ABSTRACT Thermal plasma dissociation offers a convenient and attractive route to prepare zirconium oxide from zircon mineral. Transferred and non-transferred arc plasma torches have been used to study zircon dissociation. The major thrust... more
ABSTRACT Thermal plasma dissociation offers a convenient and attractive route to prepare zirconium oxide from zircon mineral. Transferred and non-transferred arc plasma torches have been used to study zircon dissociation. The major thrust has been to accomplish complete dissociation and make the process simpler and cost effective. Technologically, this has been attempted in argon-fired plasma reactors using higher electrical power. The present work reports a cost effective low power transferred arc plasma (TAP) processing method for dissociating zircon by using air as the plasma forming gas. Phase composition and microstructure formation of the dissociated zircon were examined by XRD and SEM with EDX. Experimental results showed that the torch input power and processing time strongly influenced the dissociation percentage as well as the microstructure formation. Further, obtained results revealed that the air plasma medium significantly improved the percentage of zircon dissociation rather than argon plasma medium at 10 and 15 kW power levels. The air plasma gives complete zircon dissociation at 10 kW power with 5 min of processing.
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Waste treatments to induce stabilization or recovery of waste materials is an important part of modern research efforts. Microwave processing has proved to be a powerful tool to convey energy exactly where it is needed by the process, as... more
Waste treatments to induce stabilization or recovery of waste materials is an important part of modern research efforts. Microwave processing has proved to be a powerful tool to convey energy exactly where it is needed by the process, as well as to allow operation in peculiar environments, even in remote-controlled modality. The present work is a summary of three years of joint research between Modena's University and ENEA investigation regarding microwave assisted thermal treatments lead on wastes of different nature, performed at the 2.45 GHz ...
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This paper deals with the development and application of a new technique, Fast Regime-Fluidized Bed Machining (FR-FBM), for the easy-to-automate finishing of as-deposited Atmospheric Plasma Spraying (APS) TiO 2 coatings on AISI 1040 steel... more
This paper deals with the development and application of a new technique, Fast Regime-Fluidized Bed Machining (FR-FBM), for the easy-to-automate finishing of as-deposited Atmospheric Plasma Spraying (APS) TiO 2 coatings on AISI 1040 steel substrates. The effects of leading FBM ...
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The knowledge of the properties of the coatings in terms of scratch and wear resistance is of paramount importance in order to prevent the formation of severe damages. Nonetheless, dealing with the evaluation scratch or wear resistance of... more
The knowledge of the properties of the coatings in terms of scratch and wear resistance is of paramount importance in order to prevent the formation of severe damages. Nonetheless, dealing with the evaluation scratch or wear resistance of an organic coating can be troublesome. They can be strongly dependent on the status of the organic material as well as on the contact condition, applied load and strain rate. Besides, reliable responses cannot be achieved if an appropriate experimental design and a combined usage of proper equipments is not scheduled. In this respect, the present analysis deals with the application of variable speed and load scratch tests to characterize the scratch response and wear resistance of bilayer metal flakes powder coatings. Experimental findings allowed the achievement of consistent trends of the deformation response vs. curing temperature, scratch load and speed as well as their empirical modelling. This way, the overall scratch resistance of the bilayer coatings could be usefully predicted on a broad range of operational conditions, thus providing helpful indications to paint manufacturers and coaters on how to best deal with the application of metal flake powders.
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This study deals with the interrelation between the thermo-rheological behaviour of an epoxy-based powder coating system and its mechanical strength and wear endurance.Matte-finish protective polymeric films deposited by electrostatic... more
This study deals with the interrelation between the thermo-rheological behaviour of an epoxy-based powder coating system and its mechanical strength and wear endurance.Matte-finish protective polymeric films deposited by electrostatic fluidized bed (EFB) and conventional hot dipping fluidized bed (CHDFB) on metal substrates were examined. First, the analysis of thermo-rheological behaviour of the epoxy-based powder coating system was detailed. Secondly, the
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ABSTRACT A statistical evaluation of the association between different elements contained in atmospheric aerosol particles has been made using the microPIXE technique. We derived elemental maps of Al, Si, S, Ca, Cl, K, Fe, Mg spatial... more
ABSTRACT A statistical evaluation of the association between different elements contained in atmospheric aerosol particles has been made using the microPIXE technique. We derived elemental maps of Al, Si, S, Ca, Cl, K, Fe, Mg spatial distribution on the surface of a Nuclepore filter sample. The microPIXE measurements are validated by comparison to conventional PIXE and SEM-EDAX. Then, the spatial coherence of the different elements is analysed using statistical methods. The elements are not homogeneously distributed and the association among specific elements can be identified. MicroPIXE and factorial analysis can be coupled to understand the state of mixing of the different elements on the filter surface.
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The tribological behavior of high-velocity oxyfuel sprayed Co-28%Mo-17%Cr-3%Si coatings, both assprayed and after heat treatments at 200, 400, and 600 �C for 1 h, has been studied. The as-sprayed coating contains oxide stringers and is... more
The tribological behavior of high-velocity oxyfuel sprayed Co-28%Mo-17%Cr-3%Si coatings, both assprayed and after heat treatments at 200, 400, and 600 �C for 1 h, has been studied. The as-sprayed coating contains oxide stringers and is mostly amorphous. It has low hardness (∼6.7 GPa) and toughness and undergoes adhesive wear against 100Cr6 steel. The friction coefficient increases up to ∼0.9, so
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Glass–alumina functionally graded coatings (FGCs) were produced via plasma spraying, a deposition technique for thick (>10–20μm) coatings production, which ensures high flexibility and... more
Glass–alumina functionally graded coatings (FGCs) were produced via plasma spraying, a deposition technique for thick (>10–20μm) coatings production, which ensures high flexibility and good reliability. The samples were obtained by building a graded glass–alumina coating onto an alumina substrate; the coatings were designed as multi-layered systems, each layer having a mean composition slightly different from the neighbouring ones. Two different
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In this study, three different industrial frits BaO–Al2O3–SiO2 (BAS), CaO–MgO–Al2O3–SiO2 (CMAS), CaO–ZrO2–Al2O3–SiO2 (CZAS) have been deposited on porcelainized stoneware tiles by plasma spraying. In the as-sprayed conditions, the... more
In this study, three different industrial frits BaO–Al2O3–SiO2 (BAS), CaO–MgO–Al2O3–SiO2 (CMAS), CaO–ZrO2–Al2O3–SiO2 (CZAS) have been deposited on porcelainized stoneware tiles by plasma spraying. In the as-sprayed conditions, the microstructure of the coatings is defective because of pores, microcracks and low intersplat cohesion. Hot stage microscope and differential thermal analysis measurements made on the glass powders allowed to characterize the frits thermal behaviour. Post process thermal treatments have been arranged, following these indications as well as preliminary tests, in order to achieve the lowest porosity and the highest resistance to abrasion. At the chosen temperatures, a microstructural improvement has been induced, but in the BAS specimens, an optimal sintering has not been accomplished because of the unavoidable full overlapping of the sintering and crystallization processes.
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Plasma-sprayed ceramic coatings were manufactured on sintered alumina–mullite refractory bricks to improve their chemical resistance to molten glass. Mullite and alumina powders were employed. Graded layered coatings were designed and... more
Plasma-sprayed ceramic coatings were manufactured on sintered alumina–mullite refractory bricks to improve their chemical resistance to molten glass. Mullite and alumina powders were employed. Graded layered coatings were designed and produced, to reduce the thermal expansion mismatch with the substrate: in all cases, the upper layer consisted in pure alumina (very resistant to chemical attack); alumina–mullite intermediate layers were added
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Glass and glass-ceramic coatings on ceramic tiles have been manufactured by plasma-spraying high-performance CAS (in wt%—SiO2, 60%; Al2O3, 15%; CaO, 23%; others, traces) and CZS (in wt%—SiO2, 50%; CaO, 31%; ZrO2, 16.5%; Al2O3, 2%; others,... more
Glass and glass-ceramic coatings on ceramic tiles have been manufactured by plasma-spraying high-performance CAS (in wt%—SiO2, 60%; Al2O3, 15%; CaO, 23%; others, traces) and CZS (in wt%—SiO2, 50%; CaO, 31%; ZrO2, 16.5%; Al2O3, 2%; others, traces) glass frits. The CZS system has a surface crystallization at about 1050°C. Such behaviour would not easily allow to obtain a fully crystalline bulk glass-ceramic, but the defectiveness of the plasma-sprayed coating supplies many nucleation sites. Thus, it becomes completely crystalline and well sintered after a 850°C for 30min+1050°C for 15min treatment. The CAS frit, designed not to produce significant crystallization, is well sintered after a 850°C for 30min+950°C for 30min thermal treatment, but remains too brittle due to its glassy nature. A 1050°C treatment allows a few pseudowollastonite crystals to form in a glassy matrix; their formation also hinders sintering. Thus, mechanical properties are inferior to heat-treated plasma-sprayed CZS.
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Glass-alumina functionally graded materials were obtained by percolation and alternatively by plasma spraying. The paper develops a reliable model to predict the functional gradient of the analysed systems. A finite element code, which... more
Glass-alumina functionally graded materials were obtained by percolation and alternatively by plasma spraying. The paper develops a reliable model to predict the functional gradient of the analysed systems. A finite element code, which was able to handle microstructural images, was employed to estimate the effective elastic properties along the gradient direction. The calculated values were compared with experimental data acquired
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Some ceramics have the ability to form direct bonds with surrounding tissues when implanted in the body. Among bioactive ceramics, the apatite/wollastonite (A/W) glass–ceramic, containing apatite and wollastonite crystals in the glassy... more
Some ceramics have the ability to form direct bonds with surrounding tissues when implanted in the body. Among bioactive ceramics, the apatite/wollastonite (A/W) glass–ceramic, containing apatite and wollastonite crystals in the glassy matrix, has been largely studied because of good bioactivity and used in some fields of medicine, especially in orthopaedics and dentistry. However, medical applications of bioceramics are limited
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The viability of a high power diode laser source as effective post-deposition treatment technique of functionally graded titania-HA coatings was checked. In particular, several laser treatments were performed on various coatings... more
The viability of a high power diode laser source as effective post-deposition treatment technique of functionally graded titania-HA coatings was checked. In particular, several laser treatments were performed on various coatings plasma-sprayed under different conditions to verify the presence of an operative window large enough for practical purposes and, subsequently, to identify the most promising settings of the laser parameters.
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... Massimiliano Barletta* and Annamaria Gisario ... Luca Lusvarghi Dipartimento di Ingegneria dei Materiali e dell'Ambiente, University of Modena e Reggio Emilia, Via Vignolese, 905, 41100, Modena, Italy Fax: 0039 0592056243... more
... Massimiliano Barletta* and Annamaria Gisario ... Luca Lusvarghi Dipartimento di Ingegneria dei Materiali e dell'Ambiente, University of Modena e Reggio Emilia, Via Vignolese, 905, 41100, Modena, Italy Fax: 0039 0592056243 E-mail: lucalusv@unimore.it ...
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Glass–alumina functionally graded materials were obtained using two different methods: percolation, which was representative of natural transport based processes, and plasma spraying, which was representative of constructive processes.... more
Glass–alumina functionally graded materials were obtained using two different methods: percolation, which was representative of natural transport based processes, and plasma spraying, which was representative of constructive processes. The specimens produced in this way were investigated to evaluate the effect of production techniques on the final microstructure and gradient, which, in turn, govern the properties and performances of the graded systems. Moreover, post-production heat treatments were performed in order to improve the reliability of the materials examined.
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The prediction of the mechanical properties of polyester powder coatings is of paramount importance, as they have to undergo a wide variety of forces and deformations during their service life. Determine the response of polymeric coatings... more
The prediction of the mechanical properties of polyester powder coatings is of paramount importance, as they have to undergo a wide variety of forces and deformations during their service life. Determine the response of polymeric coatings to the actual loading conditions can be, however, very troublesome as their properties are function of the material physical state, rate-dependence and yield and break behaviour. Further, the characterization of soft, contaminated organic surfaces such as polymers can often cause severe problems with reliability and imaging accuracy due to instrumental artefacts.This is therefore the context in which this paper investigates the capability of multiple parameters scratch tests joined with non-contact CLA profilometry and FE-SEM to detect the scratch response of polyester powder coatings for protective and decorative outdoor applications. Scratch tests with blunt contact geometry were used to evaluate the response of polyester coatings baked at different time–temperature programs and, so, at different stages of their curing process. In particular, being such coatings highly non-linear in their response to mechanical stress or strain, the influence from scratch load and speed was carefully taken into account. Analytical evaluations of the experimental results led to good correlations between the extent of the deformed zone after scratch, scratch parameters and curing operational settings. This allows mapping the scratch response of the polyester topcoats to broad ranges of both scratch parameters and curing conditions.
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ABSTRACT
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ABSTRACT Recently, cermet coatings with Fe-based metal matrix have emerged as a less hazardous and more environmentally friendly alternative to WC–Co-based ones, which have known inhalation toxicity problems. This study therefore aimed to... more
ABSTRACT Recently, cermet coatings with Fe-based metal matrix have emerged as a less hazardous and more environmentally friendly alternative to WC–Co-based ones, which have known inhalation toxicity problems. This study therefore aimed to validate WC-based cermet coatings with Fe-based matrix, obtained using a commercially available feedstock powder, as an alternative to WC–CoCr.HVOF-sprayed WC–15 wt.%FeCrAl layers were therefore obtained using different oxygen and fuel (kerosene) flow rates and powder feed rates; their mechanical and tribological properties were compared to HVOF-sprayed WC–10 wt.% Co–4 wt.%Cr.The WC–FeCrAl coatings always exhibited equi-biaxial compressive residual stress state and possessed dense microstructures, with homogeneous metal matrix, but they contained more oxide inclusions than WC–CoCr. Their characteristics were significantly affected by the normalised oxygen-fuel ratio (λ).Small but meaningful differences existed between the ball-on-disc sliding wear rates of the various WC–FeCrAl coatings, the best sample being that with the most favourable combination of compressive residual stress, low oxidation and high hardness/modulus (H/E) ratio. Its sliding wear resistance was comparable to that of WC–CoCr. The cyclic ball impact resistance of WC–FeCrAl layers was also comparable to that of WC–CoCr, but the dry particle abrasion resistance was inferior, because of the brittleness induced by the oxide inclusions.
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ABSTRACT The innovative High-Velocity Suspension Flame Spraying (HVSFS) process, whereby a conventional gas-fuelled HVOF torch is modified in order to allow the processing of liquid feedstock, was employed in order to spray a TiO2... more
ABSTRACT The innovative High-Velocity Suspension Flame Spraying (HVSFS) process, whereby a conventional gas-fuelled HVOF torch is modified in order to allow the processing of liquid feedstock, was employed in order to spray a TiO2 nanopowder suspension. Three different sets of parameters were employed. The structure, microstructure, nanohardness, tribological properties and photocatalytic activity of the resulting coatings were studied and compared to conventional atmospheric plasma sprayed (APS) and HVOF-sprayed TiO2 coatings, manufactured using commercially available feedstock. Compared to the APS and HVOF techniques, HVSFS enabled the deposition of thinner (20 μm – 60 μm thick), yet high-quality layers. Moreover, it was found that the HVSFS process leaves a fairly large freedom to adjust coating properties (thickness, porosity, anatase content, hardness, etc…) according to the desired objective. Layers with higher anatase content and higher porosity can be produced, in order to achieve higher photocatalytic efficiency than conventional APS and HVOF TiO2. Alternatively, it is possible to deposit dense layers, with lower porosity and pore interconnectivity and better hardness and wear resistance than as-deposited APS and HVOF coatings.
The microstructural features of TiO2 coatings, deposited by High Velocity Suspension Flame Spraying (HVSFS) from a suspension of titania nanoparticles, were investigated by Focused Ion Beam (FIB)+Scanning Electron Microscopy (SEM)... more
The microstructural features of TiO2 coatings, deposited by High Velocity Suspension Flame Spraying (HVSFS) from a suspension of titania nanoparticles, were investigated by Focused Ion Beam (FIB)+Scanning Electron Microscopy (SEM) techniques, by Transmission Electron Microscopy (TEM) and by micro-Raman spectroscopy, and were compared to those of conventional HVOF-sprayed TiO2. Proper selection of the HVSFS deposition parameters results in coatings consisting
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ABSTRACT Bioactive glass coatings based on a novel SiO(2)-P(2)O(5)-CaO-K(2)O system ("Bio-K") were deposited by the High-Velocity Suspension Flame Spraying (HVSFS) technique. Attrition-milled micrometric powder... more
ABSTRACT Bioactive glass coatings based on a novel SiO(2)-P(2)O(5)-CaO-K(2)O system ("Bio-K") were deposited by the High-Velocity Suspension Flame Spraying (HVSFS) technique. Attrition-milled micrometric powder particles, dispersed in water + isopropanol, were sprayed onto Ti plates. The coatings remained entirely glassy, but the glass underwent some structural alterations during processing. After soaking in simulated body fluid (SBF), a rather uniform hydroxyapatite layer developed on the coatings, indicating that they may have the potential to faster osseointegration of prosthetic implants.
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In this research, Ba-hexaferrite coatings for electromagnetic wave absorption applications were deposited by thermal spraying. A suitable powder feedstock was manufactured by blending a BaCO3+Fe2O3 mixture, which was then agglomerated by... more
In this research, Ba-hexaferrite coatings for electromagnetic wave absorption applications were deposited by thermal spraying. A suitable powder feedstock was manufactured by blending a BaCO3+Fe2O3 mixture, which was then agglomerated by spray-drying. The agglomerates were processed by air plasma spraying (APS) without any further treatment or were heat-treated and reactively-sintered to stoichiometric Ba-hexaferrite prior to spraying. As-sprayed coatings were analyzed