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介绍一种低温合成二氧化钛纳米粒子的新方法.将非晶型二氧化钛加入强酸性溶液中室温搅拌数小时后得到无色透明的溶液.继续在室温搅拌数48h后,可以得到高比表面的金红石相二氧化钛纳米粒子.改变处理过程温度及酸的种类,可以得到不同组成的纤维状二氧化钛纳米粒子.对盐酸体系进行详细讨论结果表明,在低于60℃时得到的是热力学稳定的金红石单一相,而在高于120℃时得到的是热力学亚稳态的锐钛矿单一相,高于170℃时得到的是锐钛矿及金红石的混合相,显示出与众不同的结晶行为.通过此低温法制备的金红石相二氧化钛在具有较小的吸收禁带的同时,还拥有100n2·g-1以上的比表面积.与锐钛矿相相比,显示了良好的可见光催化活性. 相似文献
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研究了晶粒粒径相近的金红石相、锐钛矿相和混晶纳米二氧化钛对苯胺、甲萘胺和邻氯苯胺3种物质的光催化降解。结果表明,晶粒粒径相近的金红石相和锐钛矿相二氧化钛纳米粒子对胺类化合物的光催化效果相近,特别是在反应的开始阶段,两者的差异很小;随着反应时间的增加,金红石相纳米二氧化钛的催化能力稍优于锐钛矿相纳米二氧化钛。成分不同的混晶的催化能力相差较大,随着混晶中的金红石相含量增加,催化剂的催化效果有了显著的提高。实验中还发现,不同的催化剂对苯胺、甲萘胺和邻氯苯胺3种物质同时催化过程中,3种有机物降解程度的顺序均为甲萘胺>邻氯苯胺>苯胺。 相似文献
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以氢气和氧气作为爆炸源,四氯化钛作为前躯体气相爆轰制备纳米二氧化钛是一种新兴的纳米氧化物制备方法。通过X射线衍射(XRD)分析其晶相组成,并通过透射电镜(TEM)观察了产物颗粒的大小和形貌,总结了氧气含量对产物的影响。结果表明,在一定条件下产生了金红石相和锐钛矿相的混合晶。随着氧气含量的增加,混合物中锐钛矿相的相对含量变大,但是,氧气含量足够时,生成的是中间产物和金红石相的混合粉体。颗粒呈球形(或类球形),颗粒尺寸变大(80~100nm),分散性变好,颗粒变得更均匀。 相似文献
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采用溶胶-凝胶法制备了纯TiO_2和不同浓度Fe掺杂TiO_2纳米粉末,并对各样品进行了350℃、500℃、650℃的热处理。通过SEM、XRD、EDS、XPS等测试方法对其表面形貌、晶体结构及成分组成进行了表征,研究了热处理温度对Fe掺杂TiO_2相变的影响。实验结果表明:纯TiO_2与Fe-TiO_2在350℃、500℃时均为单一的锐钛矿,650℃时大部分转变为金红石;热处理温度升高有利于锐钛矿向金红石的转变;Fe掺杂后以+3价的形式存在,Fe离子掺杂能够明显减小TiO_2的晶粒尺寸,高浓度的Fe掺杂对锐钛矿-金红石相变有微弱的促进作用。 相似文献
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FeS2/TiO2复合薄膜光电性能 总被引:1,自引:0,他引:1
采用溶液浸渍法在ITO导电玻璃表面的多孔TiO2薄膜上沉积了FeS2薄膜.使用Fe2O3粉末保护裸露在外的ITO导电膜在硫气氛中热处理后,制得了FeS2/TiO2复合薄膜.应用B531/H数显测厚指示表、数字式四探针测试仪、XJCM-8太阳电池测试仪等研究了FeS2/TiO2复合薄膜的厚度、ITO导电玻璃的电阻率以及FeS2/TiO2复合薄膜的光电性能.结果表明:此方法制得的FeS2/TiO2复合薄膜具有良好的光电性能;且ITO导电膜的电阻率变化较小.因而适宜制备色素增感太阳能电池(DSSC). 相似文献
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采用溶胶-凝胶法、分子模板法及旋转涂覆法在硅衬底上制备掺杂TiO2的SiO2薄膜,并采用差热分析(DSC-TGA)、红外吸收光谱(FTIR)、X射线衍射、小角衍射(SAXS)、原子力显微镜(AFM)、台阶仪(Atomic-Profiler)以及纸擦拭法(paper-wiping method)和胶带剥离法(adhesive tpe-stripping method)对薄膜的性能进行了分析与表征,结果表明,薄膜的最佳热处理温度为400℃,所制备的掺杂TiO2的SiO2薄膜为多孔结构的无定形态,具有较好的机械性能,平均孔径随着膜层的增加而减小,一层膜和两层膜的平均孔径分别为87.4nm和62.8nm,厚度分别为538.7nm和1032.3nm。 相似文献
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《Advanced Powder Technology》2020,31(3):1051-1059
Novel up-conversion luminescent SrGd2(WO4)2(MoO4)2: Yb3+/Tm3+/Ho3+ nano-crystals were synthesized by hydrothermal method. The composition ratio of rare earth had been investigated. It indicated that when CYb3+ = 10 mol% and CYb3+/CTm3+/CHo3+ = 10:1.5:2, the emission intensities were the highest. X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and up-conversion luminescence spectra were used to characterize SrGd2(WO4)2(MoO4)2: Yb3+/Tm3+/Ho3+ nano-crystals and they showed that the sample had high degree of crystallinity, the sample was tetragonal system, and the grain size of the sample was about 56 nm. Three emission peaks, including blue emission peak, green emission peak and red emission peak were observed at 477, 543 and 651 nm corresponding to 1G4 → 3H6 and 1G4 → 3F4 transitions of Tm3+, 5F4 → 5I8 and 5F5 → 5I8 transitions of Ho3+ respectively. All the emission peaks were observed by excitation of 980 nm semiconductor laser. The relationship between up-conversion intensity and excitation power revealed that blue emission at 477 nm was a three-photon absorption process, green emission at 543 nm and red emission at 651 nm was a two-photon absorption process. The quantum yields of the sample were near 3.2%. 相似文献
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The nanostructured multilayer silica–titania or silica–titania–alumina films doped with Er3+ were prepared by sol–gel method. The sol–gel method is a flexible and convenient way to prepare oxide films on several types of substrates, and for this reason it was extensively investigated for optical waveguides fabrication. The selected molar composition was 90%SiO2–10%TiO2 or 85%SiO2–10%TiO2–5% Al2O3 and 0.5% Er2O3.The films were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Spectroellipsometry (SE), as well as by Atomic Force Microscopy (AFM) and photoluminescence (PL). The films deposited on Si/SiO2 substrate by dip-coating or spin-coating, followed by annealing at 900 °C, presented homogenous and continuous surface and good adherence to the substrate. Differences were noticed in the structure and properties of the prepared films, depending on the composition and the number of deposited layers.Channel optical waveguides were obtained by patterning Er3+-doped SiO2–TiO2 and SiO2–TiO2–Al2O3 sol–gel layers deposited on oxidized silicon wafers. 相似文献
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2-DOF精密定位平台的几何误差分步辨识方法 总被引:1,自引:1,他引:0
针对一种2-DOF精密定位平台,基于误差迭代法与最小二乘法,提出一种几何误差分步辨识方法.对于给定的期望末端位置,采用迭代法计算出实际的主动关节位置,同时基于含有误差的精确的运动学逆解方程计算期望的主动关节位置,建立几何误差辨识方程;采用最小二乘法求解运动学模型中包含的所有几何误差.采用这种方法,只需测量末端平台沿X轴和Y轴方向的位置误差,即可辨识各种几何误差以及末端平台沿Z向的转动误差.实验结果表明,采用提出的几何误差分步辨识方法可有效补偿平台在平面内的位置误差,使其标定后的绝对定位误差小于6μm. 相似文献
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A mesh-free minimum length method (MLM) has been proposed for 2-D solids and heat conduction problems. In this method, both polynomials as well as modified radial basis functions (RBFs) are used to construct shape functions for arbitrarily distributed nodes based on minimum length procedure, which possess Kronecker delta property. The shape functions are then used to formulate a mesh-free method based on weak-form formulation. Both Gauss integration (GI) and stabilized nodal integration (NI) are employed to numerically evaluate Galerkin weak form. The numerical examples show that the MLM achieves better accuracy than the 4-node finite elements especially for problems with steep gradients. The method is easy to implement and works well for irregularly distributed nodes. Some numerical implementation issues for MLM are also discussed in detail. 相似文献