Papers by Author: Wen Hu Yang

Abstract: A magnetite composite composed of the organic compounds and Fe₃O₄ nanoparticles was prepared with microemulsion method. The Tween 80 and ammonia were used as surfactant and reducing agent, respectively, in synthesizing the Fe₃O₄ nanoparticles. The experimental results showed that the composite possessed good stability while the volume ratio of Tween 80 to butanol was 0.4 and the molar ratio of NH₄OH to Fe³⁺ was 14.6. The saturation magnetization of the composite depends on the molar ratio of NH₄OH to Fe³⁺. The mechanism of this stable Fe₃O₄ paste was realized by the Fe₃O₄ nanocomposite film using TEM. The microstructures of the film show that the magnetic nanoparticles in the composite are surrounded by Tween 80, which separates the magnetic nanoparticles and leads to good stability.

Abstract: The composites composed of micro-sized calcium copper titanate (CCTO) and nano-sized metallic nickel (Ni) fillers in the polyvinylidene fluoride (PVDF) matrix (Ni/CCTO/PVDF) were prepared, in which the filler content (volume fraction) of Ni and CCTO was set at 60 %. The impedance spectra and a serial equivalent circuit model consisting three RC units were used to investigate the behaviors of the Ni/CCTO/PVDF three-phase composite system near the percolation threshold. The real (Z′) and imaginary (Z″) parts of the impedance dramatically decreased as the Ni content was increased from 22% to 24% indicating a transition from an insulating to a conducting state. This transition process has been realized by the changes in the capacitance derived from the model, and the investigation has been carried out to clarify the release mechanism of the entrapped electrons at the interfaces.