铁氧体基核壳结构复合吸波材料研究进展

核壳结构复合吸波材料因其独特的物理化学特性和良好的吸波能力,近年来成为研究的热点。本文综述了近年来有关铁氧体基核壳结构复合吸波材料的研究成果。介绍了核壳结构吸波材料吸波原理的研究进展,然后将铁氧体基核壳结构复合吸波材料的研究成果系统归纳为四大类,即金属微粉/铁氧体复合,不同类型铁氧体复合,导电高聚物/铁氧体复合、其他复合类型,评述了其特点。指出了铁氧体基核壳结构复合吸波材料未来研究亟待解决的问题和发展方向。     

核壳结构电磁波吸收材料研究进展

微波通信技术的发展和广泛应用,在方便人们生活的同时,产生的大量电磁波会对环境造成污染,从而威胁人们的身体健康。电磁波吸收材料(也称吸波材料)可以吸收多余的、泄漏的电磁波能量,在治理电磁波污染方面有着十分重要的经济价值与社会效益。此外,在军事工业领域,雷达隐身飞机、导弹、作战指挥车等军事装备也对吸波材料有着极为紧迫的需求,不仅要求吸波材料具有薄、轻、宽、强的特点,还要求其具有耐高温、抗氧化、高强度等性能。传统吸波材料(如铁氧体、羰基铁、导电炭黑)的损耗机制单一,导致其吸波频带窄、吸收能力不够强,复合化处理就成为获得优良性能吸波材料的必要手段。通常人们采取多层宏观尺度结构匹配的方式来达到宽波段吸收的目的,但通过该方法得到的吸波材料匹配厚度大,适用领域十分有限,很难同时满足吸波材料薄、轻、宽、强的要求。纳米科学技术的发展使得材料的设计与制备拓展到了原子级别,人们试图从纳米尺度上对吸收材料进行阻抗匹配设计与损耗能力改进,其中核壳结构吸波材料由于结构设计自由度大、性能优异,逐渐成为该领域的研究热点。近年来,对核壳结构吸波材料的探究主要是从材料本身的特性出发,采用不同损耗特性的材料进行包覆,并结合对材料微观结构和形貌的设计,来提高吸波材料的匹配特性和有效波频带宽度。其中,具有中空核壳结构和各向异性的材料(如二维片状、纳米花状、纳米管状)表现出更优异的吸波性能。此外,可选用陶瓷材料和耐温树脂作为壳层材料,以满足吸波材料的耐高温和抗氧化性能的要求。目前虽对核壳结构吸波材料的报道较多,但其研究体系尚未统一,吸波调控机理也仍有待深入研究。本文基于核壳结构吸波材料最新的研究进展,介绍了已报道的核壳结构吸波材料的类型,分析了核壳结构吸波材料的微观调控机制和制备方法。最后,对核壳结构吸波材料的发展进行了总结和展望。     

表面改性空心微珠吸波材料的研究进展

综述了4种空心微珠的类型、表面改性方法以及其作为吸波材料的国内外研究状况,指出了表面改性空心微珠作为吸波材料的不足之处,提出了新型的空心陶瓷微珠吸波材料的制备方法及其发展方向。     

轻质核壳结构吸波材料的研究进展

随着现代科技的发展,电磁波辐射对人类的影响越来越大,在电子电路中释放的电磁波会破坏其他设备的性能并且损害人体健康,因此吸波材料的研究显得尤为重要。此外,具有优良电磁性能的复合吸波材料还可以用于制备飞行器隐身材料。这是因为高强度的微波吸收材料具有良好的介电损耗和磁性损耗,同时具有优越的阻抗匹配,而核壳结构的吸波材料是复合吸波材料中较为理想的材料。本文详细介绍了核壳结构吸波材料的合成方法,并根据核壳结构材料的分类及具体应用,阐述了近年来国内外核壳结构吸波材料的最新研究进展。     

粉煤灰空心微珠的Co-Ni-P化学镀及镀层的吸波性能

为了实现吸波材料的薄型化及轻量化,采用化学镀工艺对粉煤灰空心微珠(5μm级)进行表面电磁改性,制备出"核-壳"结构新型轻质复合粉体吸波材料,探讨了Co-Ni-P化学镀工艺参数对吸波性能的影响.借助SEM,EDS和微波矢量网络分析仪研究了施镀工艺参数对镀层形貌、成分与吸波性能的影响.结果表明,空心微珠表面镀层由粒径0.5...     

基于掺杂聚苯胺的核壳型电磁屏蔽/吸波复合材料研究进展EI北大核心CSCD

掺杂聚苯胺(PANI)具有合成方法简单、电导率可调、质量轻、价格低廉、性能稳定等优点,使其成为一种性能优良的本征型电导高分子。为实现日益提高的高性能电磁屏蔽/吸波材料的应用要求,需要将掺杂PANI和其他材料复合使用。核壳结构材料整合了核与壳材料的优点,通过改变核和壳的化学组成、组分和形貌,可以调控材料的性能,拓展其应用范围。文中回顾了近5年来,尤其是近3年来掺杂PANI用于核壳型电磁屏蔽/吸波材料的一系列研究工作。从材料的制备、结构、性能、屏蔽/吸波机理等方面进行了阐述,并对其发展前景进行了展望。     

基于掺杂聚苯胺的核壳型电磁屏蔽/吸波复合材料研究进展

掺杂聚苯胺(PANI)具有合成方法简单、电导率可调、质量轻、价格低廉、性能稳定等优点,使其成为一种性能优良的本征型电导高分子。为实现日益提高的高性能电磁屏蔽/吸波材料的应用要求,需要将掺杂PANI和其他材料复合使用。核壳结构材料整合了核与壳材料的优点,通过改变核和壳的化学组成、组分和形貌,可以调控材料的性能,拓展其应用范围。文中回顾了近5年来,尤其是近3年来掺杂PANI用于核壳型电磁屏蔽/吸波材料的一系列研究工作。从材料的制备、结构、性能、屏蔽/吸波机理等方面进行了阐述,并对其发展前景进行了展望。     

无机-有机复合吸波材料研究进展

介绍了无机吸波材料和有机吸波材料种类、特点及研究现状;阐述了无机一有机复合材料的吸波机理.重点分析了核一壳结构、纳米结构、膜结构及管状结构等不同结构无机一有机复合吸波材料制备方法、性能的研究现状,最后指出了该研究领域中存在的不足及研究发展方向.     

国外军用新型吸波材料专利技术研究进展

综述了国外军用新型吸波材料专利技术研究进展,包括智能吸波材料、手性吸波材料、导电聚合物和泡沫吸波材料。介绍了军用新型吸波材料专利的申请情况,重点阐述了相关专利技术的特点或优势、新型吸波材料或设备的制备方法及潜在军事应用,提出了对我国新型吸波材料技术研究的新思路和方法。     

核壳结构有机/无机复合微球的制备与应用进展

根据核、壳的组成,核壳结构有机/无机复合微球可以分为2类:A类是核为无机材料,壳为高分子材料的核壳式结构;B类是核为高分子材料,无机材料作为壳层的核壳式结构.综述了B类复合微球的研究进展,详细讨论了复合微球的制备方法,如原位化学沉积法、溶胶-凝胶法、化学镀法、自组装法,并对各种制备方法的优缺点进行了总结,介绍了复合微球在轻质雷达吸波材料、光子晶体、生物医药载体材料、化妆品等领域的应用.最后指出了该研究领域未来的发展方向.     

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.     

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.……     

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.……     

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.     

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.