Papers by Author: P.C. Chang

Abstract: Ga doped ZnO (GZO) films were prepared by radio frequency (rf) magnetron sputtering on glass or silicon substrates. Electrical, optical, and structural properties of these films were analyzed in order to investigate their dependence on thermal annealing temperature. GZO films with a minimum resistivity of 5.2×10-3 Ω-cm annealed at 400°C and a transparency above 80% in visible region were observed. The temperature-dependent conductivity affected the carrier transport and was related to the localization of carriers. The results of transmission spectra were consistent with the results of atomic force microscopy (AFM) scan. X-ray diffraction analysis and electron spectroscopy for chemical analysis were also used to investigate the properties of GZO films.

Abstract: This study is to investigate tribological behavior of brake lining materials by hot pressing commercial friction powders with ceramic powders prepared by TEOS / boehmite sol-gel. The stoichiometric ratios of TEOS / boehmite sol-gel were kept constant but calcinated at different temperature to fabricate different homemade ceramic powders. The various phases of ceramic powders such as γ-Al2O3, δ-Al2O3, θ-Al2O3, α-Al2O3, cristobalite and mullite were formed during the preparation process starting from TEOS / boehmite sol-gel solution. The XRD observations reveal the final compositions of these homemade powders were strongly related to the calcining temperature. The brake lining specimens made from TEOS / boehmite sol-gel calcinated at higher temperature show better tribological performance. The brake lining specimen with α-Al2O3 and mullite which were transformed from TEOS / boehmite sol-gel calcinated at 1300°C shows the most stable friction coefficient and the lowest mass loss during wear tests.