Hafnium(Iv) Carbide

Hafnium carbide
Identifiers
CAS Number	12069-85-1 ;
3D model (JSmol)	Interactive image;
ChemSpider	17340381 ;
PubChem CID	16212551;
	InChI InChI=1S/C.Hf/q-1;+1 Key: NVDNLVYQHRUYJA-UHFFFAOYSA-N ; InChI=1/C.Hf/q-1;+1/rCHf/c1-2 Key: NVDNLVYQHRUYJA-GLWNXBRTAK;
	SMILES [Hf+]#[C-];
Properties
Chemical formula	HfC
Molar mass	190.50 g/mol
Appearance	black odorless powder
Density	12.2 g/cm3
Melting point	3,900 °C (7,050 °F; 4,170 K)
Solubility in water	insoluble
Structure
Crystal structure	Cubic crystal system, cF8
Space group	Fm3m, No. 225
Hazards
EU classification (DSD) (outdated)	not listed
NFPA 704 (fire diamond)	2 2 1
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
	verify (what is ?)
	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] This compound may be seen on future spacecraft as part of the heat shield.

Hafnium carbide is usually carbon deficient and therefore its composition is often expressed as HfC_x (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 HfC_x change from paramagnetic for x ≤ 0.8 to diamagnetic at larger x. An inverse behavior (dia-paramagnetic transition with increasing x) is observed for TaC_x, despite its having the same crystal structure as HfC_x.^[6]

References

↑ Physical Constants of Inorganic Compounds in Lide, D. R., ed (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. pp. 4–44 ff.. ISBN 0-8493-0486-5.
↑ ^2.0 ^2.1 ^2.2 Harry Julius Emeléus (1968). Advances in Inorganic Chemistry and Radiochemistry. Academic Press. pp. 169–170. ISBN 978-0-12-023611-4. https://books.google.com/books?id=-SnCsg5jM_kC&pg=PA169.
↑ Shimada, Shiro (1992). "Oxidation Kinetics of Hafnium Carbide in the Temperature Range of 480o to 600oC". Journal of the American Ceramic Society 75 (10): 2671–2678. doi:10.1111/j.1151-2916.1992.tb05487.x.
↑ 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.
↑ CRC Materials Science and Engineering Handbook (2001).
↑ Aleksandr Ivanovich Gusev; Andreĭ Andreevich Rempel; Andreas J. Magerl (2001). Disorder and order in strongly nonstoichiometric compounds: transition metal carbides, nitrides, and oxides. Springer. pp. 513–516. ISBN 978-3-540-41817-7. https://books.google.com/books?id=jc2D7TGZcyUC&pg=PA513.

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[crc-1] Physical Constants of Inorganic Compounds in Lide, D. R., ed (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. pp. 4–44 ff.. ISBN 0-8493-0486-5.

[b1-2] 2.0 ^2.1 ^2.2 Harry Julius Emeléus (1968). Advances in Inorganic Chemistry and Radiochemistry. Academic Press. pp. 169–170. ISBN 978-0-12-023611-4. https://books.google.com/books?id=-SnCsg5jM_kC&pg=PA169.

[3] Shimada, Shiro (1992). "Oxidation Kinetics of Hafnium Carbide in the Temperature Range of 480o to 600oC". Journal of the American Ceramic Society 75 (10): 2671–2678. doi:10.1111/j.1151-2916.1992.tb05487.x.

[j1-4] 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.

[5] CRC Materials Science and Engineering Handbook (2001).

[6] Aleksandr Ivanovich Gusev; Andreĭ Andreevich Rempel; Andreas J. Magerl (2001). Disorder and order in strongly nonstoichiometric compounds: transition metal carbides, nitrides, and oxides. Springer. pp. 513–516. ISBN 978-3-540-41817-7. https://books.google.com/books?id=jc2D7TGZcyUC&pg=PA513.

v t e Hafnium compounds
Hf(II)	HfB₂
Hf(IV)	HfC HfBr₄ HfCl₄ HfF₄ HfI₄ Hf(C₅H₇O₂)₄ HfO₂ HfSiO₄ HfS₂ Ta₄HfC₅

Identifiers

CAS Number	12069-85-1^Y
3D model (JSmol)	Interactive image
ChemSpider	17340381^Y
PubChem CID	16212551
InChI InChI=1S/C.Hf/q-1;+1^Y Key: NVDNLVYQHRUYJA-UHFFFAOYSA-N^Y InChI=1/C.Hf/q-1;+1/rCHf/c1-2 Key: NVDNLVYQHRUYJA-GLWNXBRTAK
SMILES [Hf+]#[C-]
Properties
Chemical formula	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]
Solubility in water	insoluble
Structure
Crystal structure	Cubic crystal system, cF8
Space group	Fm3m, No. 225
Hazards
EU classification (DSD) (outdated)	not listed
NFPA 704 (fire diamond)	2 2 1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is ^YN ?)
Infobox references