Singh Manoj K, Titus E, Tyagi Pawan K, Palnitkar Umesh, Misra D S, Roy Mainak, Dua A K, Cojocaru C S, Le Normand F
Physics Department, Indian Institute of Technology, Bombay Mumbai-400 076, India.
J Nanosci Nanotechnol. 2003 Feb-Apr;3(1-2):165-70. doi: 10.1166/jnn.2003.200.
Multiwalled carbon nanotubes are grown by microwave plasma chemical vapor deposition with CH4 and H2 as precursor gases. Ni and Ni/Pt electroplated layers are used as catalysts for the synthesis of the tubes. We observe that a very efficient filling of the tubes takes place with Ni. In some cases Ni/Pt filling is also observed inside the tubes. High-resolution transmission electron microscopy (HRTEM) studies, coupled with energy-dispersive X-ray analyses of the tubes, indicate Ni nanorods with a highly symmetrical cylindrical structure. The diameter of the cylindrical nanorods is on the order of 40 nm, and their length is 660 nm. The nano area diffraction pattern of the nanorods reveals the cubic structure of nickel, and electron diffraction spots corresponding to (111), (200), (220) planes are evident. The lattice constant of Ni measured from the diffraction spots was found to be 0.347 +/- 0.0013 nm. This should be compared with 0.352 nm, the value of "a" in bulk Ni. The decrease in the lattice constant may be due to the strain experienced inside the tubes. Raman spectroscopy shows the typical signature of the tangential breathing mode present in the tubes at 1580 cm-1 that shifts to a new position when the C12 is replaced by 13C. The shift, however, is too small and is difficult to explain on the basis of mass difference. HRTEM experiments indicate the presence of Ni3C in the samples dominantly in the interfacial region.
多壁碳纳米管通过以CH4和H2作为前驱体气体的微波等离子体化学气相沉积法生长。镀Ni和Ni/Pt层用作合成碳纳米管的催化剂。我们观察到，镍能非常有效地填充到碳纳米管中。在某些情况下，管内也观察到Ni/Pt填充。高分辨率透射电子显微镜（HRTEM）研究以及对碳纳米管的能量色散X射线分析表明，镍纳米棒具有高度对称的圆柱结构。圆柱纳米棒的直径约为40nm，长度为660nm。纳米棒的纳米区域衍射图谱揭示了镍的立方结构，对应于（111）、（200）、（220）晶面的电子衍射斑点很明显。从衍射斑点测得的Ni的晶格常数为0.347±0.0013nm。这应与块状Ni中“a”的值0.352nm进行比较。晶格常数的减小可能是由于管内所经历的应变。拉曼光谱显示，碳纳米管中存在的切向呼吸模式在1580cm-1处有典型特征，当C12被13C取代时，该特征会移至新位置。然而，这种位移太小，难以基于质量差异来解释。HRTEM实验表明，样品中主要在界面区域存在Ni3C。
