Preparation of cordierite from fibrous sepiolite

概要

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Mineral sepiolite (Mg4Si6O15(OH)2·6H2O) with fibrous morphology is one of candidates for substituting asbestos. When sepiolite was used as a matrix of an inorganic insulator, it was expected that formation of cordierite (Mg2Al4Si5O18) at elevated temperatures should improve its thermal shock resistance. We investigated formation of α-cordierite by reacting two kinds of sepiolite (as-received and acid-treated sepiolite) with amorphous aluminosilicate fiber (Al2O3·1.88SiO2), γ-alumina (Al2O3) and amorphous silica (SiO2) at 1100-1300°C. A α-cordierite phase was observed above 1200°C for any starting compound, however, anorthite (CaAl2Si2O8) was produced at 1300°C when as-received sepiolite which contained calcite (CaCO3) as an impurity was used. A single phase of α-cordierite was prepared by heating the mixture of acid-treated sepiolite, amorphous aluminosilicate fiber and γ-alumina or acid-treated sepiolite, γ-alumina and amorphous silica at 1300°C.