（Sn1-xCo2x）O2纳米拉子的制备及气敏性能研究

采用分析纯SnCl4·5H2O和NH3·H2O为主要原料,控制不同Co^2＋／Sn^4＋摩尔比,利用均匀共沉淀法制备了（Sn1-xCo2x）O2纳米粉体样品,并以白云母为基片利用厚膜工艺制得气敏元件。对样品的结构、结晶性能和活性等分析发现,Co件以类质同像的方式代替了SnO2晶格中的Sn^4＋,并引起了M—O键长、晶胞参数和M-O八面体电价平衡的非均一性,进而提高了粉体活性及n型半导体性能。在不同浓度H2中元件气敏性能测试表明,Co^2＋的引入提高了Sn02的H2灵敏度。元件的灵敏度与H2浓度之间具有较好的线性关系。实验得到了制备（Sn1-x,Co2x）O2气敏材料的最佳Co^2＋／Sn^4＋摩尔比。     

Cd2SnO4水热制备及其气敏性能研究

以SnCl4.5H2O、CdCl2·1/2H2O和NaOH为原料,采用水热法制备了Cd2SnO4粒子。通过XRD和SEM对其物相和形貌进行了分析,并将其制成气敏元件,进行气敏性能测试。结果表明制得的Cd2SnO4粒子为多面体,对乙醇、丙酮和三乙胺有较高的灵敏度和好的响应-恢复特性。     

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.     

花状SnO2的制备及其气敏特性的研究

以乙二醇(C2H6O2)为有机溶剂,采用溶剂热法制备了花状SnO2纳米材料,并将制备的SnO2制成旁热式气敏元件.通过XRD,SEM等测试手段对SnO2纳米材料进行了表征,并初步分析了气敏元件对丙酮的敏感机理.制备的SnO2材料是由粒径约为10 nm的颗粒有规则的堆叠而成的直径约为3～4μm的花瓣清晰的多孔分级花状结构.研究发现,气敏元件对丙酮气体有很好的响应灵敏度.在最佳工作温度(350℃)时,检测的丙酮体积分数最低为1×10-6.对100 ppm丙酮的响应及恢复时间分别为40和50 s.且气敏元件对丙酮气体的响应灵敏度远高于对苯、甲苯、甲醇、甲醛、氨等气体的响应灵敏度.     

钴掺杂二氧化锡溶剂热法制备及其气敏性能研究

以SnCl2·2H2O、CoCl2·6H2O和无水乙醇为原料,采用溶剂热法成功制备钴掺杂SnO2粉末。通过XRD、SEM和TEM对所得样品进行物相分析和形貌观察,并将其制成元件进行气敏性能测试。结果表明:所制备的钴掺杂SnO2粉末为四方相金红石结构,钴离子的掺入并没有改变SnO2的晶体结构,对SO2气体具有较高的灵敏度和较好的响应—恢复特性。     

掺杂型SnO2薄膜对乙醇的气敏特性

以SnCl4·5H2O、Ce(NO3)3·6H2O、CuCl2·2H2O、La(NO3)3·6H2O为原料,柠檬酸为络合剂,采用sol-gel法,浸渍提拉技术制备了纯SnO2及其掺杂薄膜.利用XRD分析方法进行了物相结构分析,研究了掺杂比对各掺杂SnO2薄膜元件气敏特性的影响.发现掺杂比相同时,掺杂Ce3+的SnO2样...     

sol-gel法制备的SnO_2-TiO_2厚膜及其气敏特性研究

采用sol-gel法,以钛酸丁酯、四氯化锡为前驱体制备了不同掺杂量的Sn O2-Ti O2纳米粉末,样品经300,500,700和900℃退火后,利用浸渍提拉法,在Al2O3陶瓷管表面制备了Sn O2-Ti O2厚膜。通过XRD和SEM对制备的纳米粉末的物相、形貌进行表征,静态配气法对其气敏性能进行测试,并结合分子轨道理论探讨了气敏机理。实验结果表明,经700℃退火的4%(原子分数)掺杂的Sn O2-Ti O2气敏元件,对乙醇气体具有很好的选择性,在工作温度为63℃时,对乙醇气体的灵敏度可达1 903,响应-恢复时间分别为1和3 s,所制备的气敏元件有望用于乙醇气体的实用化检测。     

SnO_2-TiO_2的制备及气敏性能研究

以SnCl4·5H2O和钛酸四丁脂为原料,采用Sol-Gel法制备SnO2-TiO2材料。运用XRD、TEM对SnO2-TiO2粉体的物相、形貌和结构进行表征。并测试其气敏性能。实验结果表明:SnO2-TiO2纳米粉体在3.5 V加热电压下对100 ppm乙醇的灵敏度为464.116。     

金属离子掺杂纳米SnO2材料的气敏性能及掺杂机理

以SnCl4·5H2O为原料合成纳米SnO2,并以其为基底材料分别以离子形式掺杂Ag^＋、Ni^2＋、Ce^3＋、Sb^2＋等作为气敏材料,制作旁热式气敏元件．研究了其对甲醇、乙醇气体的气敏性能．结果发现,适量的金属离子掺杂可提高SnO2的气敏性能,其中掺Ag^＋效果最佳,可显著提高SnO2对甲醇、乙醇气体的灵敏度．在工作温度为360℃时,对体积浓度为400×10^-6的乙醇、甲醇气体灵敏度分别为121和66．掺Sb^2＋可提高SnO2的导电性,在温度为200℃时,电阻值由180kΩ降至4kΩ．用Materials Studio软件对掺杂不同金属的SnO2的能带结构进行了理论计算,分析表明,掺杂使SnO2能带带隙宽度由掺杂前的2．65eV减少为2．02～2．62eV,相应元件电阻阻值的减少与带隙宽度变化趋势一致,带隙宽度是影响SnO2传感器工作温度高低的重要因素．     

纺丝法制备多级SnO2纳米纤维及其气敏特性研究

为了提高SnO2的气敏性能,以PVP为有机溶剂,采用静电纺丝法制备了多级结构的SnO2纳米纤维,利用XRD,SEM和TEM等技术对材料的结构、形貌进行了表征,并制备了SnO2旁热式气敏元件.采用静态气体测试系统对SnO2元件进行了气敏测试.在工作温度300℃时,对0.5~50 ppm甲醛进行了气敏测试.测试结果表明:SnO2气敏元件对甲醛气体具有优异的响应灵敏度,快速的响应及响应恢复特性、较好的选择性.采用静电纺丝制备的多级结构SnO2纳米纤维对甲醛表现出良好的气敏特性.     

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.     

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.     

Thermal diffusion in binary mixtures H2-CCl2F2 and H2-CHClF2

Thermal diffusion coefficients were measured in two gaseous mixtures, in which one component was close to the critical temperature, in the pressure range (19.6–127.4)·10⁴ N/m² and at a freon concentration of 0.25–0.8.     

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.     

Radial GRIN glasses in Li2O-Na2O-Al2O3-TiO2-SiO2 systems

A series of GRIN glass rods have been developed in Li2O-Na2O-Al2O3-TiO2-SiO2 systems. Negative radial refractive index profiles were generated by exchanging Na+ for Li+ ions in these glass rods. It has been observed that TiO2 plays a vital role in increase in the profile depth and maximum change in the refractive index because of its ambivalent nature. Change in the refractive index can be further increased by increasing the concentration of exchanging cation in the base glass.     

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.     

Si_2N_2O-Al_2O_3-La_2O_3和Si_2N_2O-Al_2O_3-CaO系统的亚固相关系

本文给出了 Si_2N_2O-Al_2O_3-La_2O_3和 Si_2N_2O-Al_2O_3-CaO 系统的亚固相图。实验结果表明:在 Si_2N_2O-Al_2O_3-CaO 系统中有一个未知结构的新化合物 CaO·Si_2N_2O,在3CaO·Si_2N_2O 和3CaO·Al_2O_3两化合物之间形成连续立方固溶体。而 Si_2N_2O-Al_2O_3-La_2O_3系统中则没有发现新化合物。在两个系统的富 Si_2N_2O区,过量的 Si_2N_2O 与 La_2O_3和 CaO 分别反应形成 Si_3N_4与 La_(10)[SiO_4]_(?)N_2(H-相)(和 CaSiO_3。所研究的这两个三元系统中,分别形成了如下几个四元相容性区。在 Si_2N_2O-Al_2O_3-La_2O_3系统内有:H-Si_3N_4-La_2O_3·Si_2N_2O-La_2O_3·Al_2O_3;H-Si_3N_4-La_2O_3·Al_2O_3-La_2O_3·11 Al_2O_3;H-Si_3N_4-La_2O_3·11 Al_2O_3-Al_2O_3;H-Si_3N_4-Al_2O_3-O′s.s;H-Si_3N_4-O′s.s-Si_2N_2O在 Si_2N_2O-Al_2O_3-CaO 系统内有:Si_3N_4-CaSiO_3-CaO·Si_2N_2O-3CaO·Al_2O_3;Si_3N_3-CaSiO_3-3CaO·Al_2O_3-2CaO·Al_2O_3·SiO_(?);Si_(?)N_(?)-CaSiO_3-2CaO·Al_2O_3·SiO_2-Al_2O_3;Si_3N_4-CaSiO_3-Al_2O_(?)-O′s.s;Si_3N_4-CaSiO_3-O′s.s-Si_(?)N_(?)O