Effect of heat treatment temperature and time on phase variation of decomposition product of crystalline aluminum chloride
Effect of heat treatment temperature and time on phase variation characteristic of decomposition product of crystalline aluminum chloride was investigated.The composition and microtopography of crys-talline aluminum chloride were analyzed and discussed by inductively coupled plasma atomic emission spec-trometer(ICP-AES)and metallographic microscope.The results showed that the purity of crystalline alu-minum chloride was relatively high.It contained trace impurity elements such as sodium and calcium,and it belonged to orthorhombic structure.While,aluminum oxide showed irregular elliptic with particle size of 100-210 μm.The phase change characteristics of decomposition product were investigated with thermal gravimetric analyzer and X-ray diffractometer(XRD).The results showed that the crystalline aluminum chloride lost small amount of free water under heat treatment at 80-100 ℃.The decomposition rate after 120 min was 6.95％,and the phase was still crystalline aluminum chloride.The decomposition rate was 35.84％after heat treatment at 150 ℃ for 120 min.The decomposition rate was 87.31％after heat treat-ment at 200 ℃ for 120 min.The decomposition velocity at 600-1 200 ℃ was very fast,and the sample could be completely decomposed within 5 min.The decomposition rate of crystalline aluminum chloride was in direct proportion to heat treatment temperature and time,and heat temperature was the dominant factor.When the heat treatment temperature was 200-700 ℃,the decomposition product phase was ρ-type or amorphous aluminum oxide.When the heat treatment temperature was 800-1 000 ℃,the decomposition product phase was mainly in y-type,8-type and or η-type aluminum oxide.Wherein,a small amount of α-type aluminum oxide was observed in decomposition product at 1 000 ℃.When the heat treatment temper-ature reached 1 200 ℃,all phases were converted into α-type aluminum oxide with most stable energy.This study provided data basis for the theoretical research and pilot equipment selection in heat treatment of crystalline aluminum chloride in the laboratory.It also provided data support for the process parameter optimization in heat treatment of crystalline aluminum chloride.
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