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1.
采用稀土气相扩渗法制备了La改性的BaTiO3基PTC陶瓷,并对其室温电阻率的变化及温-阻效应进行了研究.结果表明,BaTiO3基PTC陶瓷经La气相扩渗后,室温电阻率从2.7×109Ω.m下降到220Ω.m,在25-500℃范围内,电阻率随温度升高单调递减,从220Ω.m降至5.8Ω.m,产生了明显的NTCR效应.结合XRD,SEM,EDAX以及介电性能测试结果分析了La气相扩渗BaTiO3基PTC陶瓷NTCR效应的形成机理,建立了NTCR效应的物理结构模型.  相似文献   

2.
聚合物前驱体法制备立方相WO_3薄膜的光电化学性质   总被引:2,自引:0,他引:2  
以(NH4)6W7O24·6H2O为钨源,聚乙二醇1000(PEG 1000)为配位聚合物,采用聚合物前驱体法制备了WO3薄膜,利用X射线衍射(XRD)、扫描电子显微镜(SEM)、紫外-可见(UV-Vis)吸收光谱等手段对其结构进行表征.采用循环伏安法、Mott-Schottky测试、瞬态光和稳态光电流谱等方法研究了WO3薄膜电极的光电化学性能.结果表明,制备的WO3薄膜为立方晶系,禁带宽度约为2.7eV.当热处理温度为450℃时,载流子浓度达到最大2.44×1022cm-3,平带电位为0.06V,在500W氙灯光源照射和1.2V偏压下,光电流密度为2.70mA·cm-2.进一步探讨了热处理温度对其光电性质的影响及其机理.  相似文献   

3.
通过溶胶-凝胶工艺,采用两步加热法在聚酰亚胺表面制备了具有c轴取向的ZnO薄膜.通过差式扫描量热-热重分析(DSC-TGA)得出最佳的前热处理温度和后热处理温度分别为300和390℃.通过X射线衍射(XRD)和扫描电子显微镜(SEM)对薄膜的晶体取向和表面形貌进行了分析,描述了ZnO薄膜在聚酰亚胺上的生长过程.拉伸实验结果表明,ZnO薄膜与聚酰亚胺衬底有较强的附着力.  相似文献   

4.
采用一步式阶跃电压加压方法,在NH4F/(NH4)2SO4电解质溶液中对W片进行阳极氧化处理制备了WO3多孔薄膜,通过后续热处理温度的控制,制备了性能规律性变化的WO3多孔纳米薄膜材料.用场发射扫描电镜(FE-SEM)、X射线衍射(XRD)分析等手段考察了热处理温度对氧化钨晶体结构和形貌影响的规律,在450°C以下的煅烧温度下,薄膜保持50-100nm孔径;通过对光电化学性质、光催化降解甲基橙动力学行为的研究,考察了不同热处理温度对WO3多孔薄膜光电转换性能影响的规律.研究表明,450°C煅烧处理后的WO3薄膜在500W氙灯光源照射及1.2V偏压下,光电流密度达到5.11mA·cm-2;340及400nm单色光辐射下光电转换效率(IPCE)值分别达到87.4%及22.1%.电化学交流阻抗谱显示,450°C煅烧处理后的WO3薄膜表现出最佳的导电率及最小的界面电荷转移电阻.实验结果证明,高结晶度的多孔结构是WO3薄膜具有高光电转换效率的主要因素,控制热处理温度是实现薄膜具有高孔隙率、完整结晶度、低电阻的重要手段.  相似文献   

5.
纳米二氧化钒薄膜的制备及红外光学性能   总被引:2,自引:0,他引:2  
采用双离子束溅射方法在Si3N4/SiO2/Si基底表面沉积氧化钒薄膜, 在氮气气氛下热处理获得二氧化钒薄膜. 利用X射线衍射(XRD)、扫描电子显微镜(SEM)和X射线光电子能谱(XPS)研究了热处理温度对氧化钒薄膜晶体结构、表面形貌和组分的影响, 利用傅里叶变换红外光谱(FT-IR)对二氧化钒薄膜的红外透射性能进行了测试分析. 结果表明, 所制备的氧化钒薄膜以非晶态V2O5和四方金红石结构VO2为主, 经400 ℃、2 h热处理后获得了(011)择优取向的单斜金红石结构纳米VO2薄膜, 提高热处理温度至450 ℃, 纳米结构VO2薄膜的晶粒尺寸减小. FT-IR结果显示,纳米VO2薄膜透射率对比因子超过0.99, 高温关闭状态下透射率接近0. 小晶粒尺寸纳米VO2薄膜更适合在热光开关器件领域应用.  相似文献   

6.
本文利用三甲基氯硅烷与硅胶表面羟基反应的方法制备了甲基化硅胶。测定了亲水硅胶和甲基化硅胶的热处理对其自四氯化碳中吸附乙酸的等温线的影响,并配合有热重分析(TG)和红外光谱(IR)的测定。结果表明:(1)甲基化后的硅胶对乙酸的吸附能力大大下降;(2)甲基化硅胶的热处理温度达500℃时吸附能力完全恢复到甲基化前的硅胶的水平,甲基化层明显开始破坏的温度为450℃;(3)甲基化硅胶高温处理后吸附能力得以恢复的主要原因是重新形成表面自由羟基。  相似文献   

7.
溶胶-凝胶多孔性硅胶薄膜的制备及吸附特性研究   总被引:1,自引:0,他引:1  
研究了纳米硅溶胶和多孔性硅胶薄膜的制备与性能.一定条件下Na2SiO3溶液经过阳离子交挟树脂除去Na+离子后形成纳米硅溶胶,再经过调节pH值和添加化学添加剂如丙三醇、聚乙烯醇(PVA)形成硅溶胶前体.用甩膜法制备的凝胶二氧化硅薄膜在约550℃下热处理30min后,薄膜孔径分布在55~310nm之间.对硅溶胶的粒度分布、粘度和多孔性硅胶薄膜的形貌、孔率分布和吸附性能及相关参数进行了表征,从中得知,通过化学添加剂、调节硅溶胶pH值可控制硅溶胶粒度分布,从而达到控制多孔性硅胶薄膜的徼结构;硅胶薄膜热处理温度在很大程度上影响着硅胶薄膜孔径、孔率分布和吸附量.考虑到硅胶薄膜微结构和吸附特性以及高温下多孔硅胶薄膜会出现熔结现象等因素,二氧化硅溶胶pH为7.5时,凝胶薄膜热处理温度550℃最佳.  相似文献   

8.
以Zn(NO3)2•6H2O和AlCl3•6H2O为原料, 借助CO(NH2)2的水解反应, 采用化学均相共沉淀方法和热处理工艺, 在自制CaSiO3∶Pb, Mn红色荧光粉表面包覆ZnO∶Al, 形成透明导电层. 运用数字万用表和自制测量盒对粉体的电阻率进行测量, 比较了包覆率n(Zn)/n(Ca)、n(Al)/n(Zn), 热处理温度和热处理时间对粉体电阻率的影响; 优化出包覆条件和热处理条件: n(Zn)/n(Ca)=10%, n(Al)/n(Zn)=5%, 75 ℃水解1.5 h, 500 ℃热处理45 min. 对包覆样品进行了室温光致荧光(PL)测量, X射线衍射(XRD)结构分析和透射电子显微镜(TEM)形貌观察. 结果显示, 当n(Zn)/n(Ca)=10%时, 在CaSiO3∶Pb, Mn荧光粉表面形成了连续的ZnO∶Al敷膜, 荧光粉的电阻率明显降低, 并且保持了良好的光致发光性质.  相似文献   

9.
磁控溅射中靶-基底距离与Si共掺对ZnO:Al薄膜性质的影响   总被引:1,自引:0,他引:1  
徐浩  陆昉  傅正文 《物理化学学报》2011,27(5):1232-1238
使用射频磁控溅射, 在正方形石英衬底上沉积透明导电掺Al的ZnO(AZO)和Si共掺AZO(AZO:Si)薄膜. 系统研究了靶-基底距离(Dst)和Si共掺对AZO薄膜电学、光学性质的影响. 电阻率、载流子浓度和迁移率都强烈地依赖于靶-基底距离, 随着靶-基底距离的减少, 载流子浓度和迁移率都有显著的增加, 电导率也随之提高. 在靶-基底距离为4.5 cm处, 得到最低电阻率4.94×10-4 Ω·cm, 此时的载流子浓度和迁移率分别是3.75×1020 cm-3和33.7 cm2·V-1·s-1. X射线光电子能谱(XPS)、X射线衍射(XRD)和边界散射模型被用于分析载流子浓度、迁移率和靶-基底距离的关系. 透射谱显示, 在可见-近红外范围内所有样品均有大于93%的平均透射率, 同时随着靶基距离的减少, 吸收边蓝移. AZO:Si表现出可与AZO相比拟的高电导和高透射光学特性, 但在热湿环境中却有着更好的电阻稳定性, 这在实际使用中很有意义.  相似文献   

10.
醋酸铜热解制备无氯Cu2O/AC催化剂及其催化氧化羰基化   总被引:3,自引:3,他引:0  
以醋酸铜为前驱物, 采用浸渍法负载后进行热处理使醋酸铜热解, 获得了负载型无氯Cu2O/AC(活性炭)催化剂, 并通过催化甲醇直接气相氧化羰基化合成碳酸二甲酯(DMC). 在氮气和惰性气体气氛下, 一水合醋酸铜Cu(CH3COO)2·H2O在30~450 ℃范围内产生3个失重过程, 其中在150~300 ℃范围内Cu(CH3·COO)2热解生成Cu2O; 而在300~450 ℃范围内生成单质Cu. 在200~350 ℃范围内, 将Cu(CH3COO)2·H2O/AC加热处理4 h后, 催化剂上逐步形成了Cu2O, 到350 ℃时, 水合醋酸铜几乎全部转化为Cu2O, 并有极少量单质Cu形成. 在300~350 ℃热处理4 h后, 催化剂中铜主要以Cu2O形式存在, 并表现出良好的氧化羰基化催化活性. 在n(CO)∶n(MeOH)∶n(O2)=4∶10∶1及SV=5600 h-1条件下, 于300 ℃热处理4 h所制备的催化剂的甲醇转化率达到6.21%, DMC的时空收率为128.16 mg·g-1·h-1, 选择性为64.26%.  相似文献   

11.
氧化锌薄膜的电化学沉积和表征   总被引:9,自引:0,他引:9  
以透明导电玻璃(TCO)为衬底,用硝酸锌水溶液作为电解液,研究了阴极还原沉积ZnO薄膜的反应机理和电化学行为. 通过改变工艺条件来控制ZnO的生长速率, 得到了粒径为10~15 nm的纳米ZnO薄膜. XRD分析显示纳米ZnO薄膜纯度高, 呈纤锌矿结构. 光学测试结果表明,在可见光区其透光度高达90%,禁带宽度为3.37 eV.  相似文献   

12.
In this study, Ga‐doped ZnO thin films were prepared using sol–gel technique via spin‐coating method. The effect of Ga‐doping dopant (0, 1, 2 and 3 at.%) on microstructural, optical, electrical and photoelectrochemical (PEC) characteristics have been investigated. The spin‐coating was repeated six times, and as‐obtained thin films were then annealed at 500 °C for 1 h in vacuum. After annealing, all samples revealed single phase of hexagonal ZnO polycrystalline structure with a main peak of (002) in X‐ray diffraction (XRD) pattern. Raman spectra show that the vibration strength of E2 is highly decreased by Ga doping. Thicknesses of all samples were ~300 nm measured via scanning electron microscopy (SEM) cross‐section images and alpha‐step. The optical band gap and resistivity of samples were in the range of 3.24 to 3.28 eV and 102 to 9 Ohm cm, respectively. Resulting from PEC response, the 2 at.% Ga‐doped ZnO thin film has a better PEC performance with photocurrent density of ~0.14 mA/cm2 at 0.5 V versus saturated calomel electrode (SCE) under illumination with the intensity of 100 mW/cm2. This value was about seven times higher than the un‐doped film (reference sample). Observed higher photocurrent density was likely because of a suitable Ga‐doping concentration causing a lower resistivity. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

13.
ZnO thin films were deposited onto glass subsrates by a Sol-gel spin coating method. The structural and optical properties of ZnO thin films were investigated. The molar ratios of the zinc acetate dihydrate to Monoethanolamine were maintained 1:1. The as-grown film was sintered 250 °C for 10 min, then annealed in air at 500 °C for 30 min. The XRD results indicate that ZnO films were strongly oriented to the c-axis of the hexagonal nature. Absorption measurements were carried out as a function of temperature with 10 K steps in the range 10–320 K. The band gap energy was measured 3.275 and 3.267 eV for 0.5 and 1.0 molarity (M) ZnO thin films at 300 K. The steepness parameters were observed between 10 and 320 K and their extrapolations converged at (E0, α0) = 3.65 eV, 172,819 cm−1 and 3.70 eV, 653,436 cm−1 for 0.5 and 1.0 M ZnO thin films, respectively.  相似文献   

14.
在80℃水浴下,采用简易的湿化学法在不导电玻璃基底上制备了ZnO纳米棒阵列,利用X射线衍射仪(XRD)和场发射扫描电镜(FE-SEM)对样品的结构形貌进行了表征.结果表明,晶化30 min所得产物为六方纤锌矿相的ZnO纳米棒,直径大约为80~90 nm.为了分析不同的低温退火温度和退火气氛对其光致发光性能的影响,研究了ZnO纳米棒薄膜在不同的后处理条件下的光致发光谱(PL).实验结果表明,在O2气氛下于450℃退火1 h后,ZnO纳米棒薄膜的红光发射(约650 nm)强度相对在空气和5%H2/95%N2气氛下退火的样品变得更强,而且该样品的激发波长范围(200~370 nm)与近紫外发光二极管(LEDs)的发射波长范围(350~420 nm)匹配得很好.  相似文献   

15.
Pure and Ag-doped zinc oxide sol–gel thin films were prepared by spin-coating process. Pure and Ag–ZnO films, containing 2–8% Ag, were annealed at 500?°C for 2?h. All thin films were prepared and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV–visible spectroscopy. X-ray diffraction studies show the polycrystalline nature with hexagonal wurtzite structure of ZnO and Ag:ZnO thin films. The crystallite size of the prepared samples reduced with increasing Ag doping concentrations. AFM and SEM results indicated that the average crystallite size decreased as Ag doping concentration increased. The transmittance spectra were then recorded at wavelengths ranging from 300 to 1000?nm. The films produced yielded high transmission at visible regions. The optical band gap energy of spin-coated films also decreased as Ag doping concentration increased. In particular, their optical band gap energies were 3.75, 3.55, 3.4, 3.3, and 3.23?eV at 0%, 2%, 4%, 6%, and 8%, respectively. Antibacterial activity of pure and Ag-doped zinc oxide against Escherichia coli and Staphylococcus aureus was evaluated by international recognized test (JIS Z 2801). The results showed that pure and Ag-doped ZnO thin film has an antibacterial inhibition zone against E. coli and S. aureus. Gram-positive bacteria seemed to be more resistant to pure and Ag-doped ZnO thin film than gram-negative bacteria. The test shows incrementally increasing in antibacterial activity of the thin films when dopant ratio increased under UV light.  相似文献   

16.
Highly C‐axis oriented ZnO thin film was manufactured by radio‐frequency magnetron sputtering technique on Si (111) substrate. The main objective was to study the influence of rapid thermal annealing (RTA) temperature on the structure and interfacial characteristic of ZnO thin films. X‐ray diffraction results showed that the ZnO thin films annealed at 600 °C by RTA technique had a perfect C‐axis preferred orientation compared to the other ZnO thin films, and the full width at half maximum of ZnO (002) rocking curve measurements indicted that the RTA‐annealed ZnO thin films possessed better crystal structure. Atom force microscopy displayed that the grain size of RTA‐annealed ZnO thin films was fine and uniform compared with the as‐deposited ZnO thin films, although the grains grew in RTA process and the root meant square roughness was smaller than that of as‐deposited films. High‐resolution transmission electron microscopy showed that there was an obvious amorphous layer between ZnO thin films and Si substrate, but the RTA‐annealed ZnO thin films exhibited larger and denser columnar structure and a preferred orientation with highly c axis perpendicular to the amorphous layer. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

17.
Monolayer polystyrene spheres (∼400 nm) array templates were assembled orderly on clean glass substrates by dip-coating method from emulsion of polystyrene (PS). Porous ZnO thin films were also prepared by dip-coating method to fill the interstices among the close-packed PS templates with ZnO and annealing to remove the PS templates. Results showed that ZnO sol concentration and dipping time of PS templates in sol had great influences on the morphology of ordered porous ZnO thin films. There was a shrinkage ratio of about 30% from pore to PS. SEM observation showed that the PS array templates had face-centered cubic close-packing. X-ray diffraction (XRD) spectra showed the porous ZnO thin film was wurtzite structure. The optical transmittance decreased with decreasing wavelength of lights, but was kept above 80% beyond the wavelength of 550 nm. Optical band-gap of the porous ZnO thin film annealed at 500°C was 3.22 eV.  相似文献   

18.
Sol–gel spin-coating was used to grow zinc oxide (ZnO) thin films doped with 0–2.5 at.% B on quartz substrates. The structural, optical, and electrical properties of the thin films were investigated using field-emission scanning electron microscopy, X-ray diffraction (XRD), photoluminescence (PL), ultraviolet–visible spectroscopy, and van der Pauw Hall-effect measurements. All the thin films had deposited well onto the quartz substrates and exhibited granular morphology. The average crystallite size, lattice constants, residual stress, and lengths of the bonds in the crystal lattice of the thin films were calculated from the XRD data. The PL spectra showed near-band-edge (NBE) and deep-level emissions, and B doping varied the PL properties and increased the efficiency of the NBE emission. The optical transmittance spectra for the undoped ZnO and boron-doped zinc oxide (BZO) thin films show that the optical transmittance of the BZO thin films was significantly higher than that of the undoped ZnO thin films in the visible region of the spectra and that the absorption edge of the BZO thin films was blue-shifted. In addition, doping the ZnO thin films with B significantly varied the absorption coefficient, optical band gap, Urbach energy, refractive index, extinction coefficient, single-oscillator energy, dispersion energy, average oscillator strength, average oscillator wavelength, dielectric constant, and optical conductivity of the BZO thin films. The Hall-effect data suggested that B doping also improved the electrical properties such as the carrier concentration, mobility, and resistivity of the thin films.  相似文献   

19.
ZnO thin films doped with Ce at different concentration were deposited on glass substrates by spray pyrolysis technique. XRD analysis revealed the phase purity and polycrystalline nature of the films with hexagonal wurtzite geometry and the composition analysis confirmed the incorporation of Ce in the ZnO lattice in the case of doped films. Crystalline quality and optical transmittance diminished while electrical conductivity enhanced with Ce doping. Ce doping resulted in a red-shift of optical energy gap due to the downshift of the conduction band minimum after merging with Ce related impurity bands formed below the conduction band in the forbidden gap. In the room temperature photoluminescence spectra, UV emission intensity of the doped films decreased while the intensity of the visible emission band increased drastically implying the degradation in crystallinity as well as the incorporation of defect levels capable of luminescence downshifting. Ce doping showed improvement in photocatalytic efficiency by effectively trapping the free carriers and then transferring for dye degradation. Thus Ce doped ZnO thin films are capable of acting as luminescent downshifters as well as efficient photocatalysts.  相似文献   

20.
纳米ZnO薄膜的制备及其可见光催化降解甲基橙   总被引:9,自引:0,他引:9  
采用溶胶-凝胶方法制备ZnO透明溶胶, 在铝箔上涂膜后经500 ℃处理制得具有可见光响应的纳米ZnO薄膜光催化剂. 以甲基橙模拟有机污染物, 在可见光下研究了薄膜的降解性能, 结果表明, 用一片有效面积为200 cm2的ZnO/Al薄膜作为催化剂, 甲基橙的降解率达到96.3%, 比ZnO负载在玻璃上制得的ZnO/glass薄膜催化剂活性高得多. 采用扫描电镜与原子力显微镜对ZnO/Al薄膜制备条件进行了表征, 结果发现多孔ZnO/Al薄膜比致密ZnO/Al薄膜具有更高的活性, 实验制备的具有高活性的ZnO/Al薄膜颗粒平均直径为52.2 nm. 采用本方法制备的ZnO/Al薄膜是一种具有应用前景的, 能在可见光下降解有机物的有效光催化剂.  相似文献   

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