Silicon carbide fibers matrix composites

Silicon carbide (SiC) matrix composites have been fabricated by chemical vapor infiltration (CVl), polymer impregnation and pyrolysis (PIP), and reaction sintering (RS). The RS process can be recognized as an attractive technique, because it offers a high density and good thermal conductivity, compared to those of CVl and PIP process. In general, the fabrication of fiber reinforced SiC matrix composites by reaction sintering involves melt infiltration (Ml) or liquid silicon infiltration (LSI). However, the fabrication of continuous fiber reinforced SiC matrix composites by RS focused in melt infiltration (Ml) such as liquid silicon infiltration (LSl) Vapor silicon infiltration was rarely used for SiC matrix composites. 

E. Tani, K. Shobu, and K. Kishi, Two-dimensional-woven-carbon-fiber-reinforced Silicon Carbide/Carbon Matrix Composites Produced by Reaction Bonding, J. Am. Ceram. Soc., 82 [5] 1355-57(1999). 

TABLE 5.9 Properties of Enhanced Silicon Carbide Fiber-Reinforced Silicon Carbide Ceramic Matrix Composites Source Allied SignaQ... 

The high-temperature stability of SiC-based ceramics is well-known, and therefore its composite materials have been investigated for application to high-tem-perature structural materials [19-21]. However, well-known SiC-based fibers and matrix-materials stained with alkali salt are easily oxidized at high temperatures in air [22]. This would be a serious problem when these materials are used near the ocean or in a combustion gas containing alkali elements. In particular, a silicon carbide fiber containing boron (a well-known sintering aid for SiC) over 1 wt% was extensively oxidized under the above condition. In this... 

Recent research has explored a wide variety of filler-matrix combinations for ceramic composites. For example, scientists at the Japan Atomic Energy Research Institute have been studying a composite made of silicon carbide fibers embedded in a silicon carbide matrix for use in high-temperature applications, such as spacecraft components and nuclear fusion facilities. Other composites that have been tested include silicon nitride reinforcements embedded in silicon carbide matrix, carbon fibers in boron nitride matrix, silicon nitride in boron nitride, and silicon nitride in titanium nitride. Researchers are also testing other, less common filler and matrix materials in the development of new composites. These include titanium carbide (TiC), titanium boride (TiB2), chromium boride (CrB), zirconium oxide (Zr02), and lanthanum phosphate (LaP04). 

R. F. Cooper and K. Chyung, Structure and Chemistry of Fibre-Matrix Interfaces in Silicon Carbide Fiber-Reinforced Glass-Ceramic Composites An Electron Microscopy Study, J. Mater. Sci., 22, 3148-3160 (1987). 

J. J. Brennan and K. M. Prewo, Silicon carbide fiber reinforced glass-ceramic matrix composites exhibiting high strength and toughness. J. Mater. Sci. 17, 2371-2383 (1982). 

Owing to their outstanding properties, silicon carbide fiber reinforced silicon carbide matrix (SiC/SiC) composites have been specified in several applications especially in recent fusion power plant design studies and have been considered internationally in several power plant studies. These characteristics include high-temperature properties and stability, corrosion resistance, as well as low induced radioactivity, quick decay of activity, low afterheat, low atomic number, good fracture resistance and more. 

Prewo, K.M., and J.J. Brennan. 1980. High-strength silicon carbide fiber reinforced glass-matrix composites. Journal of Materials Science 15 463 68. ... 

Hi-Nicalon/Celsian composites are stable up to use temperature of 1100°C in oxidizing environments and degrade at higher temperatures due to the instability of polymer-derived fibers. The stability of Celsian matrix composites may be extended to higher temperatures by more uniform and stable interface coating(s) and by reinforcement with more advanced silicon carbide fiber (Sylramic) for applications as hot components (combustion liner, air foil, nozzle, etc.) in turbine engines. 

N. P. Bansal, Method of Producing a Silicon Carbide Fiber Reinforced Strontium Aluminosilicate Glass-Ceramic Matrix Composite, U. S. Patent 5,389,321 February 14, 1995. 

Ceramic matrix composites are under active consideration for low-observable military applications, where dielectric properties are a key performance factor. The frequency range of interest is the 8-12 GHz microwave range. The composite system must have low electrical conductivity. The SiOC-Nextel 312 system meets that requirement (as compared to ceramic composites made with conductive silicon carbide fibers). 

X. Wu and J. W. Holmes, Tensile Creep and Creep-Strain Recovery Behaviour of Silicon Carbide Fiber/Calcium Aluminosilicate Matrix Ceramic Composites, J. Am. Cerartu Soc. 76, 2695-2700 (1993). 

Since the oxidation resistance of SiC is much better than that of carbon, SiC/SiC composites have been developed for aerospace application such as propulsion and high velocity systems. Similar to carbon/carbon composites, the SiC/SiC continuous fiber composites consist of a fiber architecture made of silicon car-hide fibers in a matrix of silicon carbide. The matrix is usually produced by CVl or preceramic polymer impregnation and pyrolysis. 

Coatings were applied to bend bars made from various commercial types of silicon nitride or silicon carbide, fiber-reinforced, silicon carbide matrix composites. In some cases the silicon nitride bend bars had as-processed surfaces, but in most cases the surfaces were machined and ground. The surfaces of the SiCf/SiCn, bend bars were cleaned prior to coating, but no other treatment was applied to them. 

R.F. Cooper, K. Chyung Structure and chemistry of fiber-matrix interfaces in silicon carbide fiber-reinforced glass-ceramic composites An electron microscopy study , J. Mat. Sci. 22, 3148-3160 (1987)... 

Composites are usually classified by the type of material used for the matrix. The four primary categories of composites are polymer matrix composites (PMCs), metal matrix composites (MMCs), ceramic matrix composites (CMCs), and carbon matrix composites (CAMCs). The last category, CAMCs, includes carbon/carbon composites (CCCs), which consist of carbon matrices reinforced with carbon fibers. For decades, CCCs were the only significant type of CAMC. However, there are now other types of composites utilizing a carbon matrix. Notable among these is silicon carbide fiber-reinforced carbon, which is being used in military aircraft gas turbine engine components. 

Aerospace applications of ceramic matrix composites to date have been limited. Perhaps the most significant are the aircraft engine flaps used on a French fighter. There are two types. Both use silicon carbide matrices. One is reinforced with carbon fibers, and the other with a multifllament silicon carbide fiber. Another application is a missile diverter thruster made of carbon fiber-reinforced silicon carbide. Again, the process used to make this part is CVI. The Space Shuttle Orbiter thermal protection system (TPS) makes extensive use of tiles composed of a three-dimensional network of discontinuous oxide fibers with silicate surface layers. While there is no continuous matrix for most of the tile, the surface region is a form of CMC. In a sense, this can be considered to be a type of functionally graded material. 

Table 5.9 presents room-temperature properties of one of these materials, enhanced silicon carbide fiber-reinforced silicon carbide, which has a SiC matrix containing proprietary additives that improve oxidation resistance. The composite is reinforced with a plain weave fabric woven from CG Nicalon silicon carbide fibers. 

SILICON CARBIDE FIBERS. There are two forms of SiC fibers, neither of which is available commercially. One consists of a pyrolytic deposit (CVD) of SiC on an electrically conductive, usually carbon, continuous filament. Fiber diameter is about 140 fim. This technology has been used to make filaments with both graded and layered structures, including surface layers of carbon which provide a toughness-enhancing parting layer in composites having a brittle matrix (sdicon nitride, for example). 

---