Zirconium diboride

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IUPACName = Zirconium Diboride
OtherNames = ZrB₂
Section1 = Chembox Identifiers
CASNo = 12045-64-6
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Section2 = Chembox Properties
Formula = ZrB₂
MolarMass = 112.85 g/mol
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Density = 6.085 g/cm³
MeltingPt = ~3246°C
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Solubility = Insoluble
Section3 = Chembox Hazards
MainHazards = Uninvestigated
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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 ultrasonic flight or rocket propulsion systems.

ZrB₂ parts are usually hot pressed (Pressure applied to the powder with heat being applied) 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. Pressureless sintering of ZrB₂ is possible with sintering additives such as Boron carbide and Carbon which react with the surface oxides to increase the driving force for sintering but mechanical properties are degraded compared to hot pressed ZrB₂. [ [http://scholarsmine.mst.edu/post_prints/PressurelessDensificationofZirconiumDiboridewith_09007dcc804d6b89.html Missouri S&T Research - Pressureless densification of Zirconium Diboride with Carbon Additions ] ]

Additions of ~30vol% 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. [ [http://scholarsmine.mst.edu/post_prints/ThermodynamicAnalysisofZrB2-SiCOxidationFormation_09007dcc804d8025.html Missouri S&T Research - Thermodynamic analysis of ZrB₂-SiC oxidation: formation of a SiC-depleted region ] ]

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