SBIR-STTR Award

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.

This Small Business Innovation Research (SBIR) Phase II project enables an innovative low cost approach to reaction bonded silicon carbide (RBSC). RBSC is a preferred material for mechanical seals, which are critical, costly components in many major manufacturing lines. The high cost of RBSC limits its use in favor of cheaper, shorter lived materials. A microwave heating process, combined with lower cost raw materials addresses RBSC cost issues. Phase I research identified a process range for producing RBSC with flexural strength above the industry average. The Phase II research will yield reliably high strength RBSC. The key objective for Phase II is optimization of all-carbon preform formation, and microwave infiltration methods, to fabricate prototype mechanical seals for industrial evaluation. The new RBSC will be characterized according to mechanical seal industry approval specifications. Innovative forming processes including 3D printing will be studied for the ability to quickly form complex, custom, near net preforms for infiltration. The anticipated result is a commercially ready, lightweight, high strength RBSC that will be preferred for existing and new applications. The broader impact/commercial potential of this project will include significant cost reductions for wear resistant applications. A low-cost, superior performance mechanical seal will improve efficiency, with fewer costly production shut-downs due to pump failures. RBSC provides a longer overall lifetime than tungsten carbide, graphite, or alumina parts, further reducing life cycle costs. Mechanical seals cost on average $750 per inch of diameter, ranging up to 15" across. This research will enable a 50% reduction in RBSC cost, developing a viable, high performance product, along with market demand. Recent consolidation of major silicon carbide suppliers provides an opening in the market to support a new, independent RBSC source. The RBSC process uses a greener microwave process, with time, energy and greenhouse gas reductions of 50 to 80%. The commercial demonstration of microwave RBSC product will provide a needed boost to encourage other manufacturers to uptake cleaner, efficient microwave processing. The project also supports Science Technology Engineering Mathematics (STEM) education through high school projects and at least four undergraduate engineering co-op students