シリカガラスの結晶化に及ぼすジルコン添加効果 : 速度論的研究

概要

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SiO_2 ZrSiO_4 powder mixture was prepared frum pow ders of fused silica and zircon with a high speed stirrer at 2400 rpm for 5 min. Mixtures were, then, heated at the soaking temperature between 1275℃ and 1350℃ for different time periods. The fraction of cristobalite precipitated was determined by a quantitative X ray diffraction (QXRD). It was found that zircon affects the rate of transformation of fused silica to cristoba lite. In the initial stage of the heating, the presence of zircon assists the crystallization of fused silica. However, it retards the crystallization as the soaking time is increased. The EDS analysis shows that zirconi um diffuses into the surface layer of silica particle to form a solid solution, resulting in the lattice distortion which may generate a compressive stress on the sur face layer. From the kinetic analysis, the time expo nent, n, in Avrami equation decreases with increasing zircon additions suggesting that the transformation ki netic is controlled by long range diffusion mechanism froun two dimensional plate like growth to one dimen sional needle like growth.
社団法人日本セラミックス協会の論文
1994-06-01