|Molar mass||190.50 g/mol|
|Appearance||black odorless powder|
|Melting point||3,900 °C (7,050 °F; 4,170 K)|
|Crystal structure||cubic, cF8|
|Space group||Fm3m, No. 225|
|EU classification||not listed|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is: / ?)(|
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 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) 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.
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- Lavrentyev, A; Gabrelian, B; Vorzhev, V; Nikiforov, I; Khyzhun, O; Rehr, J (2008). "Electronic structure of cubic HfxTa1–xCy carbides from X-ray spectroscopy studies and cluster self-consistent calculations". Journal of Alloys and Compounds 462 (1-2): 4–10. doi:10.1016/j.jallcom.2007.08.018.
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