Bulk production of multi-wall carbon nanotube bundles on sol–gel prepared catalyst

Synthesis of aligned and length-controlled carbon nanotubes by chemical vapor deposition

“…a-f. The molar ratios of Mo to Mg and Fe to Mg were from 1.0 to 1.2 and from 0.01 to 0.1 in previous works [11][12][13][14], whereas those of Mo to Mg and Fe to Mo were from 0.01 to 0.06 and from 0.04 to 0.14 in our work. In http://carbonlett.org TEM was used to measure the distribution and average diameters of CNTs.…”

“…In cases of high content of Mo in the catalyst, high temperature was needed to grow CNTs, because the melting point of Mo is higher than 2000°C. Wang et al [10] and others [11][12][13][14] carried out experiments to obtain aligned CNTs at more than 900°C with flow of methane gas; however, we could have aligned CNTs at less than 700°C with a flow of ethylene gas instead of methane gas. 3000, 1000, 500 and 300 wt% in the order shown in Figs. 5a-e.…”

“…The growth mechanism of the aligned CNTs on the iron-rich catalyst or molybdenum-poor catalyst, such as were used in our study, would be similar to that of aligned growth on a substrate such as silicon wafer. This means that the metal nanoparticles such as MgO could easily melt and then move from the inside of the ceramic supports to the surface of the ceramic supports when catalysts were synthe- short, previous works [11][12][13][14] used a catalyst with high Mo content; on the other hand, we used a catalyst with low Mo content. In cases of high content of Mo in the catalyst, high temperature was needed to grow CNTs, because the melting point of Mo is higher than 2000°C.…”

“…The powder form of short and aligned CNTs can be more easily dispersed in a composite matrix than can be normally grown CNTs. Several researchers [8][9][10][11][12][13][14] have succeeded in growing aligned CNTs powders, but there has been no fabrication of a composite with aligned CNTs. Current materials do not seem to be suitable for composites because of the use of high temperature in the CNT growth and high molybdenum contents in the catalysts.…”

Synthesis of thin-multiwalled carbon nanotubes by Fe-Mo/MgO catalyst using sol-gel method

“…Flahaut et al [13] reported the formation of (Mg, Co, Mo)O solid solutions, which showed large diameter MWCNTs (inner diameter ~9 nm) having up to 13 graphene walls due to the used of high Mo content. It has commonly been accepted that the addition of Mo within transition metals like Fe, Co, or Ni increases the carbon yield and induces large diameter MWCNTs with defective structures at the side walls [5,[13][14][15][16][17]. The realization of highly homogeneous catalyst nanoparticles with uniform size using a simple and low cost process is still a hot issue.…”