Hafnium carbide

Hafnium(IV) carbide

Identifiers
CAS Number	12069-85-1 Y
3D model (Jmol)	Interactive image
ChemSpider	17340381 Y
ECHA InfoCard	100.031.910
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
Melting point	3,900 °C (7,050 °F; 4,170 K)
Solubility in water	insoluble
Structure
Crystal structure	cubic, cF8
Space group	Fm3m, No. 225
Hazards
EU classification (DSD)	not listed
NFPA 704	2 2 1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
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. 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 HfC_x (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) and melting point.

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.