镁钙砂表面沉积MgO涂层的动力学分析

Kinetics of deposition of MgO coating on surface of MgO-CaO clinker

采用MgO碳热还原和扩散氧化法在镁钙砂表面沉积MgO涂层,研究了MgO涂层的沉积动力学、微观形貌、生长机制以及涂层厚度对镁钙砂抗水化性能的影响。结果表明:随着反应温度的升高,沉积过程存在两个控制机理,在1400～1500℃之间,为化学动力学控制,反应为一级反应,活化能为97.82kJ.mol-1;在1500～1600℃之间,沉积过程为扩散控制,扩散活化能为19.18kJ.mol-1;MgO涂层以方镁石和方钙石为基底均呈二维台阶状生长,但二者生长机制并不完全相同;抗水化实验结果显示最佳处理温度为1600℃、沉积时间为6h,镁钙砂水化质量增加率为0.02%,约是处理前的1/150。

MgO-CaO clinker refractory has the disadvantage of poor hydration resistance.MgO coating was deposited on the surface of MgO-CaO clinker by carbothermal reduction of MgO with carbon black as reducing agent and oxidation of the resulted vapor-phase Mg through diffusion.Deposition kinetics,morphology and growth mechanism of MgO coating and influence of coating thickness on hydration resistance of MgO-CaO clinker were investigated.The results indicated that there existed two kinds of controlling mechanism at 1400—1600℃.Deposition process was controlled by chemical reaction and the apparent activated energy was 97.82 kJ·mol^-1 at 1400—1500℃.However,at 1500—1600℃ the process was controlled by diffusion,and the apparent activated energy was 19.18 kJ·mol^-1.Morphology of MgO coating showed that the MgO growth on magnesia or calcia was typical two-dimensional step-like,but the growth mechanism of MgO coating on either one was not the same.Hydration results showed that the optimal process parameters was that MgO-CaO clinker was treated at 1600℃ for 6 h,and the mass gain percent for treated MgO-CaO clinker was 0.02%,which was 1/150 of untreated one.