This technical information has been contributed by
Insaco Incorporated

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Machinable Ceramic Materials - Alumina 94%

Alumina 94% (Al2O3)

Alumina (Al2O3) is one of the most widely specified, general-purpose technical ceramics. All aluminas are very hard and wear resistant, with high-compressive strength even against extreme temperatures and corrosive environments. Aluminas are also excellent electrical insulators and are gas tight.

Alumina is produced by firing a tightly packed powder form of Al2O3 which includes some binder material. Commercially available grades range from 90% up to 99.95% with the higher purity generating somewhat higher hardness. It is possible to machine alumina using diamond grinding techniques. Polishing is also possible, with the degree attainable affected by alumina grain size and production technique, whether pressed or extruded.

90%-97%:
Best suited for metalizing (metal deposition which allows brazing) because of large grain structure.

98%-99.95%:
Common range for isostatically pressed grades, with extruded shapes also available at low cost.

As-fired tolerances are generally only possible within a few percent of dimension. Extremely tight tolerances are attainable, but only by precision machining the fired part using diamond grinding techniques. This adds considerable cost, but tolerances to millionths of an inch are possible, and are often cost-effective due to the extraordinary stability and durability of the finished piece.

Additional options include blends of zirconia with alumina and silicon nitride with alumina. The result is a performance combination that is tougher than alumina alone, but with improved hardness, strength and thermal properties compared to these other materials, especially at elevated temperature.

SEE ALSO: Zirconia Toughened Alumina (ZrO2-Al2O3), or Sialon (Si3N4-Al2O3)

PROPERTY UNITS VALUE
 Mechanical    
 Density gm/cc 3.7
 Hardness Rockwell 45N 82
 Tensile Strength kpsi 28
 Modulus of Elasticity psi x 106 46
 Flexural Strength kpsi 51
 Compressive  Strength kpsi 300
 Poisson's Ratio - 0.21
 Fracture Toughness MPa m1/2 4.0-5.0
 Electrical    
 Dielectric Strength ac volts/mil 212
 Dielectric Constant (at 1 MHz) 9.3
 Volume Resistivity ohm-cm2/cm >1014
 Thermal    
 Coefficient of
 Thermal Expansion
x10-6/°C 6.8
 Thermal Conductivity W/m°K 18
 Specific Heat cal/g°C 0.21
 Max Working Temp °C 1700
 Shock Resistance °C 300
All properties are at room temperature unless otherwise noted.

Engineering data are representative, and are not intended as absolute nor warrantable. Manufacturer’s Data shown is blended from multiple sources and therefore illustrates the marketplace.

This technical information has been contributed by
Insaco Incorporated

Click here to find suppliers


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