Introduction of CO_(2)is a facile way to tune the growth of vertically aligned double-or single-walled carbon nanotube(CNT)forests on wafers.In the absence of CO_(2),a double-walled CNT convexity was obtained.With increasing concentration of CO_(2),the morphologies of the forests transformed first into radial blocks,and finally into bowl-shaped forests.Furthermore,the wall number and diameter distribution of the CNTs were also modulated by varying the amount of CO_(2).With increasing CO_(2)concentration,CNTs with fewer wall number and smaller diameter were obtained.The addition of CO_(2)is speculated to generate water and serve as a weak oxidant for high quality CNT growth.It can tune the growth rate and the morphologies of the forests,prevent the formation of amorphous carbon,and reduce the wall number of the CNTs.
Liquefied petroleum gas (LPG), a cheap industrial material, is used as carbon source to produce carbon nanotube (CNT) arrays on ceramic spherical surface on a large scale in the floating catalyst process. The ceramic spheres provide huge surface area and good mobility, leading to the mass production of CNT arrays continuously. The arrays obtained from the surface are of good alignment, and the purity is as high as 97.5%. With the decrease of the growth temperature, CNTs in the array form with small-diameter of about 13 nm can be obtained. Therefore, with the industrial fuel as carbon source and the ceramic sphere as substrate, CNT arrays can easily be produced on large scale at low cost.
ZHANG Qiang HUANG JiaQi WEI Fei XU GuangHui WANG Yao QIAN WeiZhong WANG DeZheng
