Papers by Author: X.M. Yang

Abstract: Novel raspberrylike organic-inorganic hybrids consisting of spherical silica supporting smaller conductive polypyrrole particles were prepared through a self-assembly polymerization process by choosing chitosan as a modifying agent of silica surface. TEM shows the raspberrylike morphology of resulted hybrids. Hydrogen-bonding interaction between the acetylamino of chitosan and hydrogen atom on nitrogen of polypyrrole is a determining parameter to get the raspberrylike morphology. The raspberrylike silica-polypyrrole hybrids exhibited high conductivity of 8 s.cm-1 and its suspensions possessed good stability because of the special surface morphology. In the past few years, organic-inorganic nanocomposite particles have become the subject of rapidly growing interest for their superior properties (optical, mechanical, rheological, electrical, catalytic);1-2 In this field, silica is the most commonly used inorganic support. On the other hand, polypyrrrole(Ppy) is also commonly used organic shell.3 If Ppy nanocomposite systems can be prepared in stable colloidal form, the poor processibility of Ppy can be overcome, at lest partly, so that its applications can extended to wide areas. However, since silica is initially hydrophilic, hydrophobic Ppy shell is very difficult to get by direct surface polymerization. Only “raspberry” like composite was got. A high-resolution TEM picture obtained by Gill et. al. was the first report to reveal this unusual “raspberry” morphology where the composite particles were aggregates of the original small silica particles held together by the conducting polymer component which

Abstract: The superplasticity and microstructure of magnesium alloy ZK40 processed by ECAP for 1 and 4 passes were investigated. Tensile experiments at 523 K showed that the elongation of ZK40 was improved with the increasing passes. The elongation-to-failure of ZK40 processed by ECAP for 4 passes tested at 523 K and strain rate of 1×10-4s-1 was 660%. The microstructural analyses explained these results.