.23 to 0.48 MPa m1/2. In general, the lower the silica percentage of the calcium-silicate hydrates and the higher the fraction of calcium silicate hydrate are, the higher the flexural strength, elastic modulus, and fracture toughness. The underlying mechanism for the observed stiffening, strengthening, and toughening is the insertion of aluminum in the C–S–H defect sites to yield C-A-S-H, along with the formation of sodium silicate gel from excess colloidal silica, which contributes to the reduction in gel pores and matrix densification. The values of porosity, density, and mechanical properties suggest that inorganic polymer cements derived from marble wastes are promising candidates for innovative low-temperature and low-density binders with low carbon footprint satisfying both the requirements of sustainability and the local material concept.
2021
- Biomass processing via microwave treatment
[Capitolo/Saggio]
Rosa, Roberto; Cravotto, Giancarlo; Leonelli, Cristina
abstract
2021
- Effect of isopropanol co-product on the long-term stability of TiO2 nanoparticle suspensions produced by microwave-assisted synthesis
[Relazione in Atti di Convegno]
Paradisi, E.; Rosa, R.; Baldi, G.; Dami, V.; Cioni, A.; Lorenzi, G.; Leonelli, C.
abstract
2021
- Environmental safety of the 180-W GreenLight Laser: a pilot study on plume and irrigating fluids
[Articolo su rivista]
Ferrari, Giovanni; Ferrari, Anna Maria; Campobasso, Davide; Modenese, Alberto; Rijo, Enrique; Misrai, Vincent; Rosa, Roberto; Cindolo, Luca
abstract
2021
- Green deep eutectic solvents for microwave-assisted biomass delignification and valorisation
[Articolo su rivista]
Grillo, G.; Gaudino, E. C.; Rosa, R.; Leonelli, C.; Timonina, A.; Grygiskis, S.; Tabasso, S.; Cravotto, G.
abstract
Aiming to fulfil the sustainability criteria of future biorefineries, a novel biomass pretreatment combining natural deep eutectic solvents (NaDESs) and microwave (MW) technology was developed. Results showed that NaDESs have a high potential as green solvents for lignin fractionation/recovery and sugar release in the following enzymatic hydrolysis. A new class of lignin derived NaDESs (LigDESs) was also investigated, showing promising effects in wheat straw delignification. MW irradiation enabled a fast pretreatment under mild condition (120 °C, 30 min). To better understand the interaction of MW with these green solvents, the dielectric properties of NaDESs were investigated. Furthermore, a NaDES using the lignin recovered from biomass pretreatment as hydrogen bond donor was prepared, thus paving the way for a “closed-loop” biorefinery process.
2021
- Latent fingermarks and electrochemistry: possibilities for development and aging studies
[Capitolo/Saggio]
Rosa, Roberto; Mugoni, Consuelo; Bononi, Massimiliano; Giovanardi, Roberto
abstract
2021
- Management of Asbestos Containing Materials: A Detailed LCA Comparison of Different Scenarios Comprising First Time Asbestos
Characterization Factor Proposal
[Articolo su rivista]
Pini, Martina; Scarpellini, Simone; Rosa, Roberto; Neri, Paolo; Gualtieri, Alessandro; Ferrari, Anna Maria
abstract
This work addresses the complex issue of asbestos containing materials (ACMs) management, by focusing on the scenario of six municipalities comprised in the Reggio Emilia province of Emilia Romagna Italian region. Particularly, the life cycle assessment (LCA) methodology was applied in order to assess in a quantitative and reliable manner the human toxicity as well as the ecotoxicity impacts associated with all of the different phases of ACMs management. The latter comprises mapping of ACMs, creation of a risk map for defining priority of intervention, encapsulation and removal of ACMs, as well as the as obtained asbestos containing waste (ACW) end of life. Particularly, a thermal inertisation treatment performed in a continuous industrial furnace was considered as the innovative end of life scenario to be compared with what actually was provided by the legislation of many countries worldwide, that is, the disposal of ACW in a controlled landfill for hazardous wastes. A characterization factor for asbestos fibers released both in outdoor air and in occupational setting was proposed for the first time and included in the USEtox 2.0 impact assessment method. This allowed us to reliably and quantitatively highlight that inertisation treatments should be the preferred solutions to be adopted by local and national authorities, especially if the obtained inert material finds application as secondary raw materials, thus contributing to a decrease in the environmental damage (limited to its toxicological contributions) to be associated with asbestos management.
2021
- Marble wastes recycling: Design and synthesis of low-temperature calcium silicate hydrate under various CaO:SiO2 ratio and alkalinity
[Articolo su rivista]
Kamseu, E.; Alzari, V.; Rosa, R.; Nuvoli, D.; Sanna, D.; Mariani, A.; Leonelli, C.
abstract
Marble sludge wastes (MSW) are investigated as solid precursors for the production of low-temperature calcium silicate hydrate (CSH). Calcined powder of MSW is ball-milled with rice husk ash (RHA) and the slurries are treated in the oven at 100°C for 24 h in a context where water evaporation is minimized. The initial CaO:SiO2 molar ratio varies from 1 to 3 (CS, C2S and C3S) and the solution used for the preparation of the calcium silicate hydrate presents NaOH with concentration of 0, 1, 2 and 3 N. FTIR, XRD, Particle size distribution, BET surface area and Environmental Scanning Electron Microscope (ESEM) permitted to confirm the formation of CSH(I) at 100°C through pozzolanic reactions. The increase of the alkalinity of the solution improves the silica dissolution and enhances the formation of CxS and CSH up to 2N. Further increase of the alkalinity affected the silica polymerization, the particle size and the concentration of CSH into the final matrix. The precursor with CaO:SiO2 = 1 seems to promote C-S-H(I) with more monomers while 2CaO:SiO2 and 3CaO:SiO2 resulted in orthosilicate chains and interlayer respectively. The high reactivity and fine particles (diametre < 32 nm) of CSH obtained appeared promising for the design of low-cost, environmentally-friendly and sustainable binders as well as others engineering applications including binder and concrete seed, refractory precursors, hydroceramics, insulating matrices, filtration and catalysis.
2021
- MICROWAVE SINTERING OF SODIUM-β -ALUMINA: EXPERIMENTAL AND NUMERICAL SIMULATION RESULTS
[Relazione in Atti di Convegno]
Rosa, R.; Mortalo, C.; Veronesi, P.; Fasolin, S.; Zin, V.; Deambrosis, S. M.; Miorin, E.; Dimitrakis, G.; Fabrizio, M.; Leonelli, C.
abstract
2021
- NEW APPLICATORS FOR THE PROJECT SIMPLIFY: SONICATION AND MICROWAVE PROCESSING OF MATERIAL FEEDSTOCK
[Relazione in Atti di Convegno]
Veronesi, P.; Colombini, E.; Poppi, G.; Rosa, R.; Dami, V.; Cioni, A.; Lorenzi, G.; Baldi, G.; Leonelli, C.
abstract
2021
- Synthesis and characterization of (68-x) CuO – xV2O5 – 32TeO2 (x = 0–68 mol%) and (35-x) CuO – xV2O5 – 65TeO2 (x = 0–35 mol%) glasses: Conduction mechanism, structure and EPR study
[Articolo su rivista]
Mugoni, C.; Rosa, R.; Giovanardi, R.; Affatigato, M.; Gualtieri, M. L.; Siligardi, C.; Andronenko, S. I.; Misra, S. K.
abstract
In this work, two series of glasses, i.e. (68-x) CuO – xV2O5 – 32TeO2 (x = 0–68 mol%, Te32 series) and (35-x) CuO – xV2O5 – 65TeO2 (x = 0–35 mol%, Te65 series), were synthesized by the melt-quenching method and subjected to physical, thermal and electrical characterization. Their vitreous nature was confirmed by X-Ray diffraction and differential scanning calorimetry, while their structural units were determined by Raman spectroscopy. CuO substitution by V2O5 led to a decrease in density and glass-transition temperature, together with a conductivity increase. Conduction mechanism was interpreted as mainly due to small polaron hopping from the lower (V4+) to the higher (V5+) vanadium valence states. Te32 glasses, possessing the highest electronic conductivities (ranging from 2 E−4 to 5 E−7 Ω−1 cm−1), were investigated by the Electron Paramagnetic Resonance technique, in order to more deeply analyze their structure-conductivity correlation. Particularly, the observed signals were determined to consist in a superposition of a first line due to paramagnetic Cu2+ ions and a second line due to exchange-coupled CuO clusters. Differences in the spectra were determined between samples with higher (i.e. 20-30 mol%) Cu2+ concentrations and samples with lower Cu2+ concentrations, suggesting they are located in different local environments. Finally, it was found that the Cu2+ ions are not involved in the process of electron transfer.
2021
- Use of combustion synthesis/self-propagating high-temperature synthesis (SHS) for the joining of similar/dissimilar materials
[Capitolo/Saggio]
Rosa, Roberto; Veronesi, Paolo; Leonelli, Cristina
abstract
2020
- Effect of frequency on MW assisted sintering: 2.45 GHz versus 5.8 GHz
[Articolo su rivista]
Gil-Flores, L.; Salvador, M. D.; Penaranda-Foix, F. L.; Fernandez, A.; Suarez, M.; Rosa, R.; Veronesi, P.; Leonelli, C.; Borrell, A.
abstract
Innovative non-conventional approaches, such as microwave sintering, are being developed as a method for sintering a variety of materials which shown advantages over conventional sintering procedures. This work involves an investigation of the microwave sintering of an ATZ composite with two different microwave applicators and frequency generators: 2.45 GHz and 5.8 GHz. Zirconia doped with ceria and toughened with alumina (10Ce-TZP/Al2O3) is the composite used in this study. The samples were sintered by microwave in air at 1200 and 1300 °C with 10 min of dwell time at 2.45 and 5.8 GHz in order to evaluate their effects on sintering, using an optimized experimental configuration. In addition, the mechanical properties of MW-sintered samples were compared with those obtained for the same composites sintered by the conventional method (1500 °C/120 min), such as relative density, hardness and fracture toughness.
2020
- Effect of isopropanol co-product on the long-term stability of TiO2 nanoparticle suspensions produced by microwave-assisted synthesis
[Articolo su rivista]
Paradisi, E.; Rosa, R.; Baldi, G.; Dami, V.; Cioni, A.; Lorenzi, G.; Leonelli, C.
abstract
In this paper we evaluate the effect of isopropanol arising from the reagent Ti(O-iPr)4 on the long-term stability of nanoparticle size of TiO2 produced during a microwave assisted sol-gel synthesis. Different configurations of microwave apparatus have been considered: the synthesis was carried out both in vessel or flask, and both performing or not isopropanol distillation through a modified microwave apparatus. Results revealed that isopropanol distillation after a short reaction time provided suspensions with slightly smaller particle size, that also show longer stability over time, especially for syntheses carried out at certain temperatures. Reactions performed distilling isopropanol from vessel and flasks showed comparable results, superior to the corresponding suspensions obtained without distilling isopropanol. This study is intended to provide a useful contribution to those applications where the need for stable TiO2 suspensions is critical.
2020
- LCA application to chemical synthesis at laboratory scale
[Capitolo/Saggio]
Pini, M.; Rosa, R.; Neri, P.; Ferrari, A. M.
abstract
Although a huge number of Green Chemistry metrics are available and more simply applicable with respect to LCA, their intrinsic less comprehensive nature could in some cases represent a limiting factor for a trustworthy evaluation of the environmental and human health impacts assessment associated to that specific chemical. Therefore, all of the chemical processes not specifically based on a chemical reaction (e.g., the extraction of a particular phytochemical compound from plant matrices) are far from being assessed by most of these metrics. LCA methodology-based evaluations for chemical processes are not limited by a mere chemical reaction equation, being also able to account for time and energy contributions together with all of the possible environmental loads associated to a particular process or product. This chapter will first overview the most widely employed Green Chemistry metrics. The possibility to integrate those metrics with the all-encompassing LCA methodology will be also accurately and critically discussed. This chapter will also furnish important recommendations and guidelines on when and at which extent the application of LCA should be highly suggested at a laboratory scale.
2020
- Life Cycle Assessment of Chemical vs Enzymatic-Assisted Extraction of Proteins from Black Soldier Fly Prepupae for the Preparation of Biomaterials for Potential Agricultural Use
[Articolo su rivista]
Rosa, R.; Spinelli, R.; Neri, P.; Pini, M.; Barbi, S.; Montorsi, M.; Maistrello, L.; Marseglia, A.; Caligiani, A.; Ferrari, A. M.
abstract
The cradle-to-grave life cycle assessment (LCA) was applied to the preparation of biomaterials derived from proteins, extracted from black soldier fly (BSF) prepupae, after the larvae were reared on poultry manure-based organic waste. To obtain higher value-added biomolecules, extraction represents the fundamental step. Therefore, the environmental sustainability assessments of different extraction/fractionation procedures were compared. In this way, it is possible to consider also their environmental performances in addition to the purity, yield, and integrity of the extract. A chemical method characterized by a one-step protein extraction was compared to an enzymatic-assisted protocol, employing Bacillus licheniformis protease. Surprisingly, the enzymatic approach resulted for the 31.87% more environmentally impacting with respect to the chemical method, despite its lack of organic solvents and reduction of alkaline and acid solutions employed. Particularly, the long time necessary for the enzymatic hydrolysis significantly contributed to the environmental impact of this protocol. Therefore, improvements such as biomass pretreatment procedures or the use of different proteolytic enzymes (e.g., operating at lower temperatures and in shorter times) are needed. Moreover, to reduce the environmental load of the protein fraction, attention should also be given to increase extraction yields of lipids and chitin biomolecules obtainable from BSF prepupae, due to the biorefinery approach under which this study was considered.
2020
- Microwave assisted sintering of Na-β’’-Al2O3 in single mode cavities: Insights in the use of 2450 MHz frequency and preliminary experiments at 5800 MHz
[Articolo su rivista]
Mortalo, C.; Rosa, R.; Veronesi, P.; Fasolin, S.; Zin, V.; Deambrosis, S. M.; Miorin, E.; Dimitrakis, G.; Fabrizio, M.; Leonelli, C.
abstract
Microwave assisted sintering of Na-β’’-Al2O3 in single mode cavities was accurately investigated. The use of single mode cavity allowed monitoring the parameters affecting the sintering process, like the forward power, together with the temperature evolution, making possible to perform energy efficiency and specific energy consumption evaluations. Experiments have been performed at the frequency of 2450 MHz, but preliminary results are also reported using the higher frequency of 5800 MHz, in order to investigate its effect on important parameters like the power density distribution as well as the penetration depth, which are responsible of the resulting heating rate and sintering outcome. Dielectric properties of the powders were measured as a function of temperature in order to partially predict and support the understanding of their experimental heating behaviour. Furthermore, dielectric properties provide the fundamental information needed for the multiphysics numerical simulation, performed with the aim to reach insights into the power density evolution in the specimen as sintering proceeds.
2020
- On the effect of steel substrate alloying elements on the in-situ formation of intermediate thermal diffusion barrier layers
[Articolo su rivista]
Rosa, R.; Veronesi, P.; Casagrande, A.
abstract
The aim of this work was to evaluate the feasibility of a hot-dipping aluminizing process, for the simultaneous production of an iron aluminide coating, a protective alumina topcoat layer and an intermediate thermal diffusion barrier layer, at the aluminide coating/steel substrate interface, the latter being thought in order to limit the detrimental depletion of Al content in the coating layer as a consequence of its inward diffusion towards the substrate. Indeed, the steel substrates were opportunely selected for their high weight percentages of alloying elements (namely Ni, Cr, Mn and Co) potentially able to diffuse from the substrate and react with the inward diffusing Al at the temperatures employed in the coating preparation, thus forming transition metal aluminides able to stop Al depletion, thus potentially prolong the lifetime of iron aluminide coatings in service. The effective in-situ growth of this intermetallic thermal diffusion layer was found to be strictly dependent on several factors, including the enthalpy of formation of the alloying-element aluminides, together with the atomic percentages of the selected alloying element in the steel substrate as well as its diffusion rate. The obtained results, can be considered an important contribution to the selection criteria of iron aluminides-coated steel substrates, to be employed in burdensome scenarios at high temperatures.
2020
- Opportune inward waste materials towards a zero waste ceramic slabs production in a circular economy perspective
[Articolo su rivista]
Mugoni, Consuelo; Rosa, Roberto; Remigio, Vito A.; Ferrari, Anna Maria; Siligardi, Cristina
abstract
This work is related to the preliminary lab‐scale preparation of ceramic slabs, reproducing the characteristics of natural stones, containing up to more than 40 wt.% of different waste materials, namely laboratory glass, cullet glass (both thought as fluxing agents replacing feldspar), and ceramic waste obtained from drying squaring operations (for partial quartz sand replacement). Indeed, in order to pursue the circular economy principles, the possibility of turning different kinds of wastes into resources for the ceramic industry, surely represents the first concern to be addressed and demonstrated, with also the aim to reduce the environmental impact associated with landfill, minimizing manufacturing cost and contributing to preserve nonrenewable natural resources, which are known to be consistently depleted by the ceramic
industries
2020
- Preliminary Thermal Investigations of Calcium Antimonate Opacified White Glass Tesserae
[Articolo su rivista]
Boschetti, Cristina; Leonelli, Cristina; Rosa, Roberto; Romagnoli, Marcello; Valero Tévar, Miguel Ángel; Schibille, Nadine
abstract
Calcium antimonate (in the hexagonal or cubic form) dispersed in the glass matrix is an artificially synthesized phase commonly documented as opacifier for white glasses during the Roman period. Glasses of this type occasionally contain variable amounts of lead oxide. There is no consensus about the origin and role of the lead component in white glasses, whether it was functional to modify the workability of the glass and/or to help the precipitation of the particles, or whether it was an unintentional pollutant introduced with the raw materials. A group of lead and lead-free white mosaic tesserae from the fourth-century CE villa of Noheda in Spain were analyzed by differential scanning calorimetry (DSC) and high temperature X-ray diffraction (HTXRD) to evaluate the impact of variable amounts of lead oxide in the precipitation of calcium antimonate on the viscosity of the glass. The analyzed glasses show thermal events that have been related to the composition of the glass via multicomponent linear regression model. CaSb2O6 and Ca2Sb2O7 formed in the glass during the cooling phase and the glass was not reheated. Lead oxide influences the thermal behavior of the glass, lowering the onset temperatures of all the events, implying a more cost-effective production process. We propose that lead was added intentionally or that lead-bearing raw materials were selected specifically by the ancient glass artisans
2020
- Rapid microwave synthesis of magnetocaloric Ni–Mn–Sn Heusler compounds
[Articolo su rivista]
Trombi, L.; Cugini, F.; Rosa, R.; Amade, N. S.; Chicco, S.; Solzi, M.; Veronesi, P.
abstract
The magnetocaloric Ni50Mn25Sn25 Heusler compound was prepared via ultra-fast and sustainable microwave synthesis, by using the two ways hybrid microwave heating method. The structural, microstructural, magnetic and magnetocaloric properties of the prepared specimen are presented. The functional features of the synthetized sample result comparable with compounds obtained with other high-temperature preparation techniques that require larger amount of energy. The proposed time and energy-efficient preparation method could promote the development of large mass production routes of multifunctional huge-potential Heusler compounds, exploitable as active materials in thermomagnetic energy conversion machines and in other technological applications.
2020
- Relating type of mold materials to crystal morphology and properties of glass-ceramics with YSZ additions as a dental material
[Articolo su rivista]
Angkulpipat, S.; Srichumpong, T.; Prasertwong, S.; Meechoowas, E.; Sirinukunwattana, K.; Heness, G.; Rosa, R.; Suputtamongkol, K.; Chaysuwan, D.
abstract
YSZ was added to glass frit in order to improve properties of the glass-ceramic dental materials by casting into a graphite mold and a cast iron mold and then crystallized via heat treatment. XRD results presented the similar crystalline phases of phlogopite-calcium mica and tetragonal zirconia in both molds. Microstructures by SEM showed the different crystal morphology due to casting molds. The slow cooling of graphite mold produced the equiaxed crystals whereas the fast cooling of cast iron mold promoted rod-like, and YSZ addition increased the number of crystals. The properties depended on the crystal morphology and crystallinity. The 5 wt% YSZ added glass-ceramic from graphite mold developed the equiaxed crystals to present the desirable properties of 147.15 MPa, flexural strength, 251.80 µg/cm2, chemical solubility and 9.26 × 10-6/°C CTE. The results were accepted by ISO 6872:2015 (Dentistry-Ceramic Materials) in type II class 2b as a partially and fully covered single substructure and matched with commercial porcelains.
2019
- In vitro surface reaction in SBF of a non-crystalline aluminosilicate (geopolymer) material
[Articolo su rivista]
Tippayasam, C.; Sutikulsombat, S.; Kamseu, E.; Rosa, R.; Thavorniti, P.; Chindaprasirt, P.; Leonelli, C.; Heness, G.; Chaysuwan, D.
abstract
Geopolymer is a non-crystalline material based on aluminosilicate reaction exhibiting ceramic-like properties. It showed the possibility to use geopolymer as biomaterials by soaking in SBF solution to induct carbonate apatite onto the surface of samples. Carbonate apatite possesses good biocompatibility and bioactivity. The aims of this research were to study the geopolymer synthesis as a biomaterial to replace bones and the effects of Ca/P ratio on bioactivity properties of metakaolin-based geopolymers. For in vitro bioactivity test, the samples were soaked in SBF to study the influence of Ca(OH) 2 contents on the surface reaction. The 14, 28, and 90 day-soaked sample surfaces were investigated using SEM, XRD, and FTIR characterization. The compressive strength of samples was also tested. The SEM micrographs revealed that the increase of Ca/P ratio resulted in the increase of the carbonate apatite on sample surfaces. FTIR results confirmed that the formation of Ca 10 (PO 4 ) 3 (CO 3 ) 3 (OH) 2 was investigated.
2019
- Low temperature degradation behaviour of 10Ce-TZP/Al2O3 bioceramics obtained by microwave sintering technology
[Relazione in Atti di Convegno]
Gil, L.; Salvador, M. D.; Penaranda-Foix, F. L.; Rosa, R.; Veronesi, P.; Leonelli, C.; Borrell, A.
abstract
Zirconia is one of the most used ceramics, especially for biomedical applications, due to its exceptional mechanical properties. However, it is commonly known that its properties can be diminished owing to a low temperature degradation (LTD). This phenomenon consists on a spontaneous phase transformation, from tetragonal to monoclinic, under certain conditions, which is accelerated when the samples are exposed under high levels of humidity at a temperature range between 20-300 ºC. In addition to the fact that the monoclinic phase presents worse mechanical properties than the tetragonal one, there is a volume change of 4% between phases that gives rise to defects in the material as microcracks. Due to this reason, zirconia prostheses failed catastrophically inside the human body between 1999 and 2001 (1). Previous researches reveal that Al2O3 addition suppress the propagation of phase transformation (2). Thus, the aim of the present work is to study the hydrothermal ageing of zirconia doped with ceria and toughened with alumina (10Ce-TZP/Al2O3) composite, which has been sintered by microwave employing two different frequencies: 2.45 and 5.8 GHz. Microwave heating technology is based on the absorption of electromagnetic radiation by the material, which allows the sample to be heated. So far, most microwave heating equipments use 2.45 GHz; accordingly, the novelty of this study is to employ a frequency of 5.8 GHz and to investigate its effect on LTD. LTD is carried out in an autoclaved in steam at 120 ºC and 1.2 bar, because these conditions accelerate the hydrothermal aging process (3). In order to characterize the degraded samples, micro-Raman spectroscopy, AFM, nanoindentation technique and electronic microscopy have been performed.
References
1. Norton, M. R., Yarlagadda, R., Anderson, G. H. J. Bone Joint Surg. Br., 2002, 84–B, 631–635.
2. Fabbri, P., Piconi, C., Burresi, E., Magnani, G., Mazzanti, F., Mingazzini, C. Dent. Mater., 2014.
3. Presenda, Á., Salvador, M. D., Moreno, R., Borrell, A. J. Am. Ceram. Soc., 2015, 98, 3680–3689.
2019
- Microstructure and mechanical properties of 5.8 GHz microwave-sintered ZrO2/Al2O3 ceramics
[Articolo su rivista]
Gil-Flores, L.; Salvador, M. D.; Penaranda-Foix, F. L.; Fernandez, A.; Suarez, M.; Rosa, R.; Veronesi, P.; Leonelli, C.; Borrell, A.
abstract
Aim of the present study is to sinter zirconia nanocomposite powders doped with ceria and toughened with alumina (10Ce-TZP/Al2O3) by non-conventional means, i.e. microwave sintering technology. The sintering effects of various microwave applicators and frequency generators were evaluated using an optimised experimental set-up. The microwave-sintered samples were compared with the composites sintered by the conventional method. The mechanical properties of the ceramic composites were evaluated by their hardness, fracture toughness and Young's modulus. Likewise, their density and microstructure were analysed.
2019
- Microwave sintering of SiAlON ceramics with TiN addition
[Articolo su rivista]
Canarslan, O. S.; Rosa, R.; Koroglu, L.; Ayas, E.; Kara, A.; Veronesi, P.
abstract
α-β SiAlON/TiN composites with nominal composition of α:= β25:75 were fabricated by microwave sintering. The effect of titanium nitride addition on the phases, microstructure, microwave absorption ability and mechanical properties (Vickers hardness and fracture toughness) of the SiAlON-based composites were studied. Finite Difference Time Domain (FDTD) software was used for the numerical simulation in order to assess the most suitable experimental setup. Sintering trials were performed in a single mode microwave furnace operating at 2.45 GHz and a power output of 660W, for a reaction time of 30 min. SiC blocks were used as a susceptor to accelerate the microwave processing by hybrid heating, with reduced heat losses from the surface of the material of the α- βSiAlON/TiN composites. The optimum comprehensive mechanical properties, corresponding to a relative density of 96%, Vickers hardness of 12.98 ± 1.81 GPa and Vickers indentation fracture toughness of 5.52 ± 0.71 MPa.m1/2 were obtained at 850°C when the content of TiN was 5 wt.%.
2019
- On the versatility and distinctiveness in the use of microwave energy for the ignition of low exothermic Ni–Ti intermetallics combustion synthesis
[Articolo su rivista]
Rosa, R.; Trombi, L.; Casagrande, A.; Cugini, F.; Leonelli, C.; Veronesi, P.
abstract
Microwave energy has been employed in the present work in order to reach ignition of the combustion synthesis in the binary Ni–Ti system without the need of any separate additional pre-heating step. Indeed, the latter is known to be necessary with more conventional ignition strategies, due to the low exothermic character of the reaction between elemental Ni and Ti powders. On the opposite, the unique microwaves heating mechanism allows directly transferring electromagnetic energy in the reactive specimen that absorbs and transforms it into the heat necessary to reach ignition of the exothermic reaction. According to the electromagnetic field distribution inside the microwave single mode applicator employed, it was possible to realize both Thermal Explosion (TE) and Self-propagating High-temperature Synthesis (SHS) ways of combustion. Moreover, the use of a single mode applicator also allowed separately investigating the effect of electric and magnetic fields strengths, at the 2450 MHz microwave frequency, on the combustion characteristics. This significantly affected the microstructure as well as the phase evolution in the synthesized products.
2018
- From Field to Shelf: How Microwave-Assisted Extraction Techniques Foster an Integrated Green Approach
[Capitolo/Saggio]
Rosa, Roberto; Ferrari, Erika; Veronesi, Paolo
abstract
Microwave-assisted extraction of organic compounds from vegetal matrixes is a relatively
young ield of research. The exceptional results achievable at the laboratory scale by microwave-assisted extraction, like shorter extraction times, lower average temperatures, reduction of organic solvents use, higher yields and selectivity, as well as energy and cost saving,
are not always accompanied by a successful scale up. Nevertheless, microwave-assisted
techniques of extraction have been multiplying during last decades. In this framework,
a deeper knowledge of microwave applicator design criteria is mandatory. This chapter
starts from the basis of microwave heating and the relevant material properties involved in
a successful microwave-assisted extraction application, to continue with a short overview
on how such properties can be measured and used to optimize the experimental setup or
a possible scale up of the process under investigation. A comprehensive review of recent
applications of microwave-assisted extraction, applied to vegetal matrixes, is presented
next. The chapter ends reviewing duplex treatments of vegetal matrixes for extraction
purposes, where microwave heating is coupled to other techniques, like ultrasounds, and
indicating new paths, where the recent advent of new microwave solid-state generators
has led to beter process control and higher yields and energy efficiency.
2018
- High entropy alloys obtained by field assisted powder metallurgy route: SPS and microwave heating
[Articolo su rivista]
Colombini, E.; Rosa, R.; Trombi, L.; Zadra, M.; Casagrande, A.; Veronesi, P.
abstract
The aim of this work was to investigate the field assisted powder metallurgy route for producing HEAs at equimolar composition, i.e. FeCoNiCrAl, starting from metal powders. Both mixed, mechanically activated and mechanically alloyed powders have been used. The powders obtained by mechanical alloying were synthesized only by SPS, whereas the remaining ones were sintered by SPS or microwave heating. The investigated field assisted sintering techniques allowed an extremely short alloying time, high energy density on the load and negligible contamination by the surrounding environment. Both the conducted sintering-synthesis technology resulted not definitive to produce chemical homogeneity and to obtain a single stable structure. Thus a subsequently heat treatment was required. The post heat treatment, indeed, led to a single crystalline structure (FCC) and the material was fully recrystallized. After heat treatment samples are isomorphic: they exhibit two different phases with the same FCC cell, but different chemical composition, in detail Fe-Cr richer and Al-Ni richer. SPS-ed samples present a reduced porosity, while microwave processed ones are much more porous and this is reflected in the mechanical properties.
2018
- Microstructure and engineering properties of Fe2O3(FeO)-Al2O3-SiO2 based geopolymer composites
[Articolo su rivista]
Kaze, R. C.; Beleuk a Moungam, L. M.; Cannio, M.; Rosa, R.; Kamseu, E.; Melo, U. C.; Leonelli, C.
abstract
The objective of this study is to develop low cost, eco-friendly and sustainable building materials by applying the technology of mineral polymerization (geopolymerization) process on naturally abundant iron-rich aluminosilicate (laterite) materials. Iron-rich aluminosilicates based-geopolymer composites containing 10 to 40 wt% of rice husk ash (RHA) were cured at room temperature and at 90 °C. This paper examines the phase transformation, microstructural and mechanical changes that occur in the geopolymer composites when fine aggregates of quartz sand are added. Experimental results indicate good polycondensation and more cohesion resulting in high strength due to the better dissolution of RHA that provides soluble reactive silica to equilibrate the Si/Al and Si/Fe molar ratios. Ferro-sialates, Fe(Al)–S–H, were identified at the room temperature in addition to polysialates, S–A-N–H, phases. The flexural strength of resultant composites increases from 10 to 12 MPa for room temperature curing to ∼40 MPa when the composites were cured at about 90 °C as from the intensive formation of ferrisilicates. The formation of ferri-silicates that changed the flexural strength and microstructure seem to play significant role in the engineering properties of laterites based geopolymer composites making them promising candidates for applications as pavements, roads and building construction.
2018
- SPS-assisted Synthesis of SICp reinforced high entropy alloys: reactivity of SIC and effects of pre-mechanical alloying and post-annealing treatment
[Articolo su rivista]
Colombini, E.; Lassinantti Gualtieri, M.; Rosa, R.; Tarterini, F.; Zadra, M.; Casagrande, A.; Veronesi, P.
abstract
In this work a traditional high entropy alloy (FeCoNiCrAl) was reinforced by uniformly distributed reactive silicon carbide (SiC) particles by a powder metallurgy synthetic route, using as precursors simply mixed powders or mechanically prealloyed ones. The reactive sintering produced a single isomorphic BCC structure. The sample microstructure resulted equiassic, more homogenous in samples based on prealloyed powders. The instability of SiC in the presence of metal precursors resulted in the formation of more stable carbides and silicides, as well as in carbon diffusion in the high entropy alloy matrix and partially unreacted SiC particles. The formation of these newly formed fine precipitates, as well as the presence of residual SiC were useful to increase the hardness of the alloy.
2017
- A new multi principal element alloy synthesized by microwave powder metallurgy technique
[Relazione in Atti di Convegno]
Colombini, E.; Rosa, R.; Poletti, M. G.; Battezzati, L.; Casagrande, A.; Veronesi, P.; Leonelli, C.
abstract
Multi principal element alloys (MPEAs), consisting of five or more alloying elements at near equiatomic concentrations and forming bcc and/or fcc solid solution phase, were recently developed. According to the literature research, the synthetic route to produce MPEAs should guarantee short alloying time, efficient cooling and capability to operate in controlled atmosphere. Such conditions can be achieved using high frequency electromagnetic fields, like in microwave heating. Microwave assisted combustion synthesis of pure metal powders mixtures as reactants has already been used during the last decade by the authors to prepare intermetallics, functionally-graded materials, and recently to produce multi-principle alloys. Moreover the addition of SiC in these alloys increases the mechanical properties and oxidation resistance at high temperature, as demonstrated in a recent paper by the authors. In this work a new MPEA (Al15Mn20Fe25Co15Ni25) was prepared with and without the addition of SiC, using powder metallurgy route and exploiting microwave as way of generating heat inside the precursors and hence to start the reactive sintering. Results show that direct microwave heating at 2450 MHz of the powder precursors leads to the ignition conditions, with an evident exothermal event ascribable to the mixing enthalpy, and then self-sustaining of the synthesis occurs. The temperature and duration of the microwave-assisted process resulted much lower than other conventional powder metallurgy routes, but at the cost of a higher residual porosity. Sample characterization confirmed that the powder metallurgy approach is suitable to retain the shape of the load imparted during forming by uniaxial pressing.
2017
- Electrochemical impedance spectroscopy: A deeper and quantitative insight into the fingermarks physical modifications over time
[Articolo su rivista]
Rosa, Roberto; Giovanardi, Roberto; Bozza, Andrea; Veronesi, Paolo; Leonelli, Cristina
abstract
The present work is focused on a novel approach for the study and quantification of some of the physical changes to which a fingermark deposited on non-porous substrates is subjected as its ageing proceeds. Particularly, electrochemical impedance spectroscopy (EIS) technique has been applied for the first time in order to monitor the electrochemical behaviour of the system constituted by the fingermark residue and the underlying substrate. The impedance spectra proved to be significantly affected by the presence of the mark residue as well as by its ageing process. Opportune fitting operations performed on the experimental data allowed obtaining quantitative electrochemical parameters used to reach useful information on the fingermarks ageing mechanism as well as to calculate the fingermark ageing curves from which fundamental information could be potentially extrapolated.
2017
- Environmental sustainability assessment of a new degreasing formulation for the tanning cycle within leather manufacturing
[Articolo su rivista]
Rosa, R.; Pini, M.; Neri, P.; Corsi, M.; Bianchini, R.; Bonanni, M.; Ferrari, A. M.
abstract
The degreasing or defatting phase represents one of the most environmentally impacting steps in the
entire leather manufacturing cycle. Indeed, the chemical compounds conventionally employed during
this activity are significantly impacting, mainly as a consequence of their scarcity and slow biodegradability.
The present work represents a limited part of the European Life+ project titled, “Environmentallyfriendly
natural products instead of chemical products in the degreasing phase of the tanning cycle”,
which aims at proposing innovative degreasing formulations based on chemical compounds of natural
origin. Particularly, newly synthesised lactose derivatives were thought to partially replace ethoxylated
alcohols typically employed in commercial products. The aim of the present work is to present detailed
and quantitative environmental assessments of the laboratory-scale preparation of the most promising
formulation tested, designated EDF 20. This innovative formulation is based on a piperazinyl hydrochloride
derivative of lactose, for which a four-step synthetic protocol has been optimized, and which was then
mixed, in the last preparatory step, with further components to obtain an aqueous degreasing formulation
with a reduced ethoxylated alcohol content. A preliminary environmental assessment limited to the
chemical point of view was performed by employing the software EATOS (Environmental Assessment
Tool for Organic Syntheses) in order to evaluate all of the chemicals used in the synthesis of the lactose
derivative and in its work-up procedures. In order to assess the whole environmental and human health
impacts associated with the production of the defatting agent, thus performing a cradle-to-grave analysis,
the Life Cycle Assessment (LCA) methodology was applied, with the aim of furnishing quantitative and
trustworthy data also related to further fundamental impact categories, such as those comprising energy
consumption. This work represents the first example of an environmental assessment related to one
efficient alternative to the conventional degreasing procedure within the leather manufacturing cycle. It
will hopefully smooth the way towards the quantitative assessments of further alternative defatting procedures/
products, which are proposed practically on a daily basis with the aim of significantly reducing
the environmental loads of this tremendously impacting industrial activity.
2017
- Microwave energy application to combustion synthesis: A comprehensive review of recent advancements and most promising perspectives
[Articolo su rivista]
Rosa, R.; Trombi, L.; Veronesi, P.; Leonelli, C.
abstract
Microwave heating fundamentally differs from other heating techniques as the consequence of its unique characteristic of being based on the electromagnetic energy transfer from the microwaves source to the interacting material, which according to its electric, dielectric, and magnetic properties can convert the absorbed energy into heat. This peculiar heating mechanism is at the basis of plenty of unquestionable advantages that were reported during the last three decades in most of the different branches of chemistry as well as materials science, thus including also combustion synthesis. After a brief overview of the microwave heating fundamentals as well as of the different components constituting the scientific microwave applicators, all the most significant and recent advancements in the use of microwaves as energy source in both solid-state as well as solution combustion synthesis processes will be comprehensively reviewed, highlighting the unique opportunities arising from the coupling of these two energy efficient techniques. Moreover the possible employment of less conventional frequencies as well as the use of new-generation solid state generators will be critically discussed also in the framework of scaling-up and microwave reactor design considerations.
2017
- Microwave processing of high entropy alloys: A powder metallurgy approach
[Articolo su rivista]
Veronesi, Paolo; Colombini, Elena; Rosa, Roberto; Leonelli, Cristina; Garuti, Marco
abstract
Microwaves at the ISM frequency of 2450 and 5800 MHz have been exploited to prepare FeCoNiCrAl-family high entropy alloys by direct heating of pressed mixtures of metal powders. The aim of this work is to explore a new microwave assisted near-net-shape technology, using powder metallurgy approach for the preparation of high entropy alloys, able to overcome the limits of current melting technologies (defects formation) or solid state ones (time demanding). Results show that direct microwave heating of the powder precursors occurs, and further heating generation is favored by the ignition of exothermal reactions in the compound. Microwave processing, exploited both for the ignition and sustaining of such reactions, has been compared to reactive sintering in laboratory furnace and mechanical alloying in a planetary ball milling. Results demonstrate that microwave required the shortest time and lowest energy consumption, thus it is promising time- and cost-saving synthetic route.
2017
- Microwave processing of high entropy alloys: A powder metallurgy approach
[Relazione in Atti di Convegno]
Veronesi, P.; Rosa, R.; Colombini, E.; Leonelli, C.; Garuti, M.
abstract
Microwaves at the ISM frequency of 2450 and 5800 MHz have been exploited to prepare FeCoNiCrAl-family high entropy alloys by direct heating of pressed mixtures of metal powders. The aim of this work is to explore a new microwave assisted near-net-shape technology, using powder metallurgy approach for the preparation of high entropy alloys, able to overcome the limits of current melting technologies (defects formation) or solid state ones (time demanding). Results show that direct microwave heating of the powder precursors occurs, and further heating generation is favored by the ignition of exothermal reactions in the compound. Microwave processing, exploited both for the ignition and sustaining of such reactions, has been compared to reactive sintering in laboratory furnace and mechanical alloying in a planetary ball milling. Results demonstrate that microwave required the shortest time and lowest energy consumption, thus it is promising time- and cost-saving synthetic route.
2017
- New ceramic materials from MSWI bottom ash obtained by an innovative microwave-assisted sintering process
[Articolo su rivista]
Taurino, Rosa; Karamanov, Alexander; Rosa, Roberto; Karamanova, E.; Barbieri, Luisa; Atanasova Vladimirova, S.; Avdeev, G.; Leonelli, Cristina
abstract
Preliminary results on the production of new ceramic bricks by an innovative microwave-assisted sintering process employing MSWI bottom ashes are reported. Microwave heating technique was compared with a conventional thermal treatment with the aims to: (1) study the influence of heat treatment method on the crystallization behavior and on the microstructure of obtained samples; (2) define the crystallization evolution in microwave field; (3) gain an insight into the physical properties of the new samples. Higher crystallinity and new crystal phases were observed in the samples prepared by microwave heating, where precipitation of new sodium rich crystal phases was observed, together with quartz and anorthite, formed in the conventionally prepared samples. The possibility to obtain novel bricks with huge waste amount, in a very short thermal cycle and at relatively low temperatures was demonstrated with significant reductions in the energy demand for their production. Finally, the samples obtained by microwave-assisted sintering are characterized by improved mechanical properties.
2017
- Process Intensification by Experimental Design Application to Microwave-Assisted Extraction of Phenolic Compounds from Juglans regia L.
[Articolo su rivista]
Rosa, Roberto; Tassi, Lorenzo; Orteca, Giulia; Saladini, Monica; Villa, Carla; Veronesi, Paolo; Leonelli, Cristina; Ferrari, Erika
abstract
Microwave-assisted extraction was applied to Juglans regia L. fresh male flowers and unripe walnut seeds to evaluate the total phenolic contents of the extracts as well as the percentage of water-soluble polyphenols. The research was planned using the Design of Experiments technique to investigate the role on the extraction efficiency of different parameters, such as temperature, time and number of microwave heating cycles, together with their possible interactions. Optimization was achieved by applying a Response Surface Methodology comprising a three-factor, two-level, full-factorial Face-Centred Central Composite Design. The two input variables with a significant effect on the recovery of phenols from fresh male flowers were the extraction temperature and the number of microwave cycles. In the case of unripe walnut seeds, a linear two-factor interaction model was selected, with significant interactions occurring between temperature and time, and time and number of microwave cycles. The best experimental conditions were as follows: 100 °C, 6 min, three microwave heating cycles and 22.7 ± 0.2 mg gallic acid equivalent (GAE)/g (total phenolic content, PC); energy consumption calculations suggested slightly different conditions: 60 °C, 30 min, three microwave heating cycles and 20.7 ± 0.3 mg GAE/g (TPC).
2016
- Cradle to the grave Life Cycle Assessment of microwave assisted vs. conventional extraction for the obtainment of highly pure curcumin
[Abstract in Atti di Convegno]
Rosa, Roberto; Zerazion, Elisabetta; Ferrari, Erika; Veronesi, Paolo; Leonelli, Cristina; Saladini, Monica; Ferrari, Anna Maria
abstract
Microwave assisted extraction of natural compounds is widely recognized as one of the most promising green extraction techniques, even if comprehensive comparisons with more conventional procedures are surprisingly scarce, being on the other hand limited to mere considerations concerning extraction time and yield.
In this work, “cradle to the grave” environmental assessments of microwave assisted compared to conventional Soxhlet-based extraction procedures will be presented, for the particular case of curcumin molecule, extracted from Curcuma longa L., in view of its important antioxidant, anti-inflammatory and anticancer properties. The Life Cycle Assessment (LCA) methodology was applied, since it allows evaluating the environmental consequences associated with all the stages of the extraction process, thus including the crop production of the Indian plant, the subsequent production of the dried rhizomes, their commercialization, their transport, all the energy consumptions needed, the necessary laboratory facilities and their maintenance, together with the chemicals needed and their disposal treatments. The study was then completed by also comparing the obtained results with those of a particular synthetic strategy of curcumin, in order to establish the most environmentally friendly production procedure of this fundamental phytochemical.
2016
- Environmental assessment of different synthetic strategies towards engineered oxide nanomaterials
[Abstract in Atti di Convegno]
Rosa, Roberto; Pini, Martina; Neri, Paolo; Ferrari, Anna Maria
abstract
In the evaluation and selection of a particular synthetic strategy for the preparation of desired engineered nanomaterials, careful considerations on the size and the shape of nanocrystals must accompany the conventional considerations related to the yield, reaction time and cost of the precursors. Moreover, in order for inorganic chemistry to pursue a sustainable development, green metrics assessments are becoming always more popular. Among the different soft chemistry strategies available for the synthesis of engineered nanomaterials, some of the most intriguing and effectively employed ones have been compared in this work, in terms of their environmental as well as human health assessments. Particularly sol-gel synthesis (both hydrolytic and non-hydrolytic) and solution combustion synthesis are the three synthetic strategies selected for this comparative study. Anatase TiO2 nanoparticles have been identified as the ideal material, since it is probably the most studied and applied semiconductor and photocatalyst, owing to its unique physicochemical properties. First approximated environmental evaluation from the mere chemical point of view has been performed with the software EATOS (Environmental Assessment Tool for Organic Syntheses). Subsequently complete cradle to the grave analyses have been conducted by the Life Cycle Assessment (LCA) methodology, allowing considering further fundamentals damage categories. This study represents a pioneering work for the establishment of environmental and human health impacts rankings, comprising all the possible synthetic approaches to a desired nanomaterial. Preliminary results and future perspectives related to the scaling-up of selected syntheses as well as the possibility of employing alternative heating techniques will be presented as well.
2016
- Microwave assisted synthesis of Si-modified Mn25FexNi25Cu(50−x) high entropy alloys
[Articolo su rivista]
Veronesi, Paolo; Colombini, Elena; Rosa, Roberto; Leonelli, Cristina; Rosi, Fabrizio
abstract
Rapid microwave heating at 2450 MHz of metallic powders mixtures compacts was performed under Ar flux in a single mode applicator in order to produce Si-modified Mn25FexNi25Cu(50−x), (x=25, 30, 35, 40) high entropy alloys. Microwave heating was conducted in presence of a SiC auxiliary absorber, so that the compacts are subjected to both direct heating by microwave absorption and indirect heating by the auxiliary absorber. Due to the extremely rapid processing times, including the cooling stage, depletion of the most oxygen-reactive elements was moderate, considering the not perfectly protective atmosphere used. FCC solid solutions have been obtained and the role of Si is discussed as a microstructure modifier and as increaser of the microhardness.
2016
- Microwave ignition of the combustion synthesis of aluminides and field-related effects
[Articolo su rivista]
Rosa, Roberto; Veronesi, Paolo; Casagrande, Angelo; Leonelli, Cristina
abstract
Combustion synthesis of aluminide intermetallics starting from reactive powders mixtures comprising a ferromagnetic component (Fe, Co and Ni) has been performed by igniting the exothermic reactions in a microwave single mode applicator, in order to investigate possible effects related to the positioning of the reactive sample into the region of predominant electric or magnetic field. In addition to an increase of the reproducibility of the experiments and the possibility to avoid electric arcs generation, the ignition of the combustion reactions in predominant magnetic field allowed to significantly reduce the ignition times, with a global reduction of the power required to synthesize the intermetallics. This implies that the amount of the reactive volume under ignition conditions is reduced proportionally, thus moving from thermal explosion towards Self-propagating High-temperature Synthesis mode of combustion. Moreover, in the case of Fe-Al system, the disposition of the load into the region of predominant magnetic field increased the yield of the desired intermetallic compound, to the detriment of α-Fe(Al) solid solution co-product. Furthermore, the possibility to continue to furnish energy to the reactive Fe + Al sample after combustion synthesis ignition has been proven for both configurations. Results show that in case of exposure to the predominant magnetic field, the sample cooling rate resulted lower, hence the permanence at high temperatures after synthesis could be proficiently exploited to increase adhesion to an underlying substrate, in case combustion synthesis technique is used to obtain intermetallic-based coatings.
2016
- Microwave-assisted extraction of phytochemicals
[Abstract in Atti di Convegno]
Rosa, Roberto; Zerazion, Elisabetta; Ferrari, Erika; Veronesi, Paolo; Villa, Carla; Saladini, Monica; Ferrari, Anna Maria; Leonelli, Cristina
abstract
Several epidemiological studies highlighted the importance of a diet based on fruits and vegetables, for a significant reduction in the risk of several human health diseases [1]. Therefore, the extraction of the so-called dietary phytochemicals started gaining an extraordinary research interest from both academia and industries, to the detriment of their synthesis, particularly when the concepts and principles of Green Extraction [2] and Process Intensification [3] are considered, in order to pursue a sustainable development.
Among the green extraction techniques, the application of microwave energy is surely to be considered one of the most appealing ones, mainly as a direct consequence of its unique heating mechanism. According to the nature of the plant matrix as well as of the phytochemical compounds of interest, microwaves can be applied in a plenty of variants.
Aim of the present work is to display some of our recent results obtained by microwave assisted extraction (MAE) of phenolic compounds from Juglans regia L., Cinnamomum Zeylanicum and Curcuma longa L. [4], highlighting the advantages, when any, over more conventional extraction procedures as well as over the chemical synthesis of those molecules, also in terms of energy consumptions as well as environmental assessments of these different approaches.
2016
- Phytochemical compounds or their synthetic counterparts? A detailed comparison of the quantitative environmental assessment for the synthesis and extraction of curcumin
[Articolo su rivista]
Zerazion, Elisabetta; Rosa, Roberto; Ferrari, Erika; Veronesi, Paolo; Leonelli, Cristina; Saladini, Monica; Ferrari, Anna Maria
abstract
Natural compounds represent an extremely wide category to be exploited, in order to develop new pharmaceutical strategies. In this framework, the number of in vitro, in vivo and clinical trials investigating the therapeutic potential of curcumin is exponentially increasing, due to its antioxidant, anti-inflammatory and anticancer properties. The possibility to obtain this molecule by both chemical synthesis and extraction from natural sources makes the environmental assessments of these alternative production processes of paramount importance from a green chemistry perspective, with the aim, for both industries and academia, to pursue a more sustainable development. The present work reports detailed and quantitative environmental assessments of three different curcumin production strategies: synthesis, conventional Soxhlet-based extraction (CE) and microwave-assisted extraction (MAE). The chemical synthesis of curcumin, as recently optimized by the authors, has been firstly evaluated by using the EATOS software followed by a complete “cradle to the grave” study, realized by applying the Life Cycle Assessment (LCA) methodology. The life cycles of CE and MAE were then similarly assessed, considering also the cultivation of Curcuma longa L., the production of the dried rhizomes as well as their commercialization, in order to firstly investigate the widely claimed green character of MAE with respect to more conventional extraction procedures. Secondly, the results related to the two different extraction strategies were compared to those obtained by the chemical synthesis of curcumin, with the aim to determine its greenest preparation procedure among those investigated. This work represents the first example of an environmental assessment comparison between different production strategies of curcumin, thus smoothing the way towards the highly desirable establishment of environmentally friendly rankings, comprising all the existing alternatives to the chemical synthesis of a target chemical compound.
2016
- Sintesi assistita da microonde per ottenere leghe ad alta entropia a diverso tenore di alluminio
[Articolo su rivista]
Colombini, Elena; Rosa, Roberto; Trombi, Lorenzo; Veronesi, Paolo
abstract
In questo studio si è analizzato l’effetto della variazione del contenuto di alluminio nella sintesi e microstruttura della lega ad
alta entropia di composizione: FeCoNiCrAlx, dove x può assumere i valori x=1,1.5,2,3. Il ruolo atteso dell’alluminio durane la
sintesi è di creare una fase liquida che acceleri le reazioni, che altrimenti avverrebbero unicamente allo stato solido, mentre
i rimanenti elementi comprendono almeno un elemento ferromagnetico per migliorare l’assorbimento delle microonde durante
la sintesi. Dalle caratterizzazioni effettuate si evince che all’aumentare del contenuto di alluminio si ottengono leghe
composizionalmente più omogenee, una promozione della struttura cristallina CCC e l’aumento della durezza media. La lega
equimolare FeCoNiCrAl è stata poi confrontata con la lega FeCoNiCuAl. Dalla diffrazione è possibile vedere la tendenza della
lega di sposarsi verso una struttura cristallina CFC, grazie alla presenza di rame.
2016
- Valutazione ambientale comparativa di alcune strategie sintetiche di nanoparticelle di TiO2
[Abstract in Atti di Convegno]
Rosa, Roberto; Pini, Martina; Neri, Paolo; Corradi, Anna; Leonelli, Cristina; Ferrari, Anna Maria
abstract
Il convegno si svolge presso le sale di Palazzo Garzolini di Toppo Wassermann, sede della Scuola Superiore dell’Università di Udine, che racchiude tre secoli di storia, arte, cultura e un futuro dedicato ai giovani e alla conoscenza. Tale evento nasce come occasione per favorire il confronto e lo scambio di esperienze tra i partecipanti sia per quanto attiene i recenti risultati della attività di ricerca scientifica che per questioni inerenti la specifica didattica orientata alle Tecnologie Chimiche per l’Ingegneria.I lavori del convegno, i cui atti saranno pubblicati esclusivamente in formato elettronico,
sono articolati in forma di conferenze plenarie, comunicazioni orali e conferenze da parte di giovani ricercatori a cui vengono conferiti i premi AICIng per le migliori Tesi di Dottorato. In particolare, tali premi hanno lo scopo di dare riconoscimento ai risultati di giovani talenti e stimolarli verso una carriera nella ricerca più innovativa. Non mancherà una articolata sessione poster che, assieme ai vari eventi sociali, consentirà la più ampia interazione tra i partecipanti.
Il tema della Tavola Rotonda di quest’anno sarà “Ricerca di base, ricerca applicata e trasferimento tecnologico” sul quale interverranno il Magnifico Rettore dell’Ateneo di Udine, prof. Alberto De Toni, il prof. Marco Gilli, Magnifico Rettore del Politecnico di Torino, la prof. Silvia Licoccia, collega AICIng e delegata alla Ricerca dell’Università di Roma Tor Vergata, e il dott. Emilio Sassone Corsi, AD di Management Innovation, Roma.
2015
- Analisi comparativa LCA dell’estrazione diretta convenzionale ed innovativa di Curcumina
[Abstract in Atti di Convegno]
Zerazion, Elisabetta; Rosa, Roberto; Ferrari, Erika; Neri, Paolo; Ferrari, Anna Maria
abstract
In order to develop new pharmaceutical strategies, natural compounds represent an extremely wide category to exploit. In this landscape, the number of in vitro, in vivo and clinical trials investigating the therapeutic potential of curcumin is exponentially increasing, due to its antioxidant, anti-inflammatory and anti-cancer properties. The possibility to obtain this phytochemical both by chemical synthesis and by extraction from natural sources, makes the environmental assessments of these alternative productions of paramount importance in a green chemistry perspective to pursue an always more sustainable development for industrial and academic research. The present work reports detailed and quantitative environmental assessments of three different curcumin production strategies: synthesis, Soxhlet-based extraction and microwave-assisted extraction.
The chemical synthesis of curcumin, as recently optimized by the authors, has been firstly evaluated by using the EATOS software followed by a complete “cradle to the grave” study, realized by applying the Life Cycle Assessment (LCA) methodology, to account for fundamental impact categories, different from the mere quantification of the loads associated to the chemicals employed. Two different extraction strategies were completely assessed and quantified by similar studies, considering also the cultivation of Curcuma longa L., the production of the dried rhizomes as well as their commercialization. Particularly a conventional Soxhlet-based extraction and a microwave-assisted extraction (MAE) procedure were considered, in order to firstly confirm the widely claimed green character of MAE with respect to more conventional extraction procedures. The results related to the two different extraction strategies were finally compared to those obtained in the chemical synthesis of curcumin. Moreover, in order to account for the therapeutic characteristics of curcumin, particularly its well known curative effect on cancer cachexia, a new indicator has been developed and implemented in the present LCA investigation.
This work represents the first example of a comparison of productions strategies based on environmental assessments, thus smoothing the way towards a highly desirable establishment of environmentally friendly rankings, comprising all the existing alternatives to the chemical synthesis of a target chemical compound.
2015
- Dielectric and magnetic measurements of iron-based materials and their variations at high temperature
[Relazione in Atti di Convegno]
Catala Civera, Josã; Veronesi, Paolo; Rosa, Roberto; Toso, Omar; De Appollonia, Marco; Llorens, Gabriel; Leonelli, Cristina
abstract
ND
2015
- Ecosustainable Development of Novel Bio-inorganic Hybrid Materials as UV Protection Systems for Potential Cosmetic Applications
[Articolo su rivista]
Villa, Carla; Lacapra, Chiara; Rosa, Roberto; Veronesi, Paolo; Leonelli, Cristina
abstract
A new organoclay, bio-inorganic hybrid material, was successfully prepared following the "green chemistry" principles, exploiting microwave irradiation (as an alternative energetic source) in both the solvent-free synthesis of the organic filler (UVB filter) and in its hydrothermal intercalation in a sodium Bentonite clay (renewable natural inorganic source at low temperature). The organic filler is a benzylidene camphor derivative with the same cationic moiety as the well- known UV filter camphor benzalkonium methosulfate. The aim of the research was the ecosustainable development of a new UV protection model, suitable for use in cosmetic and pharmaceutical products, with potential advantages of stability, efficiency and safety compared to the commercially available UVB sunscreens. The organically modified clay was thoroughly investigated using X-ray diffraction (XRD), infrared spectroscopy (IR), thermo gravimetric analysis and differential thermal analysis (DTA). Results confirmed the complete intercalation of the organic filler in the interlayer region of the smectite clay, leading to a new bio-inorganic hybrid material with potential for cosmetic and pharmaceutical applications in the UV protection field, as confirmed by preliminary photochemical studies. This work represents the first example in the use of Na-Bentonite cationic clay (usually employed as rheological additive) as hosting agent of the synthesized quaternary UVB filter, as well as in the complete MW-assisted preparation of the organoclay, starting from the synthesis of the organic UV sunscreen to its hydrothermal intercalation.
2015
- Environmental assessment of a bottom-up hydrolytic synthesis of TiO2 nanoparticles
[Articolo su rivista]
Pini, Martina; Rosa, Roberto; Neri, Paolo; Bondioli, Federica; Ferrari, Anna Maria
abstract
A green metrics evaluation of the bottom-up hydrolytic sol–gel synthesis of titanium dioxide (TiO2) nanoparticles has been performed by following two different approaches, namely, EATOS software and LCA methodology. Indeed, the importance of engineered nanomaterials is increasing worldwide in many high-technological applications. Due to the as yet completely un-established environment and human health impact of nano-sized materials, the possibility of at least choosing a greener synthetic strategy through an accurate comparison of detailed environmental assessments will soon be of absolute importance in both the small and large scale production of these advanced inorganic materials. The present LCA study has been carried out following an ecodesign approach, in order to limit the environmental impacts and protect human health. The results of LCA analysis suggest that the highest environmental impact is mainly due to energy and the titanium isopropoxide precursor used in the synthesis process. Concurrently, software EATOS has been employed to calculate the environmental parameters that account for the environmental and social costs related to all the chemicals involved in the analyzed synthesis. As the EATOS approach is based purely on synthetic chemical mechanism considerations, thus neglecting any energy contributions, and its results cannot be directly compared to those arising from LCA analysis. However, similar and comparable outcomes are obtained by simply neglecting the energy contributions, broadening the application fields of the combined EATOS-LCA approach to the inorganic synthesis of engineered nanomaterials, highlighting the great potential of their synergy.
2015
- Environmental assessment of different processing methods for the synthesis of TiO2 nanoparticles
[Abstract in Atti di Convegno]
Rosa, Roberto; Pini, Martina; Neri, Paolo; Zerazion, Elisabetta; Ferrari, Anna Maria
abstract
Engineered nanomaterials are increasingly gaining a worldwide relevance in a plenty of high-technological
applications. Due to the yet completely un-established environment and human health impact of nanomaterials,
the possibility to choose the greener synthetic route through accurate comparison of their environmental impact
quantitative assessment, will soon become of absolute importance in both small as well as large-scale production
of these advanced inorganic materials. In this last perspective, among the key issues related to minimisation of
the impact of nanotechnology on the environmental and on the human health, life cycle assessment and green
chemistry metrics in general have been reported as mandatory. In this work green metrics assessment of different
synthesis of titanium dioxide (TiO2) nanoparticles have been performed by following two different approaches,
namely by using EATOS software [1] and by Life Cycle Assessment (LCA) methodology [2]. The choice of TiO2 is
due to the fact that it is the most studied and applied semiconductor and photocatalyst, as a consequence of its
unique physicochemical properties [3]. Particularly nanosized anatase is the most attractive crystalline form of
TiO2 for advanced and high-technological applications mainly because of its higher stability and photocatalytic
activity with respect to rutile and brookite. Consequently, the obtainment of anatase nanoparticles with high purity
and precisely controlled structure and particle size is the main purpose of optimized synthetic methods. Several
methods have been developed over the last decade to achieve this scope; in particular, this work will consider the
most widely diffused synthetic strategy according to the scientific literature, such as hydrolytic sol-gel [4],
hydrothermal [5] and solution combustion [6] synthesis processes. Moreover, the use of alternative or at least less
conventional heating techniques will be considered as well. In details, the here performed LCA studies followed
an ecodesign approach, in order to limit the environmental impacts and to protect the human health. The analysis
of the results were performed by using the SimaPro 8.0.2 software and IMPACT 2002+ method, which has been
modified introducing a preliminary attempt to assess the TiO2 nanoparticles toxicity released in water on both
freshwater ecosystem and humans. As concern the software EATOS, it has been employed to calculate the
environmental parameters, which account for the environmental costs related to all the chemicals involved in the
analyzed syntheses. This free of charge software allows utilization of easily available data for the calculation of
green metrics indexes. The results of the environmental comparison performed among the analyzed syntheses of
TiO2 nanoparticles highlighted the great potentialities of EATOS-LCA combination also in the inorganic chemistry
field, allowing defining the greener option available to inorganic chemists and materials scientists
2015
- Microwave-Assisted Preparation of High Entropy Alloys
[Articolo su rivista]
Veronesi, Paolo; Rosa, Roberto; Colombini, Elena; Leonelli, Cristina; Veronesi, Paolo
abstract
Microwaves at the ISM (Industrial, Scientific and Medical, reserved internationally) frequency of 2450 or 5800 MHz have been used to prepare FeCoNiCuAl, FeCrNiTiAl and FeCoCrNiAl2.5 high entropy alloys by direct heating of pressed mixtures of metal powders. The aim of this work is to explore a new microwave-assisted near-net-shape technology, using a powder metallurgy approach for the preparation of high entropy alloys, able to overcome the limits of current melting technologies (defects formation) or solid state ones (time demanding). High entropy alloy compositions have been selected so as to comprise at least one ferromagnetic element and one highly reactive couple, like Ni-Al, Ti-Al, Co-Al or Fe-Al. Results show that direct microwave heating of the powder precursors occurs, and further heating generation is favored by the ignition of exothermal reactions in the load. Microwaves have been applied both for the ignition and sustaining of such reactions, showing that by the proposed technique, it is possible to control the cooling rate of the newly-synthesized high entropy alloys. Results showed also that microwave heating in predominant magnetic field regions of the microwave applicator is more effective at controlling the cooling rate. The herein proposed microwave-assisted powder metallurgy approach is suitable to retain the shape of the load imparted during forming by uniaxial pressing. The homogeneity of the prepared high entropy alloys in all cases was good, without the dendritic segregation typical of arc melting, even if some partially-unreacted powders were detected in the samples.
2015
- Microwave-assisted preparation of sodium-silicate solutions from perlite
[Articolo su rivista]
Bagramyan, V. V; Sarkisyan, A. A.; Ponzoni, Chiara; Rosa, Roberto; Leonelli, Cristina
abstract
Systematic studies on the preparation of sodium-silicate solutions of different compositions via the hydrothermal-microwave treatment of perlite with an NaOH solution were performed. The effect of various factors on the degree of SiO2 recovery and the reaction rate was studied. The application of microwave energy was established to intensify the process of hydrothermal treatment compared to conventional heating.
2015
- Quantitative environmental assessment of solution combustion synthesis of oxide nanomaterials
[Abstract in Atti di Convegno]
Rosa, Roberto; Pini, Martina; Ferrari, Anna Maria
abstract
Among soft chemistry strategies for the preparation of advanced functional oxide nanomaterials, solution combustion synthesis (SCS) can be easily considered the most appealing one. Indeed, with respect, for example, to sol-gel (both hydrolytic and non-hydrolytic) and hydrothermal (or solvothermal) techniques, SCS is significantly less energy and time consuming, the reason of which mainly relies in its self-sustaining character [1, 2]. However, although SCS advantages have been widely recognized and accepted worldwide, contributing to make this synthetic route well fitting in the green inorganic chemistry field [3, 4], quantitative data related to its environmental as well as human health impact is missing in the scientific literature.
Therefore, starting from a previous work from our group [5], in which the green metrics evaluation of a hydrolytic sol-gel synthesis of TiO2 nanoparticles was accurately investigated, a similar approach was applied in the present work to quantitatively assess the impact of SCS of similar oxide material.
Particularly SCS of anatase nanoparticles consists in the following three reaction steps [6]: hydrolysis (eq. 1), nitration (eq. 2) and CS employing glycine as fuel (eq. 3).
Ti(C4H9O)4 + 3H2O → TiO(OH)2 + 4C4H9OH (eq. 1)
TiO(OH)2 + 2HNO3 → TiO(NO3)2 + 2H2O (eq. 2)
3TiO(NO3)2 + 5C2H5NO2 → 3TiO2 + 8N2 + 5CO2 + 10 H2O (eq. 3)
A first evaluation, from a mere chemical point of view, was realized by means of the software EATOS (Environmental Assessment Tool for Organic Syntheses [7]). This software allows calculating some important environmental parameters, by considering data, which are easily available from the material safety data sheets.
Moreover, in order to take into consideration other potentially impacting categories such as transportation, energy and time requirements, thus realizing a cradle to the grave environmental evaluation, the Life Cycle Assessment (LCA, [8]) of the SCS of anatase TiO2 nanoparticles has been realized.
The obtained results will allow for the first time to quantitatively determine the widely recognized “greenness” of SCS technique, and, concurrently, to compare this synthetic strategy to those more conventionally employed. The quantitative environmental parameters obtained by the combined EATOS-LCA methodology, will be extremely useful to inorganic chemists and material scientists with a strong environmental awareness.
The potential applicability, of the here proposed quantitative environmental assessment to further combustion synthesis-based processes and products will be discussed as well.
2015
- Recycling of aluminum and titanium chips by microwave augmented SHS
[Relazione in Atti di Convegno]
Veronesi, Paolo; Rosa, Roberto; Colombini, Elena; Lancellotti, Isabella; Giovanardi, Roberto; Leonelli, Cristina; Montecchia, L.; Cavatorta, G.
abstract
Recycling of titanium and aluminium chips to manufacture wear and corrosion-resistant intermetallic-based coatings is achieved by microwave assisted Self Propagating High Temperature Synthesis (SHS). A multi-physics model implementing both reaction kinetic and microwave heating and heat transfer has been developed in order to optimize the synthesis condition. Numerical simulation allowed to investigate the preferable applicator geometry and to quantify the excess heat generated, which could be useful to promote further reactions with an iron-based substrate, thus realizing intermetallic-coated steel-based products.
2015
- Solution combustion synthesis of La1-xSrxFe1-yCuyO3±w (x=0, 0.2; Y=0, 0.2) perovskite nanoparticles: Conventional vs. microwaves ignition
[Articolo su rivista]
Rosa, Roberto; Ponzoni, Chiara; Veronesi, Paolo; Natali Sora, Isabella; Felice, Valeria; Leonelli, Cristina
abstract
La1-xSrxFe1-yCuyO3±w (x=0, 0.2; y=0, 0.2) nanoparticles have been prepared by solution combustion synthesis exploiting both conventional and microwave heating in the ignition of the self-sustaining reactions. Interaction of microwaves with the reaction mixture allowed significant reduction of the ignition time according to the dielectric properties of the precursor gels, which have been measured at room temperature in the 0.5-3 GHz frequency range. Both the ignition strategies led to the preparation of crystalline single-phase products without affecting particles morphology. The ignition technique influenced only the average particles size with those prepared by microwaves-ignition, possessing typically larger dimension, as a probable consequence of the higher temperatures reached due to microwave absorbing products. Perfectly crystallised nanoparticles were obtained after combustion syntheses and calcination at 600 °C for 3 h in the particle size range between 20 and 80 nm dependently upon the heating source and the dopant level.
2015
- Stabilization of bismuth ferrite suspensions in aqueous medium with sodium polyacrylate characterized by different molecular weights
[Articolo su rivista]
Ponzoni, Chiara; Cannio, Maria; Rosa, Roberto; Leonelli, Cristina
abstract
Electrostatic stabilization of bismuth ferrite BiFeO3 (BFO) single phase micronized particles suspended for the first time in aqueous medium, using sodium polyacrylate (Na-PAA) as suspending agent, was investigated to form homogeneous films through electrophoretic deposition technique. The dispersion efficiency was evaluated in terms of the zeta potential trend as a function of pH and sediment percentage, employing a fast and easy spectrophotometric method. All the tests were performed using three suspending agents characterized by the same polyacrylate functional group (-COONa) but with different molecular weights (Na-PAA Mw = 2100, 5100, and 20 000). The effect of BFO particles concentration (wt%), suspending agent concentration (wt%), suspending agent molecular weight and sonication time have been evaluated. The results showed that for all the experiments carried out the electrostatic stabilization of the BFO micronized particles in aqueous medium is accomplished in high basic pH range (8.5-9 or 9-11) depending on the molecular weight of the polyacrylate additive.
2014
- Direct energy supply to the reaction mixture during microwave-assisted hydrothermal and combustion synthesis of inorganic materials
[Articolo su rivista]
Rosa, R.; Ponzoni, C.; Leonelli, C.
abstract
The use of microwaves to perform inorganic synthesis allows the direct transfer of electromagnetic energy inside the reaction mixture, independently of the temperature manifested therein. The conversion of microwave (MW) radiation into heat is useful in overcoming the activation energy barriers associated with chemical transformations, but the use of microwaves can be further extended to higher temperatures, thus creating unusual high-energy environments. In devising synthetic methodologies to engineered nanomaterials, hydrothermal synthesis and solution combustion synthesis can be used as reference systems to illustrate effects related to microwave irradiation. In the first case, energy is transferred to the entire reaction volume, causing a homogeneous temperature rise within a closed vessel in a few minutes, hence assuring uniform crystal growth at the nanometer scale. In the second case, strong exothermic combustion syntheses can benefit from the application of microwaves to convey energy to the reaction not only during the ignition step, but also while it is occurring and even after its completion. In both approaches, however, the direct interaction of microwaves with the reaction mixture can lead to practically gradient-less heating profiles, on the basis of which the main observed characteristics and properties of the aforementioned reactions and products can be explained.
2014
- Dispersing hydrophilic nanoparticles in hydrophobic polymers: HDPE/ZnO nanocomposites by a novel template-based approach
[Articolo su rivista]
de Luna, M. Salzano; Galizia, M.; Wojnarowicz, J.; Rosa, Roberto; Lojkowski, W.; Leonelli, Cristina; Acierno, D.; Filippone, G.
abstract
The efficiency of a novel template-based approach for the dispersion of hydrophilic nanoparticles within hydrophobic polymer matrices is investigated. The procedure envisages the permeation of a well dispersed nanoparticle suspension inside a micro-porous matrix, obtained through selective extraction of a sacrificial phase from a finely interpenetrated co-continuous polymer blend. Specifically, a blend of high density polyethylene (HDPE) and polyethylene oxide (PEO) at 50/50 wt% is prepared by melt mixing. The addition of small amounts of organo-clay promotes the necessary refinement of the blend morphology. Once removed the PEO, the micro-porous HDPE matrix is dipped in a colloidal suspension of zinc oxide nanoparticles which exhibits low interfacial tension with HDPE. A system prepared by traditional melt mixing is used as reference. Melt- and solid-state viscoelastic measurements reveal a good quality of the filler dispersion despite the uneven distribution on micro-scale. The latter can be capitalized to minimize the filler content to attain a certain improvement of the material properties or to design nano-structured polymer composites. © BME-PT.
2014
- Mechanical and dynamic-mechanical behavior and morphology of polystyrene/perovskite composites: Effects of filler size
[Articolo su rivista]
Russo, Pietro; Acierno, Domenico; Rosa, Roberto; Leonelli, Cristina; Corradi, Anna; Rizzuti, Antonino
abstract
Composites based on a commercial grade polystyrene (PS) resin containing non commercial perovskite particles were prepared by melt mixing and analyzed in terms of mechanical properties, dynamic-mechanical behavior and morphology. In particular, with the aim to study the influence of the filler size on the ultimate properties of PS based composites micro- and nano-sized perovskite La0.5Sr0.5MnO3 crystal particles, synthesized by using an efficient and rapid microwave-assisted hydrothermal route, were considered.Measurements of flexural parameters such as modulus and strength by static tests and storage modulus and damping factor by dynamic-mechanical evaluations showed better performance for nanofilled systems with respect to the ones containing micro particles, with the same filler content.Mechanical evidences were explained also by morphological observations from which a different level of filler dispersion seems to be obtained with the organization of perovskite nanosized crystals in superstructures able to support viscoelastic results. © 2012 Elsevier B.V.
2014
- Microwave-assisted nonaqueous sol-gel synthesis of highly crystalline magnetite nanocrystals
[Articolo su rivista]
Sciancalepore, C.; Rosa, R.; Barrera, G.; Tiberto, P.; Allia, P.; Bondioli, F.
abstract
Microwave-assisted benzyl alcohol route, starting form Fe(III) acetylacetonate, was applied to obtain crystalline magnetite nanoparticles. In particular the effect of synthesis time on the physical and magnetic properties of the so obtained powders were evaluated. By means of this approach, monocrystalline magnetite particles with size ranging from 4 to 8 nm were obtained. The crystallinity increases as the microwave thermal treatment is increased and reaches almost 95 wt% with treatment time of 240 min. The size of the units individually responding to a magnetic field is slightly larger than the nanoparticle size, indicating partial aggregation of nanoparticles. Both the magnetization of powders and the effects of magnetic dipolar interaction increase with increasing heating time. All powders behave as weakly interacting superparamagnetic materials over an extended temperature interval.
2014
- Valutazione ambientale della sintesi della curcumina tramite parametri quantitativi di green metrics
[Abstract in Atti di Convegno]
Zerazion, Elisabetta; Rosa, Roberto; Ferrari, Erika; Leonelli, Cristina; Corradi, Anna; Ferrari, Anna Maria
abstract
La curcumina [(1E,6E)-1,7-Bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione] è un composto fenolico presente nei rizomi della pianta Curcuma longa L. Essa, così come numerosi suoi derivati, possiede interessanti proprietà antiossidanti, antiinfiammatorie e antitumorali [1]. Per questo motivo la sintesi chimica dei diversi curcuminoidi risulta fondamentale allo scopo di realizzare un accurato studio di tutte le possibili relazioni esistenti tra struttura e proprietà.
Lo scopo di questo lavoro è quello di presentare una dettagliata valutazione ambientale del processo sintetico della curcumina così come messo a punto da alcuni degli autori [2]. Infatti, ultimamente accanto ai tradizionali parametri che accompagnano una sintesi chimica (come resa, tempo di reazione, etc.) sta acquisendo sempre maggiore importanza l’utilizzo dei cosiddetti parametri di green metrics, allo scopo di promuovere uno sviluppo sempre più sostenibile, permettendo al chimico organico di scegliere la strategia sintetica meno impattante sull’ambiente e sulla salute umana [3,4].
L’approccio seguito ha previsto l’utilizzo del software EATOS (Environmental Assessment Tool for Organic Synthesis [5,6]) e di uno studio tramite metodologia LCA (Life Cycle Assessment) [7]. Al contrario del software EATOS (che è limitato alla sola valutazione delle sostanze chimiche coinvolte nella sintesi e nel work-up) l’analisi LCA permette di prendere in considerazione numerose altre categorie potenzialmente impattanti quali i consumi energetici, quelli dovuti al trasporto delle materie prime, agli imballaggi delle sostanze utilizzate, e molti altri, permettendo di realizzare una valutazione dell’intero ciclo di vita del processo “dalla culla alla tomba”. I risultati ottenuti permetteranno anche un successivo paragone con il processo estrattivo, così come con le sintesi e le estrazioni che prevedano l’utilizzo di tecniche non convenzionali, come ad esempio il riscaldamento dielettrico a microonde.
2014
- Valutazione ambientale della sintesi sol-gel idrolitica di nano particelle di TiO2 tramite un approccio sinergico con software EATOS e metodologia LCA
[Abstract in Atti di Convegno]
Pini, Martina; Neri, Paolo; Rosa, Roberto; Zerazion, Elisabetta; Ferrari, Anna Maria
abstract
La sintesi di nano materiali di dimensione e forma desiderata costituisce attualmente una delle principali aree di ricerca della chimica inorganica e della scienza dei materiali. Nonostante numerosissime strategie sintetiche siano sviluppate continuamente allo scopo di raggiungere un controllo sempre maggiore dei nano cristalli ottenuti, la loro valutazione ambientale tramite parametri quantitativi (le cosiddette Green Metrics), raramente accompagna le classiche valutazioni di resa, tempo di reazione e costo. Tutto ciò risulta particolarmente sorprendente considerando che gli effetti dei nano materiali sulla salute umana e sull’ambiente non sono ancora stati completamente stabiliti e/o chiarificati. Pertanto, la possibilità di optare per una determinata via sintetica rispetto ad un'altra, sulla base non solo della dimensione e della forma delle particelle desiderate, ma anche sul più basso impatto ambientale e sulla salute umana dell’intero processo, dovrebbe sicuramente costituire un aspetto fondamentale nella produzione di nano materiali opportunamente ingegnerizzati allo scopo di perseguire uno sviluppo sempre più sostenibile [1].
Il presente lavoro si propone di fornire una valutazione ambientale dettagliata della sintesi per via sol-gel idrolitica di nano particelle di anatasio (TiO2) [2] tramite la combinazione di due metodi: l’utilizzo del software EATOS (Environmental Assessment Tool for Organic Synthesis, [3, 4]) ed uno studio completo “dalla culla alla tomba” tramite metodologia LCA (Life Cycle Assessment).
Nonostante queste due tecniche siano state già applicate in maniera sinergica e comparativa nella valutazione di alcune sintesi organiche [5, 6], questo studio rappresenta il primo esempio di applicazione alla sintesi inorganica di nano materiali.
Trascurando i contributi energetici, le due metodologie utilizzate forniscono risultati assolutamente comparabili, evidenziando come il software EATOS possa essere utilizzato per una prima valutazione comparativa tra diverse vie sintetiche, ma anche per una valutazione quantitativa di una nuova sintesi messa a punto. Nonostante EATOS fornisca indicazioni assolutamente affidabili, anche nel caso di sintesi inorganiche, questo strumento deve successivamente essere integrato da una valutazione dell’intero ciclo di vita di quel determinato processo, per poter considerare anche l’impatto di altre categorie fondamentali quali ad esempio il consumo energetico, il trasporto, la distribuzione, l’utilizzo ed il destino finale di quel determinato materiale.
2013
- A review on combustion synthesis intensification by means of microwave energy
[Articolo su rivista]
Rosa, Roberto; Veronesi, Paolo; Leonelli, Cristina
abstract
Combustion synthesis (CS) is a materials manufacturing technique, which gained increased attention by both academia and industries, due to its intrinsic energy saving characteristics and high purity of the products. Energy requirements for CS are limited to the ignition step, since the desired products are obtained by using the heat generated by exothermic reactions occurring between the reactants.CS has been here addressed from a process intensification perspective, since CS characteristics perfectly fit into several process intensification definitions, aims and approaches.Particular attention has been dedicated to the use of microwaves as energy source for CS, and the benefits deriving from the combination of these two techniques have been reviewed. The doubtless better energy transfer efficiency of microwaves, with respect to conventional heating techniques, arising from the direct interaction of the electromagnetic energy with the reactants, contributes to further intensify both solid state and solution CS processes.Moreover, microwaves peculiarities, such as their selective and volumetric nature, together with their energy transfer nature, open new attractive opportunities for CS in different fields of materials science, like joining and advanced protective coatings. Innovative strategies of microwaves-ignited and/or sustained CS for the process intensification of advanced materials manufacturing are proposed as well.
2013
- Design and optimization of a multi-port applicator for microwave assisted foaming
[Relazione in Atti di Convegno]
Veronesi, Paolo; Rosa, Roberto; Garuti, Marco; Botti, Claudio; Balocchi, Paolo
abstract
The use of numerical simulation to design a microwave applicator dedicated to foaming is presented. During foaming, the load characteristics change, both in terms of permittivity, thermal properties and size and shape. The use of a growth law able to describe size and characteristics variations of the load as microwave heating proceeds allowed to determine the most suitable microwave source arrangement able to provide both good energy efficiency and heat generation homogeneity. Load shape variations are neglected, assuming that expansion occurs with shape retention. Despite its simplified nature, the model allows to compare different scenarios of microwave applicator geometry, showing the advantages of the multi-physics approach adopted. The designed applicator was built and tested, showing the feasibility at the industrial scale of rapid microwave foaming of starch based products of complex shape.
2013
- Effect of low-temperature high-pressure sintering on BiFeO3 density, electrical magnetic and structural properties
[Articolo su rivista]
Ponzoni, C.; Cannio, M.; Rosa, R.; Chudoba, T.; Pietrzykowka, E.; Buscaglia, V.; Finocchio, E.; Nanni, P.; Lojkowski, W.; Leonelli, C.
abstract
Single-phase multiferroic BiFeO3 (BFO) powders were prepared by hydrothermal microwave synthesis and dense BiFeO3 ceramics were fabricated for the first time by the low-temperature high-pressure (LTHP) sintering technique. Effect of sintering temperature ranging from 400 to 800 °C (3 min and 10 min) and pressure of 3-8 GPa on structural, microstructural, electric and magnetic properties were investigated through X-ray diffraction, scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS), density and magnetic measurements. The results highlighted that LTHP sintering method, thanks to the high pressure involved, requires lower temperature and shorter time than other techniques, avoiding BiFeO3 phase degradation. SEM images show that for short experimental time (t = 3 min) the average grain size of the sintered samples was approximately the same size of raw powder. Extending the sintering time up to 10 min the grain growth phenomena occurred. Moreover the results indicate that the best obtained density value was around 98% of theoretical density. The dielectric behavior of BiFeO3 ceramics was not significantly influenced by the LTHP sintering conditions. Magnetic measurements showed that ceramic BiFeO 3 is weakly ferromagnetic at room temperature. © 2013 Taylor & Francis.
2013
- Electrophoretic deposition of multiferroic BiFeO3 sub-micrometric particles from stabilized suspensions
[Articolo su rivista]
Ponzoni, Chiara; Rosa, Roberto; Cannio, Maria; Buscaglia, Vincenzo; Finocchio, Elisabetta; Nanni, Paolo; Leonelli, Cristina
abstract
The electrophoretic deposition (EPD) was applied to BiFeO3 (BFO) powders, one of the most interesting multiferroic compounds characterized by simultaneous magnetic and ferroelectric activity, to form homogeneous films. The preparation and characterization of stable BFO colloidal suspensions in aqueous, organic and mixed solvents were investigated by zeta potential measurements at room temperature in the presence of surfactants. BFO thin films were then deposited on steel substrates from stabilized BFO suspensions, by adjusting the preparative parameters to optimize the film quality. The compositional, morphological and electrical characteristics of the obtained BFO films, together with thickness measurements, were studied using SEM, XRD, AFM, EIS and optical surface profilometer. EPD method applied to BFO stable suspensions produced homogeneous thickness BFO films, free from pinholes and cracks, that were successively sintered and characterized also in terms of photocatalytic response.
2013
- Field-related effects in the microwave ignited synthesis of aluminides
[Relazione in Atti di Convegno]
Veronesi, Paolo; Rosa, Roberto; Leonelli, Cristina
abstract
Microwave ignited combustion synthesis can be used to achieve complete conversion of reactants and to obtain products with unique microstructures. However, this synthetic route suffers from usually poor reproducibility due to the possible electromagnetic field distribution-related ignition mechanisms. Ignition can occur by the direct heating of the reactants, or by their indirect heating by the use of microwave co-absorbers or due to the possible occurrence of breakdown phenomena. In this work, the effects of microwave ignition in regions of predominant electric or magnetic field is investigated in case of mixtures of powdered metal reactants, one of which is aluminium and the remaining is of ferromagnetic nature. These reactions, when a high heating rate is applied, are usually preceded by the formation of liquid aluminium, which then reacts with the other elements to form the intermetallics. The aim of the work is to improve the process reproducibility and to propose new strategies to optimise the synthesis of high purity aluminide intermetallics. Significant differences between ignition in predominant E or H field were experimentally observed, suggesting that the electromagnetic field-related effects could be proficiently exploited to control the kinetic and the microstructure of the final products.
2013
- Microwave assisted combustion synthesis in the system Ti-Si-C for the joining of SiC: Experimental and numerical simulation results
[Articolo su rivista]
Rosa, Roberto; Veronesi, Paolo; S., Han; V., Casalegno; M., Salvo; Colombini, Elena; Leonelli, Cristina; M., Ferraris
abstract
Microwaves at 2.45GHz have been applied to ignite the combustion synthesis of compacted Ti-Si-C powders mixtures, having 1:1:1 atomic ratio, in order to join SiC-based components. A mixture of different refractory phases such as TiC and TiSi2 were obtained. Depending on the synthesis conditions, no residual silicon in the joint was detected, suggesting the suitability of the here proposed experimental joining approach for nuclear plants and high temperature applications. A simplified model was developed with the aim of obtaining a deeper understanding of the here proposed rapid, almost pressure-less and localized heating joining method. Experimental and numerical simulation results demonstrate that joining of SiC can be rapidly obtained with minimization of heat affected zones in the SiC substrates. Maximum apparent shear strength values of the joints ranged from 9.9 to 45.1MPa, depending on the process conditions.
2013
- Microwave selective thermal development of latent fingerprints on porous surfaces: Potentialities of the method and preliminary experimental results
[Articolo su rivista]
Rosa, Roberto; Veronesi, Paolo; Leonelli, Cristina
abstract
The thermal development of latent fingerprints on paper surfaces is a simple, safe, and chemicals-free method, based on the faster heating of the substrate underlying the print residue. Microwave heating is proposed for the first time for the development of latent fingerprints on cellulose-based substrate, in order to add to the thermal development mechanism the further characteristic of being able to heat the fingerprint residues to a different extent with respect to the substrate, due to the intrinsic difference in their dielectric properties. Numerical simulation was performed to confirm and highlight the selectivity of microwaves, and preliminary experimental results point out the great potentialities of this technique, which allowed developing both latent sebaceous-rich and latent eccrine-rich fingerprints on different porous surfaces, in less than 30 sec time with an applied output power of 500 W. Microwaves demonstrated more effectiveness in the development of eccrine-rich residues, aged up to 12 weeks
2013
- Microwave-assisted melt reaction method for the intercalation of carboxylic acid anions into layered double hydroxides
[Articolo su rivista]
Rosa, R.; Leonelli, C.; Villa, C.; Priarone, G.
abstract
Carboxylic acid anions intercalated layered double hydroxides are currently gaining increasing interest due to their potential applications in pharmaceutical field for controlled drug release in novel tunable drug delivery systems. In this work different aliphatic carboxylic acid anions were intercalated into the interlayers of commercial as well as synthetically prepared layered double hydroxides, through a novel microwave mediated melt reaction approach. The volumetric nature of microwave dielectric heating was exploited in order to rapidly heat the intimate mixture of the lamellar inorganic precursor and the appropriate organic acid, at the melting temperature of the particular monoor dicarboxylic acid used, reaching the intercalation in approximately two hours treatment.
2013
- Optimization of BFO microwave-hydrothermal synthesis: Influence of process parameters
[Articolo su rivista]
Ponzoni, Chiara; Rosa, Roberto; Cannio, Maria; Buscaglia, Vincenzo; Finocchio, Elisabetta; Nanni, Paolo; Leonelli, Cristina
abstract
Multiferroic materials exhibiting ferromagnetic and ferroelectric properties in a certain temperature range are acquiring interest in information storage and sensors applications. Facile microwave hydrothermal synthesis route was optimized for the preparation of BiFeO3 (BFO) pure-phase. Influence of process parameters (i.e. precursor ratio, mineralizer concentration, temperature, time) on phase formation, particle size distribution and morphology was investigated in detail. The BFO powders were characterized by XRD, ESEM and TEM. Single phase BFO was formed using KOH, 8 M at 200 °C, 30 min and KOH, 10 M at 180 °C, 30 min; the presence of Na 2CO3, acting as electron donor, allowed the reaction to be performed at lower KOH concentrations and temperatures, 6 and 8 M at 180 °C in 30 min. Particles' morphology evolution with concentration and temperature without Na2CO3 followed the sequence: spherical, lamellar, lamellar semi-cubic, cubic; while with Na2CO3 addition the evolution was: lamellar semi-cubic, cubic and prismatic truncated octahedron shape. © 2012 Elsevier B.V. All rights reserved.
2013
- Single step combustion synthesis of β-NiAl-coated γ-TiAl by microwave ignition and subsequent annealing
[Articolo su rivista]
Rosa, Roberto; Veronesi, Paolo; Leonelli, Cristina; Poli, Giorgio; A., Casagrande
abstract
β-NiAl-coated γ-TiAl-based alloys were synthesised following a single combustion synthesis step in a mono mode microwave applicator operating at 2.45. GHz under a moderate pressure of 0.15. MPa, allowing the simultaneous synthesis and forming of the required shape. Two reactive cylindrical specimens composed respectively of substrate (Ti. +. Al, 50:50. at.%) and coating (Ni. +. Al, 50:50. at.%) powder mixtures were positioned in the region of maximum electric field strength of the microwave applicator. The high exothermicity of the reactions involved, together with the application of pressure, allowed synthesising in a self-propagating regime the new intermetallic phases and to promote a good adhesion between them, due to the formation of complex reaction interface belonging to the Ni-Al-Ti system. A subsequent isothermal annealing treatment at 1230. °C led to the obtainment of the desired homogeneous γ-TiAl structure into the substrate without affecting the single β-NiAl phase constituting the coating. The anomalous presence of annealing twins was observed and explained considering the different states in which combustion synthesis of aluminides in the Ni. +. Al, Ti. +. Al and Ni. +. Al. +. Ti systems occurs
2013
- Solution Combustion Synthesis of perovskite oxides: Comparison between MWs and conventional ignition
[Abstract in Atti di Convegno]
Rosa, R.; Ponzoni, C.; Veronesi, P.; Natali Sora, I.; Felice, V.; Leonelli, C.
abstract
Solution Combustion Synthesis is a nanomaterials preparation technique which is significantly energy- and time-efficient, being the energy required limited to the ignition step and being the reaction time greatly reduced as a consequence of the explosive nature of the exothermic process. Aim of this work is to present a detailed comparison between conventionally-ignited and microwavesignited solution combustion synthesis of LaFeO3 nanopowders, being this oxide at the basis of La1-xSrxFe1-yCuyO3-w perovskite materials, which represent a promising class of oxides to be exploited as the cathode in solid oxide fuel cells (SOFCs). The effects of the different ignition conditions on synthesis parameters and on nanoparticles size and morphology have been investigated in detail.
2012
- Combination of electrophoretic deposition and microwave-ignited combustion synthesis for the preparation of ceramic coated intermetallic-based materials
[Articolo su rivista]
Rosa, Roberto; Veronesi, Paolo; Michelazzi, Marco; Leonelli, Cristina; A. R., Boccaccini
abstract
Electrophoretic deposition (EPD) was used to deposit sub-micrometric ZrO2 particles on metallic powder compacts belonging to the systems Ni + Al and Ti + Al, which were used as deposition electrodes in the EPD cell. After EPD, combustion synthesis (CS) of such reactive electrodes was ignited in a microwave single-mode applicator, operating at a frequency of 2.45 GHz, in order to obtain in a single step the synthesis of the desired intermetallic phase (substrate) and the sintering of the previously deposited ceramic particles (or coating). Experimental results demonstrate that the excess heat released during the formation of nickel and titanium aluminides by CS can be exploited not only to self-sustain and self-propagate the reaction front along the substrate, but also to rapidly sinter the coating obtained by EPD. The innovative procedure here proposed is a promising strategy in order to obtain, in a single step, high temperature intermetallic-based materials, protected by well adhered ceramic coatings.
2012
- Functionally graded WC-Co/Ni-Al HVOF coatings for damage tolerance, wear and corrosion protection
[Articolo su rivista]
Bolelli, Giovanni; Cannillo, Valeria; Lusvarghi, Luca; Rosa, Roberto; A., Valarezo; W. B., Choi; R., Dey; C., Weyant; S., Sampath
abstract
The manufacturing of a HVOF-sprayed functionally graded coating (FGC), consisting of two NiAl/WC–Co composite layers with increasing cermet content and a pure WC–Co topmost layer, is discussed in this paper. As the stress build-up during spraying, measured via curvature method, is reduced in the NiAl-rich layers, thick coatings can be deposited with lower risk of delamination, in comparison to a pure WC–Co thick layer. Thermal stresses within the layers and the stainless steel substrate, measured from low temper- ature thermal cycling tests, are also reduced. The mechanical behaviour of the top layer in the graded struc- ture at relatively low loads (i.e. pin-on-disk) is equivalent to the same layer without gradation, whereas at high loads (i.e. ball-drop impact test) the enhanced compliance with depth increases the load bearing capa- bility of the graded structure. Electrochemical corrosion tests demonstrate no significant interconnected porosity and therefore, no interaction of the graded layers with the topmost WC–Co layer. The deterioration of the deeper layers under wear and corrosive conditions are also tested to investigate their performance in the scenario that the top layer coating wears out exposing the deeper layers to the surface.
2012
- Microwave ignited combustion synthesis as a joining technique for dissimilar materials
[Articolo su rivista]
Rosa, Roberto; Colombini, Elena; Veronesi, Paolo; Poli, Giorgio; Leonelli, Cristina
abstract
Microwave energy has been exploited to ignite combustion synthesis (CS) reactions of properly designed powders mixtures, in order to rapidly reach the joining between different kinds of materials, including metals (Titanium and Inconel) and ceramics (SiC). Beside the great advantage offered by CS itself, i.e., rapid and highly localized heat generation, the microwaves selectivity in being absorbed by micrometric metallic powders and not by bulk metallic components represents a further intriguing aspect in advanced materials joining applications, namely the possibility to avoid the exposition to high temperatures of the entire substrates to be joined. Moreover, in case of microwaves absorbing substrates, the competitive microwaves absorption by both substrates and powdered joining material, leads to the possibility of adhesion, interdiffusion and chemical bonding enhancements. In this study, both experimental and numerical simulation results are used to highlight the great potentialities of microwave ignited CS in the joining of advanced materials.
2012
- Microwave ignited combustion synthesis as a joining technique for dissimilar materials: Modeling and experimental results
[Articolo su rivista]
Colombini, Elena; Rosa, Roberto; Veronesi, Paolo; M., Cavallini; Poli, Giorgio; Leonelli, Cristina
abstract
Microwave energy has been applied to ignite the combustion synthesis (CS) in Ni + Al (50: 50 at %) powder mixtures in order to join dissimilar materials, in particular high-temperature metals. A numerical simulation was performed in order to obtain the data otherwise difficult to be experimentally measured and to develop a simplified predictive model of microwave ignited and sustained CS in metal powder compacts for joining applications. Experimental and numerical simulation results demonstrate that joining can be rapidly obtained by microwave ignition of the combustion synthesis characterized by a minimum extension of heat affected zones in the joined substrates.
2012
- Ni-Al-Ti coatings obtained by microwave assisted combustion synthesis
[Articolo su rivista]
Rosa, Roberto; Veronesi, Paolo; Poli, Giorgio; Leonelli, Cristina; Corradi, Anna; A., Casagrande; I., Boromei
abstract
Microwaves at 2·45 GHz have been used to ignite the self-propagating high temperature synthesis of Ni and Al powder mixtures (50:50 at-%) to produce a duplex intermetallic coating on Ti substrates. Owing to the high β-NiAl synthesis reaction enthalpy and the energy provided by the electromagnetic field, the newly formed aluminide is in the liquid phase. Thus, it can react with the underlying Ti substrate, forming a ternary eutectic at the interface, belonging to the Ni‐Al‐Ti system. The peculiar interlocking microstructure of such ternary layer is responsible for an increase in toughness and hardness compared to the parent NiAl coating. Moreover, the ternary layer’s oxidation resistance was tested, showing the possibility of replacing the functionality of hard and brittle NiAl, but limitedly up to 750°C. This can be ascribed to the relatively low Al content in the ternary layer, which hinders the formation of a continuous and protective Al2O3 scale. For this reason, the increase in Al content, or the addition of further elements such as Cr or Si, in the starting powder mixture, helps improve the oxidation resistance of the complex intermetallic coating at the interface, up to the tested temperature of 900°C.
2012
- Rapid microwave sintering of protective ZrO2 coatings on reactive metal powder compacts
[Relazione in Atti di Convegno]
Veronesi, Paolo; Rosa, Roberto; Colombini, Elena
abstract
Electrophoretic deposition was used to create protective coatings of sub-micrometric ZrO2 particles on substrates made of conductive powders mixture (Ni+Al). In order to achieve the required mechanical properties, such coating requires a sintering stage. However, the rapid microwave sintering of thin zirconia layers usually requires some form of pre-heating or auxiliary heating of the material, in order to increase its loss factor. In this study, the heat released by the exothermal reactions of combustion synthesis occurring in the powders compact, is used to concurrently synthesize high-temperature rated aluminides and pre-heat and sinter the overlaying zirconia coating. Finite elements numerical simulation, fully coupling electromagnetic, heat transfer and chemical reactions application modes is used to investigate the temperature profile and power density distribution during the microwave sintering process, Experimental results show that the concurrent synthesis allows to form a thin alumina-based bond coat, which is expected to increase the high temperature resistance of the zirconia-coated aluminides.
2012
- Ultrafine magnetite nanopowder: Synthesis, characterization, and preliminary use as filler of polymethylmethacrylate nanocomposites
[Articolo su rivista]
Russo, P.; Acierno, D.; Palomba, M.; Carotenuto, G.; Rosa, R.; Rizzuti, A.; Leonelli, C.
abstract
Magnetite (Fe 3O 4) nanoparticles prepared by microwave-assisted hydrothermal synthesis have been characterized in terms of morphological and structural features. Electron micrographs collected in both scanning (SEM) and transmission (TEM) modes and evaluations of X-ray powder diffraction (XRD) patterns have indicated the achievement of a monodispersed crystallite structure with particles having an average size around 1520 nm. Structural investigations by Micro-Raman spectroscopy highlighted the obtainment of magnetite nanocrystals with a partial surface oxidation to maghemite (γ-Fe 3O 4). Preliminary attention has been also paid to the use of these magnetite nanoparticles as filler for a commercial polymethylmethacrylate resin. Hybrid formulations containing up to 3 wt of nanoparticles were prepared by melt blending and characterized by calorimetric and thermogravimetric tests. For sake of comparison, same formulations containing commercial Fe 3O 4 nanoparticles are also reported. Calorimetric characterization indicates an increase of both glass transition temperature and thermal stability of the nanocomposite systems when loaded with the synthesized magnetite nanoparticles rather then loaded with the same amount of commercial Fe 3O 4. This first observation represents just one aspect of the promising potentiality offered by the novel magnetic nanoparticles when mixed with PMMA. © 2012 Pietro Russo et al.
2011
- Continuous microwave plasma processing of cold drawn steel wire rod
[Relazione in Atti di Convegno]
Veronesi, Paolo; Rosa, Roberto; Leonelli, Cristina; Cavatorta, Giovanni
abstract
Surface modification of cold drawn steel wire rod has been performed using a set of microwave plasma torches operating at 2.45 GHz, 3 kW maximum power, with the aim to modify the wire surface morphology and chemical composition prior to hot dip coating with Znbased alloys. The effect of varying the carrier gas type and flux is investigated experimentally and by numerical simulation. Adhesion of the zinc-based coating after plasma treatment, compared to untreated samples, as well as corrosion resistance, resulted improved, however treatment reproducibility can be still considered poor.
2011
- Energy transfer in microwave assisted Combustion Synthesis of inorganic compounds
[Relazione in Atti di Convegno]
Rosa, Roberto; Veronesi, Paolo; Leonelli, Cristina; Corradi, Anna Bonamartini
abstract
In this work microwaves (MWs) were used to ignite and sustain, the Combustion Synthesis (CS) of micrometric metallic powders in order to obtain thick intermetallic coatings as well as joining between advanced materials. MW heating possess the peculiarity to transfer energy, and not heat directly, to the reactive powders, thus it becomes possible to continue to provide energy to the reactive specimen during and after the CS, thus controlling the heating and the cooling behaviour at the reaction front. Investigations concerning the separate effect of positioning the sample in predominant electric field or magnetic field will be presented as well.
2011
- Functionally graded materials obtained by combustion synthesis techniques: A review
[Capitolo/Saggio]
Rosa, Roberto; Veronesi, Paolo
abstract
Among the large number of different techniques to produce Functionally Graded Materials (FGMs), Combustion Synthesis (CS) is gaining an increasing interest due to the possibility of achieving high-purity products in short processing times (typically of the order of few seconds or less), and with low energy consumption (limited to the ignition step), as well as low cost of the manufacturing equipment required. CS exploits high exothermic reactions between reactants, which, after reaching the ignition temperature, start to form the desired products and the reaction becomes self-sustaining, not requiring any other external energy contribution. Depending on the way of ignition, combustion synthesis can be conducted in the Self-propagating High-temperature Synthesis (SHS) mode or in the Thermal Explosion (TE) mode. In the SHS mode, the reaction is ignited at one end of the reactive sample and it self-propagates in the form of a combustion wave at very high velocities. In the TE mode (also known as reactive sintering or volume combustion synthesis) the whole volume of the sample is heated uniformly in a controlled manner until reaction takes place essentially simultaneously throughout the volume. The use of CS in FGMs manufacturing can benefit from the fast kinetics involved, allowing to create non equilibrium structures or to lead to products less prone to homogenization, thus preserving the gradient structure imparted during the forming step. Among the wide variety of possible ignition techniques, which will be discussed in the present review, recent results obtained by microwave (MW) irradiation will be presented, discussing the advantages of such a heating technique in FGMs manufacturing. MWs, in fact, can enhance the previously mentioned advantages due to their peculiarities of rapid, volumetric and selective heating, the latter particularly relevant when dealing with multi-phase systems. © 2012 by Nova Science Publishers, Inc. All rights reserved.
2011
- Microwave ignited Combustion synthesis of intermetallic compounds, modelling and experimental results
[Articolo su rivista]
Colombini, Elena; Rosa, Roberto; Veronesi, Paolo; Casagrande, A.
abstract
The process of Combustion synthesis (CS) is based on the highly exothermic reaction by reactants, which, if properly ignited, spontaneously turn into products. The aim of this work is to study the CS of β-NiAl formed starting from Ni and Al (1:1 at. %) powders activated by microwaves at 2.45 GHz. Numerical simulation is used to obtain data otherwise difficult to be measured experimentally and to develop a predictive model of microwave ignited and sustained CS of metal powder compacts. The simulation couples an electro-thermal model with a chemical model, required to study the exothermic reaction between powders. A simplify model was obtained and validated, neglecting volume changes, to study compositional and temperature change and reaction kinetics during the CS. It allowed to demonstrate how microwave application, during and after, synthesis could control the cooling rate of products and hence the microstructure of the newly formed intermetallics.
2011
- Microwave ignited combustion synthesis of metal and intermetallic matrix composites
[Relazione in Atti di Convegno]
Rosa, Roberto; Sola, Ramona; Colombini, Elena; Veronesi, Paolo; Leonelli, Cristina
abstract
Aim of this work is to present the results concerning the application of microwave assisted combustion synthesis (MACS) approach in the production of different kind of cermets and intermetallic matrix composite (IMC). Combustion synthesis allows taking advantages from the heat generated from exothermic reactions, which can derive from the synthesis of the intermetallic matrix, of the reinforcement, or both. Microwaves were used to ignite such combustion reactions exploiting their heating selectivity. The use of a single mode applicator allowed also investigating any "specific" microwave effects ascribable to separate electric and magnetic fields.
2011
- Microwave-mediated preparation of bio-inorganic hybrid materials for cosmetic and pharmaceutical applications
[Relazione in Atti di Convegno]
Villa, C.; Priarone, G.; Rosa, R.; Leonelli, C.
abstract
Due to their peculiar structure, layered nanomaterials, such as layered double hydroxides (LDHs, anionic clays) represent an interesting pathway to develop new multitasking hybrid materials. For biological, pharmaceutical and cosmetic purposes, LDHs can act as both reservoirs as well as carriers for organic bioactive hosts. In this study we present the preparation of organo-LDH using several Microwave (MW) - mediated intercalation procedures. MW activation was used both for the preparation of LDHs and for their subsequent hydrothermal intercalation. All the reactions were carried out using scientific single mode microwave applicators. Operative conditions and comparative results with the conventional methods will be reported.
2011
- Microwaves assisted hydrothermal synthesis of sub-micrometric BiFeO 3 particles
[Relazione in Atti di Convegno]
Ponzoni, Chiara; Rosa, Roberto; Veronesi, Paolo; Leonelli, Cristina; Buscaglia, Maria Teresa; Buscaglia, Vincenzo; Finocchio, Elisabetta; Nanni, Paolo
abstract
Microwave assisted hydrothermal synthesis is widely recognized to enhance powders crystallinity leading to a narrower particle size distribution compared to conventional hydrothermal approach. The synthesis of complex oxide systems still remains a challenge due to the multiplicity of oxidation states, morphologies and phases. Multiferroic materials, since exhibit magnetic and ferroelectric order in the same temperature range, are gaining increasing interest in information storage and sensors applications. The preparation of the well-known multiferroic BiFeO3, following a microwave hydrothermal approach, has been investigated in this work. The optimization of the experimental conditions (salt precursors, mineralizer concentration, temperature, time, etc.), is presented and discussed in terms of particles size distribution, phase purity and product morphology.
2011
- Microwaves-mediated preparation of organoclays as organic-/bio-inorganic hybrid materials
[Articolo su rivista]
Villa, C.; Rosa, R.; Corradi, A.; Leonelli, C.
abstract
An innovative approach in the field of nanomaterials is to develop modern and mild synthetic protocols that enable controlled and integrated organization of specific functional organic and biological building blocks. In this context, research on the preparation of clay-based organic-inorganic hybrid materials, i.e. organoclays, has received considerable attention because these lamellar materials not only possess highly ordered structure in 2D, but also provide interesting chemical intercalation and surface properties. As a result entrapment and orientation of various functional guest molecules into layered inorganic solids, has been well exploited. At present there is a great deal of interest in the rational design of hybrid organic-/bio-inorganic composites on the nanometer to micrometer length scales. These hybrids encompass highly selective recognition properties associated with organic and biological species, combined with catalytic, optical, and electronic properties of the inorganic lamellar framework. This paper presents an overview of microwave application in different preparation steps of organophilic clays, their modification and their addition to polymeric matrices. Particular attention has been given to the microwave-mediated hydrothermal technique, as innovative and eco-friendly protocol for the intercalation of different kinds of organic hosts into the interlayer of clay minerals. The few pioneering complete microwave-mediated preparation procedures, exploiting advantages of dielectric heating in both the synthesis of the organic host molecule and the intercalation in the clay structure, have been also highlighted. © 2011 Bentham Science Publishers Ltd.
2011
- On the boron addition to beta-NiAl intermetallic obtained by microwaves ignited combustion synthesis
[Relazione in Atti di Convegno]
Veronesi, Paolo; Rosa, Roberto; Poli, Giorgio; Casagrande, Angelo
abstract
Aim of the present work is to accurately investigate the effect of Boron addition on the microstructure and mechanical properties of β-NiAl intermetallic phase obtained by microwave initiated and sustained combustion synthesis (CS). In this work the rapidness, selectivity and volumetric nature of microwaves (MWs) at the frequency of 2.45 GHz were exploited to ignite the combustion synthesis of precursor powder mixtures, leading to the preparation of free-standing β-NiAl intermetallic specimens presenting different boron amounts. Micro-alloying with B is known to contribute to improve the ductility and enhancing room temperature toughness of aluminides, while larger boron amounts significantly increase the yield strength and hardness. Since literature results are sometimes contradictory, particularly as far as the CS manufacturing process is concerned, an accurate investigation on the possible mechanisms which can be responsible for the above mentioned improvements, has been carried out, demonstrating that boron addition is effective in decreasing the intrinsic brittleness and improving the ductility of β-NiAl intermetallic phase, already starting form 50 ppm concentration.
2011
- Prismatic applicator for continuous microwave-assisted synthesis of metallic nanoparticles
[Relazione in Atti di Convegno]
Veronesi, Paolo; Rosa, Roberto; Leonelli, Cristina; Cappi, A.; Barzanti, A.; Baldi, G.
abstract
Metallic (Ag, Au, Cu) nanoparticles suspensions are gaining an increasing interest in medical applications. Among the existing synthetic routes available, microwave processing allows to better control particle size and to achieve high purity of the products. The large scale production of nanoparticles requires the development of industrially-viable processes, preferably conducted using a "green chemistry" approach, at ambient pressure and relatively low temperature. Based on a recently developed microwave-assisted process in aqueous solution, a new dedicated continuous-flow reactor, made of two twin prismatic applicators has been designed, optimized and tested. It can produce up to 1000 liters/day of metal nanoparticles colloidal suspension
2010
- Damage tolerant functionally graded WC-Co/Stainless Steel HVOF coatings
[Articolo su rivista]
A., Valarezo; Bolelli, Giovanni; W. B., Choi; S., Sampath; Cannillo, Valeria; Lusvarghi, Luca; Rosa, Roberto
abstract
In this paper, effective damage tolerance of a functionally graded coating (FGC) deposited by high velocity oxygen fuel (HVOF) spraying is observed. The thick FGC (≈1.2 mm) consists of 6 layers with a stepwise change in composition from 100 vol.% ductile AISI316 stainless steel (bottom layer) to 100 vol.% hard WC-12Co (top layer) deposited onto an AISI316 stainless steel substrate. Damage tolerance is observed via 1) an increase in compliance with depth, and 2) an increase in fracture resistance by containment, arrest and deflection of cracks. A smooth gradation in the composition and hardness through the coating thickness is found by scanning electron microscopy and depth-sensing microindentation, respectively. The in-situ curvature measurement technique reveals that during the deposition of the FGC, compressive stresses exist in the lower, metallic layers owing to peening effect of successive impact, and these gradually evolve to high tensile, in the top layers. Tensile stresses appear to be due to quenching alone; thermal stresses are low because of the gradation. All of this is beneficial for the deposition of a thick coating.The FGC structure shows the ability to reduce cracking with increased compliance in the top layer during static and dynamic normal contact loading, while retaining excellent sliding wear resistance (ball-on-disk tests). Results are discussed in comparison to the behavior and properties of coatings of similar individual compositions and thicknesses, as well as a thick monolithic WC-12Co sprayed coating. Further improvements in the processing are proposed to enhance the adhesion strength and avoid coating delamination under high load contact-fatigue conditions.
2010
- Effect of Si and Cr content on the high temperature oxidation resistance of aluminide coatings on Ti obtained by microwave assisted SHS of metallic powders mixture
[Relazione in Atti di Convegno]
Veronesi, Paolo; Rosa, Roberto; Poli, Giorgio; Casagrande, A.; Boromei, I.
abstract
High temperature oxidation protection of alpha-titanium alloys is a fundamental aspect to be improved when applying such materials in demanding environments like in the case of high-performance exhaust systems. Protective Ni-Aluminide coatings produced by microwave assisted self-propagating high-temperature synthesis (SHS) of Ni and Al powder mixtures on Ti substrates are a promising route towards the improvement of hightemperature wear and oxidation resistance. As a matter of fact, the newly formed Ti-Ni-Al ternary compound at the Ti- interface (15 wt% of Al), results protective like pure NiAl, but only up to 750 °C. At 900 °C the lack of protective enough oxides does not hinder the growth of non-protective TiO2. In this study, the improvement of the 900°C oxidation resistance of the Ti-Ni-Al layer by powder metallurgy route is investigated, adding Si or Cr to the protective intermetallic coating and using microwave assisted SHS to minimize the extension of heat affected zones generated in the substrate when applying the coating.
2010
- Microwave Assisted Combustion Synthesis of Non-equilibrium Intermetallic Compounds
[Articolo su rivista]
Veronesi, Paolo; Rosa, Roberto; Colombini, Elena; Leonelli, Cristina; Poli, Giorgio; Angelo, Casagrande
abstract
A simplified model of the microwave-assisted combustion synthesis of Ni and Al metal powders to form the NiAl intermetallic on titanium and steel substrates is presented. The simulation couples an electro-thermal model with a chemical model, accounting for local heat generation due to the highly exothermic nature of the reactions between the powders.Numerical results, validated by experimental values, show that the capability of microwaves to convey energy, and not heat, can be used to alter the temperature profiles during and after the combustion synthesis, leading to unique intermetallic microstructures. This phenomenon is ascribed to the extended existence of high temperature liquid intermetallic phases, which react with the metallic substrates at the interface. Moreover, microwave heating selectivity allows to maintain the bulk of the substrate metallic materials to a much lower temperature, compared to combustion synthesis in conventionally heated furnaces, thus reducing possible unwanted transformations like phase change or oxidation.
2010
- Microwave (MW)-assisted combustion synthesis of micrometric metallic powders for the preparation of intermetallic-based materials
[Relazione in Atti di Convegno]
Rosa, Roberto; Veronesi, Paolo; Leonelli, Cristina; Corradi, A. B.
abstract
Due to the interesting combination of lightweight and high refractoriness, Al-based intermetallic compounds are candidate materials for high temperature applications like turbochargers and exhaust valves. Microwaves (MW) at the frequency of 2.45 GHz were used to ignite the combustion synthesis of elemental micrometric powder mixtures belonging to Fe-Al, Co-Al and Ni-Al systems. The use of a single mode MW applicator allowed undertaking for the first time a comparative investigation concerning the effects of positioning the samples in predominant electric or magnetic field during synthesis. Moreover the effect of microwave irradiation exposure time, after ignition of the highly exothermic reactions, has been investigated as well.
2010
- Microwave technique applied to the hydrothermal synthesis and sintering of calcia stabilized zirconia nanoparticles
[Articolo su rivista]
Rizzuti, A.; Corradi, A.; Leonelli, C.; Rosa, R.; Pielaszek, R.; Lojkowski, W.
abstract
This study is focused on the synthesis of zirconia nanopowders stabilized by 6%mol calcia prepared under hydrothermal conditions using microwave technology. Sodium hydroxide-based hydrolysis of zirconyl chloride solution containing calcium nitrate followed by microwave irradiation at the temperature of 220 °C for 30 min was sufficient to obtain white powders of crystalline calcia stabilized zirconia. By means of X-ray diffraction and transmission electron microscopy, it was shown that tetragonal zirconia nanocrystallites with a size of ca 7 nm and diameter/standard deviation ratio of 0.10 were formed. The effects of the [Ca2+] and [NaOH] as well as temperature and time of microwave irradiation on the density and specific surface area were evaluated. Sintering test of the tetragonal nanopowders at 1,300 °C in air was performed in a monomode microwave applicator. The sample was sintered to the density of 95% and the grain size, analyzed by field emission scanning electron microscopy, was in the range from 90 to 170 nm. © 2009 Springer Science+Business Media B.V.
2010
- Ni-Al-Ti coatings obtained by microwave assisted SHS: Oxidation behaviour in the 750-900 °C range
[Articolo su rivista]
Boromei, I.; Casagrande, A.; Tarterini, F.; Poli, Giorgio; Veronesi, Paolo; Rosa, Roberto
abstract
Microwaves have been used to ignite the Self-propagating High-temperature Synthesis (SHS) of Ni and Al powder mixtures to produce a duplex intermetallic coating on Ti substrates. Due to the high exothermic nature of the reaction, the newly formed NiAl is in the liquid phase and can react with the underlying Ti to form a tough ternary intermediate layer, belonging to the Ti-Ni-Al system, in a one step process. Aim of this work is to assess the high-temperature performances of the Ti-Ni-Al layer, compared to NiAl coating and Ti. Experimental results demonstrate that the ternary layer presents oxidation resistance comparable to NiAl up to 750 °C. In this condition, the thick Ti-Ni-Al layer could replace the functionality of hard and brittle NiAl coatings. At 900 °C, instead, NiAl oxidation resistance results higher, and this can be ascribed to the relatively low Al content in the studied ternary compound, which hinders the formation of a continuous and protective scale
2010
- Optimization of microwave-assisted rapid debinding of CIM parts in multimode applications
[Relazione in Atti di Convegno]
Rosa, Roberto; Veronesi, Paolo; Leonelli, Cristina
abstract
Microwave (MW) heating selectivity was exploited in this work for the rapid thermal debinding of parts obtained by Ceramic Injection Moulding (CIM). Since the organic binder preferentially absorbs microwaves with respect to ceramic powders, heat can be efficiently transferred to the green parts, despite their low thermal conductivity which renders conventional heating techniques less effective. However, one of the major drawbacks of microwave-assisted processes is the lack of reproducibility of the results, and of non-adequate experimental conditions and procedures which can lead to misleading conclusions on the effective yield of the process. A rational approach to overcome this problem, consisting in numerical simulation coupled to Design of Experiments (DoE) technique was used. In this way it has been possible to optimize the MW-assisted thermal debinding of ring-shaped CIM parts in multi-mode applicators operating at 2.45 GHz, reducing processing times from the original 80-140 hours (depending on the shape and dimensions of the samples) by conventional heating to 6 hours by dielectric heating.
2009
- Complete, efficient and "green" microwave assisted preparation of organoclays: Synthesis of the organic fillers and their intercalation procedure
[Abstract in Atti di Convegno]
Villa, C.; Rosa, R.; Mariani, E.; Veronesi, P.; Leonelli, C.; Corradi, A.
abstract
Organoclays are organic-inorganic hybrid systems, which find a wide range of application in several industrial fields. In pursuing a Green Chemistry approach to synthetic routes coupling microwave (MW) activation to chemical processes, in this work we focused our research efforts on the MW assisted preparation of new organoclays interesting for peculiar cosmetic and pharmaceutical applications. MW heating was successfully applied to both the solventless synthetic protocol of the appropriate organic fillers (quaternary ammonium salts) and to their hydrothermal intercalation in a smectite clay structure. The organic compounds were obtained in excellent yield under mild conditions and their complete intercalation was fast achieved as confirmed by powder X-ray diffraction (XRD). Advantages of the microwave-mediated procedure over conventional preparative pathways in terms of "greenness" and the potential applications of the investigated systems are reported.
2009
- Microwave assisted combustion synthesis and compaction of intermetallic-based functionally graded materials: numerical simulation and experimental results
[Articolo su rivista]
Rosa, Roberto; Veronesi, Paolo; Leonelli, Cristina; Corradi, Anna
abstract
compaction of intermetallics-based functionally graded materials (FGMs) is presented. Numerical simulation was used to investigate the temperature distribution in the reacting powders, before, during and after combustion synthesis occurred, showing that microwaves are capable of continuing to convey energy to the reactants and products, despite an adverse temperature gradient. Examples of the application of Microwave Assisted Combustion Synthesis (MACS) are reported, involving principally neat intermetallic based FGMs, belonging to the system CoAl-NiAl, both as freestanding and coatings on titanium grade 5 alloy. Some other preliminary results on the reliability of the here proposed experimental approach to the synthesis of freestanding samples based on intermetallic-matrix ceramic particles reinforced FGMs, are presented
2009
- Microwave assisted synthesis of new β-diketo derivatives ligands
[Relazione in Atti di Convegno]
Ferrari, Erika; Lazzari, Sandra; Pignedoli, Francesca; Saladini, Monica; O., Verna; Corradi, Anna; Leonelli, Cristina; Rosa, Roberto; Veronesi, Paolo
abstract
The metal complexes of β-diketo derivatives and especially those of acetylacetone are well known and have been extensively studied. To improve the chelating ability of this molecule, we have introduced a further coordinative group. The designed compounds, which include a carboxylic group and the β-diketo moiety, are promising candidates as new metal ligands for pharmaceutical applications.
Classical synthetic strategy for the obtainment of these adducts requires a two step procedure consisting first in the SN2 reaction of methylenic group and second deprotection of ester derivatives in order to set the carboxylic function free.
Concerning the first step, traditional approach requires long reaction times and long work up procedures that lead to very poor product yields. Microwave (MW) irradiation at 2.45 GHz in closed vessels was exploited in this first synthetic step to take advantages from rapid heating rates thanks to the intrinsic volumetric and selectivity nature of MW heating.
Results in terms of reaction times and yields as well as possible future developments, will be discussed.
2009
- Microwave ignited combustion synthesis of intermetallic-based functionally graded materials
[Relazione in Atti di Convegno]
Rosa, Roberto; Veronesi, Paolo; Leonelli, Cristina; Corradi, A. B.
abstract
Combustion synthesis (CS) of different functionally graded materials (FGMs) based on intermetallic alloys were ignited by 2.45 GHz frequency microwaves, in order to obtain candidate materials for high temperature structural and coating applications. Combining CS with a moderate pressure, to promote porosity reduction, it was possible to obtain both freestanding samples and hard coatings on non-ferrous alloys substrates. The high temperature generated due to the high exothermicity of CS, and the selective microwave absorption by the reacting species, led to the formation of complex binary and ternary compounds and microstructures, at the interface between the reacted powders and the substrate, presenting, in some cases, an increased micro-hardness value with respect to parent materials.
2009
- Microwave-assisted consolidation of coatings obtained by electrophoretic deposition (EPD)
[Abstract in Atti di Convegno]
Veronesi, P.; Leonelli, C.; Corradi, A. B.; Poli, G.; Romagnoli, M.; Giovanardi, R.; Rosa, R.; Cannio, M.; Michelazzi, M.; Rizzuti, A.; Boccaccini, A. R.
abstract
Electrophoretic deposition (EPD) is an electrochemical method attracting increasing interest as a material processing technique. In the first step of EPD an electric field is applied between two electrodes and charged particles suspended in a suitable liquid move toward the oppositely charged electrode; in the second step the particles accumulate at the deposition electrode and create a relatively compact and homogeneous film, which, however, requires a further consolidation step in order to fully develop satisfactory mechanical properties. In the present work, EPD conditions have been varied in order to control the initial porosity of the deposits of nano- and sub-micrometric zirconia powders, applying an innovative "zerointegral" approach. Microwave heating was then applied to rapidly sinter the deposited powders, trying to minimize grain growth. EPD and microwave heating allow to influence the final product properties and thus its end use like thermal barrier coating or for tribological applications.
2009
- Modelling of microwave assisted combustion synthesis applied to the joining of high temperature ceramics
[Abstract in Atti di Convegno]
Rosa, R.; Veronesi, P.; Leonelli, C.; Corradi, A. B.; Salvo, M.; Casalegno, V.; Shaohua, H.; Ferraris, M.
abstract
Microwave (MW) irradiation at 2.45 GHz is a rapid and efficient way to ignite different kind of highly exothermic reactions involving powder mixtures, leading to the so-called combustion synthesis reactions. In the present work this technique was exploited to promote the rapid joining of high temperature ceramic materials composites, in a single mode applicator, applying a moderate pressure during the process. A multi-physics simplified model of the joining process between two SiC-based elements with the continuous application of microwaves was developed to study the effects on the combustion synthesis of powder mixtures preparation, microwave forward power and sample arrangement inside the applicator.
2009
- New Synthetic Glucosyl-Curcuminoids, and their 1Hand 13C NMR Characterization, from Curcuma longa L.
[Articolo su rivista]
Saladini, Monica; Lazzari, Sandra; Pignedoli, Francesca; Rosa, Roberto; F., Spagnolo; Ferrari, Erika
abstract
Turmeric extracts, among which curcumin and bisdemethoxycurcumin, are by far known for their therapeutic activities. In this study we propose easy and low cost synthetic pathways in order to obtain glucosyl-curcuminoids, safe and water soluble potential drugs and dyes, which may be implied in different fields ranging from pharmacology to food chemistry. The complete 1H and 13C NMR characterization of naturally occurring curcumin, bis-demethoxycurcumin and new synthetic glucosyl-curcuminoids is reported.
2009
- Oxidation behavior resistance of a duplex NiAl/Ti-Ni-Al coating by microwave assisted SHS on Ti substrate
[Abstract in Atti di Convegno]
Boromei, I.; Poli, G.; Veronesi, P.; Rosa, R.
abstract
Microwaves have been used to ignite the Self-propagating-High-temperature Synthesis (SHS) of Ni and Al powder mixtures to produce a duplex intermetallic coating on Ti substrates. Due to the high exothermic nature of the reaction, the newly formed NiAl is in the liquid phase and can react with the underlying Ti to form a tough ternary intermediate layer in a one step process. The obtained thick intermediate layer, Ti-Ni-Al ternary compound, with improved mechanical properties could replace the functionality of hard and brittle NiAl aluminide coatings in service. Moreover, the thickness of the intermediate layer, presenting an interlocking microstructure, can be controllably altered, up to 500μm, by annealing at 950°C for times ranging in the 3-20 minutes. The present work intends to assess the high temperature performances of the Ti-Ni-Al ternary coating, compared to pure Ti, Ti-6Al-4V and NiAl. In particular, cyclic oxidation response in the 750-900°C range and wear resistance at 750°C, measured using a ball-on-disk tribometer, were evaluated. The tendency for scale spallation, adherence and oxidation rates for NiAl and Ni-Al-Ti intermediate layer was evaluated as well.
2009
- “Oxidation Behavior Resistance of a Duplex NiAl/Ti-Ni-Al Coating by Microwave Assisted SHS on Ti Substrate”, Vol 3, , Denmark, 2009, 161-166, ISBN
[Relazione in Atti di Convegno]
I., Boromei; A., Casagrande; Poli, Giorgio; Veronesi, Paolo; Rosa, Roberto
abstract
-
2008
- “Tough and wear resistant Ni- Al based thick intermetallic coatings on titanium obtained by microwave assisted combustion synthesis”, , vol.3, Mannheim, Germany, 71-76, 2008, ISBN:
[Relazione in Atti di Convegno]
Veronesi, Paolo; Rosa, Roberto; Poli, Giorgio; A., Casagrande; G. P., Cammarota
abstract
-
2008
- Tough and wear resistant Ni-Al based thick intermetallic coatings on titanium Obtained by microwave assisted SHS
[Abstract in Atti di Convegno]
Veronesi, P.; Rosa, R.; Poli, G.; Casagrande, A.; Cammarota, G. P.
abstract
Microwaves at 2.45 GHz have been used to ignite the Self propagating High temperature Synthesis (SHS) of Ni and Al powder mixtures to produce NiAl and a complex Ni-Al-Ti intermediate layer on titanium. The use of microwaves allows to selectively convey energy to the reacting powders, even during and after SHS, thus prolonging the existence of liquid phases and promoting the formation of a well adhered interface between titanium and the newly formed NiAl. The intermediate layer, belonging to the Ni-Al-Ti system, presents an interlocking microstructure, which provides increased mechanical properties with respect to the parent polycrystalline NiAl. Wear resistance of the complex Ni-Al-Ti layer was measured in dry-sliding against alumina using a ball-on-disk tribometer. Micro-hardness, elastic modulus, and scratch resistance (constant load, single- and multi-pass) were also measured, showing that the Ni-Al-Ti layer presents increased performances with respect to polycrystalline NiAl obtained by microwave assisted SHS.
2007
- New "green" approaches to the synthesis of pyrazole derivatives
[Articolo su rivista]
Corradi, Anna; Leonelli, Cristina; Rizzuti, Antonino; Rosa, Roberto; Veronesi, Paolo; Grandi, Romano; S., Baldassari; C., Villa
abstract
A novel approach to the synthesis of pyrazole derivatives from tosylhydrazones of alpha,beta-unsaturated carbonyl compounds possessing a beta-hydrogen is proposed, exploiting microwave (MW) activation coupled with solvent free reaction conditions. The cycloaddition was studied on three ketones (trans-4-phenyl-3-buten-2-one, beta-ionone and trans-chalcone). The corresponding 3,5-disubstituted-1H-pyrazoles were obtained in high yields and after short reaction times. In order to simplify and point out the green chemistry features of the method, a further improvement was achieved under the same catalytic conditions with a "one pot" synthesis of these heterocyclic compounds, starting directly from their carbonyl precursors via tosylhydrazones generated in situ. For an exhaustive study, the dielectric properties of the solid reaction mixtures were also measured, in order to obtain input data for the numerical simulation of their heating behaviour in the single mode MW cavity which was used for experimental work. In order to supply a valid methodology and tool for measuring the environmental impact, a comparative study between the synthetic route proposed and the classical synthetic route has been carried out.
2005
- Simplification of several types of reactions with using of alternative energy forms
[Relazione in Atti di Convegno]
Nuchter, M.; Ondruschka, B.; Schneider, F.; Grandi, R.; Leonelli, C.; Rosa, R.
abstract