以溶胶凝胶法合成的亚微米级和市售微米级ZrB_2粉体为原料,B4C和Mo为烧结助剂,在氩气气氛下,常压烧结制得ZrB_2-SiC复相超高温陶瓷材料.研究结果表明,亚微米级ZrB_2超细粉体的加入对ZrB_2-SiC复相陶瓷的常压烧结致密化有一定的促进作用,但对材料性能的影响不太明显.当超细粉体占到粉体质量的30%时,材料的相对密度约为97%.复相材料的三点抗弯强度为(327±56) MPa,弹性模量为(365±30) GPa,维氏硬度和断裂韧性分别为(12.30±0.75) GPa和(3.39±0.35) MPa·m~(1/2).另外,从材料的SEM照片明显看出,在压痕棱角尖端出现裂纹分叉现象,同时在裂纹延伸过程中发生偏转,断裂模式多为穿晶断裂,较少为沿晶断裂.
Commercially available and sol-gel synthesized ZrB_2 ultra-fine ceramic powders were used as the raw materials. Nearly full density ZrB_2-SiC ceramic composites were pressurelessly sintered with B_4C and Mo as the sintering aids under flowing argon. The results show that the sub-micron synthesized ZrB_2 powders could apparently enhance the sintering process, though the properties of the composites were not obviously improved. The mechanical properties were the best as the synthesized powder was 30wt% of the total ceramic powders and the relative density was ～97%. The three-point flexure strength was (327±56) MPa and the elastic modulus was (365±30) GPa. The Vickers hardness and the fracture toughness were (12.30±0.75) GPa and (3.39±0.35) MPa·m~(1/2), respectively. The fracture propagation mode was mainly intragranular and the composite had a low residual porosity.
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