Different types of silicon carbide

Silicon carbide ceramic materials have excellent resistance, thermal conductivity, oxidation resistance and outstanding high-temperature mechanical properties. They are widely used in various fields such as optics, energy and environmental protection, chemical machinery, semiconductors, and defense industries.

Silicon carbide (SiC) possesses excellent optical performance. Compared to materials such as quartz glass, microcrystalline glass, and metals, it has moderate density, high elastic modulus, high dimensional stability, low coefficient of thermal expansion, and strong radiation stability. These characteristics make it one of the commonly used materials for manufacturing optical mirrors and optical systems.

The highly covalent nature of silicon carbide and its extremely low diffusion coefficient make it difficult to achieve sintering densification. Therefore, various sintering preparation technologies for silicon carbide have been developed. Currently, the main industrial production methods for silicon carbide ceramic materials include reaction bonding, chemical vapor deposition, and hot isostatic pressing.

Reaction Bonded Silicon Carbide (RB-SiC): This process involves the infiltration of a porous carbon structure with molten silicon, which reacts with carbon to form silicon carbide. The reaction occurs at high temperatures, typically above 1500°C. RB-SiC can produce products with complex shapes and precise dimensions. Modified RB-SiC can meet the requirements for manufacturing high-precision optical mirrors.

Chemical Vapor Deposition Silicon Carbide (CVD SiC): In CVD SiC, a gaseous mixture containing silicon and carbon precursors is introduced into a reactor chamber. The precursors decompose and react on the substrate surface at high temperatures (typically around 1200-1600°C) to form a solid silicon carbide layer. The deposition process can be performed under atmospheric pressure or in a low-pressure environment. CVD SiC creates high-purity silicon carbide with excellent thermal conductivity. However, this process has the highest production cost and may result in high residual stress.

Hot Isostatic Pressing (HIP): HIP, also known as hot pressing, is a process that uses an inert high-pressure gas (such as argon) to facilitate the densification sintering of materials. The silicon carbide powder compact is sealed in a glass or metal container under vacuum. During the HIP process, the sample is heated to the sintering temperature while being subjected to an initial gas pressure of several megapascals by a compressor. As the heating proceeds, the gas pressure gradually increases up to 200 MPa, eliminating internal voids in the material to achieve densification using isostatic gas pressure. HIP is commonly used for densification of ceramics, metals, and composite materials to enhance their mechanical properties, eliminate defects, and achieve uniformity in microstructure.

MG Optics has years experience in manufacturing RB-SiC. We have advanced gel injection molding technology, which enables the preparation of various complex-shaped, hollow, lightweight ceramic preforms. Meanwhile MG Optics develop the whole process of manufacturing and polishing large aperture lightweight SiC aspheric mirrrors primarily applied in satellite telescopes and scanning mirror systems.
We have completed one set of 720mm aperture large SiC aspheric mirrors, with the final surface accuracy better than 1/60 RMS.

Send us your drawings or specifications , we will prepare a quote for you.

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