溶胶凝胶法制备Pt/WO3氢气敏感材料的研究

采用溶胶凝胶法制备纳米级WO3,掺杂不同含量的氯铂酸并混合搅拌均匀,再进行热处理,将所得粉体均匀涂覆在光纤光栅周围,制备出具有氢敏特性的光纤光栅传感器.实验中,通过改变氯铂酸掺杂量和热处理温度并进行XRD物相分析得:随着Pt∶W的降低以及热处理温度的升高,WO3的结晶度不断提高;通入不同浓度的氢气对传感器进行氢敏性能测试发现,经过300℃热处理,Pt∶W为1∶9时,对4%浓度的氢气能达到15s的响应速度,最高有140pm的中心波长变化,多次重复通氢气,重复性良好;当热处理温度达到500℃时,材料对氢气已经不敏感.     

超声化学法制备纳米WO3掺杂聚苯乙烯及其表征

 为了满足惯性约束聚变和电磁内爆实验对靶材料的需求，以W(CO)_{5/sub>为原料，利用超声化学法在线制备纳米WO3/sub>掺杂聚苯乙烯。所得样品用TEM，XPS，FTIR和TG进行了表征。测试结果表明，钨元素主要以WO3/sub>的形态存在，WO3/sub>粒径分布为20~50 nm，WO3/sub>微粒被聚苯乙烯完全包覆，掺杂后聚苯乙烯的热稳定性提高了70 ℃。在此基础上，对超声化学法的反应机理进行了探讨。研究表明：纳米WO3/sub>与聚苯乙烯分子链有一定的化学键结合，纳米WO3/sub>在聚苯乙烯基体中分布均匀。}     

CdTe太阳电池前电极SnO2:F/SnO2复合薄膜性能分析

减薄CdS窗口层是提高CdS/CdTe太阳电池转换效率的有效途径之一,减薄窗口层会对器件造成不利的影响,因此在减薄了的窗口层与前电极之间引入过渡层非常必要.利用反应磁控溅射法在前电极SnO₂:F薄膜衬底上制备未掺杂的SnO₂薄膜形成过渡层,并将其在N₂/O₂=4 ∶1,550 ℃环境进行了30 min热处理,利用原子力显微镜、X射线衍射仪、紫外分光光度计对复合薄膜热处理前后的形貌、结构、光学性能进行了表征,同时分析了复     

Nd掺杂对Bi4Ti3O12铁电薄膜的微结构和铁电性能的影响

利用溶胶-凝胶法在Pt/Ti/SiO₂/Si(100)衬底上制备了Nd掺杂Bi₄Ti₃O₁₂(Bi_4-xNd_xTi₃O₁₂, x=0.00,0.30,0.45,0.75,0.85,1.00,1.50)铁电薄膜样品.研究了Nd掺杂对Bi₄Ti₃O₁₂薄膜的微结构和铁电性能的影响.研究结果表明:Nd掺杂未改变Bi₄Ti₃O₁₂薄膜的基本晶体结构.在掺杂量x<0.45时,Nd³⁺只取代类钙钛矿层中的A位Bi³⁺.当x=0.45时,样品剩余极化强度达最大值,在270kV·cm^-1的电场下为32.7μC·cm^-2.掺杂量进一步增加时,结构无序度开始明显增大,Nd³⁺开始进入(Bi₂O₂)²⁺层,削弱其绝缘层和空间电荷库的作用,导致材料剩余极化逐渐下降.当掺杂量x达到1.50时,掺杂离子最终破坏(Bi₂O₂)²⁺层的结构,材料发生铁电-顺电相变.     

使用金属掺杂SnO2(110)作为表面催化剂的电催化CO2还原反应：通过调控Sn:O原子比例来控制产物

电催化CO₂还原反应可以产生HCOOH和CO,目前该反应是将可再生电力转化为化学能存储在燃料中的最有前景的方法之一. SnO₂作为将CO₂转换为HCOOH和CO的良好催化剂,其反应发生的晶面可以是不同的. 其中(110)面的SnO₂非常稳定,易于合成. 通过改变SnO₂(110)的Sn:O原子比例,得到了两种典型的SnO₂薄膜：完全氧化型(符合化学计量)和部分还原型. 本文研究了不同金属(Fe、Co、Ni、Cu、Ru、Rh、Pd、Ag、Os、Ir、Pt和Au)掺杂的SnO₂(110),发现在CO₂还原反应中这些材料的催化活性和选择性是不同的. 所有这些变化都可以通过调控(110)表面中Sn:O原子的比例来控制. 结果表明,化学计量型和部分还原型Cu/Ag掺杂的SnO₂(110)对CO₂还原反应具有不同的选择性. 具体而言,化学计量型的Cu/Ag掺杂的SnO₂(110)倾向于产生CO(g),而部分还原型的表面倾向于产生HCOOH(g). 此外,本文还考虑了CO₂还原的竞争析氢反应. 其中Ru、Rh、Pd、Os、Ir和Pt掺杂的SnO₂(110)催化剂对析氢反应具有较高的活性,其他催化剂对CO₂还原反应具有良好的催化作用.     

热处理对CuIn(S,Se)2薄膜断面成分均匀性的影响

用同时硒硫化共溅射Cu-In预制层的方法制备了CuIn(S,Se)₂薄膜．为了了解热处理对CuIn(S,Se)₂薄膜断面成分均匀性的影响,对经"一段式"热处理(500 ℃)和"二段式"热处理(250 ℃保温然后500 ℃)的样品进行了研究．XRD测试结果表明,经过"一段式"热处理后的样品XRD(112)峰出现劈裂现象,而经过"二段式"热处理的样品XRD(112)峰比较匀称．GIXRD和EDS测试证明样品经过"二段式"热处理后断面成分均匀性较好．通过XRD 和Raman测试对两种热处理下的反应机理进行了研究,阐述了两种热处理对CuIn(S,Se)₂薄膜断面成分均匀性的影响的内在原因．     

超声强化合成MgFe2O4纳米颗粒及其机理研究

用超声水解方法制备MgO纳米颗粒,用化学沉淀法制备α-Fe₂O₃纳米颗粒,将MgO/α-Fe₂O₃混合体常温下超声活化2h,400℃固相合成制备出MgFe₂O₄纳米颗粒.通过X射线衍射和透射电子显微镜测试产品的化学成分、晶体结构和形貌尺寸,分析声化学反应机理及其影响因素.研究结果表明:所制备的MgFe₂O₄为尖晶石铁氧体,颗粒尺寸分布在20-30nm之间,粒度分布均匀;超声空化效应提高了化学反应活性、增加反应物的比表面积和反应物之间的接触面积,促进固相合成反应速度,降低反应温度,实现了一般条件下难以完成的化学反应.     

NaAlH4 表面Ti催化空间构型和X射线吸收光谱: Car-Parrinello分子动力学和密度泛函理论研究

通过采用Car-Parrinello分子动力学方法对掺杂Ti前后的NaAlH₄(001)2×2×1超晶胞表面晶体在333 K(60 ℃)温度条件催化脱氢的空间构型做了理论研究,发现掺杂Ti的合金中AlH₄团的其中两个Al—H键长分别从约1.64 (1 =0.1 nm)增大至1.74和1.93 ,而未掺杂合金表面中AlH₄团的4个Al—H键长基本不变,这意味着掺杂Ti相对未掺杂的合金更易于放氢.但在模拟温度条件下并未发现Ti-Al成键趋     

掺杂CeO2的75TeO2-25Nb2O5-5ZnO飞秒激光诱导瞬态光栅的研究

用泵浦探测技术研究了掺杂CeO₂的75TeO₂-25Nb₂O₅-5ZnO玻璃在飞秒激光诱导的瞬态光栅多级自衍射。从拉曼和吸收光谱中研究了玻璃的结构特性，并证明了此玻璃中存在Ce3+离子。这种瞬态光栅起因于光克尔效应，并通过Ce3+离子中1S0?1F3电子能级跃迁形成的激发态粒子数光栅而改善，一级衍射信号的转换效率可达到11%。这些实验结果显示了掺杂CeO₂的75TeO₂-25Nb₂O₅-5ZnO飞玻璃在全转换开关中具有广泛应用。     

掺杂浓度和烧结温度对CaWO4:Eu3+发光性能的影响

采用微乳液法合成掺杂浓度不同和烧结温度不同的CaWO₄:Eu³⁺系列荧光体, 这些荧光体都具有Eu³⁺离子的特征荧光发射. 在不同温度烧结后, 高浓度掺杂的样品(Eu³⁺掺杂30或50 mol%)可获得最大的发光强度, 低浓度掺杂的样品(掺杂0.5—2 mol%)在800 ℃烧结时也可获得优异的发光强度. 实验结果表明, Eu³⁺离子高浓度掺杂的CaWO₄:Eu³⁺在紫外光激发下可成为高效发光的荧光粉.     

Preparation of WO3 nanoparticles and application to NO2 sensor

WO₃ nanoparticles were prepared by evaporating tungsten filament under a low pressure of oxygen gas, namely, by a gas evaporation method. The crystal structure, morphology, and NO₂ gas sensing properties of WO₃ nanoparticles deposited under various oxygen pressures and annealed at different temperatures were investigated. The particles obtained were identified as monoclinic WO₃. The particle size increased with increasing oxygen pressure and with increasing annealing temperature. The sensitivity increased with decreasing particle size, irrespective of the oxygen pressure during deposition and annealing temperature. The highest sensitivity of 4700 to NO₂ at 1 ppm observed in this study was measured at a relatively low operating temperature of 50 °C; this sensitivity was observed for a sensor made of particles as small as 36 nm.     

超高温度系数V0.97W0.03 O2多晶薄膜的制备研究

将V₂O₅粉体与WO₃粉体均匀混合并压制成靶，用离子束增强沉积加后退火技术在SiO₂衬底上制备掺钨VO₂多晶薄膜.X射线衍射表明，薄膜取向单一，为VO₂结构的［002］相,晶格参数d比VO₂粉晶增大约0.34%；薄膜从半导体相向金属相转变的相变温度约28；室温(300 K)时的电阻-温度系数(TCR)可大于10%/K，是目前红外热成像薄膜TCR的四倍.W离子的半径大于V离子的半径，W的掺入在薄膜中引入了张应力,使薄膜相变温度降低到室温附近，是IBED V_0.97W_0.03O₂薄膜的室温电阻温度系数提高的原因. 关键词： 二氧化钒薄膜 薄膜掺杂 离子束增强沉积     

Response improvement for In2O3-TiO2 thick film gas sensors

In₂O₃ is introduced into TiO₂ by sol-gel method to improve the response/recovery rate and expand the operating temperature, when the In₂O₃-TiO₂ mixed system is exposed to H₂/O₂. The sensor is fabricated by thick film technology. Influence of In₂O₃ on the film phase composition, microstructure and sensing characteristics is discussed. Dynamic response properties show that the operating temperature of the mixed system is at 500-800 °C, which is about 600-800 °C for pure TiO₂. Response time of the sensor is about 200-260 ms (millisecond) while recovery time is in a narrow range of 60-280 ms at 600-800 °C. The promoting mechanism is suggested to arise from the introduction of In₂O₃ and grain size effect of the sensing film. Then In₂O₃-TiO₂ thick films are surface-modified by Pt using chloroplatinic acid. The promoting effect of Pt dispersed on the mixed system is also investigated.     

Correlation between crystallinity and resistive switching behavior of sputtered WO3 thin films

The as-deposited WO₃ thin films were post-annealed at different temperatures (300 °C and 600 °C) in air to investigate a correlation between crystallinity and switching behavior of WO₃ thin films. Associating the results of XRD, FTIR, XPS and FESEM measurements, the annealing-caused crystallinity change contributes to the variation of the switching behaviors of the WO₃ thin films. The as-deposited WO₃ films with low crystalline structure are preferred for random Ag conducting path, resulting in large switching ratio but fluctuating I–V hysteresis, whereas the annealed WO₃ films with crystallized compact structure limits Ag conducting path, favoring the stable I–V hysteresis but small switching ratio. It is therefore concluded that electrochemical redox reaction-controlled resistance switching depends not only on electrode materials (inert and reactive electrodes) but also on crystallinity of host oxide.     

VO2-WO3 nanocomposite thin films synthesized by pulsed laser deposition technique

Pure VO₂ and VO₂-WO₃ composite thin films were grown on quartz substrate by pulsed laser deposition (PLD) technique. The influence of varying WO₃ molar concentration in the range from x = 0.0 to x = 0.4 on structural, electrical and optical properties of VO₂-WO₃ nanocomposite thin films has been systematically investigated. X-ray diffraction studies reveal the single crystalline monoclinic VO₂ phase (m-VO₂) up to 10% of WO₃ content whereas both m-VO₂ as well as h-WO₃ (hexagonal WO₃) phases were present at higher WO₃ content (0.2 ≤ x ≤ 0.4). Optical transmittance spectra of the films showed blue shift in the absorption edge with increase in WO₃ content. Temperature dependence of resistivity (R-T) measurements indicates significant variation in metal-insulator transition temperature, width of the hysteresis, and shape of the hysteresis curve. Cyclic Voltammetry measurements were performed on VO₂-WO₃ thin films. A direct correlation between V/W ratio and structure-property relationship was established. The present investigations reveal that doping of WO₃ in VO₂ is effective to increase the optical transmittance and to reduce the semiconductor to metal phase transition temperature close to room temperature.     

Structure, electrochromic and optical properties of WO3 film prepared by dip coating-pyrolysis

The tungsten oxide (WO₃) film was grown by dip coating-pyrolysis method with the PEG-400 as the structure-directing agent. Microstructure of the WO₃ film was characterized by TG-DSC, XRD and SEM techniques. It was found that the film annealed at 350 °C for 2 h comprised cubic WO₃ and orthorhombic WO₃. The measurements of the cyclic voltammetry (CV) and UV-vis spectrum suggested that the WO₃ film had a good electrochromic reversibility performance. The film possessed excellent modulation to the visible light and the maximal average transmittance modulation reached 70.06%.     

Effects of O2/Ar ratio and annealing temperature on electrical properties of Ta2O5 film prepared by magnetron sputtering

The effects of the oxygen-argon ratio on electric properties of Ta2O5 film prepared by radio-frequency magnetron sputtering were investigated.The Ta2O5 partially transforms from the amorphous phase into the crystal phase when annealing temperatures are 800℃ or higher.The lattice constant of Ta2O5 decreases with the increase of the O2/Ar ratio,which indicates that oxygen gas in the working gas mixture contributes to reducing the density of oxygen vacancies during the deposition process.For the films deposited in working gas mixtures with different O2/Ar ratios and subsequently annealed at 700℃,the effective dielectric constant is increased from 14.7 to 18.4 with the increase of the O2/Ar ratio from 0 to 1.Considering the presence of an SiO2 layer between the film and the silicon substrate,the optimal dielectric constant of Ta2O5 film was estimated to be 31.Oxygen gas in the working gas mixture contributes to reducing the density of oxygen vacancies,and the oxygen vacancy density and leakage current of Ta2O5 film both decrease with the increase of the O2/Ar ratio.The leakage current decreases after annealing treatment and it is minimized at 700℃.However,when the annealing temperature is 800℃ or higher,it increases slightly,which results from the partially crystallized Ta2O5 layer containing defects such as grain boundaries and vacancies.     

磁控共溅射法制备的Zn2GeO4多晶薄膜结构及其光致发光研究

用射频磁控共溅射方法在不同温度的单晶硅基片上生长薄膜,然后在800℃真空环境下对薄膜进行退火处理,成功获得了结晶状态良好的Zn₂GeO₄多晶薄膜.利用X射线衍射(XRD),X射线光电子能谱(XPS)和原子力显微镜(AFM)对薄膜进行了结构、成分和形貌分析,研究了基片温度对三者的影响. 结果显示,当基片温度升高到400℃以上时,薄膜中的Zn₂GeO₄晶粒在(220)方向上显示出了明显的择优取向. 当基片温度在500—600℃范围内,有利于GeO₂结晶相的形成. XPS显示薄膜中存在着Zn₂GeO₄,GeO₂,GeO,ZnO四种化合态. 同时,随着基片温度的升高,晶粒尺寸增大且薄膜表面趋于平整. 薄膜的光致发光在绿光带存在中心波长为530和550nm两个峰,应该归因于主体材料Zn₂GeO₄中两个不同的Ge²⁺的发光中心. 关键词： 射频磁控溅射 2GeO₄')" href="#">Zn₂GeO₄ 荧光体     

Investigation on spectral features of tungsten ions in PbO-Bi2O3-As2O3 glass matrix

Lead bismuth arsenate glasses mixed with different concentrations of WO₃ (ranging from 0 to 6.0 mol%) were synthesized. Differential thermal analysis (DTA), optical absorption, ESR and IR spectral studies have been carried out. The results of DTA have indicated that there is a gradual decrease in the resistance of the glass against devitrification with increase in the concentration of WO₃ upto 4.0 mol%.The optical absorption spectra of these glasses exhibited a relatively broad band peaking at about 880 nm identified due to d_xy→d_x²_−y² transition of W⁵⁺ ions; this band is observed to be more intense in the spectrum of glass containing 4.0 mol% of WO₃. Further, two prominent kinks attributed to ³P₀→¹S₀, ¹D₂ transitions of Bi³⁺ ions have also been located in the absorption spectra. The ESR spectra of these glasses recorded at room temperature exhibited an asymmetric signal at g_⊥∼1.71 and g_ll∼1.61. The intensity of the signal is observed to be maximal for the spectrum of the glass W₄. The quantitative analysis of optical absorption and ESR spectral studies have indicated that there is a maximum reduction of tungsten ions from W⁶⁺ state to W⁵⁺ state in the glass containing 4.0 mol% of WO₃. The IR spectral studies have indicated that there is a increasing degree of disorder in the glass network with increase in the concentration of WO₃ upto 4.0 mol%.