Small Amount Of Hydrogen Research Articles

Over-the-Gap Conductance Oscillations in Superconducting Vanadium Nanocontacts Induced by Hydrogen Impurities.

We have investigated the current-voltage (I-V) characteristics of Josephson junctions made by a low-temperature superconductor of vanadium (V) with a small amount of hydrogen (H) and deuterium (D) impurities using a mechanically controllable break junction (MCBJ) technique. Below the superconducting transition temperature TC, the differential conductance dI/dV spectra show distinct peaks within the superconducting gap, known as the subgap structure, which result from multiple Andreev reflections in pure V nanocontacts. Additionally, the H and D impurities in V nanocontacts induce several new conductance peaks outside the gap, referred to as an over-the-gap structures (OGSs). We found that the OGS peaks exhibit strong temperature dependence until the temperature is close to TC and follow the gap function predicted by BCS theory. When the contact diameter is changed at low temperature using the MCBJ technique, the OGS anomalies change almost linearly with the inverse of the contact diameter. In addition, the gap anomalies are significantly shifted outward by changing the positions of the H atoms through application of a high bias voltage between the contacts. The above features suggest that the OGS peaks are caused by the superconducting quasiparticle interference induced by H or D impurities and/or inhomogeneous structures in the nanocontacts.

Computational studies of hydrogen post-injection in direct-injection natural gas engines

The impact of using a hydrogen (H2) post-injection on combustion emission characteristics in a glow plug (GP) assisted direct-injection natural gas (DING) engine was investigated in this paper. This study was conducted by using the KIVA-3V code integrated with a detailed kinetic chemical model and a modified phenomenological soot model. Previous studies have indicated two sources of unburned methane (CH4) and soot particles in such an engine, namely the injector sac volume and the glow plug shield. The emissions were reduced in previous work by improving the shield design. However, the contributions from the injector sac volume were not solved. In these simulations, a small amount of hydrogen was injected following the major injection of natural gas (NG), and the unburned CH4 was pushed out of the injector into the combustion chamber. The injected hydrogen then affects the chemical reactions to form more hydroxyl (OH) radical, and the unburned methane from the sac volume and that originally left in the combustion chamber were oxidized to reduce its final value, compared to the baseline NG only case. As well, the soot particles contributed from the glow plug shield and from the injector sac volume and thereby the total particle emissions were reduced, compared to the baseline case. The reduction is due to the additionally formed OH which reduces the soot precursor acetylene (C2H2) and enhances the soot oxidation. The hydrogen post-injection also highly affected the CO–CO2 reaction, leading to more carbon monoxide (CO) and less carbon dioxide (CO2) emissions in the DING engine. In addition, more simulations were conducted by injecting different amounts of hydrogen fuels, and the emission values were generally changed as expected. The simulations also indicated that there is a minimum requirement for the hydrogen amount, below which the formed OH radical is not enough to oxidize the soot caused by the unburned CH4 from the injector sac volume, compared to the NG only case.

Energy Saving and Pollutant Emission Reduction by Adding Hydrogen in a Gasoline-fueled Engine

Pollution reduction related to combustion engines is considered to be an important issue around the world. Hydrogen as an additive energy has been utilized for alternative fuel since it need not require any modification. Particularly, it has been considered as a sustainable option for diminishing petroleum dependence and air pollutant emissions. In this study, we investigated the tailpipe emission with hydrogen addition for different driving behavior such as cold-start, idle, urban (UDC) and extra-urban (EUDC) under New European Driving Cycle (NEDC). The results showed that urban driving could attribute the most emissions in comparison to the high speed mode. Hydrogen addition enhanced the combustion process and the average reduction rates were observed 21.6% and 65.8% for hydrocarbon (HC), 2.37% and 85.4% for carbon monoxide (CO), and 7.53% and 59.3% for nitrogen oxides (NOx) when run at UDC and EUDC, respectively. The wide flammability of hydrogen ensures a homogeneous fuel-air mixture for complete combustion and reduces the HC, CO and NOx emissions. It is noteworthy that starting with less amount of hydrogen could greatly decrease HC followed by CO and NOx. Compared to conventional gasoline (G0), the average fuel consumption was reduced by 1.3% when a small amount of hydrogen was applied as an additive fuel.

Degradation caused by self-multiplication of damage induced by an interplay between hydrogen and the martensite transformation in a Ni–Ti superelastic alloy

ABSTRACT The role of damage in the degradation of tensile properties related to a stress-induced martensite transformation in a hydrogen-charged Ni–Ti superelastic alloy has been investigated. By damage, we mean vacancy clusters and dislocation structures induced in advance by a dynamic interplay between hydrogen and the martensite transformation. To homogenise the hydrogen concentration, the specimen was aged at room temperature after charging with a small amount of hydrogen (approximately 30 mass ppm). In this case, no fracture occurs within 2000 cycles during a cyclic tensile deformation test in the stress plateau region generated by stress-induced martensite and reverse transformations. With this hydrogen concentration, cyclic interplay between hydrogen and the martensite transformation scarcely leads to the degradation of tensile properties. Nevertheless, following cyclic martensite transformations before aging that induces pre-damage, fracture occurs after around 1000 cycles under a cyclic tensile deformation test despite the hydrogen concentration being the same. The present results clearly indicate that pre-damage induced by hydrogen affects the subsequent transformations, thereby causing the self-multiplication of damage, which degrades the tensile properties.

From dry to damp and stiff mantle lithosphere by reactive melt percolation atop the Hawaiian plume

Predicting the incorporation of hydrogen (H) in the atomic structure of upper mantle minerals is a major target in geodynamics since hydration impacts essential physico-chemical properties such as the melting temperature or viscosity. Here we quantify the hydrogen concentration in olivine and pyroxenes in nine mantle peridotites from Pali (Oahu island, Hawaii), which experienced variable degrees of reactive melt percolation leading to refertilization and olivine recrystallisation. Hydrogen concentration is quantified using Fourier transform infrared spectroscopy with unpolarized and polarized light. Despite important contamination by H2O-bearing and CO2-bearing melt/fluid inclusions, quantitative analysis of H in olivine was successful in all samples. Quantification of H concentration in orthopyroxene was successful in most samples, excepted the two most reacted peridotites. Olivines are very H-poor (0-5 ppm H2O wt, on average 0.8 ppm H2O wt) and orthopyroxenes contain very small amounts of hydrogen (4 to 44 ppm H2O wt, on average 19.5 ppm H2O wt). The hydrogen concentration in clinopyroxene could not be quantified due to ubiquitous water-derived species trapped at the interfaces with spinel exsolutions and in hydrous melt inclusions. Despite low concentrations, H and Al in orthopyroxene are positively correlated, but comparison with a database encompassing pyroxene from peridotites from different geological settings shows that variations in degree of melting/type of metasomatism may totally overcome the crystallographic-control of Al on H incorporation. The whole-rock hydrogen concentrations estimated based on the FTIR data (2-26 ppm H2O wt) are among the lowest in the current database for the mantle lithosphere (average at 150 ppm H2O wt). The hydrogen concentration in orthopyroxene is positively correlated with both the recrystallized olivine fraction and the pyroxene mode, indicating that the reactive melt percolation is responsible for the limited hydration of the Pali peridotites. However, as this metasomatism did not hydrate the olivine, it did not induce mechanical weakening of the oceanic mantle lithosphere.

Thermoelectric properties of Cu2Se sintered in high-pressure H2 or N2 atmosphere

For practical application in thermoelectric modules, thermoelectric materials need to be manufactured into legs with high-density. However, during the process of hot-pressing or spark plasma sintering, sublimation and instability of the materials especially for Te and Se-based compounds requires to be considered. In this work, Cu2Se were prepared by high-hydrogen/nitrogen–pressure sintering technology. High-pressure atmosphere inhibited the volatilization of Se, enabling formation of single-phase high-density Cu2Se bulk materials. Moreover, characterization results of X-ray diffraction, differential scanning calorimetry and thermal gravimetric analyses show that small amount of hydrogen and nitrogen atoms can be incorporated into the lattice of Cu2Se, lowering the thermal conductivity to 0.7–0.8 Wm−1K−1 compared with 1.1 Wm−1K−1 for the counterpart Cu2Se. A maximal figure of merit value of 0.25 at room-temperature was obtained for Cu2Se via sintering in 18 MPa hydrogen at 400 °C. Our high-pressure sintering approach may open a new route for shaping volatile materials into dense thermoelectric legs.

Obtaining particles with the structure Mg@C and (Mg@C)@Pd, their properties and stability in the hydrogenation/dehydrogenation processes

In this work, we studied the change in the properties of powders with a core (magnesium) – shell structure (carbon and carbon/palladium) in the process of hydrogenation/dehydrogenation with hydrogen (99.995 wt%). Magnesium powders were obtained by plasma chemical synthesis in an atmosphere of argon containing a small amount of hydrogen (2–3 at.%) and nitrogen (8–9 at.%), when performing a low-frequency arc discharge between a tungsten electrode and a magnesium melt. The shell (carbon and carbon/palladium) was deposited in a plasma generator with vortex and magnetic stabilization. For all samples, a decrease in the sorption capacity of hydrogen was observed as a result of successive cycles of sorption and desorption reactions. It was found that the reason for this fall is associated with the formation of the MgO and Mg(OH)2 phase, which prevents the diffusion of hydrogen. The carbon shell provides a more complete hydrogenation of the magnesium particles, and an additional palladium shell increases the resistance to cyclic hydrogenation/dehydrogenation and reduces the temperature of these processes. According to the data obtained, powders with particles (Mg@C)@Pd can absorb the largest amount of hydrogen (6.9 wt%) for the duration of 5 cycles, after which the protective shell of the particles begins to collapse and a loss of sorption capacity is observed.

Hydrogen-induced marginal growth model for the synthesis of graphene by arc discharge

High-quality graphene is prepared by arc discharge with low cost under hydrogen atmosphere. However, the growth mechanism of graphene synthesis by arc discharge remains unclear. In this paper, the hydrogen-induced marginal growth (HIMG) model is deduced to study the growth mechanism of graphene by combining experiment with numerical simulation results. First, the characteristics of thick edges and thin middle and containing hydrogen are verified by transmission electron microscopy and Raman spectroscopy, respectively. In addition, numerical simulation provides the chemical species and temperature range of graphene growth. Second, the marginal growth pattern of hydrogen transfer and carbon addition is introduced because the C-H and C-C reduce configuration energy and island energy, respectively. Meanwhile, the stacking growth at the margin of the graphene island leads to the longitudinal growth of graphene because of the Van der Waals force and the effect of self-assembly, increasing the number of graphene layers. Finally, graphene sheets with a small amount of hydrogen are deposited on the inner wall after annealing. The investigation of the growth mechanism of graphene under hydrogen atmosphere lays a foundation for the large-scale preparation of graphene by arc discharge.

Editors’ Choice—Power-Generating Electrochemical CO2 Scrubbing from Air Enabling Practical AEMFC Application

Anion exchange membrane fuel cells (AEMFCs) have been widely touted as a low-cost alternative to existing proton exchange membrane fuel cells. However, AEMFCs operating on air suffer from a severe performance penalty caused by carbonation from exposure to CO2. Many approaches to removing CO2 from the cathode inlet would consume valuable energy and complicate the systems-level balance-of-plant. Therefore, this work focuses on an electrochemical solution where CO2 removal would still generate power, but not expose an entire AEMFC stack to carbonation conditions. Such a system consists of two AEMFCs in series. The first AEMFC, which acts as an anion exchange CO2 separator (AECS), is relatively small and serves to scrub CO2 from the air. The AECS is powered by the hydrogen bleed from the second (i.e., main) AEMFC. A small amount of hydrogen is bled from the recycled hydrogen used in the main AEMFC to mitigate impurity build-up, including nitrogen gas from diffusion across its membrane. The second, main AEMFC operates on the purified air output from the AECS and fresh H2. This work shows that it is possible to use an AECS to lower the CO2 concentration in the AEMFC input air stream to values low enough that the main AEMFC can be operated stably for extended periods, 150 h in this demonstration. Also, in this study, AEMFCs are operated on AECS-purified air without experiencing a performance penalty. Lastly, the relative geometric active area of the AEMFC and AECS devices are evaluated and discussed.

Local hydrogen accumulation after cold forming and heat treatment in punched advanced high strength steel sheets

Hydrogen embrittlement is one of the most crucial problems in the application of advanced high strength steel (AHSS) sheets for the automotive industry. Especially, the severe plastic deformation in punched edges makes the components susceptible to hydrogen assisted cracking (HAC). While small amounts of hydrogen are measured in the bulk material, hydrogen concentration increases in the micrometer-sized shear affected zone many times, along with severe plastic deformation. To contribute to the understanding of local microstructure and local stress states on the hydrogen accumulation in the shear affected zone, two industrial AHSS were investigated. Both steels had the same ultimate tensile strength of 1200 MPa, but different uniform elongations. High-pressure torsion (HPT) deformed samples were used to represent the material state in the shear affected zone. Thermal desorption spectroscopy (TDS), X-ray diffraction (XRD), magnetic retained austenite measurements and electron backscattering diffraction (EBSD) in a high resolution secondary electron microscopy (SEM) were applied among other techniques to gain more insights with microstructural resolution. The hydrogen analysis results of the HPT samples were correlated with the local hydrogen trapping capacity in punched edges. Finally, a simplified “two-zone” model considering the bulk and punched edge as separate zones was developed in order to estimate the local hydrogen concentration of punched AHSS sheets as a function of hydrogen bulk concentration. In a concluding remark it is shown, that the effect of the hydrostatic stress field as trap site is negligibly small compared to other traps.

A journey of wastewater to clean hydrogen: A perspective

A journey of wastewater to clean hydrogen: A perspective

A comprehensive study of a reactivity-controlled compression ignition engine fueled with biogas and diesel oil

Reactivity-controlled compression ignition (RCCI) engines have been introduced as a promising alternative to compression ignition engines, especially in reducing emissions. It is common practice in an RCCI engine to use two fuels with distinctly different reactivity to control the combustion process. Also, abundant biogas fuel could be considered as a potential and suitable alternative to conventional fuels. Biogas can easily be derived from renewable resources and is basically composed of methane (CH4), carbon dioxide (CO2), a small amount of hydrogen (H2), nitrogen (N2), oxygen (O2) and hydrogen sulfide (H2S). In this paper, biogas as an alternative fuel together with diesel oil is used for reactivity-controlled compression ignition in a modified heavy-duty engine. The biogas fuel with low reactivity is fed through the inlet port and diesel oil with high reactivity directly injected into the engine cylinder. Then, a detailed study of biogas composition, engine speed, intake temperature, fuel metering and injection strategies on combustion characteristics such as engine efficiency and emission levels is carried out. It is demonstrated that the amount of CO2 in biogas composition plays a significant role in combustion and emission processes. Typically, at IMEP = 9.4 bar, as the amount of CO2 in biogas composition is changed from 0 to 40%, the maximum in-cylinder temperature and pressure are reduced about 143 K and 4.6 bar, respectively, while NOx emission is reduced drastically by 75%.

Effect of hydrogen on vacancy diffusion

Although it is widely recognized that even small amounts of hydrogen (H) can cause embrittlement in iron (Fe) and in (high-strength) steels, the fundamental mechanisms that cause it are not yet completely understood. To contribute to a better understanding of the behavior of H in metals, we use parallel replica dynamics (PRD) to study the effect that different amounts of atomic H have in the diffusion of a single vacancy in body-centered cubic (BCC) Fe. Using PRD we calculate the diffusion of H-vacancy complexes at temperatures and timescales that are not reachable using classical methods. Additionally, based on the PRD results and calculations of the minimum energy paths of migration, we propose a mechanism for the migration of vacancy-H complexes and formulate an analytical model for the calculation of their joint diffusivity.

Improvement of drilling performance by overcoating diamond-like carbon films on diamond-coated drills for carbon fiber reinforced plastics processing

The hardness and hydrogen content of diamond-like carbon (DLC) films vary depending on the film deposition methods and conditions. Carbon fiber reinforced plastics (CFRP), known as hard-to-machine materials, have been widely used for industrial aircrafts that require structural materials. In this study, the effects of the hardness and hydrogen content in DLC films on the drilling performance of CFRP drills were investigated. Various DLC films, prepared using the T-shaped filtered arc deposition method, were used to coat diamond-coated drills for CFRP processing. The drilling test of the CFRP plates revealed that the occurrence of burrs was suppressed using the drill coated with a hard DLC film containing small amounts of hydrogen, classified as a hydrogenated tetrahedral amorphous carbon (ta-C:H) film. The spherical polishing test of the CFRP plate using DLC-coated balls demonstrated that the DLC films containing hydrogen suppressed the adhesion of the resin material constituting the CFRP. The coating of hard DLC films containing small amounts of hydrogen, such as a ta-C:H film, significantly improved the drilling performance of diamond-coated drills for CFRP processing. The performance improvement of CFRP drills expands the range of CFRP processing conditions.

Maximizing HBr/Br2 in the flue gas and prevention of secondary pollution during the oxy-combustion of brominated waste electrical and electronic equipment part 1- thermodynamic considerations

Organobromine compounds comprise between 3 and 8% by weight of WEEE and mainly converted to HBr and Br2 in the incinerator. However, these compounds, during the cooling of the flue gases, can form the PBDD/Fs in the post-combustion area of the furnace. Due to the many benefits of Oxy-combustion process, our group has developed a fluidised bed incinerator for burning the WEEE and plan to maximise HBr/Br2 in the flue gas. Experimental results presented in the recent papers show that the combustion of the WEEE particles attains quickly to thermodynamic equilibrium. Thermodynamic modelling can, therefore, predict the concentration of brominated pollutants, particularly HBr, Br2, HgBr2, and Br˙ in the flue gas. In this paper, the effect of various parameters for increasing the HBr/Br2 ratio in the flue gas has been investigated. The model shows that the addition of very small amounts of hydrogen in the post-combustion area can convert Br2 and Br˙ into HBr.

Very thin carbon-based films for transmissive photocathodes

Very thin carbon-based nitrogen-doped films of different thicknesses were deposited on double-side polished sapphire substrates by RF reactive magnetron sputtering. RBS and ERD were used to determine the elemental concentration in the films, and Raman spectroscopy, to determine their chemical structure. The RBS and ERD analyses indicated that the films contained carbon, nitrogen and small amounts of hydrogen and oxygen. The Gaussian-fitted and identified Raman spectra of the films showed the D and G bands in the range 1000-1800 cm−1, and the 2 D and D+G bands, in the range 2500-3100 cm−1. The photo-induced (pulsed laser, 266 nm) electron emission properties of the films were determined by measuring the cathodes’ bunch charge and calculating their quantum efficiency. The paper discusses the structural properties of the very thin nitrogen-doped carbon-based films deposited on a sapphire substrate with different thicknesses in view of their use as backside-illuminated transmissive vacuum photocathodes.

CsH2PO4 as Electrolyte for the Formation of CH4 by Electrochemical Reduction of CO2

It has been shown that methane can be formed in high amounts by co-electrolysis of CO2 and H2O using a nickel cathode, a CsH2PO4–SiC composite electrolyte and an IrO2 anode. The experimental conditions were 300 °C and 8 bar. The maximum efficiency close to 100% for methane was obtained at a current density of 10–15 mA cm−2. A small amount of hydrogen was formed as the only other product.

Effect of Liquid Phase Plasma Irradiation on Production by Photocatalytic Water Splitting over SrTiO3 Photocatalysts

AbstractA plasma in liquid state was applied as a light source in photocatalysis. The effects of liquid phase plasma irradiation were investigated for hydrogen evolution on the photocatalysts. The photocatalytic activities for hydrogen production from liquid phase plasma and UV light irradiation were compared. SrTiO3 perovskite photocatalysts which prepared by a sol‐gel method with high temperature calcining were introduced in the photocatalytic reaction. The effects of the metal loading on the perovskite photocatalysts were also evaluated in photocatalysis. A small amount of hydrogen was generated in the photo‐decomposition by irradiation of plasma into water without photocatalysts. The rate of hydrogen evolution by photocatalysis using plasma was increased on TiO2 and SrTiO3 perovskite photocatalysts. The photocatalytic activity was improved significantly with the metal loading on SrTiO3 perovskite photocatalysts.

Numerical Investigation of the Effect of Hydrogen Enrichment on an Opposed-Piston Compression Ignition Diesel Engine

High power-to-weight and fuel efficiency are bounded with opposed-piston compression ignition (OPCI) engine, which makes it ideal in certain applications. In the present study, a dynamic three-dimensional CFD model was established to numerically investigate the combustion process and emission formation of a model OPCI engine with hydrogen enrichment. The simulation results indicated that a small amount of hydrogen was efficient to improve the indicated power owing to the increased in-cylinder pressure. Hydrogen tended to increase the ignition delay of diesel fuel due to both dilution and chemical effect. The burning rate of diesel fuel was apparently accelerated when mixing with hydrogen and premixed combustion became dominated. NOx increased sharply while soot was sufficiently suppressed due to the increase of in-cylinder temperature. Preliminary modifications on diesel injection strategy including injection timing and injection pressure were conducted. It was notable that excessive delayed injection timing could reduce NOx emission but deteriorate the indicated power which was mainly attributed to the evident decline of hydrogen combustion efficiency. This side effect could be mitigated by increasing the diesel injection pressure. Appropriate delay of injection coupled with high injection pressure was suggested to deal with trade-offs among NOx, soot and engine power.

The Influence of Hydrogenation on the Structure, Magnetic and Magnetocaloric Properties of Tb–Dy–Co Alloys with a Laves Phase Structure

A complex study of structure, phase composition, surface topology, magnetic, and magnetocaloric properties was performed for TbCo2 and Tb0.3Dy0.7Co2 compounds and for a Tb0.3Dy0.7Co2H0.5 hydride with a low hydrogen content. The hydrogenation was established to impact the structural features at the micro- and nanolevels, as well as the fundamental and functional properties. Introducing even a small amount of hydrogen in the crystal lattice of Tb0.3Dy0.7Co2 compound is found to cause an increase in both the Curie temperature and the magnetic moment at the cobalt atoms. The magnetic phase transition from the paramagnetic to the magnetically ordered state changes from the first (in Tb0.3Dy0.7Co2) to the second (in TbCo2 and Tb0.3Dy0.7Co2H0.5) order, leading to a noticeable decrease in the magnetocaloric effect.