水酸化マグネシウム微粒子とカオリンからの緻密質コーディエライトセラミックスの合成

概要

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Thermal reactions and sintering characteristics were investigated to obtain dense cordierite ceramics using kaolin minerals(Al_2O_3・2SiO_2・nH_2O), such as kaolinite or halloysite, and chemically synthesized magnesium hydroxide in the form of ultrafine hexagonal tabular particles. Mixtures of magnesium hydroxide and submicron tabular-kaolinite particles in composition of MgO・Al_2O_3・2SiO_2 resulted in the formation of amorphous state at about 800-900℃ after a reaction of thermal decomposition. The amorphous materials abruptly shrank at about 900℃ up to a relative density of about 90%, above which crystallization of a μ-cordierite phase restrained further densification. Firing the mixtures to about 1300-1350℃ yielded dense α-cordierite ceramics with a relative density higher than 95% and a negligible apparent porosity and showing a linear thermal expansion coefficient of 2.2×10^<-6>/K. On the other hand, mixtures of magnesium hydroxide and submicron needlelike-halloysite particles resulted in insufficient thermal reaction at about 800-900℃ because of the less contact area of mixed particles which, affecting sintering and crystallization characteristics, produced several percents of apparent porosity by firing at 1350℃ for 1h.
社団法人日本セラミックス協会の論文
1998-07-01