Fabrication of liquid phase sintered SiC materials and their characterization

Comparative analysis of oxidation methods of reaction-sintered silicon carbide for optimization of oxidation-assisted polishing

Combination of the oxidation of reaction-sintered silicon carbide (RS-SiC) and the polishing of the oxide is an effective way of machining RS-SiC. In this study, anodic oxidation, thermal oxidation, and plasma oxidation were respectively conducted to obtain oxides on RS-SiC surfaces. By performing scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDX) analysis and scanning white light interferometry (SWLI) measurement, the oxidation behavior of these oxidation methods was compared. Through ceria slurry polishing, the polishing properties of the oxides were evaluated. Analysis of the oxygen element on polished surfaces by SEM-EDX was conducted to evaluate the remaining oxide. By analyzing the three oxidation methods with corresponding polishing process on the basis of schematic diagrams, suitable application conditions for these methods were clarified. Anodic oxidation with simultaneous polishing is suitable for the rapid figuring of RS-SiC with a high material removal rate; polishing of a thermally oxidized surface is suitable for machining RS-SiC mirrors with complex shapes; combination of plasma oxidation and polishing is suitable for the fine finishing of RS-SiC with excellent surface roughness. These oxidation methods are expected to improve the machining of RS-SiC substrates and promote the application of RS-SiC products in the fields of optics, molds, and ceramics.

Ultrasmooth reaction-sintered silicon carbide surface resulting from combination of thermal oxidation and ceria slurry polishing

An ultrasmooth reaction-sintered silicon carbide surface with an rms roughness of 0.424 nm is obtained after thermal oxidation for 30 min followed by ceria slurry polishing for 30 min. By SEM-EDX analysis, we investigated the thermal oxidation behavior of RS-SiC, in which the main components are Si and SiC. As the oxidation rate is higher in the area with defects, there are no scratches or cracks on the surface after oxidation. However, a bumpy structure is formed after oxidation because the oxidation rates of Si and SiC differ. Through a theoretical analysis of thermal oxidation using the Deal-Grove model and the removal of the oxide layer by ceria slurry polishing in accordance with the Preston equation, a model for obtaining an ultrasmooth surface is proposed and the optimal processing conditions are presented.