Cf/Mg 复合材料异形件成形装置设计与实验研究

为实现Cf/Mg复合材料异形件的近净成形,在分析金属基复合材料液态浸渗制备技术的基础上,提出了真空压力浸渗-液固挤压制备Cf/Mg复合材料新工艺,并设计了相应的成形装置.利用设计的装置开展2D碳毡增强镁基复合材料异形件的制备研究.在熔炼温度为760~820℃,预制体预热温度为570~610℃,浸渗气压0.5 MPa和挤压载荷10~30 MPa等工艺参数下,成功制备出Cf/Mg复合材料异形制件.对复合材料制件进行宏观尺寸测量及扫描电镜(SEM)观察发现,制件外形完整,与设计一致;制件内部组织致密、纤维分布均匀;预制体在制备过程中没有发生明显的变形和破坏.     

网状结构Si3N4陶瓷增强金属基复合材料的研究

利用有机前驱体浸渍法制备了Si3N4网络陶瓷预制体,利用液态金属浸渗法制备出Al基、Mg基复合材料.分析了在浸渗过程中浸渗温度、润湿角、浸渗时间、浸渗高度的相互关系.在压力下金属液克服浸渗阻力,使浸渗得以完成.网络陶瓷骨架孔筋表面覆盖一层氧化膜有利于自发浸渗的进行.合金中适量镁元素的存在使界面上发生轻微化学放热反应,对浸渗有利.指出压力浸渗制备铝基复合材料与无压浸渗制备镁基复合材料的特点.探讨了这种复合材料抗压强度和摩擦磨损性能特点.指出Si3N4/Al复合材料,Si3N4/Mg复合材料抗磨擦性能明显优于基体,抗拉强度大大高于基体.     

网状结构Si3N4陶瓷增强金属基复合材料的研究

利用有机前驱体浸渍法制备了Si3N4网络陶瓷预制体,利用液态金属浸渗法制备出Al基、Mg基复合材料：分析了在浸渗过程中浸渗温度、润湿角、浸渗时间、浸渗高度的相互关系。在压力下金属液克服浸渗阻力．使浸渗得以完成。网络陶瓷骨架孔筋表面覆盖一层氧化膜有利于自发娄渗的进行。合金中适量镁元素的存在使平面上发生轻微化学放热反应．对浸渗有利。指出压力浸渗制备铝基复合材料与无压浸渗制备镁基合材料的特点。探计了这种复合材料抗压强度和摩擦磨损性能特点。指出Si3N4／Al复合材料，Si3N4/Mg复合材料抗磨擦性能明显优于基休．抗拉强度大大高于基体。     

无压浸渗法制备B4C/Al复合材料研究

采用无压浸渗法,分别以纯铝、超硬铝LC4和铸造铝合金9Si-3Mg-1Zn为渗体和碳化硼陶瓷预制体进行复合,制备出有高陶瓷体分比的B-Al-C陶瓷-金属复合材料,弯曲强度350～600MPa,韧性5～9MPa*m-1/2,采用扫描电镜,X射线衍射仪和金相显微镜和透射电镜对材料的微观结构进行分析,分析结果表明材料界面复合良好,在碳化硼和铝的界面有薄的Al3BC反应层生成使碳化硼与铝紧密结合, 在复合材料中碳化硼形成连续的骨架结构,金属相起到增韧、增强的作用.     

SiCp颗粒增强铝基复合材料工艺与组织研究

对无压渗透制备碳化硅颗粒增强铝基复合材料工艺进行了探索，并利用光学显微镜、扫描电镜对其组织进行了观察，用ｘ射线衍射仪对复合材料组成相进行了分析。结果表明：采用无压渗透技术，可以制备碳化硅颗粒增强铝基复合材料；熔融的基体合金对碳化硅颗粒预制体渗透完全；其过程存在Ａｌ与ＳｉＣ的化学反应，产物为Ｓｉ和碳化铝（Ａ１４Ｃ３），其中Ｓｉ进入基体中，Ａｌ４Ｃ３能与大气中水汽发生化学反应，结果使碳化硅铝基复合材料存放一定时间后发生龟裂和粉化。为限制Ａｌ与Ｓｉ反应，可向基体中加入适量的Ｓｉ元素，可使电裂与粉化问题得到解决。     

碳化硅颗粒表面吸附质对铝基复合材料制备及力学性能的影响

选用粒度为60～80μm的国产磨料级碳化硅颗粒作为增强体、以无压浸渗法制备高体份SiC_p/Al复合材料,采用超声清洗工艺对比研究颗粒表面吸附质对颗粒浸渗性以及复合材料力学性能的影响。结果表明:国产磨料级碳化硅颗粒表面普遍存在少量吸附质(<0.5%),吸附质以粒度更小(<5μm)的碳化硅颗粒为主,个别情况含有少量的游离碳。颗粒表面吸附质的存在严重影响了颗粒表面与熔融铝液的润湿性,并且会大幅度降低复合材料的密度和力学性能。超声清洗工艺可以有效去除碳化硅颗粒表面的吸附质,去除吸附质之后颗粒的浸渗成功率从25%提升至100%,复合材料的抗弯强度从320MPa提升至390MPa,弹性模量从203GPa提升至232GPa。     

Cf/Al复合材料异形件预制体制备及其力学性能研究

目的解决铝基复合材料异形件形状特征复杂,对良好的抗拉和抗剪切等使用性能有较高要求,制备难度较大等问题。方法提出了"铺层-缠绕-缝合"碳纤维异形件预制体制备方法,设计了直接式缝合、插销式缝合、整体式缝合3种成形方案,通过理论计算分析不同方案预制体的力学性能;在此基础上,采用液固高压成形Cf/Al复合材料异形件,并通过断口形貌、微观组织以及致密度的分析,解释了其力学性能提升的原因。结果根据较佳的预制体成形方法,成功制备了预制体和复合材料异形件;异形件内部未发现气孔、微裂纹等缺陷,Cf/Al复合材料拉伸强度达278MPa,较基体提高了114%。结论整体缝合法为较佳的预制体成形方案,可使构件具有较高的连接强度和定位精度;复合材料内部浸渗良好,致密度达98.59%,故该复合材料的力学性能较铝合金基体提升较多。     

低黏结剂含量SiC素坯的选区激光烧结

Al/SiC是SiC基复合材料, 具有优异的力学性能和热学性能, 在大功率电子器件、5G基站关键冷却组件、电动汽车、高速刹车片、空间探测器操作装置等相关领域具有不可替代的作用。传统制备工艺的局限性使得近净成形的无压浸渗法成为制备Al/SiC复合材料的一种较好的方法。得到高质量的碳化硅(SiC)陶瓷素坯是熔渗技术的先决条件, 选区激光烧结技术是获得高质量陶瓷素坯的一种新方法。该方法具有快速、高效的优点, 无需模具即可成型制备大规模、复杂形状部件。本研究以热塑性酚醛树脂为黏结剂, 利用机械混合与喷雾造粒的方法制备了复合粉体, 采用选区激光烧结技术制备SiC素坯, 制备了黏结剂体积分数低至15%的样品, 并对其力学性能和微观结构进行表征。当树脂含量增大到体积分数25%时, SiC坯体的强度增量为702.1%。对于喷雾造粒粉体制备的样品而言, 喷雾干粉的多孔结构使得SiC生坯的孔隙率较高(71.18%), 导致生坯强度下降。     

浸渗法制备双连续TiB2/(Cu,Ni)复合材料的组织和性能

用高温粉末烧结结合自发浸渗法制备高TiB2含量(体积含量约为86%)的双连续TiB2/(Cu,Ni)复合材料,研究了不同陶瓷体积含量多孔材料对TiB2/(Cu,Ni)复合材料微观组织和力学性能的影响.采用XRD和SEM分析了复合材料的相组成和微观结构,用三点弯曲试验测试了复合材料的弯曲强度和断裂韧性.结果表明:经过预制坯高温烧结后自发熔渗金属是制备致密的双连续TiB2/(Cu,Ni)复合材料的有效方法,复合材料的致密度和力学性能得到显著提高;当TiB2陶瓷体积含量为81.6%以及浸渗温度为1500℃条件下,TiB2/(Cu,Ni)复合材料的弯曲强度和断裂韧性分别达到640.5 MPa和9.37 MPa·m1/2,相对密度为98.4%.     

连续碳纤维/Mg复合材料异形薄板件预制体制备与成型

针对连续碳纤维增强镁基(Cf/Mg)复合材料异形薄板件预制体制备成本高、性能不稳定等问题,提出了"仿形编织-环向缠绕-铺放定位-缝合增强"的低成本组合制备工艺,设计开发了与之相配套的预制体制备装置。通过理论与实验研究,确定薄板与凸台预制体分体制备:薄板预制体采用径向编织、环向缠绕,仿形无纬布织物与环向纤维层针刺合成,其中纬纱引纬张力控制在1.7~2.3N;凸台预制体采用无纬布横向叠层,再与环状薄板预制体缠绕缝合而成。所制备预制体外形完整,形态良好,环向碳纤维分布均匀、与径向增强碳纤维呈规则排列。经液固挤压制备的Cf/Mg复合材料异形薄板件表明,凸台与薄板连接强度良好,为成形高质量Cf/Mg复合材料异形薄板件奠定了基础。     

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.……     

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.     

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.