Abstract B4C is a structural ceramic, which is very sensitive to cracks and flaws. The present study aims to improve its mechanical performance using pre-oxidation process. The monolithic B4C ceramic and TiB2-SiC/B4C (B4C-TSC) composite ceramic were fabricated using spark plasma sintering technique, and they were pre-oxidized at 800 °C in the air. The effect of pre-oxidation time on microstructure and flexural strength was systematically investigated. The results indicated that 30 min was the optimum pre-oxidation time for both B4C ceramic and B4C-TSC ceramic. At this pre-oxidation time, the maximum flexural strength of 601.5 and 785.2 MPa were obtained for B4C ceramic and B4C-TSC ceramic, respectively. The improved flexural strength was primarily ascribed to the formation of glassy oxide layer during the pre-oxidation process and, in turn, the crack healing effect on the surface of the ceramics. Further increasing pre-oxidation time reduced flexural strength due to the pore formation induced by a large amount of CO gas and an intensive evaporation of B2O3 glass phase.

中文翻译：

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预氧化时间对单片B4C陶瓷和TiB2-SiC/B4C复合陶瓷微观结构和抗弯强度的影响

摘要 B4C是一种结构陶瓷，对裂纹和缺陷非常敏感。本研究旨在通过预氧化工艺提高其机械性能。采用放电等离子烧结技术制备单片 B4C 陶瓷和 TiB2-SiC/B4C（B4C-TSC）复合陶瓷，并在空气中 800 °C 下进行预氧化。系统地研究了预氧化时间对微观结构和弯曲强度的影响。结果表明，30 min 是 B4C 陶瓷和 B4C-TSC 陶瓷的最佳预氧化时间。在此预氧化时间，B4C 陶瓷和 B4C-TSC 陶瓷分别获得了 601.5 和 785.2 MPa 的最大弯曲强度。弯曲强度的提高主要归因于预氧化过程中玻璃状氧化层的形成，反过来，陶瓷表面的裂纹愈合效果。由于大量 CO 气体和 B2O3 玻璃相的强烈蒸发导致孔隙形成，进一步增加预氧化时间会降低抗弯强度。