High Strength Spinel Sensor Windows

The Optical Ceramics Division of TA & T proposes to develop fine grained, high strength transparent magnesium aluminate (Spinel) windows for Navy airborne and ship electro-optical sensor hardware A systematic approach based on the latest scientific principles for selecting nano-particulate additives (dopants) that promote grain boundary pinning and retard grain growth is outlined. The approach builds on (1) the recent results of high resolution aberration corrected transmission electron microscopy of doped alumina and the relationship it established between processing conditions and grain boundary atomic structure and (2) the processing know how that TA & T has developed in producing transparent spinel optical windows as large as 11"x 18"and transparent armor windows as large as 15"x 20". Feedback from optical measurements and microstructural characterization will be used to focus iterative experiments on the nano-particulate dopants, dopant concentrations and processing conditions that appear most promising. Microhardness, fracture toughness, biaxial flexure (tensile) strength and total forward integrated scatter measurements will be made on selected nano-composite spinel samples in order to develop correlations that lead to optimization of processing conditions for scale-up to large size windows in Phase 2.