CCVD synthesis of carbon nanotubes with W/Co–MgO catalysts

Carbon nanotubes (CNT) were synthesized from a H2–CH4 mixture with W/Co–MgO catalyst by a catalytic chemical vapour deposition (CCVD) method. Different W/Co ratios were investigated. From transmission electron microscopy observations, we observed that both the number of walls and the diameter of CNT increased with the proportion of tungsten. A promoter effect was observed as long as the proportion of tungsten was kept low and CNT with a number of walls ranging from 2 to 5 were obtained. With a higher proportion of tungsten, multi-walled carbon nanotubes (MWNT) up to 10 walls were synthesised, together with additional undesirable carbon nanofibres.