Studying On Microwave Absorbing Properties Of MWNTs/EP Composites

Multi-walled carbon nanotubes (MWNTs) have a special microstructure, which makes it own unique mechanical, thermal and electrical propertites. Meanwhile, MWNTs show out the outstanding microwave absorbing properties, and overcome narrow frequency band, light mass, low absorbing intensity. MWNTs can be widely used in military and civil microwave absorbing materials. Epoxy resin, which has high tensile strength, high toughness, good insulation, and other properties, is one kind of polymer materials in industries. It is very important to study the microwave absorbing properties of MWNTs/epoxy resin composites.In this paper, according to the mechanism of microwave absorption in absorbing materials, we will prepare MWNTs/epoxy resin composites which use MWNTs as the major absorber, and epoxy resin as the base of composite materials. And then, we study their microwave absorbing properties. First, we make the samples of MWNTs purified. The effects of treating MWNTs by calcine in air, nitric acid oxidation in different concentrations and other purified methods are studied. We also study the dispersion of MWNTs in the epoxy resin. Second, the purified MWNTs in a vacuum condition are treated by the NaOH at high-temperature processing. We analyze the impacts of treating MWNTs by the different concentrations of NaOH. At last, NaOH-treated MWNTs /epoxy resin composites with different MWNTs contents have been prepared by cast molding method.The results show that the double absorbing peaks are obtained in the kind of MWNTs/epoxy resin composites with 4 mm thickness. And the wave absorbing curves have good microwave absorbing properties in the low-frequency S-band (2GHz - 4GHz).MWNTs on mechanical ball milling, air calcine, nitric acid oxidation, and other treatments can be very high purity. In the high-temperature vacuum conditions, different alkali concentration of treating MWNTs have produced different structures of the holes on MWNTs' surface. By changing the concentration of the NaOH liquid used to treat the MWNTs, at high temperature, the maximum absorbing peak, its frequency, and its band width can be adjusted. At a certain condition, the concentration is higher, the absorbing peak, its frequency, as well as its band width, become larger. The measurement results show that the volume resistivities of the NaOH-treated MWNTs/EP composites are in the range of 10~6-10~7Ω·cm, having the good anti-static-electric ability.