The processing problems associated with boron carbide and the limitations of its mechanical properties can be significantly reduced when a metal phase (e.g., aluminum) is added. Lower densification temperatures and higher fracture toughness will result. Based on fundamental capillarity thermodynamics, reaction thermodynamics, and densification kinetics, we have established reliable criteria for fabricating B4C-AI particulate composites. Because chemical reactions cannot be eliminated, it is necessary to process B4C-AI by rapidly heating to near 1200°C (to ensure wetting) and subsequently heat-treating below 1200°C (for microstructural development).
Problems associated with manufacturing Si,N,/SiCwhisker composites have been overcome by developing selfreinforced Si,N, with elongated P-Si,N, grains formed in situ from oxynitride glass. This Si,N,-Y,O,-MgO-SO,-CaO-based material has a flexure strength >lo00 MPa and fracture toughness >8 M P a -d 2 . The optimum combination of mechanical properties has been obtained with Y,O,:MgO ratios ranging from 3:l to 1:2, CaO contents ranging from 0.1 to 0.5 wt%, and Si,N, contents between 90 and 96 wt%.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.