 |
CORRADO SCIANCALEPORE
DIPENDENTE ALTRA UNIVERSITA
Dipartimento di Ingegneria "Enzo Ferrari"
|
Home |
Pubblicazioni
2019
- Effect of powder recycling in laser-based powder bed fusion of Ti-6Al-4V
[Articolo su rivista]
Denti, L.; Sola, A.; Defanti, S.; Sciancalepore, C.; Bondioli, F.
abstract
Additive manufacturing (AM) has shown promise to process parts for end-use applications, however stringent requirements must be fulfilled in terms of reliability and predictability. The expensiveness of raw materials for AM, especially for metal-based Powder Bed Fusion (PBF), brings about the need for a careful recycling of powder, but the effect of powder reuse on both processing conditions and final part performance is still the focus of intensive research in the open literature. Although ASTM F2924-14 specifies the virgin-to-used powder ratio to be introduced to manufacture titanium-6aluminum-4vanadium (Ti-6Al-4V) components by PBF, a deeper understanding of the effect of powder recycling on the mechanical properties of finished parts is expected to foster a more efficient and safe reuse. The present contribution is therefore addressed to investigate the consequence of Ti- 6Al-4V powder recycling on the flowability, particle size distribution and morphology of the feedstock material as well as on the density and tensile performance of built parts. In order to quantify the recyclability of powders, a new "average usage time" (AUT) parameter is defined to account for both the real usage time of the powder and the virgin-to-used powder mixing ratio. The new parameter, whose applicability can be readily extended to any kind of feedstock powder, offers a significant contribution to achieve a more consistent and economical recycling of raw materials for PBF processing.
2019
- Solid-state phase transformations in thermally treated Ti-6Al-4V alloy fabricated via laser powder bed fusion
[Articolo su rivista]
Mengucci, P.; Santecchia, E.; Gatto, A.; Bassoli, E.; Sola, A.; Sciancalepore, C.; Rutkowski, B.; Barucca, G.
abstract
Laser Powder Bed Fusion (LPBF) technology was used to produce samples based on the Ti-6Al-4V alloy for biomedical applications. Solid-state phase transformations induced by thermal treatments were studied by neutron diffraction (ND), X-ray diffraction (XRD), scanning transmission electron microscopy (STEM) and energy-dispersive spectroscopy (EDS). Although, ND analysis is rather uncommon in such studies, this technique allowed evidencing the presence of retained β in α' martensite of the as-produced (#AP) sample. The retained β was not detectable byXRDanalysis, nor by STEM observations. Martensite contains a high number of defects, mainly dislocations, that anneal during the thermal treatment. Element diffusion and partitioning are the main mechanisms in the α ↔ β transformation that causes lattice expansion during heating and determines the final shape and size of phases. The retained β phase plays a key role in the α' → β transformation kinetics.
2018
- Effects of nano-silica treatment on the flexural post cracking behaviour of polypropylene macro-synthetic fibre reinforced concrete
[Articolo su rivista]
DI MAIDA, Pietro; Sciancalepore, Corrado; Radi, Enrico; Bondioli, Federica
abstract
The effects of a surface nano-silica treatment, carried out with the sol gel method, on the post-cracking behaviour of polypropylene macro-synthetic fibre reinforced concrete are experimentally investigated here for the first time. The present study extends previous experimental and analytical investigations on the corresponding improvement of the bonding properties of a single synthetic macro fibre, performed by means of pull-out test. Scanning electron microscopy is adopted here to explore the changes in the morphological characteristics of polypropylene macro synthetic fibres, before and after mixing in the concrete matrix. A comparative analysis, carried out with three-point bending tests on notched beam specimens, is used to evaluate the effects of the nano-silica treatment on the concrete post cracking behaviour. Increase in concrete toughness and residual post-cracking strength is recorded due to improved adhesion between fibres and the concrete matrix and to the consequent increase in the frictional shear stress generated during the fibre pull-out, especially for large crack opening. As shown by the SEM images, the nano-treatment favours the bonding of the concrete hydration products to the surface of the treated fibres, thus ensuring strengthening of the interface transition zone. In addition, the links between the nano-silica coating and the concrete hydration products improve the frictional shear stress and thus the overall energy absorption, as denoted by the increase of the residual strength during the post-cracking phase.
2018
- Structural characterization and functional correlation of Fe3O4 nanocrystals obtained using 2-ethyl-1,3-hexanediol as innovative reactive solvent in non-hydrolytic sol-gel synthesis
[Articolo su rivista]
Sciancalepore, C.; Gualtieri, A. F.; Scardi, P.; VIVAS DE GONZALEZ, FLOR ALBA; Allia, P.; Tiberto, P.; Barrera, Giulia; Messori, M.; Bondoli, F.
abstract
An original non-hydrolytic sol-gel approach, using 2-ethyl-1,3-hexanediol as reactive solvent, was proposed to synthetize nanostructured magnetite. Iron-oxide nanoparticles were prepared and studied as a function of the precursor-to-solvent ratio. The crystallization degree of nanoparticles was followed by the combined Rietveld and Reference Intensity Ratio method. This procedure has allowed the determination of both amorphous and crystalline content of nanomagnetite, using hematite as suitable internal standard. The results of Rietveld method show that the crystalline content decreases as the precursor-to-solvent is increased, ranging from 67 to 60 wt%. Information on the crystallite size-strain distribution and microstructural evolution of nanocrystals was supplied by line profile analysis of the powder diffraction patterns, employing the Whole Powder Pattern Modeling analysis: the obtained log-normal distribution curves become increasingly narrow and symmetrical, while nanoparticle microstrain increases as the precursor concentration is increased. The dimensional analysis of the Transmission Electron Microscopy images has allowed to obtain the nanoparticle grain-size distribution. Nanoparticle dimensions decreases from 15 to 9 nm increasing the precursor concentration. The comparison between the results of X-ray diffraction and microscopic characterization techniques highlighted the effect of several factors, such as size, shape and microstructure of magnetite nanoparticles, on their functional magnetic response. Magnetic characterizations show that magnetite nanoparticles are not in the superparamagnetic phase even at room temperature, independent of the precursor concentration. On the other hand, the room-temperature saturation magnetization, ranging from 73 to 60 emu/g, is a function of the nanoparticle average size, decreasing as the precursor concentration increases.
2018
- 3D printing processes for photocurable polymeric materials: technologies, materials, and future trends
[Articolo su rivista]
Taormina, Gabriele; Sciancalepore, Corrado; Messori, Massimo; Bondioli, Federica
abstract
The aim of this review is a faithful report of the panorama of solutions adopted to fabricate a component using vat photopolymerization (VP) processes. A general overview on additive manufacturing and on the different technologies available for polymers is given. A comparison between stereolithography and digital light processing is also presented, with attention to different aspects and to the advantages and limitations of both technologies. Afterward, a quick overview of the process parameters is given, with an emphasis on the necessities and the issues associated with the VP process. The materials are then explored, starting from base matrix materials to composites and nanocomposites, with attention to examples of applications and explanations of the main factors involved.
2015
- Pullout behavior of polypropylene macro-synthetic fibers treated with nano-silica
[Articolo su rivista]
DI MAIDA, Pietro; Radi, Enrico; Sciancalepore, Corrado; Bondioli, Federica
abstract
A study of the effects of nano-silica treatment on the bonding properties of macro synthetic polypropylene fibers embedded in a cement matrix is provided in the present paper as a step to improve interfacial properties of the fiber reinforced cementitious composites (FRCC). Polypropylene fibers were treated by sol–gel technique, allowing to obtain a nano-silica coating. Scanning electron microscopy was used to
observe the morphological features of PP fibers surfaces before and after the pullout test. The effects of the treatment were investigated by comparative pullout tests on treated and untreated fibers. An increase in maximum load and energy necessary for the complete extraction of the fiber was observed, as a consequence of the improvement of the interface properties due to the nano-silica hydration activity.
These two parameters control the crack-resistance and ductility properties of FRCC and are deeply affected by bonding and friction phenomena. The hydration products act as chemical and physical anchors, thus producing a densification of the interface transition zone (ITZ). The abrasion phenomena occurring on the fiber surface during the pullout test are responsible of hardening behavior, consisting in the
increase in the frictional shear stress with the fiber slip and thus in the energy required for fiber extraction.
2015
- Quantitative phase analysis and microstructure characterization of magnetite nanocrystals obtained by microwave assisted non-hydrolytic sol–gel synthesis
[Articolo su rivista]
Sciancalepore, Corrado; Bondioli, Federica; Manfredini, Tiziano; Gualtieri, Alessandro
abstract
An innovative preparation procedure, based on microwave assisted non-hydrolytic sol-gel synthesis, to obtain spherical magnetite nanoparticles was reported together with a detailed quantitative phase analysis and microstructure characterization of the synthetic products. The nanoparticle growth was analyzed as a function of the synthesis time and was described in terms of crystallization degree employing the Rietveld method on the magnetic nanostructured system for the determination of the amorphous content using hematite as internal standard. Product crystallinity increases as the microwave thermal treatment is increased and reaches very high percentages for synthesis times longer than 1 h. Microstructural evolution of nanocrystals was followed by the integral breadth methods to obtain information on the crystallite size-strain distribution. The results of diffraction line profile analysis were compared with nanoparticle grain distribution estimated by dimensional analysis of the transmission electron microscopy (TEM) images. A variation both in the average grain size and in the distribution of the coherently diffraction domains is evidenced, allowing to suppose a relationship between the two quantities. The traditional integral breadth methods have proven to be valid for a rapid assessment of the diffraction line broadening effects in the above-mentioned nanostructured systems and the basic assumption for the correct use of these methods are discussed as well.
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.
2009
- Magnetic Memory of a Single-molecule Quantum Magnet Wired to a Gold Surface
[Articolo su rivista]
M., Mannini; F., Pineider; Sainctavit, P. H.; Danieli, Chiara; E., Otero; Sciancalepore, Corrado; Talarico, Anna Maria; M. A., Arrio; Cornia, Andrea; D., Gatteschi; R., Sessoli
abstract
In the field of mol. spintronics, the use of magnetic mols. for information technol. is a main target and the observation of magnetic hysteresis on individual mols. organized on surfaces is a necessary step to develop mol. memory arrays. Although simple paramagnetic mols. can show surface-induced magnetic ordering and hysteresis when deposited on ferromagnetic surfaces, information storage at the mol. level requires mols. exhibiting an intrinsic remnant magnetization, like the so-called single-mol. magnets (SMMs). These have been intensively investigated for their rich quantum behavior but no magnetic hysteresis has been so far reported for monolayers of SMMs on various nonmagnetic substrates, most probably owing to the chem. instability of clusters on surfaces. Using X-ray absorption spectroscopy and X-ray magnetic CD synchrotron-based techniques, pushed to the limits in sensitivity and operated at sub-kelvin temps., we have now found that robust, tailor-made Fe4 complexes retain magnetic hysteresis at gold surfaces. Our results demonstrate that isolated SMMs can be used for storing information. The road is now open to address individual mols. wired to a conducting surface in their blocked magnetization state, thereby enabling investigation of the elementary interactions between electron transport and magnetism degrees of freedom at the mol. scale.