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Duarte W.,Groupe dEtudes des Materiaux Heterogenes GEMH | Duarte W.,French National Center for Space Studies | Rossignol S.,Groupe dEtudes des Materiaux Heterogenes GEMH | Vardelle M.,Science des Procedes Ceramiques et de Traitements de Surface SPCTS
Ceramic Engineering and Science Proceedings | Year: 2014

Solution precursor plasma spraying (SPPS) is an innovative process for obtaining finely structured coatings from metallic salt solutions. Lanthanum and zirconium precursors were studied in order to understand their influence on the synthesis of lanthanum zirconate (La2Zr2O7) by SPPS. Thermal analysis revealed that the nature of the precursor affected the hydration shell as well as the formation temperature of zirconium oxide (ZrO2). The surface tensions of precursor solutions in various media were investigated and revealed the influence of the nature of the anion. Different solutions of precursor mixtures were used to obtain La2Zr2O7 splats on metallic substrates. A decrease in the surface tension of the solution led to an increase in the size of the splats. Coating mechanisms by SPPS are governed by the nature of the precursors and solvents. Source


Duarte W.,Science des Procedes Ceramiques et de Traitements de Surface SPCTS | Duarte W.,French National Center for Space Studies | Vardelle M.,Science des Procedes Ceramiques et de Traitements de Surface SPCTS | Rossignol S.,Science des Procedes Ceramiques et de Traitements de Surface SPCTS
Ceramics International | Year: 2016

This study addresses the thermal behavior of La2Zr2O7 powders prepared via two different synthetic routes and the effect of the zirconium counter-cation on their properties, as carried out by dilatometric experiments. Citrate-based compounds exhibit shrinkage, regardless of the precursors used. Preliminary thermal treatment permits the reduction in shrinkage. Nitrate based compounds calcinated at 600 °C show a higher shrinkage (-9.4%) than at 1200 °C (-5.2%) because of the decomposition of the trapped precursors, as revealed by DTA-TGA-MS. Coprecipitated samples present different behaviors as a function of the counter-cation nature. Chloride based compounds leads to shrinkage and phase mixtures, whereas expansion is observed for pure pyrochlore compounds that are synthesized with nitrate. The thermal expansion coefficients of the different compounds are similar to the literature values (9.5-10.10-6 K-1). This study allowed for a better understanding of the densification of the La2Zr2O7 material and its adjusted properties, as a function of the precursor nature and the preparation mode, for application in thermal barrier coatings. © 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Source


Duarte W.,Science des Procedes Ceramiques et de Traitements de Surface SPCTS | Duarte W.,French National Center for Space Studies | Meguekam A.,Science des Procedes Ceramiques et de Traitements de Surface SPCTS | Colas M.,Science des Procedes Ceramiques et de Traitements de Surface SPCTS | And 2 more authors.
Journal of Materials Science | Year: 2014

Lanthanum zirconate with a pyrochlore structure exhibits interesting thermal and structural properties for thermal barrier coating applications operating at high temperature. This study focused on the synthesis of La2Zr2O7 powders by soft chemistry (citrate, coprecipitation, and sol–gel methods), and the effects of the solvent and the nature of the precursors used on the powder properties were investigated. The nature of the counter-cation influenced the structural phase of the compound. A low polarizable counter-cation (chloride) permitted the elaboration of a pyrochlore structure within a larger range of parameters compared with highly polarizable counter-cations (nitrate and acetate). Moreover, the nature of the solvent, and specifically the strength of the interactions within it, had an impact on the particle size. Specifically, the use of water, which is a solvent with strong interactions, led to a smaller particle size than the use of ethanol, which has weaker interactions. Based on these results, the crystalline phase of the powders can be predicted as a function of the precursor and the solvent used for the different synthesis routes, and the particle size can be used to evaluate the reactivity of the powders. © 2014, Springer Science+Business Media New York. Source

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