【作者】 胡礼初；

【导师】 张海燕；

【作者基本信息】 广东工业大学 ， 微电子学与固体电子学， 2007， 硕士

【摘要】 本文旨在制备和研究具有良好的低频波段微波吸收功能的吸波剂——碳纳米管复合吸波材料，Fe／Al₂O₃磁性复合吸波材料，Fe、Co、Ni合金及其复合吸波材料。采用热CVD法制备多壁碳纳米管，并运用高温氧化、浓盐酸处理和HNO₃／H₂SO₄混酸回流工艺对其进行纯化；采用FTIR、TEM和EDS比较各工艺对碳管表面结构的影响程度，并通过矢量网络分析仪测定经不同工艺纯化后，碳管在0.5～6.0GHz低频波段的介电常数和磁导率数值。采用自蔓延燃烧法和氢气还原制备不同成份比例的Fe／Al₂O₃磁性复合粉。运用XRD、SEM、DSC-TGA分析复合粉末的结构、形貌和抗氧化性能，并采用同轴波导法测量其2.0～6.0GHz范围内的电磁参数数值。采用自蔓延燃烧法制备出系列的Fe、Co、Ni及其二元和三元的合金微粉，研究合金组成、物相、电磁参数之间的关系，最终得出具有最佳介电常数和磁导率的成分配比方案。通过Matlab模拟计算，归纳出0.5～6.0GHz低频波段内的电磁参数（ε′，ε″，μ′，μ″）各数值对反射率的影响规律。运用矢量网络分析仪，研究不同基材、多种吸波剂混合的等效电磁参数。最后，根据电磁波传输理论，编写反射率模拟程序，并将模拟结果与单层、双层样板的实测反射率相比较，以此来验证程序的准确性。结果表明：碳管中无定形碳的存在，有效地提高了碳管的介电损耗；长时间的浓盐酸或混酸回流处理，会对碳管的介电常数构成明显地影响。当Fe₂O₃／Al₂O₃复合物中Al：Fe=1：9时，还原所得的Fe／Al₂O₃抗氧化性能得到明显的提高；Al₂O₃的低介电损耗和绝缘性能，可以对复合物2.0～6.0GHz波段内的介电常数实部和虚部进行有效地调整。Ni_0.8Co_0.2和Fe_0.5Ni_0.5是二元合金中磁损耗较好的组成，它们的物相分别为（Ni，Co）固溶体和Taenite镍纹石系（Fe，Ni）合金。三元合金Fe_0.5Ni_0.4Co_0.1具有优异的电磁性能，其μ″的最大相对值达到1.9，该合金物相为Taenite系（Fe，Ni）晶格中固溶入Co。将15wt％碳纳米管与CIP-A羰基铁混合，发现电损耗型的碳纳米管的加入，可以有效地提高磁性吸波材料的介电常数实部。同样的，5wt％碳纳米管与Fe_0.5Ni_0.5合金粉混合，复合物的介电常数实部也得到了提高。通过对含碳纳米管的单层涂层、碳纳米管和石墨双层涂层的模拟结果与实测反射率进行比较，证明了电磁波传输线模型是可以应用于吸波涂层的反射率模拟。更多还原

【Abstract】 The purpose of this thesis is to prepare and investigate the microwave absorbing materials of excellent absorption properties in low frequencies, which include: Carbon NanoTubes （CNTs） composites, Fe/Al₂O₃ magnetic composites, Fe-Co-Ni magnetic alloys and their composites.CNTs prepared by thermal CVD method, were treated by high-temperature oxidation method, and by concentrated HC1 method, or by HNO₃-H₂SO₄ mixture in different conditions. FTIR, TEM and EDS were employed to study the effect of these treatments on external structure of CNTs. The complex permittivity and permeability were measured by vector network analyzer in the range of 0.5～6.0 GHz.Fe/Al₂O₃ magnetic composites of different components were produced through the method of Self-propagating High-temperature Synthesis （SHS） and hydrogen-deoxidization. Their detailed characterization and anti-oxidation were investigated by XRD, SEM, DSC-TGA, and the electromagnetic characterization were measured by agilent microwave network analyzer in the range of 2.0～6.0GHz. The binary and ternary alloys of Fe, Co and Ni were also prepared by SHS method. The components with the best electromagnetic parameters have been found by studying the relations of components, phase structures and electromagnetic parameters.In order to research the intrinsic reasons for microwave absorption of composites, simulation program of reflectivity basing on electromagnetic parameters were completed and run by the software of MATLAB. The equivalent electromagnetic parameters of different basic materials, multi- RAM were studied, too. Finally, the model of Microwave Transmission-Line was examined by comparing the simulated results and actual measurement of single-layer and two-layer coatings.The experiments showed that existence of amorphous carbon in CNT samples could improve the dielectric dissipation. And concentrated HC1 or HNO₃-H₂SO₄ mixture treatments for long time would change the polarization performance and external structure of CNTs, and affect the permittivity of CNTs in Low-frequency bands finally.The ability of anti-oxidation was improved greatly, when the ratio （atoms） of Al-to-Fe is （or over） 1: 9 in Fe/Al₂O₃ composites. Adding different Al₂O₃ concentration would effectively modify the real and imaginary permittivity value of the composites, because of the low dielectric performance and insulation of Al₂O₃.Ni_0.8Co_0.2 and Fe_0.5Ni_0.5 had better magnetic loss than other Fe, Co, Ni binary alloys. And their phase structures were Ni-Co solid solution, and Fe-Ni Taenite solution individually. The ternary Fe_0.5Ni_0.4Co_0.1 whose imaginary permeability reached the maximum value of 1.9, had the best magnetic property among any unitary and binary magnetic alloys. Its main phase structure also was Fe-Ni Taenite solution, but Co was dissolving into Fe-Ni basic solid solution.15wt%CNTs has been incorporated into CIP-A/wax composite. And the results showed that the real permittivity of composite had effectively increased by 9. When 5wt%CNTs mixed with Fe_0.5Ni_0.5/epoxy composite, the permittivity also increased, too.By comparing the simulation and actual measurements of CNT single-layer coating and two-layer coating, we had found that the model of Transmission-Line could accord with the actual measurements very well.更多还原