Since their discovery 1, carbon nanotubes (CNTs) have attracted much attention from scientists in the field of materials, chemistry and physics because of their many attractive properties 2-4. Accordingly, a variety of synthesis methods have been developed. One of the main methods for the synthesis of multiwalled carbon nanotubes (MWNTs) is the catalytic decomposition of hydrocarbon gases with the aid of highly dispersed transition metal elements such as Fe, Co and Ni supported by many kinds of substrates 5. However, both active metal particles and supports remain in the synthesized products, and have to be eliminated by oxidation methods before application. Oxidation treatment not only removes impurity, but also affects the structure and properties of CNTs. It is known that MWNTs are themselves good catalyst support materials 6,7. When pure Ni particles supported by MWNTs are used as the catalyst in the decomposition of hydrocarbon gas, however, most products are nanofibers due to the growing tendency of Ni particles at high temperature 8. So stabilizing the active phase particles is very important when using MWNTs as support material.
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