アルミナ-シリカゲルの共沈物を加熱して得られるムライトの性状 : アルミナ-シリカ系に関する研究(第2報)

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Mullite is studied using co-precipitated gels obtained from mixed silicon ethylate and aluminium ethylate. Mullite is formed at higher temperatures by the thermal decomposition of the spinel-type phase. In the temperature range 1000゜〜1200℃ mullite exhibites two-dimensional grain growth in accordance with the equation d α/dt=Kα (1-α), where t=time, α=amount of mullite- An activation energy of 11〜12kcal/mol is obtained. At temperatures higher than 1200℃, mullite shows a remarkable grain growth. The lattice parameters a and c of mullite decrease, and the parameter b increases, when the temperature of heat treatment is increased. Also a is increased and b is decreased as the Al_2O_3/SiO_2 ratio increases beyond 3 : 2. The c parameter shows little change with A1_2O_3/SiO_2 ratio in the range 3 : 2 to 2 : 1. The time variations of a and c are thought to be due mainly to the chemical composition, and the time variation of b due mainly to a process of ordering of the lattice. The diagram of c/a〜a/b shows clearly the influence of chemical composition, and suggests the possible existence of mullite containing more silica than 3 : 2. According to the electron-microscopic studies, mullite showed always a needle-1ike mor-phology irrespective of the mode of formation. [Received March 17,1962]
社団法人日本セラミックス協会の論文
1962-08-01