PREPARATION, CHARACTERIZATION, AND SINTERABILITY OF WELL-DEFINED SILICA/YTTRIA POWDERS
PREPARATION, CHARACTERIZATION, AND SINTERABILITY OF WELL-DEFINED SILICA/YTTRIA POWDERS
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DOI：
10.1557/jmr.1994.0436
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发表时间：
1994-02-01
影响因子：
2.7
通讯作者：
MATIJEVIC, E
中科院分区：
文献类型：
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作者：
GIESCHE, H;MATIJEVIC, E
通过沉淀技术制备了由二氧化硅核和氧化钇涂层组成的均匀亚微米球形颗粒的分散体，反之亦然。颗粒的总体尺寸和壳的厚度可以在宽范围内变化。使用这些粉末通过沉降、离心或压滤形成绿色体，并评价所得固体的密度和孔径分布。对绿色坯体进行烧结，并跟踪密度、相和显微结构随温度的变化。通常，涂覆的粉末表现出增强的致密化。在>1000 ℃的温度下处理复合固体时，发生Y2 Si 2 O 7的形成，这导致样品的显著收缩。当壳由二氧化硅而不是氧化钇组成时，具有相同二氧化硅/氧化钇比率的涂覆颗粒的粉末在较低温度下烧结。当二氧化硅或氧化钇在包覆颗粒中摩尔过量时，烧结产物具有Y2 Si 2 O 7和过量组分的混合组成。通过在晶粒生长开始之前终止烧结过程，固体显示出明确的微观结构，其中一个相在过量物质的基质中的区域均匀分布。这种性能主要是由于初始粉末在粒度和涂层方面的均匀性。
Dispersions of uniform submicron spherical particles consisting of silica cores and yttria coatings, or vice versa, were prepared by a precipitation technique. The overall size of the particles and the thickness of the shells could be varied over a wide range. Such powders were used to form green bodies by sedimentation, centrifugation, or pressure filtration, and the density and the pore size distribution of the resulting solids were evaluated. The green bodies were sintered and the changes in density, phases, and microstructure were followed with temperature. In general, the coated powders exhibited enhanced densification. On processing composite solids at temperatures >1000 degrees C, the formation of Y2Si2O7 took place, which caused a pronounced shrinkage of the samples. Powders of coated particles having the same silica/yttria ratios sintered at lower temperatures when the shell was composed of silica rather than of yttria. When either silica or yttria were in molar excess in the coated particles, the sintered products had a mixed composition of Y2Si2O7 and the component in excess. By terminating the sintering process before the grain growth started, the solids displayed a well-defined microstructure with a uniform distribution of areas of one phase in the matrix of the matter in excess. This property was mainly due to the uniformity of initial powders in terms of the particle size and the coating.