SBIR Phase I: Microwave Heating of Reaction-Bonded Silicon Carbide Ceramics

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This Small Business Innovation Research Phase I project addresses the need for lower cost ceramic materials, specifically for reaction-bonded silicon carbide (RBSC) products. RBSC is used in a multitude of applications ranging from kiln furniture to body armor inserts to ultra-high purity semiconductor components. Lowering costs would make ceramic materials available for more wide-spread use. Currently, these products are limited in applications due to the high costs associated with expensive raw materials and high-temperature processing requirements. This project addresses these issues though the use of low cost preform materials and an innovative thermal processing technique. In prior work, a new method for producing RBSC was developed, through liquid infiltration of molten silicon by direct microwave heating. This innovative process allows for complete infiltration of porous preforms using microwaves, without the need for a high vacuum environment. However, one of the persistent technical issues is the formation of undesirable silicon veins in the RBSC. This may be caused by in part by a significant exothermic reaction during the infiltration. The veins can detrimentally affect the physical properties of the final RBSC. The anticipated technical results of this work are to identify the origin of silicon vein formation, and to develop methods to mitigate this issue. The broader impact/commercial potential of this project is to lower the cost of RBSC ceramics, making them more economically viable in current applications, and increasing their use in previously unfeasible applications where RBSC could provide superior performance characteristics. The successful development of low-cost, higher strength, and higher purity RSBC would provide significant benefits to ceramic component manufacturers and end users. Some of the current applications for RBSC include kiln furniture and various burner parts for combustion. Areas targeted for expanded use are: wear resistant components (e.g., slip ring seals), body armor for soldiers, sand blasting nozzles, and diffusion components for the semiconductor industry. The semiconductor industry is of particular interest. As devices continue to get smaller, the purity of diffusion components is becoming a critical issue. The use of this RBSC for high-purity wafer carriers would be advantageous, as preforms in the green state can be heated and purified. Finally, this work will enhance scientific and technological understanding of high temperature exothermic reactions, explore methods to control exothermic rates of reaction, and quantify the energy benefit of microwave processing versus conventional methods.