Hydrogen adsorption on graphene foam synthesized by combustion of sodium ethoxide

Hydrogen storage is a crucial technology for the realization of a carbon-neutral society. However, few materials have been able to approach useful hydrogen storage capacity at reasonable temperatures and pressures. Graphene has an extremely high surface-area-to-weight ratio, is strong, cheap, chemically inert, and environmentally benign. As such it may be an ideal substrate for hydrogen storage. Here we present synthesis of graphene foam by combustion of sodium ethoxide. This technique is low-cost, scalable, and results in a three-dimensional graphene network with a surface area of more than 1200 m²/g. It is applied as a hydrogen storage material at liquid nitrogen temperature, with a capacity of 2.1 wt%.     

Gigacycle fatigue data sheets for advanced engineering materials

Gigacycle fatigue data sheets have been published since 1997 by the National Institute for Materials Science. They cover several areas such as high-cycle-number fatigue for high-strength steels and titanium alloys, the fatigue of welded joints, and high-temperature fatigue for advanced ferritic heat-resistant steels. Some unique testing machines are used to run the tests up to an extremely high number of cycles such as 10¹⁰ cycles. A characteristic of gigacycle fatigue failure is that it is initiated inside smooth specimens; the fatigue strength decreases with increasing cycle number and the fatigue limit disappears, although ordinary fatigue failure initiates from the surface of a smooth specimen and a fatigue limit appears. For welded joints, fatigue failure initiates from the notch root of the weld, because a large amount of stress is concentrated at the weld toe. The fatigue strength of welded joints has been obtained for up to 10⁸ cycles, which is an extremely high number of cycles for large welded joints. The project of producing gigacycle fatigue data sheets is still continuing and will take a few more years to complete. r 2007 Published by Elsevier Ltd.     

Activation of TiFe for hydrogen storage by plastic deformation using groove rolling and high-pressure torsion: Similarities and differences

Intermetallics of TiFe were processed using three different routes: annealing, plastic deformation using groove rolling and severe plastic deformation using high-pressure torsion (HPT). Hydrogen absorption was less than 0.2 wt.% in the coarse-grained annealed sample because of difficult activation. The groove-rolled sample, with subgrain structure and high density of dislocations and cracks, absorbed 0.3, 1.0, 1.4 and 1.7 wt.% of hydrogen in the first, second, third and fourth hydrogenation cycles, respectively. The HPT-processed sample, containing nanograins, absorbed 1.7–2 wt.% of hydrogen in any hydrogenation cycles. Both samples activated by groove rolling and HPT were not deactivated by long time exposure to the air. No surface segregation was detected after groove rolling, while the HPT-processed sample exhibited surface segregation. The current study confirmed the significance of plastic deformation and formation of grain boundaries and cracks on activation for hydrogen storage.     

Change in the molecular weight distribution of poly(ethylene oxide) caused by the complexation with poly(acrylic acid)

The complexation between poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) was made by using double the molar quantity of either polymer component at pH 2 where the resulting complex completely precipitates. After the removal of the precipitate, PEO or PAA remaining in the supernatant was subjected to gel permeation chromatography to investigate the change in the molecular weight distribution (MWD) caused by the complexation. No remarkable difference is observed in the MWD curves for PEO[1] (M_w=1.37 × 10⁴) before and after the complexation with PAA[1] (M_w=1.10 × 10³) and PAA[2] (M_w=4.16 × 10⁵). However, the MWD curves of PEO[2] (M_w=1.26 × 10⁵) and PAA[2] become shortened and shift to the low molecular weight side after the complexation with PAA[1] or [2] and PEO[2], respectively. This tendency is enhanced by increasing the complexation temperature. From these results, it is indicated that the complexation between PEO and PAA deals with an equilibrium reaction, and the equilibrium constant is dependent on the chain length of both polymer components and also on the complexation temperature.     

Estimation of contact stiffness at interfaces in machine structures by a beam model on an elastic foundation

The dynamic properties of machine structures are significantly influenced by an interaction at the mating surfaces of machine elements. This interaction is called contact stiffness, and the development of a simple method for contact stiffness estimation is an important tribological objective. In this paper the contact stiffness is estimated by a beam model vibrating on an elastic foundation. The effects of clamping condition and mating surface topography on the contact stiffness obtained are quantitatively and accurately represented by experimental equations.     

Optimal and reference adaptive processes for the control of regional income disparities

This paper reports on studies into the controllability of the regional income disparities arising from multi-regional economic growth. The necessary condition is that no significant band of regional income disparities should result at the end of the planning period. The regional disparities among nine regions in Japan are explored using the interregional input-output technique and regional production functions. Furthermore, some potentially interesting research probes into the controllability of regional income disparities using the reference adaptive control technique are discussed.     

Stoichiometric formation of poly-ion complexes between human carboxyhemoglobin and potassium poly(vinyl alcohol) sulfate

Summary Colloid titrations of human carboxyhemoglobin were carried out at different pH. The total number of basic groups in the hemoglobin was 95, as evaluated by the titration with potassium poly (vinyl alcohol) sulfate (KPVS). The value estimated was comparable with that obtained from the amino acid sequence of human hemoglobin. This finding indicates the stoichiometric salt-linkage formation between the basic groups in the hemoglobin and the KOSO₃-groups in KPVS.     

Oxochloromolybdenum(V)tetraphenylporphyrin complex-containing polymer as a phosphate ion exchanger

Summary Oxochloro(5,10,15,20-tetraphenylporphyrinate)molybdenum (V) was physically entrapped into poly (styrene) by lyophilizing a benzene solution including both complex and polymer. The functional ability of the obtained complex-containing resin to adsorb H₂PO₄ ^– from an aqueous solution was investigated in the presence of various anions. It was found that the selectivity of the resin for H₂PO₄ ^– is superior to those of conventional anion exchangers.