Papers by Author: Tian Min Wang

Abstract: Nickel Titanium alloy has been used widely in clinical iatrology for years because of its unique shape memory capability, proper elasticity and considerable biocompatibility. But as an implanted material, its possible release of Ni ions which might cause toxic effect and its improvable biocompatibility draw attentions of researchers. In this study, chitosan/heparin multilayer is coated on NiTi shape memory alloy by electrostatic self-assemble method. Field emission scanning electron microscopy (FE-SEM), contact angle test is used to show its surface character; hemolysis test, dynamic clotting time experiment and platelet binding test are utilized to investigate the blood compatibility of the materials. The results reveal that the hydrophilic character of the coated one is better than the substrate, and blood compatibility of NiTi is improved by coating treatment.

Abstract: Chromium-activated ZnGa2O4 nano-sized phosphor powder was prepared by the Sol-Gel technique using citric acid as chelator, and the microstructure and luminescent property were studied. The host ZnGa2O4 belongs to the spinel structure and the ZnGa2O4:Cr3+ phosphor powder exhibited bright red emission band. The excitation bands with peak of maximum height at about 250 nm, 410 nm and 560 nm were related to the charge transfer (CT) of Ga-O, 4A2-4T1 and 4A2-4T2 transitions of Cr3+, respectively. Different quenching concentrations of the CT state and intrinsic excitation were discovered originating from different energy transfer schemes. Meanwhile, with the increasing of the calcining temperature the PLE spectrum exhibited an obvious blue-shift which is attributed to the enhancement of the crystal field.

Abstract: An all-thin-film glass/ITO/MoO3/LiAlO2/NiOx/ITO device was deposited by magnetron sputtering for electrochromic application. The amorphous MoO3 and LiAlO2 thin films were prepared with the substrate temperature below 0 °C and in O2 and Ar gas pressure. The structure and surface morphology of the films were characterized by x-ray diffraction (XRD) and atomic force microscopy (AFM). It has been found that the amorphous LiAlO2 thin film was a suitable ion conductor for the electrochromic device. The transmittance in the wavelength range of 400-800 nm for the ITO/MoO3/LiAlO2/NiOx/ITO device changed from 14.48 % to 57.68 % by the applied voltage of 7 V. The blue-colored electrochromic property could be observed for the all-thin-film device. The experimental results indicated that such a monolithic system had great potential to be applied in flat-panel displays and smart windows.

Abstract: The direct current (DC) reactive magnetron sputtering of a metal copper target in oxygen-argon mixed atmospheres to produce thin films of crystalline copper oxides was described. The sputtering pressure, sputtering power and oxygen flow rate were established in order to control the structures and properties of Cu2O films. The as-deposited Cu2O films with various crystal structures have high visible absorption and photo-catalytic activity under visible light irradiation. The photo-catalytic properties of Cu2O films are affected by not only the crystal structure but also the surface morphology.

Abstract: In this paper, a series of mesoporous silica particles with different pore diameters were fabricated using tetraethyl orthosilicate (TEOS) as the network precursor, hexadecyl trimethyl ammonium bromide (CTAB) as a structure directing agent and 1,3,5-Trimethylbenzene (TMB) as a pore enlarge reagent. Compared with SAXRD and BET, the PALS may not only show the mesoporous information but also provide the structure information of microporous.

Abstract: L10 phase FePt alloy is regarded as one of the most promising materials for ultra high density magnetic recording media. However, structural point defects, which would reduce the media's signal to noise ratio, are inevitable in non-stoichiometric L10 FePt alloy. Hence, possible types of point defect (vacancy and anti-site defect) in non-stoichiometric ordered FePt alloy were fully studied using density functional theory. Investigation over vacancy shows the formation energy of Fe and Pt vacancy is respectively 2.58eV and 3.20eV. Geometry relaxation implies Fe vacancy has a stronger deformation force upon the original lattice. Meanwhile, anti-site defect study shows that the formation energy of Fe anti-site (Fe occupation in Pt sublattice) and Pt anti-site (Pt occupation in Fe sublattice) is respectively 1.05eV and 0.66eV. Therefore, for Fe-rich and Pt-rich alloy, the preferred structural point defects are both anti-site substitution rather than vacancy due to the much lower formation energy.

Abstract: Based on double cermet layer structure, Mo-Al2O3 cermet solar selective coating was prepared on stainless steel substrate. A solar absorptance of 0.92 and normal emittance of 0.19 at room temperature have been achieved. Vacuum annealing treatment was done and its influences on the solar selective performance was discussed. Absorptance changed between 0.90 and 0.92 under the selected annealing temperature range of 350-800°C, and emittance varied from 0.19 to 0.23 when heated at 650°C. The microstructures before and after annealing process at different temperatures were investigated.

Abstract: ZnO:Al(ZAO) thin film is a kind of transparent conductive functional material which has a potential application in the solar cell and Atom Oxygen resisting systems of spacecrafts. High performance ZAO thin films were prepared by reactive magnetron sputtering and then irradiated by γ-ray with different dose or rate of irradiation. The as-deposited sample and irradiated ones were characterized by X-ray Diffraction, Scanning Electron Microscopy and Hall-effect measurement to investigate the dependences of the structure, morphology and electrical properties of ZAO on the dose and rate of γ-ray irradiation. Measurement of Positron Annihilation Doppler-Broadening Spectroscopy was carried out to study the variation of the defects in ZAO thin films before and after irradiation. It is indicated that γ-ray will excite the carriers, which are electrons in ZAO. A high rate of γ-ray irradiation could slightly destroy the bonds of Zn-O and decrease the crystallinity, while the effect of low rate irradiation is similar to heat annealing and increase the crystallinity of ZAO thin films. γ-ray has no apparent influences on the negative vacancy defects in ZAO thin film.

Abstract: In this paper, nanostructure zinc oxide (ZnO) hexagonal rods arrays on ZnO granular films coated substrates were fabricated by a simple chemical solution method. The shapes and structures can be controlled by changing the reactants and experimental conditions. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) equipped with energy dispersive spectrometer (EDS), and fluorescence spectrum were used to characterize the structures and luminescent properties. The best reacting condition has been discussed. Urea was found playing an important role in forming rods. The granular films acting as the seed films were proved.

Abstract: Y2O3:Eu3+ thin film was synthesized by sol-gel method with inorganic salt raw materials, and the crystal structure and luminescent properties were investigated. By adding organic additive to the sol, a homogeneous film with high luminescent intensity could be obtained by dip-coating technique on the surface of alumina sheet and quartz glass. Structures of the films were studied by XRD and SEM. The excitation spectra of the films showed a wide excitation peak from 200nm to 260nm, and the emission spectra had a strongest emission peak at 611nm which revealed a close relationship with the calcining temperature.