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Enhancement and control of carrier lifetimes in p-type 4H-SiC have been investigated. In this study, thermal oxidation and carbon ion implantation methods, both of which are effective for lifetime enhancement in n-type SiC, were attempted on 147-μm thick p-type 4H-SiC epilayers. Effects of surface passivation on carrier lifetimes were also investigated. The carrier lifetimes in p-type SiC could be enhanced from 0.9 μs (as-grown) to 2.6 μs by either thermal oxidation or carbon implantation and subsequent Ar annealing, although the improvement effect for the p-type epilayers was smaller than that for the n-type epilayers. After the lifetime enhancement, electron irradiation was performed to control the carrier lifetime. The distribution of carrier lifetimes in each irradiated region was rather uniform, along with successful lifetime control in the p-type epilayer in the range from 0.1 to 1.6 μs. [ABSTRACT FROM AUTHOR]

The authors report a significant enhancement in the thermal conductivity of a conventional carbon fiber/phenolic resin composite system when adding highly crystalline multiwalled carbon nanotubes. They demonstrate that 7 wt % of carbon nanotubes dispersed homogeneously in a phenolic resin acted as an effective thermal bridge between adjacent carbon fibers and resulted in an enhancement of the thermal conductivity (e.g., from 250 to 393 W/m K). These results indicate that highly crystalline carbon nanotubes can be used as a multifunctional filler to enhance simultaneously the mechanical and thermal properties of the carbon fiber/phenolic resin composites. [ABSTRACT FROM AUTHOR]

A comparison of the microtexture and structure of the low temperature heat-treated polyparaphenylene (PPP)-based carbons which are promising for the Li ion battery has been performed using high-resolution transmission electron microscopy and electron energy loss spectroscopy. It is found that the PPP-based carbon prepared by Kovacic method remains in suitable microtexture for high Li storage over a wider temperature range relative to that obtained by Yamamoto method. This characteristic of the Kovacic PPP-based carbon could lead to a more controlled microtexture for obtaining a higher Li storage capacity for Li ion battery applications. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]