碳纳米管加载量对复合材料吸波性能的影响

将不同质量分数的碳纳米管和环氧树脂充分混合，制成复合吸波涂料并涂覆在铝板上制成吸波涂层。采用TEM对碳纳米管的形貌进行观察。使用反射率扫频测量系统HP8757E标量网络分析仪检测复合材料的吸波性能。结果表明，复合材料在2GHz～18GHz均有良好的吸波性能。碳纳米管加载质量分数为8％和10％时，复合材料吸波性能最佳。8％碳纳米管加载量，峰值最大，达到～22．55dB，波峰出现在12．32GHz，带宽分别为2．56GHz（R〈-8dB）和4．00GHz（R〈-5dB）。10％碳纳米管添加量，带宽最大，分别达到2．80GHz（R〈-8dB）和7．00GHz（R〈-5dB），波峰出现在13．67GHz，峰值为-14．59dB。     

吸收剂含量对结构吸波材料吸波性能的影响

用实验和理论计算研究了碳黑、铁氧体含量对碳纤维毡／环氧树脂结构吸波材料吸收性能的影响。并由此制得了最在吸收率为－１４．９３ｄＢ、吸收率超过－１０ｄＢ的有效带宽接近雷达的整个工作频率区间的较高性能结构吸波材料的厚度为５ｍｍ,密度为１．２２ｇ／ｃｍ＾２３     

空心粉煤灰对铁氧体-炭黑/水泥基复合材料吸波性能的影响

通过改变空心粉煤灰微珠、铁氧体、炭黑的配比,分析了影响混凝土电磁吸收效能的主要因素,并探讨了空心粉煤灰微珠、铁氧体和炭黑的加入对水泥基复合材料电磁吸收性能的影响机制。结果表明:8~18GHz频率范围内,空心粉煤灰微珠是影响水泥基复合材料吸波性能的最主要因素,最佳水平组合为20wt%铁氧体、20wt%粉煤灰、10vol%炭黑,-10dB吸收带宽可达10GHz且明显优于无粉煤灰样品,其机制在于空心粉煤灰微珠的掺入同时改善了材料表面透射性能和介电损耗。     

石墨烯增强FeSiAl-MoS2/PLA复合材料吸波性能

多元材料复合是制备轻质、宽频和强吸收吸波材料的有效方法。以聚乳酸(PLA)为基体,FeSiAl、MoS₂和石墨烯(GN)为填料,通过球磨和熔融挤出两步法制备了可用于熔融沉积成形(FDM)的FeSiAl-MoS₂-GN/PLA复合材料。采用XRD、拉曼光谱、SEM和矢量网络分析仪分别对复合材料的物相结构、微观形貌和电磁特性进行了表征,并研究了石墨烯含量对复合材料吸波性能的影响。研究表明:石墨烯、FeSiAl和MoS₂随机分散在PLA基体中,形成了复杂的导电网络;多元材料复合构筑了丰富的介电/磁异质界面,有利于促进界面极化;当石墨烯含量增加时,复合材料的吸波性能随之增强,当石墨烯含量为5wt%时,复合材料的吸波性能最佳,在厚度为1.7 mm时最小反射损耗为?27.90 dB,在厚度为1.9 mm时有效吸收带宽为4.96 GHz(12.64~17.60 GHz)。其优异的吸波性能归因于良好的阻抗匹配及介电损耗和磁损耗之间的协同作用。      

稀土掺杂碳纳米管/聚氯乙烯复合材料的吸波性能研究

利用La(NO3)3和Ce(NO3)3掺杂的碳纳米管(MWCNTs-La(NO3)3和MWCNTs-Ce(NO3)3)作为吸收剂、聚氯乙烯(PVC)作为基体,制备出MWCNT-La(NO3)3(或Ce(NO3)3)/PVC复合材料。运用透射电子显微镜和X射线衍射仪对MWCNTs、MWCNTs-La(NO3)3、MWCNTs-Ce(NO3)3的微观结构进行表征分析,使用同步热分析仪和矢量网络分析仪对MWCNT/PVC、MWCNT-La(NO3)3/PVC、MWCNT-Ce(NO3)3/PVC复合材料的热解行为和吸波性能进行测试分析。结果表明,在2～18GHz频率范围内,适量掺杂La(NO3)3或Ce(NO3)3可以使MWCNT/PVC复合材料的吸波性能大幅度提高,而热解行为变化不明显。在反射率R<-10dB的范围内,MWCNT-Ce(NO3)3/PVC复合材料的吸收频宽(约为5.4GHz)虽然不及MWCNT-La(NO3)3/PVC的吸收频宽(约为5.6GHz)宽,但是吸收频段和吸收峰峰值均向高频区域移动,有利于提高复合材料的高频吸波性能。     

炭纤维及其复合材料的吸波性能和吸波机理

炭纤维和炭纤维复合材料在隐身技术中已经得到了广泛应用。通过分析连续炭纤维、短切炭纤维、螺旋形炭纤维、异形截面炭纤维、掺杂改性炭纤维及其复合材料的微波电磁特性和吸波性能,探讨了以上几种炭纤维的吸波机理,其中螺旋形炭纤维和异形截面炭纤维是最有发展前景的两种吸波炭纤维。     

SiC/CNTs纳米复合材料吸波性能的研究

采用聚碳硅烷前驱体转化法制备了SiC/CNTs纳米复合材料, 采用扫描电子显微镜、透射电子显微镜、高分辨电子显微镜对样品进行了微观结构分析, 并测试了材料在2～18GHz频率范围内的电磁参数. 结果表明, 当初始聚碳硅烷/二甲苯溶液浓度为10%～15%时, 聚碳硅烷前驱体转化法在CNTs表面可以制备SiC包覆层均匀致密的复合一维纳米材料. SiC包覆CNTs一维纳米材料的电磁参数测试表明, 其损耗机制以介电损耗为主, 当聚碳硅烷含量为15%时, SiC/CNTs纳米复合材料具有最高的介电常数和损耗角, 较好的电磁波吸收特性, 并表现出复合效应.     

Fe基玻璃包覆微丝的吸波性能研究

实验分析了微丝的组织结构，表明微丝是非晶态的，内部芯丝表面光滑，在长度方向上厚度均匀。用矢量网络分析仪测定了微丝的电磁参数，并进行了不同填充率不同厚度的单层吸波涂层设计，结果显示微丝在微波波段10～18GHz频段范围内具有较好的衰减特性，反射率最小值为--32dB，吸波效果好。     

Fe3O4/CNTs@Cf复合材料的制备及其吸波性能的研究

为了改善传统碳材料的吸波性能,获得具有多元吸波机理的吸波材料,本文通过化学气相沉积法在碳纤维表面原位生长碳纳米管,后采用溶剂热反应在CNTs@C_f上生成Fe₃O₄纳米颗粒,制备出了Fe₃O₄/CNTs@C_f复合材料,并对其吸波性能进行研究,分析了复合材料的合成机理和吸波机理。其反射损耗在C波段可达-43.02 dB,随着Fe₃O₄纳米颗粒含量的进一步增加,其吸波性能下降。     

SiO2对羰基铁/炭黑双层吸波涂层吸波性能的影响

以羰基铁和炭黑分别用于匹配层和吸收层制备了具有阻抗渐变结构(匹配层+吸收层)的1.2 mm厚环氧树脂基吸波涂层。通过在匹配层中加入透波剂SiO2,改善了吸波涂层的阻抗匹配性。随着SiO2在匹配层中含量的增加,涂层的反射损耗(RL)得到增强。当匹配层中SiO2与羰基铁及环氧树脂的比值为2∶5∶1时,涂层的吸收峰值达到-17.3 dB,涂层有效带宽(RL<-4 dB)达到5.7 GHz。     

Fe2O3质量分数对粉煤灰颗粒电磁特性的影响

为研究Fe2O3质量分数对粉煤灰颗粒电磁特性的影响,采用高铁粉煤灰颗粒进行试验,通过不同工艺措施改变粉煤灰颗粒Fe2O3质量分数,测试了复合高铁粉煤灰水泥浆体的吸波性能.结果表明,高铁粉煤灰颗粒是电磁波有效损耗介质,是以介电损耗型为主的吸波剂;高铁粉煤灰颗粒介电损耗与磁性氧化铁的质量分数具有较明显的内在相关性;磨细磁选、分级技术可有效改善粉煤灰颗粒的吸波能力;高铁粉煤灰水泥基复合材料具有明显的吸波性能,在12.5～18GHz波段,反射率R<-5dB,最小反射率达-9.88dB,但复合材料的吸波性能与颗粒电磁特性规律有所不同.高铁粉煤灰在吸波建筑材料中具有应用前景.     

Low temperature synthesis of Fe3O4 micro-spheres and its microwave absorption properties

Fe₃O₄ micro-spheres were synthesized by a simple chemical method at 90 °C. It was demonstrated that the final size and morphology of Fe₃O₄ was significantly affected by the additive NaF. The as-synthesized products were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and vector network analysis. The complex permittivity and permeability of paraffin wax and Fe₃O₄ with different Fe₃O₄ volume fraction were measured to increase linearly with increasing volume fraction of Fe₃O₄. When the matching thickness is 4 mm, the calculated reflection loss reaches a maximum value of −45.2 dB at 4.67 GHz with 40% volume fraction of Fe₃O₄.     

Fe/Fe_(3)C/Fe_(3)O_(4)@C磁性微球的制备及吸波性能研究EI北大核心CSCD

薄、轻、宽、强是人们对高效电磁波吸收材料的追求。用食品级柠檬酸铁与蔗糖经过水热反应,高温煅烧制备Fe/Fe_(3)C/Fe_(3)O_(4)@C磁性微球,并通过改变柠檬酸铁与蔗糖的摩尔比,探究柠檬酸铁的含量对复合材料吸波性能的影响,有效地调控电磁参数,从而优化阻抗匹配。实验结果表明,当柠檬酸铁与蔗糖的摩尔比为5∶3时,具有较好的吸波性能:当厚度为2.5 mm时,最小反射损耗为-50.17 dB,小于-10 dB的有效吸收频宽为3.52 GHz,优异的电磁波吸收性能主要得益于微球丰富的界面、孔状结构和Fe/Fe_(3)C/Fe_(3)O_(4)磁学性能的协同作用。     

Thermal, dielectric and microwave absorption properties of polyaniline-CoFe2O4 nanocomposites

The present paper deals with the synthesis of conducting ferromagnetic polyaniline-CoFe₂O₄ (PC) nanocomposites via one-step chemical oxidative polymerization of aniline in the presence of CoFe₂O₄ nanoparticles (30-40 nm). These nanocomposites of PC have been characterized by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and vibrating sample magnetometer (VSM). Extended thermal analysis has revealed that the activation energy of these nanocomposites varies from 75.3 to 84.3 kJ/mol as compared to the activation energy of 50.3 kJ/mol for polyaniline-DBSA. In addition, dielectric and microwave absorption properties of the nanocomposites have been measured in the frequency range of 12.4-18 GHz (Ku-band) which demonstrate that more than 99% attenuation of microwaves (SE_A = 21.5 dB) has been achieved using these nanocomposites. Systematic investigations reveal that the CoFe₂O₄ nanoparticles in the polyaniline matrix have phenomenal effect in determining the microwave absorption properties of the nanocomposites.     

Al含量对漂珠/镁合金可溶复合材料组织与性能的影响

采用搅拌铸造法制备了不同Al含量下的漂珠（FAC）/镁合金可溶复合材料。采用金相显微镜、SEM及XRD观察分析了FAC/镁合金可溶复合材料的微观组织、溶解表面形貌及溶解产物的物相组成,采用力学性能试验机研究了复合材料的压缩性能,采用电化学工作站对复合材料进行电化学性能测试,在常温及水浴锅内进行复合材料在不同温度下的KCl溶液中的溶解试验。结果表明：该FAC/镁合金可溶复合材料主要由α-Mg基体相、β-Mg₁₇Al₁₂相、Mg₂Si相和MgO相组成。随着Al含量的增加,FAC/镁合金可溶复合材料的溶解速率先变快后减慢,在80℃的3wt% KCl溶液中,含15wt% Al的FAC/镁合金复合材料溶解速率最快,为56 mg/（h·cm²）。Al-FAC/镁合金可溶复合材料的抗压强度随Al含量的增加先提高后下降,四种合金的抗压强度均大于300 MPa,最高强度达到372 MPa。     

纳米Fe3O4/聚苯胺复合粒子的制备及其磁性能研究

用水解沉淀法制备纳米Fe3O4,然后在其溶液中原位合成聚苯胺,得到纳米Fe3O4/聚苯胺复合粒子.通过XRD、TEM、JDM等测试对纳米复合粒子的形态、结构及磁性能进行了研究.实验制备的纳米Fe3O4粒子粒径为30nm左右,在其表面沉积聚苯胺后,复合粒子的粒径达到了50nm左右.与纳米Fe3O4粒子相比,纳米Fe3O4/聚苯胺复合粒子的XRD峰形变得更为明锐.纳米复合粒子的磁性能表现出软磁性,与纳米Fe3O4粒子相比,矫顽力减小为0,这可以大大减小材料的磁滞损耗和退磁难度,性能得到改善.     

Electromagnetic wave absorption properties of mesoporous Fe3O4/C nanocomposites

In this work, the mesoporous Fe₃O₄/C nanocomposites with a yolk-shell structure (Fe₃O₄@void@C) were prepared by a silica-assisted strategy, and their microstructure, magnetic properties, and microwave absorption were studied in detail. The BET surface area and the total pore volume of Fe₃O₄@void@C are 171.5 m² g⁻¹ and 0.19 cm³ g⁻¹, respectively. The composites show a saturation magnetization of 35.4 emu/g and reduced hysteresis loss at room temperature. The Fe₃O₄@void@C nanocomposites exhibit the obvious complementarities between complex permittivity and permeability. A minimum reflection loss value of −18.1 dB was obtained for the absorber thickness reaching 2.0 mm, and even the Fe₃O₄@void@C nanocomposites possess a lower reflection loss of-10 dB under 2 GHz bandwidth. We believe that the investigations on the Fe₃O₄@void@C nanocomposite open up a route to develop a new type of composite, which is considered as a promising candidate for microwave absorber.     

Hierarchically nanostructured Fe3O4 microspheres and their novel microwave electromagnetic properties

Magnetite nanoparticles are found to assemble into monodisperse Fe₃O₄ microspheres with diameters ∼ 300 nm and open pores on the shells in ethylene glycol (EG) in the presence of polyethylene 2000 (PEG 2000) and a small quantity of polyethyleneimine (PEI). The hysteresis loops of the magnetic microspheres are measured by a vibrating sample magnetometer (VSM), the ferromagnetic signature emerged with the saturated magnetization of ∼ 80.0 emu g^− 1, and the coercive force of ∼ 208.7 Oe. The synthesized hierarchical microspheres exhibit two microwave magnetic loss peaks: one appears at 4.0-5.0 GHz, the other appears around 16.0-17.0 GHz. The latter peak is attributed to the effect of the morphology of the hierarchical structure. Modern analysis methods SEM, TEM, XRD etc., are employed to figure the detailed structure information of the magnetic hollow spheres.     

Graphene-enhanced microwave absorption properties of Fe3O4/SiO2 nanorods

Fe₃O₄/SiO₂/graphene composite composed of Fe₃O₄/SiO₂ core–shell nanorods and graphene nanosheets were synthesized by a facile wet chemical method. Structure and morphology studies reveal that the Fe₃O₄/SiO₂ nanorods with porous structure and large aspect ratio are densely wrapped by the graphene nanosheets. By changing the graphene content, the electromagnetic properties of the Fe₃O₄/SiO₂/graphene composite can be well tuned. When the weight ratio of Fe₃O₄/SiO₂ to graphene reaches an appropriate value, excellent microwave absorption performance is achieved due to the large electromagnetic losses and good impedance matching. The Fe₃O₄/SiO₂/graphene composite with graphene content of 5 wt.% shows the minimum reflection loss of −27.1 dB at 12.2 GHz when the coating layer thickness is only 1.5 mm.