| As a new member of the fullerene family, carbon onions can encapsulate atom clusters, nanoparticles and metal carbides because of their unique hollow cage and concentric shells structure, which endow carbon onions some special properties. Based on these properties, many potential applications, such as source materials, high-powered and high temperature wearable materials, superconduct materials and bio-materials, have been proposed. So far, synthesis, purification and properties of carbon onions have been widely investigated all over the world. All synthesis methods developed have some shortcomings, such as high price or low production. For these reasons, the further research of their properties and applications has been hindered. This paper gave some systematic reaserch on the synthesis of carbon onions for the purpose of reducing price and increasing yield, and presented a new method, template synthesis, for preparing endohedral-metal carbon onions (EMCOs) in large quantity and high qulity.The template synthsis is a novelty synthesis method for EMCOs, which was presented by us for the first time. Template synthsis could use orgnic monomeric compound (such as styrene and acryl acid) as carbon source, form EMCOs precursors through the polymeration reaction between these monomers, and transform into real EMCOs by heat treatment at last. The microstructure of products were characterized and analyzed by field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) . The results revealed that the formation of EMCOs through pre-molding synthesis is an efficient method for producing EMCOs with a uniform size distribution and high degree of graphitization. It should be noted that the EMCOs morphology (spherical or polygonal) and size (measured as dimension of EMCOs or the number of outer shells) were very difficult to control in previous synthesis methods. However, our method is a simple important process for future applications.
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