Development of AIN IR Windows for Hypersonic Applications

Vortec proposes to improve the IR transparency, thermal shock resistance, and processing of AlN through the exploitation of the unique properties of nanocrystalline materials. We will construct test windows consisting of nanocrystalline AlN where the grain sizes are on the order of about 100 nm. The thermal conductivity of AlN is very large as compared to other materials currently used for IR window hypersonic flight applications. Improved optical properties and mechanical properties such as strength, ductility are expected so windows with higher thermal shock resistance, greater IR transmittance and lower birefringence are expected as the grain size of the AlN is reduced to below 100 nm. The production costs for polycrystalline parts are a fraction of that for single crystal ones. Therefore through the combination of these factors and Vortec's low-cost nanopowder production process, it is anticipated that a high performance AlN window can be manufactured at low cost. During Phase I, the feasibility of producing IR windows using nanocrystalline AlN will be demonstrated and the windows characteized. The work performed will include the adaptation Vortec's process to the production of AlN, demonstration of improved processing, and the development of test windows demonstrating improved optical and thermal characteristics.