Oxidation behaviour of a pressureless sintered HfB_2-MoSi_2 composite

摘要

The thermal stability of a 80-vol. percent HfB_2 + 20 vol. percent MoSi_2 composite is tested under oxidizing environment. Oxidation tests are carried out in flowing synthetic air in a TG equipment from 1000 to 1400 deg C with exposure time of 30 h. At temperatures > = 1200 deg C the silica resulting from oxidation of molybdenum disilicide seals the sample surface, preventing hafnium diboride from fast degradation. Analysis of the kinetics is carried out through fitting of the thermogravimetric curves. Between 1200 and 1400 deg C, the kinetic curves deviate from a parabolic behaviour, being more close to a logarithmic-parabolic behaviour.