Investigation On The Microwave Absorption Properties Of Magnetized Hydrogen Plasma In Carbon Nanotubes

Carbon nanotubes(CNTs) materials, with both hollow structure and singular electromagnetic properties, have been synthesized by researchers, and create a new field for the preparation of excellent microwave shielding and absorbing materials. The compound material containing CNTs, especially hydrogen plasma in CNTs applied to microwave absorption, have been a research hot spot in the field of material physics. In this dissertation, the dielectric and attenuation properties of magnetized uniform hydrogen plasma in CNTs in microwave frequency range are studied systematically. Further, the microwave absorption properties of magnetized nonuniform hydrogen plasma in CNTs are investigated in detail.The objective of this investigation is to supply theoretical guidance for magnetized hydrogen plasma in CNTs applied to both civilian microwave radiation protection and military stealth.First of all, molecular and pore structure characteristics as well as specific surface area of CNTs, wave-absorbing mechanism of materials, development trend of wave-absorbing materials research, the mechanisms and properties of hydrogen adsorption of CNTs are reviewed systematically.Using magneto-ionic theory and W.K.B approximation, the complex permittivity and microwave attenuation coefficient of magnetized uniform hydrogen plasma in CNTs film are deduced at an arbitrary angle of incident wave propagation with respect to the external static background magnetic field. The numerical results show that when θ increases, the real part and imaginary part of the complex permittivity increase in low-frequency microwave region, the imaginary part is much more sensitive to the change of θ than the real part. The increases of the magnetic induction intensity of the static background magnetic field can effectively improve microwave(especially microwave in low-frequency region of 4 to 5GHz) dielectric absorption property of hydrogen plasma in carbon nanotubes. When incident microwave frequency ν<4.18 GHz, two symmetric attenuation absorption peaks relative to π/2 are observed for each incident microwave frequency. Moreover, the attenuation absorption peaks approach π/2 as ν increases. There is an inflexion frequency of about 4.18 GHz. The attenuation coefficient has a positive correlation with the incident microwave frequency before the inflexion frequency but the attenuation coefficient dependence reverse after the inflexion. For ν>4.28 GHz, no attenuation absorption peak is found.The microwave absorption coefficient of magnetized nonuniform hydrogen plasma in CNTs are deduced using theory of electromagnetic wave propagation in dissipative medium. Theoretical results show that the change of free electron density has important influence on the microwave absorption of the sample. When the external magnetic field is parallel to electromagnetic wave propagation direction, the microwave absorption coefficient increases linearly with free electron density. Otherwise, a discontinuity point can be seen, the microwave absorption coefficient changes greatly with the minimal increase of f r e e e l e c t r o n de ns i t y. Th e fre e e l e c t r o n d e n s i t y c o r r e s p o n d i n g t o t h e discontinuity point and the discontinuity increment of the microwave absorption coefficient increase with the incident microwave frequency.