A Low-Cost Innovative Approach for the Fabrication of Net-Shape SiC Components for Mirror Substrate Applications

Beryllium, with its light weight and exceptional characteristics, has been the preferred material for different demanding applications including sensor mirrors. Beryllium, however, is now facing bigger challenges including growing health hazard concernsand the increasing production cost. It is expected that beryllium will not be available within the next seven years and a substitute material with matching characteristics is now needed. Based on a comprehensive review of many potential candidatematerials and their properties resulted in the selection of silicon carbide (SiC) as the new material of choice and best substitute for beryllium due to its superior mechanical and thermal properties as compared to other materials. Conventional processesfor the manufacturing of SiC, however, lack the capability for complex shape fabrication and tend to be expensive due to the processes involved and the extensive post machining.It is, therefore, proposed here to utilize POCO's chemical vapor reaction (CVR) process for the manufacturing of complex net-shape SiC parts with 18-20% porosity followed by an innovative approach to achieve full densification. In this proposal, thedensification approach is described in detail and supported with some preliminary results including strength and other physical and chemical properties. Poco has identified a number of benefits that will come from this effort.1. Elimination of health hazard issues caused by processing of beryllium2. Shorter fabrication leadtimes3. Reduced cost for manufacturing dense silicon carbide4. Increased capability for the fabrication of complex SiC shapes5. New opportunities for dense SiC where CVD SiC and hot-pressed SiC too expensive.6. This project will support Poco's commercialization effort for copnverted SiC products.