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In recent years, the extensive participation of turbine generator in deep peak regulation has caused significant damage to the rotor windings, which is rooted in the frequent and significant changes in the electrical load of the rotor, accompanied by thermal expansion and contraction, causing harm to the rotor insulation and stress fatigue of the metal conductor. Hydrogen, as the cooling medium for the rotor windings of turbine generators, has a direct impact on the windings temperature through its parameters. Starting from suppressing the harm of deep peak regulation on the rotor windings, the inhibitory effect of hydrogen parameter changes on the temperature of the gap‐pickup diagonal‐flow rotor is studied. A calculation model for the rotor temperature field of the turbo‐generator with gap‐pickup diagonal‐flow ventilation is established. The finite volume method is used to iteratively calculate the control equations in the fluid‐thermal‐solid coupling heat transfer problem, and the temperature field distribution of various components of the rotor under different excitation loads is obtained. On this basis, the effects of individual adjustment of hydrogen temperature and pressure, as well as the combined adjustment, on the temperature of the rotor windings are studied. Finally, a variable hydrogen parameter adjustment strategy is proposed for the operation of turbo‐generators under deep peak regulation conditions. To a certain extent, the winding temperature fluctuation can be suppressed, which provides a potential solution for the thermal stable operation of the rotor. [ABSTRACT FROM AUTHOR]

The in situ small punch (SP) test method is a simple screening technology developed to assess the hydrogen embrittlement (HE) characteristics of structural steels. This method can easily adjust the influencing parameters such as test temperature, gas pressure, and punch velocity depending on the hydrogen service environment. With increased hydrogen consumption, using pipelines for mass hydrogen transportation is being considered. This study evaluated the HE susceptibility of API-X52 and API-X70 steels, considering the hydrogen usage environment. The study investigated the effects of hydrogen pressure and punch velocity on the HE behaviors of each pipe steel at room temperature using the SP energy and relative reduction in thickness (RRT) to determine their effect on HE susceptibility quantitatively. The study found that hydrogen pressure produced a different HE effect; the lower the hydrogen pressure, the more HE was relieved. Particularly, when the punch velocity was high, such as 1 mm/min, the HE effect was significantly relaxed. However, when the punch velocity was below 0.01 mm/min, HE occurred even at low hydrogen pressure conditions, meaning hydrogen diffusion within the specimen during the SP testing reached a critical hydrogen concentration to create a brittle fracture. Both pipeline steels showed similar HE behaviors under a wide range of H2 pressures and punch velocities, showing an inverse S-curve for quantitative factors of SP energy and RRT against the H2 pressure at 1.0 mm/min punch velocity. The study classified the observed HE behaviors into four types based on quantitative and qualitative aspects. These findings confirm that the in situ SP test is a useful screening technique, and the factor RRT can be effectively applied to the HE screening of pipeline steels in low and high-pressure hydrogen environments. [ABSTRACT FROM AUTHOR]

In recent years, to reduce manufacturing costs and alleviate the rare-earth supply/demand imbalance in the N-Fe-B magnet market, researchers have actively pursued the development of (Nd,Ce)-Fe-B magnets, in which Nd is replaced by Ce. In the present study, we focused on magnetic powders treated by the hydrogenation-disproportionation-desorption-recombination (HDDR) process and explored the relationship between the hydrogen pressure and temperature (PH2-T curves) in the Ce-Fe-B system, which is essential for the development of (Nd,Ce)-Fe-B magnets. It was confirmed that the disproportionation and recombination reactions of both Ce2Fe14B and CeFe2 take place in the Ce-Fe-B system. Furthermore, compared with Nd2Fe14B, the PH2-T curve of Ce2Fe14B was found to be shifted to higher pressure and lower temperature, suggesting a corresponding shift in the HDDR conditions under which good magnetic properties can be obtained. [ABSTRACT FROM AUTHOR]

The authors have investigated hydro-liquefaction of Lemna minor (duckweed) aquatic biomass and a hydrogen-donor solvent, methanol, at temperatures of 180 °C, 200 °C and 220 °C and final reactor pressure values of 70, 80 and 90 bar. The rise in reactor pressure for all reaction temperatures led to an increase in biocrude yield with a maximum higher heating value of 22.19 MJ/kg, while the biochar also depicted its potential to be used in varied applications and as a bio-refinery feedstock. Fourier Transform Infrared Spectroscopy and Gas Chromatography Mass Spectrometry analysis of biocrude indicated the presence of esters and long chain alkanes, ethers, phenols, etc. The main finding of this work disclosed that fuel properties of the present biocrude (without any catalyst) were better than their non-catalytic and hydro-catalytic bio-oil counterparts obtained from similar biomass at a pyrolysis temperature of 550 °C. [ABSTRACT FROM AUTHOR]

This paper is an analysis of driving characteristics of a metal-hydrogen (MH) actuator for driving a rehabilitative system using environmentally friendly hydrogen. The temperature–pressure characteristics of the MH actuator according to the temperature control of the Peltier element were analyzed to apply to the driving of the rehabilitative system to assist the daily activities of the patient. In this experiment, Peltier element is used to control the temperature of MH module which contains hydrogen storage alloy with on/off control scheme and fan on/off. To improve the thermal conductivity of the hydrogen-absorbing alloy, an assembly of MH module based on copper has been used. The control currents of the thermoelectric elements were 1 A and 2 A, and the temperature control range was between 35° and 70°. As the result of experiments, it is proper to act fan only while cooling duration and there exist a proper cooling current to drop temperature rapidly. It takes about 100 s to increase to 70 °C and drop to 35 °C of MH module temperature and about 90 s to increase to 70 °C and drop to 40 °C in ambient temperature 30 °C while fan is on only in cooling duration. The desirable characteristics of MH actuator, which makes it suitable for the uses in medical and rehabilitation applications, have been also studied. [ABSTRACT FROM AUTHOR]

We deposit intrinsic hydrogenated amorphous silicon (a-Si:H) thin films by reactive pulsed laser deposition, for various hydrogen pressures in the 0-20 Pa range, at a low deposition temperature of 120 °C, and investigate the hydrogen incorporation, structural, optical, and electrical properties of the films, as a function of the ambient hydrogen pressure. The film thickness decreases linearly as the hydrogen pressure increases. The hydrogen content of the films is determined by infrared spectroscopy and the optical bandgap from UV-Vis-NIR transmittance and reflectance measurements. Electric measurements yield the dark conductivity of the films. The hydrogen concentration of the films lies in the 1021-1022cm-3 range and increases with the hydrogen pressure until the latter reaches 15 Pa, beyond which the hydrogen concentration decreases. The optical bandgap and dark conductivity follow the hydrogen concentration variation of the films. The dark conductivity lies in the 10-9-10-10S/cm range. An unusually wide optical bandgap of 2.2-2.6 eV is observed. [ABSTRACT FROM AUTHOR]

Canola oil was hydrogenated on an industrial nickel catalyst at 180 |C under a wide range of pressures from 1.5 to 21 bar(a). The effect of hydrogen pressure on the hydrogenation characteristics and fatty acids profile was investigated. The hydrogenation kinetics were described by a simplified three-step model including linolenic acid. The apparent rate constants for the particular reaction steps (hydrogenation, isomerization) kx as well as rate constants kx0 and reaction orders in hydrogen were determined. The results reveal that with the increasing pressure an increase of values of all rate constants was observed, with the largest increase being observed for the rate constant of hydrogenation of monoenes to stearic acid (about 20 times). Moreover, with the increasing pressure the isomerization rate of cis dienes to trans dienes was found to become lower than the dienes hydrogenation rate. Analogously, the cis/trans monoenes isomerization rate was also found to decrease with the increasing pressure. The reaction orders of the hydrogenation steps with respect to hydrogen were in the range of 0.35 to 1.1. The kinetic model was verified by comparsion of predicted fatty acids contents with the experimental data of fatty acids profiles. It emerged that a simplified kinetic model proposed can be utilized to simulate the course of the hydrogenation process and concentrations of fatty acids at a certain iodine value. [ABSTRACT FROM AUTHOR]

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Chiral 1,5-cyclooctadiene rhodium(I) cationic complexes with C2-symmetric chelate diphosphoramidite ligands containing ( R, R)-1,2-diaminocyclohexane as the backbone and two atropoisomeric biaryl units were easily synthesized and fully characterized by multinuclear one- and two-dimensional NMR spectroscopy and elemental analysis. These complexes were used as catalysts in the of dimethyl itaconate, methyl 2-acetamidoacrylate and ( Z)-methyl-2-acetamido-3-phenylacrylate. The rhodium complexes derived from diphosphoramidite ligands that contain two ( R) or ( S) BINOL (2,2′-dihydroxy-1,1′-binaphthyl) units proved to be efficient catalysts, giving complete conversion and very good (up to 88% ee). An uncommon positive H2 pressure effect on the was observed in the of dimethyl itaconate catalyzed by Rh-complex with diphosphoramidite ligand that contains two ( S)-binaphthol moieties. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Decreasing hydrogen partial pressure can not only increase the activity of the hydrogen enzyme but also decrease the products inhibition, so it is an appropriate method to enhance the fermentative hydrogen production from anaerobic mixed culture. The effect of biogas release method on anaerobic fermentative hydrogen production in batch culture system was compared, i.e., Owen method with intermediately release, continuous releasing method, and continuous releasing + CO absorbing. The experimental results showed that, at 35°C, initial pH 7.0 and glucose concentration of 10 g·L, the hydrogen production was only 28 mL when releasing gas by Owen method, while it increased two times when releasing the biogas continuously. The cumulative hydrogen production could reach 155 mL when carbon dioxide in the gas stream was continuously absorbed by 1 mol·L NaOH. The results showed that acetate was dominated, accounting for 43% in the dissolved fermentation products in Owen method, whereas the butyrate predominated and reached 47%-53% of the total liquid end products when releasing gas continuously. It is concluded that the homoacetogenesis could be suppressed when absorbing CO in the gas phase in fermentative hydrogen production system. [ABSTRACT FROM AUTHOR]

Nanostructured thin films of tantalum and titanium were deposited on glass substrate using d.c. magnetron sputtering technique under the argon gas environment at a pressure of 0.1 mbar. Optical transmission and absorption studies were carried out for these samples with pressure of hydrogen. Large changes in both transmission and absorption on loading these films with hydrogen are accompanied by significant phase changes and electronic transformation. Optical photograph shows the colour variation after hydrogenation in case of tantalum film which may be used as decorative mirrors and hydrogen sensors. The hydrogen storage capability of thin films was confirmed by variation in optical properties. [ABSTRACT FROM AUTHOR]

In this study the parameters affecting the foaming process of pure commercial aluminum for preparing of light products are investigated. Titanium hydride (TiH2) powder as a foaming agent (0/5 to 2/5 wt%) added to the aluminum melt. The temperature range of 620 to 660°C was selected. The proper holding temperature and foaming agent content lead to production of foamed aluminum with high porosity percentage and cell structure uniformity. Results show that by adding 1 wt% of TiH2 at foaming temperature of 640°C, cells with 2-6 millimeter in diameter and uniform distribution with 86% porosity are achieved. [ABSTRACT FROM AUTHOR]

This review summarizes the thermodynamics of hydrogen (H2) in mixed gases of nitrogen (N2), methane (CH4) and natural gas, with a special focus on hydrogen fugacity. A compilation and interpretation of literature results for mechanical properties of steels as a function of hydrogen fugacity implies that test results obtained in gas mixtures and in pure hydrogen, both at the same fugacity, are equivalent. However, this needs to be verified experimentally. Among the test methods reviewed here, fatigue crack growth testing is the most sensitive method to measure hydrogen effects in pipeline steels followed by fracture toughness testing and tensile testing. [ABSTRACT FROM AUTHOR]

Hydrogen pressure is often found to cause an inhibiting effect on the kinetics of alkane reactions on metal surfaces. The most common interpretation of such results is focussed on the degree of dehydrogenation of the active surface intermediate following a dissociative mechanism. A series of arguments will be given in favour of an associative mechanism in which the hydrocarbon reacts with an adsorbed hydrogen atom. In this mechanism, the adsorption site or “landing site” is composed of a chemisorbed hydrogen atom associated with an ensemble of “ Z” potential sites. These sites are associated with the hydrogen chemisorption site. The validity of H2 adsorption to determine the metallic dispersion will be also discussed. [ABSTRACT FROM AUTHOR]

The effects of types and amount of catalysts, hydrogen pressure, and kinds of vegetable oils on the formation of CLA isomers were studied during hydrogenation. CLA isomers were identified by using a silver ion-impregnated high-performance liquid chromatograph and 100-m cyano-capillary column gas chromatograph. A selective catalyst (SP-7) produced a considerably higher content of CLA in soybean oil than nonselective catalysts. The maximal quantity of CLA produced in soybean oil during hydrogenation increased greatly with increasing amount of catalyst. By increasing the amount of selective catalyst from 0.05 to 0.3%, the quantity of total CLA obtained was about 1.9 times higher. Changes in hydrogen pressure also greatly influenced total CLA formed. By decreasing hydrogen pressure from 0.24 to 0.024 MPa, the quantity of CLA obtained was about 1.3 times higher. With different oil species (soybean, cottonseed, and corn oils), the time to reach the maximal quantity of CLA was different under the same hydrogenation conditions. However, the maximal quantity of CLA and proportion of CLA isomers formed were almost identical, regardless of oil species tested, under the same hydrogenation conditions. [ABSTRACT FROM AUTHOR]

The complex gaseous equilibria of approximately 10,000 different compositions in the C-H-O ternary system containing up to 40 gaseous species have been calculated at temperatures of 500, 1000, 1500, and 2000 K for total pressures of 0.1, 1.0, and 10.0 atm. The results are represented by selected isoactivity curves of carbon and isobars of hydrogen and oxygen plotted on C-H-O Gibbs composition triangles. The effects of changing composition, temperature, and pressure upon the chemical equilibria in this system are analyzed. In addition, the role of the C-H-O system in selected industrial applications is briefly discussed, including the choice of gas mixtures for the carburization of metals; the extent of carbon deposition at various temperatures, pressures, and compositions in reforming and gasification processes; the free hydrogen partial pressure in the anode compartment of fuel cells and influence of water addition; the oxygen potential in the products of combustion engines; and chemically buffered gas mixtures in controlled atmospheres. [ABSTRACT FROM AUTHOR]

A new criterion for hydrogen-induced cracking (HIC) that includes both the embrittlement effect and the loading effect of hydrogen was obtained theoretically. The surface cohesive energy and plastic deformation energy are reduced by hydrogen atoms at the interface; thus, the fracture toughness is reduced according to fracture mechanics theory. Both the pressure effect and the embrittlement effect mitigate the critical condition required for crack instability extension. During the crack instability expansion, the hydrogen in the material can be divided into two categories: hydrogen atoms surrounding the crack and hydrogen molecules in the crack cavity. The loading effect of hydrogen was verified by experiments, and the characterization methods for the stress intensity factor under hydrogen pressure in a linear elastic model and an elastoplastic model were analyzed using the finite-element simulation method. The hydrogen pressure due to the aggregation of hydrogen molecules inside the crack cavity regularly contributed to the stress intensity factor. The embrittlement of hydrogen was verified by electrolytic charging hydrogen experiments. According to the change in the atomic distribution during crack propagation in a molecular dynamics simulation, the transition from ductile to brittle fracture and the reduction in the fracture toughness were due to the formation of crack tip dislocation regions suppressed by hydrogen. The HIC formation mechanism is both the driving force of crack propagation due to the hydrogen gas pressure and the resisting force reduced by hydrogen atoms. [ABSTRACT FROM AUTHOR]