Oxidation behavior of ZrB2-xSiC composites at 1500 degrees C under different oxygen partial pressures

Abstract

The oxidation behavior of zirconium boride composites with various SiC contents (0-40 vol%) at 1500 degrees C in air (pO(2)= 10(4) Pa) and under low pO(2) (10(-8) Pa) was investigated. Due to different oxidation kinetics calculated from the oxidation depths, the oxidized composites exhibited different layered structures. In addition, the composites of ZrB2-30 vol% SiC (one of the typical compositions) oxidized at 1500 degrees C for 10 h in air and under low pO(2) conditions were analyzed using TEM (transmission electron microscope). In air, the oxidation depth as a function of time indicated a parabolic kinetic behavior, and the ZrB2-40 vol% SiC composite exhibited the lowest parabolic rate constant (k(P)) of 232 mu m(2)/h. Under low pO(2), the oxidation depth as a function of time indicated a parabolic to linear transition kinetic behavior, except for monolithic ZrB2. The monolithic ZrB2 exhibited the lowest parabolic rate constant (k(P)) of 811 mu m (2)/h.