Hafnium(IV) carbide

• Hafnium
• Hafnium (IV) carbide
• Hafniummonocarbid

Gray powder

Fixed

12.2 g · cm -3

3890 ° C

Insoluble in water

0.5 mg · m -3 (based on Hf)

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Hafnium carbide (obsolete: Hafnium ) is a chemical compound of the elements hafnium and carbon with the formula HfC, which is characterized by its extraordinary thermal and mechanical stability.

Production and representation

Hafnium carbide may be represented by the same procedures as titanium carbide. It can be obtained by carbothermal reduction of hafnia

Be obtained or by synthesis from the elements at more than 2000 ° C. Since hafnium is very sensitive to nitrogen, necessary to work at the Hochsinterung with very pure argon.

It can also be displayed from hafnium ( IV) chloride.

Also possible is the production by plasma CVD.

Properties

Hafnium carbide is a solid solution in which the carbon to fill the gaps in the octahedral Hafniumkristalls. With a melting point of about 3890 ° C, the material has the highest heat resistance of any known two-component element and can therefore be used as a refractory material (It is not yet certain whether hafnium carbide or tantalum carbide the higher melting point ). Its high hardness is also typical for metal-like carbides. The density is 12.2 g · cm -3.

Hafnium has a crystal structure of the sodium chloride type with considerable phase width ( HfC0 ,99 - HfC0, 60). It has a Vickers hardness of 26.1 GPa and a modulus of 350-510 GPa. It oxidizes in air at 500 ° C. As titanium carbide forms with oxygen and nitrogen solid solutions.

Even higher is the temperature resistance of Tantalhafniumcarbid.

Use

The technical use, however, constrained by the relatively high price of the material limits. However, whiskers and coatings are produced from this material. It is also used in control rods of nuclear reactors.