Growth Modes Of Carbon Nanofibers Catalyzed By Copper-based Catalysts

In this paper,copper-based catalysts were prepared by microwave heating,redox,and arc-plasma methods.Using these particles as catalysts,carbon nanofibers?CNFs?were successfully synthesized.The paper focuses on three areas:1.Copper nanoparticles?CNPs?were prepared using microwave heating and redox methods respectively.CNFs were synthesized by chemical vapor deposition?CVD?.The one-step simple methods,microwave heating and redox,were used to synthesize CNPs.The products were characterized by scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,and X-ray diffraction?XRD?.The results show that the morphologies and components of the products were influenced by reaction methods,surfactants,and reaction time.CNPs are pure,crystalline spheres prepared by microwave heating using ethylene glycol?EG?,CuSO4·5H2O,N2H4·H2O,and NaOH.CNPs with different morphologies were synthesized in redox method by changing surfactants and reaction time.Truncated octahedral CNPs could be prepared using EDTA-2Na;1D nanobelts of Cu could be obtained by the adding of CTAB.CNFs were prepared using the as-synthesized CNPs.Multiple shaped CNFs could be prepared by spherical CNPs;clustered parallel CNFs could be synthesized by nanobelt-like CNPs;multi-branched CNFs could be prepared by truncated octahedral CNPs.2.CNFs were catalyzed by CNPs which were deposited on silicon substrate.CNPs were successfully prepared on silicon substrate by microwave heating.And CNFs were prepared in tubular furnace using the deposited silicon wafers as catalyst and acetylene as carbon source.A uniform layer of CNPs was synthesized on silicon wafers by activation and sensitization pre-treatment;the as-prepared CNFs were symmetric helix growth.Polishing and erosion pre-treatment could make the silicon show the active planes;a compact layer of CNPs could be obtained with oriented flaws,which play the key role of the directional grown CNFs.Symmetric coiled CNFs could be synthesized by uniform CNPs on activation and sensitization treated silicon;oriented CNFs could be prepared by copper layer after polishing and erosion pre-treatment on silicon wafer.3.CNFs were prepared by surface modified CNPs,silica-coated CNPs?Cu?SiO₂?and carbon encapsulated CNPs?Cu@C?.Cu@SiO₂ nanoparticles were synthesized by coating copper nanoparticles with a silica shell through microemulsion.The CNPs are 50 nm in diameter and the silica coating is 10 nm in thickness.After coating,copper nanoparticles were encapsulated in a silica matrix.These particles were used as catalyst for the growth of CNFs in a tubular furnace.It is found that CNFs are mirror-symmetric growth and 100 nm in diameter.During growth,the copper nanoparticles moved out of the silica.As the experiment progressed,the interplanar spacing of copper?220?increased from 0.1288 nm to 0.1306 nm indicating that?220?plane exhibited high catalytic activity.Cu@C nanoparticles were synthesized by arc-plasma.The products were uniform spheres with the diameter of 20 nm.Using these particles as catalyst,CNFs with symmetric helix growth and single helix growth were obtained.