Papers by Author: S.W. Du

Abstract: Boron carbide is one of the hardest materials known. The research on the synthesis of nano-sized boron carbide is of great importance. RF plasma synthesis of B4C nanoparticle was carried out by powder feeder using micro-sized commercial boron carbide powder as the stating material. Different plasma energy and powder feeder probe position was used to find out the optimum condition to achieve nanoparticles. Powders were collected from Chamber 1, 2 and 3. fine particles can be achieved, but the decomposition and oxidation of B4C powder during the high temperature plasma spray was detected. Boron oxide was found in the sprayed powder, and the powder was purified by washing and heat treatment. XRD, SEM and TEM was used to for characterization of the particles.

Abstract: The Herzer model suggests that superior magnetic properties can be observed in magnetic alloys provided a suitable microstructure consisting of soft magnetic nanometre size precipitates separated by nanometre size distances is obtained. In order to explore new magnetic alloy compositions which can satisfy the Herzer model, we studied selected alloys in which we wished to obtain suitable microstructures, one such alloy has the composition Fe40Ni38B18Mo4. This alloy is amorphous as received, the heat treatment schedule required to obtain nanoprecipitates was designed based on DSC, resistivity and x-ray results. Heat treatment at temperatures between 420 0C and 500 0C and different heat times was carried out on the amorphous ribbon. Transmission Electron Microscopy (TEM) results of the early stage of crystallization behavior showed that soft magnetic precipitates of nano-size were indeed observed within the amorphous matrix. The crystal structure, composition analysis and thermal stability of the precipitates were studied by XRD, EDS and TEM. These results will be presented and the implication of these results to the production of new soft magnetic alloys will be emphasized.