PURPOSE: To prepare fine powder of silicon ceramic raw material having high purity, easily, at a low cost, by reacting an alkali silicate with a mineral acid, mixing the obtained silica with carbon or a carbon compound, and calcining the mixture in a non-oxidative atmosphere.
CONSTITUTION: An alkali silicate such as sodium silicate is mixed with a mineral acid such as sulfuric acid to obtain a mixture having an Si concentration of ≥15wt%, and reacted under thorough agitation until the mixture becomes non- viscous liquid. The hydrogel thus obtained is filtered, washed with water, and dried to obtain highly pure silica. The silica is mixed with carbon such as carbon black and/or a carbon compound such as sucrose, and calcined at ≥1,400°C in reducing atmosphere or at ≤1,600°C in nitrogen gas atmosphere to obtain powdery raw material of ceramic composed of SiC or SiN. As an alternative method, the objective product can be obtained by reacting an alkali silicate with a mineral acid in the presence of a carbon source.
NISHINO KOUZOU
ONO HIROSHI
NAKAMURA MASAMI
SASAKI HIROMI
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