The residual carbon content of ultra-fine hafnium carbide (HfC) powder was controlled by the optimization of the synthesis process, and the effect of residual carbon on the densification of HfC powder was analyzed. The amount of residual carbon in the HfC powder could be reduced by the de-agglomeration of HfO₂ powder before the carbo-thermal reduction (CTR) process. The average particle size of HfO₂ powder decreased from 230 to 130 nm after the de-agglomeration treatment. Ultra-fine (d₅₀: 110 nm) and highly pure (metal basis purity: >99.9 % except for Zr) HfC powder was obtained after the CTR at 1600 °C for 1 h using the C/Hf mixing ratio of 3.3. In contrast, the C/Hf ratio increased to 3.6 without the de-agglomeration treatment, indicating that a large amount of excess carbon was required for the complete reduction of the agglomerated HfO₂ particles. HfC ceramics with high relative density (>98 %) were obtained after spark plasma sintering at 2000 °C under 80 MPa pressure when using the HfC powder with low excess carbon content. In contrast, the densification did not complete at a higher temperature (2300 °C) and pressure (100 MPa) when the HfC powder contained a large amount of residual carbon. The results clearly indicated that residual carbon suppressed the densification of HfC powder in case the carbide powder had low oxygen content, and the residual carbon content could be controlled by the optimization of the synthesis process. The average grain size and Vickers hardness of the sintered specimen were 6.7(±0.7) μm and 19.6 GPa, respectively.

通过优化合成工艺控制了超细碳化f粉末的残余碳含量，并分析了残余碳对HfC粉末致密化的影响。在碳热还原（CTR）工艺之前，可以通过HfO ₂粉末的解聚来减少HfC粉末中的残留碳量。解聚处理后，HfO ₂粉末的平均粒径从230 nm降低至130 nm。超细（d ₅₀：110nm）和高纯度（金属基本纯度：除Zr外，＞ 99.9％）HfC粉末在C / Hf混合比为3.3的情况下在1600℃下CTR 1小时后获得。相反，在不进行解团聚处理的情况下，C / Hf比增加到3.6，这表明要完全还原团聚的HfO ₂，需要大量过量的碳。粒子。使用过剩碳含量低的HfC粉末在2000°C，80 MPa的压力下进行火花等离子体烧结后，可获得具有较高相对密度（> 98％）的HfC陶瓷。相反，当HfC粉末含有大量残留碳时，在较高的温度（2300°C）和压力（100 MPa）下致密化未完成。结果清楚地表明，在碳化物粉末含氧量较低的情况下，残余碳抑制了HfC粉末的致密化，并且可以通过优化合成工艺来控制残余碳含量。烧结样品的平均晶粒尺寸和维氏硬度分别为6.7（±0.7）μm和19.6 GPa。