Some properties of mullite powders prepared by chemical vapour deposition. I: Preparation of mullite powder

• Published in: Journal of materials science 1995-03, Vol.30 (5), p.1158-1165
• Main Authors: ITATANI, K, KUBOZONO, T, HOWELL, F. S, KISHIOKA, A, KINOSHITA, M
• Format: Article
• Language: English
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Chemical industry and chemicals; Exact sciences and technology; Structural ceramics; Technical ceramics
• ISSN: 0022-2461; 1573-4803

The chemical deposition (CVD) technique based on reaction among aluminium chloride (AlCl sub 3 ), silicon chloride (SiCl sub 4 ) and oxygen was applied to produce sub- mu m sized mullite (3Al sub 2 O sub 3 .2SiO sub 2 ) powder. The conditions for preparing the best crystalline mullite were as follows: (i) the reaction temperature, 1200 deg C; (ii) the flow rate of carrier gas (argon) of AlCl sub 3 , 0.3 dm exp 3 /min, and that of SiCl sub 4 , 0.3 dm exp 3 /min; (iii) the sublimation temperature of AlCl sub 3 , 180 deg C, and the evaporation temperature of SiCl sub 4 , 25 deg C; and (iv) the flow rate of O, 0.9 dm exp 3 /min. The as-prepared powder contained mullite, a small amount of gamma -Al sub 2 O sub 3 (Al-Si spinel) and amorphous material; this powder was composed of spherical primary particles of approx0.05 mu m diameter. Although only mullite was present at the calcination temperature of 1300 deg C, a small amount of alpha -Al sub 2 O sub 3 was formed at 1400-1700 deg C. Agglomeration due to primary particle growth started at temperatures > 1400 deg C.