Preparation And Properties Of Carbon Nanomaterials Based On Biomaterials

Carbon nanomaterials are currently the focus of research around the world because of their unique microstructures and extraordinary properties as well as great potential in many fields of science and technology. In this thesis the possibility for preparing carbon nanomaterials based on natural biomaterials has been explored, and the morphology, structure and properties of the obtained carbon nanomaterials are systematically studied, on the basis of which the growth mechanism of carbon nanometerials are addressed.A novel approach for preparing carbon encapsulated nanomaterials with apoferritin as the starting nano-sized reactor has been developed, in which apoferritin molecules, a kind of biomaterial with hollow cages, is used to trap the precursors of metals to be encapsulated. The results show that the nano-sized metal particles can be effectively encapsulated inside the carbon shells resulting from the pyrolysis decomposition of protein molecules under mild and controllable conditions. Carbon encapsulated Mn and Co nanomaterials are prepared by carbonization under vacuum conditions or in flowing hydrogen, respectively. The mechanisms of mineralization and carbonization are discussed in terms of the structure and properties of protein.A practical and efficient route is developed for the first time for making carbon encapsulated metal nanomaterials with amylase (starch and cellulose) as the starting material. It has been found that Fe particles can be effectively encapsulated inside carbon shells by carbonizing mixtures of starch and iron oxide in flowing hydrogen. Following the above route, carbon encapsulated bimetallic particles are also synthesized successfully. The preparation of carbon encapsulated nanomaterials with cellulose as the starting material is also successful, which is attributed to the similarity in composition and structure of starch and cellulose. The results demonstrate that both starch and cellulose are one of the ideal carbon precursors for preparing carbon encapsulated nanomaterials. The products are characterized using a number of techniques including TEM, HRTEM, SEM, EDX, XRD, Raman, IR and UV-vis. It has been found that carbon encapsulated nanomaterials have an ideal core-shell structure with a narrow size distribution. In addition, preliminary results show that carbon nanoballs with a narrow size distribution can also be made from starch via arc discharge method. The mechanism involved in the growth process of carbon encapsulated nanomaterials is also addressed, in which it is believed that two steps, i.e. the thermolysis of precursor and the catalytic graphitization of carbonized materials, are involved.The possibility of making carbon nanotubes (CNTs) from different carbon-containing sources via chemical vapor deposition method is also explored, in which biomaterials ororganic substance are used as catalysts. With ferritin as catalyst, CNTs are prepared for the first time from coal gas, which leads one to believe that ferritin is an ideal catalyst precursor for controlling growth of carbon nanotubes and coal gas is one ideal carbon source for CNTs. Under the optimized conditions, it is also possible to prepare aligned CNTs. With organic sulfur compound as carbon source, Y-junction CNTs are obtained, of which the growth mechanism is briefly discussed. The results show that sulfur may play a key role for the growth of junctions. Furthermore, single walled CNTs are synthesized from coal gas when ferrocene is used as catalyst, indicating that catalyst has an important effect on morphologies and structures of CNTs. In addition, the potential of CNTs in the field of electrochemistry is explored, of which the preliminary results lead one to believe that CNTs is an ideal electrode materials for superocapacitors.