Fabrication and Oxidation Behavior of Reactively Hot Pressed TaB2-based Ultra-High Temperature Ceramics

Abstract

TaB2 based UHTCs were fabricated by ‘ in situ' reactive hot pressing from Ta, B4C and Si powders. The reaction was conducted using two processes, (1) powder reactions at temperature from 900 to 19000C and (2) reactive hot pressing between 1800 and 1900oC. The products from the powder reaction of a 3TaJIB4C and 2TaJIB4C/lSi molar mixture were TaB2-TaC and TaB2-SiC, respectively. Two kinds of composites were densified at 19000C for 2 h under 32 MPa in an argon atmosphere via reactive hot pressing. The re1ative densities of TaB2-TaC and TaB2-SiC were 98.6, 98%, respectively. Oxidation behavior was investigated at 15000C under ambient atmosphere. TaB2-SiC composite showed the passive oxidation behavior with parabolic mass gain. TaB2-TaC composite, however, showed formation of a non-protective Taps scale with linear mass gain. The relationships between the microstructural features and mechanical propertied of the composites were discussed.