Yu Zhixin, Chen De, Tøtdal Bård, Holmen Anders
Department of Chemical Engineering, Norwegian University of Science and Technology, N-7491, Trondheim, Norway.
J Phys Chem B. 2005 Apr 7;109(13):6096-102. doi: 10.1021/jp0449760.
The effect of catalyst support and reactant on the yield and structure of carbon growth has been investigated in the chemical vapor deposition (CVD) process. Powder Fe and Fe/Al(2)O(3) were the catalysts studied, and CO/H(2), CO, CH(4), and C(2)H(6)/H(2) were used as gas precursors. Platelet and fishbone-tubular structures were produced on powder and supported Fe from CO/H(2), with average diameters of 115 and 45 nm and yields of 28.8 and 17.6 g of C/g of cat. in 8.5 h, respectively. Onionlike carbon was the main structure produced from pure CO on both catalysts. In contrast, from hydrocarbons the highest yield of 2.24 g of C/g of cat. was achieved on Fe/Al(2)O(3), with predominantly tubular structures produced and average tube diameters close to 21 nm. It is concluded that the reactivity and carbon nanostructures are dictated by the size and crystallographic orientation of the catalyst particles. It has been suggested that the tubular structures were grown by continuous carbon supply directly to the tube, but the fiber structures were grown in a layer-by-layer manner. Controlled synthesis of carbon nanotube, platelet nanofiber, fishbone-tubular nanofiber, and onionlike carbon with high selectivity and yield was demonstrated.
在化学气相沉积（CVD）过程中，研究了催化剂载体和反应物对碳生长的产率和结构的影响。研究的催化剂为粉末状铁和Fe/Al₂O₃，气体前驱体使用CO/H₂、CO、CH₄和C₂H₆/H₂。在粉末状铁和负载型铁上，由CO/H₂生成了片状和鱼骨状管状结构，平均直径分别为115和45 nm，在8.5小时内的产率分别为28.8和17.6 g C/g催化剂。在两种催化剂上，由纯CO生成的主要结构为洋葱状碳。相比之下，在Fe/Al₂O₃上，由烃类生成的最高产率为2.24 g C/g催化剂，主要生成管状结构，平均管径接近21 nm。得出的结论是，反应活性和碳纳米结构由催化剂颗粒的尺寸和晶体取向决定。有人提出，管状结构是通过直接向管中连续供应碳而生长的，而纤维结构是以逐层方式生长的。证明了能够以高选择性和高产率可控合成碳纳米管、片状纳米纤维、鱼骨状管状纳米纤维和洋葱状碳。
