镀镍碳纳米管的微波吸收性能研究

用竖式炉流动法制备了碳纳米管，碳纳米管的外径40nm～70nm，内径7nm～10nm，长度50μm～1000μm，呈直线型，用化学镀法在碳纳米管表面镀上了一层均匀的金属镍。碳纳米管吸波涂层在厚度为0.97mm时，在8GHz～18GHz，最大吸收峰在11.4GHz(R=-22.89dB)，R<-10dB的频宽为3.0Hz，R<-5dB的频宽为4.7GHz。镀镍碳纳米管吸波涂层在相同厚度下，最大吸收峰在14GHz(R=-11.85dB)，R<-10dB的频宽为2.23Hz，R<-5dB的频宽为4.6GHz。碳纳米管表面镀镍后虽然吸收峰值变小，但吸收峰有宽化的趋势，这种趋势对提高材料的吸波性能是有利的。碳纳米管作为偶极子在电磁场的作用下，会产生耗散电流，在周围基体作用下，耗散电流被衰减，从而雷达波能量被转换为其它形式的能量。

STUDY ON THE MICROWAVE ABSORBING PROPERTY OF COMPOSITE MATERIAL CONTAINING CARBON NANOTUBES WITH NI COATING

Carbon nanotubes were prepared by catalytic decomposition ofbenzene using a floating transition method. The carbon nanotubes are straight with diameter 40 nm～70 nm, internal diameter 7 nm～10 nm and length 50 μm～1 000 μm. The Ni coating on the carbon nanotubes was deposited by electroless deposition technique. The maximum absorbing peak of the microwave absorbing composite material containing the carbon nanotubes is 22.89 dB at 11.40 GHz. The maximum absorbing peak of the microwave absorbing composite material containing carbon nanotubes with Ni coating is 11.85 dB at 14.0 GHz. The absorbing peak of the composite material is moved from 11.40 GHz to 14.0 GHz, and absorbing peak becomes broader. The band width (R<-10 dB) of the composites containing carbon nanotubes with thickness of 0.97 mm is 3.0 GHz, band width (R<-5 dB) is 4.7 dB at the frequency range of 8 GHz～18 GHz. The band width (R<-10 dB) of the composites containing carbon nanotubes with Ni coating with thickness of 0.97 mm is 2.3 GHz, band width (R<-5 dB) is 4.6 dB at the frequency range of 8 GHz～18 GHz. The carbon nanotubes or carbon nanotubes with Ni coating are used as resonators to absorb the microwave. In the microwave absorbing material containing an electromagnetic loss substance and resonator, the resonator as an electron couple can generate an inductive current in the electromagnetic field. The induced current then causes a loss current and energy dissipation. In the electromagnetic loss substance, the electromagnetic wave energy is changed into heat energy. This is the main mechanism in microwave attenuation. So by controlling the composition, loss factor and impedance, performance of the microwave absorbing material can be optimized for a single narrow band frequency, multiple frequencies, or over a broad frequency spectrum.