Study On The Microwave Absorbing Property Of Carbon Nanotubes/active Carbon By Electroless Plating

In this paper, the composite materials with microwave absorbing property are studied. In the experiment, carbon nanotubes and active carbon are the substrate for electroless plating, and a series of modified processing are carried in order to produce new absorbing materials with the property of outstanding absorption performance, band absorption width, light density and quality.A series of experiments are carried on carbon nanotubes and active carbon, such as purification, oxidation, sensitization, and activation,etc. As a result, one quite ideal pretreatment method is discovered. Firstly, carbon nanotubes is grinded in a mortar. Secondly, carbon nanotubes is purified in the sodium hydroxide solution, and oxidized in the thick nitric acid solution and the Fenton reagent. The single factor experimental method is used to discover the better composition of the electroless plating solution. The composition is listed below: CoSO4·7H₂O, 25～30g/L; NaH₂PO₂·H₂O, 25～30g/L; Na₃C₆H₅O₇·2H₂O, 45⁵5g/L; NH₄Cl,25～30g/L; NH₄·H₂O,CH₃COOH, anion surface active agent, trace amount. The plating condition is: temperature: 80±2℃; the mixing speed: medium speed; the pH value: 9.80±0.50.etc.By electroless plating, cobalt/nickel is deposited respectively on the surface of carbon nanotubes and active carbon by transmission electron microscopy. The structure of carbon nanotubes doesn't change after electroless plating by infrared spectrum picture. And the complex relative permittivity (εr=ε' -jε'') and permeability (μr =μ'- jμ'') of the absorber were measured in a frequency range from 2 GHz to 18 GHz. The reflection loss (R.L.), matching thickness (d_m) and matching frequency (f_m) were calculated by the theory of the absorbing wall. When the matching thickness of canbon nanotubes is 3.5mm, the maximum reflection coefficient is about -11.28dB , the corresponding matching frequency is 17GHz. With the increase of the frequency, the value of the reflection loss transfers to lower value. When the matching thickness of canbon nanotubes with Co coating is 9mm, the maximum reflection coefficient is about ?30.92dB, the corresponding matching frequency is 10.99GHz. The bandwidth corresponding to the reflection loss below ?5 dB is more than 2.7GHz, and the reflection loss below ?10dB is more than1.4GHz. When the matching thickness of canbon nanotubes with Ni coating is 0.2mm, the maximum reflection coefficient is about ?11.40dB, the corresponding matching frequency is 15.6GHz. The reflection loss...