菱镁矿煅烧过程中氧化镁烧结与晶粒生长动力学的研究

KINETICS OF SINTERING AND GRAIN GROWTH OF MgO DURING CALCINATION OF MAGNESITE

用XRD、BET和TEM研究了菱镁矿煅烧过程中氧化镁烧结与晶粒长大动力学。用表面积降低动力学模型和颗粒长大动力学方程对结果进行了分析,得出结果认为菱镁矿煅烧过程中氧化镁微晶的烧结可分为三个阶段:(1)微晶氧化镁结构的调整,伴随着晶粒迅速长大、比表面积急剧下降;(2)团聚体内孔容积保持不变,团聚体也不收缩,这时烧结过程为表面扩散和蒸发-凝聚所控制;(3)烧结过程为体积或晶界扩散所控制,团聚体出现显著收缩。

The kinetica of sintering and grain growth of MgO during calcination of magnesite have been studied by XRD, BET and TEM.The magnesite particles Decompose rapidly to form aggregates of MgO crystallites during calcination. The results were analysed by kinetics in surface area reduction and equation for grain growth. It is found that the sintering of the MgO cry stallites can be divided into three stages: rearrangement of structure of MgO crystallites with rapid reduction of surface erea and growth of MgO crystal; the process controlled by surface diffusion and evaporation-condensation without change of specific volume of pores and shrinkage of MgO aggregates; and the process controlled by volume and grain boundary diffusion with considerable shrinkage of aggregates