Zirconium diboride


Zirconium diboride

Chembox new
ImageFile =
ImageSize =
IUPACName = Zirconium Diboride
OtherNames = ZrB2
Section1 = Chembox Identifiers
CASNo = 12045-64-6
PubChem =
SMILES =

Section2 = Chembox Properties
Formula = ZrB2
MolarMass = 112.85 g/mol
Appearance =
Density = 6.085 g/cm3
MeltingPt = ~3246°C
BoilingPt =
Solubility = Insoluble

Section3 = Chembox Hazards
MainHazards = Uninvestigated
FlashPt =
Autoignition =

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 ] ]

References


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