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See detailSlip casting of barium zirconate aqueous concentrated suspensions
Boschini, Frédéric ULg; Guillaume, Bernard ULg; Rulmont, André ULg et al

in Journal of the European Ceramic Society (2006), 26(9), 1591-1598

The rheological behaviour of aqueous suspensions of barium zirconate was studied focusing on the effect of the Volume fraction of particles, leading to the determination of the maximum packing fraction ... [more ▼]

The rheological behaviour of aqueous suspensions of barium zirconate was studied focusing on the effect of the Volume fraction of particles, leading to the determination of the maximum packing fraction. Optimised suspensions dispersed with both polymethacrylic acid and tetramethylammonium hydroxide were slip cast on plaster Moulds to produce discs and crucibles, leading to relative green densities greater than 62% of theoretical ones. Densification was studied at temperatures ranging from 1450 to 1700 degrees C by static and dynamic sintering experiments. Scanning electron microscopy studies demonstrate that slip cast parts are dense and very homogeneous, without any significant processing-related defects or abnormal grain growth. (c) 2005 Elsevier Ltd. All rights reserved. [less ▲]

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See detailInfluence of the shaping effect on hardness homogeneity by Vickers indentation analysis
Guillaume, Bernard ULg; Boschini, Frédéric ULg; Rulmont, André ULg et al

in Journal of the European Ceramic Society (2006), 26(15), 3191-3196

In this study, indentation technique (Vickers indentation) has been unconventionally used to evaluate the homogeneity of barium zirconate ceramic samples which have been shaped through different routes ... [more ▼]

In this study, indentation technique (Vickers indentation) has been unconventionally used to evaluate the homogeneity of barium zirconate ceramic samples which have been shaped through different routes. Statistical tools have been used to estimate the con-elation which can be established between heterogeneities within the samples and their shaping ways. (c) 2005 Elsevier Ltd. All rights reserved. [less ▲]

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See detailOptimization of BaZrO3 sintering by control of the initial powder size distribution; a factorial design statistical analysis
Guillaume, Bernard ULg; Boschini, Frédéric ULg; Garcia-Cano, I. et al

in Journal of the European Ceramic Society (2005), 25(16), 3593-3604

A factorial design statistical analysis has been conducted in order to obtain the optimum conditions in the solid state sintering process of barium zirconate bulk materials, optimum with respect to ... [more ▼]

A factorial design statistical analysis has been conducted in order to obtain the optimum conditions in the solid state sintering process of barium zirconate bulk materials, optimum with respect to density, closed and open porosities. The optimized heat treatment permits to sinter a 99% dense barium zirconate sample at 1650 degrees C during only 2 h. When the temperature is higher than 1650 degrees C or when the heating time is longer than 2 h, a decrease in density is observed. (c) 2004 Elsevier Ltd. All rights reserved. [less ▲]

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See detailDibarium zirconium tetraoxalate trihydrate
Vertruyen, Bénédicte ULg; Robertz, Bénédicte; Guillaume, Bernard ULg et al

in Acta Crystallographica Section C-Crystal Structure Communications (2004), 60(Pt 6), 233-234

A new mixed barium zirconium oxalate, triaquatetra-mu-oxalato-dibarium(II)zirconium(IV), Ba2Zr(C2O4)(4).3H(2)O or [Ba2Zr(C2O4)(4)(H2O)(3)](n), has been synthesized. The complex is built from eightfold ... [more ▼]

A new mixed barium zirconium oxalate, triaquatetra-mu-oxalato-dibarium(II)zirconium(IV), Ba2Zr(C2O4)(4).3H(2)O or [Ba2Zr(C2O4)(4)(H2O)(3)](n), has been synthesized. The complex is built from eightfold-coordinated Zr atoms and eleven- and sixfold-coordinated Ba atoms, linked by oxalate groups. The Zr atom, the two Ba atoms and one water O atom lie on crystallographic twofold axes, so that each coordination polyhedron has imposed C2 symmetry. Packing in the crystal is also assumed through hydrogen bonds. [less ▲]

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See detailPreparation of nanosized barium zirconate powder by precipitation in aqueous solution
Boschini, Frédéric ULg; Guillaume, Bernard ULg; Rulmont, André ULg et al

in Key Engineering Materials [=KEM] (2004), 264-268(Part 1-3), 2335-2338

Several ways were explored to synthesize barium zirconate by soft chemistry methods in aqueous solution. In the first method the synthesis of barium zirconate was initiated by urea decomposition, through ... [more ▼]

Several ways were explored to synthesize barium zirconate by soft chemistry methods in aqueous solution. In the first method the synthesis of barium zirconate was initiated by urea decomposition, through an homogeneous precipitation of barium and zirconium salts followed by a "low temperature" thermal treatment. The kinetic of the reaction and the optimum urea/cation ratio have been determined by means of X-ray diffraction and Inductive Coupled Plasma analyses. It has been demonstrated that an amorphous zirconium hydrated oxide starts to precipitate followed by the precipitation of barium carbonate[1]. A calcination at 1200degreesC during 2 hours gives rise to the formation of a pure barium zirconate phase. In the other methods, barium zirconate was synthesized, in one step without any thermal treatments, by precipitation in highly basic aqueous solutions containing barium and zirconium salts. The effect of the hydroxide concentration was discussed in relation to the barium zirconate phase formation, the particles size and the particles size distribution. For each powder, microstructural characterisations have been performed on sintered bodies in order to evaluate the influence of the thermal treatment on the final density. Dilatometric measurements have been also performed in order to quantify the densification process. Important informations were obtained by these techniques, as for example the existence of an internal porosity which severely limits the final density of the material, even if sintering was performed at high temperature. Thus a careful control of the heating profile seems to be necessary in order to produce dense materials. [less ▲]

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