Qin Yong, Jiang Xin, Cui Zuolin
Institut für Werkstofftechnik, Universität Siegen, Paul-Bonartz-Strasse 9, 57068 Siegen, Germany.
J Phys Chem B. 2005 Nov 24;109(46):21749-54. doi: 10.1021/jp054412b.
A new type of amorphous helical carbon nanofibers has been synthesized using copper nanocatalysts and an acetylene gas source at atmospheric pressure. The nanofibers are grown at 468 K, which is the lowest temperature by ordinary metal-catalyzed thermal chemical vapor deposition of hydrocarbon, and exhibit a symmetric growth mode in the form of twin helices. IR, XRD, Raman, and C/H molar ratio analyses reveal a polymer-like structure with a weak trans-polyacetylene feature. The nanofibers are a mixture of solid polymers and a small amount of carbon. A reaction mechanism has been proposed on the basis of the previous studies of acetylene adsorption, desorption properties, and surface reactions on copper (111), (110), and (001) planes under ultrahigh-vacuum (UHV) conditions as well as the results obtained in our study. The reaction mechanism of acetylene on copper single-crystal surfaces under UHV conditions indeed reflects the reaction mechanism under practical catalytic conditions at atmospheric pressure. The nanofibers grow mainly via acetylene coupling to solid polymers on copper nanocrystal surfaces. Acetylene also couples to yield small amounts of liquid oligomers and gaseous products, and undergoes slight carbon deposition during the fiber growth.
利用铜纳米催化剂和乙炔气体源在常压下合成了一种新型非晶态螺旋碳纳米纤维。纳米纤维在468K下生长，这是通过普通金属催化的烃类热化学气相沉积法的最低温度，并且呈现出双螺旋形式的对称生长模式。红外光谱、X射线衍射、拉曼光谱和碳/氢摩尔比分析揭示了一种具有弱反式聚乙炔特征的类聚合物结构。纳米纤维是固体聚合物和少量碳的混合物。基于先前在超高真空（UHV）条件下对铜（111）、（110）和（001）平面上乙炔吸附、脱附特性及表面反应的研究以及我们研究获得的结果，提出了一种反应机理。在超高真空条件下乙炔在铜单晶表面的反应机理确实反映了常压下实际催化条件下的反应机理。纳米纤维主要通过乙炔在铜纳米晶体表面偶联形成固体聚合物而生长。乙炔也会偶联生成少量液态低聚物和气态产物，并且在纤维生长过程中会发生轻微的碳沉积。
