カオリンからの針状ムライトの生成に及ぼすアルミナ,ガラスの添加効果

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The yield of mullite produced by firing a mixture of New Zealand kaolin and alumina (Al_2O_3/SiO_2=1.0 in molar ratio) increased rapidly above 1500℃ as compared with that for kaolin alone. The mullite was recovered by treating the fired body with fluoric acid. The mullite particles obtained by firing the kaolin-alnmina mixture at 1600℃ for 10 h were granular. However, the needle-like mullite particles were produced by firing kaolin and a kaolin-alumina mixture both containing float glass powder (10 wt%) at 1400℃. Needle-like mullite particles obtained by firing kaolin, kaolin-alumina, kaolin-glass and kaolin-alumina-glass at 1600℃ for 10 h were 6, 3, 13.5 and 12.5 μm long, respectively. The growth rate of needle-like mullite particles produced in the samples mixed with glass could be expressed as L^3=1.85×10^<18> exp (-5.57×l0^5/RT)t, where L is the length of needle-like mullite particles (μm), R the gas constant (J/K・mol), T the absolute temperature (K) and t the time (h). However, this equation was not applicable when the yield of mullite was close to 100%. The Al_2O_3/SiO_2 molar ratios of needle-like mullites obtained by firing kaolin-glass and kaolin-alumina-glass mixtures at 1600℃ for 10 h were 1.59 and 1.62-1.64, respectively, larger than 1.50 for the theoretical mullite composition. Their lattice constants a_0 were 7.669Å and 7.667Å, respectively. These values were also longer than 7.5456Å of JCPDS 15-776. The longer a_0 values might have resulted from the alumina-rich composition of the needle-like mullite particles.
社団法人日本セラミックス協会の論文
1992-05-01

カオリンからの針状ムライトの生成に及ぼすアルミナ,ガラスの添加効果

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