Efficient production of carbon nanotubes using camphor as a carbon source

去年，我们用樟脑作为碳源，二茂铁作为铁源，在硅衬底上合成了引人注目的垂直排列的碳纳米管阵列。另一方面，以乙酸铁和乙酸钴为催化剂源，沸石粉为催化剂载体，在常压下，在550 ℃的低温下成功地生长了MWCNTs。然而，醋酸铁是一种极其昂贵的材料，对于CNT的大规模生产来说是负担不起的。因此，今年我们专注于寻找铁催化剂的经济替代品，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非常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，以实现在650-C和大气压下MWCNTs的异常高的生长。将12 g樟脑在Fe-Co浸渍的沸石粉上在650-C下简单CVD 30分钟，得到6 g直径为10- 15 nm的MWCNTs，其生长纯度为88%。由于CNT的大量生长，沸石床膨胀了1000wt%和10000 vol %。樟脑到CNT的生产效率为50%，而碳到CNT的净转化效率为61%。这些数字比通过任何方法得到的任何CNT前体都高得多。我们称之为Gigas Growth。

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.