Abstract Spark plasma sintering technique was utilized to densify the hybrid ZrB2-based UHTCs co-toughened with SiC whiskers and different weights of graphite nano-flakes. The role of nano-graphite on the structure, hardness, densification, and toughness characteristics of ZrB2–SiCw–graphite nanocomposites were inspected. Although all UHTC matrix composites approached to full densification, a 100% dense ceramic was obtained by the incorporation of 5 wt% graphite nano-flakes. The grain coarsening phenomenon stopped significantly in the presence of carbonaceous nano-additive. Phase and microstructural investigations revealed that no in-situ phases were formed during the SPS consolidation, owing to the non-reactivity of ZrB2–SiCw–graphite system. The Vickers hardness dropped slightly from 22 to 19.5 GPa with increasing the nano-graphite content. However, the fracture toughness approached 6.2 MPa.m½ by the incorporation of 5 wt% graphite nano-flakes, remarkably tougher than that of graphitic-carbon-free ceramic with a toughness of 4.7 MPa·m½.

中文翻译：

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石墨纳米薄片对碳化硅晶须增强ZrB2基复合材料特性的影响

摘要 利用火花等离子烧结技术对碳化硅晶须和不同重量的石墨纳米薄片共增韧的混合 ZrB2 基 UHTC 进行致密化。检查了纳米石墨对 ZrB2-SiCw-石墨纳米复合材料的结构、硬度、致密化和韧性特性的作用。尽管所有 UHTC 基复合材料都接近完全致密化，但通过掺入 5 wt% 石墨纳米薄片获得了 100% 致密的陶瓷。在碳质纳米添加剂的存在下，晶粒粗化现象明显停止。相和微观结构研究表明，由于 ZrB2-SiCw-石墨体系的非反应性，在 SPS 固结过程中没有形成原位相。随着纳米石墨含量的增加，维氏硬度从 22 GPa 略微下降到 19.5 GPa。