油相和水相的比例对反相微乳液法制备钡铁氧体磁学性能的影响

通过反相微乳液法制备钡铁氧体(BaFe12O19),研究了反相微乳液法油水比例对BaFe12O19磁学性能的影响,分析了烧结温度对晶相以及晶体形貌的影响,得到了最佳的实验工艺参数,当油相和水相的体积比为6:1时,通过透射电镜观察发现:80℃热处理得到的样品的前驱体颗粒尺寸约40nm;在800℃烧成后得到片状、直径约50～80nm的钡铁氧体,并测得其饱和磁化强度为47.41emu/g,剩余磁化强度为29.01emu/g,矫顽力为2209Oe,磁滞回线面积为1120708;在900℃热处理还出现了新相BaO2.     

共沉淀法替代M-型BaTiCoFe10O19粉体的制备

采用sol-gel法成功地合成了超细替代M-型BaTiCoFe10O19，磁粉，先驱体氢氧化物在醇：水=1：1的溶胶溶液中以共沉淀法制得。研究了熔盐Na2CO3和预热处理对粉体的粒子尺寸和粘连度的影响。X-射线衍射分析（XRD）分析表明添加5-15N％的Na2CO3分别在900℃烧成2h后得到了纯的BaTiCoFe10O19粉体，粉体的粒子尺寸随熔盐Na2CO3的添加量增大而减小，250-350℃预热处理也使粉体的粒子尺寸显著减小。SEM分析表明粉体为六角片状，粒子尺寸与XRD分析结果一致。     

棒状纳米钡铁氧体的制备及镧掺杂对其性能的影响

为了研究制备工艺和掺杂对纳米钡铁氧体形貌及性能的影响规律,采用柠檬酸溶胶-凝胶法与燃烧相结合的方法制备出了BaFe12O19及掺镧钡铁氧体棒状纳米粒子.采用X射线衍射仪（XRD）,透射电镜（TEM）和磁强样品振荡计（VSM）对BaFe12O19及掺镧钡铁氧体的结构、形貌及磁性能进行了表征.通过对几个主要参数的摸索,得出制备棒状钡铁氧体的最佳工艺条件：pH值为4,煅烧温度为850℃,煅烧时间2h.该条件下制得的BaFe12O19样品分散均匀,呈棒状,直径约为50nm,长径比为6：1,矫顽力高达43460e;采用同样的方法,对钡铁氧体进行了稀土镧元素掺杂,所得掺镧钡铁氧体粒度在纳米范围,也呈现明显的棒状.另外,通过掺杂稀土元素镧使钡铁氧体的成相得到改善,对钡铁氧体的磁性能有一定程度的影响.     

CdTe@Fe3O4磁性复合纳米粒子的合成与表征

本文通过层层自组装技术（1ayer-by—layer,LBL）成功制备了CdTe@Fe3O4磁性荧光复合纳米粒子,并对其特性和应用进行了讨论．首先,采用化学共沉淀法,以NaOH为沉淀剂,Fe^2＋和Fe^3＋物质的量的比为1：2．在50℃水相中电磁搅拌30min,制备出具有磁性的纳米Fe3O4,然后表面修饰1,6-己二胺．通过透射电镜（transmission electron microscopy,TEM）对其进行观察,粒径在10nm左右．核壳cdTe@Fe3O4复合功能纳米粒子的合成表明：Fe3O4和cdTc物质的量的比为1：3,pH=6．0,温度30℃,反应时间30min为其最佳合成条件．通过TEM、紫外和荧光光谱对合成的纳米粒子分别进行了表征．cdTe@Fe3O4粒径在12～15nm,最大发射波长从530nm红移到570nm,而最大吸收波长则从530nm红移到535mm．结果表明,磁性Fe3O4表面成功覆盖了CdTe壳层．核壳型CdTe@Fe3O4磁性荧光复合纳米粒子的应用能够实现对DNA进行简便快捷的标记、传感和分离．     

凝胶法制备Ba铁氧体的微观形态及磁性能

用溶胶-凝胶技术制备六角晶系BaFe12O19铁氧体超微粉末,采用热分析技术和XRD技术分析了其形成规律,运用扫描探针显微镜分析其微观形态,并测定了常温磁性能。结果表明：BaFe2O4和BaFe12O19的转变温度分别为414．55℃、755．78℃;800℃处理后得到的BaFe12O19超微粉末呈三种不同的形态,分别为圆形、带孔洞的圆形和圆环形;平均粒径为450nm左右;其厚度小于其直径;1000℃处理后的样品完全是BaFe12O19结构,其ds小于粗晶BaFe12O19铁氧体,而Hc大于粗晶肪BaFe12O19铁氧体。     

复合纳米纤维静电纺丝法的制备及其磁性

以聚乙烯吡咯烷酮（PVP）和金属盐为原料,利用静电纺丝法成功制备出了摩尔比为1：1的SrTiO3-SrFe12O19磁电复合纳米纤维。并通过FT-IR,XRD,SEM和VSM等技术对纤维前驱体及其产物的结构、热处理产物的物相、形貌及磁性能进行了表征。结果表明,样品经900℃焙烧2h后,即可得到纯的SrTiO3和SrFe...     

热处理温度对M-Ba铁氧体微米纤维结构和磁性能的影响

以柠檬酸和金属盐为原料,采用有机凝胶先驱体转化法成功制备了直径为500～600nm的钡铁氧体(BaFe12O19)微米纤维。通过XRD、SEM和VSM等技术对所制备的目标纤维进行了表征。结果表明,经750℃焙烧2h后,可获得M-Ba铁氧体纯相。随着焙烧温度的升高,晶粒逐渐长大,经850℃焙烧2h后,纤维主要由比较规则的片状晶粒组成。钡铁氧体纤维的磁性能主要受晶粒尺寸和测试温度的影响。经950℃焙烧2h后,组成纤维的晶粒尺寸约为62nm,室温下测得的饱和磁化强度和矫顽力均取得最大值,分别约为67A.m2/kg和328kA/m。在液氮(77K)条件下,纤维的饱和磁化强度有显著提高,最大值约为87A.m2/kg,这主要是由于纳米晶的表面自旋有序程度提高造成的。     

热处理对Ni-P-A12O3化学复合镀层摩擦磨损性能的影响

热处理可显著提高镀层的硬度和耐磨性能。采用化学镀的方法在45钢表面制备了Ni-P-纳米A12O3复合镀层,并以不同温度对其热处理,研究了镀层热处理前后的物相、硬度和耐磨性能。结果表明：400℃热处理后,Ni-P-A12O3复合镀层达到稳态,稳定相是Ni＋Ni3P＋NiO＋A12O3;镀层的显微硬度随热处理温度的升高而先增加后降低;随着镀液中纳米A12O3,（n-A12O3）颗粒含量的增加,热处理前后镀层的显微硬度和耐磨性能均先增加后降低;镀液中n-A1203颗粒含量为2．0g／L,400℃热处理1h的复合镀层的显微硬度和耐磨性能最佳。     

Ni—Zn—Fe氢氧化物的低温自发固相反应

摩尔比为Ni2＋：Zn2＋：Fe3＋：0．6：0．4：2．0的水溶液与OH-在气泡液膜中进行共沉淀反应,制得0．6Ni（OH）2（H2O）0.75·（0．4-n）Zn（On）2·2（1-m—n）Fe（OH）3·mFezO3·nZnFe2O4·xH2O前驱体,微结构为大量螺旋状分子簇和少量亚晶结构,用XRD检测结果表明,前驱体在室温放置10和14个月的转化产物是Fe2O3,ZnFe2O4和Nin6Znn．Fe2O4;放置55个月的主要产物是Nin6Znn4Fe2O4。提出了分子簇演绎氢氧化物脱水,优先生成Fe2O3晶核,亚晶结构演绎新生态氧化物分子自组装的低温自发固相反应机理。     

(Y,Gd)2O3:Eu(YGO:Eu)纳米粉体合成及透明陶瓷制备

研究以碳酸氢铵作为沉淀剂制备Y1．34Gd0.6Eu0.06O3（YGO：Eu）纳米粉体的工艺，并采用真空烧结制备了YGO：Eu透明陶瓷．实验结果表明：以硝酸盐为母盐，以碳酸氢铵为沉淀剂，在本研究试验条件下获得的YGO先驱物为晶态的水合稀土碳酸钇钆正盐．先驱物在600℃煅烧后可以得到立方晶型的YGO粉体．煅烧温度对粉体的颗粒尺寸及尺寸分布有影响，1100℃煅烧所获得的粉体由粒径-100nm的球形颗粒组成，颗粒尺寸分布均匀，粉体具有较好的烧结性能．采用所制备的YGO：Eu纳米粉体，在1670℃真空烧结2h可获得透光性良好的透明陶瓷，样品在可见光区的最高透过率可达74．6％，高于相同工艺条件下制备的氧化钇透明陶瓷．     

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.