【摘要】：具有中空層狀結構和奇特電磁性能的碳納米管材料的合成,為高性能微波屏蔽與吸收材料的研制開辟了新的領域。碳納米管微波吸收復合材料,特別是碳納米管氫等離子體吸波材料已成為當今材料物理研究領域的熱點之一。本文系統(tǒng)探討了碳納米管磁化均勻氫等離子體的微波介電和衰減吸收性能,深入研究了碳納米管磁化非均勻氫等離子體的微波吸收性能。本文研究目的是為碳納米管磁化氫等離子體在民用微波防輻及軍事隱身方面的應用提供理論指導。碳納米管的分子結構、孔隙結構和比表面積、材料吸波機理、吸波材料的發(fā)展方向、碳納米管的吸附儲氫機理和吸附儲氫性能進行了系統(tǒng)論述。根據(jù)磁離子理論和W.K.B半經(jīng)典近似法,推導了外加靜磁場方向和微波傳播方向之間的夾角θ為任一值時,碳納米管薄膜磁化均勻氫等離子體的復電容率和微波衰減系數(shù)公式。數(shù)值模擬結果表明:在低頻微波段,復電容率的實部和虛部均隨θ的增加而增大,但是虛部變化更快;增大外磁場的磁感應強度能增加材料對微波特別是4~5GHz附近低頻段微波的介電吸收;當入射微波頻率ν小于4.18 GHz時,對于每一個頻率的入射波,在θ等于π/2的兩側,均有兩個對稱吸收峰出現(xiàn);隨著入射波頻率的增加,吸收峰向θ等于π/2的點靠近;存在一個約等于4.18 GHz的拐點頻率,在該頻率以下,衰減吸收隨ν的增大而增加,超過其拐點頻率時,衰減吸收系數(shù)隨ν的增加而急劇減小;若ν大于4.28 GHz,則沒有吸收峰出現(xiàn)。根據(jù)耗散介質中電磁波傳播理論,推導了碳納米管磁化非均勻氫等離子體的微波吸收系數(shù)。理論研究表明:自由電子數(shù)密度的變化對微波吸收有很大的影響。當外磁場與入射微波方向間的夾角為0時,材料的微波吸收系數(shù)隨等離子體自由電子密度的增加均近似線性增大。若外磁場與入射微波傳播方向不平行,則存在一突變點,隨自由電子密度稍微增加,微波吸收系數(shù)發(fā)生階躍式突變;當入射微波的頻率增大時,突變點所對應的自由電子密度增加,其微波吸收系數(shù)的突變增量也隨之增加。
[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.
【學位授予單位】：南華大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TB383.1

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本文編號：2485092