Zirconium carbide is a chemical compound of zirconium metal and carbon with the formula ZrC. It is an introduction phase with a wide region of homogeneity, which ranges from 38.4 to 50 at. % carbon, which corresponds to the formula ZrC 0.62 and ZrC 1.0, respectively [1] .
| Zirconium carbide | |
|---|---|
 | |
 | |
| Are common | |
| Systematic name | zirconium monocarbide |
| Traditional names | zirconium carbide |
| Chem. formula | Zrc |
| Rac formula | Zrc |
| Physical properties | |
| condition | solid |
| Molar mass | 103.23 g / mol |
| Density | 6.73 g / cm³ |
| Thermal properties | |
| T. melt. | 3530 ° C |
| T. Kip. | 5100 ° C |
| Thermal conductivity | 11.6 W / (mK) |
| Classification | |
| Reg. CAS number | 12070-14-3 |
| Pubchem | |
| Reg. EINECS number | |
| SMILES | |
| Inchi | |
Content
Physical Properties
Zirconium carbide is a gray powder. It has a cubic face-centered lattice of the NaCl type, space group Fm3m , with a period a = 0.4693 nm.
- Electrical resistivity 50 μΩ ∙ cm
- Coefficient of linear thermal expansion 7.01 ∙ 10 -6 1 / K (25-1000 ° C)
- Microhardness 28.44 GPa
- Elastic modulus 412 GPa [2]
Getting
Zirconium carbide can be obtained by one of the following methods [3] .
- Direct carbon saturation of zirconium:
The process is conducted in a vacuum, and the starting components are taken in the form of powders;
- The reduction of zirconium carbon with the subsequent formation of carbide:
The process goes through the formation of lower zirconium oxides and the subsequent formation of zirconium carbide by the reaction:
This method is used to produce commercially pure zirconium carbide. Usually the process is carried out at a temperature of about 2000 ° C;
- Gas vapor deposition:
The method is based on the reaction:
Deposition occurs on the surface of a tungsten filament, heated to a temperature of 1700-2400 ° C. Carrying out the process at high temperature (about 2400 ° C) allows to obtain a single-crystal precipitate. Methane may be replaced by toluene , benzene or acetylene .
[four]
Chemical Properties
Zirconium carbide is a chemically stable compound at room temperature with respect to sulfuric , hydrochloric , phosphoric , perchloric , oxalic acids and mixtures of sulfuric and phosphoric, sulfuric and oxalic acids. Insoluble in 10% and 20% sodium hydroxide solutions . It is soluble in boiling sulfuric, nitric , perchloric acids. It is highly soluble in aqua regia , mixtures of sulfuric and nitric, nitric and hydrofluoric acids [3] . Starting at 700 ° C, zirconium carbide reacts with oxygen to form ZrO 2 . At high temperatures, in the presence of nitrogen, zirconium carbonitrides are formed.
Application
The high melting point and small cross section for neutron capture of zirconium carbide allows it to be used as a protective coating on graphite matrices in fuel rods containing uranium and thorium carbides. The zirconium carbide coating deposited by the CVD process on uranium dioxide is used as a diffusion barrier from the products of the half-life of nuclear fuel [5] . ZrC-UC composite is used in thermoelectric generators . Zirconium carbide is also used as an abrasive material for polishing metals [3] .
Notes
- ↑ Samsonov G.V. Physical material science of carbides. - Naukova Dumka, 1974 .-- S. 107-109. - 454 s.
- ↑ Samsonov G.V., Vinitsky I.M. Refractory compounds (reference book). - Metallurgy, 1976 .-- S. 560.
- ↑ 1 2 3 Kosolapova T. Ya. Carbids. - Metallurgy, 1968 .-- S. 300.
- ↑ C 233. Modern production of zirconium carbide. Galevsky G.V. (inaccessible link) . Date of treatment August 3, 2019. Archived November 15, 2017.
- ↑ Effect of Use of Zirconium Carbide Coatings on the VHTR Core Nuclear Design (link not available) . Date of treatment April 21, 2012. Archived October 16, 2011.