含结晶水无机盐对复合材料吸波性能的影响——材料研究新思路探索

通过在毕业论文研究中对乙炔炭黑(CB)和含结晶水无机盐吸波剂填充丁腈橡胶(NBR)吸波性能的探索，不但对得到了具有良好吸波性能的材料，而且还得到了良好的科学研究思想方法的训练，提高了动手能力。     

宽频高性能短切碳纤维/聚氨酯泡沫吸波材料制备

采用两种不同长度的短切碳纤维做填充吸收剂制备聚氨酯硬质泡沫基复合吸波材料,使用微波矢量网络分析仪系统和弓形法测量该类复合材料的微波吸收性能,研究了两种不同长度的短切碳纤维单独应用以及复合应用时,填充质量分数、混合填充比、总填充量以及匹配层对聚氨酯泡沫吸波复合材料在8~18 GHz频段吸波性能的影响。结果表明,短切碳纤维的最佳填充质量分数为7%,短切碳纤维T1和T2的最佳混合填充比为3∶4;匹配层引入可进一步改善X波段和Ku波段的宽频吸波性能,在X波段和Ku波段可实现全频段优于-10 d B的吸波性能,峰值达-21.1 d B。     

填充吸波泡沫的碳纤维复合材料格栅结构吸波性能计算

采用空间回路网法计算得到填充吸波泡沫的碳纤维复合材料格栅结构的电磁散射性能。根据格栅结构的周期性排布特征,采用Floquet 定理分析结构的周期性边界条件,将计算模型简化为一个周期单元进行电磁场分布计算。通过计算结果分析结构在不同频率、不同单元体尺寸下的吸波性能。计算表明：对于含吸波泡沫的复合材料格栅结构,其吸波性能明显好于未填充结构;格栅单元中所填充的泡沫厚度以及泡沫体积分数是影响格栅结构吸波性能的2个主要因素。     

碳纳米管与二硫化钼协同增强丁腈橡胶复合材料吸波性能

利用不同维度的多壁碳纳米管(MWCNTs)和二硫化钼(MoS_2)在形貌和性能上的互补性,通过机械共混制备了电磁性能优异的丁腈橡胶(NBR)吸波复合材料;采用X射线衍射、拉曼光谱、扫描电镜和矢量网络分析仪(VNA)对复合材料结构和性能进行了表征分析,研究了MWCNTs与MoS_2比例对复合材料电磁性能的影响。研究结果表明,MWCNTs和MoS_2共掺协同促进了彼此在NBR基体中的分散,形成更完善的电磁损耗网络;与单纯MWCNTs或MoS_2填充的NBR复合材料相比,NBR/MWCNTs/MoS_2复合材料的吸波性能提高了2.3倍以上;当MWCNTs/MoS_2体积比为5/5时,复合材料的吸波效能最优,反射损耗峰值达到-31.08 dB,有效吸收带宽达到3.04 GHz。对复合材料电磁波衰减机理分析表明,MWCNTs和MoS_2共掺调和了彼此的电磁参数,使复合材料具有较为平衡的阻抗匹配度和衰减常数,促进了复合材料对电磁波的衰减。     

碳黑/无机材料填充聚合物复合材料的微波吸收特性

研究了以乙炔碳黑和无机材料填充PVC复合材料的吸波性能。就无机材料的种类，配比及是否添加局炔碳黑等因素对吸波性能的影响进行了分析讨论。结果表明，在复合材料中，填充的无机材料的极性对吸收性能有影响；填充乙炔碳黑，材料具有良好的吸收性能；而乙炔碳黑和水合氧化铝混合填充复合材料的最大吸收衰减可达21.87dB。     

EPS水泥复合材料的吸波性能与抗压性能研究

对发泡聚苯乙烯(EPS)填充水泥基体复合材料的吸波性能与抗压性能进行了实验研究.结果表明,EPS填充水泥基体复合材料具有良好的吸波性能,而且EPS填充率和颗粒直径对材料的吸波性能具有明显的影响.当EPS填充率为60%vol.,直径为1 mm时,材料在8～18 GHz频段内可以实现-8～-15dB的吸收,吸收超过-10dB的带宽为6.2GHz.EPS水泥复合材料的抗压强度与EPS填充率存在一定的线性关系,直径为1mm的EPS较3mm EPS填充的复合材料具有更大的抗压强度.     

CB/ABS连续导电介质吸波性能研究

通过热压方法制备了炭黑(CB)/ 丙烯腈-丁二烯-苯乙烯共聚物(ABS)连续导电介质吸波平板,研究了炭黑含量和厚度对CB/ABS连续导电介质介电常数和吸波效能的影响.结果表明炭黑/ABS连续导电介质的介电常数和介电损耗角正切随炭黑含量的增加而增大;在炭黑含量达到20%(质量分数)时,复合平板的吸收峰值达到最佳,对应于其体积电阻率为105Ω·cm;复合平板的厚度增加有助于改善其吸波性能.修正的Rayleigh混合有效介电常数和广义反射率计算公式计算导电介质吸波性能有很好的实用性.     

蜂窝状三维整体机织结构型吸波复合材料的设计、制备与性能

为了解决蜂窝夹层结构材料的开裂和分层问题,以玄武岩纤维长丝纱和碳纤维长丝纱为原料,在普通织机上,经合理设计,织造了顶层为透波层、中间层为吸波层和底面为反射层的蜂窝状三维整体机织结构型吸波织物;其次,以蜂窝状三维整体机织结构型吸波织物为增强体,双酚A型环氧树脂为基体,羰基铁粉(CIP)和炭黑(CB)为吸波剂,采用真空辅助树脂传递模塑(VARTM)成型工艺,制备了不同结构参数的蜂窝状三维整体机织结构型吸波复合材料;最后,采用矢量网络分析仪和万能试验机分别对蜂窝状三维整体机织结构型吸波复合材料的吸波性能和力学性能进行研究。研究表明,其有良好的整体性能,兼具吸波和承载能力。     

CB/PBO复合材料制备及吸波性能研究

以4, 6二氨基间苯二酚盐酸盐(DAR?2HCl)、对苯二甲酸(TPA)为原料, 合成TA盐, 再缩聚制得具有较高耐热性的聚对苯撑苯并二噁唑(PBO)。以PBO为基体, 炭黑(CB)为吸收剂, 热压法制备CB/PBO复合材料。对不同炭黑质量分数的复合材料介电及PBO基体与复合材料的热性能进行研究。结果表明, 随着炭黑含量的增加, 材料的复介电常数的实部与虚部均增大。含5%炭黑的试样厚度达到2 mm时, 吸波性能最好, 反射率小于-10 dB的带宽可达2.4 GHz, 最小反射率可达-32 dB。在空气中450℃保温5 h, PBO的质量损失为11.84%, 而5% CB/PBO复合材料的质量损失为21.99%。     

含电路模拟结构吸波复合材料

研究了电路模拟结构材质、电路模拟结构尺寸、介质层电磁参数等对电阻渐变型和"陷阱"式结构吸波复合材料的吸波性能和力学性能的影响。结果表明:通过合理的结构设计,在其它条件相同的情况下含电路模拟结构电阻渐变吸波复合材料的吸波性能在8~18 GHz范围内有3~5 dB的提高;含电路模拟结构"陷阱"式吸波复合材料在厚度≤4 mm条件下,实现了吸波性能在8~18 GHz频率范围内吸收率≥12 dB。在提高吸波复合材料吸波性能的同时,电路模拟结构的引入使复合材料力学性能有一定的提高,有利于实现吸波复合材料的吸波/承载一体化。      

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.     

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.……     

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.     

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.     

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.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

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.     

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