14 December 1992 Advances in spinel optical quality, size/shape capacity, and applications
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Polycrystalline MgAl2O4 Spinel, transparent from two hundred nanometers to six microns, offers a unique combination of optical and physical properties. A superior dome and window material with respect to rain and particle erosion, solar radiation, high temperatures and humidity, it is resistant to attack by strong acids, alkali solutions, sea water and jet fuels. Residual microporosity from the powder process used for fabricating Spinel which previously limited the use of Spinel to thin wall thicknesses and small sizes, has been significantly reduced by advanced hot press and hot isostatic press (HIP) technology. It is now possible to manufacture high quality shallow domes up to seven inches in diameter with a two tenths inch thick wall thickness. Eight inch diameter flat windows have been produced for an advanced missile system. Proof of process near hemispherical 8 inch dome blanks have been fabricated. Recent measurements of refractive index, homogeneity, scatter and surface roughness are available for design purposes. Improvement in the optical quality and in size/shape capability along with several successful prototype tests demonstrate that Spinel is ready for inclusion in appropriate production systems.
© (1992) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Donald W. Roy, Gay G. Martin, "Advances in spinel optical quality, size/shape capacity, and applications", Proc. SPIE 1760, Window and Dome Technologies and Materials III, (14 December 1992); doi: 10.1117/12.130781; https://doi.org/10.1117/12.130781

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