Papers by Keyword: Carbon Nanofiber

Abstract: The technical issue of direct ethanol fuel cells is slow kinetics of ethanol electrooxidation by using noble metals such as Pt. We propose silica-embedded carbon nanofiber (SECNF) as a catalyst support for the electrooxidation of ethanol to improve catalytic activity of Pt. SECNF was prepared by electrospinning, then Pt nanoparticles were deposited on SECNF. Catalyst characterizations were performed by SEM, EDX, and XRD. Cyclic voltammetry was performed to analyze catalytic activity of Pt/SECNF. The mass activity of Pt/SECNF was 2.9 times higher than a commercially available Pt/carbon catalyst (Pt/C_com). Electrochemically active surface area of Pt/SECNF was lower than Pt/C_com. Hence, the activity enhancement is attributed to the improvement of specific activity for Pt/SECNF. This enhancement is attributed to the interaction between Pt and SiO₂ like hydrogen spillover. Pt/SECNF is a promising catalyst for direct ethanol fuel cells which can reduce Pt loading.

Abstract: An ammonia synthesis using magnetic field to replace Haber-Bosch’s ammonia production is great technological challenge in novel magnetized catalysts area. The carbon nanofiber supported iron catalyst was prepared by modifying carbon nanofiber support surface and later using urea to precipitate iron nitrate by deposition precipitation. It was found that the particle size was in a range of 5-50nm and well dispersion of iron was shown by transmission electron microscopy. This was strongly influenced by alteration of carbon nanofiber surface from hydrophobic to hydrophilic and with high adsorption sites as oxygen functional groups and defects. The lower iron loading between 5 and 40%wt, the lower iron accumulation and the narrower the particle size distribution of 10-20nm. The result suggests that the iron particles are in a good size range for iron catalyst activity for ammonia synthesis as reported by Morawski et.al and Figurski et.al authors.

Abstract: Carbon nanofiber is a new type of carbon materials and it has wide application prospects. At present, there are many kinds of synthesis methods of carbon nanofibers. Among them, preparation of carbon nanofibers from the controllable flame is a new method. It needs simple laboratory equipments and normal atmosphere pressure in this method. Experimental apparatus is including controllable flame burner, thermocouple, mass flow meter and catalyst preparation system, etc. The key factors of synthesis experiment involving the carbon source, the catalyst and high temperature heat source. Characterization of the carbon nanofibers from the controllable flame is by scanning electron microscope (SEM) and transmission electron microscope (TEM).The experimental results indicated that carbon nanofibers with less impurity can be captured at the temperature from 720 to 880 ̊C when carbon monoxide and iron-based catalyst served as carbon source and the catalyst respectively.

Abstract: The intrinsic surface of carbon nanofiber (CNF) is important for supported catalyst preparation. The surface changes due to various techniques applied such as N₂ thermal and HNO₃ oxidation methods. The combination of different analyses is to observe the internal structure through Raman spectroscope, textural properties via N₂ physisorption and morphology of CNF using transmission electron microscope or through quantification of oxygen containing groups by acid base titration. As results, an extension of residence time increases the amount of amorphous and damages the structure of mesoporous CNF texture unexpectedly. The change from hydrophobic to hydrophilic surface of CNF is due to the growing number of oxygen. The surface area of CNF by HNO₃ treatment method produces 115.14m²/g which is higher than that of using thermal method.

Abstract: The materials used for fuel cell separators require a bending strength of more than 70 MPa. Therefore, the contact resistance is required to be 10 mΩ∙cm², respectively. In the present study, vapor grown carbon nanofibers (VGCF) were added to Ti composite using the compression shearing method at room temperature. The mechanical properties of the compacted powder were then measured. The microstructure of the Ti/VGCF composite material was Ti with dispersed VGCF (not alloyed). In addition, the bending strength of all Ti/VGCF composites was more than 800 MPa, and the bending strength of 0-1 vol% VGCF composites was twice as much as that for Ti rolled material (ASTM grade 2). Ti/VGCF thin plates also exhibited excellent electrical property. The contact resistance of 5 vol% VGCF was found to be three times smaller than that of Ti rolled material. These properties make the Ti/VGCF composite material suitable as a separator material.

Abstract: The paper studied the influence of carbon nanofiber on the mechanical property of PALC and discussed the modified mechanism by SEM analysis. The results show that the addition of 2.0wt./% carbon nanofiber is favorable for tensile splitting strength of PALC pastes owing to their filling pore and bridging enhancement effect of the nanofibers.

Abstract: In present study, artificial neural network (ANN) was used to predict the tensile moduli of carbon nanofibers (CNF)/epoxy composites. The tensile properties of CNF/epoxy composites made by different dispersion technique were measured by tensile test. It was found that the tensile properties are seriously affected by the CNF fraction, ultrasonication time and mechanical stirring time. According to the test results, ANN was trained and used to predict the tensile moduli of CNF/epoxy composites. By compared the predicted values with the experimental data, it was demonstrated that the back propagation ANN model is a promising tool for prediction of properties of composites.

Abstract: Similar amount of carbon with three different types of morphologies, i.e. smooth pyrolytic carbon (SPC), granular pyrolytic carbon (GPC) and carbon nanofiber (CNF) was coated on the natural graphite (NG) spheres in a fluidized bed by chemical vapor deposition (CVD) from acetylene. The effect of carbon-coating morphologies on the electrochemical performance of NG spheres were studied, the results show that: PC is more effective in improving the first coulombic efficiency (CE); both GPC and CNF can improve the cyclability, however, GPC improves the first CE whereas CNF decreases the first CE.

Abstract: By employing the electrospinning technique and subsequent carbonization processes, porous carbon/nickle (C/Ni) composite nanofibers with diameters of 100-200 nm were successfully prepared. Two polymer solutions of polyacrylonitrile (PAN), polyvinyl pyrrolidone (PVP), and Ni (CH₃COOH)₂ (Ni (OAc)₂) were used as C/Ni composite nanofiber precursors. The study revealed that C/Ni composite nanofibers were successfully prepared and nickle particles with diameters of 20-70 nm were uniformly scattered in the carbon nanofibers. It was also observed that the fiber with clear fibrous morphology with particles broke into shorter fibers after sinter. X-ray diffraction (XRD) showed that these particles crystallized with the face centered cubic (FCC) structure. The Brunauer-Emmett-Teller (BET) analysis indicated that C/Ni composites nanofibers with meso-pores possessed larger specific surface area than that of carbon nanofibers.

Abstract: Deposition precipitation method was employed to synthesize carbon nanofiber based Cu-ZrO₂ catalyst (Cu-ZrO₂/CNF). Carbon nanofibre of herringbone type was used as a catalyst support. Prior deposition of catalyst particles, carbon nanofibre was oxidized to (CNF-O) with nitric acid solution. Catalyst was characterized by X-ray diffraction (XRD), Fourier Transmission Infrared (FTIR), Transmission Electron Microscopy (TEM) and Temperature-Programmed Reduction (TPR). Highly loaded, well-dispersed and thermally stable catalyst particles with average size of 4 nm were obtained by deposition precipitation method. Reaction studies confirmed the activity of the catalyst towards methanol formation.