Akihito Fujii

Diamond-ZnS composite infrared window

Rain erosion is a critical problem in the use of conventional Zinc Sulfides as infrared window and dome. In this study, the diamond-ZnS composite, which dispersed diamond particles into a zinc sulfide matrix, was fabricated for improved durability against rain erosion. It was found that mechanical properties, such as hardness, fracture strength and Young modulus of the diamond-ZnS composite improved with the increase in diamond particles. Furthermore the diamonds-ZnS composite consisted of two layers, a diamond dispersed layer and a pure ZnS layer. They have a 280-350kg/mm2 hardness, which is 1.5 times higher than conventional ZnS, while maintaining about 55~70% in average transmittance at the wavelength of 10micrometers bands.

Nondoped Y203 for 3-5μm IR transmission

Non-doped yttria (Y203) ceramics for 3-5Mm JR transmission have been experimentally made by a powder processing technique. The optical, mechanical, and thermal properties have been measured. Some samples showed fairly good transmittance properties. In addition, decreasing the grain size of yttria proved effective in improving the flexural strength.

Polycrystal GaAs infrared windows

There are difficult points such as lowering of the detection or recognition capability of some targets by aerodynamic heating with speedup of the aircraft and missile and restriction of the operation by the raindrop in rainfall time on the conventional ZnS infrared window application used for missile seeker and FLIR equipment. Therefore, in this study, the promising polycrystal GaAs which has low infrared radiations in high temperature was produced using HB method (Horizontal Boat method) and VG method (Vertical Boat method) as a new infrared window material expected the durability for rain erosion. As the result, 70mm2 windows by the HB method and 100mm diameter windows by VB method were realized. Moreover, their optical characteristics, mechanical properties and thermal shock durabilities were measured and they were confirmed to be about 56% in average transmittance in the wavelength of 10micrometers bands, 530~630kg/mm2 in their hardness and thermostable at 300 degree(s)C.

Ceramics For 3-5 Micron IR Transmission

Magnesium fluoride(MgF2) and Magnesium aluminate spinel(MgA1204) ceramics for 3-5 micron IR transmission have been developed by a powder processing technique. Their optical, physical, mechanical, and thermal properties have been measured and compared with each other. The transmittance and flexural strength related with microstructures are studied.