Pressureless sintering of the nanostructured beta-sialon precursor

摘要

The effect of mechanical activation of the powders on the microstructural development and mechanical properties of beta-sialon ceramics was studied. Pressureless sintering in nitrogen was applied to the beta-sialon precursor obtained by activation milling in a planetary mill with a high acceleration of 28 g. The precursor powders consisted of the typical mixtures of silicon and aluminium nitrides as well as of yttria. The mechanically activated powders were amorphized as a result of the formation of defects and of new crystallites boundaries. The sintering experiments were performed at 1450-1600 deg C in a powder bed. The resultant relative density depended on the initial composition and the degree of powder activation in the planetary mill. The relative density of the sintered bodies achieved the value of 98 percent. The nanostructured material was produced after pressureless sintering at 1500 deg C. It is concluded that high activation degree of the powders is necessary to obtain fully dense ceramics.