SYNTHESIS OF HIGH PURITY CARBON NANOTUBES FROM COAL BY TWICE ARC-DISCHARGE METHODS

摘要

Carbon nanotubes have drawn many scientists attention throughout the world for its unique structure and potential application since it has been discovered first by S.Iijima[1]. But nowadays arc-discharge methods and chemical vapor deposition (CVD) were two main synthetic methods. As a pioneer method, arc-discharge had many advantages, such as simple equipment, better graphitized product, less defect etc. While carbon nanotubes synthesized by CVD methods had many lattice defect and most multi-walled carbon nanotubes (MWNT)[2], although the carbon source is abundant. The cost of nanotubes arises from several aspects, the cost of the source materials, production processes, level of yield, and process of purification. The cost of raw materials will become more significant when nanotubes are required in industrial scales in the future [3]. So scientist developed many valuable methods to reduce synthesis cost. One of which was to select cheap raw material, the use of coal as carbon source to make nano-materials started in 1990s. And now many important conclusions have been obtained[4-9]. But the methods used coal as carbon source now faced many problems, such as the coal-derived carbon nnaotubes is poorer than graphite-derived carbon nanotubes not only in quality but also quantity, which restricted it from industrializing. All of these can be attributed to complicated structure of coal. Now how to solve such a problem: increase the yield and purity of coal-derived carbon nanotubes?