Hafnium carbide (HfC) possesses low toughness and damage tolerance, which limits its application as high‐temperature structural materials. Here we report a route to fabricate a dense HfC with high toughness by incorporating a two‐component SiCN (silicon carbonitride) sintering aid, which is composed of SiCN and turbostratic carbon in the spark plasma sintering. The addition of the SiCN not only enhances the density (up to ~97%) of the final product, but more importantly results in an increase in toughness from 4.3 to 8.5 MPa m^1/2 with only a 10% reduction in the flexural strength. The improvement has been attributed to the unique microstructure of the obtained samples, exhibiting several important characteristics: (a) homogeneously dispersed SiCN and C secondary phases in the HfC matrix to control grain size; (b) HfC grains contain different levels of Si, O, and N to form solid solution; (c) enrichment of free carbon at grain boundaries and triple junctions.

中文翻译：

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碳化ha中添加了碳氮化硅的致密化，强化和增韧

碳化（HfC）具有较低的韧性和损伤耐受性，这限制了其作为高温结构材料的应用。在这里，我们报告了一种通过在火花等离子烧结中掺入由SiCN和透皮层碳组成的两组分SiCN（碳氮化硅）烧结助剂来制造具有高韧性的致密HfC的方法。添加SiCN不仅可以提高最终产品的密度（最高约97％），而且更重要的是可以将韧性从4.3 MPa m ^1/2提高到^1/2弯曲强度仅降低10％。改善归因于所获得样品的独特微观结构，具有几个重要特征：（a）在HfC基体中均匀分散的SiCN和C第二相，以控制晶粒尺寸；（b）HfC晶粒含有不同含量的Si，O和N，形成固溶体；（c）富集自由碳在晶界和三重结处。