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Transparent Ceramic Spinel
Magnesium aluminate spinel (MgAl2O4) is a cubic crystal structure with an excellent optical transmission from 0.2 to 5.5 microns in its polycrystlalline form. Optical quality transparent spinel has been produced by sinter/HIP, hot pressing, and hot press/HIP operaiotns, and it has been shown that the use of a hot isostatic press can improve its optical and physical properties.
As shown in a field demonstration, a Spinel ceramic plate can survive a direct hit from a .50 BMG round fired at close range. By all indications, this is an important new technology that should find its way into military vehicles in the near future.
Spinel offers some processing advantages over AlONTM, such as the fact that spinel powder is available from commercial manufacturers while AlON powders are proprietary to Raytheon. It is also capable of being processed at much lower temperatures than AlONTM, and has been shown to possess superior optical properties within the infrared (IR) region. The improved optical characteristics make spinal attractive in sensor applications where effective communication is impacted by the protective missile dome's absorption characteristics.
Spinel Physical and Optical Properties
Thermal conductivity : 17.0 W/m.k @ 20deg. C
Crystal structure : Cubic
Thermal expansion : 7.33 x 10-6/K (20-500deg. C)
Density : 3.58g/cm3
Refractive index : 1.730-1.598(0.4-5.0µm)
Melting point : 2135 deg. C
Transmittance : (d=4 mm) 0.4-0.8µm >75% 3-5µm, 80-87% >98%(AR Coated)
Vickers hardness : >1.26 x 10^4 MPa/mm2
Strength of flexure : 140-200MPa
Transparent Ceramic Spinel Application
Transparent ceramic spinel is an attractive material for uses in a wide range of optical, electronic and structural applications including windows and lenses, which require excellent transmission from the visible through to the mid IR. Theoretical transmission is very uniform and approaches 87% between 0.3 to 5 microns. Transmission characteristics rival that of sapphire in the mid-wave IR, making it especially attractive for the ever-increasing performance requirements of current and next-generation IR imaging systems.
- Domes, optical window, lens, prism.
- LED, ceramic substrate material for electronic packaging.
- Valve flap, valve seat, a water-jet cutting flow-shaper, a nozzle for process fluids.
- High-pressure arc lamp and lens, safety goggles.
Transparent Ceramic Spinel Specifications
Dome : Max Φ255×8 mm;
Other spec. upon request.