磁性中孔炭微球复合材料的制备及吸波性能
发布时间：2018-11-17 14:30
【摘要】：随着电子科学技术不断发展,不论是军事雷达隐身领域还是民用电磁污染防护领域,对吸波材料性能的要求越来越高,发展新型"薄、轻、宽、强"的吸波材料已是势在必行。本文以获得"薄、轻、宽、强"的吸波材料为目标,以喷雾干燥法制备的中孔炭微球为基础,制备了一系列磁性复合吸波材料,并对相应的吸波机理进行了探讨。(1)采用喷雾干燥法制备了粒径分布在1-10μm的中孔炭微球(MCMSs),比表面积和孔容最高分别可达到1221 m2/g和2.5 cm3/g。且单纯的MCMSs具有一定的吸波效果,最大反射峰峰值可为-12dB,匹配厚度为2mm。但是非磁性的中孔炭微球阻抗匹配较弱,导致了其吸波效果有限。(2)为提高材料的磁损耗能力,采用湿法浸渍-热处理的方法成功制备了 Fe_3O_4/MCMSs复合材料。复合材料具有优异的流动性和低密度(0.24-0.39 g/cm3)特征,四氧化三铁的纳米颗粒高度分散在MCMSs中孔孔道内;复合材料仍具有较高的比表面积(266-735 m2/g);在2-18 GHz范围内,复合材料以介电损耗为主,12.6 GHz处具有最大反射率-25 dB,小于-10 dB的带宽达4.7 GHz。其优异的吸波性能归结于均相分布的Fe_3O_4纳米颗粒及其和中孔炭微球之间的协同作用,同时改善了阻抗匹配。(3)为在低频下获得较好的电磁波吸收效果,通过化学共沉淀法制备了 NiFe2O4/MCMSs复合材料,其在匹配厚度5mm时,在5.9 GHz处具有最大反射峰,峰值为-21 dB,小于-10 dB的带宽2.1 GHz;且涂层厚度为2-5 mm时最大反射损耗都超过了-10 dB。对比Fe_3O_4/MCMSs复合材料,其在低频下的吸收能力得到了一定程度的提升,这主要归功于镍铁氧体优良的软磁性质以及极低的共振频率,使得复合材料在较低的频率范围内出现了多个共振损耗峰。(4)探索用化学镀镍的方法对中孔炭微球进行包覆,确定了化学镀镍的前处理以及施镀过程的优化工艺条件。成功的在中孔炭微球表面包覆了一层均匀的镍磷合金镀层。镀镍后保持了中孔炭微球原本较大的介电损耗,同时磁损耗有大幅增加。在涂层厚度2-5 mm时镀镍中孔炭微球的反射损耗都超过了-10dB,在匹配厚度3mm时,其在7.4GHz处最大反射峰峰值为-20 dB,小于-10 dB的带宽为2.0 GHz(6.4-8.4 GHz)。结果表明化学镀镍的方法可以有效的提高中孔炭微球的吸波能力。
[Abstract]:With the development of electronic science and technology, whether in the field of military radar stealth or in the field of civil electromagnetic pollution protection, it is imperative to develop new "thin, light, wide and strong" absorbing materials. In this paper, a series of magnetic composite absorbing materials were prepared on the basis of mesoporous carbon microspheres prepared by spray drying with the aim of obtaining "thin, light, wide and strong" absorbing materials. The corresponding absorbing mechanism was also discussed. (1) the (MCMSs), surface area and pore volume of mesoporous carbon microspheres with particle size distribution of 1-10 渭 m were prepared by spray drying method. The specific surface area and pore volume of mesoporous carbon microspheres were up to 1221 m2 / g and 2.5 cm3/g., respectively. The pure MCMSs has a certain absorbing effect, the maximum reflection peak value can be -12 dB, and the matching thickness is 2 mm. However, the impedance matching of non-magnetic mesoporous carbon microspheres is weak, which leads to the limited effect of absorbing waves. (2) in order to improve the magnetic loss, Fe_3O_4/MCMSs composites were successfully prepared by wet impregnation and heat treatment. The composites have excellent fluidity and low density (0.24-0.39 g/cm3), the nano-particles of Fe _ 2O _ 4 are highly dispersed in the pore channels of MCMSs, and the composites still have high specific surface area (266-735 m2 / g). In the range of 2-18 GHz, the dielectric loss is dominant in the composite, and the bandwidth of -25 dB, less than -10 dB at 12.6 GHz has a bandwidth of 4.7 GHz.. Its excellent wave absorption performance is attributed to the synergistic effect between homogeneous Fe_3O_4 nanoparticles and mesoporous carbon microspheres, and the impedance matching is improved. (3) in order to obtain better electromagnetic wave absorption effect at low frequency, NiFe2O4/MCMSs composites were prepared by chemical coprecipitation method. The maximum reflection peak at 5.9 GHz was obtained when the thickness of 5mm was matched, and the peak bandwidth of -21 dB, less than -10 dB was 2.1 GHz;. And the maximum reflection loss of the coating is more than -10 dB. when the thickness of coating is 2-5 mm. Compared with Fe_3O_4/MCMSs composites, the absorption capacity of Fe_3O_4/MCMSs composites at low frequency is improved to some extent, which is mainly due to the excellent soft magnetic properties of nickel ferrite and the extremely low resonance frequency. The composite has many resonance loss peaks in the lower frequency range. (4) the electroless nickel plating method is explored to coat the mesoporous carbon microspheres, and the pretreatment of electroless nickel plating and the optimum process conditions of the plating process are determined. A uniform Ni-P alloy coating was successfully coated on the surface of mesoporous carbon microspheres. After nickel plating, the dielectric loss of mesoporous carbon microspheres was maintained, and the magnetic loss increased significantly. When the coating thickness is 2-5 mm, the reflection loss of Ni-coated mesoporous carbon microspheres exceeds -10 dB. When the thickness is matched, the maximum reflection peak at 7.4GHz is -20 dB,. Bandwidth less than -10 dB is 2.0 GHz (6.4-8.4 GHz).) The results show that the method of electroless nickel plating can effectively improve the absorbing ability of mesoporous carbon microspheres.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB332
本文编号：2338122
[Abstract]:With the development of electronic science and technology, whether in the field of military radar stealth or in the field of civil electromagnetic pollution protection, it is imperative to develop new "thin, light, wide and strong" absorbing materials. In this paper, a series of magnetic composite absorbing materials were prepared on the basis of mesoporous carbon microspheres prepared by spray drying with the aim of obtaining "thin, light, wide and strong" absorbing materials. The corresponding absorbing mechanism was also discussed. (1) the (MCMSs), surface area and pore volume of mesoporous carbon microspheres with particle size distribution of 1-10 渭 m were prepared by spray drying method. The specific surface area and pore volume of mesoporous carbon microspheres were up to 1221 m2 / g and 2.5 cm3/g., respectively. The pure MCMSs has a certain absorbing effect, the maximum reflection peak value can be -12 dB, and the matching thickness is 2 mm. However, the impedance matching of non-magnetic mesoporous carbon microspheres is weak, which leads to the limited effect of absorbing waves. (2) in order to improve the magnetic loss, Fe_3O_4/MCMSs composites were successfully prepared by wet impregnation and heat treatment. The composites have excellent fluidity and low density (0.24-0.39 g/cm3), the nano-particles of Fe _ 2O _ 4 are highly dispersed in the pore channels of MCMSs, and the composites still have high specific surface area (266-735 m2 / g). In the range of 2-18 GHz, the dielectric loss is dominant in the composite, and the bandwidth of -25 dB, less than -10 dB at 12.6 GHz has a bandwidth of 4.7 GHz.. Its excellent wave absorption performance is attributed to the synergistic effect between homogeneous Fe_3O_4 nanoparticles and mesoporous carbon microspheres, and the impedance matching is improved. (3) in order to obtain better electromagnetic wave absorption effect at low frequency, NiFe2O4/MCMSs composites were prepared by chemical coprecipitation method. The maximum reflection peak at 5.9 GHz was obtained when the thickness of 5mm was matched, and the peak bandwidth of -21 dB, less than -10 dB was 2.1 GHz;. And the maximum reflection loss of the coating is more than -10 dB. when the thickness of coating is 2-5 mm. Compared with Fe_3O_4/MCMSs composites, the absorption capacity of Fe_3O_4/MCMSs composites at low frequency is improved to some extent, which is mainly due to the excellent soft magnetic properties of nickel ferrite and the extremely low resonance frequency. The composite has many resonance loss peaks in the lower frequency range. (4) the electroless nickel plating method is explored to coat the mesoporous carbon microspheres, and the pretreatment of electroless nickel plating and the optimum process conditions of the plating process are determined. A uniform Ni-P alloy coating was successfully coated on the surface of mesoporous carbon microspheres. After nickel plating, the dielectric loss of mesoporous carbon microspheres was maintained, and the magnetic loss increased significantly. When the coating thickness is 2-5 mm, the reflection loss of Ni-coated mesoporous carbon microspheres exceeds -10 dB. When the thickness is matched, the maximum reflection peak at 7.4GHz is -20 dB,. Bandwidth less than -10 dB is 2.0 GHz (6.4-8.4 GHz).) The results show that the method of electroless nickel plating can effectively improve the absorbing ability of mesoporous carbon microspheres.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB332
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