Hydrogen diffusivity and tensile-ductility loss of solution-treated austenitic stainless steels with external and internal hydrogen

The effects of external and internal hydrogen on the slow-strain-rate tensile (SSRT) properties at room temperature were studied for ten types of solution-treated austenitic stainless steels containing a small amount of additive elements. The hydrogen diffusivity and solubility of the steels were measured with high-pressure hydrogen gas. The remarkable tensile-ductility loss observed in the SSRT tests was attributed to hydrogen-induced successive crack growth (HISCG) and was successfully quantified according to the nickel-equivalent content (Ni_eq), which represents the stability of the austenitic phase. The relative reduction in area (RRA) of the steels with a larger Ni_eq was influenced by the hydrogen distribution, whereas that of the steels with a smaller Ni_eq was not. This unique trend was interpreted with regard to the hydrogen distribution and fracture morphology (HISCG or microvoid coalescence).     

Preparation of carbon-supported PtCo nanoparticle catalysts for the oxygen reduction reaction in polymer electrolyte fuel cells by an electron-beam irradiation reduction method

We prepared carbon-supported PtCo bimetallic nanoparticles (PtCo/C) as electrode catalysts for the oxygen reduction reaction (ORR) at the cathodes in polymer electrolyte membrane fuel cells (PEFCs) by an electron-beam irradiation reduction method (EBIRM). An EBIRM allows nanoparticles to be easily prepared by the reduction of precursor ions in an aqueous solution irradiated with a high-energy electron beam. The structures of PtCo/C were characterized by transmission electron microscopy, inductively coupled plasma atomic emission spectrometry, and the techniques of X-ray diffraction and X-ray absorption near edge structure. It found for the first time that both PtCo alloy and Co oxide were prepared simultaneously on the carbon support by an EBIRM. The catalytic activity and durability of PtCo/C were evaluated by linear-sweep voltammetry and cyclic voltammetry, respectively. The addition of Co to Pt/C not only enhanced the catalytic activity for the ORR but also improved the catalytic durability. As the Co concentration increased, both behaviors became pronounced. These improvements are explained by the effects of both PtCo alloy and Co oxide. We demonstrated that an EBIRM can not only synthesize the alloy and oxide simultaneously on the carbon support but also mass-produce the electrode catalysts for PEFC cathodes.     

Real-time observation of Brownian motion and cluster movement of ferro- and non-magnetic particles in magnetic fluids

Cluster movements of ferro- and non-magnetic particles in magnetic fluids were investigated using optical microscope system and image processing system. Real-time visualizations of the Brownian motion of particles and the chain-like cluster movement of both types of particle were performed under a magnetic field. The principal objectives of this study were to clarify the applicability of the optical microscope system and image processing system, and to analyze the growth process of the cluster under magnetic field. The analysis of particle image was done using Particle Tracking Velocimetry (PTV). The results clarified that the real-time observation of Brownian motion and cluster movement of ferro- and non-magnetic particles in magnetic fluids can be carried out using the optical microscope system and the PTV image measurement. Independent continuous measurements with changing positions and velocity of the minute particle were made possible. The study concluded that the system can obtain satisfactory results on growth process measurement of cluster under a magnetic field.     

A comparative study of NiO-Ce0.9Gd0.1O1.95 nanocomposite powders synthesized by hydroxide and oxalate co-precipitation methods

In this study, NiO-Ce_0.9Gd_0.1O_1.95 (NiO-GDC) nanocomposite powders, which were applied as anode materials of low temperature solid oxide fuel cells (SOFCs), were synthesized by hydroxide and oxalate reverse co-precipitation methods, respectively. The crystal phases, crystallite size, particle size, particle size distribution, and sintering characteristics of the synthesized NiO-GDC nanocomposite powders were investigated and compared. Results showed that the different co-precipitation methods affected strongly the synthesis and characteristics of the NiO-GDC nanocomposite powders. The NiO-GDC nanocomposite powders could be synthesized at lower temperature by the hydroxide reverse co-precipitation method, and the synthesized NiO-GDC nanocomposite powders had better sinterability. The NiO-GDC nanocomposite powders synthesized by the oxalate reverse co-precipitation method had smaller particle size and uniform particle size distribution and, however, were easy to result in crack formation in the sintered disks.     

The effect of La oxide additive on the solubility of NiO in molten carbonates

A comprehensive analysis on a novel energy recovery system for reformate-based proton exchange membrane (PEM) fuel cell systems is presented. The energy recovery system includes a throttling valve, a heat exchanger, a compressor, and is coupled with a coolant loop for the fuel cell stack. The feed stock of the fuel reformer, which is primarily a mixture of water and fuel, is vaporized in the heat exchanger and is then compressed to a sufficiently high pressure before it is ducted into the fuel reformer. The analysis includes the throttling of two-phase fuel/water mixture and vaporization in the heat exchanger to obtain the temperature and pressure of the mixture at the inlet of the compressor. The results indicate that the power plant efficiency with the energy recovery system can be increased by more than 20% compared to that of a fuel cell power plant without the energy recovery system. Additionally, more than 25% of the waste heat generated by the fuel cell stack can be removed due to the energy recovery system, and the fuel burned for the fuel reforming purpose is reduced by more than 70%.     

Intracavity second-harmonic generation at 320 nm of an actively Q-switched Pr:LiYF4 laser

We demonstrate pulse laser operation of a Pr:LiYF(4) laser pumped by InGaN laser diodes (444 nm) using an acousto-optic modulator. We obtained a maximum laser peak power of 167 W (4 μJ/pulse) with a pulse width of 24 ns at an 11 kHz repetition rate for a 63 nm wavelength. Employing an 8 mm long lithium triborate nonlinear crystal in the laser cavity, we obtained a maximum peak power of 55 W (2.7 μJ/pulse) at 320 nm, which corresponds to a conversion efficiency of 69% with respect to the fundamental laser energy. The UV laser pulse width was 36 ns.     

Surface coating with a high resistance to hydrogen entry under high-pressure hydrogen-gas environment

Development of a surface coating with high resistance to hydrogen entry under a high-pressure hydrogen-gas environment is presented. Two aluminum-based coatings were developed on the basis of preliminary tests: two-layer (alumina/Fe–Al) and three-layer (alumina/aluminum/Fe–Al) coatings, deposited onto cylindrical and pipe (Type 304 austenitic stainless steel) surfaces by immersion into a specially blended molten aluminum alloy. The coated specimens were exposed to hydrogen gas at 10–100 MPa at 270 °C for 200 h. Specimen hydrogen content was measured by thermal desorption analysis; hydrogen distributions were analyzed by secondary ion mass spectroscopy. Both coatings showed high hydrogen-entry resistance at 10 MPa. However, resistance of the two-layer coating clearly decreased with an increase in pressure. In contrast, the three-layer coating showed excellent hydrogen-entry resistance at a wide pressure range (10–100 MPa), achieved by the combined effect of alumina, aluminum, and Fe–Al layers.     

Estimates of GHG emission reduction potential by country,sector, and cost

In this study, emission reduction potentials in greenhouse gases (GHG) are assessed by country, sector, and cost using a GHG emission reduction assessment model with high resolutions with respect to region and technology and high consistency in terms of assumptions, interrelationships, and solution principles. Model analyses show that large potential reductions can be achieved at low cost in developing countries and power sectors. In addition, cost-efficient emission reductions were evaluated for some international emission reduction targets that have been derived on the basis of the principle of common but differentiated responsibilities among developed and developing countries. If (1) emission reduction measures at negative costs and below 50 $/tCO₂ for developed countries, (2) intensity improvement measures for selected sectors at negative costs and below 20 $/tCO₂ for major developing countries, and (3) all emission reduction measures with negative costs for other developing countries in 2020 are adopted, then emission reductions of 8.9, 14.8, and 27.7 GtCO₂ eq./yr compared to the technology-frozen case can be expected in developed countries, major developing countries, and globally, corresponding to a 11% decrease, 40% increase, and 17% increase from 2005 levels, respectively. Large-scale emission reductions can be achieved even if CO₂-intensity targets for major sectors are assumed for major developing countries.