Hafnium(IV) carbide
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| Identifiers | |
|---|---|
12069-85-1  |
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| ChemSpider | 17340381 |
| Jmol 3D model | Interactive image |
| PubChem | 16212551 |
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| Properties | |
| HfC | |
| Molar mass | 190.50 g/mol |
| Appearance | black odorless powder |
| Density | 12.2 g/cm3[1] |
| Melting point | 3,900 °C (7,050 °F; 4,170 K)[2] |
| insoluble | |
| Structure | |
| cubic, cF8 | |
| Fm3m, No. 225 | |
| Vapor pressure | {{{value}}} |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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| Infobox references | |
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.[2] However, it has a low oxidation resistance, with the oxidation starting at temperatures as low as 430 °C.[3]
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.[4]
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[5]) and melting point.[2]
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.[6]
References
- ↑ Physical Constants of Inorganic Compounds in Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 2.0 2.1 2.2 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ CRC Materials Science and Engineering Handbook (2001).
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
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