Resins, boron carbides

Organic precursors can be used both polycarbosilane and a small amount of phenolic resin, giving CSi and carbon by in situ pyrolysis the resulting boron-carbide ceramies have high density (> 92 %) and contain no free carbon and a small amount of SiC( 5wt%) . 

The addition of free graphite yields fine-grained compounds near the theoretical density (94-100 %) . Carbon is better added by the in-situ pyrolysis of a phenolfor-maldehyde resin (i 9 wt Pressure-less sintering of boron-carbide is now... 

Boron has been included as a neutron absorber in various materials in addition to concrete. For example, borated graphite, a mixture of elemental boron and graphite, has been used in fast-reactor shields. Boral, consisting of boron carbide (B4C) and aluminum, and epoxy resins and resin-impregnated wood laminates incorporating boron have been used for local shielding purposes. Boron has also been added to steel for shield structures to reduce secondary gamma-ray production. In special situations, where a shield has consisted of a heavy metal and water, it has been beneficial to add a soluble boron compound to the water. 

The only technically important sintering additive for boron carbide is carbon, as discovered almost simultaneously by Schwetz and Vogt [189], Henney and Jones [190], and Suzuki et al. [191], which today allows the routine production of dense parts. An amount ranging from 1 to 6 mass-% is sufficient to obtain almost theoretical density. Schwetz and Grellner [192] added phenolic resin (corresponding to 1-3 mass-% C) to a submicron B4C powder and obtained >98% density at 2150°C. The resins are pyrolized at temperatures up to 1000°C and they leave a... 

Hydrochloric acid Succinic acid neutralizer, preboiler system Methoxypropylamine neutralizer, urea-formaldehyde resins Ammonium biborate neutron absorber Boron carbide Samarium oxide neutron absorber, laser crystals Samarium... 

Silicones pure silicon, fumed silica, silanes, silicone resins and rubbers Materials advanced ceramics, boron compounds, surface treatments and silicon carbide. 

The common commercially available fibers used in composites are fiberglass, graphite (carbon), aramid, polyethylene, boron, silicon carbide, and other ceramics such as silicon nitride, alumina, and alumina silica. Many matrix choices are available, both thermosetting and thermoplastic. Each type has an impact on the processing technique, physical properties, and environmental resistance of the finished composite. The most common resin matrices include polyester, vinyl esters, epoxy, bismaleimides, polyimides, cyanate ester, and triazine. 

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