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Patches for Repairing Ceramics and Ceramic Matrix Composites

Patches are simply pressed in place, then heated. Patches consisting mostly of ceramic fabrics impregnated with partially cured polymers and ceramic particles are being developed as means of repairing ceramics and ceramic-matrix composites (CMCs) that must withstand temperatures above the melting points of refractory metal alloys. These patches were conceived for use by space-suited, space-walking astronauts in repairing damaged space-shuttle leading edges: as such, these patches could be applied in the field, in relatively simple procedures, and with minimal requirements for specialized tools. These design characteristics also make the patches useful for repairing ceramics and CMCs in terrestrial settings.

Posted in: Materials, Briefs

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Improving Thermomechanical Properties of SiC/SiC Composites

A heat treatment increases thermal conductivity and increases creep resistance. Today, a major thrust toward improving the thermomechanical properties of engine components lies in the development of fiber-reinforced silicon carbide matrix composite materials, including SiC-fiber/SiC-matrix composites. These materials are lighter in weight and capable of withstanding higher temperatures, relative to state-of-the-art metallic alloys and oxide-matrix composites for which maximum use temperatures are in the vicinity of 1,100 °C. In addition, the toughness or damage tolerance of the SiC-matrix composites is significantly greater than that of unreinforced silicon-based monolithic ceramics.

Posted in: Materials, Briefs, TSP

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Lower-Conductivity Ceramic Materials for Thermal-Barrier Coatings

Thermal conductivities of certain pyrochlore oxides can be reduced by doping. Doped pyrochlore oxides of a type described below are under consideration as alternative materials for high temperature thermal barrier coatings (TBCs). In comparison with partially yttria stabilized zirconia (YSZ), which is the state of the art TBC material now in commercial use, these doped pyrochlore oxides exhibit lower thermal conductivities, which could be exploited to obtain the following advantages:

Posted in: Materials, Briefs, TSP

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