SYNTHETIC PROCESS FOR CaO・（2-n）Al₂O₃・n Fe₂O₃ CONTINUOUS SOLID SOLUTION BY IN SITU OBSERVATIONS

Abstract

Grossite which consisted of uniformed CaO・2Al₂O₃ is to be manufactured by rotary kiln under over 1600℃ temperature. Addition of slight amount of Fe₂O₃ raw material makes the melting point of Grossite lower（＜1400℃）. While the function of Fe₂O₃ for manufacturing conditions has not been investigated well. In this paper, we researched the sintering process of Grossite by utilizing dynamic microscopic observations, SEM-EDS and XRD. According to dynamic microscopic observations of CaO・1.8Al₂O₃ 0.2Fe₂O₃ at a temperature of 25℃ to 1500℃ result Fe₂O₃ acted as liquid over 1300℃ and existed as a small particle（20μm）with metallic luster. SEM-EDS analysis of CaO・1.6Al₂O₃ 0.4Fe₂O₃ burned at 1200℃ and cooled by air revealed the ratios of Fe/Al to Ca were not constant. By XRD and Rietveld analysis of CaO・2Al₂O₃ and CaO・1.8Al₂O₃ 0.2Fe₂O₃ at a temperature of 25℃ to 1500℃, Fe₂O₃ was converted to calcium ferrites such as CaO・2Fe₂O₃, CaO・Fe₂O₃, 2CaO・Fe₂O₃ at 1000 to 1100℃. Yield of Grossite from CaO・1.8Al₂O₃ 0.2Fe₂O₃ at 1500℃ was higher than CaO・2Al₂O₃. In addition, a part of Al which is constitution of Grossite crystal structure was substituted to Fe. It was also supposed that calcium ferrites existed as melting liquids form and promoted the diffusion of Al₂O₃.