溶胶-凝胶法制备钇掺杂氧化锆的工艺研究

论述了用溶胶-凝胶法制备钇掺杂的氧化锆前驱体的过程,系统地研究草酸溶液的浓度、pH值、加热温度以及添加方式对溶胶、凝胶的影响,得出制备氧化锆前驱体的最佳工艺条件:当氧氯化锆溶液与草酸溶液的浓度比为1.25～2,草酸溶液pH值为1～2,加热温度为40～80℃,制得的前驱体溶胶、凝胶均匀,透明.正加方式得到的溶胶淡蓝色透明,较反加方式下的溶胶的胶凝时间短.并对最佳工艺条件制备的粉体进行SEM分析,结果表明,很好地合成了钇掺杂的纳米氧化锆粉体.     

溶胶-凝胶法制备纳米Y2O3粉体

为了改善Y2O3粉体的分散性,提高其烧结活性,试验以三乙醇胺和氨水为凝胶剂,利用溶胶-凝胶方法合成了纳米级Y2O3粉体,采用差热/热重、X射线衍射、透射电镜研究了前驱体的组成、前驱体在不同的煅烧温度下的物相变化以及煅烧粉体的分散性.结果表明,前驱体的组成为Y2(OH)5.14(NO3)0.86H2O,在500℃保温2h可直接生成立方相的Y2O3,煅烧至1000℃保温2h得到了结晶度高、分散性好、平均粒径为50nm、近球形的YO纳米粉体;三乙醇胺的加入有利于提高YO粉体的分散性.     

尖晶石型Ni0.8Zn0.2Fe2O4纳米晶体的?制备及电磁性能研究

以金属离子的柠檬酸盐为前驱体,通过sol-gel自燃烧的合成方法制备了镍锌铁氧体(Nio.8Zno.2Fe2O4)纳米晶体.采用FT-IR、DSC-TG、XRD、TEM波导等方法对产物以及产物的电磁性能进行了表征.结果表明,在前驱体中,金属离子与柠檬酸以络合物的形式存在.凝胶在220℃完成自燃烧反应.随着热处理温度的升高,粉体的粒径逐渐增大.纳米晶体在8～12GHz的测试条件下具有介电损耗与磁损耗.随着涂层厚度的增加,混合媒质的微波反射率逐渐增加,反射率吸收峰随着厚度的增加向低频移动.     

纳米LaAlO3粉体的制备与烧结

对共沉淀法制备纳米LaAlO3粉体及烧结进行了初步研究．采用La(NO3)3与Al(NO3)3为原料，控制pH=9左右，在室温下完成共沉淀，前驱体经800℃／2h的条件下煅烧后可获得纳米LaAlO3粉体，粉体颗粒约50nm．无压烧结的结果表明，这种纳米LaAl03粉体的烧结性能较好，通过选择适当的条件，在1500℃下烧结可获得密度达6．2g／cm^3的LaAlO3材料．     

拓展作用光范围的纳米TiO2-xNx制备和表征

以廉价的工业偏钛酸为原料,采用特殊的酸解工艺制得纳米级水合二氧化钛粉体,再利用高温管式炉对前驱体-TiO2·nH2O进行掺氮,制得纳米TiO2-xNx粉体,研究了不同掺氮气体和反应工艺对TiO2-xNx粉体吸光特性、形态结构的影响.结果表明水合TiO2粉体与氨气在600℃下反应5h,制得的粉体为锐钛矿型结构,粒径约为20nm,光吸收阀值由387nm红移至520nm左右.     

反应条件对水热法制备纳米ATO粉体形貌和电性能的影响

以SnCl4·5H2O和SbCl3为原料,采用水热法制备出了纳米级锑掺杂二氧化锡(ATO)导电微粉,运用XRD和TEM等测试手段对粉体进行了表征,比较系统地研究了掺杂量,共沉淀温度,溶液pH值,水热时间、温度和表面活性剂对粉体粒度、形貌和电性能的影响规律.研究表明,合成的ATO粉体分散性较好、导电性能优异,粒径在10nm左右,具有金红石型结构.在ATO纳米导电粉的制备过程中,前驱体制备温度对其性能有很大影响,当共沉淀温度在40-50℃时制得的粉体导电性能最佳.水热条件对粉体的形貌、粒度和导电性也有较大的影响,在200℃,4h,pH=2～4条件下可以制得导电性能良好的ATO粉体,所添加的表面活性剂可以改善粉体的粒径和分散性能,但对粉体的导电性影响极小.掺入Sb3 的量对载流子的迁移率有很大的影响,在掺杂浓度为4～5%左右可制得导电性极佳的纳米ATO粉体.     

纳米TiO_2复合抗菌材料的制备及其性能研究

采用溶胶-凝胶技术,以钛酸正丁酯为前驱体,于450~700℃的空气气氛中煅烧3h,分别制得了有、无SiO2包膜的掺杂银、镍金属离子的复合纳米TiO2抗茵粉体.采用TG-DSC、XRD、SEM等方法对产物进行表征,并选用大肠杆茵、枯草芽孢杆茵为受试菌种,采用抑茵圈实验对粉体抗茵性进行检测.结果表明,在该实验条件下制备的纳米TiO2>为锐钛矿型,通过包覆SiO2能有效地减小SiO2的粒度,防止团聚的产生,粉体抗茵性能良好,无SiO2包膜的抗茵粉体抑茵效果优于有包膜的抗茵粉体,在700℃下煅烧的抗茵粉体抑茵效果最好.     

锐钛矿型纳米TiO_2粉体的纯净制备

以钛酸丁酯为原料,采用可控醇盐水解沉淀法制得TiO2前驱体,450℃恒温煅烧2h后制备出粒径约10nm的纳米TiO2粉体,并与传统溶胶-凝胶法制备的TiO2纳米粉体的形貌、结构、工艺过程进行了对比.结果表明,可控醇盐水解沉淀法可制得纯度高、粒径小且分布范围窄的纳米TiO2粉体,工艺简单,流程最短.该方法的关键是实现了醇盐的可控水解.     

γ-Fe2O3/SiO2纳米复合粉体的制备

以硝酸铁和正硅酸乙酯分别作为氧化铁和SiO2的前驱体,通过溶胶-凝胶工艺制备了γ-Fe2O3/SiO2纳米复合粉体.若使用氯化铁为氧化铁前驱体,SiO2基体中则会生成α-Fe2O3.当干凝胶热处理温度较低时(T＜400℃),复合粉体(硝酸铁为前驱体)以非晶态存在.当T达到600℃时,γ-Fe2O3粒子在SiO2基体中大量形成.随着热处理温度的进一步升高,粉体中开始有α-Fe2Oa杂质生成.使用盐酸做添加剂对复合粉体中γ-Fe2O3粒子大小及颗粒尺寸分布均有显著影响.     

溶胶-凝胶法制备纳米Si_3N_4(Y_2O_3)粉末的研究

本文以硅溶胶、尿素和炭黑为原料，采用溶胶-凝胶碳热氮化法在1500℃、2h条件下制得粒径为50～80nm的Si3N4纳米粉末．比较了由硅溶胶与尿素经氨解合成的前驱体和硅溶胶二种不同起始物料的反应活性，研究了氮化条件对合成反应的影响．结果表明：氨解前驱体使硅溶胶中的结构水排除，有助于加快反应速率，提高产物氮含量．本文同时以Y（NO3）3为添加剂，在溶液状态与硅源混合，合成了Si3N4－Y2O3纳米复合粉末.     

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.