Carbon nanotubes ball-milling treatment

Chen and co-workers [14] have produced carbon nanotubes using HEBM. They used graphite as precursor and milled it for about 150 h at ambient temperature, followed by a heat treatment at 1,400 °C for 6 h in a nitrogen atmosphere. The outer diameter of the resulting material was 20 nm. The main contaminants found in these carbon nanotubes were iron and chromium originated from the balls and the inner wall of the steel container. 

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