Rapid Near Net Shape Processing of Transparent ALON Windows and Domes

Infrared transparent domes for missiles require a multi-mode system of electromagnetic guidance. In recent-years efforts have been concentrated on maximizing the resolution of such detector materials and provide sensor guidance systems between the W. visible and the mid IR ranges. With a higher thermal shock resistance than any available optical material, sapphire is the material of choice, but displays optical anisotropy, which leads to significant scatter. Aluminum oxy-nitride based optical materials are its ideal replacement, since it has a cubic symmetry, which results in isotropic properties and displays ~>80% in line transmission in the visible and near infrared regions (0.3um - 5.0um). Unfortunately, AlON suffers from compositional inhomogeneity due to incomplete reactive sintering, and unstable mechanical properties resulting from catastrophic grain growth owing to high sintering times (20-100 hours). In this Phase I effort MMI proposes to synthesize gamnsa-AlON and consolidate near net shapes to full densities in less than 5 minutes. The consolidated part will further be polished to a roughness of <lnm. AlONobtained by the proposed method can be used in a variety of optical devices such as windows for high power laser systems, maximum efficiency detectors, windows and domes for aircraft's and missiles for high transmission across a broad band of the electromagnetic spectrum (0.2um - 5.5um).