涂层层数对镍粉_石墨基复合材料介电性能和吸波性能的影响.pdf

第 32 卷 第 3 期2024 年 3 月现代纺织技术Advanced Textile TechnologyVol.32,No.3Mar.2024DOI:10.19398j.att.202303049涂层层数对镍粉石墨基复合材料介电性能和吸波性能的影响师 琅a,姜茸凡b(西安工程大学,a.学报编辑部;b.服装与艺术设计学院,西安 710048)摘 要:为了解制备工艺对涂覆型吸波材料性能的影响,实验研究涂层层数对镍粉石墨基复合材料的介电性能及吸波性能的影响机制。选用 PU2540 型聚氨酯为黏结剂,镍粉、石墨为功能粒子,涤棉平纹织物为基布,采用纺织涂层(刮涂法)工艺制备了涂层层数不同的镍粉石墨基涂层复合材料。测试该复合材料的介电常数(实部、虚部、损耗角正切值)和反射损耗,分析涂层层数对复合材料介电性能和吸波性能的影响。结果表明:在测试频率 11000 MHz 范围内,3 层的镍粉石墨基复合材料对电磁波的极化能力、损耗能力及耦合能力最强;在测试频率 103000 MHz 范围内,涂层层数 2 层的复合材料的吸波性能最好,反射损耗最小峰值为-26.460 dB;3 种涂层层数不同的复合材料在不同频段表现出不同的吸波特性。所得结果可为开发经济实用的吸波材料提供理论参考。关键词:镍粉;石墨;涂层;复合材料;介电性能;吸波性能中图分类号:TS101.3 文献标志码:A 文章编号:1009-265X(2024)03-0038-07收稿日期:20230329 网络出版日期:20231027基金项目:陕西省教育厅专项科研计划项目(22JK0405)作者简介:师琅(1988),女,陕西西安人,硕士,主要从事纺织复合材料的研究。通信作者:姜茸凡,jiangrongfan 随着现代通信技术的快速发展,电子设备在航天航空、无线通讯、雷达探测等领域的广泛应用使得电磁波干扰、辐射污染等成为备受关注的社会问题1-3。电磁污染不仅威胁信息安全,且高能电磁波对人体健康会有一定影响。电磁波的危害程度与其频率相关。当电磁波达到一定强度时,其电离作用会直接杀死细胞,使蛋白质变性,从而影响人体免疫系统,引发人体病变4-6。吸波材料可有效解决电磁波干扰及辐射污染等问题,因此有关吸波材料的研发受到学界的广泛关注。石墨是一种高密度碳原子构成的层状六方结构碳材料,碳原子间通过范德华力形成一个连续的电子轨道。石墨具有良好的导电性、导热性、耐腐蚀性,广泛应用于石墨电极、电磁防护材料、超导材料等7-9。石墨不仅具有优良的介电性能,而且易促进镍粉在基体中均匀分布。镍粉是具有良好铁磁性的超细金属粉末,依靠磁滞损耗、畴壁共振、自然共振、后效共振等磁化机制衰减、吸收电磁波,吸收和散射射线的电子矢量能力强,磁矢量的衰减幅度大,在电磁防护材料领域得到广泛应用。而且,镍粉的导电性能与导热性能好,吸收与散射能力强,耐高温耐腐蚀性强10-11。另外,在应用于涂层织物的黏合剂涂料中,聚氨酯是最通用的涂料品种之一,类型和品种繁多,应用范围广泛。PU2540 型聚氨酯涂层黏合剂是由多异氰酸酯(含NCO 基团)和大分子多元醇(含OH 基团)聚合而成的树脂。在聚氨酯大分子中存在大量的氢键,分子间作用力大,大分子链对大部分化学物质是稳定的,因此聚氨酯具有环保无毒、黏接牢度好、价格低廉等优点。PU2540 型聚氨酯可作为涂层材料的基体,用其制备的涂层织物具有韧性好、耐曲折、耐磨、耐寒、耐水洗、柔软不回黏、丰满度高、光泽好、伸展性优异等显著优点,能够更好地满足辐射防护材料各方面的要求。本文以涤棉平纹织物为基布、PU2540 型聚氨酯为黏结剂、镍粉和石墨为功能粒子,采用纺织涂层(刮涂法)工艺制备镍粉石墨基复合材料,并测试分析其电磁性能,从而为后续开发经济实用的吸波材料提供理论基础。1 实 验1.1 材料和试剂涤棉平纹织物(宝鸡常源工贸有限公司);石墨粉末(QHG3991-88,天津市登科化学试剂有限公司,10100 m);镍粉(W-5,深圳昌鑫达屏蔽材料有限公司,10100 m);聚氨酯(PU2540,广州誉衡环保材料有限公司);增稠剂(7011,广州典木复合材料经营部)。1.2 涂层复合材料的制备1.2.1 镍粉石墨涂层浆料制备将镍粉与石墨按质量比 1 4 混合得到镍粉石墨功能粒子,以 PU2540 型聚氨酯为黏结剂,并加入适量增稠剂,制成涂层浆料。涂层浆料中功能粒子质量分数为 40%,涂层浆料黏度为 30000 mPa s。1.2.2 镍粉石墨基复合材料制备涤棉平纹织物固定于涂层机上,将镍粉石墨涂覆材料通过涂层机均匀涂覆在基布表面,涂层速度为 60 cmmin。涂覆后材料置于 80 烘箱内烘10 min,得到单层的镍粉石墨基涂层复合材料。多层涂层材料制备需待单次涂层完全晾干后重复上述过程,进行 2 次、3 次涂层。为分析涂层层数对复合材料介电性能和吸波性能的影响,分别制备了 3 种涂层层数不同的复合材料,具体工艺参数见表 1。复合材料结构模型如图 1 所示,最底层黄色部分为基布,上层蓝色部分为不同层数涂层。实验采用高精度自动涂层设备进行,实验中设备自动控制涂层厚度,转速平稳,涂层厚度均匀。表 1 涂层工艺参数Tab.1 Coating process parameters试样编号单层涂层厚度mm涂层总层数层涂层总厚度mm1#1112#1223#133 注:厚度指烘干前湿膜厚度。图 1 涂层复合材料结构示意图Fig.1 Structure model of coated composite materials1.3 性能测试1.3.1 介电性能测试介电性能是指在电场作用下,材料表现出对静电能的存储和损耗的性质。介电常数实部越大,材料对电磁波的极化能力越强;介电常数虚部越大,材料对电磁波的损耗能力越强;损耗角正切值越大,材料对电磁波的耦合能力越强12-13。采用BDS50 型介电阻抗谱仪(德国 Novocontrol 公司)进行测试,试样尺寸为 2 cm 2 cm,将试样放入测试夹具中,连接在测试系统的上下电极之间。根据 SJ 205121995微波大损耗固体材料复介电常数和复磁导率测试方法测试材料的介电性能。每种试样测试 10 次,取平均值。1.3.2 反射损耗测试反射损耗(RL)用于评估微波吸收材料的吸波性能14-15。采用 ZNB40 型矢量网络分析仪(德国罗德与施瓦茨公司)对样品的反射损耗进行测试。将测试夹具用测试线与主机相连,设定测试频段为103000 MHz,试样为外径 7.60 cm、内径 3.35 cm的圆环形。将试样放入同轴夹具中,将标准金属板盖于同轴夹具上,测试样品的反射损耗。每种试样测试 10 次,取平均值。2 结果与讨论2.1 涂层层数对复合材料介电常数的影响介电性能是电介质材料的重要物理性能之一,93第 3 期师 琅 等:涂层层数对镍粉石墨基复合材料介电性能和吸波性能的影响用介电常数及介电损耗来表征。测试了不同涂层层数的复合材料的介电常数和介电损耗,分析涂层层数对复合材料介电常数实部、介电常数虚部 以及介电常数损耗角正切值 tan 的影响。图 2 为不同涂层层数的复合材料的介电常数实部变化曲线。从图 2 可看出,在频率 301000 MHz范围内,涂层层数为 1 层、2 层、3 层的复合材料的介电常数实部均减小,对电磁波的极化能力减小,其中:涂层层数为 3 层的复合材料的介电常数实部最大,其次为涂层层数 2 层、1 层的复合材料。在外加电场频率为 30 MHz 时,各样品的介电常数实部均最大,其中涂层层数为 3 层的复合材料对电磁波的极化能力最强,对电荷的存储能力最强。这可能是因为实部储存电荷的能力与涂层复合材料的导电性成正比。复合涂料的导电性与其导电填料的体积分数、导电粒子尺寸、粒子形状、粒子分散均匀程度有关,这些因素均会影响导电粒子间相互接触的程度。单层涂层厚度不变的情况下,涂层层数增加,涂层总厚度增加,单位横截面内的石墨和镍粉粒子的含量也增加,材料的导电性能增强。此外,石墨在材料中呈导电网络骨架结构,加入镍粉后,石墨粒子间的空隙得到充分填充,复合材料的导电性能进一步提升16。图 2 不同涂层层数的复合材料的介电常数实部变化曲线Fig.2 Real part change curves of dielectric constant of composites with different coating layers图 3 为不同涂层层数的复合材料的介电常数虚部变化曲线。从图 3 可看出,在频率 1 1000 MHz范围内,涂层层数为 1 层、2 层、3 层的介电常数虚部均有增加,对电磁波的损耗能力增强,其中:3 层的复合材料的介电常数虚部最大,其次为 2 层、1 层的复合材料。在外加电场频率为 1000 MHz 时,各样品的介电常数虚部均最大,其中涂层层数为 3 层的复合材料对电磁波的损耗能力最强。随着涂层层度的增加,样品的介电常数虚部增加。这可能是因为介电常数虚部取决于发生重排的电偶极矩,发生重排的电偶极矩与复合材料的导电性成正比。单层涂层厚度不变的情况下,涂层层数增加时,涂层总厚度增加,单位横截面内的石墨和镍粉粒子的含量也增加,材料的导电性能增强,材料内部粒子极化时发生的位移增大。电偶极矩越大,对电磁波的损耗越大。图 3 不同涂层层数的复合材料的介电常数虚部变化曲线Fig.3 Imaginary part change curves of dielectric constant of composites with different coating layers图 4 为不同涂层层数的复合材料的介电常数损耗角正切值变化曲线。从图 4 可看出,在频率 1 1000 MHz 范围内,涂层层数为 1 层、2 层、3 层的复合材料的介电常数损耗角正切值均有增加,对电磁波的衰减能力增强。其中涂层层数为 3 层的复合材料的介电常数损耗角正切值最大,对电磁波的衰减能力最强。在频率 1200 MHz 范围内,涂层层数为3 层的复合材料的介电常数损耗角正切值最大,其次为涂层层数 2 层、1 层的复合材料。吸波材料需要有合适的电导率才能使其具备一定的电磁波衰减能力。而随着涂层厚度的增加,涂料中的导电粒子增多,材料对电磁波的传输和损耗能力增强。此外,石墨的导电网络骨架结构以及镍粉的加入,使得复合材料吸收、衰减电磁波的性能进一步提升16。单层涂层厚度不变,改变涂层层数,涂层总厚度变化,涂层总厚度决定单位横截面积中的镍粉石墨功能粒子含量。2.2 涂层层数对复合材料反射损耗的影响测试不同涂层层数的复合材料对电磁波的反射损耗,结果如图 5 所示。材料的反射损耗值越小,说明其对电磁波的反射越少,对电磁波的损耗越大。04现代纺织技术第 32 卷图 4 不同涂层层数的复合材料的介电常数损耗角正切值变化曲线Fig.4 Loss tangent change curves of dielectric constant of composites with different coating layers图 5 不同涂层层数的复合材料的反射损耗变化曲线Fig.5 Reflection loss change curves of composites with different coating layers从图 5 可看出,在频率 140740 MHz 范围内,涂层层数为 1 层、2 层、3 层的复合材料的反射损耗值均大于-2 dB,这表明其几乎没有吸波能力。在频率7401304 MHz,涂层层数为3 层的复合材料的反射损耗值最小为-15.793 dB,其次是涂层层数为2 层、1 层的复合材料。在频率 13041597 MHz 范围内,涂 层 层 数 为 2 层 的 反 射 损 耗 值 最 小 为-26.460 dB,其次是涂层层数 3 层、1 层的复合材料。在频率 15971920 MHz 范围内,涂层层数为 2层的复合材料的反射损耗值最小,其次是涂层层数为 1 层、3 层的复合材料。在频率 19203000 MHz 范围内,涂层层数为 1 层的复合材料的反射损耗值最小,为-12.406 dB,其次是涂层层数为 2 层、3 层的复合材料。在频率 1403000 MHz 范围内,所有样品的反射损耗值均先减小后增大,吸收电磁波的能力均先增大后减小。由于镍粉属于磁损耗型吸波材料,具有较佳的微波磁导率,通过涡流效应、磁滞损耗和交换共振等磁损耗方式对电磁波能量进行吸收和衰减,使材料具有较佳的吸波性能。石墨属碳基材料,不仅具有很好的介电性能,且易促进铁磁性材料在基体中均匀分布。此外石墨粒子之间通过桥接作用形成导电网络骨架,增加了镍粉粒子相互接触的概率和构成电子隧道结的概率。石墨属电阻损耗型吸波材料,在电磁波作用下材料内部会产生感应电流,感应电流转化为热能从而被损耗17。石墨与镍粉混合使得材料同时具有磁损耗和介电损耗。石墨通过与电场的相互作用,依靠介质的电子极化或界面极化衰减来吸收电磁波,主要表现为具有较高的介电损耗角正切值。涂层层数增加,石墨粒子含量增大,材料的体积电阻率减小,吸波效果增强,但是材料表面电阻率的降低使得材料的反射能力增大,以至自由空间的电磁波难以进入材料内部,不能达到吸波的目的。因此,吸波材料的设计要考虑到阻抗匹配,保证电导率在适当范围内,使材料具有理想的吸波性能18。在单层涂层厚度相同的情况下,涂层层数决定了石墨和镍粉的含量存在一个最佳范围,使材料的吸波性能最好。在频率 103000 MHz范围内,涂层层数为 2 层的涂层复合材料出现了反射损耗最小峰值,为-26.460 dB。本文实验中涂层层数为 2 层的涂层复合材料的吸波性能最好。3 结 论本文以纺织涂层工艺制备了镍粉石墨基涂层复合材料,通过测试复合材料的介电性能及吸波性能,分析涂层层数对镍粉石墨基涂层复合材料介电常数及反射损耗的影响,结论如下:a)在频率 301000 MHz 范围内,涂层层数不同的复合材料的介电常数实部均减小;当频率为30 MHz 时,涂层层数为 3 层的复合材料的介电常数实部最大,其对电磁波的极化能力最强。在频率11000 MHz 范围内,涂层层数不同的复合材料的介电常数虚部、介电常数损耗角正切值均有增加;当频率1000 MHz 时,涂层层数为3 层的复合材料的介电常数虚部及介电常数损耗角正切值最大,其对电磁波的损耗能力最强。b)在频率 103000 MHz 范围内,3 种涂层层数不同的复合材料在不同频段表现出不同的吸波特性。涂层层数为 2 层的涂层复合材料达到反射损耗最小峰值(-26.460 dB),其对电磁波的吸波能力最强。参考文献:1 LIU Y J,LIU Y C,ZHAO X M.The research of EM wave 14第 3 期师 琅 等:涂层层数对镍粉石墨基复合材料介电性能和吸波性能的影响absorbing properties of ferritesilicon carbide double coated polyester woven fabric J.The Journal of the Textile Institute,2018,109(1):106-112.2 计瑜,刘元军,赵晓明,等.电磁屏蔽织物的研究现状J.现代纺织技术,2022,30(3):1-12.JI Yu,LIU Yuanjun,ZHAO Xiaoming,et al.Research status of electromagnetic shielding fabricsJ.Advanced Textile Technology,2022,30(3):1-12.3 KENANAKIS G,VASILOPOULOS K C,VISKADOURAKIS Z,et al.Electromagnetic shielding effectiveness and mechanical properties of graphite-based polymeric filmsJ.Applied 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compositeJ.Plastics,2015,44(2):22-25.17 王丽熙,张晶,黄啸谷,等.铁氧体石墨复合吸波涂层的微波吸收性能J.材料科学与工程学报,2011,29(5):688-691.WANG Lixi,ZHANG Jing,HUANG Xiaogu,et al.Microwave absorbing properties of ferritegraphite composite coatingsJ.Journal of Materials Science and Engineering,2011,29(5):688-691.18 高敬伟.多形态聚吡咯的制备与吸波性能研究D.上海:东华大学,2010.GAO Jingwei.Preparation ofMulti-morphology Polypyrrole and the Research on Their Microwave Absorbing PropertiesD.Shanghai:Donghua University,2010.Effect of coating layer number on dielectric properties and wave absorption properties of Ni powdergraphite matrix compositesSHI Langa,JIANG Rongfanb(a.Editorial Department;b.Apparel&Art Design College,Xi an Polytechnic University,Xi an 710048,China)Abstract:Graphite has good electrical conductivity thermal conductivity and corrosion resistance and is widely used in graphite electrodes electromagnetic protection materials superconducting materials and so on.To improve the wave absorbing properties of graphite-matrix composites and analyze the effect of the coating layer number on the dielectric properties and wave absorbing properties of composites the nickel powdergraphite matrix composites were prepared and researched.The nickel powdergraphite functional particles were prepared by mixing nickel powder and graphite according to the mass ratio of 1 4.By using PU2540 polyurethane as the substrate and adding appropriate thickener the nickel powdergraphite coating sizing was prepared.The mass fraction of functional particles in the coating sizing is 40%of the total mass and the viscosity of the coating sizing is 30 000 mPa s.With the common polyestercotton plain fabric in the market as the coating material base cloth by adopting the textile coating process scraping coating method and using the automatic coating machine coating machine speed of 60 cmmin the nickel powdergraphite base coating sizing was evenly coated on the base cloth and dried in the oven at 80 for 10 min.Nickel powdergraphite based coating composites with 1 2 and 3 layers were prepared respectively.The dielectric constant of the composite was measured by BDS50 dielectric impedance spectrometer and the reflection loss was measured by ZNB40 vector network analyzer.The effects of the layer number on dielectric properties and wave absorption properties of the composite were analyzed.The results show that the layer number has a certain influence on the electromagnetic shielding properties of Ni powdergraphite coating composites.In the applied electric field frequency range of 301 000 MHz the real part of the dielectric constant of the composites with different coating layers decreases.When the frequency is 30 MHz the real part of the dielectric constant of the samples is the largest and the composites with three coating layers is the largest indicating that it has the strongest ability to polarize electromagnetic waves and store charges.This is because the ability of the real part to store charge is directly proportional to the conductivity of the coated composite.The electrical conductivity of the composite is related to the volume fraction of the conductive filler the size of the conductive particle the shape of the particle and the dispersion uniformity of the particle which will affect the degree of contact between the conductive particles.In the applied electric field frequency range 11 000 MHz the imaginary part and loss angle tangent value of the dielectric constant of the composite with different layer number increase.When the frequency is 1 000 MHz the imaginary part of the dielectric constant of the samples is 34第 3 期师 琅 等:涂层层数对镍粉石墨基复合材料介电性能和吸波性能的影响the largest and the imaginary part and loss angle tangent value of the dielectric constant of the composite with three layers are the largest indicating that it has the strongest loss ability to electromagnetic wave.This is because the imaginary part of the dielectric constant depends on the electric dipole moment of the rearrangement which is proportional to the conductivity of the composite sizing.In addition in the conductive network skeleton formed by graphite due to the addition of nickel powder the space between the graphite particles is fully filled and the conductive property of the composite material is further improved.In the applied electric field frequency range of 10-3 000 MHz the 2-coating-layer composite achieves the lowest peak value of reflection loss up to-26.460 dB indicating that it has the strongest absorption ability of electromagnetic wave.This is because graphite absorbs electromagnetic waves through the interaction with the electric field and its main feature is that it has a high dielectric loss angle tangent relying on the dielectric electron polarization or interface polarization attenuation to absorb electromagnetic waves.The smaller the volume resistivity of the material the better the absorption effect but the reduction of the surface resistivity of the material also increases the reflective ability of the material.Electromagnetic waves in free space are difficult to enter the interior of the material and cannot achieve the purpose of absorbing waves.Therefore there is an optimal conductivity range and its absorption efficiency depends mainly on the conductivity and dielectric constant of the material.The results can be used as reference for designing and developing e