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339 results on '"Estournès, Claude"'

25. Friction and Wear Behavior of Double-Walled Carbon Nanotube-Yttria-Stabilized ZrO 2 Nanocomposites Prepared by Spark Plasma Sintering †.

Author

Kasperski, Anne, Alkattan, Dalya, Turq, Viviane, Estournès, Claude, Laurent, Christophe, and Weibel, Alicia

Subjects
DOUBLE walled carbon nanotubes, MULTIWALLED carbon nanotubes, DEFORMATION of surfaces, ELASTIC deformation, WEAR resistance
Abstract

Double-walled carbon nanotube-yttria-stabilized ZrO2 nanocomposites are prepared by a mixing route followed by Spark Plasma Sintering. The double-walled carbon nanotubes (DWCNTs) have been previously subjected to a covalent functionalization. The nanocomposites present a high densification and show a homogenous dispersion of DWCNTs into a matrix about 100 nm in size. The DWCNTs are well distributed at the matrix grain boundaries but form larger bundles upon the increase in carbon content. The Vickers microhardness of the nanocomposites decreases regularly upon the increase in carbon content. Incorporation of carbon at contents higher than 2 wt.% results in significantly lower friction coefficients, both against alumina and steel balls, possibly because of the elastic deformation of the DWCNTs at the surface of the sample. Their presence also favors a reduction of the steel/ceramic contacts and reduces the wear of the steel ball at high loads. DWCNTs improve wear resistance and reduce friction without incurring any severe damage, contrary to multi-walled carbon nanotubes. [ABSTRACT FROM AUTHOR]

Published
2024
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35. Continuous Flow Synthesis of Yttria‐Stabilized‐Zirconia Nanocrystals in Supercritical Solvothermal Conditions.

Author

Denis, Yoan, Elissalde, Catherine, Suchomel, Matthew R., Gayot, Marion, Weill, François, Labrugère, Christine, Etienne, Laetitia, Vaudesca, Mélanie, Cam, Nithavong, Chung, U‐Chan, Reveron, Helen, Chevalier, Jérome, de Beauvoir, Thomas Hérisson, Estournès, Claude, Aymonier, Cyril, Goglio, Graziella, and Philippot, Gilles

Subjects
NANOCRYSTALS, RAMAN scattering, X-ray scattering
Abstract

The synthesis of yttria‐stabilized zirconia nanoparticles with a fine control on the chemical composition and the distribution of yttrium cations is of major interest to master the mechanical, optical or ionic conduction properties of the final material. However, a fine control of this chemical homogeneity within the particles, especially above 5 mol.% of yttria (Y2O3), is challenging with conventional synthesis routes. In the present study, for the first time the interest of using supercritical sol–gel like synthesis is demonstrated for the continuous production in a single step of high quality zirconia (ZrO2) nanocrystals of 7 nm stabilized with Y2O3 without post‐treatment. Three compositions are investigated, i.e., 1.5, 3, and 8 mol.% of Y2O3 and in‐depth physico‐ chemical characterizations such as X‐ray diffraction, total X‐ray scattering, High‐resolution electron microscopy, Raman and X‐ray photoelectron spectroscopy are performed to asses and thus prove the successful synthesis of these different compositions while keeping a good chemical homogeneity. This enables to confirm that this original process leads to a unique and fine structural control for such small yttria‐doped zirconia nanocrystals. [ABSTRACT FROM AUTHOR]

Published
2024
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36. Preface

Author

Cao, Giacomo, primary, Estournès, Claude, additional, Garay, Javier E., additional, and Orrù, Roberto, additional

Published
2019
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40. Thermal conductivity of binary ceramic composites made of insulating and conducting materials comprising full composition range – Applied to yttria partially stabilized zirconia and molybdenum disilicide

Author

Cernuschi, Federico (author), Kulczyk-Malecka, Justyna (author), Zhang, Xun (author), Nozahic, Franck (author), Estournès, Claude (author), Sloof, W.G. (author), Cernuschi, Federico (author), Kulczyk-Malecka, Justyna (author), Zhang, Xun (author), Nozahic, Franck (author), Estournès, Claude (author), and Sloof, W.G. (author)

Abstract

The thermal diffusivity and conductivity of dense and porous binary composites having an insulating and conducting phase were studied across its entire composition range. Experimental evaluation has been performed with MoSi2 particles embedded into yttria partially stabilized zirconia (YPSZ) as prepared by spark plasma sintering (SPS). The thermal diffusivity of the composites was measured with Flash Thermography (FT) and Laser Flash Analysis (LFA) techniques. Subsequently, the thermal conductivity was determined with the measured heat capacity and density of the composites. The actual volume fraction of the conducting phase of the composites was determined with image analysis of X-ray maps recorded with scanning electron microscopy (SEM). The phases present and their density were determined with X-ray diffractometry (XRD) using Rietveld refinement. The thermal diffusivity increases with increasing volume fraction of MoSi2. Porosity reduces the thermal diffusivity, but the effect diminishes with high volume fractions MoSi2. The thermal diffusivity as a function of the MoSi2 volume fraction of the YPSZ composites is captured by modelling, which includes the porosity effect and the high conductivity paths due to the percolation of the conductive phase., Team Joris Dik

Published
2023
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