Papers by Author: H.J. Wang

Abstract: CNTs/Fe/Al2O3 nanocomposites were prepared by thermal CVD and SPS methods. The dispersion of CNTs in the Fe/Al2O3 matrix were controlled by an attrition milling process. FESEM analysis revealed that the CNTs of 5 vol.% were homogeneously dispersed in the Fe/Al2O3. The effects of CNTs dispersion on the mechanical and electrical properties of the specimens were investigated. Fracture strength and electrical conductivity of 5 vol.% CNTs/Fe/Al2O3 specimen were measured at 641 MPa and 2.93
10-11 mS/m, whereas that of a 20 vol.% CNTs/Fe/Al2O3 specimen were 208 MPa and 8.46
10-7 mS/m, respectively. In comparison with an Al2O3 monolith, the specimen with 5 vol.% CNTs showed enhanced fracture strength and increased electrical conductivity.

Abstract: To overcome the difficulty of preparing the stoichiometric single phase calcium phosphate materials, ultrasonic spray pyrolysis was used to fabricate various calcium phosphates. Effect of the initial Ca/P ratios and pyrolysis temperature were investigated in preparation of single phase materials. Also thermal stability of the obtained powders was estimated with the heat treatment in the air. Crystallinity of the powders was analyzed using XRD and FT-IR. The HAp and β-TCP powders with single phase could be obtained from their stoichiometric Ca/P ratios of 1.50 and 1.67, respectively. These single phase powders with good crystallinity and stoichiometry were stable with respect to heat treatment up to 1000oC. The particle size of these powders would be controlled by the concentration of starting solution.

Abstract: CNTs/metal/Al₂O₃ nanocomposite powders were fabricated by thermal chemical vapor deposition (CVD) of C₂H₂ gas over metal/Al₂O₃ nanocomposite catalysts prepared by the selective reduction of oxide/Al₂O₃ powders. The yield and diameter of CNTs significantly depended on the kind of metal catalyst and catalyst size. X-ray diffraction (XRD) was used for phase identification. The morphology of CNTs was determined using field emission scanning electron microscopy (FESEM). FT-Raman spectroscopy revealed that the CNTs have single- and multi-walled carbon nanotubes structure. The relationship between the CNT yield/diameter and the characteristics of the composite catalyst was systematically investigated.