表面官能团化多壁碳纳米管对环氧树脂固化过程的影响

以4,4‘-二胺基二苯砜(DDS)为固化剂,将表面化学修饰的MWNT作为填料加入到环氧树脂中,制备了MWNT/环氧树脂复合材料,采用非等温DSC研究了MWNT对环氧树脂固化过程的影响.结果表明,表面化学修饰的MWNT能促进环氧树脂的固化,降低固化反应的起始温度和峰顶温度;根据Kissinger公式和Crane经验方程推出了固化反应的表观活化能、反应级数、频率因子和速率常数;根据不同升温速率下的DSC固化反应放热曲线确定了固化工艺参数.     

玄武岩纤维对环氧乙烯基酯树脂基体固化特性的影响

根据纯环氧乙烯基酯树脂和加入玄武岩纤维以后的DSC曲线,研究了玄武岩纤维对环氧乙烯基酯树脂固化特性的影响,并得出了动力学方程。结果表明,玄武岩纤维的加入使环氧乙烯基酯的DSC曲线放热峰前移且变的尖锐,反应活化能降低,反应级数下降,使固化反应速度提高,固化工艺温度降低。     

用于CIRTM工艺的环氧树脂酚醛树脂的固化工艺研究

采用动态差示扫描量热(DSC)法,研究了用于CIRTM工艺的E-44/GA327(DDM改性芳胺)环氧体系和苯并噁嗪酚醛树脂的固化过程,以及升温速率对固化体系DSC曲线的影响,并采用最佳固化温度外推法确定了两种树脂的最佳共固化制度。结果表明,苯并噁嗪固化反应表观活化能Ea为70.35kJ/mol,表观指前因子A为1.27×107s-1,反应级数n为0.897;E-44/GA327体系固化反应表观活化能Ea为44.04kJ/mol,表观指前因子A为1.78×104s-1,反应级数n为0.884。两种树脂的最佳共固化制度为140℃/240min+180℃/240min,按所确定的共注射树脂的固化工艺制备了浇铸体,苯并噁嗪和E-44/GA327的固化度分别达到了96.7%和98.3%,固化物力学性能良好,验证了固化工艺的合理性。     

840S 环氧树脂体系固化反应特性

用差示扫描量热法(DSC) 在动态条件下对840S 环氧树脂体系的固化反应动力学进行了研究。根据所测量的不同升温速率的DSC 曲线, 运用温度升温速率( T-β) 图外推法得到该环氧树脂体系的固化工艺参数, 即凝胶化温度、固化温度、后处理温度, 这些温度参数为制定合理的固化工艺提供了理论基础。采用Kissinger 方程和Crane 方程计算该840S 环氧树脂体系的动力学参数, 即表观活化能E_a 、表观频率因子A 和反应级数n 。根据所计算的动力学参数, 建立了该840S 环氧树脂体系的固化动力学模型。利用所建立的固化动力学模型分别预测了等温和动态条件下840S 环氧树脂体系的固化反应特性。      

纳米氧化铝颗粒增强TDE-85型环氧树脂的固化动力学和力学性能研究

用超声分散法和程序温度固化制备了纳米氧化铝颗粒增强TDE-85型环氧树脂复合材料,研究了添加纳米氧化铝颗粒对环氧树脂固化动力学和力学性能的影响.根据示差扫描量热法(DSC)曲线,由Kissinger方法和Ozawa方法计算了固化体系固化反应的活化能,用Kissinger公式计算了Arrhenius指前因子,并用Crane方法计算了固化体系的反应级数.研究结果表明,添加纳米氧化铝颗粒增加了体系固化反应的活化能,但对反应级数和Arrhenius指前因子的影响较小;当纳米氧化铝添加量为1wt%(环氧树脂的质量分数)时,复合树脂的拉伸强度提高19%;伸长率提高34.5%.     

非等温差示扫描量热法研究杂萘联苯聚芳醚酮改性环氧树脂体系的固化动力学

采用非等温差示扫描量热仪(DSC)对环氧树脂(E-51)/杂萘联苯聚芳醚酮(PPEK)共混物的固化过程进行研究。利用T-β外推法确定了固化工艺温度,并利用Kissinger和Crane法计算得到共混体系固化反应的表观活化能Ea、指前因子A、固化反应级数n等动力学参数。结果表明,PPEK的加入对环氧树脂的固化反应温度影响不大,但反应活化能有所升高,表明PPEK的加入阻碍了固化反应的进行。通过固化度与固化时间的关系曲线证明,PPEK的加入不改变环氧树脂的固化反应机理。     

钛酸酯催化环氧树脂固化动力学研究

用FTIR“原位”技术,研究了钛酸酯(Tc-114)偶联剂对环氧E-44和二氨基二苯基甲烷(DDM)固化反应的催化作用,得出固化程度与时间的关系曲线。又根据DSC曲线,分别算出加有Tc-114和不加Tc-114的两个固化体系的反应表观活化能和反应级数。结果表明,Tc-114的存在使环氧固化反应活化能降低,催化作用明显。     

风机叶片用环氧树脂的固化动力学研究

通过动态DSC(差示扫描量热法)研究了佳发JH-239、惠利LT-5078A等两种风机叶片用环氧树脂的固化动力学特征温度,并采用Kissinger、Crane法确定它们的固化动力学参数.结果表明:佳发树脂体系的表现活化能为40.60 kJ/mol,惠利树脂体系的表现活化能为45.91kJ/mol,而二者的反应级数分别为...     

复合材料胶粘剂固化反应及工艺参数的研究

本文用PERKIN-ELMER公司(简称P-E公司)的DSC-7仪器测定了SY—25胶膜的固化反应.根据DSC测试原理建立的动力学方程,通过DSC—7动力学软件,求出SY-25胶膜的固化反应动力学参数-固化反应表观活化能(E_a)、反应级数(n)以及表观频率因子(Z).利用已得到的动力学参数值,进一步预测SY-25胶膜的固化反应程度(α)、固化反应温度(T_{c相似文献}   

聚氨酯改性TDE-85/E-51环氧树脂的固化反应

以混合芳胺为固化剂,通过聚氨酯(PU)对4,5-环氧环己烷-1,2-二甲酸二缩水甘油酯(TDE-85)与二酚基丙烷缩水甘油醚(E-51)环氧树脂的混合树脂体系的改性,制备了高性能聚氨酯改性环氧树脂(PU/EP)。通过差示扫描量热法(DSC),确定了PU/EP体系的最佳固化条件,并探讨了PU/EP体系的固化反应动力学特征。研究结果表明,PU/EP体系的最佳固化条件为:25℃12h+150℃2h。PU/EP体系的固化反应活化能为69.18kJ/mol,反应级数为0.901。     

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.……     

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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