羟基氧化铝包覆碳酸钙热分解非等温动力学研究

Study on the non-isothermal decomposition kinetics of AlOOH coated calcium carbonate

在鼓泡碳化法制备的普通及纳米碳酸钙表面包覆上一层羟基氧化铝,根据差热热重分析实验数据,采用master-plot标准作图法和经典动力学机理方程确定了碳酸钙的分解机理并求取相应动力学参数.普通碳酸钙包覆后分解机理由R2变为D1,纳米碳酸钙包覆后分解机理由R3变为R2.用微分和积分方法验证活化能得到很好的一一对应结果.对包覆二元复合物特殊的热分解动力学行为做了初步解释.

The model-free and model fitting approaches were applied to the data for non-isothermal decomposition kinetics of AlOOH surface coated ordinary calcium carbonate as well as the the nano-sized. Master plot method and classical kinetic mechanism equation were used to determine the decomposition mechanisms and the relevant kinetic parameters based on the TGDTA curves. The decomposition mechanisms as revealed by computation showed great differences. Ordinary reference sample decomposed according to the contracting area mechanism Re while A1OOH surface coated calcium carbonate showed the one-dimensional mechanism D1. And as to the nano-sized sample, the mechanism varied from the contracting volume mechanism Ra to the contracting area mechanism R2. Meanwhile, the kinetic parameters Ea of ordinary and nano-sized calcium carbonate verified by both integral method and differential method showed about 100 kJ · mol^-1 and 30 kJ · mo1^-1 , respectively, increase in the decomposition process after being coated. This is possibly because of the as-shell structure of surface AlOOH layer hindering the diffusion of the dissociate COe into the outer atmosphere.