| Zirconium diboride | |
|---|---|
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| IUPAC name |
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| Other names | ZrB2 |
| Identifiers | |
| CAS number | [] |
| Properties | |
| Molecular formula | ZrB2 |
| Molar mass | 112.85 g/mol |
| Appearance | grey-black powder |
| Density | 6.085 g/cm3 |
| Melting point |
~3246 °C |
| Solubility in water | Insoluble |
| Structure | |
| Crystal structure | Hexagonal, hP3 |
| Space group | P6/mmm, No. 191 |
| Hazards | |
| Main hazards | Uninvestigated |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
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Zirconium diboride (ZrB2) is a highly covalent refractory ceramic material with a hexagonal crystal structure. ZrB2 is an Ultra High Temperature Ceramic (UHTC) with a melting point of 3246 °C. This along with its relatively low density of ~6.09 g/cm3 (measured density may be higher due to hafnium impurities) and good high temperature strength makes it a candidate for high temperature aerospace applications such as hypersonic flight or rocket propulsion systems.
ZrB2 parts are usually hot pressed (pressure applied to the heated powder) and then machined to shape. Sintering of ZrB2 is hindered by the material's covalent nature and presence of surface oxides which increase grain coarsening before densification during sintering.
Additions of ~30 vol% SiC to ZrB2 is often added to ZrB2 to improve oxidation resistance through SiC creating a protective oxide layer - similar to aluminum's protective alumina layer.[2]
References
- ^ Missouri S&T Research - Pressureless densification of Zirconium Diboride with Carbon Additions
- ^ Missouri S&T Research - Thermodynamic analysis of ZrB₂-SiC oxidation: formation of a SiC-depleted region
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