Crouse Christopher A, Maruyama Benji, Colorado Ramon, Back Tyson, Barron Andrew R
Richard E. Smalley Institute for Nanoscale Science and Technology, nano Carbon Center, and Department of Chemistry, Rice University, Houston, Texas 77005, USA.
J Am Chem Soc. 2008 Jun 25;130(25):7946-54. doi: 10.1021/ja800233b. Epub 2008 May 29.
Carbon nanotubes (CNTs) have been grown using Fe, Co, Ni, and Co/Fe spin-on-catalyst (SOC) systems, involving the metal salt dispersed with a spin-on-glass precursor. During initial growth runs (CH4/H2/900 degrees C), the CNT yield followed the order Co-SOC > Fe-SOC >> Ni-SOC. The Fe catalysts produced the longest nanotubes at the expense of a larger average CNT diameter and broader diameter distribution than the Co-SOC system. A series of Co/Fe-SOCs were prepared where as the atomic percentage of Co is increased nucleation of CNT increases but the CNT length decreases. The linear relationship between the diameter and length of CNTs grown from the Co/Fe-SOC suggests that slow growth is beneficial with respect to control over CNT diameter. After initial CNT growth, the original samples were subjected to additional growth runs. Four individual reactions were observed in the Fe-SOC and binary Co/Fe-SOC: regrowth (amplification), double growth (a second CNT growing from a previously active catalyst), CNT etching, and nucleation from initially inactive catalysts (new growth). CNT etching was observed for the mixed catalyst systems (Co/Fe-SOC) but not for either Fe-SOC or Co-SOC. During the regrowth experiments, CNTs were observed that were not present after the initial growth run (and were not as a result of amplification or double growth). Thus, catalysts, which were initially inactive toward nucleation of CNTs in the original growth run, are capable of becoming activated when placed back into the furnace and submitted to regrowth under identical conditions.
碳纳米管（CNT）已通过铁、钴、镍以及钴/铁旋涂催化剂（SOC）体系生长而成，该体系涉及与旋涂玻璃前驱体分散的金属盐。在初始生长过程中（CH4/H2/900摄氏度），碳纳米管的产量顺序为：钴-SOC＞铁-SOC＞＞镍-SOC。铁催化剂生成的纳米管最长，但与钴-SOC体系相比，其平均碳纳米管直径更大且直径分布更宽。制备了一系列钴/铁-SOC，随着钴原子百分比的增加，碳纳米管的成核增加，但碳纳米管长度减小。从钴/铁-SOC生长的碳纳米管直径与长度之间的线性关系表明，缓慢生长有利于控制碳纳米管直径。在碳纳米管初始生长后，对原始样品进行额外的生长过程。在铁-SOC和二元钴/铁-SOC中观察到四个单独的反应：再生长（放大）、双重生长（第二个碳纳米管从先前活性催化剂上生长）、碳纳米管蚀刻以及从初始无活性催化剂上成核（新生长）。在混合催化剂体系（钴/铁-SOC）中观察到了碳纳米管蚀刻，但在铁-SOC或钴-SOC中均未观察到。在再生长实验期间，观察到了在初始生长过程后不存在的碳纳米管（且不是放大或双重生长的结果）。因此，在原始生长过程中最初对碳纳米管成核无活性的催化剂，当放回炉中并在相同条件下进行再生长时能够被激活。
