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Alumina

Example of applications

Alumina is, most of the time, produced from bauxite mineral and mainly used as alpha polymorph to produce parts dense or porous. Alumina ceramics are available with different purity grades, typically 96% to 99.9%. Characteristics improve with purity increase. Alumina is one of the first advanced ceramic used for technical specifications as wear resistance, hardness, thermal stability, corrosion resistance, electrical insulation, applications as high frequency electrical insulation, thermal resistance, chemical resistance, bio-compatibility.

Application : sodium vapor lamp tubes, hip prosthesis, filters and membranes, electronic substrates, electrical insulators, valve balls, valve seats, shafts, bearings, crucibles, mechanical seals…

 


Typical characterictics

 unit99.99%99.8%98%
Densityg/cm3.983.933.83
Cristal sizeμm1-22-55-10
 unit99.99%99.8%98%
Al2O3%>99.99>99.8>98%
Others oxides%<0.01<0.2<2
 unit99.99%99.8%98%
3 points flexural strengthMPa (N.mm-)500380360
Compressive strengthMPa (N.mm-)200019001500
Young ModulusGPa390380360
Hardness (Vickers)MPa180015001300
 unit99.99%99.8%98%
Linear thermal expansion10-⁶.K-7.27.27
Thermal conductivityW.m-.K383227
Maximum temperature usingC180016001500
 unit99.99%99.8%98%
Volume resistivityOhm.cm>10⁴>10⁴>10⁴
Dielectric constant

(25c, 1 MHz)

-9.99.69.5
Dielectric loss

(25c, 1 MHz)

(tan d)

-10-⁴10-⁴2 10-⁴