Fabricaion Process and Growth Characteristics of AIN Whiskers by Sublimation-Recrystallization Method

Using AIN powders as raw materials and CaO-B2O3 as additives, AIN whiskers were fabricated by a sublimation-recrystallization method. The influences of reaction chamber's structure and temperature gradient on AIN synthetics were inspected, as well as the fabrication mechanism and growth characteristics of AIN whiskers. At the earlier stage of reaction, different morphologies of AIN synthetics such as crystal pillars, whiskers and noncrystalline fibers were produced by VLS mechanism. While at the later stage, VS mechanism occurred, which yielded only AIN whiskers.By XRD and TEM analysis, it was discovered that most AIN whiskers grew on crystal planes {2110}, {101l} and {0001}, along crystal axes [2110], [101w] and [0001], l=0, 1, 2 and 3, w=0, 1, 2and 3. But in some whiskers, oblique growth was observed, therefore nonnormality of macroscopic growth direction to growth crystal plane existed.