电弧法制备碳包覆铁纳米微粒的纯化研究

利用钨电极电弧法制备了碳包覆铁纳米微粒,采用酸洗加磁选的方法对初产物进行了纯化.用透射电子显微镜、X射线衍射仪和振动样品磁强计对产物的形貌结构、物相组成以及磁性能进行了表征分析.结果表明:该纯化方法可以有效地去除产物中未被包覆或碳包覆不完整的铁颗粒及各类碳杂质,纯化后的产物以包覆多层碳膜的铁纳米颗粒为主;粉体的磁滞回线也表明经纯化后产物的磁性能得到了明显提高.     

纳米洋葱碳制备及其在超级电容器中的应用

以甲烷为碳源,采用化学气相沉积法制备了石墨化程度高的纳米洋葱碳(CNOs),通过酸洗-煅烧-酸洗对CNOs进行纯化并作为导电剂应用于超级电容器,结果表明,制得的超级电容器比容量为143.7F/g,与导电炭黑Super-P相比提高30.6%,经过1000次循环后比容量为原来的94.8%,循环稳定性高。     

碳包裹镍核-壳结构复合纳米颗粒的制备及性能研究

采用自行研制的实验装置,通过阳极弧放电等离子体技术成功制备了碳包裹镍核-壳结构纳米复合颗粒,并采用酸洗和磁选的方法对初产物进行了纯化.利用高分辨透射电子显微镜(HRTEM)、X射线衍射(XRD)、透射电子显微镜(TEM)和X射线能量色散分析谱仪(XEDS)等测试手段对样品的化学成分、形貌、微观结构和粒度等特征进行了表征...     

负载Pd蛋黄-蛋壳型磁性碳纳米复合材料Fe3O4@C-Pd的制备及其催化性能研究

用氨水做催化剂,利用正硅酸乙酯(TEOS)的溶胶-凝胶化过程和间苯二酚与甲醛的缩聚反应一步合成核壳材料;通过在N_2中碳化并在NaOH溶液中刻蚀SiO_2制得蛋黄-蛋壳型结构纳米微球;最后负载Pd得到磁性碳纳米复合材料Fe_3O_4@C-Pd。采用透射电子显微镜、X射线粉末衍射仪、紫外-可见分光光度计以及振动样品磁强计等手段对所制纳米材料的形貌、组成结构、晶体结构和磁性能进行了分析表征。将Fe_3O_4@C-Pd作为催化剂用于对亚甲基蓝(MB)的催化还原,结果表明其具有良好的催化活性,重复使用4次催化活性几乎保持不变。     

金属对炭黑转化为洋葱状中空结构纳米碳的影响

研究了炭黑分别在 Fe、Co、Ni 三种金属化合物作用下的催化转化行为, 以期使炭黑质点中不连续的无规则小石墨片层重新组装、构筑成洋葱状中空结构纳米碳. 采用透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)、X射线衍射(XRD)和Raman光谱分析表征了炭黑及其催化炭化产物的微观形貌和结构. 结果表明: 尽管三种金属催化剂均可通过溶碳-析出机制形成过渡态碳包覆纳米金属颗粒, 继而构筑成由准球形同心石墨壳层组合的洋葱状中空结构纳米碳, 但三种金属催化剂显示不同的催化效果, 终碳产物的形态和纯度差异较大, 其中以Fe 的催化效果最好.     

四方排列有序Ag/TiO2空心微球的制备及光催化性能

采用低温垂直沉积法制备了聚苯乙烯(PS)胶体模板,由于低温下粒子热运动受到抑制,排列时发生位错,因此模板中存在大面积四方排列结构。然后采用化学镀法、溶胶-凝胶法在PS微球表面依次沉积银纳米粒子、纳米TiO2,最后高温煅烧除去模板制备了四方排列有序Ag/TiO2空心微球。通过扫描电镜(SEM)、X射线衍射(XRD)对样品进行表征。结果表明这种材料很好地保持了模板的四方排列,具有高度有序的纳米结构。选择降解甲基橙溶液来检验样品的光催化性能,并与纳米TiO2薄膜、四方排列TiO2空心微球的光催化性能进行比较,结果表明四方排列Ag/TiO2空心微球具有最佳的光催化性能。这是有序空心纳米结构和银纳米粒子的沉积共同作用的结果。     

双微乳液法制备CoFe2O4纳米颗粒及其磁性能研究

以TritonX-100/正己醇/正己烷/水为反应介质,采用双微乳液法合成了尖晶石型CoFe2O4磁性纳米颗粒.利用TG-DSC、FTIR、TEM、XRD、VSM等测试技术对CoFe2O4煅烧前后的结构和磁性能进行表征.结果表明,采用微乳液法制备的CoFe2O4前驱物经煅烧后可获得纳米级磁性微粒.煅烧温度对微粒粒径和磁性能有较大影响,经300℃煅烧后的微粒粒径为15nm,700℃煅烧后微粒粒径增大为52nm.样品的饱和磁化强度和剩余磁化强度也随热处理温度的升高而增加.     

双微乳液法制备CoFe2O4纳米颗粒及其磁性能研究

以TritonX-100／正己醇／正己炕／水为反应介质，采用双微乳液法合成了尖晶石型CoFe2O4磁性纳米颗粒。利用TG-DSC、FTIR、TEM、XRD、VSM等测试技术对CoFe2O4煅烧前后的结构和磁性能进行表征。结果表明，采用微乳液法制备的CoFe2O4前驱物经煅烧后可获得纳米级磁性微粒。煅烧温度对微粒粒径和磁性能有较大影响，经300℃煅烧后的微粒粒径为15nm，700℃煅烧后微粒粒径增大为52am。样品的饱和磁化强度和剩余磁化强度也随热处理温度的升高而增加。     

通过乙醇催化燃烧方法制备碳纳米纤维

介绍了一种用于合成碳纳米纤维的既简单又经济的方法。该方法采用乙醇作为碳源，硝酸镍，硝酸铁和氯化铁分别作为催化剂先体，铜薄片作为基底。通过这种方法，获得了大量丰富的产物。采用场发射扫描电子显微镜、透射电子显微镜、拉曼光谱仪和选区电子衍射光谱分析仪对所制备的碳纳米纤维进行了表征。实验结果表明，催化剂的形貌、尺寸对碳纳米纤维的形貌有影响。此外，通过对样品的拉曼表征，样品的石墨化程度被估算。     

静电纺丝制备磁性碳纳米复合纤维及其表征

以聚丙烯腈(PAN)、乙酰丙酮铁(AAI)、N, N-二甲基甲酰胺(DMF)为原料, 采用静电纺丝-煅烧技术成功制备出磁性碳纳米复合纤维。通过TEM分析发现CF900的直径约为130~210 nm, 磁性纳米颗粒均匀地分散在碳纳米纤维中, 并探讨了碳化温度对碳纳米复合纤维磁性能的影响。结果显示: 饱和磁化强度(M_s)和剩余磁化强度(M_r)均随温度的升高而增大, 样品CF900的饱和磁化强度(M_s)高达27.55 A·m²/kg, 比表面积(S_BET)和总孔容积(V_total)达354.0 m²/g和0.315 mL/g。     

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.