No abstract

Carbon nanofibers were synthesized on transition metal (Fe, Co, Cu) catalysts by Chemical Vapor Deposition (CVD). The variations of thickness and surface of the fibers were investigated according to the concentration of the transition metal. In order to prepare the metal catalysts for synthesis, transition metal nitrate and copper nitrate at a weight ratio were dissolved in distilled water. The obtained catalyst precipitates were filtered and then dried for more than 24 hours at 110 degrees C. Carbon nanofibers were synthesized by using ethylene gas of carbon source by CVD after pulverization of the fully-dried catalyst precipitates. They were characterized by SEM, EDS, Raman, XRD, XPS and TG/DTA, and their specific surface area was measured by BET. The characteristics of the synthesized carbon nanofibers were greatly influenced by the concentration ratio of the metal catalysts. Especially, uniform carbon nanofibers grew when the concentration ratio of Fe and Cu was 7:3, and that of Co and Cu was 6:4. Carbon nanofibers synthesized under such concentration conditions had the best crystallizability, compared to carbon nanofibers synthesized with metal catalysts of different concentration ratios, and revealed high amorphicity as well as high specific surface area.

The carbon nanofibers (CNFs) and Si-CNFs composite were synthesized using a chemical vapor deposition (CVD) method with an iron-copper catalyst and silicon-covered Ni foam. Acetylene as a carbon source was flowed into the quartz reactor of a tubular furnace heated to 600 degrees C. This temperature was maintained for 10 min to synthesize the CNFs. The morphologies, compositions, and crystal quality of the prepared CNFs were characterized by Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), X-ray Diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The electrochemical characteristics of the Si-CNFs composite as an anode of the Li secondary batteries were investigated using a three-electrode cell. The as-deposited Si-CNF composite on the Ni foam was directly employed as an working electrode without any binder, and lithium foil was used as the counter and reference electrode. A glass fiber separator was used as the separator membrane. Two kinds of electrolytes were employed; 1) 1 M LiPF6 was dissolved in a mixture of EC (ethylene carbonate): PC (propylene carbonate): EMC (Ethyl methyl carbonate) in a 1:1:1 volume ratio and 2) 1 M LiClO4 was dissolved in a mixture of propylene carbonate (PC): ethylene carbonate (EC) in a 1:1 volume ratio. The galvanostatic charge-discharge cycling and cyclic voltammetry measurements were carried out at room temperature by using a battery tester. The resulting Si-CNFs composite achieved the large discharge capacity of 613 mAh/g and much improved cycle-ability with the retention rate of 87% after 20 cycles.

In this study, carbon nanofibers were synthesized on iron and copper catalysts by Chemical Vapor Deposition (CVD). Investigation was made with respect to variation on thickness and surface of fibers based on concentration of iron and copper. In order to prepare metal catalysts of respective synthesis, iron nitrate and copper nitrate were calculated in proportion to weight ratio and then dissolved into distilled water. Obtained catalyst precipitates were filtered and then dried for more than 24 hours at 110°C. Carbon nanofibers were composed by using ethylene gas of carbon source through CVD after pulverization of fully dried catalyst precipitates. Analysis through SEM was made in order to investigate structural characteristics of composed carbon nanofibers, and qualitative and quantitative analyses were conducted on elements through EDS. In addition, crystalline analysis was made on carbon nanofibers through XRD and Raman, and specific surface area measurement was carried on carbon nanofibers composed through BET.

No abstract