氧化铝晶粒表面在CaO-Al_2O_3-SiO_2系玻璃非均匀晶化形核时的作用研究

Effect of the Surface of Alumina Crystal Grain on the Heterogeneous Nucleation of CaO-Al_2O_3-SiO_2 System Glasses

抛光的氧化铝晶体表面在玻璃熔融温度和CaO－Al2O3－SiO2（CAS）系玻璃长时间作用下，表面上的几何缺陷全部消失，只剩下结构缺陷，通过DTA、XRD、SEM和EDAX研究，发现在同样的热处理制度下，从CAS系玻璃相接触的氧化铝晶体表面处生长出来的晶体层很薄，且主要是由氧化铝晶粒组成；而从玻璃表面处生长出来的晶体层却很厚，且呈均匀的细柱状晶分布，说明玻璃表面处的非均匀形核速率和生长速率大于风化铝晶体表面处的非均匀形核速率和生长速率，非均匀形核的主要位置是表面处的结构缺陷．形核速率更动力学势垒△GD的影响较大，而受热力学势垒W*的影响较小。氧化铝晶粒不能作为CAS系玻璃晶化时的异质晶核使用。

The methods of DTA, XRD, SEM and EDAX were used to investigate the sample,which was made by means of puting a block of polished alumina crystal substrate containing Al2O3 95 %above into the CAS system glasses in alumina crucible and then heating together to a high temperature(above 1500 ℃) to melt the glasses. Alumina crystal substrate and melting glasses were kept at hightemperature for a long time and then quenched to a temperature slightly above Tg, and again they wereheated at a constant rate (10℃/min) to a temperature slightly above Tp. The glasses were crystallizedboth on the surface and in the interface of alumina crystal substrate. The crystal layer on the surfacewhich grew by the shape of dendrite from the surface to interior was thicker than that in the interfacewhich mainly consist of alumina crystal grain. The dendrite on the surface was both fine and uniform,which shown that the most important sites for heterogeneous nucleation were structure defects on thesurface. The parts between glasses surface and alumina suhstrate interface were still glasses, whichshown that homogeneous nucleation did not take place. The rate for heterogeneous nucleation wasmainly decided by the kinetic barrier to nucleation (△GD) and the thermodynamic barrier to nucleation(W*) had slight influence