Facile Fabrication of SiC Matrix Composites Using Novel Preceramic Polymers

Abstract

Starfire Systems, Inc. offers a family of unique, patented, polysilylene-methylene polymers for the manufacture of advanced silicon carbide (SiC) ceramic materials with unequalled performance, safety, environmental and cost advantages. The resultant advanced ceramic materials provide superior resistance to wear, corrosion and elevated temperatures, when compared to many other materials. These new precursors greatly simplify the formation of SiC ceramic materials, making possible new applications in aerospace, power materials, microelectronics, and other 21 s t century industries. Typical applications are for increasing energy efficiency, pollution control, improved capital effectiveness and increased productivity in many industrial sectors. Starfire has performed experimental research on the composites generated using Starfire Precursors. These composites have been formed via Infiltration Process (PIP), Ceramic Molding operation, Paint On process, and Chemical Vapor Deposition/Infiltration (CVD/I). These four applications are discussed.First, our precursor Polymer is used in the Infiltration Process (PIP) to infiltrate fibrous performs and form a SiC matrix. The ceramic matrix is formed by a pyrolysis at 850°C. Typically the PIP process is repeated a number of times as each step results in a higher density and lower porosity. Second, our SP-Matrix can be mixed with powders and used to bond SiC pieces to SiC pieces and other substrates. It acts as a high temperature SiC glue. This enables the forming of complex structures with joints of silicon carbide. Third, we have manufactured a SiC ceramic molding compound which can be formed into a wide variety of shapes. This moldable compound yields a very hard, dense part after just one pyrolysis cycle. And fourth, we have used our SP-4000 and SP-2000 low molecular weight precursors for CVD and CVI reactions to yield SiC coated and SiC matrix infiltrated parts. The process is done at a low temperature (850°C) and under vacuum/inert gas atmosphere. The CVD coatings are very dense and uniform in thickness. The CVI process infiltrates a variety of fiber tow thicknesses and can be tailored to meet density and porosity needs. All of the above precursors have been demonstrated to adhere (as SiC) to a variety of substrates including graphite, silicon carbide, silica, alumina, diamond, zirconia, and some refractory metals. Typical SiC yields from the precursor at high temperatures are 85-90% by wt. These preceramic polymers offer SiC manufacturers a greater design freedom than most other methods of SiC processing. The temperatures of application are much lower (typically 850°C), the process equipment required is much simpler and more cost effective, and these precursors have much lower environmental, personnel and usage hazards. These polymers are currently offered as SiC precursors for the industrial, academic, and governmental markets around the world.