【作者】 强成文；

【导师】 徐金城；

【作者基本信息】 兰州大学 ， 材料物理与化学， 2011， 硕士

【摘要】 近年来,国内外对于纳米吸波剂的研究特别是在纳米复合吸波材料的选取和制备方法上取得巨大的进展。尤其纳米薄膜复合吸波材料是将薄膜技术与纳米技术结合起来,与其他的吸波材料相比具有厚度薄,质量小,吸波性能强等优点而逐渐成为研究的热点,有望成为一种很有前途的新型吸波材料。本论文中我们对碳纤维进行表面改性,通过化学镀在其表面涂覆一层磁性薄膜来改善其电磁特性,从而获得性能较好的吸波材料。(1)我们对Izaki的方法进行改进,将敏化-活化处理过的碳纤维放入含有10 mM的[Fe(NO3)3·9H2O]和30 mM的DMAB的水溶液中,在合适的温度和时间的条件下制备了Fe3O4/CFs复合材料。得出了如下结论：a本实验的最佳反应条件为：镀液成分和浓度分别为10 mM的[Fe-(NO3)3·9H2O]和30 mM的DMAB,反应温度为90℃,反应时间为1 h。b采用VSM在室温条件下测试发现碳纤维没有任何磁性,但是Fe3O4/CFs复合材料表现出良好的铁磁性能。c 50%质量分数的Fe3O4/CFs复合材料在电磁波频率在0-18 GHz范围内表现宽频和较强的电吸收性能。d在电磁波频率为6.37 GHz时,复合材料的反射率达到了最强的-35 dB(对应的吸收率大于99.99%),对应的厚度为4.41 m。当反射率小于-20 dB(吸收率为99%)时,电磁波频率覆盖了5.49-7.75 GHz之间的所有范围,基本上满足中频段的强吸收要求。(2)我们采用电化学的方法分别在ITO导电玻璃表面和碳纤维表面镀一层FeCo合金薄膜。通过对其结构的分析及性能的测试,得出以下结论：a通过调节电镀液的成分我们发现当溶液中Co2+/Fe2+的比例,从0.50/0.50变化到0.90/0.10时,薄膜中Co的成分即X从40%上升到85%,薄膜中铁的成分从60%下降到15%。当薄膜中Co的含量发生变化时,我们发现随着X的增加,材料的Ms先增大后减小。Hc随着X的增加,先减小后增大。这说明FeCo合金薄膜的磁性和电镀液成分有着密切的关系。b通过固定电镀液成分。改变在此镀液成分下的pH值,我们发现随着pH值的增加,FeCo薄膜的饱和磁化强度先增加后减小,而矫顽力呈现出先减小后增大的趋势。c我们找到本实验条件下FeCo合金磁性最强时的最合适的镀液成分与pH值,还是采用电化学的方法在此电镀液的成分及pH值条件下在碳纤维表面电镀一层FeCo合金薄膜。我们发现FeCo/CFs复合材料表现出良好的铁磁性能。d 50%质量分数的FeCo/CFs复合材料在电磁波频率为2-18 GHz之间表现出了一定的吸波性能。e在频率为2.0 GHz时,材料的反射率达到了-14.7 dB,对应的厚度为3.3mm。当FeCo/CFs复合材料的反射率小于-10 dB(吸收率为90%),电磁波频率覆盖了1.6-2.1 GHz之间的所有频率更多还原

【Abstract】 The selection and preparation of absorption materials were made a great progress in recently years. In particular, nano-thin films composites absorbing materials combine with nanotechnology have caused a hot research. It can be used promising new absorbing materials due to their small quality, thinner, absorbing properties and other advantages. Many treatments have been used to enhance the absorbing property of carbon fibers, including changing the cross-section shape and size of carbon fibers, modifying the carbon fiber surfaces such as coating the surface with a layer of metal or other oxide. So we coated magnetic films by chemical method to improve its electromagnetism properties. The excellent magnetic and microwave absorption properties of nano-absorbing composites were obtained.(1)Therefore, by modifying Izaki’s method, a convenient way was presented in this paper, the pretreated CFs were immersed into aqueous solution at best temperature and time. The conclusions were found as follows:a. The best reaction condition is queous solution containing 10 mM iron nitrate 9-hydrate [Fe (NO3)3·9H2O] and 30 mM dimethylamin borane complex (DMAB) [(CH3)3NHBH3] treated at 90℃forl h.b. The magnetic properties of the Fe3O4/CFs composites were measured with VSM at room temperature. We found that the carbon fibers exhibited paramagnetism. But the Fe3O4/CFs composites exhibited ferromagnetism.c. The electromagnetic parameter of 50 wt.% Fe3O4/CFs composites is measured by the coaxial line method at 0-18 GHz.d. The lowest reflectivity of the Fe3O4/CFs composites is-35 dB at 6.37 GHz for a layer of 4.41 mm in thickness. The result shows that the strong absorption (RL<-20 dB) is broadened from the 5.49 to 7.75 GHz with the thickness varying from 5.12 to 2.90 mm.(2) Fe-Co films were prepared by the electroplating method. ITO glass and carbon fibers were used as the substrates, respectively. In this study, the structure and magnetic property of electrodeposited Fe-Co films were investigated. The conclusions were found as follows:a. By changing the molar ratio of Co2+/Fe2+ in the reaction electrolyte from 0.50/0.50 to 0.90/0.10, the Co content x in the films ranges from 40% to 85%. Mean- while, the Fe content in the films decreases from 60% to 15%. It can be seen that Ms increases with the Co content x increasing from 0.40 to 0.70, reaches a maximum value at x= 0.70, and then decreases with further increasing of x. Meanwhile, He decreases with the Co content x increasing from 0.40 to 0.70, reaches a minimum value at x= 0.7, and then increases with the further increasing of x. The change of the magnetic properties of the Fe-Co films can be attributed to the increase of Co content in the deposited films.b. The fixed electrolyte were fasted at room temperature as the pH values varying from 2.1 to 4.3. Ms increases with the pH values increasing from 2.1 to 2.9, reaches a maximum values at pH=2.9, and then decreases with further increasing of pH values. Meanwhile, Hc decreases with the pH values increasing from 2.1 to 2.9, reaches a minimum values at pH=2.9, and then increases with the pH values increasing from 3.9 to 3.7, reaches a maximum values at pH=3.7, and then decreasing with further increase of pH values.c. The magnetic performance of the FeCo films shows the best composition and pH values. We coated FeCo films on carbon fibers by electroplating method. We found the FeCo/CFs composites exhibited ferromagnetism.d. The electromagnetic parameter of 50 wt.% FeCo/CFs composites is measured by the coaxial line method at 2-18 GHz.e. The lowest reflectivity of the FeCo/CFs composites is-14.7 dB at 2.0 GHz for a layer of 3.3 mm in thickness. The results show that the reflectivity is less than-10 dB the reflection loss of microwave absorption materials achieves 90%. The reflectivity of Fe3O4/CFs composites is less than-10 dB over the range of 1.6-2.1 GHz.更多还原