Koji Kadono

Production of a 100-m-long high-quality graphene transparent conductive film by roll-to-roll chemical vapor deposition and transfer process

A high-quality graphene transparent conductive film was fabricated by roll-to-roll chemical vapor deposition (CVD) synthesis on a suspended copper foil and subsequent transfer. While the high temperature required for the CVD synthesis of high-quality graphene has prevented efficient roll-to-roll production thus far, we used selective Joule heating of the copper foil to achieve this. Low pressure thermal CVD synthesis and a direct roll-to-roll transfer process using photocurable epoxy resin allowed us to fabricate a 100-m-long graphene transparent conductive film with a sheet resistance as low as 150 Ω/sq, which is comparable to that of state-of-the-art CVD-grown graphene films.

Hydrogen storage capacity of commercially available carbon materials at room temperature

The hydrogen storage capacity of five types of commercially available carbon materials with different nanostructures was measured at up to 8 MPa at room temperature using an apparatus based on a volumetric method with an error of less than 0.04 wt %/gr. The highest storage capacity of 0.43 wt % was obtained for purified HiPco™ single-walled carbon nanotubes (SWNTs). In the SWNTs, the hydrogen density in pores with a diameter of less than 1 nm was estimated to be a 0.022 g/ml, which corresponds to 31% of the density of liquid hydrogen. Issues in the development of carbon-based hydrogen storage media are discussed.

Dense hydrogen adsorption on carbon subnanopores at 77 K

Hydrogen adsorption measurements on two types of different carbon nanomaterials were carried out at 77 K up to hydrogen pressures of 2 MPa using the volumetric method modified for low-temperature experiments. The adsorption property was concluded as dense hydrogen physisorption in subnanometer-sized pores because of the Langmuir-type isotherm, reversible adsorption/desorption, and large hydrogen uptake exceeding 2 wt %. The estimated density of adsorbed hydrogen was comparable to the density of bulk liquid hydrogen, indicating that hydrogen filling would be attainable when both the chemical potential of hydrogen and adsorption potential of carbon were optimized.

Repeatable hydrogen adsorption using nanostructured graphite at room temperature

Repeatable hydrogen adsorption and desorption by nanostructured graphite was confirmed using a high-accuracy volumetric measuring apparatus at room temperature. The nanostructured graphite was prepared from graphite powder using a mechanical milling process at a pressure of 2.0×10−4 Pa. The untreated graphite adsorbed 0.02 wt % of hydrogen, while 0.20–0.25 wt % of hydrogen can be repeatedly adsorbed by the nanostructured graphite. Measurements of the hydrogen adsorption rate at constant pressure and pore-size distribution suggest that the hydrogen molecules are adsorbed through a diffusion process into pores with a diameter less than 1 nm.