Co3O4/Biomass-rGO异质结构纳米片的微波吸收性能

目的调节Co3O4纳米粒子的电磁匹配,以实现最佳的电磁波吸收性能,同时实现对轻质、强吸收、宽频带、小厚度电磁波吸收材料的追求。方法通过玉米秸秆制备生物质-rGO,采用水热法将生物质-rGO引入到Co3O4纳米粒子中制备具有异质结构的Co3O4/biomass-rGO纳米片。通过X射线衍射分析仪、透射电子显微镜、高分辨透射电子显微镜测试,分别对Co3O4/biomass-rGO异质结构纳米片的组成、形貌以及结构进行表征,同时通过矢量网络分析仪测试分析生物质-rGO的引入对Co3O4/biomass-rGO异质结构纳米片吸波性能的影响。结果生物质-rGO的引入明显提高了Co3O4/biomass-rGO异质结构纳米片在2~18 GHz频率范围的电磁波吸收性能,不仅降低了有效吸收体厚度,同时还拓展了有效吸收频带宽度。在厚度为1.5 mm、频率为15.8 GHz时,达到–36.1 dB的最大反射损耗值。有效吸收频带宽度为15 GHz,在S、C、X、Ku波段均存在有效吸收,实现了在1.0~5.5 mm宽厚度范围内的全部有效吸收。结论通过引入生物质-rGO可以有效改善Co3O4的电磁匹配和介电损耗。     

钴镍铜合金纳米线的制备及微波吸收性能

采用脉冲电化学法沉积法在AAO模板上制备了钴镍铜合金纳米线,XRD测试表明纳米线有Co,Ni,NiCu和CoCu4个磁性相共存。在平行于和垂直于长轴方向上所测的磁滞回线表明:钴镍铜合金纳米线阵列具有弱的各向异性。磁性合金纳米线与石蜡的复合材料在GHz频段内具有较好的电磁波吸收性能:当吸波涂层的厚度为4mm时,其最小反射损耗可达–30dB。     

Microwave absorption properties of TiN nanoparticles

TiN nanoparticles with an average diameter of 15 nm or so were prepared by the reaction of spongy Ti and NH₄Cl at about 530 °C. The electromagnetic parameters of the TiN nanoparticles/wax composite were measured by a coaxial line method. The nanoparticles exhibit good microwave absorbing ability owing to dielectric loss, and the measured reflection loss reaches a minimum value of −16.1 dB at 13.8 GHz. The interfaces between nanocrystalline TiN and the thin amorphous TiO₂ layer on the TiN surface contribute dominantly to the high permittivity and good microwave absorbing properties.     

PVP对石墨烯/Fe3O4复合吸波材料形貌及吸波性能的影响

目的研究分散剂PVP对Fe_3O_4在石墨烯表面分散性的影响,以获得吸波性能良好的吸波材料。方法采用溶剂热法制备石墨烯/Fe_3O_4复合吸波材料,通过扫描电子显微镜、X射线衍射分析仪、X射线光电子能谱、矢量网络分析仪等对石墨烯/Fe_3O_4复合吸波材料进行表征,并研究了PVP添加与否在石墨烯/Fe_3O_4复合吸波材料形貌及吸波性能的影响。结果添加PVP后的石墨烯/Fe_3O_4复合吸波材料与未添加PVP的相比,Fe_3O_4在石墨烯表面的团聚现象明显减少,尺寸显著减小。通过计算机模拟反射率,未添加PVP的石墨烯/Fe_3O_4复合吸波材料在匹配厚度d=2.00 mm时,在16.25 GHz处达到最大反射损耗-18.79 dB,复合材料反射损耗小于-10 dB的频带宽度可达4.1 GHz。添加PVP的复合材料在匹配厚度d=2.00 mm时,在16.25 GHz处达到最大反射损耗-25.88 dB,复合材料反射损耗小于-10 dB的频带宽度可达4.5 GHz,相比未添加PVP的复合吸波材料,反射损耗小于-10 dB的频带宽度增加0.4 GHz,最大反射损耗提高7.09 dB。结论 PVP能提高Fe_3O_4在石墨烯表面的分散性,并在石墨烯表面形成良好的导电网络,使复合材料的吸波性能明显提升。     

Zn0.6Cu0.4Cr0.5Fe1.46Sm0.04O4 ferrite and its nanocomposites with polyaniline and polypyrrole: Preparation and electromagnetic properties

The nanosized Zn_0.6Cu_0.4Cr_0.5Fe_1.46Sm_0.04O₄ (ZCCFS_0.04O) ferrite doped with Sm was prepared by a rheological phase reaction method. These nanoparticles were further used as templates for the fabrication of polyaniline-linked ZCCFS_0.04O and polypyrrole-linked ZCCFS_0.04O nanocomposites via in situ polymerization method. The structures, morphology and electromagnetic property of ferrite powders and nanocomposites were characterized by X-ray powder diffractometer (XRD), transmission electron microscope (TEM), four-point probe resistivity instrument (SDY-4) and vibrating sample magnetometer (VSM). The electronic and magnetic properties of the nanocomposites are tailored by controlling the ferrite content. The pure polyaniline (PANI) and polypyrrole (PPy) films with thickness of 2 mm show a maximum reflection loss of ?20.93 dB and ?19.68 dB at 16 GHz and an available bandwidth (frequency difference between points where the absorption is less than ?8 dB) of 5.9 GHz and 6.2 GHz, respectively. When relative content of the ZCCFS_0.04O in PANI/ZCCFS_0.04O and PPy/ZCCFS_0.04O composites with respect to aniline (pyrrole) monomer is approximately 20 wt%, the maximum reflection loss of ?22.46 and ?20.90 dB appear at approximately 14.07 and 14.05 GHz, and available bandwidth is broadened to 11.15 and 11.30 GHz, respectively. The results show that both of PANI/ZCCFS_0.04O and PPy/ZCCFS_0.04O composites can be used as advancing microwave absorption and shielding materials due to their favorable microwave absorption properties.     

钴-铁沉积碳化硅颗粒及其吸波性能

目的提高碳化硅微粒的微波吸收性能。方法利用改进的化学镀法,以硫酸钴和硫酸亚铁为主盐,次亚磷酸钠为还原剂,施镀温度为50℃,使用机械搅拌和超声分散相结合的方法,在预处理后的微米碳化硅颗粒表面沉积钴铁合金。通过X射线衍射仪(XRD)、X射线能谱仪(EDS)和扫描电子显微镜(SEM)分别对化学镀前后材料的结晶状态、组成成分和形貌特征进行了表征;利用矢量网络分析仪对化学镀前后材料在2~18 GHz频率范围内的电磁性能进行了测试,并通过计算得到了材料微波反射率损耗。结果钴铁合金呈微球状均匀沉积在碳化硅表面,有效地改善了碳化硅材料的电磁性能和微波吸收性能。碳化硅的介电常数虚部存在界面极化和缺陷极化两个弛豫峰(9.1、13.8 GHz),而沉积钴铁合金后,碳化硅材料Co-Fe/SiC增加了两个弛豫峰:介电弛豫峰(11.7 GHz)和磁弛豫峰(12.6 GHz)。正是由于Co-Fe合金对微波信号的介电弛豫和磁弛豫,有效提升了材料的吸波性能。当吸波层厚度为2.4 mm时,反射率在10 dB以上的吸收带宽达到3.8 GHz,20 dB带宽可以达到1.5 GHz。当吸波层厚度为2.3 mm时,频率为12.7 GHz时达到最大吸收峰值–43 dB。结论在碳化硅材料表面沉积钴铁合金是一种有效改进材料微波吸收性能的方法,且该材料是一种高效、宽频的微波吸收材料。     

Characteristics of permittivity and permeability spectra in range of 2-18 GHz microwave frequency for La1-xSrxMn1-yByO3 （B=Fe, Co, Ni）

Doped LaMnO3 has unusual electromagnetic properties, which makes it possible for this material to be used for absorbing microwave. LaMnO3 systems doped by Sr at site A and Fe or Co, Ni at site B were prepared by sol-gel as an microwave absorption material and their permittivity and permeability spectra were measured by microwave vector network analyzer in the frequency range of 2-18 GHz. A novel phenomenon is discovered that the complex permittivity, complex permeability and electromagnetic loss tangent have suddenly a step change at a certain frequency and the step-change frequency is relevant to content of Sr and Fe or Co, Ni. The samples show mainly dielectric loss when microwave frequency is smaller than the step-change frequency, and mainly magnetic loss when larger than that frequency. It is indicated that anti-ferromagnetic clusters in the material can absorb energy quantum of microwave electromagnetic field to change into ferromagnetic clusters because they can overcome higher energy barrier when the frequency of incident microwave reaches a certain value.     

Synthesis and microwave absorbing properties of polyaniline/MnFe2O4 nanocomposite

Conductive polyaniline (PANi)-manganese ferrite (MnFe₂O₄) nanocomposites with core-shell structure were synthesized by in situ polymerization in the presence of dodecyl benzene sulfonic acid (DBSA) as the surfactant and dopant and ammonium persulfate (APS) as the oxidant. The structure and magnetic properties of manganese ferrite nanoparticles were measured by using powder X-ray diffraction (XRD) and vibrating sample magnetometer (VSM), respectively. Its morphology, microstructure and DC conductivity of the nanocomposite were characterized by scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR) and four-wire-technique, respectively. The microwave absorbing properties of the nanocomposite powders dispersing in resin acrylic coating with the coating thickness of 1_.4 mm were investigated by using vector network analyzers in the frequency range of 8-12 GHz. A minimum reflection loss of −15.3 dB was observed at 10.4 GHz.     

基于双磁介质层复合的超材料低频吸波体研究

本研究将磁性吸波涂层融入至超材料的结构设计中,得到了一种新型低频复合超材料吸波体,吸波体由环形电阻膜、双层磁性吸波涂层和金属背板组成。采用CST仿真软件计算了超材料吸波体的吸收性能,研究了吸波体各个结构参数对吸收性能的影响。仿真结果表明,设计的超材料吸波体厚度为2.5 mm时,在1.9和4 GHz处存在2个吸收峰,在1.59～6.59GHz频率范围内反射损耗低于-8dB,吸收带宽达到5GHz。通过吸波体电磁场分布对吸波机理进行了讨论。结果表明,吸波体低频吸收带宽的增加是由于表面的电阻膜图案改变了超材料吸波体的电场分布和磁场分布,促进了磁介质层的损耗。最后制备了吸波体样品并进行了反射率测试,实物测试结果与仿真结果基本一致,说明设计制备的吸波体具有优异的低频吸波性能,吸波带宽相比磁性吸波涂层大幅提高。     

Facile synthesis, magnetic and microwave absorption properties of Fe3O4/polypyrrole core/shell nanocomposite

Fe₃O₄/polypyrrole (PPy) core/shell nanocomposite, with Fe₃O₄ nanoparticle as core and PPy as shell, could be facilely synthesized via in situ chemical oxidative polymerization of pyrrole monomers on the surface of Fe₃O₄ nanoparticles. The results indicate that core/shell nanocomposite consists of Fe₃O₄ core with the mean diameter of 100 nm and adjacent PPy shell with a thickness of about 70 nm. The as-prepared Fe₃O₄/PPy core/shell nanocomposite exhibits a saturated magnetization of 20.1 emu/g and coercivity value of 368.3 Oe, respectively. The electromagnetic characteristics of Fe₃O₄/PPy core/shell nanocomposite were also investigated with a vector network analyzer in the 2-18 GHz range. The absorbing peak position moves to lower frequency with increasing the thicknesses of samples. The value of the minimum reflection loss is −22.4 dB at 12.9 GHz for Fe₃O₄/PPy core/shell nanocomposite with a thickness of 2.3 mm, and a broad peak with a bandwidth lower than −10 dB is about 5 GHz. Such strong absorption is attributed to better electromagnetic matching due to the existence of PPy and the special core/shell structure.     

雷达吸波涂层材料的研究进展

讨论了电磁波的吸波机理,及其性能测量和计算方法,叙述了电阻型损耗、介电损耗、磁损耗型三种损耗机制的涂层材料及其电磁波吸收损耗机理,对不同种类的吸波材料在雷达波隐身方面的应用进行了全面的综述,介绍了这一研究方向的最新进展,并分析了每种材料的主要特点。重点讨论了铁氧体、碳纳米管、导电高聚物等吸波材料的微观结构、化学性质、电磁特性对吸波性能的影响。对于磁损耗材料来说,良好的磁性能是其不可忽视的优点,但其密度高,稳定性较差,影响了其性能发挥。针对其存在的缺点,通过掺杂改性、共混等方式可提升涂层材料的吸波性能。在碳系材料中,多壁碳纳米管的吸波性能较好,将磁损耗吸波材料与碳纳米管进行复合、包覆是目前吸波性能提高的主要手段。导电聚合物等新型吸波材料具有质量轻、导电性好的特点,单独使用时,阻抗匹配性差,通过对其掺杂改性或与磁损耗型材料复合,可增强其阻抗匹配性,提升吸波性能。最后,指出了雷达吸波材料未来的研究发展方向。     

La-Ho-Fe合金的制备及其微波吸收特性研究

采用电弧熔炼及高能球磨工艺制备出LaxHo2-xFe17(x=0.0, 0.2, 0.4, 0.6, 0.8) 合金微粉,借助XRD、SEM、VSM和网络矢量分析仪等仪器分别研究La替换对合金微粉的结构、形貌、磁性能及其微波吸收性能的影响。结果表明, 随着La含量的增加,饱和磁化强度和平均颗粒大小都有所增加。LaxHo2-xFe17合金的最小反射峰频率向低频方向移动。其中La0.2Ho1.8Fe17合金具有最好的吸波效果,在最佳匹配厚度1.8 mm下,La0.2Ho1.8Fe17合金的最小反射损耗在8.72 GHz处达到-28.72 dB,反射损耗小于-10 dB的频带宽度达到2.32 GHz。当厚度在1.2-2.4 mm范围里,La0.2H1.8Fe17合金的反射损耗均小于-10 dB,这表明LaxHo2-xFe17是有前途的微波吸收材料,并具有良好的吸收特性。     

Microstructure and microwave electromagnetic properties of Dy~（3＋）-doped W-type hexaferrites

Ba 1 x Dy x Co 2 Fe 16 O 27 (x = 0.00, 0.05, 0.10, 0.15, and 0.20) was prepared by the solid-state method. The phase structure was studied using powder X-ray diffraction (XRD), the electromagnetic properties were measured, and the reflection loss of Dy 3+ -doped ferrite material was calculated using electromagnetic parameters by the transmission line theory. All XRD patterns showed the single phase of the magnetoplumbite barium ferrite without other intermediate phase when x ≤ 0.15. The values of ε′ and ε″ increased slightly with Dy 3+ ions doping. The values of μ″ and μ′ were improved with Dy 3+ doping, exhibiting excellent microwave magnetic performance. The reasons have also been discussed using the electromagnetic theory. Dy substitution could increase microwave-absorbing performance and broaden frequency band (reflection loss (RL) < -10 dB), and the absorbing peak shifted to high-frequency position. When x = 0.2, ferrite layer exhibited the most excellent microwave-absorbing performance at a thin matching thickness of 1.5 mm. The peak value of RL was around -15 dB, and the frequency band (RL < -10 dB) was about 7 GHz (from 8 to 15 GHz).     

Dy对Pr2Fe17合金微波吸收特性的影响

采用电弧熔炼及高能球磨工艺制备出 DyxPr2-xFe17 (x =0.0, 0.1, 0.2, 0.3, 0.4) 合金微粉,借助XRD、SEM、振动样品磁强计和网络矢量分析仪等仪器分别对合金微粉的结构、形貌、磁性能及其微波吸收性能进行了研究。研究发现, 随着Dy含量的增加,DyxPr2-xFe17微粉的饱和磁化强度降低。DyxPr2-xFe17合金的最小反射峰频率随Dy含量的增加往高频方向移动,最小反射损耗呈先增大后减小的变化趋势;其中Dy0.3Pr1.7Fe17合金具有最好的吸波效果,在最佳匹配厚度2.5 mm下,Dy0.3Pr1.7Fe17合金的最小反射损耗在5.04 GHz处达到-42.38 dB左右,反射损耗小于-10 dB的频带宽度达到了1.20 GHz。     

高性能雷达吸波涂层的制备及其损伤行为

以羰基铁粉为吸收剂、聚氨酯为胶黏剂,制备具有优异吸波性能的雷达吸波涂层,并基于矢量网络分析仪、电磁模拟软件Ansoft HFSS以及弓形框测试系统,对涂层电磁特性、损伤模型以及吸波性能进行研究。结果表明:雷达吸波涂层在垂直入射条件下具有优异的吸波性能,当涂层厚度为0.8 mm时,其反射损耗峰在7.2~12.8 GHz均达到?8 dB;在斜入射条件下也具有优异的吸波性能,当涂层厚度为0.8 mm、入射角为60°时,其反射损耗峰在5.5~18 GHz均达到?10 dB。相比于失效模式如雷达吸波涂层分层脱粘,损伤脱落对其吸波性能的影响更为明显。随着损伤脱落面积的增加,雷达吸波涂层的吸收强度（尤其是X波段）明显降低,且最小反射损耗峰往高频移动。通过对高性能雷达吸波涂层的脱落、分层等损伤行为的研究,为后续进行雷达吸波涂层维护与建立失效性评估标准具有极大的现实和军事意义。     

钴纳米粒子改性石墨烯复合材料的电磁性能

采用化学镀的方法,先后用氯化亚锡敏化、氯化钯活化,在石墨烯表面沉积钴纳米粒子。XRD、TEM结果显示钴在石墨烯表面的晶体结构和含量因钴前驱体盐和还原剂浓度而异。电磁测试结果表明:钴含量的增加和石墨烯的还原均能提升Co-RGO的电导率;同时,Co-RGO纳米复合材料由于具有磁损耗和大量界面引入的介电损耗,吸波性能优异,Co-RGO*1在1~18 GHz频段内反射率低于-10 d B的频宽约为4 GHz,Co-RGO*2在26.5~40 GHz频段内反射率均小于-23 d B。     

高岭土表面镀覆Co-P层及其微波吸收性能研究

选用产于茂名和苏州的天然高岭土为原料,通过改性处理和化学镀工艺制备了高岭土复合物MK/Co-P和SK/Co-P,对比分析其显微结构、磁性和微波吸收性能。结果表明:Co-P镀层均为单相密排六方结构,在MK/Co-P中均匀沉积在高岭土片层表面,Co和P含量(质量分数)分别为36.62%和4.41%。而在SK/Co-P中镀层对高岭土微米级团簇包覆完整,Co和P含量显著下降。与SK/Co-P相比,MK/Co-P的饱和磁化强度和矫顽力较高,介电常数和磁导率大幅上升,其匹配厚度在2.0~3.0 mm的有效吸波频带(RL≤–20 d B)覆盖4.7~8.2 GHz,反射损耗最大值为–27.32 d B,应用前景较好。     

Synthesis of Flowerlike MoS2/CoNi Composites for Enhancing Electromagnetic Wave Absorption

The hierarchical MoS₂/CoNi composites were successfully synthesized by a two-step hydrothermal method. The large surface area of the MoS₂ enhances the dispersivity of the CoNi nanoparticles and the formation of abundant MoS₂/CoNi interfaces, which make an important contribution to the dielectric loss, and the introduction of the CoNi improves impedance matching and introduces magnetic loss, which can improve the absorption performance to electromagnetic waves. Through the calculation of the electromagnetic parameters, the minimum reflection loss (RL) value of the MoS₂/CoNi composites achieves -41.44 dB at 13.53 GHz under a thickness of 2.0 mm and the corresponding effective absorption bandwidth (RL below -10 dB) is 5.6 GHz. The MoS₂/CoNi composite has the potential to be applied to microwave absorption due to its strong absorption and wide bandwidth.     

Fe—B／Fe3O4纳米复合粒子的吸波性能研究

采用NaBH4溶液还原FeCl3的方法制备Fe-B颗粒,并在Ar／O2气氛下干燥,使其表面不完全氧化,得到了Fe—B／Fe3O4纳米复合粒子。该粒子具有清晰的核壳结构,内核Fe-B尺寸约为20－50nm,外壳Fe3O4厚度约为3nm。将样品与石蜡按质量比1：1制成同轴样品,测试其2～18GHz下的电磁参数并进行分析计算,研究发现,由于偶极子极化、自然共振和涡流损耗,该纳米复合粒子粉末具有优良的吸波性能,其反射损耗RL在频率为12．0GHz的时候达到最小值－31dB,RL值低于－20dB（即吸收率高于99％）的频率范围为10．1～14．2GHz。     

CoNi/g-C3N4/GQDs纳米胶囊的宽频电磁波吸收调制

通过两步法制备了CoNi/g-C₃N₄/GQDs三元复合纳米胶囊,利用XRD、SEM、FT-IR对其物相组成和微观形貌进行了详细表征,并对材料在1~18 GHz的微波电磁参数和吸波性能进行了测试和分析。结果表明,类海胆状的CoNi颗粒可以保证其复磁导率在较高水平,同时g-C₃N₄和GQDs在CoNi核心表面的复合可以通过界面偶极和本征偶极的互补性调控,调制微波介电特性和损耗。在L-Ku频段范围内,CoNi/g-C₃N₄/GQDs三元纳米胶囊通过介电调制的方式,极大地改善了电磁阻抗,获得了宽频吸收效果和吸波性能增强,在f=12.94 GHz和d=2.4 mm时,复合材料的反射损耗(RL)最小值达到-33.45 dB,当材料厚度为2.6 mm时,有效吸收频宽(RL<-10 dB)达到3.5 GHz。