WO_(3)敏感电极的制备及其性能研究北大核心CSCD

迈向微型化、集成化及具有高选择性和灵敏度的固体电解质气体传感器已成为未来的发展趋势。文章采用磁控溅射法成功制备了WO_(3)气体传感器敏感电极材料,并通过X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)等表征手段研究了WO_(3)的结构、成分和形貌并测试了该气体传感器对NO_(2)的气敏性能。XRD结果表明,当退火温度大于400℃时,WO_(3)出现(200)衍射峰,且该衍射峰随退火温度增加而显著增强,表明WO_(3)结晶质量增加。SEM测试结果表明,随着退火温度的升高,薄膜的晶粒尺寸逐渐增大。当退火温度达到500℃时,采用谢乐公式计算其晶粒尺寸达到23 nm。EDS结果表明,退火温度对薄膜的成分也有较大影响,O:W原子比例呈现增大趋势,由2.7增加到3.2,这与XPS结果相符合。通过高温气敏性能测试表明,所制得的WO_(3)敏感电极对NO_(2)表现出了明显的气体响应。本研究为制备微型化、高选择性和灵敏性的固体电解质气体传感器提供了一定的研究基础。     

微波辅助制备Pt/WO_3用于生物标志物丙酮的检测

通过微波辅助溶剂热法一锅制备了贵金属Pt修饰的WO_3(Pt/WO_3),并将该材料应用于呼吸生物标志物丙酮的检测。实验结果表明,相比于纯相WO_3,贵金属Pt修饰的WO_3明显提高了材料对于丙酮气体的响应的灵敏度,并且当反应溶液中加入0.25 mL 0.1 mol/L的氯铂酸乙醇溶液时得到的材料(Pt/WO_3-2)对丙酮的气敏性能提高最为明显,提高了23倍。Pt/WO_3-2对丙酮检测的下限低至250 ppb。Pt/WO_3-2表现出对丙酮气体的良好的选择性和长期稳定性。本实验采用的微波辅助溶剂热法一锅制备贵金属修饰的氧化物的方法,为后续构筑高性能传感器提供了一种新的思路。     

La2O3/WO3平面VOCs气体传感器的研究

采用厚膜工艺制备平面气敏元件并通过溶胶-凝胶法制得纳米三氧化钨(WO_3)粉体,然后加入了不同用量的三氧化二镧(La_2O_3)为敏感材料,制得La_2O_3/WO3,并对样品进行了测试。研究发现,适量的La_2O_3的添加抑制晶粒的增长,提高粉体材料的气敏性能,其中La_2O_3用量为10%(wt,质量分数)制得的La_2O_3/WO3传感器,在3.5V工作电压条件下,对浓度为10×10-6乙醇、丙酮、苯和二甲苯的响应电压分别为1.7V、2.0V、1.5V和2.0V,传感器响应-恢复时间比较迅速,响应和恢复时间分别为5s和15s。     

基于磁控溅射的金属氧化物气敏薄膜的研究进展

气体传感器的应用越来越广泛,对气敏材料的研究也越来越深入。磁控溅射法是生产气敏薄膜的一种主要方法,本文重点介绍了用磁控溅射法制备的几种金属氧化物薄膜(SnO2、WO3、ZnO、TiO2、In2O3和NiO等)的气敏性能及其研究进展,对其它薄膜做了简要概述,并提出了目前在气敏薄膜研究中存在的问题。     

氧化钨基半导体气体传感器的研究进展

近年来,氧化钨(WO_3)基半导体气体传感器由于可用来检测低浓度二氧化氮、二氧化硫、臭氧和氨气等气体而受到广泛关注。将WO_3基材料分为4类:纯WO_3材料、氧化物-WO_3复合材料、贵金属-WO_3复合材料和有机物-WO_3复合材料,总结近年来中外文献中WO_3基材料对不同气体的响应性能,展现近年来国内外WO_3基半导体气体传感器的研究进展。最后根据已有的工作进展,提出合成新型纳米材料、降低工作温度、提高传感器选择性应成为WO_3基半导体气体传感器下一阶段的研究重点。     

CuO在气敏传感器中的应用研究进展

综述了近年来CuO在气敏传感器中的应用研究进展,主要包括纳米结构CuO作为主体传感材料以及掺杂剂时的应用。着重介绍了一维CuO纳米线、纳米棒、纳米管的制备方法及其对常见多种可燃或有毒气体的气敏响应情况。指出了纳米结构CuO是今后CuO在气敏传感器中的重点发展方向,最后提出了CuO气敏材料应用时存在的一些问题以及今后的研究工作重点。     

氧化石墨烯在气体传感器中的应用研究进展

氧化石墨烯因表面含有丰富的含氧官能团而具有十分优异的气敏性能,可应用于低浓度(ppb级)环境下气体的检测。综述了现阶段氧化石墨烯在气体传感器中的研究进展,分析了氧化石墨烯对湿度、NO_2、H_2、CH_4的敏感性能,重点探究了氧化石墨烯表面含氧官能团的类型对其选择性的影响规律,并总结了目前研究中存在的问题,为后续开展氧化石墨烯气体传感器的研究与应用提供借鉴。     

WO_3掺杂NiO纳米材料的VOCs气敏性能

制备掺杂WO_3的NiO纳米粉体材料并测量了材料的VOCs气敏性能。XRD分析表明,WO_3掺杂使NiO粉体中出现新相NiWO_4。随着WO_3掺杂量增多,NiO的衍射峰半高宽明显宽化,WO_3掺杂抑制了热处理过程中NiO晶粒的长大。50×10~(-6)浓度二甲苯、甲醛、甲苯和乙醇等气体中的测量结果说明,WO_3掺杂明显提高了NiO材料的VOCs气体灵敏度,对二甲苯的最佳掺杂量是5%,最大灵敏度为26.4,响应时间4s;对甲醛的最佳掺杂量是10%,最大灵敏度是4.67,响应时间6s。     

WO3薄膜气敏光学传感特性研究

WO3薄膜是良好的光学气敏传感器材料.采用溶胶凝胶法制备了WO3掺杂薄膜,对样品在不同浓度氢气气氛中的气敏光学性质、敏感度及响应时间进行了测试、分析和计算,并结合光传输理论给出了气敏薄膜的光学变化机制,理论分析与实验结论吻合.     

单原子材料的制备、表征及其在气敏传感器中的应用进展

气敏传感器技术的发展对于人类社会发展具有积极的作用。近年来的研究显示,原子级分散的材料具有超高的活性、独特的电子结构和量子尺寸效应等,故将某些单原子负载在一定的气敏材料上,将会显著提高气敏材料的气敏性能。本文综述了近些年来国内外单原子材料的制备和表征技术及其在气敏传感器中的研究进展,分析了单原子材料的性能优势、单原子负载策略、分析方法、气敏性能、气敏机理等,同时探讨了存在的问题以及单原子材料气敏传感器在未来的发展趋势,最后对单原子材料在气敏传感器中的应用发展提出了相关的一些看法。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.