Ultrafine preceramic Si/C/N composite powders have been prepared from hexamethyldisilazane (HMDS) by laser-induced gas phase reaction, using a new kind of tworeaction-zone reactor which could efficiently increase laser efficiency and production yield compared with a one-reaction-zone reactor. The as-formed products were nanosized (50–80 nm), amorphous powders containing Si–C and Si–N bonds homogeneously mixed with some excess carbon. The production yield was in the range of 88–120 g/h. Changes of chemical composition and crystallization of the powders during heat treatment at 1350 and 1550 °C under nitrogen for 1 h were studied.

Well-ordered, pure-phase epitaxial films of FeO, Fe3O4, and γ–Fe2O3 were prepared on MgO(001) by oxygen-plasma-assisted MBE. The stoichiometries of these thin films were controlled by varying the growth rate and oxygen partial pressure. Selective growth of γ–Fe2O3 and α–Fe2O3 was achieved by controlling the growth conditions in conjunction with the choice of appropriate substrates. Growth of the iron oxide epitaxial films on MgO at ≥350 °C is accompanied by significant Mg outdiffusion. The FeO(001) film surface exhibits a (2 × 2) reconstruction, which is accompanied by a significant amount of Fe3+ in the surface region. Fe3O4 (001) has been found to reconstruct to a structure. γ–Fe23 (001) film surface is unreconstructed.

We describe the variation of structural and physical properties of mesocarbon microbeads, a potential anode material for rechargeable lithium batteries, as a function of heat-treatment temperature in the range 400–1100 °C. Scanning electron microscopy (SEM) studies indicated changes in the morphology of the mesocarbons with heat treatment. X-ray studies show that average crystallite size varies considerably with heat treatment. The d002 spacing decreases with increasing heat-treatment temperatures. The electronic conductivity of the mesocarbon microbeads also increases substantially with increasing heat-treatment temperature. Based on thermogravimetric analysis (TGA) and other measurements, we find that organic fractions volatilizes out of these carbons in two distinct stages. The observed weight loss correlates with the structural changes observed. We suggest that these observations are consistent with two types of hydrogenated fractions present in the “green” mesocarbons.

The structure of polyparaphenylene (PPP)-based carbons prepared by the Kovacic and Yamamoto methods heat-treated at 650–3000 °C have been characterized comparatively by using x-ray diffraction, SEM, TEM, and Raman spectroscopy. Both kinds of carbons indicate not typical but poor graphitizing behavior, especially for the case of PPP Yamamoto samples, and much less for PPP Kovacic samples, by heat treatment up to 3000 °C. The Kovacic-based samples heat-treated at 600–2400 °C have a more developed layer structure than that of Yamamoto-based samples. In contrast, for HTT's (heat-treatment temperature) more than about 2400 °C, PPP Yamamoto-based carbons exhibit a more developed crystallite structure than PPP Kovacic-based carbons. At a given HTT, PPP Kovacic-based carbons have a much more quinoid-like structure and graphene-type structure than PPP Yamamoto-based carbons, as indicated by the carbon yield and Raman scattering measurements. It is suggested that the detailed structure of the starting polymers influences the texture as well as the microstructure of resultant carbons even though both are obtained from the same kinds of precursors. These microstructures also largely influence the anode performance when these carbons are used in Li ion batteries.