12CaO・7Al_2O_3の生成と熱安定性に及ぼす湿分の影響

概要

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Effects of wet air on the formation and thermal stabili ty of 12CaO ・ 7Al_2O_3 (C_<12>A_7) were studied in atmos pheres with controlled water vapor content. The forma tion process of C12A7 in fired products was examined by X ray powder diffraction and the water included in 11CaO・7Al_2O_3 Ca(OH)_2(C_<11>A_7 Ca(OH)_2) was iden tified by means of Fourier transform infrared spec trophotometer (FT IR) . Anhydrous C_<12>A_7 was pre pared ill dry atmosphere at temperatures above 1150℃. On the other hand, C_<11>A_7 Ca(OH)_2 including hydroxide ions was formed at above 1000℃ ill flowing wet air and the humidity accelerated the formation of the hydrate. It was difficult to make the distinction of X ray diffrac tion patterns between C_<12>A_7 and C_<11>A_7 Ca(OH)_2, but the stretching vibration band of O H at about 3560 cm^<-1> measured by means of FT-IR enabled to identify the hydrate. In a fiow of dried heliulm gas, the hydrate C_<11>A_7 Ca(OH)_2 decomposed into 5Ca0・3Al_2O_3(C_5A_3) with dehydration when it was heated in the temperture range of 1100 to 1250℃. At temperatures above 1250℃, C_5A_3 changed into C_<12>A_7. On the contrary, C_5A_3 changed into C_5A_7 Ca(OH)_2 by heating at about 1100℃ in a flow of wet air.
社団法人日本セラミックス協会の論文
1994-08-01