Many investigations have been made to the carbon nanotube (CNT)/pure silica (SiO2) composites for their attractive properties. Our primary work demonstrates the decrease of reflection at interface and the improvement of microwave absorbing efficiency in a four-layer composite, which was composed of a pure SiO2 layer, two absorbing layers of CNT/SiO2 with 2.5 and 5 wt% CNTs respectively and a last layer of (carbon fiber) Cf/SiO2 as a back reflection layer. In this paper, we tried to increase the numbers and CNT content of the absorbing layers and add another reflection layer to further improve the absorbing efficiency. For this reason, a microwave absorbing material with laminated structure was fabricated by one-step hot-pressed sintering. The new composite has an upper face layer of pure SiO2, four gradient layers of CNT/SiO2 with 2.5, 5, 7.5 and 10 wt% CNTs respectively and two Cf/SiO2 layers, whose Cf directions perpendicular to each other. The results of attenuation test showed that the laminated composite had an improved microwave absorbing efficiency in X-band compared with the as-mentioned four-layer composite. Furthermore, the result of the thermal treatment to the four-layer composite at 400oC for 10 hours proved a good thermal stability of the CNT/Cf/SiO2 system.
Journal: TechConnect Briefs
Volume: 3, Nanotechnology 2009: Biofuels, Renewable Energy, Coatings, Fluidics and Compact Modeling
Published: May 3, 2009
Pages: 485 - 488
Industry sector: Advanced Materials & Manufacturing
Topic: Carbon Nano Structures & Devices