On Formation of alpha -Al2O3 Whiskers.

In sintering of ceramic samples of the pseudo-binary systems Al//2O//3-Al, Al//2O//3-AIN, Al//2O//3-TiC, AIN-ZrO//2, as well as of the pseudo-ternary system Al//2O//3-AIN-ZrO//2 in nitrogen, whisker growth was observed above 1500 degree C. The whiskers, examined by means of a scanning electron microscopy with an energy dispersive analyzer as well as by means of X-ray diffraction analysis, were alpha -Al//2O//3 whiskers formed by the VLS (Vapor-Liquid-Solid)-mechanism. Impurities, mainly Mo, Fe, Ni and Co, acted as a fluid, material transporting medium.