高介电常数聚合物基复合材料研究进展

本文概述了目前高介电聚合物基复合材料的主要问题,论述了铁电陶瓷、导电颗粒(金属粒子、石墨、碳纳米管)改性高介电复合材料的国内外研究进展;重点介绍了酞菁铜、聚苯胺改性全有机高介电复合材料,探讨了存在的主要问题,并指出提高介电常数、储能密度,减小介电损耗,降低制备成本是未来发展的方向。     

功能性石墨烯改善聚合物介电性能的研究进展

目的对近年来使用改性石墨烯改善聚合物基复合材料介电性能的研究进行总结,指出今后的发展方向。方法总结通过石墨烯改性来改善其在聚合物的分散性和提高聚合物基石墨烯复合材料介电性能的方法;对比石墨烯/聚合物复合材料的复合工艺对其介电常数和介电损耗数值的变化,总结不同的改性方法对复合材料介电性能的影响。结论石墨烯作为一种性能较优的导电填料对材料介电性能影响巨大,然而,由于其物理分散性不好,极大地阻碍了石墨烯改性聚合物基高介电复合材料的发展。通过对石墨烯进行功能化改性修饰可以有效提高聚合物基复合材料的介电性能,这种材料可作为电活性聚合物,在很多需要高介电常数的电介质材料领域,如超级电容器、感应器、驱动器、智能包装和机器人等方面得到应用。     

炭黑填充BST/PVDF复合薄膜的制备与介电性研究

以聚偏氟乙烯(PVDF)为聚合物基体,钛酸锶钡(BST)为陶瓷相,成本低廉的导电炭黑(CB)为导电相。采用流延加低温热处理的方法制备了一系列高介电柔性复合薄膜。利用阻抗分析仪对薄膜的介电性进行了测试,结果表明,炭黑的填充能有效提高复合材料的介电性能,当体积分数接近渗流阈值6.2%时,CB/BST/PVDF复合材料的介电常数、介质损耗、电导率急剧增加。结合经典渗流理论研究了材料在渗流转变时介电性变化特征及微观机理,利用微电容模型、界面极化理论对这一现象进行解释。     

填料含量对纳米BaTiO_3/环氧树脂复合体系介电性能的影响

通过采用机械共混法制备纳米BaTiO3/环氧树脂两相复合材料和纳米BaTiO3/环氧树脂/炭黑三相复合材料。观试了纳米BaTiO3/环氧树脂两相复合材料的微观形态、介电常数与介电损耗角正切,以及纳米BaTiO3/环氧树脂/炭黑三相复合材料的介电常数与介电损耗角正切,根据微观结构理论、极化理论以及渗流理论分析了纳米BaTiO3填料含量对纳米BaTiO3/环氧树脂复合材料微观形态和介电性能的影响,及导电相炭黑的加入对该复合体系介电性能的影响。     

聚合物基复合介电材料的研究进展

聚合物基复合介电材料是以有机聚合物为基体,将具有高介电常数或易极化的微纳米尺寸的无机颗粒或其它有机物作为填充物复合而成,综合了无机材料的高介电性能,同时还兼备聚合物的粘结性、韧性、易加工性,在信息和微电子工业等领域具有广泛应用.该领域的研究与应用的关键是材料合成路线的设计与性能的有机结合,聚合物基体与表面修饰无机颗粒界面的良好作用,使其具有优良的介电特性.将聚合物基复合介电材料的填料颗粒分为铁电陶瓷、氧化物、碳纳米管类、金属导电颗粒、全有机高分子等几种类型,并概述了各种类型的聚合物基复合介电材料的研究状况,着重分析了聚合物与无机颗粒界面的相互作用,展望了聚合物基复合介电材料未来的发展趋势.     

[C16min]Br修饰的多壁碳纳米管及其与低密度聚乙烯复合材料的制备及介电性能

为改善多壁碳纳米管(MWNT)在低密度聚乙烯(LDPE)中的分散性及复合材料的界面特性,采用溴化-1-十六烷基-3-甲基咪唑基离子液体([C16min]Br)对MWNT进行表面改性,并用Raman光谱对改性效果进行了表征。将经过修饰的碳纳米管(MIL)与LDPE熔融共混得到MIL/LDPE复合材料,采用场发射扫描电子显微镜(FESEM)和阻抗分析仪(LCR)对复合材料的结构与介电性能进行了分析。结果表明,相比与MWNT/LDPE(渗流阈值为5.2%,介电常数为82,介电损耗为0.93),MIL/LDPE(渗流阈值为9.1%,介电常数为169,介电损耗为0.51)介电常数增大,介电损耗降低。并且在低温时,MIL/LDPE介电常数随温度的变化甚小,显示出良好的温度-介电常数特性。     

半胱氨酸改性纳米Ag/PVDF复合材料制备及介电性能研究

以半胱氨酸为改性剂,对纳米Ag进行表面修饰,制备了系列改性纳米Ag/PVDF复合材料;通过对复合材料的介电性能进行研究,结果表明,改性后纳米Ag在PVDF基体中的填充量能够得到迅速提高,体积分数可达到25%以上而不发生导电现象;当改性纳米Ag/PVDF复合材料中纳米Ag体积含量达到20%时,复合材料的相对介电常数达到了115,介电损耗保持在0.09以下;通过扫描电子显微镜、傅立叶红外光谱和X射线衍射图谱分析表明,这种高介电常数,低介电损耗的性质来源于纳米Ag在聚合物基体中分散性的提高,改性纳米Ag表面连接的半胱氨酸改善了纳米Ag粒子与PVDF基体的界面相容性,提高了PVDF结晶体和纳米Ag在基体中的分散均一性,降低了聚合物基体内纳米Ag团聚和导电网络的形成几率,有效改善了金属/聚合物介电材料的加工条件,提高了聚合物的介电性能。     

新型电容器用高介电常数聚合物研究进展

高介电常数聚合物具有优异的介电性和柔韧性,可以制备高容量有机薄膜电容器等无源器件,近年来受到广泛关注.目前理论和实验研究的热点主要集中在聚合物/无机介电陶瓷、聚合物/导电颗粒复合材料和纯有机聚合物材料.综述了这3种聚合物的高介电机理及研究进展.采用物理、化学方法进行表面修饰改性,掺入导电颗粒及设计具有高度芳环结构聚合物等措施,均可有效提高介电常数、减小损耗.     

碳纳米管填充聚合物复合材料的介电性能研究

本文研究了未经处理的多壁碳纳米管/聚偏氟乙烯(MWNT/PVDF)复合材料体系的介电性能.发现,在低频下,复合材料的介电常数随MWNT的含量增加而迅速增加,当体积分数为2.0%时,介电常数高达300左右,并且复合材料的渗流阈值仅为1.61%(体积分数).MWNT较大的长径比和较高的电导率导致复合体系渗流阈值较低.发生渗流效应时,复合材料的介电损耗低于0.4,与频率无关.因此,可以认为未经过化学处理的碳纳米管可以大幅度改善PVDF基复合材料的介电性能.     

高介电常数、低介电损耗聚合物复合电介质材料研究进展

高介电常数聚合物电介质材料作为当今信息功能材料的研究热点,具有实际的应用价值和前景。综述了聚合物基复合电介质材料的分类及优缺点,以及从材料微观结构设计和填料界面修饰出发(如三元杂化或设计核壳和三明治结构),来获得高介电常数、低介电损耗聚合物复合电介质材料的研究状况和应用前景,以期对高介电、低损耗聚合物基电介质材料有一个更直观全面的了解,进一步拓展该类材料在电气和生物工程领域的研究和应用。     

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.     

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.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

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.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.     

新闻(英文)

正China and Greece Sign the Standardization Cooperation Agreement Witnessed by Chinese Premier Li Keqiang and Greek Prime Minister Antonis Samaras,AQSIQ Minister Zhi Shuping and ELOT Chairman and Executive Director Angelos Tolkas signed the SAC-ELOT Standardization Cooperation Agreement.The Agreement is one of the critical cooperation documents signed during Li Keqiang’s visit in Greece,encouraging China and Greece to