碳纳米管磁化氢等离子体的微波吸收特性研究
发布时间：2019-05-24 18:38
【摘要】：具有中空层状结构和奇特电磁性能的碳纳米管材料的合成,为高性能微波屏蔽与吸收材料的研制开辟了新的领域。碳纳米管微波吸收复合材料,特别是碳纳米管氢等离子体吸波材料已成为当今材料物理研究领域的热点之一。本文系统探讨了碳纳米管磁化均匀氢等离子体的微波介电和衰减吸收性能,深入研究了碳纳米管磁化非均匀氢等离子体的微波吸收性能。本文研究目的是为碳纳米管磁化氢等离子体在民用微波防辐及军事隐身方面的应用提供理论指导。碳纳米管的分子结构、孔隙结构和比表面积、材料吸波机理、吸波材料的发展方向、碳纳米管的吸附储氢机理和吸附储氢性能进行了系统论述。根据磁离子理论和W.K.B半经典近似法,推导了外加静磁场方向和微波传播方向之间的夹角θ为任一值时,碳纳米管薄膜磁化均匀氢等离子体的复电容率和微波衰减系数公式。数值模拟结果表明:在低频微波段,复电容率的实部和虚部均随θ的增加而增大,但是虚部变化更快;增大外磁场的磁感应强度能增加材料对微波特别是4~5GHz附近低频段微波的介电吸收;当入射微波频率ν小于4.18 GHz时,对于每一个频率的入射波,在θ等于π/2的两侧,均有两个对称吸收峰出现;随着入射波频率的增加,吸收峰向θ等于π/2的点靠近;存在一个约等于4.18 GHz的拐点频率,在该频率以下,衰减吸收随ν的增大而增加,超过其拐点频率时,衰减吸收系数随ν的增加而急剧减小;若ν大于4.28 GHz,则没有吸收峰出现。根据耗散介质中电磁波传播理论,推导了碳纳米管磁化非均匀氢等离子体的微波吸收系数。理论研究表明:自由电子数密度的变化对微波吸收有很大的影响。当外磁场与入射微波方向间的夹角为0时,材料的微波吸收系数随等离子体自由电子密度的增加均近似线性增大。若外磁场与入射微波传播方向不平行,则存在一突变点,随自由电子密度稍微增加,微波吸收系数发生阶跃式突变;当入射微波的频率增大时,突变点所对应的自由电子密度增加,其微波吸收系数的突变增量也随之增加。
[Abstract]:The synthesis of carbon nanotube materials with hollow layered structure and strange electromagnetic properties has opened up a new field for the development of high performance microwave shielding and absorption materials. Carbon nanotube microwave absorption composites, especially carbon nanotube hydrogen plasma absorbing materials, have become one of the hotspots in the field of material physics. In this paper, the microwave dielectric and attenuated absorption properties of carbon nanotube magnetized uniform hydrogen plasma are systematically discussed, and the microwave absorption properties of carbon nanotube magnetized non-uniform hydrogen plasma are deeply studied. The purpose of this paper is to provide theoretical guidance for the application of carbon nanotube magnetized hydrogen plasma in civil microwave radiation prevention and military stealth. The molecular structure, pore structure and specific surface area of carbon nanotubes, the absorbing mechanism of materials, the development direction of absorbing materials, the adsorption hydrogen storage mechanism and adsorption hydrogen storage properties of carbon nanotubes are systematically discussed. According to the magnetic ion theory and W.K.B semiclassical approximation method, it is deduced that when the angle theta between the direction of applied static magnetic field and the direction of microwave propagation is any value, Formula of complex capacitance and microwave attenuation coefficient of magnetized uniform hydrogen plasma in carbon nanotube thin films. The numerical simulation results show that in the low frequency microband, the real part and the imaginary part of the complex capacitance increase with the increase of theta, but the imaginary part changes faster. Increasing the magnetic induction intensity of the external magnetic field can increase the dielectric absorption of the microwave, especially the low frequency microwave near 4~5GHz. When the incident microwave frequency v is less than 4.18 GHz, for each frequency, there are two symmetric absorption peaks on both sides of each frequency, and with the increase of incident wave frequency, the absorption peak is close to the point where theta is equal to 蟺 / 2. There is an inflection point frequency equal to 4.18 GHz. Below this frequency, the attenuation absorption increases with the increase of v, and the attenuation absorption coefficient decreases sharply with the increase of v when the inflection point frequency is exceeded. If v is more than 4.28 GHz, there is no absorption peak. According to the theory of electromagnetic wave propagation in dissipative medium, the microwave absorption coefficient of magnetized non-uniform hydrogen plasma in carbon nanotubes is derived. The theoretical study shows that the change of free electron number density has a great influence on microwave absorption. When the angle between the external magnetic field and the incident microwave direction is 0, the microwave absorption coefficient of the material increases approximately linearly with the increase of plasma free electron density. If the external magnetic field is not parallel to the direction of incident microwave propagation, there is a sudden change point. With the increase of free electron density, the microwave absorption coefficient changes step by step. When the frequency of incident microwave increases, the density of free electrons corresponding to the mutation point increases, and the sudden change increment of microwave absorption coefficient also increases.
【学位授予单位】：南华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1
[Abstract]:The synthesis of carbon nanotube materials with hollow layered structure and strange electromagnetic properties has opened up a new field for the development of high performance microwave shielding and absorption materials. Carbon nanotube microwave absorption composites, especially carbon nanotube hydrogen plasma absorbing materials, have become one of the hotspots in the field of material physics. In this paper, the microwave dielectric and attenuated absorption properties of carbon nanotube magnetized uniform hydrogen plasma are systematically discussed, and the microwave absorption properties of carbon nanotube magnetized non-uniform hydrogen plasma are deeply studied. The purpose of this paper is to provide theoretical guidance for the application of carbon nanotube magnetized hydrogen plasma in civil microwave radiation prevention and military stealth. The molecular structure, pore structure and specific surface area of carbon nanotubes, the absorbing mechanism of materials, the development direction of absorbing materials, the adsorption hydrogen storage mechanism and adsorption hydrogen storage properties of carbon nanotubes are systematically discussed. According to the magnetic ion theory and W.K.B semiclassical approximation method, it is deduced that when the angle theta between the direction of applied static magnetic field and the direction of microwave propagation is any value, Formula of complex capacitance and microwave attenuation coefficient of magnetized uniform hydrogen plasma in carbon nanotube thin films. The numerical simulation results show that in the low frequency microband, the real part and the imaginary part of the complex capacitance increase with the increase of theta, but the imaginary part changes faster. Increasing the magnetic induction intensity of the external magnetic field can increase the dielectric absorption of the microwave, especially the low frequency microwave near 4~5GHz. When the incident microwave frequency v is less than 4.18 GHz, for each frequency, there are two symmetric absorption peaks on both sides of each frequency, and with the increase of incident wave frequency, the absorption peak is close to the point where theta is equal to 蟺 / 2. There is an inflection point frequency equal to 4.18 GHz. Below this frequency, the attenuation absorption increases with the increase of v, and the attenuation absorption coefficient decreases sharply with the increase of v when the inflection point frequency is exceeded. If v is more than 4.28 GHz, there is no absorption peak. According to the theory of electromagnetic wave propagation in dissipative medium, the microwave absorption coefficient of magnetized non-uniform hydrogen plasma in carbon nanotubes is derived. The theoretical study shows that the change of free electron number density has a great influence on microwave absorption. When the angle between the external magnetic field and the incident microwave direction is 0, the microwave absorption coefficient of the material increases approximately linearly with the increase of plasma free electron density. If the external magnetic field is not parallel to the direction of incident microwave propagation, there is a sudden change point. With the increase of free electron density, the microwave absorption coefficient changes step by step. When the frequency of incident microwave increases, the density of free electrons corresponding to the mutation point increases, and the sudden change increment of microwave absorption coefficient also increases.
【学位授予单位】：南华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1
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