Hydrogen Saturation Research Articles

Обоснование применения ёмкостей «Акваспектр» для насыщения водных сред активным водородом с использованием биохимического показателя суммарной антиоксидантной активности

The article presents the results of a biochemical study of aqueous environments with molecular hydrogen by antioxidant activity. Activated hydrogen has selective antioxidant activity against dangerous free radicals for the human body and animals. In addition, its anti-inflammatory, anti-apoptotic, anti-allergic properties were found and it stimulates energy metabolism in cells. This problem is currently relevant due to the great interest in activated hydrogen as an antioxidant over the past ten years, but its quantitative metabolic parameters have not yet been assessed at a sufficient scientific level. The total antioxidant activity of aqueous systems saturated with hydrogen was studied using coulometric analysis. It has been shown that their total antioxidant activity increases depending on the quality of aqueous media and the operating time of the “Aquaspectr Hydrogen Mug Mug for Activating Water” device: for Arkhyz mineral water, 20 times after 26 minutes of hydrogen saturation, drinking natural oxalis Kristalia with mineral drinking medicinal water DonatMg (in volume ratio) 31 times after 55 minutes and DonatMg mineral drinking medical water 44 times after 28 minutes. The total antioxidant activity was determined using electrically generated bromine, the samples were analyzed on a certified Expert-006 coulometer (Econix-Expert LLC, Russia) according to a certified method. In the work it was shown that saturation of water systems, in particular mineral and drinking water, by the method of hydrogen evolution on the surface of containers from environmentally friendly magnesium alloys, can be quite an effective way to activate various liquid media with antioxidants used in environmental medicine. In addition, our results can be useful in solving scientific and technical problems in the development of alternative energy sources.

ЕНЕРГОЗБЕРІГАЮЧІ ПАЛИВНІ ЕЛЕМЕНТИ З ВИКОРИСТАННЯМ ВОДНЯ

Performed research work to determine the effect on the fuel cells of the temperature and change the shape of the elements (plates) in contact with hydrogen. It has been confirmed that the plate change takes two stages. In the first short time step, the maximum form of plate change is achieved. The temperature-dependence of the maximum bending of the plate obeys the extreme law. In the second, substantially longer phase, the plate is straightened. At low temperatures, the residual stationary bending of the plate is 20-30% of the maximum bending value. With increasing temperature, the bending rate of the plate increases and at 320-350oS the phenomenon becomes completely reversible. The mechanism of changing fuel cell form is discussed. As a result of the study, the experimental regularities of the hydrogen-induced form of change of the palladium plate are established, it is determined that a temporary "metal-hydrogen" gradient material is formed at hydrogen saturation and hydrogen concentration stresses always arise. This, in turn, provides for efficient planning and determination of the time of penetration of hydrogen into the metal, controlling the shape change, and allowing the fuel cell to operate. It is determined that the maximum bending of the plate with increasing temperature changes according to the extreme law and in the temperature range 220-260oS the bending reaches the maximum value. It is shown that the maximum bending of the plate is determined by two fundamental properties of the Pd-H system, namely, the diffusion coefficient and the equilibrium solubility of hydrogen in palladium. The scientific novelty is the use of the known material palladium, which in contact with hydrogen becomes a temporary gradient alloy with variable physical properties. It is established that the heat exchange in the plate and the energy equilibrium around the plate are based on the velocity on the heat flux that occurs during reactions in the fuel cells and the heat losses that occur in the fuel cell. The practical importance of the work lies in the possibility of using the developed algorithm in practice in the manufacture of specific devices operating on the basis of a fuel cell - hydrogen, with the possibility of modeling this process in Matlab. But improving the working conditions of fuel cells and hydrogen sensors, because at low temperatures there is a relatively small residual bending of the plate, and accordingly the shape of the fuel cell.

Modeling and numerical simulation of a 5 kg LaNi5-based hydrogen storage reactor with internal conical fins

Hydrogen absorption by ~5 kg LaNi5 in a metal hydride reactor is simulated. A cylindrical reactor (OD 88.9 mm, Sch- 40s, SS 316) with internal conical copper fins and cooling tubes (1/4”, SS 316) carrying water at 1 m s−1 and 293 K (inlet) is considered. Designs with 10, 13 and 19 equi-spaced fins and 2, 4 and 6 cooling tubes are explored. Hydrogen (15 atm) is supplied through a coaxial metal filter (OD 12 mm, SS 316). Conical fins offer enhanced heat transfer through higher surface area and funnelling effect for efficient loading of metal hydride powder. 19 fins + 6 tubes design requires 290 and 375 s for 80% and 90% hydrogen saturation level, respectively. The fins near the water inlet regions are more effective as the water temperature is lower in these regions. Trade-off exists between times taken for saturation and the mass of metal hydride.

Influence of liquid composition on diffusive mass transfer in the lubricating film of Taylor flow—A study related to the hydrogenation of nitrobenzene

Micro-structured reactors operated in Taylor flow are promising for intensifying heterogeneously catalyzed gas-liquid reactions. By reaction progress or dilution, physical properties may change with liquid composition. Here, the effect of composition on physical mass transfer in the liquid film of Taylor flow is studied with regard to the hydrogenation of nitrobenzene to aniline. For the liquid mixtures nitrobenzene-aniline and nitrobenzene-ethanol, composition-dependent physical properties are determined using information from literature. By numerical solution of the unsteady one-dimensional diffusion equation with composition-dependent physical properties, the instantaneous hydrogen concentration across the liquid film is obtained for different nitrobenzene mole fractions. The results indicate that in a wide composition range of reactant (nitrobenzene) and product (aniline), hydrogen diffuses slower in the mixture than in pure liquids. On the other hand, dilution of nitrobenzene by ethanol increases hydrogen mass transfer in the liquid film. A theoretical relation is provided which allows estimating for given capillary number the necessary bubble length to achieve a certain hydrogen saturation in the liquid film during the passage of one Taylor bubble. This non-dimensional relation can be applied to other physical systems and may be useful to guide optimal hydrodynamic operation conditions for applications with Taylor flow in chemical engineering.

Monitoring the Changes in Titanium Defect Structure during Titanium Hydrogen Saturation

Hydrogen saturated samples of technically pure titanium have been studied by the electron-positron annihilation method (EPA), coupled with the thermoelectric power measurements performed in these samples saturated by different amount of hydrogen. The structure of the hydrogenated samples was additionally investigated by X-ray diffraction. The complete coincidence of the moment of occurrence of a change in the structure of hydrogenated titanium depending on the amount of introduced hydrogen has been established. The intensity of positron annihilation drops with increasing hydrogen concentration in α-titanium to 0.04 wt % and then remains unchanged up to values of 0.05 wt % ($$\alpha + \delta $$) -titanium to increases afterwards. At the same time, a sharp change in the values of the thermoelectric power occurs in this range. In the region of 0.05%, the annihilation rate stabilizes and begins to increase, while the thermoelectric power begins to decrease slowly. The inflection point on the dependence of thermoelectric power on hydrogen concentration corresponds to the onset of the formation of titanium $$\delta $$-hydrides. An increase in the positron lifetime is observed in the concentration range of 0.05–0.08 wt %, then the lifetime stays stable up to concentrations of 0.08–0.12 wt %. A transition from ($$\alpha + \beta $$) to ($$\alpha + \delta $$) phase is formed in this range. Next, the positron lifetime increases, as does the number of defects, while the thermoelectric power gradually drops (to a concentration of 0.24 wt %). This is followed by a stabilization mode of all the above parameters to 0.35 wt %.

Cold Cracking Resistance of Butt Joints in High-Strength Steels with Different Welding Techniques

Investigation results are presented to improve the structural strength (cold crocking resistance) of weld joints in high-strength steels with the yield limit over 600 MPa. The effect of arc, laser, and hybrid laser-arc welding conditions on the weld metal structure and diffusion hydrogen saturation of build-up and fused base metals was experimentally studied. The diffusion hydrogen saturation of build-up (arc and hybrid welding) and fused (laser welding) metals was chromatographically examined. In gas-shielded arc welding, the diffusion hydrogen content in the fused base metal was shown to be limited to the concentration that does not exceed 0.4 ml/100 g due to an increase in the welding speed from 18 to 50 m/h. In laser and hybrid laser-arc welding of high-strength steels with the yield limit over 600 MPa, the diffusion hydrogen content in the fused metal makes up 0.07 and 0.2–0.3 ml/100 g, respectively, regardless of the welding speed. The cold cracking resistance was evaluated by a commonly accepted procedure of special reference butt samples. Optical and transmission microscopic studies permitted of revealing the effect of arc, laser, and hybrid laser-arc welding conditions on the weld metal structure and gaining detailed information on the dislocation density distribution. The relation between the level of local internal stresses and the structural factors of dislocation density distribution in the weld metal was established. In arc and laser welding, local internal stresses were shown to be reduced to the values that do not exceed 0.22 of the theoretical metal strength if the welding speed would make up 50 m/h. In hybrid laser-arc welding at 72–110 m/h, maximum local internal stresses are also less than 0.22 of the theoretical metal strength. An increase in the cold cracking resistance in butt weld joints of high-strength 14KhGN2MD and N-A-XTRA-70 steels was established to be reached due to a low concentration of diffusion hydrogen in fused metal and formation of the fine-grained structure of lower bainite with the uniform dislocation density distribution.

Phenomenon of skin effect in metals due to hydrogen absorption

Experimental studies of the distribution of hydrogen in metal samples after a standardized saturation procedure in a neutral solution are described. It is shown that the hydrogen concentrates in a thin surface layer which plays the role of a shield for the further propagation of hydrogen. We refer to this phenomenon as a skin effect in the hydrogen saturation since the internal regions of the metal are not saturated by hydrogen. A review of similar experimental results for other standardized methods for saturation of metals with hydrogen (cathodic polarization, saturation in gaseous hydrogen) is provided, and the universal nature of the skin effect for metals is shown. The analysis of mechanisms of the skin effect is carried out by methods of continuum mechanics based on a bi-continual model of a solid. The problem of saturating a metal sample with hydrogen without external load is posed. It is shown that the model taking into account the mutual influence of hydrogen and mechanical stresses allows one to obtain solutions describing the highly non-uniform distribution of hydrogen at standardized saturation.

The effect of diffusion-mobile and combined hydrogen on hydrogen brittleness of steel

Diagnostics of the emergencies attributed to the pipeline destruction resulted from hydrogen charging and corrosion is one of the important problems of the oil and gas industry. Corrosion and hydrogen charging of the metal lead to formation of holes in the pipe wall at a certain critical ratio of the metal strength and thickness resulted from the impact of the internal pressure of the gas transported through the pipeline. Despite extensive research, many issues related to this problem require further consideration. This concerns, in particular, the issues regarding kinetics of the brittle fracture of metal of the pipeline walls and the role of diffusion-mobile (active) and combined (bound) hydrogen in this process. Electrochemical hydrogenation (saturation) of cylindrical steel samples revealed that the zone of penetration of electrolytic hydrogen match the region of the cleavage crack origin, i.e., the area of the subsurface hydrogen distribution can be considered a local area of micro-cleavage in the peel tests thus making possible the study of kinetics and concentration dependences of steel brittle fracture under the impact of both diffusion-mobile and combined hydrogen, i.e., under conditions of reversible and irreversible hydrogen brittleness. The dependences of the peel resistance (micro-cleavage) on the concentration of diffusion-mobile (active) and bound hydrogen in the micro-cleavage zone are obtained as a result of kinetic studies. Electron-fractographic study of fractures of 18KhGMF steel samples showed that fracture morphology changes in accordance with the stages of brittleness development. The initial ductile fracture is followed by a typically brittle peeling at reversible brittleness. Then, with the development of irreversible fragility, a mixed character of destruction is observed. The obtained three-stage dependence of the peeling strength, taking into account different hydrogen states, proves the different physical nature of the processes at different stages of hydrogen brittleness and connects the known reversible and irreversible hydrogen brittleness with the effect of diffusion-mobile and bound hydrogen, respectively.

Effect of AlN coating on hydrogen permeability and surface structure of VT6 alloy by vacuum arc ion plating**Project supported by the China Scholarship Council.

We study the absorption of hydrogen of metal by the permeability method. With the help of the gas reaction controller (GRC), the absorptive capacity of hydrogen, which is a function of time, temperature and pressure, can be recorded. The effect of the performance of the hydrogen permeability of AlN coating on the titanium alloy surface structure is studied. In the research, the AlN is selected to be added to the titanium alloy sample VT6, and the properties of the titanium alloy are investigated, and the hydrogen absorption rate of the coating is calculated by performing the hydrogen saturation of the test sample. The results show that under 600 °C the AlN film reduces the hydrogen absorption rate of titanium alloy and improves the surface properties of VT6 alloy.

Experimental study on transient response of fuel cell

This research work discusses a control strategy to enhance the transient response of the fuel cell and boost the real and reactive power flow from grid connected to fuel cell. The current output of the fuel cell depends on the availability of hydrogen in the fuel cell stack, a battery bank is implemented to supply the transient current and to prevent it from hydrogen saturation. The battery should only supply when there is a transient. During steady state the total power is produced by the fuel cell by regulating its hydrogen input. A prototype of the system will be created to study a control scheme which regulates the current from an input source and a battery which is connected to a dc motor. The control philosophy is based on d-q transformation and subsequently generating a reference signal that is tracked by an IGBT based inverter. The speed of the motor is controlled using pulse with modulation. The dynamic modeling of the standalone fuel cell that is connected to a dc motor is carried out using MATLAB/SIMULINK platform. The simulation results show that the control scheme works well, although the dynamic response of the system can be improved. The testing carried on the prototype proves that the concept works well, but a hydrogen control scheme should be developed to improve the efficiency of the control scheme.

Experimental study on transient response of fuel cell

This research work discusses a control strategy to enhance the transient response of the fuel cell and boost the real and reactive power flow from grid connected to fuel cell. The current output of the fuel cell depends on the availability of hydrogen in the fuel cell stack, a battery bank is implemented to supply the transient current and to prevent it from hydrogen saturation. The battery should only supply when there is a transient. During steady state the total power is produced by the fuel cell by regulating its hydrogen input. A prototype of the system will be created to study a control scheme which regulates the current from an input source and a battery which is connected to a dc motor. The control philosophy is based on d-q transformation and subsequently generating a reference signal that is tracked by an IGBT based inverter. The speed of the motor is controlled using pulse with modulation. The dynamic modeling of the standalone fuel cell that is connected to a dc motor is carried out using MATLAB/SIMULINK platform. The simulation results show that the control scheme works well, although the dynamic response of the system can be improved. The testing carried on the prototype proves that the concept works well, but a hydrogen control scheme should be developed to improve the efficiency of the control scheme.

Low-temperature cementation – perspective technology of hardening of toothed parts

The structure, properties and geometrical accuracy of gear wheels after chemical heat treatment which cementation was carried out at 930°C and 870°C are investigated. Advantage of low-temperature cementation of toothed parts in size of a radial runout, fluctuation of a side clearance, ovality of an internal opening and the area of a spot of contact between teeths of the strengthened gear wheels is shown. Influence of structure of the endothermic atmosphere on mechanical properties and intensity of saturation by carbon steel 15HGN2TA and 20HGNMTA is investigated. It is established that increase in content of hydrogen from 20% to 40% in the endoatmosphere increases saturation speed carbon steel by 10 – 34%, excludes their hydrogen saturation and keeps indicators of mechanical properties of the cemented parts. The technology of chemical heat treatment of toothed parts including cementation at 870°C in the endothermic atmosphere containing 40% of hydrogen in the structure is developed and recommended for application.

Developing an Acoustic Method for Determining the Degree of Hydrogenation in Structures Made of Titanium Alloys

We present results of acoustic studies of hydrogenated samples of PT-7M and PT-3V titanium alloys, aimed at establishing correlations between acoustic parameters and the mass fraction of hydrogen in the samples. Relevant metallographic studies have been carried out, which make it possible to describe the nature of structural changes occurring under hydrogen saturation. The transition to an embrittled state in the alloys under study has been demonstrated by microhardness measurements.

Orbitrap molecular fingerprint of dissolved organic matter in natural waters and its relationship with NDMA formation potential

N-nitrosodimethylamine (NDMA) is a disinfection byproduct that has been classified as probable human carcinogen by the US Environmental Protection Agency. According to the published literature, natural dissolved organic matter (DOM) can be a source of NDMA precursors in drinking water. New advances in chemical characterization of DOM with high resolution mass spectrometry (HRMS) are allowing researchers to understand these ultra-complex mixtures.The objective of this study is to investigate analytical methodologies based on HRMS to explore NDMA formation from natural waters. To this aim, different waters from drinking water reservoirs in Spain containing NDMA precursors (quantified by means of NDMA formation potential) in concentrations between 17 and 60 ng/L have been studied. The workflow includes DOM solid-phase extraction and Orbitrap analysis with and without chromatographic separation.Here, we show that the molecular composition of DOM across the studied drinking water reservoirs is correlated with the NDMA formation potential. In particular, we found that NDMA formation potential is associated with compounds with high hydrogen saturation (H/C ≥ 1.5), corresponding also to reservoirs with higher background nutrient concentrations and wastewater indicators. Further chromatographic fractionation did not allow better definition of these possible precursors as they were present in different fractions of the chromatogram, suggesting that they were isomerically complex.

Simulation of Hydrogen Isotopes Accumulation Processes in Materials in the Presence of Chemical Traps

The accumulation of hydrogen inside a solids occurs in traps of a different nature. The following things are known in addition to finding hydrogen in interstitial sites: dislocation mechanisms of hydrogen storage, micropores and microcracks, sorption on the free surface of microdefects, chemical traps with the formation of hydrides and other compounds, both with matrix material and with impurities or components of alloys. It is established that each type of trap has its own binding energy of hydrogen, which can vary from 0.2 eV for hydrogen gas in microdefects to several eV for hydrogen chemically bound in traps. Measurements of the distribution of hydrogen concentration dissolved in a solid body over binding energies provide a clue as to the understanding of hydrogen impact on mechanical properties and to the development of technologies for controlling the materials properties during their production and operation. The paper presents the results of simulation experiments on hydrogen saturation of materials in the presence of chemical traps. The proposed model, based on the numerical solution of the diffusion equation in the presence of irreversible capture, made it possible to describe the absorption process and determine the activation energies of hydrogen interaction with the material.

Identifying the Role of Dynamic Surface Hydroxides in the Dehydrogenation of Ti-Doped NaAlH4.

Solid-state metal hydrides are prime candidates to replace compressed hydrogen for fuel cell vehicles due to their high volumetric capacities. Sodium aluminum hydride has long been studied as an archetype for higher-capacity metal hydrides, with improved reversibility demonstrated through the addition of titanium catalysts; however, atomistic mechanisms for surface processes, including hydrogen desorption, are still uncertain. Here, operando and ex situ measurements from a suite of diagnostic tools probing multiple length scales are combined with ab initio simulations to provide a detailed and unbiased view of the evolution of the surface chemistry during hydrogen release. In contrast to some previously proposed mechanisms, the titanium dopant does not directly facilitate desorption at the surface. Instead, oxidized surface species, even on well-protected NaAlH4 samples, evolve during dehydrogenation to form surface hydroxides with differing levels of hydrogen saturation. Additionally, the presence of these oxidized species leads to considerably lower computed barriers for H2 formation compared to pristine hydride surfaces, suggesting that oxygen may actively participate in hydrogen release, rather than merely inhibiting diffusion as is commonly presumed. These results demonstrate how close experiment-theory feedback can elucidate mechanistic understanding of complex metal hydride chemistry and potentially impactful roles of unavoidable surface impurities.

Correlation of acoustoelasticity with hydrogen saturation during destruction

The surface effect of acoustic anisotropy in steel and aluminum industrial alloys was experimentally detected. Changes in the integral value of acoustic anisotropy in 10–15 times were observed after removing the surface layer with a thickness of 100 microns in steel specimens and 250 microns in aluminum specimens. The correlation between distributions of acoustic anisotropy and hydrogen concentrations in surface layer of specimens was found. It was suggested that the surface effect of acoustic anisotropy occurs due to the influence of microcrack systems localized in a surface layer of metal. This result can be used to improve existing approaches to estimating of corrosion damage, fatigue, mechanical stresses and plastic deformations of technical structures by using acoustic anisotropy.

Hydrogen assisted crack initiation and propagation in nickel-cobalt heat resistant superalloys

It has been investigated the Ni-Co alloys (obtained from powder 0.1...0.3 mm under hot gaseous (in argon) isostatic pressure (up to 300 MPa) (Ni60Co15Cr8W8Al2Mo3) (Firth Rixon Metal Ltd, Sheffield) and deformed (obtained by vacuum induced remealting) materials (Ni62Cr14Co10Mo5Nb3Al3Ti3) for gaseous turbine discs. Investigation has performed in the range of temperature 25…800°С and hydrogen pressure up to 70 MPa. By the 3D visualization of crack morphology it has been discovered the structure of fatigue crack surface and established the refer points on crack path, including the boundary between the matrix and intermetallic particles (400×200 μm), crack opening, structural elements distributions on the surface for selection of next local areas for more precision fracture surface and TEM examinations. Hydrogen influence on cyclic crack resistance parameters appears in the decreasing of loading cycles number (with amplitudes 15 MPa) in hydrogenated specimens of both alloys and increase with hydrogen concentration. At the highest hydrogen saturation regimes of Ni60Co15Cr8W8Al2Mo3 alloy (800°С, 35 MPa Н2, 36 hours, СН = 32.7 ppm) number of cycles, which necessary for crack initiation is 3 times less in comparison with specimen in initial state. At crack initiation step in hydrogenated Ni56Cr14Co15Mo5Al3Ti3 alloy it has been established that before intermetallic inclusion (400×200 μm) local stresses increased, after its passing – has decreased. By fracture surface investigation it has been found the micro cracks up to 40 μm. Thin structure of heat resistant superalloys has characterises by disperse phase agglomeration with dimensions from 5 to 30 nm and crack propagation has a jumping character with no less then 50…70 nm steps.

Wall conditioning throughout the first carbon divertor campaign on Wendelstein 7-X

Controlling the recycling of hydrogen and the release of impurities from the plasma facing components proved to be essential and challenging throughout the first divertor campaign on W7-X. This paper discusses the conditioning requirements throughout the first divertor campaign on Wendelstein 7-X. Baking at 150 °C and glow discharge conditioning (GDC) in H2 is performed after the initial pump down of the vacuum vessel. Experimental programs in hydrogen are interlaced with He discharges to desaturate the wall from hydrogen, recover good recycling conditions and hence establish plasma density control. Optimized He ECRH wall conditioning procedures consisted of sequences of short discharges with fixed duty cycle. He-GDC remained however needed before each experimental day to fully offset the hydrogen inventory build-up. A significant increase in the divertor temperature is observed throughout an operational day, enhancing outgassing of CO and H2O. Preliminary recombination-diffusion modelling of hydrogen outgassing suggests enhanced diffusion to deeper surface layers with increasing wall temperature, which results in better wall pumping. This indicates that the experienced plasma performance degradation throughout an operational day results from increased impurity outgassing at higher wall temperature rather than hydrogen saturation of the wall.

Research of the effect of bias voltage on the morphology, structure and lattice spacings of the Nb coatings deposited by inverted magnetron

Using the metallography and X-ray diffraction analysis the effect of the bias voltage on the substrate on the structure, morphology, texture, and lattice parameters of Nb coatings deposited by an inverted cylindrical magnetron has been investigated. It is shown that the coatings are characterized by increased lattice spacings compared with pure niobium, which can be associated with both oxygen and hydrogen saturation and the presence of compressive residual stresses.