Growth and Characterization of Cobalt-filled Carbon Nanotubes Prepared by a Simple Catalytic Method
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Growth and Characterization of Cobalt-filled Carbon Nanotubes Prepared by a Simple Catalytic Method Xicheng Ma1, Yuanhua Cai, Xia Li, Ning Lun, Shulin Wen School of Material Science and Engineering, Characterization and Analysis Center for Materials, 1 School of Chemistry and Chemical Engineering Shandong University, Jinan 250061, PR China ABSTRACT High-quality cobalt-filled carbon nanotubes (CNTs) were prepared in situ in the decomposition of benzene over Co/silica-gel nano-scale catalysts. Unlike the previous reports, the catalysts needn’t be pre-reduced prior to the forming of Co-filled CNTs, thus the advantage of this method is that Co-filled CNTs can be produced in one step, at a relatively low cost. Transmission electron microscopy (TEM) investigation showed that the products contained abundance of CNTs and most of them were filled with metallic nanoparticles or nanorods. High-resolution TEM (HRTEM), selected area electron diffraction (SAED) patterns and energy dispersive X-ray spectroscopy (EDS) confirmed the presence of Co inside the nanotubes. The encapsulated Co was further identified always as high temperature alpha-Co phase with fcc structure, which frequently consists of twinned boundaries and stacking faults. Based on the experimental results, a possible growth mechanism of the Co-filled CNTs was proposed. INTRODUCTION Since the discovery of carbon nanotubes by Iijima [1], the materials always offer intriguing possibilities for fundamental studies of nanoscale well-defined structures and provide high potential for technological applications. Significant progresses have been made recently on the studies of mechanical, electronic transport and structural properties of individual carbon nanotubes [2-4]. On the application side, carbon nanotubes have been applied in the fabrication of various devices, for examples, scanning probes [5], biological sensors [6], electronic transistors [7] field emitting devices [8], and energy storage [9]. Filling materials into the inner hollow cavity of carbon nanotubes have brought great attention because the new filled one-dimensional structures are expected to exhibit different physical properties from those of empty nanotubes [10]. Many attempts have been made to encapsulate various materials into carbon nanotubes[11-13]. In contrast, the catalytic pyrolysis method is of great promise due to low costs, the ready availability of raw materials and simple processing setup. However, by this method, the overall yield of the encapsulated nano-materials is still rather low, the catalytic mechanism and the nature of the encapsulated materials are still not very clear, and in most cases, the control of the composition and structure of the products still pose a big challenge. In this present work, we described a study of producing Co-filled carbon nanotubes by a
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