Coal-based Nano Onion-like Fullerenes Synthesis

As a member of the fullerene family, nano onion-like fullerenes are excepted to have extensive promising application in high-performance wearable materials, superconductive materials, communicational materials, biomedical materials and so on because of their unique molecular structure. Obviously, the exploitation of property and application of nano onion-like fullerenes are based on their synthesis with large quantities at low costs. However, there are a lot of problems in their preparation (e.g. high energy consumption, high cost, low yield and so on), which make the study of nano onion-like fullerenes develop slowly in structure and property characterization, modification, function and application.In this paper, we used radio frequency, which operates at low temperatures and low energy consumption, for synthesizing nano onion-like fullerenes from coal by optimizing preparation parameters. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) were used to characterize and analyze the morphologies and microstructures of the products. The results revealed that both Zhungeer coal+10%graphite andZhungeer coal could yield nano onion-like fullerenes with large quantities. It was indicated that nano onion-like fullerenes synthesized from coal+graphite exhibited higher degree of graphitization, more regular morphologies, smoother and cleaner surfaces, but coal-derived nano onion-like fullerenes showed relatively low degree of graphitization and wavy graphite sheets. Effects of pressure on the formation of nano onion-like fullerenes were also discussed. Results revealed that nano onion-like fullerenes were easier to grow under the pressure of 30Pa. The used Fengfeng coal, which was similar with Zhungeer coal in composition and properties, could also synthesize highly graphitized nano onion-like fullerenes with high purity. There were some differences between the products from the two coals in structure. Nano onion-like fullerenes from Fengfeng coal displayed larger size and more graphene shells.Formation mechanism of coal-based nano onion-like fullerenes was discussed in this works. Compared with graphite, the relatively weak links between the macromolecular structures of coal make coal-based fullerenes preparation more efficient. The bonds in coal are not necessary to be destroyed completely during fullerenes growth. It was believed that some elements or their compounds in the coal sample probably acted as the catalysts of nano onion-like fullerenes growth. They had great influence on the yields and qualities of nano onion-like fullerenes.