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|Section2= |Section3= |Section7= }} Hafnium carbide (HfC) is a chemical compound of hafnium and carbon. With a melting point of about 3900 °C it is one of the most refractory binary compounds known.〔 However, it has a low oxidation resistance, with the oxidation starting at temperatures as low as 430 °C. Hafnium carbide is usually carbon deficient and therefore its composition is often expressed as HfCx (x = 0.5 to 1.0). It has a cubic (rock-salt) crystal structure at any value of x. Hafnium carbide powder is obtained by the reduction of hafnium(IV) oxide with carbon at 1800 to 2000 °C. A long processing time is required to remove all oxygen. Alternatively, high-purity HfC coatings can be obtained by chemical vapor deposition from a gas mixture of methane, hydrogen, and vaporized hafnium(IV) chloride. Because of the technical complexity and high cost of the synthesis, HfC has a very limited use, despite its favorable properties such as high hardness (>9 Mohs〔CRC Materials Science and Engineering Handbook (2001).〕) and melting point. The magnetic properties of HfCx change from paramagnetic for x ≤ 0.8 to diamagnetic at larger x. An inverse behavior (dia-paramagnetic transition with increasing x) is observed for TaCx, despite its having the same crystal structure as HfCx. ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hafnium(IV) carbide」の詳細全文を読む スポンサード リンク
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