C/SnO2/TiO2纳米复合物的制备及其电化学性能研究

通过碳化吸附在SnO2/TiO2电极上的葡萄糖制备出C/SnO2/TiO2纳米复合电极材料。采用晶体粉末衍射仪(XRD)、场发射扫描电镜(SEM)、X射线能谱分析(EDS)等手段对复合电极进行了表征。将复合电极作为锂离子电池负极材料,通过循环伏安和计时电位法研究了其电化学性能。结果表明,在大的电流密度200μA·cm-2下循环30次后,放电容量仍保持在120.1μAh·cm-2。相比SnO2/TiO2电极,C/SnO2/TiO2复合电极电化学性能显著提高,交流阻抗谱图也显示C/SnO2/TiO2纳米复合材料拥有更低的电荷转移电阻。     

锡锑氧化物中间层对钛基阳极氧化MnO2电极性能的影响

将锡锑氧化物用作钛基MnO2电极的中间层可改善电极性能,目前在钛基锡锑氧化物中间层上多采用热分解法制备MnO2层制成电极,而很少采用电化学方法.为此,先在钛片上涂及SbOx + SnO2中间层,然后在其上在MnS04溶液中阳极氧化制备MnO2层,最终制成Ti/SbOX + Sn02/MnO2电极,通过暂态和稳态动电位极...     

SnO2添加剂对AgCuOIn2O3复合材料电接触性能的影响

采用反应合成法结合塑性变形工艺制备了不同SnO2含量的AgCuOIn2O3SnO2电触头材料,在JF04C触点材料测试机上对不同SnO2含量的电触头材料进行电接触实验,研究了该材料的接触电阻、抗熔焊性和材料转移特性,并通过扫描电镜对试样阴/阳表面电侵蚀下的微观形貌进行了分析.结果表明AgCuOIn2O3SnO2触头材料...     

钛基Co中间层SnO2电催化电极的制备及性能研究

为提高钛基二氧化锡电极的稳定性,设计并制备了含Co中间层的钛基二氧化锡电催化电极Ti/Co/SnO2,以苯酚为目标有机物,考察了所制备Ti/Co/SnO2电极电催化氧化降解苯酚的性能,并采用SEM、EDX以及XPS等检测方法分析了Ti/Co/SnO2电极表面的形貌、元素组成及元素化学态.研究结果表明,含有中间层的Ti/Co/SnO2电极其使用寿命较不含中间层的钛基二氧化锡电极Ti/SnO2大幅度提高,但其对苯酚的电催化降解活性有所下降,氧化还原电对Co2 /Co3 的存在是所制备Ti/Co/SnO2电极稳定性及电催化活性改变的主要原因.     

纳米SnO2/TiO2复合粉体制备及其红外特性研究

以溶胶-凝胶方法制备纳米SnO2/TiO2复合粉体,并用XRD、TEM等方法对其进行了表征,给出了相关的工艺参数.研究了纳米SnO2及SnO2/TiO2复合材料的红外吸收特性.结果表明,本文制备的纳米SnO2/TiO2复合材料在4000～1500cm-1和1000～400cm-1范围内有较好的红外吸收.     

La掺杂AgSnO2触头材料的电性能

由于Cd有毒性,AgSnO2触头材料逐渐取代了 AgCdO 成为新型触头材料,但由于AgSnO2触头材料中的SnO2近乎绝缘,使得触头材料的接触电阻增大,故改善SnO2的导电性是急需解决的重大难题.本文提出了一种简单的、低成本的La掺杂AgSnO2触头材料的设计方法.采用模拟计算的方法,利用第一性原理的密度泛函理论平面波超软赝势法,建立了SnO2以及不同比例La掺杂的SnO2超晶胞模型,在对其进行几何优化之后分别研究了 La掺杂比为50%、25%、16. 67%、12. 5%、8.34% 的SnO2材料的电子结构,并研究了其晶格参数、能带结构和态密度等.结果表明,掺杂后材料晶胞体积变大. La的5d轨道进入导带,使得导带底向低能端移动,禁带宽度变小.最终得出La掺杂比为16.67% 时导电性最佳.最后进行了不同掺杂比下触头材料的电接触性能试验,得到了接触电阻和燃弧能量等电接触性能参数并验证了模拟结果.因此,本文的研究为触头材料的发展和应用提供了理论依据.     

Gd0.2Ce0.8O2包覆LaNi0.6Fe0.4O3-δ阴极材料抗铬污染性能

应用丝网印刷和共烧结制备LaNi_0.6Fe_0.4O_3-δ (LNF)/Sc_0.1Zr_0.9O_1.95(ScSZ)/LaNi_0.6Fe_0.4O_3-δ 对称电池.以硝酸铈和硝酸钆为原料、柠檬酸为燃料,采用燃烧法制备质量分数为21.3%的Gd_0.2Ce_0.8O₂(GDC)包覆的LNF阴极.电化学阻抗谱(EIS)表明:在750 ℃工作温度下,当无Cr基合金接触时,质量分数21.3%的GDC包覆的LNF经过1 200 h的搁置,其极化电阻由0.13 Ω·cm²增加至0.40 Ω·cm²,而纯LNF经过500 h的搁置,极化电阻由0.70 Ω·cm²增加至2.36 Ω·cm²,GDC的包覆加速了气体/阴极/电解质三相界面反应区的扩散过程,降低了阴极极化电阻;当有Cr基合金接触时,相对于质量分数为21.3%的GDC包覆的LNF阴极,LNF/ScSZ界面处沉积出大量Cr₂O₃,减缓了活性粒子在三相界面处的扩散,故其极化电阻远大于相同条件下质量分数为21.3%的GDC包覆的LNF阴极的极化电阻,质量分数为21.3%的GDC包覆的LNF阴极具有较佳的抗铬污染性能.     

纳米SnO2-TiO2复合材料的氢敏性能及气敏机理

以钛酸正丁酯和SnCl4·5H2O为前驱体,采用溶胶-凝胶法制备了SnO2及Sn/Ti摩尔比为5/1的SnO2-TiO2复合纳米材料,并以此复合材料制备了旁热式气敏传感器,对两者的氢敏性能做了比较,利用第一性原理对其气敏机理进行了理论分析.结果表明,TiO2的掺杂使SnO2导带底部产生了掺杂能级,使SnO2元件电阻下降,并随温度的上升出现先快速下降后缓慢下降2个过程.SnO2-TiO2元件对H2的灵敏性明显优于SnO2元件.吸附H后的SnO2电子态密度变化较小,而SnO2-TiO2的电子态密度则有明显变化,并产生了掺杂能级,导带负移,促进了能带间的电子转移.     

SnO2纳米薄膜的溶胶-凝胶法制备及气敏性能

以SnCl2·2H2O和无水乙醇为原料制备SnO2透明溶胶,通过浸渍法在云母基片上制备了SnO2纳米薄膜.利用XRD和AFM手段研究了薄膜的结构和形貌,结果表明,SnO2纳米薄膜的球形粒径约为15nm;随着薄膜沉积层数的增加或工作温度的升高,薄膜电阻逐渐减小.气敏特性研究表明,薄膜对H2有较好的敏感性.     

耐负荷的Ag-Cu-C-SnO2触头材料的制备

将一定比例的Cu、石墨、SnO2粉末混合装入7根纯铜管内,封口后再以密排方式装入一银管中.采用多次挤压-拉拔连续纤维复合工艺制备出了Ag-Cu-C-SnO2复合触头材料.用金相显微镜观察了材料组织结构,测试了材料的机械性能、电性能等,并进行了寿命试验.结果表明,多次挤压-拉拔工艺可以制备连续纤维化的Ag-Cu-C-SnO2复合材料,其接触电阻稳定,有较好的抗熔焊性和抗电弧烧损性.材料经直流28 V,40 A电负荷下,工作寿命之在3 000次以上,可在大、中负荷下的多种继电器、接触器上得到应用.     

Preparation of ZrO2-CeO2 and HfO2-CeO2 nanopowders

We prepared weakly agglomerated powders of ZrO₂-CeO₂ and HfO₂-CeO₂ solid solutions 5–8 nm in particle size, consisting of monoclinic and tetragonal phases. After heat treatment at 1200°C, the crystallite size was 30 and 14 nm, respectively. We also examined the effect of precipitate freeze drying on the crystallization of hafnia-based solid solutions containing up to 20 mol % CeO₂.     

Comparison of the Electronic Structures of La2CuO4, Sr2CuO2Cl2, and Sr2CuO2F2

First-principles cluster calculations are reported of the local electronic structure of the three compounds: La₂CuO₄, Sr₂CuO₂Cl₂, and Sr₂CuO₂F₂. The copper ${\text{3d}}_{x^2 - y^2 } $ and the planar oxygen 2p _σ atomic orbitals exhibit a similar degree of covalency. The out-of-plane orbitals, however, are quite different with the ${\text{3}}d_{3z^2 - r^2 } $ atomic orbital lowered significantly in energy for chlorine and fluorine apical positions.     

Thermoelectric power of single-phase samples of Tl2CaBa2Cu2O y and Ba2CaSr2Cu2O y

Single-phase 2122 samples of thallium and bismuth superconductors were made by the precursor matrix method. The thermopower of these samples was measured in the temperature range 250 K-T _c . The thermopower was positive and decreased linearly with increasing temperature aboveT _c (onset). The exponential enhancement of thermopower seen in the undoped and doped YBCO was not observed in these samples. The linear variation of thermopower can be explained on the basis of either a two-band model or a narrow band model.     

VLE data for CO2-CF2Cl2, N2-CO2, N2-CF2Cl2 and N2-CO2-CF2Cl

Knowledge about vapour-liquid (VLE) is required as a basis of reliable calculations for separation processes. Correlations available for the prediction of T, p, x, y data are less accurate for mixtures at high pressures and mixtures containing supercritical components. The results of VLE experiments are reported and compared with data calculated with equations of state.     

SiO2—TiO2—ZrO2系涂层的制备及其特性

用溶胶－凝胶法（sol-gel method）在不锈钢表面制备了SiO2-TiO2-ZrO2系无机氧化膜（STZ）。用DTA／TG、IR、XRD和SEM等手段研究了涂层制备时由凝胶向玻璃态的转变以及涂层薄膜的显微结构特点，考察了涂层对基体的保护效果。试验结果表明，在溶胶至凝胶最终转变为无机氧化物的过程中形成了无机网络，Si^4 和Zr^4 充当了网络骨架的形成离子。涂层为无定型玻璃态，其间混有石英、锐钛矿或金红石等微晶。     

Structure of Na2O·2TiO2 glass

X-ray radial distribution analysis and Raman spectroscopic measurement were carried out on Na₂O-2TiO₂ glass prepared by twin-roller quenching method. It is found that four-coordinated Ti⁴⁺ ions may be predominant over six-coordinated ones in the present glass. It is also found that the fraction of six-coordinated Ti⁴⁺ ions is larger in the present glass than in K₂O·2TiO₂ and Cs₂O·2TiO₂ glasses. Poorer glass-forming ability of the Na₂O-TiO₂ system compared with the K₂O-TiO₂ and Cs₂O-TiO₂ systems is ascribed to a larger fraction of TiO₆ octahedron for the former system.     

Elastic and Electronic Properties of Superconducting CaPd 2 As 2 and SrPd 2 As 2 vs. Non-superconducting BaPd 2 As 2

The first-principles calculations were performed to predict the elastic and electronic properties of the superconducting ThCr₂Si₂-type phases CaPd₂As₂ and SrPd₂As₂ in comparison with the non-superconducting CeMg₂Si₂-type phase BaPd₂As₂. Besides, the same properties were compared for CeMg₂Si₂- and ThCr₂Si₂-type polymorphs of BaPd₂As₂. We found that all these phases are mechanically stable and belong to soft materials with low hardness. The near-Fermi region is formed by the valence states of the blocks [Pd₂As₂] with decisive contributions of Pd 4d states. The values of N(E _F) increase in the sequence: CaPd₂As₂ < SrPd₂As₂ < BaPd₂As₂, i.e. in the reverse sequence relative to the transition temperatures T _C. Thus, the change in T _C cannot be explained by the electronic factor, i.e. by the simple correlation T _C～N(E _F). Most likely the decrease in T _C in the sequence CaPd₂As₂ → SrPd₂As₂ and the absence of a superconducting transition in BaPd₂As₂ are related to the structural factors and the peculiarities of the electron–phonon coupling mechanism.     

掺杂Bi_2Ti_2O_7对Y_2O_3-2TiO_2系微波介质陶瓷材料性能的影响

目前国内外对εr范围在40～80左右的中介电常数微波介质陶瓷体系的研究还很缺乏。为适应现代微波通讯技术发展需求,本实验研究开发了新型中介电常数Y2O3-2TiO2系微波介质陶瓷,并在此基础上添加Bi2Ti2O7陶瓷粉料进行复相掺杂。利用网络分析仪,阻抗分析仪,XRD,SEM等方法,本文重点研究了不同Bi2Ti2O7掺杂量对Y2O3-2TiO2系微波介质陶瓷材料烧结性能和介电性能的影响。通过分析发现适量掺杂能够有效降低材料的烧结温度,并使材料致密化。同时由于Bi3+置换主晶相中的Y3+形成了固溶体,材料主晶相为烧绿石结构并未改变。当添加质量分数为8wt%时获得介电性能较好的陶瓷材料,烧结温度从未掺杂的1460℃降低到1320℃。在1M下:εr≈62.14,tanδ≈1.22×10-3,微波频率(4.55GHz)下εr≈62.85,Q.f=4122.8GHz,τf=-7ppm/℃。     

Investigation of Instability of Lattice of Bi_2Sr_2CaCu_2O_x

Bi2Sr2CaCu2Ox superconductor was studied by differential scanning calorimetry (DSC) and thermogravimetry (TG) in different atmospheres. It is discovered that there is a thermal anomaly in the DSC curve, associated with a weight loss in the TG curve before the melting of the sample. Careful thermal analysis and high temperature X-ray diffraction reveal that the thermal anomaly and the weight loss show an instability of the crystalline Iattice. By annealing the sample in oxygen and argon, respectively and then by TC measurement and thermal analysis, the coincidence of transition temperature with the instability is found. The coincidence is further confirmed by Y-doped 2212 phase.