Ln1-xSrxCoO3-y纳米晶厚膜型气敏传感器的研究

研究了纳米晶Ln     

纳米晶稀土复合氧化物Dy_(1-x)Sr_xCoO_(3-y)低温形成机理研究

采用溶胶—凝胶工艺制备了纳米晶氧化物Ｄｙ１－ｘＳｒｘＣｏＯ３－ｙ，并对其低温形成机理进行了研究，结果表明：１００～２００℃柠檬酸配体变化不大；３００℃时配合物已开始分解，生成了单齿碳酸盐，同时形成了ＳｒＣｏＯ３－ｙ晶相骨架；４００℃晶化过程出现微区不均匀性；一级相变吉布斯自由能一阶偏微熵的改变，体现为结晶放热过程，整个晶化过程处于一种氧缺陷状态；７００℃时已形成纳米晶氧化物Ｄｙ１－ｘＳｒｘＣｏＯ３－ｙ，低于传统的合成温度。     

酒石酸辅助水热合成纳米MoO_2及其优异的乙醇气敏特性研究

以钼酸铵为原料,利用酒石酸辅助水热法一步合成了球状纳米结构的MoO_2,利用XRD和TEM对样品的结构、微观形貌进行分析。将样品制成旁热式气敏元件,并对其气敏特性进行了测试。研究结果表明,酒石酸在水热合成过程中对产物的形貌和相行为起决定性的作用,而且对气敏材料的气敏性影响显著。取适量的酒石酸,可有效提高传感器的灵敏度。在260℃工作温度下,MoO_2纳米球气敏元件对10×10~(-6)乙醇气体的灵敏度达3.9,并具有良好的选择性。     

镍氢电池负极用纳米晶稀土贮氢合金的性能研究

对采用双辊快淬法制备的纳米晶稀土贮氢合金Ml(NiCoMnAl) 5相结构、贮氢性能和电化学充放电性能进行了研究分析。X射线衍射分析 (XRD)结果表明 ,合金片由均匀的CaCu5相组成 ,其晶粒尺寸平均为 2 0～ 40nm。PCT测试表明 ,该合金具有很好的平台特性和较小的滞后效应。将合金粉压成极片组装成模拟电池以 3 0 0mA·g- 1 (1C)电流充电 ,分别以 2 0 0 0mA·g- 1 (7C)和 3 0 0 0mA·g- 1 (10C)电流放电至 0 .9V和 0 .8V ,其电化学容量分别达到 2 5 0和 2 3 0mAh·g - 1。在 7C放电情况下 ,经 45 0循环后 ,容量衰减率小于 2 0 %。     

石墨烯复合材料用于气敏传感器的研究进展

石墨烯(Graphene)自发现以来,凭借其出色的二维蜂窝的网状平面结构获得了良好的导电性、导热性,运用领域越来越广泛,也为各方面的科研提供了一系列创新思路。总结了石墨烯在气敏传感器领域的创新思路以及目前的发展概述和未来的展望。石墨烯独特的蜂窝网状结构对气体具有良好的吸附能力和在简单条件下的脱附能力,并且良好的导电能力使得待测气体在接触石墨烯表面时会发生电子交换改变石墨烯的电阻,而石墨烯为基的气敏传感材料正可以利用这个细小的变化来测量待测气体的浓度。为提高石墨烯的气敏特性,目前研究大多在石墨烯表面通过掺杂其他金属离子或者金属氧化物,以及有机高分子材料来提高石墨烯复合气敏材料的气敏特性。     

纳米W、Cu固溶行为的研究

采用溶胶-喷雾干燥-热还原法制备了纳米W-Cu复合粉末,用日产3014-2Z型X射线自动衍射仪对W-Cu复合粉末和烧结坯进行物相分析。通过衍射图谱可以观察到经三步还原后的W-Cu复合粉末,存在W相和Cu相,通过精确测量各晶面所对应的衍射角,并采用标准Si校正,得到各种粉末和烧结坯中W相和Cu相的晶格常数,结果表明:这些数值与其分别对应的标准晶格常数0.3165 nm和0.3615 nm相比,出现一定偏差,说明W相和Cu相均存在一定的固溶,在烧结过程中,随着烧结温度的升高,W在Cu中的固溶度逐渐增大。     

温度和湿度对Nafion膜氢传感器性能的影响

系统研究了以Nafion112膜为电解质的氢传感器在不同工作环境下的氢敏感性能.结果表明,以Nafion112膜为电解质的氢传感器对氢具有很好的敏感性,可以实现微量氢气泄漏的快速检测.该传感器在氢气体积分数为(500～3000)×10^-6时的响应电压与氢气体积分数的对数呈线性关系,为标定不同环境下氢气含量与传感器响应电压的对应关系提供了依据.在相同湿度条件下,传感器响应电压随温度的升高而下降.湿度对传感器响应电压的影响与温度相关:温度较低时,响应电压随湿度的增加而下降;温度较高时,响应电压随湿度的增加而升高.     

Cd（Ⅱ）掺杂TiO2多孔纳米晶膜电极的表征及其光电化学行为

利用Ｘ射线粉末笛射法和原子力显微镜对镉掺杂的ＴｉＯ２纳米晶膜电极作了表征，并用光电化学方法测定了该电极的光电化学行为。实验发现光镉的掺杂量低于１５％时，镉与ＴｉＯ２形成固熔体，掺杂量高时出现ＣｄＴｉＯ３的独立相；随着镉含量的增加，纳米晶颗粒逐渐变大（粒径从１０ｎｍ和２０ｎｍ）。镉含量的多少直接影响光电流的大小符号，当Ｃｄ含量（相对于Ｔｉ的质量分数）为５％时光电流最大，外加电压为０．３Ｖ时光电流比纯     

氧化铈掺杂对氧化铟气敏特性的影响

用微乳液法合成了纳米In2O3粉体,浸渍法制备了掺杂CeO2的氧化铟.利用 X射线衍射、透射电镜对氧化铟的结构和形貌进行了表征;采用静态配气法对氧化铟的气敏特性进行了测试.结果表明,微乳液法合成的氧化铟在600℃煅烧1h后,颗粒尺寸约20nm,且分布均匀.未掺杂的氧化铟气敏元件对汽油有较高的灵敏度,但选择性不是太好;氧化铈掺杂后,在加热电压为3.5V～4.5V范围内,较大地提高了汽油的灵敏度和选择性,尤其当加热电压为4.0V,掺杂量为5%(质量分数)时,灵敏度从9.0提高到40.4,汽油对丁烷的选择性系数为30.9,汽油对乙醇的选择性系数可达到11.5.     

纳米La_2O_3粉晶的制备及其表征

以La(NO_3)_3·6H_2O、NH_4HCO_3和聚乙二醇为原料,利用沉淀法制备了纳米La_2O_3粉体,利用XRD,TG-DTA和TEM等测试方法对干凝胶热分解过程及最终形成的纳米La_2O_3粉体进行了分析和表征,XRD法考察了前驱体在不同热处理条件下产物物相和晶粒度的变化情况,实验结果表明,在适当工艺参数下,前驱体经720℃,1h焙烧所得产物为平均粒径小于50nm的La_2O_3粉体.     

CeO_2纳米薄膜的光声光谱研究

本文以Ｃｅ（ＮＯ３）３·６Ｈ２Ｏ为前驱物，火棉胶为添加剂，用ｓｏｌ－ｇｅｌ提拉法制备ＣｅＯ２透明薄膜。本方法成膜均匀，重复性好。薄膜的结晶性质和光谱性质研究表明，薄膜中ＣｅＯ２为纳米粒径，具有强烈的量子尺寸效应和表面效应。     

铂粉物理特性对厚膜铂电阻温度系数的影响

采用化学还原方法制备3种超细铂粉,通过对铂粉物理特性的测试和微观结构分析,解释了引起电阻温度系数(TCR)变化的原因。发现粒度分布为0.1~0.6μm,比表面积1.45m2.g-1,松装密度0.85g.cm-3,表面光滑的2#球形铂粉,用于制作厚膜铂电阻温度传感器生产工艺可行,电阻温度系数达到380×106.℃-1,是一种理想的电阻材料。     

纳米晶Al-Cu-Mg合金的微观组织与力学性能研究

以工程实际中应用较广的Al-Cu-Mg铝合金作为研究对象, 用Al-Cu-Mg铝合金气体雾化粉末作为原材料, 通过低温液氮球磨获得纳米晶后, 再经真空热压和热挤压制备了致密的大块体纳米材料. 通过力学性能测试, 挤压态的纳米晶Al-Cu-Mg块体材料抗拉强度达470 MPa, 经过T4处理后, 抗拉强度达到590 MPa, 远远超过常规方法制备的Al-Cu-Mg铝合金抗拉强度. 对纳米晶Al-Cu-Mg块体材料进行微观组织观察, 分析了材料强度提高的原因.     

Effect of Residual Stresses on Electrophysical Properties of High-Ohmic Thick Films Based on SnO 2 ― Sb

We have studied the effect of a mismatch between the thermal coefficients of linear expansion for the current-conducting phase and the glass on the electrical properties of composite thick films based on Sn_0.93Sb_0.07O₂. The physical explanation of the results obtained is connected with the appearance of residual stresses in the film on cooling during heat treatment.     

用酒石酸凝胶法制备LaFeO3纳米晶

用酒石酸溶胶-凝胶法制备出纳米LaFeO3材料,粒径30～10nm。用X射线衍射仪和透射电子显微镜对材料的结构、粒径进行了分析和表征。     

Synthesis of Nanocrystalline La1-xSrxCrO3 by Sol-Gel Method

The nanocrystalline La1-xSrxCrO3 was prepared by sol-gel method using La( NO3 )3 · 6H2O, Sr( NO3 )2 and respectively. The phase transformation from dry-gel to crystal was investigated by means of TG, DSC and XRD. Influences of temperature and Sr quantity on particle-diameters were observed by HREM. The experimental results show that the best calcined temperature is near 800 ℃. The particle-diameters decrease with the increase of Sr quantity. The chromite phase formed continuously during crystallization process, which is mainly composed of four steps: ( 1 ) Carbonates first formed by decomposing metal citrates. (2) The decomposition of carbonates occurred metal oxides. (3) La0. 9Sr0.1 CrO4 were synthesized by the reaction of metal oxides. (4) Chromite phase formed lastly due to the decomposition of chromate phase.     

水溶液中电沉积Fe-Zr-B纳米合金

在酸性镀液中电沉积了Fe-Zr—B纳米合金。讨论了影响镀层组分的因素。用原子吸收光谱和分光光度法分析了铰层组分，线性扫描和循环伏安法研究了电极过程。实验结果表明，甘氨酸和二甲基甲酰胺(DMF)抑制了铁的沉积，沉积机制可能是诱导共沉积。电镜扫描图像表明镀层粒子是纳米粒子，XRD分析表明镀层含有Fe-Zr合金。     

Formation of Nanocrystalline Structure of TaSi2 Films on Silicon

The nanocrystalline structure and mechanical properties of TaSi₂ films deposited by sputtering of TaSi₂ target have been investigated by x-ray diffraction, cross-sectional transmission electron microscopy (TEM), four-point electrical resistance measurement, and cyclic depth-sensitive nanoindentation. The purpose of this work is to study the formation of nanocrystalline structure in TaSi₂ films on a silicon substrate. As revealed, a decrease in the deposition rate leads to an increase in the O and C impurity content in the films. Contamination of the film by O and C atoms during a low-rate deposition causes the formation of an amorphous phase in the deposited films. Upon annealing, the amorphous structures crystallize into mixtures of disilicide and a small amount of polysilicide, i.e. TaSi₂ and Ta₅Si₃, respectively. After annealing at 970 K, the formation of a nanocrystalline structure with a grain size about 10 nm takes place in the film produced at a deposition rate of 0.2 nm/sec. The formation of a nanocrystalline structure changes drastically the mechanical properties of the film. The nanohardness and elastic modulus increase significantly, and the film becomes brittle and overstressed. After deposition in the film produced at the 1 nm/sec deposition rate mainly Ta disilicide and the amorphous phase are observed. After annealing, the amorphous phase near the Si substrate coexists with column-shape grains of Ta disilicide of size 150 × 500 nm. The annealed thin film becomes nonuniform in thickness. The nanohardness and elastic modulus increase.     

Influence of the Phase Composition on the Electrical Conductivity of Gas Sensors Based on Antimony-Doped Tin Dioxide Films

Scanning electron microscopy is used to examine the structure (of thin- and thick-film gas sensors based on Sn_1x Sb _x O₂ solid solutions. The solid-solution particles are found not to sinter. The temperature dependences of the resistance and the volt-ampere characteristics of the films are studied. A mechanism for the gas sensitivity of the films to gas is suggested. In the model presented electrons are transported across grain-boundary Schottky barriers by thermoelectron emission and tunneling.