SnO2/NiO复合半导体纳米纤维的制备及气敏性能研究

采用静电纺丝技术结合化学沉淀法和高温煅烧处理, 制备了具有不同Sn含量的SnO₂/NiO复合半导体纳米纤维。采用扫描电子显微镜(SEM), X射线衍射仪(XRD)和能量色散X射线光谱仪(EDS)对样品的形貌, 结构以及各元素含量进行表征。以乙醇为目标气体, 探究SnO₂/NiO纳米纤维的气体传感性质, 以及Sn含量对复合纳米纤维气敏性能的影响。研究结果表明, SnO₂/NiO复合纳米纤维具有三维网状结构, SnO₂复合对NiO纳米纤维的气敏性能具有明显的增强作用。随着SnO₂含量的增加, 复合纤维对乙醇气体的响应灵敏度增强, 其中响应最高的复合纳米纤维在最佳工作温度160 ℃条件下对体积分数为100×10^-6乙醇气体的响应灵敏度为13.4, 是NiO纳米纤维最大响应灵敏度的8.38倍。与市面常见的乙醇气体传感器MQ-3相比, SnO₂/NiO复合纳米纤维的最佳工作温度更低, 响应灵敏度更高, 具有一定的实际应用价值。     

Fe掺杂NiO纳米花状微球的制备及其气敏性能研究

采用水热法成功制备了Fe掺杂NiO纳米花状微球,研究了Fe掺杂量对微球结构、形貌和气敏性能的影响。气敏实验结果表明:Fe掺杂NiO纳米微球基气敏元件对丙酮的气敏性能较纯相NiO显著提高;当Fe掺杂量为0.03g时,气敏器件在工作温度为280℃,丙酮质量浓度为3.7×10~(-4) mg/L条件下,气体灵敏度为41.8,是相同条件下未掺杂NiO基气敏元件的12倍,该气敏元件在检测低浓度丙酮气体时也表现出优异的性能。     

NiO基氧化物热电材料的合成及其性能

采用溶胶凝胶法制备了Li掺杂的NiO基氧化物热电材料,研究了Li掺杂对其热电性能的影响,实验结果表明:在x=0.03,0.06,0.09掺杂比例范围,Li+很好地进入了NiO的晶格,没有形成新的杂相。热电性能测试结果显示,在室温至750K的范围内随着Li掺杂量的增加,电导率显著增加,而样品的Seebeck系数随着掺杂浓度增高明显降低,样品Ni0.94Li0.06O在750K的功率因子PF=1.9×10-5 W.m-1.K-2,随温度升高,PF增加趋势明显,表明在高温环境中可具有更大的PF。     

离子液体电沉积制备Cu掺杂NiO电致变色薄膜及其性能EI北大核心

NiO是一种常见的电致变色材料,元素掺杂改性是改善NiO薄膜电致变色性能的重要方法。以离子液体为介质,采用电沉积法制备Cu掺杂NiO薄膜,并研究Cu元素掺杂对NiO薄膜电致变色性能的影响。结果表明:Cu掺杂NiO薄膜的电致变色性能相较于纯NiO薄膜有明显提升。Cu掺杂含量为6%(原子分数,下同)时,薄膜光调制范围最大,为54.7%,着色效率最高,为61.54 cm^(2)/C,Cu掺杂含量为12%时,薄膜的着褪色响应时间最短,分别达到2.7 s与2.6 s。薄膜的物相结构为面心立方晶相Ni_(1-x)Cu_(x)O,由纳米粒子堆积而成,表面存在大量利于离子扩散的孔隙。     

Ce掺杂NiO纳米材料的制备及其气敏性能研究

以硫酸镍、硝酸铈和氢氧化钠为原料,聚乙烯吡咯烷酮(PVP)为表面活性剂,先通过化学沉淀反应,再经过高温煅烧得到Ce掺杂NiO纳米材料,并利用X射线衍射仪(XRD)和透射电子显微镜(TEM)对所得材料进行表征与分析。将所得Ce掺杂NiO纳米材料制成气敏元件,测试其对乙醇气体的敏感性能。结果表明:当Ce掺杂量为3%(质量分数)时,NiO纳米材料对乙醇气体具有较好的气敏响应性能;在工作温度为300℃时,该Ce掺杂NiO纳米材料对5×10~(-6)乙醇的灵敏度可达到2.20,响应时间小于20s。     

La3+掺杂TiO2纳米纤维的制备、表征与光催化性能

结合溶胶-凝胶法、静电纺丝技术和高温煅烧制备了La3+掺杂TiO2纳米纤维.采用扫描电子显微镜、X射线能谱仪、比表面积及孔隙分析仪、X射线衍射仪和紫外分光光度计对纳米纤维的形貌、晶型、表面和孔隙结构以及光催化性能进行了表征和测试.结果表明,La3+掺杂TiO2纳米纤维表面为多孔的纤维状结构.La3+掺杂明显改善了TiO2纳米纤维的表面孔隙结构,对TiO2纳米纤维的粒子生长有一定的抑制作用.光催化降解性能测试结果表明,当La3+掺杂量为0.04%(质量分数)时,TiO2纳米纤维的光催化性能最佳.     

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。     

异质结型NiO/ZnO复合纳米纤维的制备及光催化性能

采用静电纺丝技术, 以聚乙烯醇(PVA)和醋酸锌[Zn(CH₃COO)₂]为前驱体, 制备纯ZnO纳米纤维, 并以其为基质, 醋酸镍为镍源, 通过溶剂热法制备了NiO/ZnO复合纳米纤维. 利用X射线衍射(XRD)、扫描电镜(SEM)、高分辨透射电镜(HRTEM)和荧光光谱(PL)等分析测试手段对样品的结构和形貌进行表征。以罗丹明Ｂ的脱色降解为模式反应, 考察了样品的光催化性能。结果表明: NiO粒子均匀地负载到ZnO纳米纤维上, 得到了异质结型NiO/ZnO复合纳米纤维光催化材料, 与纯ZnO纳米纤维相比光催化活性明显提高, 且易于分离、回收和再利用。循环使用3次, RB的脱色率仍保持在89%以上。     

NiO/In2O3纳米复合材料的制备及气敏性能研究

采用水热法结合水浴法制备出了NiO/In2O3纳米复合材料,利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线衍射仪(XRD)等对其微观形貌和晶相进行表征分析。表征结果表明,制备所得In2O3纳米微球直径为200~300 nm,其表面均匀包覆厚度约为20 nm的NiO纳米片。气敏测试结果表明,基于NiO/In2O3异质结纳米复合材料的气体传感器对甲醛的最佳工作温度为220℃;在最佳工作温度下,对浓度为1×10^-5的甲醛气体响应可达到20,响应/恢复时间分别为4 s/16 s,且具有较好的重复性和选择性。最后,对分级结构及p-n异质结对其气敏机理进行了探讨。     

掺杂氯化锂的聚氨酯超细纳米纤维的制备及其空气过滤应用

本研究采用静电纺丝技术制备掺杂氯化锂(LiCl)的超细聚氨酯(PU)纳米纤维以用作空气过滤,并通过不同的测试方法对其进行表征.研究结果表明,当PU浓度为15 wt％时(盐的固含量为0.3 wt％),纳米纤维的结构形貌较整齐有序,纤维分布均匀,纳米纤维平均直径达到84 nm.此时,纤维的断裂伸长率为186.01％,断裂强度为6.29 MPa;当LiCl溶液浓度升高时,纤维形貌开始变差,力学性能开始下降.当LiCl含量达到0.5 wt％时,其断裂伸长率为131.07％,断裂强度为2.43 MPa.利用此纺丝工艺,本研究制备了一种新型的三层结构的玻璃纤维粗网/克重为2～3 g/m2的纳米纤维膜/聚酯纤维细网,过滤阻力为30.89 Pa,过滤效率94.71％(测试条件为:气体流速设置在32 L/min,NaCl气溶胶颗粒直径0.3μm).     

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...     

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.     

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.     

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.……     

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.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

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.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.