Advanced Materials Research Vols. 79-82

Abstract: Thin films of vinylidene fluoride with trifluoroethylene [P(VDF-TrFE)] copolymer have been deposited onto bare Si and SiO2 by spin casting from methylethylketone solutions. The structures and optical and electronic properties for P(VDF-TrFE) films after vacuum and forming gas annealing were studied. The degree of structural order and the crystallinity determined by X-ray diffraction were increased with the thermal annealing time. Ellipsometry spectroscopy were employed to investigate the changes in the thickness, refractive indices n, and the anisotropic properties. The results reflected that the n was increased with the thermal annealing time and temperature, and the anisotropy of the annealed films was strengthened with the annealing time and temperature. Metal-polymer-(oxide)-semiconductor capacitors were used to measure the static dielectric constant K and interfacial electronic properties of P(VDF-TrFE) on Si which the K increase with film thickness and thermal annealing. The interface at Al-P(VDF-TrFE) and/or P(VDF-TrFE)-Si affect the K value which is sensitive for films thinner than 120 nm. The Si-P(VDF-TrFE) interface quality determined using capacitance-voltage and current-voltage measurementswas found to be improved after forming gas annealed.

Abstract: This study investigates the effects of damp heat stability on the optoelectronic properties of ZnO:Al (AZO) and ZnO:Ga(GZO) films with respect to thin-film solar cells. The lowest resistivities of AZO and GZO thin films are 8.2621×10-4 Ω-cm and 2.8561×10-4 Ω-cm, respectively. After damp heat testing for 999h, the resistivities of AZO and GZO thin film increase by 39.72% and 11.97%, respectively. XPS binding energy analysis shows that the AZO thin film has a higher O 1s spectrum than the GZO thin film. Thus, the carrier concentration of films decreases, as a higher binding energy is attributed to the chemisorbed oxygen atoms (O-). Experimental results show that after expousre to a damp heat test at 85°C and 85% relative humidity for electrical, optical, structural, and morphological analysis, GZO films are more stable than AZO films.

Abstract: TiO2 thin films obtained by sol-gel and dipping deposition on glass fibers substrates followed by thermal treatment was used in this works. In an attempt to understand the structure and the morphology of TiO2 sol-gel thin films, analysis by X-ray diffraction (XRD) and scanning electron microscopy (SEM) are reported. Degradation of toluene under 365 nm light illumination was conducted to evaluate the photocatalytic ability of the TiO2 thin films. A special design of glass reactor allowed the UV lamp to be located in the center of the reactor. The photocatalyst reactor was then filled with TiO2 thin films/glass fibers substrates to exams the photocatalysis of toluene vapor ranged from 10 to 1,000 ppmv. Toluene depletion was sampled by gas chromatography (GC). The results showed that the photocatalytic performance of the reactor had high toluene depletion efficiency of 99.9% under 20 ppmv, and the efficiency decreased when toluene concentration were 100 and 1,000 ppmv. The improvement of the photocatalytic activity was ascribed to the fibers-based reactor provides a significantly huge surface area of the TiO2 thin films. These results will be useful and assist engineers to design photocatalyst reactors for the VOCs removal.

Abstract: The polycrystalline V2O5 films as the anode in V2O5 /LiPON /LiCoO2 lithium microbattary were prepared by RF magnetron sputtering system. The V2O5 films’ crystal structures, surface morphologies and composition were characterized and analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The microbatteries were fabricated by micro electro-mechanical system (MEMS) technology. The battery active unit area is 500μm×500μm, and the thickness of V2O5, LiPON and LiCoO2 films was estimated to be 200, 610, and 220nm, respectively. The discharge volumetric capacity is between 9.36μAhcm-2μm-1 and 9.63μAhcm-2μm-1 after 40 cycles.

Abstract: This paper reports the silica density, surface structures and optical properties of gold nanoparticles coated with different thickness of silica shells. The gold nanoparticles encapsulated with amorphous silica shells were prepared in a slight modification of Stǒber method. The silica-shell thickness could be varied from 20 to 50 nm by controlling the experimental conditions, such as reaction time. Transmission Electron Microscopy (TEM) and UV-Visible absorption spectroscopy were employed to characterize the size, shell density, surface structures and the optical properties of these silica-coated gold nanoparticles. The TEM images demonstrated that the density of the silica shell were depended on the reaction time, and the surface morphology was changed from porous structures in the initial coating to the final continuous and smooth silica surface. With the increasing of the reaction time, the silica-coated gold nanoparticles became more and more round and monodispersed. UV-Vis spectra showed that surface plasmon absorption peak had a red-shifted of 3~12 nm on increasing the thickness of silica shell from 20 to 50 nm. A possible mechanism of silica formation on gold nanoparticles was proposed on the basis of silica shell density and the shift of absorption peak of coated gold nanoparticles.

Abstract: A uniform TiO2 nanoparticle coating was prepared both on steel and slide glass using sol–gel method and hydrothermal post-treatments. The particle size in the sol was determined to be ～2nm. The surface morphology and the structure of the coatings were analyzed by scanning electron microscope (SEM) and X-ray diffraction（XRD）, which revealed the surface was compact and well-distributed, and the main phase was anatase. UV-VIS spectrophotometer indicated that a absorption peak existed at 340nm. The anticorrosion performances of the coatings in dark and under ultraviolet illumination have been evaluated by electrochemical techniques.

Abstract: Nanocrystalline titania porous films were prepared on ITO and glass substrates by polyethylene glycol（PEG）-assisted sol-gel method using Ti(C4H9COO)4 as precursor, ethanol as solvent and NH(C2H2OH)2 as chelating agent and PEG 2000as a template. When the amount of polyethylene glycol is within the range of 0～2. 0g/L ,. The characteristics and microstructure of films as well as the chemical and physical changes taken place during so-gel and heat treatments were analyzed by XRD, SEM and Emission spectra. The Cyclic voltammetry which measurements the films by illumination with a high pressure mercury lamp are employed to analyze photoelectrochemical property the porous titania thin films. The effects of precursor concentration and PEG 2000 contention the characteristic of films were discussed. The Cyclic voltammetry experiment under UV light irradiation indicated that the pores in the TiO2 thin films enhanced its photoelectrochemical activity; the size of the pores thin films obviously affected the photo-current exchanged rate of titania films.

Abstract: The hexagonal and the monoclinic CePO4 with rod-like coated ZrO2 composite powders were successfully synthesized through the hydrothemal method. the coated powders were characterized by the techniques of XRD, TEM, DTA and zeta potential measurements. In addition, the morphology of the coated powders after calcinations at 1000°C was also investigated.

Abstract: Cerium-based conversion coating process for corrosion protection is a potential replacement of chromates. However, there are still some defects such that the processing time is too long and the conversion coatings are not thick enough. The experiment proves that compared to non-added animal gelatin in corrosion-inhibiting cerium solution, the added one improves the deposition rate. After post-treatment process in phosphate, the surface morphology of the coatings is tested by scanning electron microsopy (SEM), the chemical composition of the protective films have been examined by energy-dispersive Spectrometer (EDS) and thickness of films is measured by coating thickness gauge.

Abstract: The weather resistance of 10CuPRE、10CuP and Q235 steels were studied by dry-wet cyclic immersion test. The corrosion resistance mechanism of rare earth Cu-containing weathering steel was studied through electrochemical polarization test, scanning electron microscope(SEM) and X ray diffraction(XRD). The results show the small and spherical rare earth oxysulfides replace the elongated MnS inclusions in the rare earth weathering steel. Less and fewer rare earth oxysulfides heavily decrease pitting susceptibility and rate of pit propagation. So the electrochemical corrosion of microarea in the steel matrix is weakened after rare earth was added in the Cu-containing weathering steel. The inner rust layer of rare earth weathering steel is more compact and uniform than that of weathering steel without rare earth. The main corrosion product on the rare earth weathering steel is α-FeOOH. The formation of the steady corrosion product is promoted by rare earth, which result in that the protective property of the inner rust layer on weathering steels is enhanced. As a result, the corrosion resistance of Cu-containing weathering steel is improved by rare earth elements.