Papers by Author: Y. Dai

Abstract: This article introduces a process for the growth of one-dimensional oxide nanomaterials that combines rheological phase reaction and hydrothermal self-assembling process. Fundamentals and practical approaches of hydrothermal self-assembling process and rheological phase reaction are briefly described. Particular attention is devoted to the rheological self-assembling for the growth of low dimensional oxide nanomaterials. Many examples are shown that the rheological self-assembling is an effective method to prepare one-dimensional nanomaterials, organic-inorganic hybrids and 1-D nanomaterial array for optical-electronic and electrochemical devices and catalysis. Morphologies, microstructures, properties, and application of one-dimensional oxide nanomaterials are reviewed.

Abstract: In ELID (Electrolytic In-process Dressing) operations, the setting of starting point is quite important for reducing waste of time and for achiving high quality surface. In this study, the authors proposed a new describing mode for ELID grinding. The oxide layer formed on the wheel surface was divided to four sub-layer: porous-layer, polishing-layer, grinding-layer and interface-layer. The influence of the oxide layer on material removal rates and surface properties was investigated. It was found that, olny the oxide layer with thickness less than 24'm has capability of material removal. In ELID grinding, optimal thickness of the oxide layer is about 8~9'm. And the oxide layer with thickness of 4~9'm is suitable for grinding.

Abstract: The high-strength reaction-sintered silicon carbide (RS-SiC) developed by TOSHIBA is one of the most excellent materials for large-scale space-borne optics. The bending strength of the high-strength RS-SiC is two times higher than other SiC ceramics. The purpose of this study is to investigate the ELID grinding properties of the high strength RS-SiC. Two types of metal bond diamond wheels (cup type and straight type) were used to grinding tests. The ground surface properties, such as roughness, subsurface damage and micro-step were made clear by measurement or observation. It was confirmed that, both the surface roughness and the depth of micro-step produced by cup-wheel were lower than those produced by straight-wheel. When a #20000 grit sized cup-wheel was used, a considerably high quality mirror surface (Ra<0.8nm) can be achived.

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.