Nano Channels Research Articles

Expanded graphite as an electrode material for an alcohol fuel cell

Abstract An efficient graphite electrode has been developed using expanded graphite as the starting material. A graphite plate has been expanded by doping with potassium vapour using a vapour incorporation technique developed at our laboratory. The extent of expansion of the electrode plate is about 20% of its initial thickness. These expanded graphite electrodes have been platinized by an electrodeposition method. The electrocatalytic activity of platinized expanded graphite has been examined, and the discharge profile of a conventional laboratory model fuel cell comprising a platinized Pt air cathode, expanded platinized graphite anode and sulphuric acid (2 M) as electrolyte has been measured. Analysis of the electrochemical parameters of the laboratory model cell clearly indicates that the expanded Pt graphite electrode shows better electrochemical behaviour towards methanol (1 M), ethanol (1 M) and propanol (1 M) oxidation than that of unexpanded graphite electrodes. The results are explained in terms of efficient electrocatalytic activity of the nano channel formed after the expansion. These electrodes are expected to have promising applications in fuel cells.

Expanded graphite as an electrode material for an alcohol fuel cell

An efficient graphite electrode has been developed using expanded graphite as the starting material. A graphite plate has been expanded by doping with potassium vapour using a vapour incorporation technique developed at our laboratory. The extent of expansion of the electrode plate is about 20% of its initial thickness. These expanded graphite electrodes have been platinized by an electrodeposition method. The electrocatalytic activity of platinized expanded graphite has been examined, and the discharge profile of a conventional laboratory model fuel cell comprising a platinized Pt air cathode, expanded platinized graphite anode and sulphuric acid (2 M) as electrolyte has been measured. Analysis of the electrochemical parameters of the laboratory model cell clearly indicates that the expanded Pt graphite electrode shows better electrochemical behaviour towards methanol (1 M), ethanol (1 M) and propanol (1 M) oxidation than that of unexpanded graphite electrodes. The results are explained in terms of efficient electrocatalytic activity of the nano channel formed after the expansion. These electrodes are expected to have promising applications in fuel cells.

Analysis of nano channel formation in quartz cubes by laser-induced process

A novel laser processing technique was developed for making channels in the nanoregime in this paper.A Nd:YAG laser was used to dry fabricate micro channels(25μm～100μm di-ameter)in a 1 cm~3 fused silica substrate by thermal-induced processing.By controlling the locationsof these initiating micro...

Stepped carbon nanotubes synthesized in anodic aluminum oxide templates

Anodic aluminum oxide templates with stepped nano channels were fabricated by repeated anodization and pore widening processes, and carbon nanotubes were grown on the templates without catalytic metals by pyrolysis of acetylene. High-resolution transmission electron microscopy revealed that the wall of the CNTs has a multi-wall structure made of stacked graphite flakes of several nm sizes. For the carbon nanotube formation on alumina, we propose a pyrolytic CVD of carbon on alumina surface instead of a synthesis via catalytic action of the alumina. The electrical properties of the stepped and linear CNTs did not show remarkable difference because of the highly defective structure of the flaked tubes.

Stepped carbon nanotubes synthesized in anodic aluminum oxide templates

Anodic aluminum oxide templates with stepped nano channels were fabricated by repeated anodization and pore widening processes, and carbon nanotubes were grown on the templates without catalytic metals by pyrolysis of acetylene. High-resolution transmission electron microscopy revealed that the wall of the CNTs has a multi-wall structure made of stacked graphite flakes of several nm sizes. For the carbon nanotube formation on alumina, we propose a pyrolytic CVD of carbon on alumina surface instead of a synthesis via catalytic action of the alumina. The electrical properties of the stepped and linear CNTs did not show remarkable difference because of the highly defective structure of the flaked tubes.

Fabrication of Alumina Membrane Using Anodic Oxidation Process

Anodic aluminum oxide (AAO) membrane was made of aluminum sheet (99.6%, 0.2 mm thickness). The regular array of hexagonal nano pores or channels were prepared by two step anodization process. A detail description of the AAO fabrication is presented. After the 1st anodization in oxalic acid (0.3 M) at 45 V, The formed AAO was removed by etching in a solution of 6 wt% <TEX>$H_3$</TEX><TEX>$PO_4$</TEX>＋1.8 wt% <TEX>$H_2$</TEX><TEX>$CrO_4$</TEX>. The regular arrangement of the pores was obtained by the 2nd anodization, which was carried out in the same condition as the 1st anodization. Subsequently, the alumina barrier layer at the bottom of the channel layer was removed in phosphoric acid (1M) after removing of aluminum. Pore diameter, density, and thickness could be controlled by the anodization process parameters such as applied voltage, anodizing time, pore widening time, etc. The pore diameter is proportional to the applied voltage and pore widening time. The pore density and thickness can be controlled by anodization temperature and voltage.

Molecular dynamics simulation of a liquid in a complex nano channel flow

We report some molecular dynamics simulation results for a complex nano channel flow. In certain flow geometry, some of the flow features cannot be predicted by the Navier–Stokes equations with no-slip boundary conditions. The results show a loss of dynamic similarity for flows with similar geometry and global dimensionless flow parameters. Nano-sized vortex flow can be developed at low Reynolds numbers due to near-wall molecules having large enough momenta, resulting in qualitatively different flow field from that predicted by the Navier–Stokes equations.

Orientation of Fluorescent Dyes in the Nano Channels of Zeolite L

The orientation of the S1 ← S0 π,π* transition dipole moments of oxonine (Ox+), pyronine (Py+), and POPOP (5,5‘-diphenyl-2,2‘-p-phenylenebis(oxazole)) in the channels of zeolite L crystals was investigated by means of fluorescence microscopy and single-crystal imaging. Qualitative observations led to the result that the transition moment of POPOP is aligned along the c-axis of the hexagonal crystals whereas the fluorescence of Ox+ and Py+ is not. More detailed investigations on Ox+ showed a cone-shaped distribution of the transition moments with a half-cone angle of 72°. The orientation of the transition dipole moment for all of these molecules is parallel to the molecules' long axis. We found by means of space-filling arguments that POPOP, the van der Waals length of which is about 21 A, can only be aligned along the channel axis. This is in full agreement with the observed fluorescence anisotropy. For Ox+ and Py+, geometrical arguments based on the zeolite L structure give room for only two possible arr...