Papers by Author: J.P. Tu

Abstract: NiO thin films were prepared on ITO glass by a modified sol-gel method in combination with a following annealing process. The XRD results show that the film annealed at 280 °C is amorphous, while the films annealed at and above 300 °C are cubic NiO phase. The electrochromic performances of the annealed films were characterized by means of UV–vis spectroscopy and cyclic voltammetry (CV) measurements. The film annealed at 280 °C exhibits a noticeable electrochromism with a variation of transmittance up to 76 % at 550 nm. The cyclic voltammetry (CV) measurements reveal that the film annealed at higher temperature has better electrochemical reversibility.

Abstract: Nickel foam-supported NiO spheres were prepared by an electrodeposition technique using nickel foam as the substrate, and then the Ag nanoparticles were loaded on the NiO spheres. SEM images showed that these NiO/Ag spheres are porous with a size of about 2 µm. As an anode for lithium-ion batteries, the nickel foam-supported NiO/Ag spheres exhibit higher coulombic efficiency, weaker polarization, and better cycling performance as compared to the NiO spheres. The improvements of these electrochemical properties are attributed to the Ag nanoparticles, which enhanced the electrical conduction of the electrode.

Abstract: Amorphous Ti/C multilayers were prepared on titanium-alloy and silicon (100)-wafer substrates by pulsed laser deposition. Films with different Ti concentration were synthesized by changing the ablating time for Ti and C targets. The morphology and microstructure of Ti/C multilayers were characterized by scanning electron microscopy (SEM), Raman spectroscopy and X-ray diffraction (XRD). Both of the Ti and C monolayers were amorphous. The metallic Ti stimulated the formation of more amorphous carbon phase by reducing the sp2 aromatic bonds and elongating the C-C chain bonds. The tribological properties of Ti/C multilayers were investigated by ball-on-disk tribometer. The pure C film and the multilayers containing more than 68.8 at.% of Ti showed low wear resistance. The multilayer contained 36.8 at.% of Ti exhibited the lowest wear rate at 3.54×10–16 m3/N·m. The formation of carbon related interlayer and its effect on tribological performance of the films were discussed.

Abstract: Well-crystallized nanopolycrystalline thin films of cubic strontium titanate, SrTiO3, have been prepared on the TiNi-deposited Ni substrate in Sr(OH)2 aqueous solutions at temperatures between 130 and 200°C under saturated vapor pressures. The microstructure and morphology of the films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The photoelectrochemical properties of SrTiO3 thin films on TiNi-deposited Ni substrate were investigated on a three-electrode assembly. The grain sizes increased from 30 nm to 300 nm and the relative crystal intensity in XRD pattern increased with the reaction temperature. Its photocurrent increasesdfirst with the grain size, then decreased. When the grain size of the film is about 200 nm, the photocurrent is highest.

Abstract: Al-substituted α-Ni(OH)2 was synthesized by a chemical co-precipitation. The as-prepared α-Ni(OH)2 particles were characterized by the means of X-ray diffraction (XRD) and scanning electron microscope (SEM). The obtained α-Ni(OH)2 particles were well crystallized, spherical shape with the particle sizes of 20-35 nm. The electrochemical performance of β-Ni(OH)2 electrode with addition of nanosized α-Ni(OH)2 was investigated by galvanostatic charge-discharge tests. The nanosized α-Ni(OH)2 as additive in the commercial microsized spherical β-Ni(OH)2 electrode improved the discharge capability. As compared to commercial β-Ni(OH)2 electrode, the electrode with nanosized α-Ni(OH)2 exhibited excellent better charge-discharge cycling stability. It may be a promising positive active material for alkaline secondary batteries.

Abstract: Bamboo-shaped carbon nanotubes (BCNTs) have been synthesized by chemical vapor deposition method. The activated BCNTs after simple ball milling and KOH etching are used as polarizable electrodes in electric double layer capacitor (EDLC). Our results show that the specific capacity of BCNTs can be improved by the activation treatment.