Papers by Author: Li Wang

Abstract: ZrO2-CeO2 thin film was successfully prepared on 316L stainless steel by sol-gel process and the corrosion characteristics of the substrate coated with ZrO2-CeO2 thin film were evaluated through potentiodynamic polarization curve obtained in deaerated 15% H2SO4. The results show that, with the increase of CeO2 content, the corrosion rate of 316L stainless steel substrates coated with ZrO2-CeO2 thin film decreases. The surface morphology of the coating was observed by field scanning electron microscopy and the elements in the surface of coated substrate analyzed by FEM-EDX.

Abstract: The chemical composition and the valence state of elements on the surface of ZrO2 thin films deposited on glass substrates have been studied by X-ray photoelectron spectroscopy. Results show that: elements of Na, Mg, Zr, Ca exist in the form of their respective stable state, such as Na2O, MgO, ZrO2, CaO, when heat treated at 500°C for 0.5h; but Si is unstable, and exhibit stoichiometrical disturbances. Results of chemical composition and their content by atom percent of ZrO2 thin films surface reveal that: Si, and Ca diffuse from glass to the thin films in scale; Na diffuses few and Mg collects to the thin films surface. The diffusion of Mg2+ and Ca2+ from glass to ZrO2 thin films is negative diffusion.

Abstract: The influence of heat-treated temperature and the CeO2 content on the chemical composition and the valence state of elements on surface of ZrO2-CeO2 thin films deposited on metal substrates has been studied by X-ray photoelectron spectroscopy. Results show that: elements of Fe, Cr, Zr, Ce exist in the form of their respective stable state, such as Fe2O3, (Fe0.6Cr0.4)O3, ZrO2, CeO2, when heat treated at 600°C and 700°C for 2h respectively; with the increase of heat-treated temperature, the area of oxygen with O1s peak corresponding to value of bonding energy 529.28ev increases, but the area of oxygen with O1s peak corresponding to value of bonding energy 531.7ev decreases.

Abstract: X-ray diffraction (XRD) method to measure the residual stress existing in the metal substrate surface layer was introduced and the sol-gel ZrO2-CeO2 thin film was successfully prepared on SUS304 stainless steel substrate by dip-coating process. The macro residual stress existing in metal substrate was analyzed by XRD. It turns out that the compressive stress existing in the metal substrate surface layer increases with the increase of heat-treated temperature. Based on the above study, colored stainless steels of high quality were prepared by sol-gel process.

Abstract: Antimony doped tin oxide (ATO) thin films were deposited onto silica coated soda lime silicate substrate by the sol-gel method using Sb(OC4H9)4 and Sn(OC4H9)4 as the precursor materials. Conductive tin oxide nano particles of different particle size were added into the sols. The films were subjected to heat treatment at t=500) for about one hour. Film structure and surface morphology has been investigated by means of atomic force microscopy (AFM). Room temperature electrical resistivity of the films was measured using the conventional four probe van der paul method. The influence of incorporation of conductive nano particles on the electrical conductivity of Sb-doped tin oxide films was studied. The correlation between the microstructure and the film electrical property has been obtained. The status of the nano particles in the films has also investigated by FTIR spectroscopy.

Abstract: Silver doped titania-silica films were fabricated by two-step route of sol-gel method using Ti(OC4H9)4, Si(OC2H5)4 and AgNO3 as the precursor materials. The films were annealed at temperature from 350°C to 560°C for a period of time ranging from 15min to 90 min. Optical properties of the films were characterized by UV-visible spectroscopy and the state of silver in the titania-silica films was investigated by XRD patterns. It was found that the annealing temperature and time have considerably influenced the coloration of the films, and with the increase of annealing temperature the [111] orientation of silver crystal occurred which make the color of silver doped titania-silica films deepened. The coloration stability of the silver doped titania-silica films was also investigated.

Abstract: Through X-ray photoelectron spectroscopy, by the aid of Ar+ sputtering, chemical composition and the valence state of elements on surface and at depth of TiO2-SiO2 thin films and metal substrates have been studied. Results show that: on surface, elements of Cr, Mn, Ti, Fe exist in the form of their respective stable state, but Si is unstable and exhibits stoichiometrical disturbance when heat treated at 800°C; at depth, after sputtering for 5 minutes and 17 minutes, elements of Cr, Mn, Ti and Ni exist in the form of their respective stable state, but Si and Fe are unstable and exhibit stoichiometrical disturbances; at depth, after sputtering for 57 minutes, all of the Cr, Mn, Ti, Si, Ni and Fe exist in the form of their respective stable state. Results of chemical composition and their content by weight percent of TiO2-SiO2 thin films and metal substrates reveal that: Fe, Cr, and Mn diffuse from metal substrates to the thin films in scale; Ni diffuses few and Si collects to the metal substrate surface

Abstract: Two-layer antireflective films were prepared on Na-Mg-Ca-Si glass substrate by sol-gel process starting from metal alkoxides: Si(OC2H5)4, Ti(OC4H9)4. The transmittance of glass was increased obviously (>95%), the reflective index was reduced to 1.95 through visible light range. TEM observation showed that SiO2 film is compactly joined to TiO2 film and TiO2 film to the substrate. TEM-EDX analysis of the films, film-substrate interface and substrate revealed that with the increase of Ti content, the content of Mg，Ca and Si decreases, however, the content of Na increases. The diffuse of Na+ from the substrate to the film is negative diffusion.