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  • 1
    Digitale Medien
    Digitale Medien
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), S. 0 
    ISSN: 1551-2916
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Maschinenbau , Physik
    Notizen: Crystalline mullite was deposited by chemical vapor deposition (CVD) onto SiC/SiC composites overlaid with CVD SiC. Specimens were exposed to isothermal oxidation tests in high-pressure air + H2O at 1200°C. Unprotected CVD SiC formed silica scales with a dense amorphous inner layer and a thick, porous, outer layer of cristobalite. Thin coatings (∼2 μm) of dense CVD mullite effectively suppressed the rapid oxidation of CVD SiC. No microstructural evidence of mullite volatility was observed under these temperature, pressure, and low-flow-rate conditions. Results of this preliminary study indicate that dense, crystalline, high-purity CVD mullite is stable and protective in low-velocity, high-pressure, moisture-containing environments.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Bingley : Emerald
    Environmental management and health 10 (1999), S. 282-289 
    ISSN: 0956-6163
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Medizin , Wirtschaftswissenschaften
    Notizen: Life-cycle analysis (LCA) provides a general framework for assessing and summarizing all of the information important to a decision. LCA has been used to analyze the desirability of replacing lead (Pb) with a composite of tungsten (W) and tin (Sn) in projectile slugs used in small arms ammunition at US Department of Energy (DOE) training facilities for security personnel. The analysis includes consideration of costs, performance, environmental and human health impacts, availability of raw materials, and stakeholder acceptance. Projectiles developed by researchers at Oak Ridge National Laboratory (ORNL) using a composite of tungsten and tin are shown to perform as well as, or better than, those fabricated using lead. A cost analysis shows that tungsten-tin is less costly to use than lead, since, for the current number of rounds used annually, the higher tungsten-tin purchase price is small compared with higher maintenance costs associated with lead. The tungsten-tin composite presents a much smaller potential for adverse human health and environmental impacts than lead. Only a small fraction of the world's tungsten production occurs in the USA, however, and market-economy countries account for only around 15 per cent of world tungsten production. Concludes that stakeholders would prefer tungsten-tin on the basis of total cost, performance, reduced environmental impact and lower human toxicity. However, lead is preferable on the basis of material availability. Life cycle analysis clearly shows that advantages outweigh disadvantages in replacing lead with tungsten-tin in small-caliber projectiles at DOE training facilities. Concerns about the availability of raw tungsten are mitigated by the ease of converting back to lead (if necessary) and the recyclability of tungsten-tin rounds.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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