Han Gao-rong

The effect of the ratio of thiourea to Cd 2+ on the properties of CdS nanoparticles

CdS nanoparticles capped by thiourea and stabilized by PVP (poly N-vinyl-2-pyrrolidone) were prepared using a wet chemical route. The eventual particles size and size distribution can be systematically controlled by adjusting the relative ratios of thiourea to Cd2+. The nanoparticles were characterized by transmission electron microscopy (TEM), ultraviolet visible (UV-vis) absorption spectra and photoluminescence (PL) spectra. The results show that the higher thiourea/Cd2+ ratio leads to higher stability, smaller size and narrower size distribution. After the nanoparticles were capped by thiourea, the band emission of CdS nanoparticles can be observed in the PL spectra.

Preparation of CdS nanoparticles by hydrothermal method in microemulsion

CdS nanoparticles with good crystallinity were prepared by hydrothermal method in microemulsion composed of polyoxyethylene laurylether/water/cyclohexane/butanol. The structure and the size of the CdS nanoparticles were analyzed by TEM and XRD. The UV-Vis optical absorption of the samples was also investigated. The results show that hydrothermal treatment is an effective method to prepare CdS nanoparticles of hexagonal structure at lower temperature. The particles were in dimensional uniformity. The diameter of the CdS nanoparticles decreased with the increase of the molar ratio of water to surfactant. The minimum diameter of the CdS nanoparticles prepared in this work was about 10 nm. Obvious blue shift appeared in the UV-Vis absorption spectra.

Fabrication of Titanium Dioxide Thin Films by DBD-CVD Under Atmosphere

Titanium dioxide films were firstly deposited on glass substrate by DBD-CVD (dielectric barrier discharge enhanced chemical vapor deposition) technique. The structure of the films was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM). TiO2 films deposited under atmosphere pressure show preferred orientation, and exhibit columnar-like structure, while TiO2 films deposited under low gas pressure show no preferred orientation. The columnar-like structure with preferred orientation exhibits higher photocatalytic efficiency, since the columnar structure has larger surface area. However, it contributes little to the improvement of hydrophilicity. DBD-CVD is an alternative method to prepare photocatalytic TiO2 for its well-controllable property.

EFFECT OF NITROGEN AND HYDROGEN ON THE CRYSTALLIZATION OF NANOCRYSTALLINE SILICON NITROGEN FILMS

Hydrogenated nanocrystalline silicon nitrogen (nc-SiNx:H) films were prepared by rf glow discharge of gas mixture of silane (SiH4) and nitrogen (N2) diluted heavily by hydrogen (H2). The effect of the gas volume ratios Xg of (SiH4+N2)/H2 and XN of N2/SiH4 on the crystallization and composition of films is described. The growth process and crystallization mechanism of nc-SiNx:H films are discussed in detail.

BST Thin Film Deposited on Glass Substrate with TISI Nanowire Electrode by RF-Sputtering Method

Ferroelectric Ba 0.7 Sr 0.3 TiO 3 (BST) thin film is sputtered on the titanium silicide bottom layer with TiSi nanowires on glass substrate at room temperature and annealed at 450°C for 30 minutes. The phase structure, morphology, dielectric properties of the BST thin film are measured by X-ray diffraction, Field emission scanning electron microscopy, and Impedance Analyzer, respectively. The results show that the crystallinity of the BST thin film is perfect, and the capacitance is independent on the frequency between about 100 KHz and 8 MHz. The tunability is 52.1% with 9V applied dc bias voltage and the dielectric loss is below 0.09.

Simulation of scattering in dense medium by Monte Carlo method

We present a Monte Carlo (MC) method to simulate the scattering for medium within randomly distributed particles, discuss the convergence of this method by varying the size parameter ka, volume parameter η and calculation parameter Ni, then compare this method with the classical iteration method with the same parameters. The calculation results showed that this method has good convergence and accords with the iteration method while consuming less CPU time. At the end of this paper, this method is used to discuss the visual light scatter in the c-Si/α-Si films.

First-principles study of the influences of oxygen defects upon the electronic properties of Nb-doped TiO2 by GGA + U methods

The influence of oxygen defects upon the electronic properties of Nb-doped TiO2 has been studied by using the general gradient approximation (GGA)+U method. Four independent models (i.e., an undoped anatase cell, an anatase cell with a Nb dopant at Ti site (NbTi), an anatase cell with a Nb-dopant and an oxygen vacancy (NbTi+VO), and an anatase cell with a Nb-dopant and an interstitial oxygen (NbTi+Oi)) were considered. The density of states, effective mass, Bader charge, charge density, and electron localization function were calculated. The results show that in the NbTi+VO cell both eg and t2g levels of Ti 3d orbits make contributions to the electronic conductivity, and the oxygen vacancies (VO) collaborate with Nb-dopants to favor the high electrical conductivity by inducing the Nb-dopants to release more excess charges. In NbTi+Oi, an unoccupied impurity level appears in the band gap, which served as an acceptor level and suppressed the electronic conductivity. The results qualitatively coincide with experimental results and possibly provide insights into the preparation of TCOs with desirable conductivity.

Electret Characteristics of Hybrid Films Consisting of Porous Polytetrafluoroethylene and Teflon Fluoroethylenepropylene with Corona Charging

We have prepared hybrid films consisting of porous polytetrafluoroethylene (PTFE) and Teflon fluoroethylenepropylene (FEP) and we have investigated their charge dynamics of injection, transport and trapping using corona charging, isothermal and thermally stimulated surface-potential decay measurements. The results indicate that the hybrid film samples show different electret characteristics when charged through side PTFE or side FEP. The samples charged negatively through side porous PTFE show the best charge stability. Their charge dynamics differs very much from a single film. The effect of corona polarity on the electret behaviour in the hybrid film is very large. The experimental results are explained with the three structure level model of charge storage in electrets.

柱状晶形貌TiO 2 膜厚对FTO/TiO 2 镀膜玻璃光催化活性影响

采用溶胶-凝胶法, 在FTO(SnO 2 :F)低辐射镀膜玻璃衬底上制备了柱状晶体结构的TiO 2 薄膜, 获得双层结构FTO/TiO 2 镀膜玻璃样品. 研究了TiO 2 薄膜厚度对FTO/TiO 2 镀膜玻璃样品的光催化活性、低辐射性能以及透光性能的影响. 结果表明, FTO/TiO 2 镀膜玻璃样品光催化活性随着TiO 2 薄膜厚度的增加先升高后下降, 在TiO 2 薄膜厚度为300 nm时光催化活性最佳; 低辐射性能随着TiO 2 薄膜厚度的增加而下降, 但TiO 2 薄膜厚度为300 nm时仍然具备一定的低辐射性能; 透光性能与TiO 2 薄膜膜厚的关系不大, 可见光透射比保持在72%左右; 表面平均粗糙度约为1 nm, 表面光滑, 不易沾染油污灰尘. 该镀膜玻璃在保证低辐射建筑节能和透光的前提下, 兼具光催化自清洁功能, 具有很好的应用前景.采用溶胶-凝胶法, 在FTO(SnO 2 :F)低辐射镀膜玻璃衬底上制备了柱状晶体结构的TiO 2 薄膜, 获得双层结构FTO/TiO 2 镀膜玻璃样品. 研究了TiO 2 薄膜厚度对FTO/TiO 2 镀膜玻璃样品的光催化活性、低辐射性能以及透光性能的影响. 结果表明, FTO/TiO 2 镀膜玻璃样品光催化活性随着TiO 2 薄膜厚度的增加先升高后下降, 在TiO 2 薄膜厚度为300 nm时光催化活性最佳; 低辐射性能随着TiO 2 薄膜厚度的增加而下降, 但TiO 2 薄膜厚度为300 nm时仍然具备一定的低辐射性能; 透光性能与TiO 2 薄膜膜厚的关系不大, 可见光透射比保持在72%左右; 表面平均粗糙度约为1 nm, 表面光滑, 不易沾染油污灰尘. 该镀膜玻璃在保证低辐射建筑节能和透光的前提下, 兼具光催化自清洁功能, 具有很好的应用前景.Columnar crystal structured TiO2 thin films were prepared on the FTO (SnO2: F) low-emissivity coated glass substrates, obtaining double-layer structure FTO/TiO2 coated glass samples. The effect of TiO2 film thickness on the photocatalytic activity, the low-emissivity performance and light transmission properties of the FTO/TiO2 coated glass samples was investigated. The results showed that the photocatalytic activity of the samples increased firstly and then decrease with the increase of the film thickness. The best catalytic activity was observed for the sample coated with 300 nm TiO2 film. The low-emissivity properties of the samples declined as the TiO2 film thickness increased. The sample still have some low-emissivity performance when the TiO2 film thickness is 300 nm, while the light transmittance of the samples have little relations with the TiO2 films thickness. The visible light transmittances of the samples remain at about 72% with a smooth surface. The average surface roughness of the sample is about 1 nm. The FTO/TiO2 coated glass has photocatalytic self-cleaning properties with excellent low emissive performance and light transmittance property, thus guaranteeing good application prospects.