Containerless processing of ceramics by aerodynamic levitation

Abstract

An inexpensive containerless processing technique based on aerodynamic levitation has been developed for high temperature studies on ceramics. A spherical sample of about 0.5 cm diameter levitates in an upward stream of inert gas in a flared graphite nozzle which also acts as a susceptor and heats the sample by radiation to a maximum temperature of 2200°C. The highest heating and cooling rates are 8 and 200°C s^-1, respectively. Solidification studies in this apparatus on the system Al₂O₃-BaO suggest that the eutectic between barium hexaaluminate phase-I and BaAl₂O₄ occurs at less than 28.7 mol% BaO instead of the currently accepted value of 32 mol%. Results of levitation experiments on Al₂O₃-SiC_p composite powder compacts demonstrate the feasibility of using this technique for sintering experiments on refractory ceramics.