热处理效应对Sn-Al与Sn-Ca纳米薄膜的电磁屏蔽机制

利用溅镀Sn-Al纳米薄膜和Sn-Cu纳米薄膜讨论结晶机制与膜厚对电磁波屏蔽特性的影响,比较了Sn-Al和Sn-Cu薄膜的高温显微组织、导电性与电磁波屏蔽性能。结果表明,高温处理提高了Sn-Al纳米薄膜的电磁波屏蔽性。在低频条件下,高Cu摩尔浓度的Sn-Cu纳米薄膜不能有效改善电磁波屏蔽性;高温处理后,低Cu摩浓度的Sn-Cu纳米薄膜能提高低频的电磁波屏蔽性,而高频下的电磁波屏蔽性则呈相反趋势。     

电磁屏蔽材料及其测试技术研究

随着电磁污染及电磁波泄漏的日益严重,以电磁干扰（EMI）屏蔽材料为代表的电磁防护材料已经广泛应用在军用、民用电子设备中。目前,利用本征电磁性能制备的金属型EMI屏蔽材料,将高导电层与绝缘基体相结合的涂覆型EMI屏蔽材料,以及具有优良柔性的EMI屏蔽织物已经能够大批量生产。具有柔性、透明、可变形的新型EMI屏蔽材料日益增多,满足市场对材料多功能性、极端环境适用性、加工装配便捷性的新需求。EMI屏蔽测试技术在现有近场、远场测试技术基础上也呈现多元化、精细化的发展趋势。     

Polypyrrole-based conducting hot melt adhesives for EMI shielding applications

Intrinsically conducting hot melt adhesives (ICHMAs) have been developed, based on polypyrrole (PPy) blends, for use in electronic and telecommunication applications requiring shielding against electromagnetic interference (EMI). These advanced materials have been formulated to exhibit significant EMI shielding effectiveness (SE) while retaining the superior properties of conventional hot melt adhesives. The conductivity properties, adhesion characteristics and both near- and far-field EMI SE behaviour of these ICHMAs at room temperature are investigated as a function of PPy content. The environmental stability of the conductivity is also reported. Potential use of such new materials in current and future electronic applications is anticipated.     

Microwave absorption,reflection and EMI shielding of PU–PANI composite

In order to allow electronic components to coexist without harmful electromagnetic interference (EMI) it is necessary to develop new shielding and absorbing materials with high performance and a large operating frequency band. Conducting polymer composites have been found to be suitable for EMI shielding and for the dissipation of electrostatic charge. In the present study polyaniline–polyurethane (PANI–PU) composite was considered for these applications. The microwave absorption, microwave reflection and EMI shielding properties of PANI–PU composite is evaluated both at S-band and X-band frequencies. The material is found to have good microwave absorption and is a potential candidate for EMI shielding applications.     

Enhanced Electromagnetic Interference Shielding of Mg–Zn–Zr Alloy by Ce Addition

The effects of Ce addition on microstructure and electromagnetic interference(EMI) shielding response of Mg–6Zn–0.5Zr(ZK60) alloy have been investigated.Ce addition resulted in grain refinement and higher density of Mg–Zn–Ce and Mg Zn2 intermetallic particles in the alloy.In particular,this was substantially remarkable as the addition of Ce was up to 1.0 wt%.It is interesting to note that as-extruded ZK60 alloy with 1.0 wt% Ce addition exhibited an EMI shielding effectiveness(SE) exceeding 70 d B at the frequency range of 30–1,500 MHz,which was significantly higher than that of ZK60 alloy without Ce addition and reached the requirement of high protection.The superior SE was probably related to the increased reflection and multiple reflection of electromagnetic radiation induced by Ce addition.Direct artificial aging at 150 °C for 25 or 50 h led to a further increase of 7–10 d B in the SE of the alloy with 1.0 wt% Ce addition.The advantages of excellent shielding capacity and favorable mechanical strength make the Mg–Zn–Zr–Ce alloy an attractive shielding candidate material for a variety of technological applications.     

热处理温度对有序介孔碳微结构和电磁屏蔽性能的影响(英文)

通过模板法制备了有序介孔碳(OMC),研究了有序介孔碳粉体在8.2～12.4GHz(X波段)范围内作为轻质电磁波吸收剂的电磁屏蔽性能。在氮气保护的条件下对OMC粉体分别在1400、1600和1800℃进行2h热处理。研究了热处理前后OMC微结构的变化,并测试了所得OMC粉体的介电常数。在1400℃下热处理所得OMC粉体试样的损耗正切(tanδ)高达3.1,远远高于未进行热处理的OMC试样的。通过将总的屏蔽效能分解为吸收和反射两部分,研究了OMC试样的电磁屏蔽效能。于1400℃和1600℃热处理后,OMC得到最高的电磁屏蔽效能其屏蔽机制以吸收为主,表明OMC具有作为微波吸收剂的潜力。     

Enhanced Electromagnetic Interference Shielding in a Duplex-Phase Mg-9Li-3Al-1Zn Alloy Processed by Accumulative Roll Bonding

High electromagnetic shielding performance was achieved in the Mg-9Li-3Al-1Zn alloy processed by accumulative roll bonding(ARB).The microstructure,electromagnetic interference shielding effectiveness(SE) in the frequency of 30-1500 MHz and mechanical properties of the alloy were investigated.A model based on the shielding of the electromagnetic plane wave was used to theoretically discuss the EMI shielding mechanisms of ARB-processed alloy.Results indicate that the SE of the material increases gradually with the increase in the ARB pass.The enhanced SE can be attributed to the obvious microstructure orientation caused by ARB,and the alternative arrangement of alpha(Mg) phase and beta(Li)phase.In addition,with the increase in ARB pass,the number of interfaces between layers increases and the grain orientation of each layer tends to alignment along c-axis,which is beneficial to the reflection loss and multiple reflection loss of the incident electromagnetic wave.     

开孔泡沫Fe-Ni的电磁屏蔽性能

利用专利技术制备了开孔泡沫Fe-Ni材料,并对其电磁屏蔽效能进行了研究。结果表明,在0.03～1500MHz的频率范围内,开孔泡沫Fe-Ni的屏蔽效能在60～85dB之间,屏蔽效能良好;而在0.03～400MHz范围内,其屏蔽效能与铝合金板的屏蔽效能相当。开孔泡沫Fe-Ni的电磁屏蔽效能主要受泡沫结构的影响,随着开孔孔径以及泡沫体孔隙率的减小其电磁屏蔽效能增加显著。而当材料的孔径以及厚度一定时,泡沫体孔隙率的变化对电磁屏蔽效能的影响较其他因素小。     

浸渍式提拉法制备TiO2薄膜的微观结构和润湿性

目的研究工艺参数与TiO_2薄膜的微观结构、光学性质及润湿性的关系。方法以钛酸四丁酯为原料,乙醇为溶剂,采用溶胶-凝胶浸渍式提拉法,改变工艺参数(提拉次数、提拉速度),在玻璃衬底上制备了TiO_2薄膜,并通过光学表面形貌仪、紫外可见分光光度计及接触角测试仪分析了不同参数下制备的TiO_2薄膜的微观结构、光学性质和润湿性。结果提拉次数和提拉速度都会影响薄膜的微观结构,提拉2次,提拉速度在3~7 cm/min之间制备的TiO_2薄膜表面平整、致密。在提拉方向上,存在厚度梯度,厚度梯度为1 nm/μm。透射光谱显示TiO_2薄膜在可见光区透明,吸收边与提拉工艺有关,提拉速度为7 cm/min,提拉2次制备的TiO_2薄膜,禁带宽度为3.57 e V,此时,接触角为14.8°。结论提拉速度、提拉次数影响TiO_2薄膜的微观结构、光学性质和润湿性。通过提拉工艺参数的调整,可以制备均匀致密、具有亲水性的半导体TiO_2薄膜。     

Recent advances of electromagnetic interference shielding Mg matrix materials and their processings: A review

In terms of lightweight electromagnetic interference (EMI) shielding structural materials, Mg matrix materials have proven to be the best, due to their exciting properties (e.g. low density, high specific strength, good electrical conductivity and excellent EMI shielding properties) and their wide range of applications in lightweighting in electronics, automotive and aerospace industries. Through processing, such as alloying, heat treatment, plastic deformation and composite processing, Mg matrix materials can be obtained with tailorable properties which can play a key role in designing materials for EMI shielding. This work introduces an overview of the research on the EMI shielding properties of Mg matrix materials as well as their EMI shielding mechanisms over the past few decades, focused on the influence of alloying, heat treatment, plastic deformation and composite processing for the EMI shielding properties of Mg matrix materials. At the end, conclusions and future perspectives are provided.     

N2流量对室温磁控溅射制备Ti-N薄膜太阳能光谱吸收特性的影响

利用非平衡磁控溅射技术,在室温条件下制备了一系列不同N2流量的Ti-N薄膜,研究了N2流量对薄膜微观形貌和光学性能的影响。根据分析结果设计并制备了四层结构的Ti-N太阳能选择性吸收薄膜,通过软件对薄膜进行了优化设计并进行了实验验证。结果表明,随着N2流量的增加,薄膜的微观形貌发生变化,逐渐出现气泡状沉积物及气泡破裂状形貌,直至变为无定型态。通过紫外-可见-近红外光谱分析可知,选用合适的工艺可有效提高太阳能吸收薄膜光学性能,利用软件对薄膜进行优化设计可使薄膜光学性能获得进一步改进,经过优化的薄膜吸收率达0.9048,可用作太阳能光谱选择性吸收薄膜。     

Fabrication and characterization of ITO thin films on heat-resistant transparent flexible clay films

Transparent conductive indium tin oxide (ITO) thin films were deposited on transparent flexible clay films with heat resistant and high gas barrier properties by rf magnetron sputtering. The electrical, structural, and optical properties of these films were examined as a function of deposition temperature. A lowest resistivity of 4.2 × 10^− 4 Ωcm and an average transmittance more than 90% in the visible region were obtained for the ITO thin films fabricated at deposition temperatures more than 300 °C. It was found that ITO thin films with low resistivity and high transparency can be achieved on transparent flexible clay film using conventional rf magnetron sputtering at high temperature, those characteristics are comparable to those of ITO thin films deposited on a glass substrate.     

填料形状对Fe@Ag核壳复合粒子的电磁特性的影响

运用液相化学还原Ag技术,制备了球形和片形2种Fe@Ag核壳复合粒子.表征了这2种屏蔽填料的物相、表面形貌和化学组成,研究了其静磁性能,分析了填料的形状对复合材料的复磁导率、电导率和屏蔽效能等电磁特性的影响.结果表明:2种复合粒子均为核壳结构完整的Fe@Ag核壳复合粒子,其Ag壳层均匀且致密;球形和片形Fe@Ag核壳复合粒子均具有良好的软磁性能;与形状各向同性的屏蔽填料相比,以片形Fe@Ag核壳复合粒子为填料的电磁屏蔽复合材料的复磁导率更高,体积电阻率更低,该复合材料在电磁波频率范围为30—1500 MHz内的屏蔽效能(SE)为-51—-55 dB,优于以球形Fe@Ag核壳复合粒子为填料的电磁屏蔽复合材料.并且从理论上分析了片形Fe@Ag核壳复合粒子的电磁屏蔽复合材料对电磁波的吸收损耗更强和屏蔽效能更高的物理本质.     

Materials for electromagnetic interference shielding

Materials for the electromagnetic interference (EMI) shielding of electronics and radiation sources are reviewed, with emphasis on composite materials and resilient EMI gasket materials, which shield mainly by reflection of the radiation at a high frequency.     

Effect of Al Film on the Electromagnetic Properties of Glass Fiber Reinforced Resin Matrix CompositeEI北大核心CSCD

Metallic thin films have many properties that bulk metals do not possess, such as high impedance. Recently, increasing attention has been paid to high impedance surface in the design of antennas and absorbers. Metallic thin films used in composite materials can realize the perfect matching of electromagnetic wave in different materials. The use of metallic thin films in electromagnetic functional materials results in significant increase of the absorbing intensity and operating bandwidth. But it usually needs to pay a huge amount of manpower, material resources and a longer period of time to design excellent electromagnetic functional materials with metallic films. So it is greatly significant to understand clearly the electromagnetic influence of metallic film for designing excellent performance materials and saving costs by simulation software. Al film is a typical non-magnetic metal film. In this work, the electromagnetic reflectivity of Al films and glass fiber reinforced resin matrix composite had been studied. High frequency electromagnetic field calculation software FEKO was employed to calculate the reflection coefficient of the composites. The effect of composites' real part of permittivity epsilon(r), dielectric loss tangent tan delta(epsilon), permeability mu(r) and magnetic loss tangent tan delta(mu) on microwave reflectivity had been discussed. The equivalent electromagnetic parameters of glass fiber reinforced resin matrix composite had been obtained through a comparison between simulation and experimental results. Due to resonance phenomena of the embedded Al film in the glass fiber reinforced resin matrix composite with certain thickness, there is an optimum resistance value of Al film that makes the composite structure have minimum reflection. Through the calculation of Al film and glass fiber reinforced resin matrix composite with different structure, the thickness relationship between Al films in calculation and Al films prepared by magnetron sputtering had been obtained. According to the theory of transmission line, the resistance of resonance is analyzed by MATLAB. This method is also applicable to the resistance solution of the homogeneous metal films at any position in the composite or frequency selective surfaces. The equivalent electromagnetic parameters of Al film and glass fiber reinforced resin matrix composite in simulation had been ascertained, and the simulation results agree well with the experimental results.     

Effect of annealing on pulsed laser deposited zirconium oxide thin films

Zirconium oxide thin films were deposited using pulsed laser ablation from a ceramic ZrO₂ target on unheated substrates. Subsequently, the films were annealed in air in the temperature range 400-800 °C. The films were characterized by X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, and optical spectroscopy to investigate the variation of the structural, chemical, and optical properties upon annealing. As-deposited films were amorphous and had a large surface density of ablated particles. Annealing resulted in the growth of monoclinic nano-crystalline, uniform, and transparent films that were slightly sub-stoichiometric. The annealed films were compact and had high values of the refractive index. Extinction coefficients were small, and may be related to the presence of defects. The films exhibited the presence of an indirect band gap, related to defects, and a direct band gap, related to fundamental absorption.     

Dielectric characterization of conducting textiles using free space transmission measurements: Accuracy and methods for improvement

The dielectric behaviour of in-situ polymerized thin polypyrrole (PPy) films on synthetic textile substrates were obtained in the 1–18 GHz region using free space transmission and reflection methods. The PPy/para-toluene-2-sulphonic acid (pTSA) coated fabrics exhibited an absorption dominated total shielding effectiveness (SE) of up to −7.34 dB, which corresponds to more than 80% of incident radiation. The permittivity response is significantly influenced by the changes in ambient conditions, sample size and diffraction around the sample. Mathematical diffraction removal, time-gating tools and high gain horns were utilized to improve the permittivity response. A narrow time-gate of 0.15 ns produced accurate response for frequencies above 6.7 GHz and the high gain horns further improved the response in the 7.5–18 GHz range. Errors between calculated and measured values of reflection were most commonly within 2%, indicating good accuracy of the method.     

Effect of annealing treatment on the structural, optical, and electrical properties of Al-doped ZnO thin films

Highly conductive and transparent Al-doped ZnO (AZO) thin films were prepared from a zinc target containing Al (1.5 wt.%) by direct current (DC) and radio frequency (RF) reactive magnetron sputtering. The structural, optical, and electrical properties of AZO films as-deposited and submitted to annealing treatment (at 300 and 400 ℃, respectively) were characterized using various techniques. The experimental results show that the properties of AZO thin films can be further improved by annealing treatment. The crystallinity of ZnO films improves after annealing treatment. The transmittances of the AZO thin films prepared by DC and RF reactive magnetron sputtering are up to 80% and 85% in the visible region, respectively. The electrical resistivity of AZO thin films prepared by DC reactive magnetron sputtering can be as low as tering have better structural and optical properties than that prepared by DC reactive magnetron sputtering.     

Electro magnetic interference shielding characteristic of silver coated copper powder

The present investigation deals with the synthesis of silver coated copper powder for potential application as filler material in conductive polymers for electro magnetic interference (EMI) shielding. Copper powders were obtained by the reaction of cuprous oxide and, hydrazine in a mixed solvent (H₂O:ethanol) at various reaction conditions. The cuprous oxide powder was produced by the reaction of CuSO₄, NaOH and D-glucose. The synthesized copper powder was silver coated by its reaction with (NH₄)₂SO₄, C₄H₄O₆KNa and AgNO₃. The prepared powders were characterized by XRD, SEM, TGA and XPS. The coaxial transmission line method was used to measure the EMI shielding effectiveness of the powders. The silver coated copper powders exhibited an improved oxidation resistance and higher EMI shielding effectiveness as compared to the uncoated copper powders.     

金属纤维电磁屏蔽材料的研究进展

描述电磁辐射的危害及电磁屏蔽材料的屏蔽机制,重点阐述金属纤维制备电磁屏蔽织物、电磁屏蔽聚合物材料及电磁屏蔽建筑与装饰材料的应用及研究进展,并对未来电磁屏蔽材料的发展趋势作预测,指出开发具有高吸收率、低反射率与低透射率的高性能、低消耗兼绿色环保的新型电磁屏蔽材料是未来的研究重点,同时对材料内部组织与结构进行优化,改进成型工艺,提高其电磁屏蔽效能