Influence of the milling environment on the reaction progress in the Si–Al2O3 system

In the solid-state reaction of alumina and silicon in nitrogen the value of the surface area seems to be the most important factor. Agglomerates formed during the milling process can exhibit unfavourable effect on the reaction progress: non-homogenous distribution of both kinds of particles and limited nitrogen access to the surface of silicon particles during subsequent nitridation. The milling process was performed in the attritor mill using two different environments: polar and non-polar with addition of surfactant. For non-polar environment an additional mixing of fine powders on a roller bench was applied. Surface area of powders was examined by BET. Mass changes and shrinkage of the tablets were measured after nitridation at 1250 °C. Thermal properties of the samples were determined by dilatometry and TG measurements. The nitrogen content was measured by mass gain whereas the sample homogeneity was verified by SEM studies.