Search results for " hydrogen"
showing 10 items of 319 documents
Nanoscale membrane electrode assemblies based on porous anodic alumina for hydrogen–oxygen fuel cell
2007
In this paper, we demonstrate that nanoscale membrane electrode assemblies, functioning in a H 2/O 2 fuel cell, can be fabricated by impregnation of anodic alumina porous membranes with Nafion® and phosphotungstic acid. Porous anodic alumina is potentially a promising material for thin-film micro power sources because of its ability to be manipulated in micro-machining operations. Alumina membranes (Whatman, 50 μm thick, and pore diameters of 200 nm) impregnated with the proton conductor were characterized by means of scanning electron microscopy, X-ray diffraction, and thermal analysis. The electrochemical characterization of the membrane electrode assemblies was carried out by recording t…
Wetting behavior of solid hydrogen films
1996
We have studied the dewetting of quench-condensed solid hydrogen films on bare and Ne plated Ag substrates. Information about the morphology of the films during the dewetting process is obtained from measurements of photoelectron tunneling through the films and complementary surface plasmon resonance data. Plating the Ag substrate with Ne films of various thickness allows to tune the strength of the van der Waals interaction with the hydrogen and thus to change the H2 films from a state of incomplete to complete wetting.
Photo-switching and -cyclisation of hydrogen bonded liquid crystals based on resveratrol
2020
A series of hydrogen-bonded liquid crystals based on resveratrol and resveratrone is reported and investigated with respect to their photo-switchability (at 405 nm) and photo-cyclisation (at 300 nm).
Study of Gasdynamic Electron Cyclotron Resonance Plasma Vacuum Ultraviolet Emission to Optimize Negative Hydrogen Ion Production Efficiency
2019
Negative hydrogen ion sources are used as injectors into accelerators and drive the neutral beam heating in ITER. Certain processes in low-temperature hydrogen plasmas are accompanied by the emission of vacuum ultraviolet (VUV) emission. Studying the VUV radiation therefore provides volumetric rates of plasma-chemical processes and plasma parameters. In the past we have used gasdynamic ECR discharge for volumetric negative ion production and investigated the dependencies between the extracted H$^-$ current density and various ion source parameters. It was shown that it is possible to reach up to 80 mA/cm$^2$ of negative ion current density with a two electrode extraction. We report experime…
Chiral mesophases of hydrogen-bonded liquid crystals
2020
The chiral induction in hydrogen-bonded liquid crystals is investigated. The experimental study was accompanied by detailed density functional theory calculations and variable-temperature solid-state deuteron NMR measurements indicating that interactions between the linking groups of the hydrogen-bond accepting unit play a key role in the chiral induction.
Effect of Hydrogen and Absence of Passive Layer on Corrosive Properties of Aluminum Alloys
2020
This paper reports the results of research on the effect of hydrogen permeation and the absence of passive layers on the variations in the corrosive properties of aluminum alloys. The study demonstrated that such variations contribute to the deterioration of corrosive properties, which in turn contributes to shortening the reliability time associated with the operation of aluminum alloy structures. The analysis involved structural aluminum alloys: EN AW-1050A, EN AW-5754, and EN AW-6060. It was demonstrated that the absorption of hydrogen by the analyzed alloys led to the shift of the electrode potential to the negative side. The built hydrogen corrosion cells demonstrate in each case the f…
Improving the mesomorphic behaviour of supramolecular liquid crystals by resonance-assisted hydrogen bonding
2019
A systematic structure-property relationship study on hydrogen-bonded liquid crystals was performed, revealing the impact of resonance-assisted hydrogen bonds (RAHBs) on the self-assembling behavior of the supramolecular architecture. The creation of a six-membered intramolecular hydrogen-bonded ring acts as a counterpart to the self-organization between hydrogen bond donators and acceptors and determines thus the suprastructure. Variation of the hydrogen-bonding pattern allowed us to significantly improve the temperature range of the reported liquid crystalline assemblies.
Character of the Reaction between Molecular Hydrogen and a Silicon Dangling Bond in Amorphous SiO2
2007
The passivation by diffusing H2 of silicon dangling bond defects (E′ centers, O3tSi•) induced by laser irradiation in amorphous SiO2 (silica) is investigated in situ at several temperatures. It is found that the reaction between the E′ center and H2 requires an activation energy of 0.39 eV and that its kinetics is not diffusionlimited. The results are compared with previous findings on the other fundamental paramagnetic point defect in silica, the oxygen dangling bond, which features completely different reaction properties with H2. Furthermore, a comparison is proposed with literature data on the reaction properties of surface E′ centers, of E′ centers embedded in silica films, and with th…
Hyperpolarization of cis ‐ 15 N 2 ‐Azobenzene by Parahydrogen at Ultralow Magnetic Fields**
2021
The development of nuclear spins hyperpolarization, and the search for molecules that can be efficiently hyperpolarized is an active area in nuclear magnetic resonance. In this work we present a detailed study of SABRE SHEATH (signal amplification by reversible exchange in shield enabled alignment transfer to heteronuclei) experiments on 15 N2 -azobenzene. In SABRE SHEATH experiments the nuclear spins of the target are hyperpolarized through transfer of spin polarization from parahydrogen at ultralow fields during a reversible chemical process. Azobenzene exists in two isomers, trans and cis. We show that all nuclear spins in cis-azobenzene can be efficiently hyperpolarized by SABRE at suit…
Structure of anisole derivatives by total neutron and X-ray scattering: Evidences of weak C–H⋯O and C–H⋯π interactions in the liquid state
2020
Abstract High resolution, total neutron and X-ray scattering data have been used in synergy with Molecular Dynamics simulations to access atomistic scale insight into the structure of anisole and 2,3,5-trimethylanisole, two aromatic compounds bearing an electron-donating methoxy group. A detailed description is provided for the main interactions occurring in these systems, including π-π stacking and weak hydrogen bonding correlations: C H⋯O and C H⋯π. The existence of preferential orientations of the first shell coordinating molecules and the specific nature of the interactions involving the π cloud and the polar methoxy group have been reported and discussed.