Search results for "Sintering"
showing 10 items of 165 documents
Dense Mosi2 produced by reactive flash sintering: Control of Mo/Si agglomerates prepared by high-energy ball milling
2011
The objective of this work is to determine the influence of the agglomeration state of the MA mixture on the microstructure and the chemical composition of SPS end-products. In order to produce MoSi2 with a microstructure and a density perfectly controlled via reactive sintering implying an SHS reaction, the characteristics of Mo/Si mechanically activated (MA) powder mixtures were investigated. Indeed, the MA powders have been characterized in terms of their surface specific area, size, phase composition and microstructure. The high-energy milling allows the formation of agglomerates (0.8 to 800 μm) composed of nanometric crystallites of molybdenum and silicon, as a consequence of a continu…
Visible luminescence peculiar to sintered silica nanoparticles: Spectral and decay properties
2015
We report that the sintering at 1000 degrees C of silica nanoparticles (an average diameter of 14 nm) produces a transparent sample that exhibits a bright visible emission under UV excitation. The use of time resolved luminescence spectroscopy and a tunable laser source allows us to single out three contributions centered at 1.96 eV, 2.41 eV and 3.43 eV. The excitation spectra of these emissions evidence bell shaped bands consistent with transitions between localized defects' states. For each emission we study the intensity and the lifetime in the temperature range from 300 K down to 10 K, thus evidencing the competition between radiative and non-radiative processes in the optical cycle of …
SiC-based sandwich material for Flow Channel Inserts in DCLL blankets: Manufacturing, characterization, corrosion tests
2017
This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.
Structure formation and properties of corundum ceramics based on metastable aluminium oxide doped with stabilized zirconium dioxide
2021
Abstract The work presents a successful example of the use of YSZ binary systems for production of composite ceramic materials based on θ-Al2O3 with improved physical and mechanical characteristics which was previously considered an unpromising material. It was first obtained result of extreme nature of dependence of physical and mechanical properties of Al2O3+YSZ on the concentration of YSZ (ZrO2–3mol% of Y2O3) additive. The sintering temperature was decreased on 250 °C (from 1800 to 1550 °C). The phase composition of powders and the structure of ceramics of the Al2O3 + YSZ system were investigated depending on the amount of YSZ dopant, the structure-properties relationship was established…
Alumina supported Pt(1%)/Ce0.6Zr0.4O2 monolith: Remarkable stabilization of ceria–zirconia solution towards CeAlO3 formation operated by Pt under red…
2009
Abstract A structured Pt(1 wt%)/ceria–zirconia/alumina catalyst and the metal-free ceria–zirconia/alumina were prepared, by dip-coating, over a cordierite monolithic support. XRD analyses and Rietveld refinements of the structural data demonstrate that in the Pt supported catalysts ceria–zirconia is present as a Ce 0.6 Zr 0.4 O 2 homogeneous solid solution and that the deposition over the cordierite doesn’t produce any structural modification. Moreover no Pt sintering occurs. By comparing the XRD patterns recorded on Pt/ceria–zirconia/alumina and ceria–zirconia/alumina after three redox cycles, it results that Pt, favouring the structural reorganization of the ceria–zirconia into one cubic …
PLZT—Synthesis, sintering and ceramics microstructure
2006
Abstract Producing of PLZT powders by original two-stage co-precipitation method from mixed solution of inorganic salts ZrOCl 2 ·8H 2 O, TiCl 4 , La(NO 3 ) 3 ·6H 2 O, Pb(NO 3 ) 2 , was carried out. The sequence of phases formed during PLZT synthesis has been studied by X-ray and DTA analysis. Ceramic samples were prepared by two-stage hot-pressing technology. Dielectric, ferroelectric and optical properties have been measured. Ceramic microstructures were studied by SEM with energy dispersive analytical capability (EDX). The fine-grained microstructure was quite uniform with the average grain size of 5–7 μm, without internal or grain boundary porosity. The optical transmittance of ceramic p…
Inelastic Light Scattering Contribution to the Study of the Onset of Sintering of a Nanopowder
2017
International audience; The onset of the sintering of 5 nm ZrO2 and TiO2 nanoparticles is investigated by various methods including inelastic light scattering. A special attention is paid to low-frequency Raman spectra where scattering from confined acoustic vibrations and quasielastic scattering manifest. Significant changes are observed between samples sintered at different temperatures or applied forces. A detailed analysis of the spectra enables to follow the variation of the size of the nanoparticles, the surface area, and the formation of internanoparticles necks in the sintered materials. Finally, low-frequency scattering is shown to be more sensitive to the onset of sintering than m…
Au/CeO2-SBA-15 catalysts for CO oxidation: Effect of ceria loading on physic-chemical properties and catalytic performances
2012
In this work gold catalysts supported over SBA-15 with different CeO 2 loadings (5-30 wt%) were prepared, characterized by N 2 physisorption analyses, SAXS, XRD, STEM and XPS techniques and their catalytic performances were evaluated in the CO oxidation, chosen as reaction test. Over a selected catalyst, Au/CeO 2(20 wt%)-SBA-15, the effect of CO 2 and of the mixture (CO 2 + H 2O) on the CO conversion to CO 2 was also evaluated. Characterizations by SAXS, XRD, STEM and XPS were carried out on selected spent catalysts after CO oxidation. The results were discussed in terms of relationship between morphological, structural, electronic and catalytic properties as a function of the ceria loading…
Sol-gel assisted molten-salt synthesis of novel single phase Y3–2xCa2xTaxAl5−xO12:1%Eu garnet structure phosphors
2022
Strong absorption and emission are the key the features of any phosphor. The results obtained during this study demonstrate the difficulty of the incorporation of tantalum ions into the garnet structure and reveal that only the combination of Sol-Gel synthesis method together with Molten-Salt technique enable to obtain a single-phase cubic garnet structure. Note that, the Sol-Gel synthesis assisted by further processing by Molten-Salt technique can be a potentially new way of material preparation reported in literature. This work also proves that this combination of synthesis methods is much more capable of incorporating ions with large ionic radii into the garnet structure as compared to t…
Temperature control during Spark Plasma Sintering and application to up-scaling and complex shaping
2013
International audience; The determination and the homogeneity of the sample temperature during consolidation of powders by Spark Plasma Sintering (SPS) are addressed. Densifications were carried out in three different facilities differing by their constructors and their size. A structural transformation activated in a TiAl alloy was used as a marker of the sample temperature and finite element modeling were performed to evaluate the temperature at each point of the set-up. A good agreement between experimental and simulated data is exhibited. Alloys with identical microstructures were sintered and the homogeneity of the microstructure was better in the largest machines or when the sample wa…