Nitrogen controlled iron catalyst phase during carbon nanotube growth
Nitrogen controlled iron catalyst phase during carbon nanotube growth
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DOI：
10.1063/1.4897950
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发表时间：
2014-10-06
影响因子：
4
通讯作者：
Hofmann, Stephan
中科院分区：
文献类型：
--
作者：
Bayer, Bernhard C.;Baehtz, Carsten;Hofmann, Stephan
在催化化学气相沉积中，对活性催化剂相进行精确控制从而控制碳纳米管结构仍然具有挑战性，因为在实际合成条件下，通常会同时存在多种相互竞争的活性催化剂相。在此，我们利用原位X射线衍射法表明，在纳米管合成过程中添加氨气能够可靠地控制负载型铁催化剂颗粒的相。与氢气稀释的纳米管生长过程中出现的多分散催化剂相混合物不同，添加氮气可在预处理过程中可控地形成纯γ - Fe相，并在生长过程中形成纯Fe₃C相。我们根据三元Fe - C - N相图计算对这些发现进行了合理的解释，从而强调了预处理气体和添加气体作为控制碳纳米管生长的关键参数的应用。（C）2014美国物理联合会出版有限责任公司
Close control over the active catalyst phase and hence carbon nanotube structure remains challenging in catalytic chemical vapor deposition since multiple competing active catalyst phases typically co-exist under realistic synthesis conditions. Here, using in-situ X-ray diffractometry, we show that the phase of supported iron catalyst particles can be reliably controlled via the addition of NH3 during nanotube synthesis. Unlike polydisperse catalyst phase mixtures during H-2 diluted nanotube growth, nitrogen addition controllably leads to phase-pure gamma-Fe during pre-treatment and to phase-pure Fe3C during growth. We rationalize these findings in the context of ternary Fe-C-N phase diagram calculations and, thus, highlight the use of pre-treatment- and add-gases as a key parameter towards controlled carbon nanotube growth. (C) 2014 AIP Publishing LLC.