超声振荡对多壁碳纳米管/VARTM用环氧树脂复合材料导电性能的影响

借助超声振荡工艺促进了多壁碳纳米管(MWNTs)在VARTM用环氧树脂(EP)中的分散,通过真空辅助树脂传递模塑成型(VARTM)工艺制备了MWNTs/EP复合材料试样并研究试样的导电性能。结果表明,随着超声振荡时间、功率和频率的增大,不同MWNTs添加量的试样导电性能均呈现出先升高后降低的趋势。在超声振荡时间90min、功率80 W和频率45kHz附近分别达到了阈值,MWNTs的添加量仅1%就可以达到降低纯EP表面电阻率(1012Ω·cm)近4个数量级的要求。实验还运用扫描电镜(SEM)证实了MWNTs在EP中的分散情况。     

基体诱导法制备碳纳米管/云母复合导电粉

基体诱导法制备碳纳米管(CNT)/云母复合导电粉, 即用聚乙烯醇(PVA)或聚丙烯酰胺(PAM)对云母进行处理, 将处理后的云母与CNT分散液混合, 使CNT吸附在云母表面. 测试复合导电粉的体积电阻率(ρ)发现, CNT含量为1.0wt%时, CNT/云母的ρ为2.0×10⁴Ω·cm, 而用PVA修饰的云母制备CNT/云母, 体积电阻率达到86.6Ω·cm. 运用XPS、SEM对复合导电粉进行表征. 结果表明当云母表面经PVA修饰后, 能改善CNT在其表面的吸附和分散, 使CNT/云母的体积电阻率明显降低.     

取向碳纳米管/环氧树脂复合薄膜制备及结构与性能表征

碳纳米管(Carbon nanotube, CNT)/环氧树脂(Epoxy resin, EP)纳米复合材料中树脂含量、分布、CNT取向及其与树脂间界面结合是制备高性能纳米复合材料的关键因素。为了探究树脂分布和CNT/EP复合材料性能之间的关系,采用浮动催化化学气相沉积法制备的CNT薄膜和EP为原料,通过浸渍、牵伸、清洗和热压固化工艺制备CNT/EP复合薄膜。利用聚焦离子束结合扫描电子显微镜定性表征树脂在复合膜中的分布状态。结果表明,随着树脂含量增加,树脂在复合薄膜表面富集程度增加。在最优工艺条件下制备的纳米复合材料中CNT含量为66.14wt%, 拉伸强度和拉伸模量达到1405 MPa和46.7 GPa。      

PBT/石墨烯/碳纳米管复合材料的制备及其导电性能研究

以膨胀石墨为基体,用硝酸铁、碳酸铵等物质对其进行修饰,结合化学气相沉积工艺,原位制备出石墨烯/碳纳米管复合粉体材料;利用扫描电镜对复合粉体进行了表征。采用熔融混炼的方法制备PBT/石墨烯/碳纳米管复合材料并测试了其表面电阻。研究结果表明:该方法可以制备出性能优异的石墨烯/碳纳米管复合粉体材料,将该复合粉体加入到PBT中所制备的复合材料具有优良的电性能;当复合粉体加入量为5%时,PBT/石墨烯/碳纳米管复合材料的表面电阻可达到106Ω。     

聚癸二酸甘油酯/碳纳米管纳米复合材料的制备与性能

通过一步法得到了力学性能优异的碳纳米管(CNT)改性的聚癸二酸甘油酯纳米复合材料。将CNT分散在甘油中后与癸二酸进行缩聚反应,通过改变碳纳米管的添加量、癸二酸与甘油之间的配比以及固化时间得到了一系列的聚酯纳米复合材料。结果表明:CNT能明显的提高弹性体的强度和硬度,该纳米复合材料具有优异的力学性能,同时研究了CNT对玻璃化转变温度和凝胶含量等影响,并通过扫描电镜观察材料断面形貌,可以发现一定量的碳纳米管可以较均匀地分散在聚合物中。     

碳纳米管/环氧复合材料制备与性能研究

研究了碳纳米管管径、种类、含量以及偶联-三辊研磨-超声处理等工艺条件对碳纳米管/环氧树脂复合材料拉伸强度和电性能的影响。研究结果表明:三辊研磨-超声联用是均匀分散碳纳米管简单而有效的方法。较低的碳纳米管添加量(0.8%～4%)能大幅度提高环氧树脂的剪切强度和导电性能,添加量为3%时,复合材料的综合性能最优,即剪切强度提高了55.19%,表面/体积电阻率下降了8～10个数量级。     

碳纤维/碳纳米管-环氧树脂复合材料的耐老化性能

将环氧树脂基体与氨基化碳纳米管(MWNTs)复合,制备了碳纤维/氨基化碳纳米管-环氧树脂(CF/MWNTs-EP)复合材料。表征CF/MWNTs-EP三相复合材料的断面,并在标准条件下测试其冲击、拉伸等力学性能,研究了耐老化性能。结果表明:氨基化碳纳米管的加入明显提高了材料的耐盐雾性、耐热氧老化性和耐湿热性能。氨基化碳纳米管的加入改善了纤维与基体树脂间的界面性能,同时,促进了环氧树脂的固化,降低孔隙率,导致耐老化性能显著提高。当MWNTs-NH2的添加量(质量分数)为1.0%时,在72h和168h不同盐雾时间下,三相复合材料的耐盐雾老化性比CF/EP复合材料分别提高了61.8%和67.5%。在48h、96h和168h热氧老化时间下,三相复合材料的耐热氧老化性比CF/EP复合材料分别提高了43.5%、48.5%和41.7%。在72h和168h不同湿热时间下,三相复合材料的耐湿热老化性比CF/EP复合材料分别提高了52.8%和60.0%。     

快速固化碳纳米管/苎麻纤维/环氧树脂复合材料层板的制备与性能

针对植物纤维/树脂基复合材料高性能化问题,本研究以羟基化碳纳米管/无水乙醇分散液预先浸渍苎麻纤维织物,得到了碳纳米管分散均匀的碳纳米管/苎麻纤维多尺度复合织物,并进一步以快速固化环氧树脂为基体,采用真空辅助树脂灌注成型工艺(VARI)制备了碳纳米管改性的苎麻纤维/环氧树脂基复合材料层板(PRFC)。研究结果表明,相比未采用碳纳米管改性的苎麻纤维/环氧树脂复合材料(RFC),PRFC的弯曲强度提高14.7%,冲击强度提高20.9%。相比碳纳米管预先分散于环氧树脂基体中制备的碳纳米管改性苎麻纤维/环氧树脂复合材料(MRFC),PRFC的力学性能提高更显著。同时,PRFC的吸湿性能比MRFC和RFC的明显降低。     

多壁碳纳米管的辐照处理及其对多壁碳纳米管/环氧树脂复合材料热性能的影响

在空气中用高频高压电子加速器辐照多壁碳纳米管(MWCNTs),采用红外光谱、能谱分析、拉曼光谱和透射电镜表征分析辐照处理对碳纳米管结构的影响;通过原位复合法制备MWCNT/环氧树脂(EP)复合材料.采用场发射扫描电镜、热失重分析和动态力学分析研究辐照处理MWCNTs对环氧树脂热稳定性的影响.结果表明:电子束辐照处理使MWCNTs表面接入了少量的含氧基团,同时破坏了MWCNTs的完整结构,当辐照剂量为170 kGy时,接枝含氧基团的量最多(约为4％),且结构破坏程度较小.与原始MWCNT/EP体系相比,经电子束辐照处理后的MWCNTs在EP中分散得更均匀,并能使材料的最大热分解温度和玻璃化转变温度较纯EP有所提高,在EP中加入质量分数0.5％的经170kGy辐照处理后的MWCNTs,能够使材料的最大热分解温度和玻璃化转变温度分别提高约14℃和8℃.     

不同固化剂对MWNTs/EP复合材料导电性能的影响

采用己二胺和丙烯酰胺为原料,利用迈克尔加成反应合成了一种脂肪族胺类固化剂B,并用它与添加了多壁碳纳米管(MWNTs)的环氧树脂固化制备了B/MWNTs/环氧复合材料.利用傅立叶红外光谱、Novocontral宽频介电谱测试仪对合成固化剂B的结构及复合材料的介电性能进行了表征,并从电导、介电常数、损耗3个方面与常用固化剂DDS/MWNTs/环氧复合材料的性能进行了比较和理论分析.结果表明,固化剂种类对MWNTs/EP复合材料的电性能有较大的影响,使用含有导电π键的DDS作为固化剂要比长碳链的胺类固化剂B更容易达到逾渗点,即使添加少量MWNTs就可以达到好的电性能.     

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.