This paper describes recenl advances on the development of low cost, high strength, transparent magnesium aluminum spinel windows and domes for armored vehicles, aircrafts, and missiles. The novel spinel material exhibits high optical and IR transparency in the 0.3 - 5.5 mu m wavelength, is very resistant to abrasion, with density higher than 99.95 percent of theoretical, with very fine and uniform grain size, and flexural strength of 300 MPa. Its mechanical properties are several times greater than that of glass and make it a leading candidate for use as a transparent armor and window material. The novel spinel described in this paper is superior lo conventional available spinel materials. Improved performance derives from the use of an advanced transient sintering aid technology that leaves no traces in the final product, and flexible green forming and densification achieved by high temperature sintering of high purity spinel powder. Unlike previous efforts to produce transparent spinel by conventional mixing or granulation during powder preparation, resulting in inhomogeneous spinel with exaggerated grain growth and hazy and/or opaque regions, the novel powder preparation technology ensures a previously unattainable uniformity in sintering aid dispersion that allows the densificalion of highly transparent and uniform spinel windows. The production of discs, lenses, curved windshields, domes, and rectangular windows larger than 12"xl6" in large numbers, exhibiting no optical defects, high degree of transparency, using conventional ceramic powder compaction technology or net shape green body formation is described. Spinel transmission and mechanical properties are presented.
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