Purification of Catalytic Grown MWNTs by Rapid Cooling Heat Treatment

摘要

In order to purify the catalytic grown MWNTs, a new method using rapid cooling heat treatment was tried out. The CNTs heated at 900 deg C had been quenched with solid CO_2 coolant, then 30 percent HNO_3 refluxing treatment was carried out for 1hour. 30 percent HNO_3 refluxing treated CNTs for 8hours and 35 percent HCl washing treatment + 30 percent HNO_3 refluxing treated CNTs for 4hours were also prepared, respectively. The morphology and purity were estimated by the means of TEM observation, powder XRD, EDX, and ICP analysis. The investigation of BET surface area and pore characteristics were conducted also by N_2 adsorption at 77 K. From the results of experiments, it was found that the purity of 99.7 wt. percent MWNTs could be obtained by rapid cooling associated method. In addition, the BET surface area of rapid cooling treated MWNTs increased significantly. It was assumed that rapid cooling treatment promoted the development of mesopores not only by the opening of MWNTs tip but also by the bursting of nanotubes caused by thermal shock effect.