Efficient production of carbon nanotubes using camphor as a carbon source

去年，我们以樟脑为碳源，二茂铁为铁源，在硅衬底上合成了垂直排列的碳纳米管。表现出优异的场发射性能。另一方面，我们以醋酸铁和醋酸钴为催化剂源，沸石粉为催化剂载体，在低至550℃的常压下成功生长出了MWCNTs。然而，醋酸铁是一种非常昂贵的材料，不适合大规模生产碳纳米管。因此，今年我们致力于寻找一种经济的铁催化剂替代品，并优化催化剂浓度和CVD温度。在研究的各种铁化合物中，我们发现硝酸铁是一种极其便宜但同样有效的铁催化剂来源。我们成功地优化了反应器中樟脑、铁钴和沸石的相对浓度，从而在650℃的大气压下实现了MWCNTs的超高速生长。将12g樟脑置于fe - co浸染的沸石粉上，在650℃下CVD 30分钟，可制得6g直径为10-15nm的MWCNTs，其生长纯度为88%。由于碳纳米管的大量生长，沸石床膨胀了1000wt%和10000vol%。樟脑到碳纳米管的生产效率为50%，而净碳到碳纳米管的转换效率为61%。这些数字比用任何方法得到的碳纳米管前体都要高得多。因此我们称之为千兆级增长。

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.