Oxidation behaviour of a pressureless sintered HfB2-MoSi2 composite

The thermal stability of a 80 vol% HfB2+ 20 vol% MoSi2 composite is tested under oxidizing environment. Oxidation tests are carried out in flowing synthetic air in a TG equipment from 1000 to 1400°C with exposure time of 30 hours. At temperatures 1200°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°C, the kinetic curves deviate from a parabolic behaviour, being more close to a logarithmic-parabolic behaviour