Zirconium carbide matrix

More recently, ceramic composite materials have been described that incorporate zirconium diboride platelet reinforcements in a zirconium carbide matrix [34, 35], These materials are prepared by the directed reaction of molten zirconium with boron carbide (B4C) to form a ceramic material composed of zirconium diboride platelets in a zirconium carbide matrix with a controlled amount of residual zirconium metal. 

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). 

Because the details of processing in each class of CMCs (e.g., oxide, carbide, or nitride matrix) are slightly different, the appropriate thermochemical approach for each class may also be different. For example, in the formation of alumina matrix materials by directed metal oxidation, the alumina product grows from a molten aluminum alloy by reaction with an oxygen-containing gas phase. On the other hand, in the formation of platlet-reinforced zirconium carbide, the gas phase is not involved in the reaction at all, being inert to the reactants and products. Thus, a general approach to deal with the myriad of possible products formed by the... 

The fibers typically consist of carbon (C), silicon carbide (SiC), alumina (AI2O3), or mullite (Al203-Si02). For the matrix components, alumina, zirconium oxide, and silicon carbide are most commonly used. The terminology of CMC usually follows the principle t3q>e of fiber/t3q>e of matrix. C/SiC stands for a carbon-fiber-remforced silicon carbide. Today, the most important CMCs are C/C, C/C-SiC, C/SiC, and SiC/SiC. In some cases, the term is preceded with the abbreviation of the manufacturing process. 

Fuel element Outer annular region (27 elements) pyrolytic carbon-coated U-235/ zirconium monocarbide spherical particles consolidated in graphite matrix, to form inserts, 30 per fuel rod. Inner central region (10 elements) pyrolytic carbon and silicon carbide-coated U-235 thorium carbide spherical particles. Zr U-235 ratio 8 1 Th U-235 ratio 10 1... 

Song et al. (2002) suggested using a mixture of fine and coarse silicon carbide particles to improve electrolyte and gas management in the matrix. Similar results can be obtained with a combination of silicon carbide and zirconium silicate particles (Neergat and Shukla, 2001). 

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