铁镍磁性涂层碳纤维软磁性能及电磁屏蔽效能的研究

目的制备兼具良好电磁屏蔽效能和软磁性能的新型屏蔽材料。方法采用化学镀的方法在碳纤维表面制备FeNi合金涂层和Ni涂层。运用SEM、EDS、XRD分析涂层碳纤维的形貌、成分和镀层结构。通过VSM研究其软磁性能。采用万用表测量其电阻并计算电导率。利用网络矢量分析仪测量其电磁参数并计算其电磁屏蔽效能,进而对FeNi合金涂层碳纤维和Ni涂层碳纤维的上述性能进行对比。结果金属镀层均匀且晶粒细小。FeNi合金涂层碳纤维的矫顽力为29.25 Oe,饱和磁化强度为25.61 emu/g。在7.92~18 GHz频率范围内,FeNi合金涂层碳纤维的电磁屏蔽效能均在30 dB以上,峰值为40.79 dB。结论金属涂层能使碳纤维具有软磁性能,并能有效地调整其电磁参数,进而显著提高其电磁屏蔽效能。与Ni涂层碳纤维相比,FeNi合金涂层碳纤维的上述性能更加优异。该研究为兼具良好电磁屏蔽效能和软磁性能的新型屏蔽材料的制备提供了新方案。     

Hot-pressed electrospun PAN nano fibers: An idea for flexible carbon mat

Fibers on the nano scale are characterized by its high surface area per unit mass which is associated with high surface free energy. It seems to be an interesting idea to take advantage of this high free surface energy in electrospun in-plane randomly oriented (quasi-isotropic) multi-layered PAN fibrous mat by stabilizing the as electrospun structure at 220 °C under suitable pressure in oxygen environment; such treatment not only activates its high surface energy but also allows the contribution of larger number of molecules on the nano fiber surfaces as well as enhances the bonding between fibers. Mechanical examination of the hot pressed electrospun PAN Nano fibers mat showed higher flexibility than commercial carbon fiber as well as 2-D structure that can be advantageous in applications where the forces are equal in all directions and no specific orientation are required. Stress–strain curves of the hot pressed electro-spun PAN mats showed ductile behavior. The absolute values for tensile strength ranged from 55 to 63 MPa similar to some ductile pure metals such as aluminum, with much larger strain (6.5–8.25%). The modulus value for the fabric was found to be a measure for the enhanced surface free energy (nano size bond) and not the measure for single nano fiber properties, which was proved by preliminary examination for the fracture pattern of the fabric mat. This revealed de-lamination between the mat's layers breaking the bond in between within a value approximately equal or slightly larger than the modulus for bulk PAN polymer (2.80–3.04 GPa) with measured Poisson's ratio of 0.33. Raman analysis for the hot pressed samples showed a formation of disordered carbon structure at 1360 cm^?1 and ordered carbon structure at 1580 cm^?1.     

Electrospun camphorsulfonic acid doped poly(o-toluidine)–polystyrene composite fibers: Chemical vapor sensing

The electrospinning technique was utilized to produce camphorsulfonic acid (HCSA) doped poly(o-toluidine) (POT)–polystyrene (PS) composite fibers in the non-woven mat form. HCSA doped POT–PS composite fibers were fabricated on an interdigited gold (Au) substrate for use as a chemical vapor sensor. The composite fiber sensor responded to volatile chemicals in different ways, depending on the polarity of sensing chemicals. The surface morphology of the non-woven composite fiber mat after chemical vapor sensing was unchanged. This study highlights that composite fibers comprised of polyaniline derivative and a spinnable polymer do have potential for use as chemical sensors due to their good solubility in common solvents and detectable electrical changes at low fiber contents.     

Dielectric properties at microwave frequencies of poly(ɛ-caprolactone)/CNF films and electrospun mats

The electromagnetic (EM) properties of hybrid poly(?-caprolactone)/carbon nanofiber films and electrospun mats at microwave frequencies (8.2–12.4 GHz) were assessed by means of wave guide measurements. It was found that, on equal composition, the two systems present very different permittivities, that in the case of electrospun mats is far lower than that of films. These results are explained in view of the different microstructures. In particular, the massive presence of porosity is demonstrated to be the major parameter affecting the EM properties of mats. Shielding effectiveness was evaluated and was found to be poor for both systems, despite the relative large amount of conductive nanofiller. This results was attributed, in the case of films, to the presence of multiple reflections among CNF, while in the case of mats to their porous microstructure that let the waves easily pass through.     

Morphology of conductive blend fibers of polyaniline and polyamide-11

Polyaniline (PANI), a member of the intrinsically conducting polymer (ICPs) family, was blended with polyamide-11 (poly-ω-aminoundecanoyle) in concentrated sulfuric acid. The above solution was used to spin conductive PANI/polyamide-11 fibers by wet-spinning technology. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were employed to study the two-phase morphology of the conductive PANI/polyamide-11 fibers. The micrographs of the cross-section, the axial section and the surface of the monofilament demonstrated that the two blend components were incompatible. The morphology of PANI in the fibers was of fibrillar form, which was valuable for producing conducting channels. The electrical conductivity of the fibers was from 10⁻⁶ to 10⁻¹ S/cm with the different PANI fraction and the percolation threshold was about 5 wt.%. By comparing the two blend systems of PANI/Polyamide-11 fibers and carbon black filled poly(ethylene terephthalate) (PET) fibers, it was shown that the morphology of the conductive component had an influence on electrical conductivity. The former had higher conductivity and lower percolation threshold than the latter.     

Processing and Performance of MOF (Metal Organic Framework)-Loaded PAN Nanofibrous Membrane for CO<Subscript>2</Subscript> Adsorption

The objective of this experimental study is to produce a nanofibrous membrane functionalized with adsorbent particles called metal organic framework (MOF) in order to adsorb CO₂ from a gas source. Therefore, Polyacrylonitrile (PAN) was chosen as the precursor for nanofibers and HKUST-1, a Cu-based MOF, was chosen as adsorbent. The experimental process consists of electrospinning PAN solution blended with HKUST-1 to produce a nanofibrous mat as working substrates. The fibers were collected in a cylindrical canister model. SEM image of this mat showed nanofibers with the presence of small adsorbent particles, impregnated into the as-spun fibers discretely. To increase the amount of MOF particles for effectual gas adsorption, a secondary solvothermal process of producing MOF particles on the fibers was required. This process consists of multiple growth cycles of HKUST-1 particles by using a sol-gel precursor. SEM images showed uniform distribution of porous MOF particles of 2-4 µm in size on the fiber surface. Energy dispersive spectroscopy report of the fiber confirmed the presence of MOF particles through the identification of characteristic Copper elemental peaks of HKUST-1. To determine the thermal stability of the fibrous membrane, Thermogravimetric analysis of HKUST-1 consisting of PAN fiber was performed where a total weight loss of 40% between 210 and 360 °C was observed, hence proving the high-temperature durability of the synthesized membrane. BET surface area of the fiber membrane was measured as 540.73 m²/g. The fiber membrane was then placed into an experimental test bench containing a mixed gas inflow of CO₂ and N₂. Using non-dispersive infrared CO₂ sensors connected to the inlet and outlet port of the bench, significant reduction of CO₂ in concentration was measured. Comparative IR spectroscopic analysis between the gas-treated and gas untreated fiber samples showed the presence of characteristic peak in the vicinity of 2300 and 2400 cm^?1 which verifies the adsorption of CO₂.     

Shielding performance of metal fiber composites

Metal fibers have been applied to construct composites with desirable electromagnetic interference shiel ding effectiveness and mechanical properties. Copper and stainless steel fibers were prepared with micro-saw fiberpulling combined cutting method. The cross section of the fibers is hook-like, which is beneficial to the improvement of bonding strength. Cement-based composites with copper and stainless steel fibers were fabricated and their electromagnetic shielding effectiveness was measured in the frequency range of 1 - 5 GHz. The results show that the electromagnetic interference shielding effectiveness of those composites is enhanced by the addition of metal fibers,which functions mainly due to the absorption. At some frequencies, 20 dB or more difference is obtained between the materials with and without metal fibers.     

Electromagnetic shielding properties of polypyrrole/polyester composites in the 1–18 GHz frequency range

The dielectric characteristics of conducting polymer-coated textiles in the frequency range 1–18 GHz were investigated using a non-contact, non-destructive free space technique. Polypyrrole coatings were applied by solution polymerization on fabric substrates using a range of concentrations of para-toluene-2-sulfonic acid (pTSA) as dopant and ferric chloride as oxidant. The conducting polymer coatings exhibited dispersive permittivity behaviour with a decrease in real and imaginary components of complex permittivity as frequency increased in the range tested. Both the permittivity and the loss factor were affected by the polymerization time of the conductive coating. It was found that the total shielding efficiency of these conductive fabrics is significant at short polymerization times and increases to values exceeding 80% with longer polymerization times. The reflection contribution to electromagnetic shielding also increases with polymerization time.     

Electrically conductive,processable polymeric materials constructed from metallophthalocyanines

This contribution describes an approach to producing new classes of macromolecular/macromolecular and molecular/macromolecular hybrid materials which can be spun into environmentally stable, flexible, oriented, electrically conductive fibers. Solutions of a phthalocyanine-containing macromolecular (e.g., [Si(Pc)O]_n) or molecular(e.g., Ni(Pc)) ‘metal’ precursor and a host polymer (e.g., Kevlar) are wet-spun to yield, after halogen or electrochemical doping, strong, air-stable fibers with thermally activated electronic conductivities as high as 5 ω^?1 cm^?1. X-ray diffraction and resonance Raman studies of the fibers reveal the presence of preferentially oriented Kevlar and {[Si(Pc)O]I_1.1}_n (or M(Pc)I) crystalline regions, the latter regions with the metallophthalocyanine stacking directions preferentially parallel to the longitudinal fiber axis.     

Physical and electromagnetic shielding properties of green carbon foam prepared from biomaterials

100% green carbon foam from the fibrous fruits of Platanus Orientalis-L (Plane) along with the tar oil as binder has been prepared using a powder molding technique. The objective was to develop a porous monolithic carbon from biomaterials with a considerable strength necessary for various physical, thermal and electromagnetic shielding applications. Fast carbonization was carried out at 1000 °C under the cover of Plane tree pyrolyzed seeds without using any external protective gas. For comparative analysis, some samples were mixed with 5% (mass fraction) iron chloride during the molding process. Iron chloride being a graphitization catalyst and activating agent helped in increasing the specific surface area from 88 to 294 m²/g with a 25% decrease in flexural strength. Thermal stability was improved due to the incorporation of more graphitic phases in the sample resulting in a little higher thermal conductivity from 0.22 to 0.67 W/(m·K). The catalytic carbon foam exhibited shielding effectiveness of more than 20 dB over the X-band frequency. Absorption was dominant with only 8.26%–10.33% reflectance, indicating an absorption dominant shielding mechanism. The new material is quite suitable for high temperature thermal insulation being lightweight, highly porous with interconnected porous morphology most of which is preserved from the original biomaterial.     

电磁波屏蔽织物的发展现状

电磁波屏蔽织物是现代电磁屏蔽材料中不可或缺的一种新型产品.根据生产方法的不同分类,电磁屏蔽织物主要包括金属丝和服用纱线的混编织物、金属纤维混纺织物、共混纺丝织物、真空镀金属织物、金属涂层织物、硫化铜织物、化学镀金属织物.介绍了这些电磁波屏蔽织物的主要特性、制备方法、应用领域以及未来的发展趋势.     

An assessment of graphitized carbon fiber use for electrical power transmission

Significant progress has been made in the last few years toward the production of a highly conductive carbon filament. Graphitized carbon fibers, made from a variety of precursor materials such as rayon, polyacrylonitrile (PAN), pitch, mesophase pitch and benzene, have electrical conductivities in the range $\text{10}{}^6\text{? 10}{}^7\text{(Ω}\text{m}\text{)}{}^{\mathrm{?1}}$, tensile strengths in the range 1–3 GPa, tensile moduli in the range 100–700 GPa and densities in the range 1.8 ?2 2.2 × 10³ kg/m³. These properties suggest that graphitized fibers may have potential as current carriers for electrical power transmission. This paper examines the physical reasons for the electrical and mechanical properties and evaluates prospects for fibers with better electrical conductivity without degradation of mechanical properties. Chemical doping (intercalation) of the highly graphitized carbon fibers is found to be capable of achieving increases in conductivity of 5 to 15 times with some degradation in tensile strength. Various applications for electrical power transmission usage are examined, i.e., underground and overhead conductors, underground pipe, overhead towers and submarine cable. Near-term usage is most probable in towers and submarine cable, where high strength-to-weight advantages may offset the present failure of fiber electrical conductivity to equal aluminum or copper values.     

石墨烯纤维研究进展

石墨烯纤维是2011年才发展起来的一种以天然石墨为最初原料的新型碳质纤维,由石墨烯或者功能化石墨烯纳米片的液晶原液经湿法纺丝一维有序组装而成。石墨烯纤维具有良好的机械性能、电学性能和导热性能,可用于导电织物、散热、储能等领域。将其他物质引入石墨烯纤维中还可得到特定功能的石墨烯复合纤维,如将聚合物加入石墨烯纤维得到结构精巧、力学性能良好的石墨烯仿贝壳纤维;将磁性纳米粒子加入得到磁性的石墨烯复合纤维;加入Ag纳米线得到高导电的石墨烯复合纤维。石墨烯纤维良好的柔韧性使其在柔性器件如柔性超级电容器等领域得到应用。综述了石墨烯纤维的研究现状,对纯石墨烯纤维、石墨烯复合纤维的制备和应用进行了详细的阐述,并对石墨烯纤维的发展方向进行了展望。     

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。     

Fracture detection in concrete by glass fiber cloth reinforced plastics

Two types of carbon (carbon fiber and carbon powder) and a glass cloth were used as conductive phases and a reinforcing fiber, respectively, in polymer rods. The carbon powder was used for fabricating electrically conductive carbon powder-glass fiber reinforced plastic (CP-GFRP) rods. The carbon fiber tows and the CP-GFRP rods were adhered to mortar specimens using epoxy resin and glass fiber cloth. On bending, the electrical resistance of the carbon fiber tow attached to the mortar specimen increased greatly after crack generation, and that of the CP-GFRP rod increased after the early stages of deflection in the mortar. Therefore, the CP-GFRP rod is superior to the carbon fiber tow in detecting fractures. Also, by reinforcing with a glass fiber cloth reinforced plastic, the strength of the mortar specimens became more than twice as strong as that of the unreinforced mortar.     

碳纳米管对金属网栅电磁屏蔽效能及可视性的影响

目的提高金属网栅的屏蔽效能及可视性能。方法采用纳米复合电镀工艺,将碳纳米管附着在金属网栅表面,并对网栅的微观结构、屏蔽效能、透光率进行测试分析。结果施镀后,金属网栅表面的碳纳米管分布均匀,在10 kHz~1 GHz频段的电磁屏蔽效能提高了3~5 dB,可见光透光率降低了5%,金属光泽有所消除。结论碳纳米管可有效提高金属网栅的屏蔽效能和可视性能。     

Fabrication of niobium doped Pb（Zr, Ti）O3 fibers by viscous polymer processing

A technique based on viscous polymer processing （VPP） was described, which can produce high ceramic content green fibers. PZT-5 ceramic powders were ball milled to get high dispersibility. The slurry prepared for VPP was a composition of PZT-5 powder, PVA binder and glycerin. High ceramic content PZT-5 fibers were extruded with the slurry. The results show that the ceramic powders have fine mean particle size of 0.54 pan, high specific surface area of 3.55 m^2/g and zeta potential of 8.81 mV after 16 h milling. The fibers sintered at 1 280 ℃ for 4 h have pure perovskite structure and grains of 2-5 μm in size, with little pores or cracks. The ultimate tensile strength of sintered fibers is up to 13.84 MPa compared with 2.88 MPa of green fibers. The remnant polarization （Pr） and coercive field （Ec） of the fibers are 50.65 μC/cm^2 and 2.45 kV/mm, respectively. This fiber can withstand an electric field of 9 kV/mm higher than the ceramic （5 kV/mm）, which shows high directional and compact qualities.     

碳纤维增强水泥基复合材料电磁性能的研究

制备了碳纤维增强水泥基复合材料，在SEM扫描电镜下观察了样品的断121形貌。利用NRL测试系统测试了低频段4-8GHz和高频段8-18GHz条件下、碳纤维质量分数分别为0．2％，0．4％，0．6％，0．8％，1．0％时，复合材料对电磁波的反射率，评价了电磁干扰性能。结果表明，低频段时所测得的反射率均小于-10dB，材料对电磁波主要表现出吸收性：高频段且碳纤维质量分数超过0．6％时，反射率大于-10dB，材料对电磁波主要表现出反射性。反射率随着碳纤维质量分数的增加而变化，低频段且碳纤维质量分数为0．6％时，出现最小反射率，其大小为-15．1dB：高频段且碳纤维质量分数为0．4％时，出现最小反射率，其大小为-19．3dB。     

Polypyrrole-coated fibers as microwave and millimeterwave obscurants

Microwave and millimeterwave obscurants based on typical millimeterwave materials do not environmentally degrade with respect to their physical and electrical properties. The use of conductive polymer-coated films and fibers with inherent environmental instabilities are being investigated as possible alternatives. Achieving the optimum electrical performance is highly dependent upon the polymer/dopant combination, deposition conditions, morphology and volume of the coating that is used. The electrical performance can be assessed by complex permittivity analysis and this was performed on samples of compacted conductive polymer powders. Several conductive polymer-coated fiber systems were also investigated via thermal analysis. The effects of processing conditions on performance and stability were studied.     

Synthesis of carbon nanomaterials with porous alumina as a template

Single-and double-walled carbon nanotubes were obtained by template synthesis with foamed monolithic alumina as a template. The carbon materials obtained are homogeneous; their structures depend on the carbon precursor used. Double-walled nanotubes (with saccharose as a carbon precursor) have an average diameter of about 0.4 nm and a specific surface area of about 400 m²/g (from the BET isotherm). Single-walled carbon nanotubes (with a polymer based on furfuryl alcohol as a carbon precursor) have a diameter of 1.8 nm and a specific surface area of 580 m²/g. Original Russian Text ? O.K. Krasil’nikova, A.S. Pogosyan, N.V. Serebryakova, T.Yu. Grankina, A.N. Khodan, 2008, published in Fizikokhimiya Poverkhnosti i Zashchita Materialov, 2008, Vol. 44, No. 4, pp. 389–394.