Preparation of HfB2/SiC composite powders by sol-gel technology

Sol-gel technology was used to chemically modify the surface of HfB2 powders with highly dispersed silicon carbide using two carbothermy protocols: (1) under heating to 1500A degrees D in flowing argon (100 mL/min) without exposure and (2) under dynamic vacuum conditions (p similar to 1 x 10(-5)-1 x 10(-6) MPa) at 1400A degrees D with 4-h exposure. The phase composition and microstructural features of the thus-prepared HfB2/xSiC (x = 10-65 vol %) composite powders were studied. The products prepared by the second protocol showed an enhanced oxidation resistance in the range 20-1400A degrees C in flowing air compared to individual HfB2.