Treatment to Increase the Strength of Sapphire Windows and Domes

Aspen Systems proposes to develop a novel process to increase the strength of sapphire at elevated temperatures. The resulting increase will alleviate strength losses in high performance IR seeker systems such as THAAD and Standard Block IV. The Aspen process will uniformly implant silicon atoms within the sapphire window material. This will in turn pin the crystal lattice resulting in a structure more resistant to rhombohedral twinning and thermal shock failure. Preliminary testing conducted on sapphire treated with our novel process have demonstrated that our process can be applied to high purity sapphire with no adverse effects on the transmittance in the Midwave (3-5 um) region. The Phase I effort will demonstrate proof-of-principal that our process can increase the tensile strength of sapphire without degrading its optical properties. In Phase II of the program we will optimize our process to maximize the tensile strength of sapphire and to characterize the material properties of the processed sapphire. The process method used in Phase I and Phase II can readily be scaled to meet both military ands civilian needs. The process developed in the proposed program will provide a low cost method to strengthen sapphire materials Strengthening sapphire will expand the type and number of applications where sapphire can replace current window materials. Sapphire is chemically inert and can out perform silica based products and processes.