海胆状氧化锌/羰基铁粉核壳结构复合粒子的抗氧化及吸波性能

针对羰基铁粉吸收剂在温度较高时易被氧化的问题,采用水热法制备了氧化锌包覆羰基铁粉核壳结构复合粒子,并分别将羰基铁粉和氧化锌/羰基铁粉核壳粒子与石蜡混合,制备复合材料。结果表明,氧化锌纳米棒致密的包覆在羰基铁粉颗粒表面形成海胆状核壳结构复合粒子,正是这种结构将羰基铁粉颗粒与空气隔绝,使得复合粒子的抗氧化性能得到显著改善。与羰基铁粉复合吸波材料相比,氧化锌/羰基铁粉核壳粒子的复合材料吸收峰稍向低频移动,反射损耗小于-5 d B的带宽几乎保持不变,在不改变电磁吸波性能的前提下,提高了羰基铁粉粒子的使用温度。     

海胆状氧化锌/羰基铁粉核壳结构复合粒子的抗氧化及吸波性能

针对羰基铁粉吸收剂在温度较高时易被氧化的问题,采用水热法制备了氧化锌包覆羰基铁粉核壳结构复合粒子,并分别将羰基铁粉和氧化锌/羰基铁粉核壳粒子与石蜡混合,制备复合材料。结果表明,氧化锌纳米棒致密的包覆在羰基铁粉颗粒表面形成海胆状核壳结构复合粒子,正是这种结构将羰基铁粉颗粒与空气隔绝,使得复合粒子的抗氧化性能得到显著改善。与羰基铁粉复合吸波材料相比,氧化锌/羰基铁粉核壳粒子的复合材料吸收峰稍向低频移动,反射损耗小于-5dB的带宽几乎保持不变,在不改变电磁吸波性能的前提下,提高了羰基铁粉粒子的使用温度。     

一种提高有机硅导电橡胶复合材料导电和电磁屏蔽性能的方法

描述了一种利用多元复合导电网络提高有机硅橡胶复合材料导电和电磁屏蔽性能的思想。这种含有多元复合导电网络的复合材料是通过将镀银泡沫、导电填料和有机硅橡胶复合在一起而制备的。利用扫描电子显微镜观察了复合材料的微观结构,采用电阻测试仪、矢量网络分析仪、热失重分析仪分别研究了复合材料的导电性、电磁屏蔽性能及热稳定性,并探讨了补强剂SiO2对这些性能的影响。结果表明,2%碳纳米管/导电泡沫/硅橡胶多元复合体系相比于2%碳纳米管/硅橡胶单一复合体系电阻率降低了6个数量级,平均电磁屏蔽效能由12dB提高到52dB,增大了4倍。当导电填料换为炭黑后,2%炭黑/导电泡沫/硅橡胶多元复合体系相比于2%炭黑/硅橡胶单一复合体系电阻率降低了7个数量级,平均电磁屏蔽效能由10dB提高到50dB,增大了5倍。由于多元复合导电网络,材料的导电性能和电磁屏蔽性能大幅度提升。此外,补强剂的加入增大了复合材料的热稳定性,但降低了其导电和电磁屏蔽性能。     

电磁屏蔽材料的研究进展

介绍了电磁屏蔽材料在军用和民用领域的重要性;简要阐述了电磁屏蔽的机理;综述了4种不同电磁屏蔽材料的优缺点以及研究现状,分别为金属型、表面导电型、填充复合型和本征型导电聚合物电磁屏蔽材料;分析并提出了3种提高电磁屏蔽效能的方式,分别为多孔结构设计、多层结构设计、复合填料优化。     

聚乙二醇包裹羰基铁核壳粒子的制备及水基磁流变液的性能

以羰基铁粉(CI)为原料用共溶胶-凝胶反应制备CI/聚乙二醇核壳复合粒子，并将其与水组成了磁流变液. 用SEM、TEM、FT-IR和VSM表征了核壳复合粒子的微观结构和静磁特性，并测试了水基磁流变液的性能. 结果表明，核壳复合粒子表面有SiO_x和聚乙二醇的包覆层，它有较好的亲水性和优良的软磁特性，用它组成的水基磁流变液具有抗沉降性优良、零场粘度低、磁流变效应显著等特点.     

片状镍粉填充树脂基和石蜡基复合材料的微波电磁特性

以微米镍粉作为原料,采用湿法研磨法制备了片状镍粉,将其作为填料用于制备树脂基导电复合材料和石蜡基复合材料;测定了树脂基复合材料的电磁屏蔽性能与镍粉含量的关系,同时考察了片状镍粉/石蜡复合材料的吸波性能.结果表明,复合材料电磁屏蔽性能(SE)随着填料含量的增加而提高;厚度为5 mm的片状镍粉/石蜡复合材料在2 GHz附近的最小反射率可达-27 dB.这表明所制备的片状镍粉在电磁屏蔽及吸波领域具有很好的应用前景.     

碳系填料填充聚合物基电磁屏蔽材料研究进展北大核心CSCD

电子电器设备的大量应用,使得电磁环境越来越复杂,对电磁屏蔽材料的需求也不断增长。与传统的金属填料相比,碳系填料具有品种多、质量轻、电导率高、来源广、耐腐蚀等独特优势,在聚合物基电磁屏蔽领域有着广阔的应用前景。本文主要介绍了炭黑、石墨、石墨烯、碳纳米管、碳纤维等碳系填料的结构与性能特点,并从填料形状,表面处理,复合技术等角度综述了近年来碳系填料填充改性制备聚合物基电磁屏蔽材料方面的研究进展。     

双功能聚二甲基硅氧烷/铜纳米线复合薄膜的制备与性能

通过环境友好的葡萄糖模板法和改进的湿化学还原法制备了聚二甲基硅氧烷/铜纳米线(PDMS/CuNWs)复合薄膜, 其采用的“类夹心结构”有效解决了铜在空气中易氧化进而导致电导率大幅度下降的问题, 同时获得了具有优异电磁屏蔽和光热转化性能的双功能轻质柔性复合薄膜. CuNWs面密度为1.6 g/cm²的复合薄膜在重复弯折1000次后性能保持率最高可达99.07％; CuNWs面密度为2.4 g/cm²的复合薄膜在X波段下总电磁屏蔽效能达到30.1 dB, 屏蔽效率达到99.9％; 同时, 在2 W/cm²的近红外光照射下, 复合薄膜在仅加热15 s后其表面温度高达211.2 ℃, 具有十分快速的光热响应和转化效率.     

Conductivity and electromagnetic shielding effectiveness of flaky Ni/Ni-Cu-coated glass fiber/epoxy resin composite coating

Flaky Ni/Ni-Cu-coated glass fiber/epoxy resin composite coatings were prepared using the glass fibers and flaky nickel powders as fillers and epoxy resin as binder. The conductivity and electromagnetic shielding effectiveness of the coatings are as follows: (1) the appropriate content of Ni-Cu-coated glass fibers is 6 wt % in the composite filler and the optimum ratio of the filler to epoxy resin is 4: 1; (2) electrical conductivity of the coating with a thickness of 300 μm has a minimum value of 0.72 Ω cm; (3) shielding effectiveness of the coatings is up to 50.21–55.43 dB in the frequency range of 0.3–1000 MHz. This offers a new idea to enhance the added value of the glass fibers and raise the level of electromagnetic radiation protection.     

Silver Hollow Microspheres: Large-scale Synthesis, Characterization and Electromagnetic Shielding Property

A facile and large-scale synthesis method to fabricate silver hollow microspheres with controllable morphologies and shell thickness is described using low-cost glass microspheres as templates. The method mainly involves two steps of the preparation of silver-coated glass microsphere core-shell particles by a controllable liquid reduced reaction of Ag[(NH3)2]+ solution, which only produces silver nanoparticles anchored on the surface of the thiolated glass microsphere templates, and the removal of glass microspheres by wet chemical etching with HF solution. The products are well characterized by field emitted scanning electron microscopy (SEM), transmitted electron microscopy (TEM), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) etc. The as-prepared core-shell particles and hollow particles have even and compact silver shells. The electromagnetic shielding coatings based on the silver hollow microspheres are demonstrated to have high conductivity, excellent shielding effectiveness and long durability, suggesting that the silver hollow microspheres obtained here are a novel light-weight electromagnetic shielding filler and will have extensive applications in the electromagnetic compatibility fields.     

Preparation and characterization of silver/TiO2 composite hollow spheres

Silver-coated poly(methyl acrylic acid) (PSA) core-shell colloid particles were prepared by an in situ chemical reduction method. Crystalline silver/titania composite hollow spheres were obtained by coating the as-prepared PSA/silver particles with an amorphous titania layer and subsequently calcining in Ar atmosphere. SEM and TEM investigation indicated that the size of the as-prepared PSA/silver and PSA/silver/TiO(2) core-shell particles and silver/titania composite hollow particles was fairly uniform and the wall thickness of the hollow spheres was in the range of 40-80 nm. UV-vis absorption spectra were recorded to investigate their optical properties.     

酞菁钴/纳米铁复合颗粒的结构与微波电磁特性

一些铁磁性金属及其合金超细粉末,具有比饱和磁化强度高、易于合成与粒径可控等优点,因此被广泛应用于磁流体、电磁流变液、微波吸收材料等领域,但由抗氧化性差、密度较大等主要缺点而使其应用受到限制,采用有机／无机复合技术可制备具有有机包覆层的有机／无机复合颗粒,不仅可以增强铁磁性颗粒的抗氧化性,减小了密度,而且可以提高与有机基体的亲和性,为该类材料向更高层次发展提供了可能。     

碳纤维表面羰基铁的原位生长及吸波性能

以Fe(CO)5为前驱体,通过金属有机化学气相沉积(MOCVD),在碳纤维(CF)表面构筑厚度为纳米级的羰基铁(CI)壳层,通过改变沉积温度,调控核壳粉体的形貌结构和吸波性能。用X射线衍射仪、扫描电子显微镜和矢量网络分析仪对粉末的结构及电磁性能进行表征并对其吸波性能进行研究。结果表明:随着沉积温度升高(210~240℃),沉积到CF表面的羰基铁颗粒互相“吞并-融合”,此时CF-CI形成了完整的薄膜包覆型核壳结构;沉积温度太高时(270℃)会造成CF表面羰基铁壳层形貌的恶化。通过调节沉积温度,在纳米尺度上可以有效调控CI壳层的形貌,从而调节CF-CI核壳粒子的电磁性能。以核壳形貌及吸波性能为考察指标,最终确定最佳的沉积温度为240℃。以沉积温度为240℃时所获样品的电磁参数,模拟计算出涂层厚度为0.9 mm时,小于-10 dB的吸波带宽最大为4.6 GHz(13.4~18 GHz);涂层厚度为2.0 mm时,反射率达到最小值为-21.5 dB;厚度为0.9~3.9 mm时,在2~18 GHz均能实现吸波强度低于-10 dB。     

Synthesis and characterization of silica-silver core-shell composite particles with uniform thin silver layers

Silica-silver core-shell composite particles with uniform thin silver layers were successfully synthesized by a facile and one-step ultrasonic electrodeposition method. By electrolysis of the slurry consisting of preformed silica spheres and silver perchlorate without any additives, the homogenous composite particles can be prepared. The average size of single silver crystals in the composite is about 12 nm and the thickness of silver layer is 14±2 nm. Moreover, the continuity of Ag distribution, the surface roughness and the thickness of silver layer are controllable by adjusting the current density (I), the concentration of electrolyte (C) and the reaction time (t). Optical properties of the composite particles with different silver content were also investigated.     

PDA/PVDF紫外线屏蔽复合膜的制备及性能表征

利用多巴胺在溶液中自聚得到聚多巴胺(PDA)颗粒, 然后将其作为填料加入聚偏氟乙烯(PVDF)中, 采用溶液成膜法制备具有紫外线屏蔽功能的PDA/PVDF复合膜. 通过傅里叶变换红外光谱(FTIR)、 扫描电子显微镜(SEM)和紫外可见分光光度计(UV-Vis)对制备的PDA颗粒的结构、 形貌以及吸光度进行表征, 并且进一步利用X 射线衍射仪(XRD)、 差示扫描量热仪(DSC)、 热失重分析仪(TGA)、 接触角测量仪(CA)以及紫外老化箱等对PDA/PVDF复合膜的结构、 热性能、 润湿性能与紫外线屏蔽性能进行测试. 结果表明, 制备的PDA颗粒的粒径约为160 nm; 掺杂PDA之后的PVDF膜的结晶度以及接触角均减小; 并且PDA质量分数为5%时得到的PDA/PVDF复合膜在200400 nm范围内的透过率均低于1%, 能够吸收所有的紫外线, 表现出优异的紫外线屏蔽功能.