Efficient production of carbon nanotubes using camphor as a carbon source

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Last year, using camphor as a carbon source and ferrocene as an iron source, we synthesized attractive arrays of vertically aligned CNTs on silicon substrates. That showed excellent field emission properties.On the other hand, using iron acetate and cobalt acetate as the catalyst source and zeolite powder as the catalyst support, we succeeded in growing MWCNTs at a temperature as low as 550-C at atmospheric pressure. However, the iron acetate is an extremely expensive material, not affordable for mass production of CNTs. Hence this year we focused on finding an economical alternative of iron catalyst and optimizing the catalyst concentration and CVD temperature. Out of various iron compounds investigated, we found that iron nitrate is an extremely cheap but equally effective source of iron catalyst. We successfully optimized the relative concentrations of camphor, iron-cobalt and zeolite in the reactor to achieve an exceptionally high growth of MWCNTs at 650-C at atmospheric pressure. A simple CVD of 12g camphor over Fe-Co-impregnated zeolite powder at 650-C for 30 minutes yields 6g MWCNTs of diameter 10-15nm with an as-grown purity of 88%. Owing to the enormous CNT growth, the zeolite bed inflates by 1000wt% and 10000vol%. Camphor-to-CNT production efficiency is 50% while net carbon-to-CNT conversion efficiency is 61%. These figures are incomparably higher than that of any CNT precursor by any method. Hence we call it gigas growth.