M. Balat et al., OXIDATION OF SILICON-NITRIDE UNDER STANDARD AIR OR MICROWAVE-EXCITED AIR AT HIGH-TEMPERATURE AND LOW-PRESSURE, Journal of Materials Science, 32(5), 1997, pp. 1187-1193
During the atmospheric re-entry of space shuttles, the thermal constra
ints due to the hypersonic velocity can lead to very extensive damage
on materials of the protective heat shield (oxidation; thermal shock,
etc.). In order to test the oxidation resistance of such materials, we
have realized an experimental set-up called MESOX which associates a
concentrated radiation solar furnace and a microwave generator. The ma
ximal heat flux is 4.5 MW m(-2), and the temperature ranges up to 2500
K. The total pressure is in the range 10(2)-10(4) Pa. For silicon-bas
ed ceramics, it is necessary to have a good knowledge of the condition
s for the existence of a protective silica layer. The determination of
the transition between passive and active oxidation is done, in the c
ase of sintered silicon nitride, under standard and microwave-excited
air.