高能球磨对片状银粉的改性研究

采用高能球磨工艺,利用激光粒度仪、扫描电子显微镜、BET吸附等测试手段,研究了由化学法制备出的片状银粉在进一步细化过程中,银粉随球磨工艺参数的改变而变化的情况,讨论了不同球磨时间和不同分散剂对银粉粒度、形貌、比表面积等性能的影响.结果表明:球磨20h,使用无水乙醇作为分散剂,可制得平均粒径为2.5μm、比表面积为2.9m2/g的超细片状银粉,满足电子浆料的使用需求.     

片状银粉行星球磨过程中的影响因素

采用机械球磨法制备片状银粉,通过扫描电镜和热重分析仪表征银粉形貌、粒径及纯度,研究球磨动能及后处理等因素对银粉性能的影响。结果表明,以球形银粉为球磨前驱体,氧化锆球为磨球,无水乙醇为球磨介质,球磨转速为200 r/min,球料质量比为12∶1,介料质量比为2∶1,填充系数为0.5,油酸为球磨助剂,随着球磨时间的延长,能够制备出不同粒径范围的高片状率的片状银粉;经过后处理后,银粉表面粗糙,热失质量分数小于0.1%,符合片状银粉的应用指标。     

太阳能电池正极浆料用超细银粉的制备

采用液相化学还原法,以聚乙二醇4000为分散剂,用抗坏血酸直接还原硝酸银溶液制备太阳能电池正极浆料用银粉。通过扫描电镜(SEM)、激光粒度分析仪和X射线衍射仪(XRD)等方法分析银粉的形貌、粒度及纯度,研究分散剂用量、抗坏血酸浓度、硝酸银浓度和溶液pH值等工艺条件对银粉粒度、物相结构及形貌的影响。结果表明,随着分散剂用量的增大,银粉颗粒粒度先减小后趋于稳定。在溶液pH值为4,抗坏血酸浓度和硝酸银浓度分别为2.0和0.5mol/L,聚乙二醇4000与硝酸银的质量比为0.10时,可以制得分散性好、纯度高、面心立方晶系和平均粒度为5.32μm的规则球形银粉。并将所得银粉调制成太阳能电池用浆料,通过丝网印刷在硅片上,使用四探针测试仪测得烧结膜的方阻为4.27mΩ/□,可满足太阳能电池的电性能要求。     

纳米复合碳化钨-钴粉末的分散与粒度表征

为研究纳米复合碳化钨-钴粉末的分散稳定性和粒度表征方法，以一定量分散介质和分散剂作用于纳米复合碳化钨-钴粉末，利用氮吸附法(BET)、光子相关光谱法(PCS)和电位分析仪分别测试了粉末的比表面积、粒度及其分布和粉末的ξ电位．研究结果表明：高比重的纳米复合碳化钨-钴粉末经一定工艺处理后具有相当的分散稳定性，但长时间球磨对分散并非有利；用BET可表征一次粒径，而PCS则表征二次粒径。     

热电材料Bi_2Te_3粉体的制备及粒径分析

为了确定经机械合金化法制备的Bi2Te3粉体进行激光粒度分析的适宜条件,运用X射线粉末衍射、激光粒度分析、比表面积分析等手段对样品物相和粒径进行分析。结果表明,高能球磨30 h后,Bi2Te3晶粒的平均粒径达到本实验中的最小值135 nm;当分散剂采用Tween-80,体积分数为1%;粉体质量浓度为0.01 g/mL时,对样品进行激光粒度分析的结果较为理想。     

纳米氟硼酸钾粉末的制备及表征

探讨了高能球磨法制备纳米KBF4粉末的工艺过程及影响因素.通过选择合适的球磨工艺及表面活性剂,以普通KBF4粉末为原料成功制备出粉末的粒度均径为81.2nm、比表面积为28.26m2/g的纳米级KBF4粉末.分别采用BET比表面积测试法、X射线小角度散射法(SAXS)及扫描电镜对纳米KBF4粉末进行了表征.     

超细碳化钨介质球磨工艺的研究

对介质球磨法制取超细碳化钨粉末进行了研究。实验探讨了不同线速度、磨球尺寸、分散剂的添加对初始粒径约1μm的碳化钨粉末的介质球磨工艺的影响。根据W=P·t,在保持能耗不变的情况下得到了粒度与线速度之间的关系,从而在一定粒度范围内选择最有效的线速度。同时,采取分阶段球磨的球磨效率要高于单一线速度球磨,可实现用更少的成本达到相同粒度。此外,球磨时添加羧甲基纤维素钠分散剂,粉末粒度越小时分散效果越明显,实验中在输出功率不变时,与不添加分散剂对比,其时间效率提高了13%,最终的粉末也呈现很好的分散性。最后,磨球尺寸的大小可决定最终粒度的大小。因此,根据目标粒度采用合适的磨球尺寸和球磨工艺才能达到最高的球磨效率。     

合成一维β-SiC纳米材料原料粉体的球磨工艺研究

采用高能球磨对合成一维β-SiC纳米材料的原料-Si粉和SiO2粉分别进行处理。通过正交试验研究球磨转速、时间、球料比、级配比等因素对球磨后粉体粒径的影响规律,结果表明,Si粉的球磨优化工艺为转速300r/min、球磨时间4h、球料比5:1,级配比φ20 mm:φ10 mm:φ6mm:φ2mm=1:50:180:400;SiO2粉的球磨优化工艺为转速350 r/min、球磨时间4.4 h、球料比15:1,级配比φ20mm:φ10mm:φ6mm:φ2mm=1:50:180:400。借助粒度分析仪及透射电子显微镜(TEM)对产物进行表征,发现经过球磨处理后的粉体粒度分布均匀,比表面积提高,可用以合成高质量的一维β-SiC纳米材料。     

高能球磨法制备铁、钨金属微粉的研究

用高能机械球磨法制备了金属铁、钨微粉，对振动磨的结构及破碎原理作了简要介绍，分析了铁、钨粉末产品的粒度分布特性、比表面积变化情况，讨论了原料性质、球磨时间、球磨强度、球料比等因素对高能球磨过程的影响。     

片状银粉表面润滑层的化学去除

以水合肼为还原剂还原硝酸银溶液,以沉淀法制备微细银粉,再经机械球磨得到光亮片状银粉.为提高以片状银粉为填料的复合物的导电性,有必要去除银粉球磨过程中化学吸附在银粉表面的润滑层.利用醇酸混合液对光亮片状银粉进行表面化学处理,采用差示扫描热分析(DSC)研究了处理前后片状银粉的热性能,并用扫描电镜和能谱分析仪(EDAX)对处理前后的片状银粉的表面进行了形貌观察和成分分析.结果表明,醇酸混合液可以完全去除光亮片状银粉表面化学吸附的润滑剂(油酸),同时探讨了片状银粉表面油酸的去除机理.     

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...     

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.     

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.     

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.