颗粒级配对固相烧结碳化硅陶瓷的影响

通过粗细碳化硅粉体的颗粒级配实现了致密固相烧结碳化硅(S-SiC)陶瓷的增强增韧, 系统研究了粗粉(~4.6 µm)加入量对烧结试样的致密化、微结构与力学特性的影响。结果表明: 当粗粉加入量不超过75wt%时, 可制备出相对密度≥98.3%的致密S-SiC陶瓷, 烧结收缩率低至14.5%;引入的粗粉颗粒产生钉扎作用, 显著抑制了S-SiC陶瓷中异常晶粒生长, 形成细小的等轴晶粒, 进而提高了S-SiC陶瓷的抗弯强度。同时, 粗粉颗粒的引入导致S-SiC陶瓷的断裂方式由穿晶断裂转变为穿晶-沿晶复合断裂, 使得S-SiC陶瓷的断裂韧性增强。对于粗粉引入量为65wt%的S-SiC陶瓷, 抗弯强度与断裂韧性分别为(440±35) MPa与(4.92±0.24) MPa?m^1/2, 相比于未添加粗粉的S-SiC陶瓷, 分别提升了14.0%与17.1%。

Grain Composition on Solid-state-sintered SiC Ceramics

Strengthening and toughening of dense solid-state-sintered SiC (S-SiC) ceramics was achieved by grain composition of coarse and fine SiC powder, whose median particle sizes were ~4.6 μm and ~0.5 μm, respectively. The fraction effects of coarse SiC powder on densification, microstructures, and mechanical properties of S-SiC ceramics were systematically investigated. High relative densities (higher than 98.3%) were successfully acquired for the S-SiC samples with the fraction of coarse powder less than 75wt%. The linear sintering shrinkage of SiC samples sharply decreased with increasing fraction of coarse powder, with the minimum fraction as low as 14.5%. Moreover, the coarse SiC powder significantly suppressed abnormal grain growth in S-SiC ceramics by Zener pining of grain boundaries. As a result, SiC grains became smaller and equiaxial, which was beneficial for obtaining high flexural strength for S-SiC ceramic. Meanwhile, the introduction of coarse SiC powder induced fracture mode transfer S-SiC ceramic from transgranular type to transgranular-intergranular mixture type, resulting in improved fracture toughness. The S-SiC ceramic added with 65wt% coarse powder achieved an increase of 14.0% in flexural strength ((440±35) MPa) and 17.1% in fracture toughness ((4.92±0.24) MPa·m^1/2).