Preparation And Characterization Of Carbon Nanofiber Films

As a research focus in the modern society and science for a long time,nano-materials are the most typical and the most representative materials in the newera. Carbon nanofibers (CNFs) play an important role in nano science and nanotechnology. CNFs exhibit unique properties such as high strength, high specific surfacearea, good field emission properties and dielectric performance due to their uniquestructures. CNFs have a broad application prospect in composite materials,electrochemical probes, catalyst supports and field emission devices.In this paper, carbon nanofiber films were synthesized by chemical vapordeposition (CVD) on copper substrate pre-treated respectively by hydrothermal andoxalic acid at a low temperature, using acetylene as carbon source. The structures andmorphologies of the obtained products were characterized by scanning electronmicroscope (SEM) and X-ray diffraction (XRD). The influences of the CVDconditions and the substrate pretreatment conditions on the structures and morphologyof the products were researched. The hydrophobic performance and the attachment ofthe carbon nanofiber films were also investigated. The growth mechanism of thecarbon nanofiber films in this method was studied.The results show that the great mass of straight carbon nanofibers and a smallpart of helical carbon nanofibers can be synthesized by CVD on the copper substratesoxidized by hydrothermal method or pretreated in oxalic acid solution. Straight carbonnanofibers with uniform diameters can be synthesized on the copper substratespre-treated by hydrothermal method. The catalyst particles on the copper substratesurfaces pretreated in different hydrothermal conditions are much different, which leadto the different morphologies of the obtained carbon nanofibers. Copper nano particlesare the catalysts in the reaction. A uniform CNF films with a thickness of20-30μm can be synthesized on the copper substrates pre-treated by oxalic acid solution at350oC. The diameters of the synthesized CNFs are300-400nm.Further studies revealed that it is unfavorable to the growth of carbon nanofiberswith too high concentration of hydrogen peroxide in hydrothermal reaction or too longtime corrosion of copper substrate in oxalic acid solution. Both chemical vapordeposition reaction time and temperature have obvious effects on the growth andmorphology of carbon nanofiber films.In the process of copper substrate pretreatment, surfactant is unfavorable to thegrowth of carbon nanofibers. The reasons were deeply studied and discussed in thispaper.In addition, the studies reveal that the yield of carbon nanofibers can be increasedwith hydrogen reduction of the pretreated copper substrate. The CNF films producedon the copper substrates pretreated in oxalic acid solution exhibit excellenthydrophobic property and fine attachment with the substrates.