Papers by Keyword: Sintered SiC

Abstract: Silicon carbide (SiC) materials have increasingly been needed in the wide range of industries, such as for structural components, automobile parts, space telescope, X-ray mirror, and next-generation semiconductors. However, SiC materials have difficulties in super-smooth finishing because of their hard and brittle characteristics. The authors have been investigating appropriate conditions on their finishing by fine-grinding with the unique grinding process called ELID (Electrolytic In-process Dressing) grinding method. The ELID grinding method has a stable grinding ability, so very detailed characteristics of their material-remove mechanisms were to be investigated. Surface analysis of each material has been discussed through the ELID, and this study proposes good finishing conditions for SiC. In this paper, the advantages of the applied fine-grinding are shown, and unique features on grinding characteristics of SiC through various grinding experimental parameters are described.

Abstract: Lightweight mirrors of SiC (Silicon Carbide) are currently used for numerous space telescopes. The most favorable characteristics of the material are high specific stiffness, high thermal conductivity and low thermal expansion (CTE). For large-scale SiC mirrors, however, the machining cost is very high using traditional polishing process. In this study, a large-scale SiC spherical mirror (φ360mm) was designed as reducing-weight structure with many open-back triangular cells. The ELID mirror grinding technique was conducted to finish the mirror. A unique jig composed of many hydrostatic actuators was developed for reducing the deformation resulted from the grinding force. By using an on-machine measurement system, the form error of the finished surface was measured. The surface roughness of the mirror was also examined with a mobile AFM. As result, a high quality mirror surface, which has form accuracy 0.8µm P-V and roughness of Ra 7.8nm, was achieved. This paper presents the experimental procedure and results.