• Journal of the Korean institute of surface engineering
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• v.41 no.5
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• pp.240-244
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• 2008

Composite plating is a method of co-deposition of plating layer with metallic and/or non-metallic particles to improve the plating layer properties such as high corrosion resistance and photolysis of organic compounds. The properties of nickel-ceramic composite plating are significantly depend on the surface characteristics of co-deposited particles as well as the quantity in electrolyte. In this study, Ni-$TiO_2$ composite coating layer was produced by electrodeposition technique from non-aqueous eletrolyte and its surface characteristics as well as photolytic properties were investigated. The amounts of immobilized $TiO_2$ particles increased with increasing the initial $TiO_2$ particles contents in the bath. Samples electroplated with the current density of $0.5\;A/dm^2$ showed the significantly improved homogeneous $TiO_2$ particles distribution. The corrosion resistance of Ni-$TiO_2$ composite coating layer also improved with increaing the amounts of $TiO_2$ particles. Etched sample showed about 10% increased photolytic rate of organic matter compare to that of the non-etched.

• Korean Journal of Optics and Photonics
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• v.33 no.2
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• pp.74-83
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• 2022

The entire process, from the raw material to the final system qualification test, has been developed to fabricate a large-diameter, lightweight reflective-telescope system for a satellite observation. The telescope with 3 anastigmatic mirrors has an aperture of 700 mm and a total mass of 66 kg. We baked a silicon carbide substrate body from a carbon preform using a reaction sintering method, and tested the structural and chemical properties, surface conditions, and crystal structure of the body. We developed the polishing and coating methods considering the mechanical and chemical properties of the silicon carbide (SiC) body, and we utilized a chemical-vapor-deposition method to deposit a dense SiC thin film more than 170 ㎛ thick on the mirror's surface, to preserve a highly reflective surface with excellent optical performance. After we made the SiC mirrors, we measured the wave-front error for various optical fields by assembling and aligning three mirrors and support structures. We conducted major space-environment tests for the components and final assembly by temperature-cycling tests and vibration-shock tests, in accordance with the qualifications for the space and launch environment. We confirmed that the final telescope achieves all of the target performance criteria.