Small Concentrations Of Hydrogen Research Articles

Progress towards edge-localized mode suppression via magnetic perturbations in hydrogen plasmas

The suppression of edge-localized modes (ELMs) by applying resonant magnetic perturbations (RMPs) is well studied in low collisionality deuterium plasmas as a measure to reduce transient divertor heat loads. However, ELM suppression has yet to be demonstrated in non-nuclear fuels such as hydrogen and hydrogen + helium mixtures which are the main ion species to be used in the ITER pre-fusion power operation (PFPO) phase. For the first time, attempts have been made to access ELM suppression with RMPs in ITER-like low collisionality hydrogen plasmas at DIII-D and ASDEX Upgrade. The DIII-D experiments focused on operation with injected power slightly above the L–H power threshold similar to the expected conditions in the ITER PFPO phase with limited external heating power. The RMPs were found to trigger H–L backtransitions, which is shown to be avoided by reducing the L–H power threshold by diluting the plasma with helium. The additional helium combined with a larger measured neutral density of hydrogen inside the separatrix compared to ELM suppressed deuterium plasmas precluded access to a pedestal top density below the known RMP-ELM suppression threshold. At ASDEX Upgrade, RMP-ELM suppression has been achieved when the concentration of 1H in the hydrogen isotope mix is below 40% . While all known access criteria for RMP-ELM suppression were met above this threshold, full ELM suppression was replaced by strong mitigation. The most prominent difference between the hydrogen and deuterium plasmas was a change of turbulence characteristics in the pedestal where Doppler reflectometry measurements suggest a significant reduction of turbulence even at small hydrogen concentrations. In conclusion, these experiments not only identify issues that may prevent access to RMP-ELM suppression in the ITER PFPO phase, but also highlight missing physics in our current understanding of RMP-ELM suppression such as potentially the role of turbulence in the pedestal gradient region.

In Ukrainian

The review material reveals the question of the influence of impurities on the physical properties of alloys, as well as the influence of gases on processes in alloys. It has been established that the presence of hydrogen affects diffusion in alloys, and gases have a significant effect on the thermoelectromotive force of metals. The paper describes the addition of a third element to binary systems, which can expand or narrow the domain of existence of an ordered phase. The above examples of adding an impurity of vanadium or molybdenum to an alloy of iron and chromium increase the ordering temperature. It has been established that gases can have a significant effect on the thermoelectromotive force of metals and increase the hardness and reduce the ductility of metals, as well as cause their brittleness and delamination. It has been established that hydrogen (H2) in alloys (for example, Fe-Ni and Au-Cu) affects diffusion and atomic ordering processes. Also, a small concentration of hydrogen, as an impurity, can change the electrical resistance of alloys (for example, in a Pd-Au alloy). It has been established that the addition of a third element to binary systems can change the state diagram, which must be taken into account when solving problems for the production of heat treatment modes for alloys, determining the conditions for phase equilibrium, etc. The paper considers the dependence of hydrogen solubility on temperature in metals (Cu, Fe and Al) and establishes the dependence of hydrogen solubility in a metal on the concentration of impurity metals. The temperature dependence of hydrogen solubility in Fe-V alloys is also shown. The shift of the density of state is studied for different distributions of impurity atoms in the alloy in the order-disorder system, and the dependence of the density of states of disordered and ordered solid solutions is studied. The dependence of the relative solubility of atoms introduced into the pores of alloys with an fcc structure (of the Cu3Au type) is indicated, taking into account the solubility, on the parameter χ, which is proportional to the degree of long-range order in the octahedral and tetrahedral pores of the alloys. The dependence of the relative solubility of intercalated atoms in octahedral pores of alloys with a bcc structure (such as CuZn and Fe3Al) is considered. A plot of the dependence of the concentration of dissolved impurity atoms on the degree of order is shown for substitutional alloys with a bcc lattice, where the M2 coefficient is introduced, which does not depend on the degree of order. The effect of pressure as a measure of long-range order is also studied, where its step decreases or increases, or decreases and then increases and vice versa (order-disorder phase transition). An equally important result is the graphic dependence of solubility (c) on pressure (P) in disordered and ordered alloys.

Application of a Microfabricated Microwave Resonator in a Co - Pd –Based Magnetic Hydrogen-Gas Sensor

We investigate the ferromagnetic resonance (FMR) response of microfabricated microwave resonators loaded with small ${\mathrm{Co}}_{16}{\mathrm{Pd}}_{84}$ alloy rectangles. A major increase in the FMR signal-to-noise ratio is achieved by employing the microwave-resonator structure. A FMR peak shift similar to that of ${\mathrm{Co}}_{16}{\mathrm{Pd}}_{84}$ continuous films is measured in the presence of hydrogen gas in the sample environment. We show that the very high sensitivity of the FMR signal of the ${\mathrm{Co}}_{16}{\mathrm{Pd}}_{84}$ alloy rectangle to hydrogen exposure can be used to measure relatively small hydrogen-concentration steps near 100% ${\mathrm{H}}_{2}$. Additionally, we also demonstrate that this structure can measure hydrogen over a concentration range from 3% to 100% ${\mathrm{H}}_{2}$ in ${\mathrm{N}}_{2}$. In time-dependent FMR measurements, we discover a temperature dependence of the FMR signal, which we relate to intrinsic temperature-dependent changes in saturation magnetization and the magnetic anisotropy of the $\mathrm{Co}$-$\mathrm{Pd}$ alloy.

Influence of hydrogen core force shielding on dislocation junctions in iron

The influence of hydrogen on dislocation junctions was analysed by incorporating a hydrogen dependent core force into nodal based discrete dislocation dynamics. Hydrogen reduces the core energy of dislocations, which reduces the magnitude of the dislocation core force. We refer to this as hydrogen core force shielding, as it is analogous to hydrogen elastic shielding but occurs at much lower hydrogen concentrations. The dislocation core energy change due to hydrogen was calibrated at the atomic scale accounting for the nonlinear inter-atomic interactions at the dislocation core, giving the model a sound physical basis. Hydrogen was found to strengthen binary junctions and promote the nucleation of dislocations from triple junctions. Simulations of microcantilever bend tests with hydrogen core force shielding showed an increase in the junction density and subsequent hardening. These simulations were performed at a small hydrogen concentration realistic for bcc iron.

Continious series of solid solutions Tb2Ni17-xCox, 0 ≤ x ≤ 17. Structural and electrochemical characteristics of alloys

Synthesis, study of the phase, structural and electrochemical characteristics of the alloys from homogeneity range of the continious series of solid solutions Tb 2 Ni 17- x Co x (0 ≤ x ≤ 17) was carried out in the prototype of NiMH battery for the purpose of search of new materials for modern electrical energy sources. The samples for investigation were synthesized by arc melting of pure components under an argon atmosphere with further annealing at 600 oC for one month in evacuated silica ampules. X-ray powder diffraction, scanning electron microscopy, X-ray fluorescent and energy dispersive X-ray spectroscopy were used to examine the alloys before and after electrochemical studies. The process of electrochemical hydrogenation of the samples was carried out in two-electrode “Swagelok-cell” prototype of NiMH battery. Studied alloys were used as anode materials (during discharging of the batteries). A mixture of Ni(OH) 2 and graphite served as cathode material (during discharging of the batteries). The anode and cathode materials were soaked by 6 M solution of KOH as electrolite and separated by pressed cellulose to avoid contacts between them. During charging we obtained the hydride of inclusion on the basis of Tb 2 Ni 17- x Co x phases. The process of hydrogenation is characterized by one stage, namely the inclusion of H-atoms into vacant tetrahedral and octahedral voids. At the small hydrogen concentration its atoms occupy the octahedral voids (6 h ) formed by two Tb atoms and four (Ni, Co) atoms. As electrode materials, the studied phases are relatively stable in the electrolyte solution. Increasing of the cobalt content improves the electrode capacity, but decreases the corrosion stability of the electrodes to the action of the electrolyte that is confirmed by the decreasing of crystallinity, passivation of the surfaces and changing of quantitative compositions of the samples. The amount of mobile hydrogen under the same conditions (during discharge) is the following: 1.53 H/f.u. for Tb 2 Ni 17 , 1.83 H/f.u. for Tb 2 Ni 12 . 2 Co 4 . 8 and 2.08 H/f.u. for Tb 2 Ni 6 . 5 Co 10 . 5 . The specific capacity does not exceed 60 mA∙h/g. The electrochemical processes in all cases led to changing of the surface morphology, reducing of the grains size. Significant amorphization was observed for electrodes with higher content of Co. Keywords : intermetallic compound, continious series of solid solutions, electrochemical hydrogenation, nickel metal hydride batteries.

Hydrogen Sensing Properties of Copper-Doped Zinc Oxide Thin Films

A highly sensitive hydrogen gas sensor has been developed utilizing 3% copper-doped zinc oxide thin films. These films were deposited using pulsed laser deposition technique on quartz substrates with predeposited interdigitated platinum electrodes. The deposited films were characterized by X-ray diffraction and atomic force microscopy. The hydrogen sensing properties of the sensor were studied at three operating temperatures, viz., 50 °C, 100 °C, and 150 °C. We observed that the sensor shows good performance even at a low operating temperature of 50 °C for a very small concentration of hydrogen (10 ppm).

Dielectric Properties of Cryogenic Gas Mixtures Containing Helium, Neon, and Hydrogen

Past efforts of cooling high temperature superconducting (HTS) power cables by gaseous cryogens focused exclusively on helium. The limited dielectric strength of helium gas necessitated alternatives that could be used in the temperature range suitable for HTS power applications. This paper presents the benefits of gas mixtures containing helium with small concentrations of hydrogen or neon to mitigate the limited dielectric strength of pure helium gas. The expectation was that such gas mixtures could improve dielectric characteristics while maintaining the thermal, non-flammable and non-corrosive properties of pure helium gas. The AC breakdown voltage of helium gas mixtures containing 4 mol% neon or 4 mol% hydrogen respectively have been measured and compared to those of pure helium and pure neon. All measurements were performed at 77 K at gas pressure levels between 0.5 and 2.0 MPa. While the 4 mol% neon mixture did not result in any improvement over pure helium, the 4 mol% hydrogen mixture resulted in 80% higher breakdown strength. This is expected to enable higher operating voltages for gas cooled HTS power devices.

Hydrogenization of underground storage of natural gas

The intermittent production of the renewable energy imposes the necessity to temporarily store it. Large amounts of exceeding electricity can be stored in geological strata in the form of hydrogen. The conversion of hydrogen to electricity and vice versa can be performed in electrolyzers and fuel elements by chemical methods. The nowadays technical solution accepted by the European industry consists of injecting small concentrations of hydrogen in the existing storages of natural gas. The progressive development of this technology will finally lead to the creation of underground storages of pure hydrogen. Due to the low viscosity and low density of hydrogen, it is expected that the problem of an unstable displacement, including viscous fingering and gravity overriding, will be more pronounced. Additionally, the injection of hydrogen in geological strata could encounter chemical reactivity induced by various species of microorganisms that consume hydrogen for their metabolism. One of the products of such reactions is methane, produced from Sabatier reaction between H2 and CO2. Other hydrogenotrophic reactions could be caused by acetogenic archaea, sulfate-reducing bacteria and iron-reducing bacteria. In the present paper, a mathematical model is presented which is capable to reflect the coupled hydrodynamic and bio-chemical processes in UHS. The model has been numerically implemented by using the open source code DuMuX developed by the University of Stuttgart. The obtained bio-chemical version of DuMuX was used to model the evolution of a hypothetical underground storage of hydrogen. We have revealed that the behavior of an underground hydrogen storage is different than that of a natural gas storage. Both, the hydrodynamic and the bio-chemical effects, contribute to the different characteristics.

Applications of neutron imaging and future possibilities

Neutron imaging applications exploit the power of neutrons to penetrate through metals and measure small concentrations of hydrogen and lithium with high sensitivity. Recent advances in digital ima...

Influence of temperature conditions of forming nanosized SnO2-based materials on hydrogen sensor properties

Semiconductor sensors are widely used to detect toxic and flammable gases, and nanosized SnO2 is usually applied as material for gas-sensitive layers of the sensors. Sensor nanomaterial has to provide appropriate value of the electrical resistance of the sensor in air and high sensor response to analyzed gas. Sol–gel synthesis is the most promising to obtain SnO2 nanomaterial because it enables to rich high chemical homogeneity of the obtaining material, to control its particle size and structure at different stages of the material synthesis. These characteristics of the nanomaterials have to determine the sensor properties. To obtain SnO2 sensor nanomaterial, synthesis of xerogel by a sol–gel method via SnCl4·5H2O dissolved in the ethylene glycol was carried out. To provide optimal values of the sensor electrical resistance in air, decomposition of the xerogel was studied by DTA–DTG analysis. This study was carried out by heating the xerogel to 1000 °C in air with heating rates of 2.5, 5 and 10 °C min−1. It was found that decomposition of the xerogel was performed in several stages: water desorption, removing ethanediol-1,2, HCl and CO2. Using the selected heating mode with isothermal holding at 280, 350, 390 and 600 °C, optimized SnO2 nanomaterial was obtained. It was found that sensors based on this material had suitable values of their electrical resistances (150–400 kΩ) and possessed high responses to very small concentration of hydrogen.

IMPROVED HYDROGEN DETECTION OF ISLAND TYPE PALLADIUM FILM — NANOPOROUS SILICON DIODE AT ROOM TEMPERATURE

An island type palladium film — silicon diode hydrogen sensor has been developed applying thin (15-75 nm) nanoporous silicon as an intermediate sensitive layer. Using a thermal Pd deposition into porous silicon allows to vary the size and morphology of the metal islands in the porous silicon matrix. The gas sensor behaviour under hydrogen exposure in mixture of 200 ppm- 10% H2 and dry synthetic (20%O2 +80 %N2 ) air was investigated by measuring the I-V characteristics. The diode current and sensor hydrogen sensitivity is shown to depend on the type of silicon substrate and the thickness of porous silicon. The current change versus hydrogen concentrations shows the linear law both for large and small hydrogen concentrations. At room temperature the sensor sensitivity is approximately 1 μA/100ppm, the response and recovery times lies in 1-8 min range.

Metrological Assurance of Measurement of Hydrogen Concentration in Metals – a Basis for Safety in the Oil and Gas Industry

It is demonstrated that metal properties depend strongly on both hydrogen concentration, and on its redistribution with respect to bonding energy. According to accident statistics presence of hydrogen within metal is in many cases the main reason for metal structure breakdown with occurrence of internal stresses. It is concluded that the lack of a single metrological hydrogen concentration measurement system makes it impossible to introduce extensively an effective and reliable method for production monitoring and accident prevention. Hydrogen is contained in all metals and alloys. In contrast to the majority of other alloy components, it has a very strong effect on material mechanical properties. The degree of the effect of small hydrogen concentrations on metal proper- ties may only be compared with phosphorus. The lack of necessary monitoring of hydrogen content in a metal promotes the task of measuring its concentration to a paramount category. According to statistics, in the last 30 years the reason for 62.7% of all bulk oil tanker accidents in our country was brittle failure, connected with hydrogen accumulation, and only 12.4% of accidents occurred as a result of ignition or explosions. The practice of studying operating vessels shows that their metal walls are often subject to deep pitting corrosion, as a consequence of which there is rapid local breakdown. At the boundary of an internal welded joint and wall surface, there is intergranular corrosion. Metal corrosion leads to hydrogen embrittlement for steel from which a vessel is manufactured. Hydrogen brittleness and wall delamination is one of the main reasons for the accident rate in main oil and gas pipelines. Due to a significant hydrogen concentration in raw oil and gas at sites it is necessary to prepare pipelines from special expensive grades of steel, but this only increases service life, and the problem of hydrogen brittleness is retained. The effect of hydrogen on metal properties has been studied for more than 150 years. Cases of hydrogen brittleness have been studied a great deal, and there are experimental data about a threshold hydrogen concentration with which it arises. As a rule, this is a very low concentration in the range 0.4-50 ppm. In addition, quantitative data do not fix a common standard and traceability of existing standards to a primary standard, and this leads to marked scatter of results with measurements in dif- ferent laboratories. Divergences comprise a factor from 0.2 to 2, and in the case of nanomaterials it reaches a factor of 500 (1). Contemporary measuring equipment, available on the market, differs considerably both with respect to the method for hydrogen extraction from a sample, and the recording principle. Measurements of hydrogen concentration in identical

Opto-chemical sensor system for the detection of H2 and hydrocarbons based on InGaN/GaN nanowires

We report on an all-optical sensor system that employs InGaN/GaN nanowires (NWs) as opto-chemical transducers. The NWs, grown by plasma-assisted molecular beam epitaxy on low-resistivity n-type Si (1 1 1) substrates, exhibit an efficient room-temperature photoluminescence (PL) that persists up to about 200 °C. After deposition of a thin (5 nm) catalytic Pt-film onto the NWs the PL intensity rises when the NWs are exposed to small concentrations of hydrogen and hydrocarbons. The gas response of the NWs was analyzed using an integrated sensor system with fiber-coupled excitation from a GaN-based power LED emitting at 365 nm and a fiber coupled photo multiplier tube for detection. With this setup, H2 concentrations as low as 200 ppb and C2H2 concentrations as low as 5 ppm could be detected when the transducers were operated at temperatures around 80 °C. This opto-chemical transducer principle is best suited for safety-critical applications where a reliable media separation is required.

Modeling the hydrogen material interaction as parametric instability of the continuum

AbstractThe hydrogen is contained in any material. Its concentration inside the materials leads to mechanical properties degradation. The two‐continuum model of solid allows one to describe the influence of small concentration of hydrogen on the mechanical properties of materials in terms of changing the bonding energy of the second continuum, the latter being responsible for the hydrogen concentration. The application of this model to fatigue task give the hydrogen concentration that are critical for material destruction. Such fatigue destruction has a nature of parametric instability during the cyclic redistribution of the hydrogen under the cyclic loading. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Bound water: Evidence from and implications for the dielectric properties of aqueous solutions

Broadband dielectric spectra of a variety of aqueous solutions are evaluated as to indications of water that may be considered bound. Static permittivity decrements due to depolarizing internal electric fields, from kinetic depolarization, as well as from dielectric saturation are discussed. The latter effect reflects the preferential orientation of water permanent dipole orientations within strong Coulombic field of small ions, especially multivalent cations. Such water may be considered bound even though rapid rotations around the orientation of the electric dipole moment are definitely possible and also a fast exchange of water molecules between the hydration region and the bulk may take place. Water exhibiting large dielectric relaxation times, as typical for regions with large local concentration of foreign matter, may also be named bound. However, no clear evidence for interaction energies exceeding the hydrogen bond energy of pure water has been found. Rather enhanced relaxation times at low water content reflect the small concentration of hydrogen bonding sites and thus low probability density for the formation of a new hydrogen bond. Potential interferences of the water relaxation with relaxations from other molecules or from ionic structures are mentioned briefly.

Determination of Hydrogen in Steel by Thermal Desorption Mass Spectrometry

AbstractHydrogen embrittlement has been observed since high‐strength steels have been produced in the nineteen thirties 1,2. Several different analytical methods have been developed to quantify the total and diffusible hydrogen in steel, but many aspects of hydrogen determination are still to be explored. Purely quantitative determination of hydrogen is not sufficient to fully characterize the steel regarding its resistance against embrittlement.Thermal Desorption Mass Spectrometry (TDMS) allows the investigation of hydrogen absorption and desorption mechanisms to characterize hydrogen traps in different kinds of steel microstructures. This provides valuable information for the development of new materials with a higher resistance against hydrogen embrittlement. Additionally, TDMS allows the quantitative determination of very small concentrations of hydrogen (<0.1 µg/g). Such low detection limits cannot be reached with other methods. Due to time‐consuming analysis and a rather complex construction, TDMS is usually not applied for hydrogen determination in German steel mills. The present work describes the development of a thermal desorption spectrometer at ThyssenKrupp Steel Europe AG by adapting a compact quadrupole mass spectrometer to a commercially available hot solid extraction analyzer, which has proven to be a simple and efficient solution for the determination of diffusible hydrogen in steel.

Bulk and interface properties of (Zn,Mg)O buffer layers sputtered in hydrogen-containing atmosphere

Sputtered (Zn,Mg)O buffer layers are one of the few promising options for completely dry and cadmium-free manufacturing of chalcopyrite-based solar cells. The performance of a heterojunction solar cell depends critically on the electrostatic charge contained in the interface. In chalcopyrite-based cells this charge can be influenced by redox treatments. In this work we have added hydrogen to the working gas when sputtering the buffer layer in an effort to optimize the interface charge. We report on the unexpectedly complex effects even at low hydrogen flow. They include a reduced deposition rate, significantly altered diffractograms and higher Mg/Zn-ratio in the film. X-ray photoelectron spectroscopy reveals the deposition of a thin layer of metallic zinc in the initial deposition stage which is not observed in the absence of hydrogen. Small hydrogen concentrations appear to be beneficial in terms of cell performance and reproducibility. However, higher concentrations typically cause a loss in blue response which indicates the formation of a homojunction buried within the chalcopyrite absorber.

Hydrogen absorption and desorption in a duplex-annealed Ti–6Al–4V alloy during exposure to different hydrogen-containing environments

Based on its excellent combination of a high strength/weight ratio and good corrosion behavior, Ti–6Al–4V alloy is ranked among the most important advanced materials for a variety of industrial applications. However, in many of these technological applications, this alloy is exposed to environments which can act as sources of hydrogen, and severe problems may arise based on its susceptibility to hydrogen embrittlement. Even small hydrogen concentrations might lead to failure. Consequently, a comprehensive knowledge of hydrogen's absorption/desorption behavior and interactions between hydrogen and different microstructural features is necessary to better understand the desorption and trapping mechanisms, the types of the trap sites, and the trapped hydrogen content, in order to determine the safe service conditions of this alloy in the industry. In this paper, different characteristics of hydrogen's absorption/desorption behavior and trapping in a duplex-annealed Ti–6Al–4V alloy are studied by means of thermal desorption spectroscopy (TDS). Spectra analysis is supported by data from a variety of other experimental techniques, such as LECO hydrogen determinator, XRD and microstructure investigations by means of optical and electron microscopy. Hydrogen evolution is found to be a very complex process, being affected by the way hydrogen was initially introduced to the alloy, the phase transformations that may occur during the thermal analysis and the presence of potential trapping sites.

Cluster-eliminating filter for depositing cluster-free a-Si:H films by plasma chemical vapor deposition

A cluster-eliminating filter is developed to reduce a volume fraction VF of amorphous silicon nanoparticles above approximately 1 nm in size (referred to as a cluster) incorporated into a-Si:H films. The filter reduces the VF value by using the difference between a sticking probability of clusters and a surface reaction probability of SiH3 radicals, which are the predominant deposition radicals. By employing the filter together with a cluster-suppressed plasma chemical vapor deposition reactor, the VF value is reduced below 1∕180 compared to that for the conventional device quality films. Such cluster-free a-Si:H films have an extremely small hydrogen concentration associated with Si-H2 bonds below 5.46×10−3at.%.

Isotopic Separation Analysis of Infinitesimal Concentrations of Hydrogen Using Trace Reduction Detector

A previously developed analyzer for detecting extremely small concentrations of hydrogen in air was evaluated by using it to distinguish hydrogen isotopes. The analyzer utilizes the functions of a gas chromatograph and an atomic absorption spectrophotometer and is based on the reduction reaction of mercuric oxide with hydrogen. Three test samples were used: gas mixtures containing both protium and deuterium with almost equal concentrations of about 5, 20, or 50 cm3/1000 m3 diluted in nitrogen. Each measurement was repeated more than 30 times, and chromatograms were obtained for each test sample. Examination of the chromatograms showed that the retention times for the protium and deuterium could be clearly distinguished. The retention times were virtually constant and indistinguishable, independent of the concentration and repetition time. The peak areas for the protium and deuterium were also stable, independent of the repetition time. Moreover, there was a clear linear relationship between the peak areas and concentrations for both elements. These results show that the analyzer can distinguish the two hydrogen isotopes and estimate concentrations of each as small as about 5 cm3/1000 m3. They also show that it may be possible to use the analyzer to monitor tritium concentrations.