Microwave Absorption Characteristics of Carbon Nanotubes

Abstract

Radar-absorption materials (RAM) have a growing and widespread applications in broadcasting and television, radar technology and microwave dark-room. In particular, in military applications, stealth weapons exhibit crucial effect in war. The research of RAM has been accelerating with the stealth technology and significant progresses have been achieved The investigations of RAM began before WarII. It has experienced a process from traditional RAM to advanced RAM represented by nano-RAM. These advanced RAM mainly include nano-metals and alloys, nano-oxides, nano-SiC, nano-ferrite, nano-graphite, nano-SiC, nano-SiN, nano conductive polymers and carbon nanotubes (CNTs) [1]. Nano RAM has light-weight, excellent compatibility and broad bandwidth, and considered as important potential RAM for industrial application. CNTs are a very important RAM. They possess high strength and toughness [2,3], excellent electrical and thermal conductivity [47].The investigations of microwave absorption of CNTs had gained a big momentum due to its potential applications in the stealth technology of aircrafts, military equipment and microwave dark-room.. Cao[8] investigated microwave absorption properties of CNTs-polyester and achieved promising results with the absorbing peak value of -14 dB and bandwidth of 10.50 GHz(R<-5dB). Sheng [9] tested the radar wave absorption properties of CNTs coated with nickel. The results show the increase of bandwidth, but the absorption peak decreases. The peak and bandwidth of the RAM of CNTs coated with nickel reach -11.85dB and 2.23 GHz(R<-10dB). Lin [10,11] investigated the microwave-absorption properties of Co-filled and Fe-fillled carbon nanotubes respectively. The results indicate that the microwaveabsorbing properties of Co-filled CNTs was improved. The maximum reflection loss is about -39.32 dB and the bandwidth corresponding to the reflection loss below -10 dB is 3.47 GHz. With increasing thickness, the maximum reflection loss shifts to lower frequency. The fe-filled CNTs also show excellent microwave absorption properties.Che[12] investigated the properties of microwave absorption and electromagnetic interference shielding of Fefilled CNTs. The results shows the microwave absorption and shielding effect was enhanced substantially. The shape of Fe filled into CNTs is largely related to the shielding effect and microwave absorption. Zhao[13] investigate the Microwave absorbing property Ni-coated and Ag nanowires filled carbon nanotubes. CNTs were coated with nickel by an electroless plating technique, CNTs were filled with Ag nanowires via a wet chemical method and epoxy was used as substrate materials.