Studing Of Preparing Activated Carbon Nanotubes And Its Applications

In this paper,the preparation of activated carbon nanotubes(CNTs)and its applications in some fields were studied.Firstly,the CNTs were activated by alkalis(NaOH,KOH,K₂CO₃ and ZnCl₂).From analyzing the products,we could see that the etching degree of alkalis-treated CNTs was more and more serious with the increase of the activating treatment temperature.The etching capabilities of different alkalis were also different at the same temperature. When the activating treatment temperature below 700℃,the etching capability was:KOH＞NaOH＞K₂CO₃＞ZnCl₂,while the temperature upon 700℃,the etching capability was:NaOH＞KOH＞K₂CO₃＞ZnCl₂.The results of specific surface areas and pore diameters distribution indicated the super alkali was KOH,activating treatment temperature was 750℃,the mass ration of alkali to CNTs was 7:1,activating treatment time was 60min.The specific surface area of KOH-activated CNTs(245.13m²/g)which prepared under super activation technics was almost 17 times bigger than the raw CNTs (13.83m²/g).The total pore volume was 0.4198cc/g,the pore diameter distribution became wide and the volume of micropore and mesopore was increase.The KOH-activated CNTs could adsorb microwave,and adsorbing peak became broader than that of raw CNTs.The band width(R＜-10dB)of the activated CNTs /Nomex honeycomb core composite is 3.4 GHz in the frequency rang of 6.48GHz to 10.88GHz,the maximum reflectivity is -22.58dB.While the reflectivity lower than - 10dB of activated CNTs/epoxide resin composite is in the frequency rang of 11.8GHz to 14.6GHz,and the maximum reflectivity is -23.99dB.The CNTs were treated by nitric acid,mixed acid(nitric acid and sulfuric acid)and phosphoric acid.Nitric acid and mixed acid could etch carbon nanotubes well because of the good oxidizability.The tubes' walls became very thin and inner diameters were enlarged clearly when the acid-treatment time of nitric acid and mixed acid respectively reached to 16h and 4h.More and more CNTs were shorted with textending the acid-treatment time.The results of the IR showed that some oxygen-functional groups had been formed. Phosphoric acid couldn't activate CNTs because of the different activation mechanism.The way of two-step activation was also used to treat CNTs.The CNTs were treated by nitric acid and mixed acid firstly,then the acid-treated CNTs were activated by KOH.The results of TEM indicated that the final products had formed several layers and channels structures which were different from the structures of CNTs just treated by single alkali or acid. The CNTs treated by different activating conditons were used as the electrode of button capacitor.The specific capacitances showed that the best mass ration of binder(PTFE)was 10%.The specific capacitances of CNTs treated by nitric acid for 10h and mixed acid for 2h are 49.38F/g and 46.7 F/g. The specific capacitances of CNTs respectively treated by NaOH,K₂CO₃, KOH at 750℃with the mass ratio of 7:1(alkalis to CNTs)are higher than that of raw CNTs(7.2 F/g),especially the KOH-treated CNTs,which increase to 59.62 F/g.The CNTs were successfully filled and coated with Fe or Fe₃O₄ by the method of self-decomposition of Iron pentacarbonyl.The appropriate ration of CNTs to Iron pentacarbonyl was 1g:20ml.TEM photographs showed the Fe or Fe₃O₄ particles in the inner diameters and surface of CNTs were homogeneous.Fe or Fe₃O₄-filled/coated CNTs have certain magnetic property and the ability of magnetic hysteresis loss,they could be the good microwave adsorbing materials because they not only have the dielectric loss but also have magnetic loss.