Absolute Hydrogen Research Articles

30‐2: Hydrogen Contents Controlled Silicon Nitride Passivation Layer for Highly Reliable IGZO Thin Film Transistor

To achieve a highly reliable IGZO transistor, silicon nitride thin film, as a passivation layer, has been extensively investigated in recent years, mainly due to readily available fabrication, along with good barrier performance. Here, we found out that larger amount hydrogen residuals was observed in the PECVD deposited SiNx passivation layer, more stable the IGZO oxide device exhibited, which is abnormal behavior to that commonly known in the literatures. Given that FT‐IR and SIMS analysis with various controlled SiNx thin film upon different deposition conditions, the plasma parameters such as power, pressure, source gas ratio could affect hydrogen ion diffusivity into the IGZO layer during the deposition and the chemical composition of hydrogen residuals in the resulting SiNx layer, which is more dominant, rather than absolute hydrogen contents itself, to the initial electrical properties as well the stability of the IGZO transistor device.

A comprehensive experimental study to analyze the cyclic variation of a hydrogen-blended ammonia engine with the Miller cycle

The effects of multiple operating parameters (including speed, valve timing, λ, manifold absolute pressure, spark timing, and hydrogen injection timing) on the coefficient of variation of indicated mean effective pressure (CoVIMEP) of a hydrogen-blended ammonia engine have not been adequately evaluated, which motivates this study. Specifically, CoVIMEP is decreased from exceeding 2.4 % to approximately 0.7 % when the speed increases from 1300 rpm to 2000 rpm. Optimizing valve timing keeps CoVIMEP below 0.8 % by improving the airflow exchange process, and the engine tends to realize lower CoVIMEP at close stoichiometric ratio conditions and low pumping loss. Furthermore, adjusting spark timing affects CoVIMEP by varying the ignition process's stability, with a combustion center of gravity around 9°CA ATDC being suggested. The hydrogen direct-injection timing influences the combustion process's instability by varying the mixture concentration gradient, and the late injection strategy allows the engine to achieve a CoVIMEP of less than 0.9 %.

Educational problems in electrochemical thermodynamics

This article reviews educational problems of electrochemical thermodynamics required as introduction to any electrochemistry-related course. Specifically, the most important, electromotive force (EMF) equation, – is generally derived from Guggenheim’s formulation of electrochemical potential. For this aim the more general equation for equilibrium between phases is introduced. Special attention is given to the measurement of electrode potential. Potential drop across metal|metal contacts, usually displayed in potential profiles of electrochemical cells, can be excluded from them. The conclusion is based on Lord Kelvin’s formulation of the case, when metals are in contact, as “metallic zero”. Concerning absolute potentials, for the cases when the electrode material does not participate in electrochemical reaction, it can be calculated from the Gibbs free energy of the corresponding chemical reaction occurring in solution. Accordingly, the absolute hydrogen electrode potential is determined by thermodynamics of H+/H2 reaction.

Heterofullerene C48B12-impregnated MOF-5 and IRMOF-10 for hydrogen storage: A combined DFT and GCMC simulations study

The H2 storage properties of isoreticular metal-organic framework materials (IRMOFs), MOF-5 and IRMOF-10, impregnated with different numbers and types of heterogeneous C48B12 molecules were investigated using density functional theory and grand canonical Monte Carlo (GCMC) calculations. The excess hydrogen adsorption isotherms of IRMOFs at 77 K within 20 bar indicate that suitable number and type of C48B12 molecules play a crucial role in improving the H2 storage properties of IRMOFs. Among the studied pure and nC48B12 (n = 1, 2, 4, 8) in Ci symmetry impregnating into MOF-5, at 77 K under 6 bar, MOF-5-4C48B12 with a 3.5 wt% and 29.9 g/L hydrogen storage density, and at 77 K under 12 bar, the pure MOF-5 with a 4.9 wt% and 31.0 g/L hydrogen storage density has the best hydrogen storage properties. Whereas, among the studied pure and nC48B12 (n = 1, 2, 4, 8) in S6 symmetry impregnating into IRMOF-10, IRMOF-10-8C48B12 always shows the best hydrogen storage properties among the pure and C48B12-impregnated IRMOF-10 at 77 K within 20 bar. IRMOF-10-8C48B12 has a 6.0 wt% and 34.6 g/L hydrogen storage density at 77 K under 6 bar, and has a 7.1 wt% and 41.4 g/L hydrogen storage density at 77 K under 12 bar. The confinement effect of IRMOFs on C48B12 molecules, and steric hindrance effect of C48B12 molecules on IRMOFs mainly affects the H2 uptake capacity by comparing the absolute H2 molecules in individual IRMOFs units, C48B12 molecules, and IRMOFs-nC48B12 compounds. The absolute hydrogen adsorption profiles show that eight C48B12 molecules impregnating into MOF-5 can exert obvious steric effects for H2 adsorption. The saturated gravimetric and volumetric H2 densities of IRMOF-10-8C48B12 higher than those of MOF-5-8C48B12 due to with larger free volume.

Resonant neutron reflectometry for hydrogen detection

The detection and quantification of hydrogen is becoming increasingly important in research on electronic materials and devices, following the identification of the hydrogen content as a potent control parameter for the electronic properties. However, establishing quantitative correlations between the hydrogen content and the physical properties of solids remains a formidable challenge. Here we report neutron reflectometry experiments on 50 nm thick niobium films during hydrogen loading, and show that the momentum-space position of a prominent waveguide resonance allows tracking of the absolute hydrogen content with an accuracy of about one atomic percent on a timescale of less than a minute. Resonance-enhanced neutron reflectometry thus allows fast, direct, and non-destructive measurements of the hydrogen concentration in thin-film structures, with sensitivity high enough for real-time in-situ studies.

Evidence of the dominant production mechanism of ammonia in a hydrogen plasma with parts per million of nitrogen

Absolute ground state atomic hydrogen densities were measured, by the utilization of two-photon absorption laser induced fluorescence, in a low-pressure electron cyclotron resonance plasma as a function of nitrogen admixtures—0 to 5000 ppm. At nitrogen admixtures of 1500 ppm and higher, the spectral distribution of the fluorescence changes from a single Gaussian to a double Gaussian distribution; this is due to a separate, nascent contribution arising from the photolysis of an ammonia molecule. At nitrogen admixtures of 5000 ppm, the nascent contribution becomes the dominant contribution at all investigated pressures. Thermal loading experiments were conducted by heating the chamber walls to different temperatures; this showed a decrease in the nascent contributions with increasing temperature. This is explained by considering how the temperature influences recombination coefficients, and from which, it can be stated that the Langmuir–Hinshelwood recombination mechanism is dominant over the Eley–Rideal mechanism.

Measuring in situ CO2 and H2O in apatite via ATR-FTIR

We present a new approach to determine in situ CO2 and H2O concentrations in apatite via attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Absolute carbon and hydrogen measurements by nuclear reaction analysis (NRA) and elastic recoil detection (ERD) are used to calibrate ATR-FTIR spectra of CO2 and H2O in apatite. We show that CO2 and H2O contents in apatite can be determined via linear equations (r2 > 0.99) using the integrated area of CO2 and H2O IR absorption bands. The main benefits of this new approach are that ATR-FTIR analyses are non-destructive and can be conducted on polished sample material surfaces with a spatial resolution of ~ 35 μm. Furthermore, the wavenumber of the phosphate IR absorption band can be used to determine the crystallographic orientation of apatite, which allows for accurate quantification of CO2 and H2O in randomly orientated apatite grains. The limit of quantification of H2O in apatite is ~ 400 ppm and ~ 100 ppm for CO2. Via two examples, one from a carbonatite and one from a metasedimentary rock, we show that this new technique opens up new possibilities for determining volatile concentrations and behavior in a wide range of hydrothermal, igneous, and metamorphic systems.

Hydrogen gas as a central on-off functional switch of reversible metabolic arrest – New perspectives for biotechnological applications

Metabolism is the sum of all chemical reactions that sustain life. There is an ongoing effort to control metabolic rate, which correlates with the maximum lifespan potential and constitutes one of the oldest scientific questions. Herein, we report on the complete reversible arrest of cellular metabolism and cell growth in a series of organisms, from microalgae to yeast upon exposure to a 100 % hydrogen atmosphere. We also report a tolerance of the microalgae under these conditions against extreme stress conditions, like high salt concentrations. The addition of oxygen or air almost completely restores the metabolic rate and cell growth. Molecular dynamics simulations are employed to decipher this phenomenon at atomic scale. Various proteins, including photosynthetic and respiratory complexes (LHCII, cytochrome c5) are probed in the interaction with hydrogen. Exposure to hydrogen, as opposed to oxygen, decreases the fluctuations of protein residues indicating thermostability. According to the above mechanism, an absolute hydrogen atmosphere can preserve biological products (e.g. fruits) for a long time without consuming any energy. By combining biological, chemical and computational methods, in this research we provide the basis for future innovative studies and advances in the field of biotechnology.

Hydrogen negative ion density measurement by laser photodetachment and the effect of H recombination on the walls

A laser photodetachment (LPD) was applied to measure the absolute hydrogen negative ion (H−) density in an RF negative ion source. The ion source has been developed to study a Cs-free ion source utilizing a magnetic filter by permanent magnets to enhance the volume production of H− in the extraction region. Prior to a beam extraction experiment, the laser photodetachment was applied as an initial performance evaluation. The absolute H− densities were obtained by LPD with the variation of the RF power. The H− density reached 1.8×109 cm−3 at an RF power of 5 kW. The comparison with the calculation of a particle balance model showed the discrepancy between the model and the LPD results. The LPD result showed the rapid increase in H− density with respect to the RF power compared to the model. By assuming the wall temperature increase and adjusting the recombination coefficient (γrec) of hydrogen (H) atoms on the walls, the discrepancy could be resolved. The recombination coefficient (γrec) plays an important role in determining the H− density in view of the fact that it can affect both the generation and the destruction processes of H−.

Investigation of hydrogen diffusivity in Zr-2.5%Nb alloy pressure tube material using Metallography and Neutron Radiography

Zr-2.5%Nb alloy is used as pressure tube material in Indian pressurised heavy water reactors (PHWR). Hydrogen diffusion studies have been carried out in this alloy in the temperature range 523 K-723 K. Samples were prepared by electrolytic hydrogen charging at one end and then subsequent annealing at said temperatures to form a concentration gradient. Neutron radiography and for the first time, metallography techniques have been used for hydrogen content profiling. Calibration studies for hydrogen in Zr-2.5%Nb alloy have also been carried out at Dhruva imaging beamline to determine the absolute hydrogen content from neutron transmission values. The hydride area fraction has been used as the measure of hydrogen content in metallography studies. The absolute hydrogen content for radiography and hydride area fraction for metallography; vs distance data were fitted with error function to obtain diffusivities at various temperatures. The diffusivity data were further processed to obtain the temperature-dependent diffusion coefficients for both techniques in the temperature range of 523 K-723 K. The results obtained from both techniques are consistent, establishing the fact that a simple lab-based technique like metallography can also be used for diffusion studies.

Flux-Reducing Tendency of Pd-Based Membranes Employed in Butane Dehydrogenation Processes.

We report on the effect of butane and butylene on hydrogen permeation through thin state-of-the-art Pd–Ag alloy membranes. A wide range of operating conditions, such as temperature (200–450 °C) and H2/butylene (or butane) ratio (0.5–3), on the flux-reducing tendency were investigated. In addition, the behavior of membrane performance during prolonged exposure to butylene was evaluated. In the presence of butane, the flux-reducing tendency was found to be limited up to the maximum temperature investigated, 450 °C. Compared to butane, the flux-reducing tendency in the presence of butylene was severe. At 400 °C and 20% butylene, the flux decreases by ~85% after 3 h of exposure but depends on temperature and the H2/butylene ratio. In terms of operating temperature, an optimal performance was found at 250–300 °C with respect to obtaining the highest absolute hydrogen flux in the presence of butylene. At lower temperatures, the competitive adsorption of butylene over hydrogen accounts for a large initial flux penalty.

Results of the QUENCH-LOCA experimental program at KIT

The QUENCH-LOCA bundle test series was launched to investigate the influence of the secondary hydriding phenomena on the applicability of the cladding embrittlement criteria. Seven out-of-pile bundle tests with different zirconium alloy-based cladding materials were performed according to a temperature/time-scenario typical for a LBLOCA in German PWRs. Each bundle contained 21 electrically heated rods with length of about 2 m. For two tests pre-hydrided claddings were used. The profilometry measurements performed over whole length of the post-test claddings showed formation of not only main ballooning area (with burst) but also additional two or three ballooning regions. Cladding wall thinning from 725 to 350 μm due to ballooning was observed at the burst side along 50 mm below and above burst opening. Oxide layer formed after the burst at the inner cladding surface around the burst opening with a thickness of about 15 μm decreasing to 3 μm at a distance of about 20 mm from the burst opening. Hydrogen enrichments (secondary hydriding) were observed for rods having been exposed to peak cladding temperatures of more than 1200 K. The average maximal hydrogen concentration inside the hydrogen bands was less than 1000 wppm and the local absolute maximal hydrogen concentration in these regions was less than 1800 wppm (neutron tomography). A part of the hydrogen absorbed inside the claddings formed the hydrides with μm-sizes, which are distributed in the matrix intra as well inter granular (EBSD). During quenching, following the high-temperature test stages, no fragmentation of claddings was observed. Tensile tests performed at room temperature after bundle tests evidenced fracture at concentrated zirconium hydride regions for several rods with local hydrogen concentrations 1500 wppm and more. Claddings with lower hydrogen concentrations fractured due to stress concentration at burst opening edges. Other tensile tested claddings failed after necking far away from burst.

Absolute atomic hydrogen density measurements in an atmospheric pressure plasma jet: generation, transport and recombination from the active discharge region to the effluent

Atomic hydrogen (H) generated by an atmospheric pressure radio frequency (RF) plasma jet is investigated by two-photon absorption laser induced fluorescence in a He–H2 mixture. The reported time and spatially resolved H density profiles enable a detailed analysis of the species generation, transport and decay along the axis of symmetry of the jet. The H density distribution for a continuous RF plasma jet corresponds well with the outcome of a Pseudo-1D plug flow model. In addition, RF power modulation has a strong effect on the H density in the active discharge region but has a negligible effect on the H density in the far effluent.

MESSENGER Gamma Ray Spectrometer and Epithermal Neutron Hydrogen Data Reveal Compositional Differences Between Mercury's Hot and Cold Poles.

The presence of hydrogen, most likely in the form of water ice, is well established in Mercury's permanently shaded polar craters. But lower concentrations that may exist away from the poles have not previously been well constrained. In this work we use data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) Gamma‐Ray and Neutron Spectrometer to produce the first map of the absolute hydrogen abundance in Mercury's northern hemisphere. We find a mean abundance of 300−150+250 ppm and a latitudinal trend that agrees with earlier results showing enhanced hydrogen contained within Mercury's radar bright craters. Additionally, we observe a middle‐ and low‐latitude variation in hydrogen abundance that is correlated most strongly with temperature 20 cm beneath Mercury's surface.

(5Z)-7-Oxozeaenol: A novel and potent resorcylic acid lactone kinase inhibitor with a cis-enone Michael acceptor.

AbstractIn this review, evidence is presented from a number of research groups over the past two decades that show that (5Z)‐7‐oxozeaenol, an initially biologically uninteresting fungal metabolite, is a remarkably selective and potent kinase inhibitor with important antiproliferative and anti‐inflammatory properties. Taken together, this research shows (5Z)‐7‐oxozeaenol to be a surprisingly selective and competitive ATP binder in which the aromatic ring of the resorcylic lactone mimics the adenine ring of ATP; that it binds covalently to a conserved cysteine at a metabolically unstable cis‐enone Michael acceptor; the conformational importance of the macrocycle, which depends on the absolute stereochemistry and hydrogen bonding properties of the 8,9‐diol; and the success of medicinal chemistry in stabilizing the cis‐enone.

Quantitative and Qualitative Analysis of Hydrogen Accumulation in Hydrogen-Storage Materials Using Hydrogen Extraction in an Inert Atmosphere

Currently, standard samples with high hydrogen concentrations that meet the requirements of hydrogen extraction in an inert atmosphere are not currently available on the market. This article describes the preparation of Ti-H standard samples and the calibration of RHEN602, a hydrogen analyzer, using LECO (LECO, Saint Joseph, MI, USA). Samples of technically pure titanium alloy were chosen as the material for sample production. The creation procedure includes five main steps: sample preparation (polishing to an average roughness of 0.04 μm using sandpaper), annealing, hydrogenation, maintenance in an inert gas atmosphere, and characterization of the samples. The absolute hydrogen concentration in the samples was determined by two methods: volumetric and mass change after the introduction of hydrogen. Furthermore, in-situ X-ray diffraction, temperature programmed desorption (TPD) analysis, and thermogravimetric analysis were used during measurements to investigate the phase transitions in the samples. As a result of this work, a series of calibration samples were prepared in a concentration range up to 4 wt % hydrogen, optimal parameters for measuring high concentrations of hydrogen. The calibration line was obtained and the calibration error was 10%.

Glow Discharge Optical Emission Spectrometer Calibration Using Hydrogenated Zr-2.5Nb Alloy Standard Samples

Currently, standard samples of hydrogen-metal systems meeting the requirements of glow discharge optical emission spectrometers (GD-OES) are not available on the market. This article describes the preparation of Zr-Nb-H standard samples and the calibration of GD-OES with the usage of these samples. Samples of Zr-2.5Nb were chosen as the material for sample production. The creation procedure includes five main steps: sample preparation (polishing to an average roughness, Ra, of 0.04 m using sandpaper), annealing, hydrogenation, maintenance in an inert gas atmosphere, and characterization of the samples. The absolute hydrogen concentration in the samples was determined volumetrically and calculated from the weight change. The distribution of hydrogen was studied using GD-OES Profiler 2 by Jobin Yvon Emission Horiba Group. As a result of this work, calibration curves of Zr, H, Nb, O, and other elements were obtained. The calibration errors were in the range of 1–5%.

Hydrogen-Induced Phase Transformation and Microstructure Evolution for Ti-6Al-4V Parts Produced by Electron Beam Melting

In this paper, phase transitions and microstructure evolution in titanium Ti-6Al-4V alloy parts produced by electron beam melting (EBM) under hydrogenation was investigated. Hydrogenation was carried out at the temperature of 650 °C to the absolute hydrogen concentrations in the samples of 0.29, 0.58, and 0.90 wt. %. Comparative analysis of microstructure changes in Ti-6Al-4V alloy parts was performed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Furthermore, in-situ XRD was used to investigate the phase transitions in the samples during hydrogenation. The structure of Ti-6Al-4V parts produced by EBM is represented by the α phase plates with the transverse length of 0.2 μm, the β phase both in the form of plates and globular grains, and metastable α″ and ω phases. Hydrogenation to the concentration of 0.29 wt. % leads to the formation of intermetallic Ti3Al phase. The dimensions of intermetallic Ti3Al plates and their volume fraction increase significantly with hydrogen concentration up to 0.58 wt. % along with precipitation of nano-sized crystals of titanium δ hydrides. Individual Ti3Al plates decay into nanocrystals with increasing hydrogen concentration up to 0.9 wt. % accompanied by the increase of proportion and size of hydride plates. Hardness of EBM Ti-6Al-4V alloy decreases with hydrogen content.

Hydrogen Breath Testing Predicts Bowel Preparation Quality Prior to Colonoscopy: A Systematic Review.

BackgroundThis systematic review aims to assess the accuracy of hydrogen breath testing as a predictor of bowel preparation.MethodsStudies were identified from MEDLINE, Embase, Web of Science, Cochrane Library and clinicaltrials.gov. Two investigators evaluated abstracts for inclusion criteria - report of correlation between hydrogen breath levels and bowel preparation quality, prospective design and non-emergent colonoscopy in adults. Included studies underwent duplicate data extraction using a standardized approach. The Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool assessed quality of the studies.ResultsOne hundred fifty-nine publications were identified, and six unique studies met inclusion criteria. The number of patients analyzed ranged from 61 to 127. Three studies were performed in the USA, one in Japan and two in Italy. Three studies used a prebiotic in addition to a purgative, with the intention of enhancing the discriminating ability of hydrogen breath levels. Three studies assessed baseline hydrogen levels. In five of the six studies, hydrogen breath levels were predictive of inadequate bowel preparation. Suggested absolute hydrogen levels to distinguish adequate from inadequate bowel preparation ranged from 3 to 10 parts per million. Depending on the cutoff value, sensitivity ranged from 71% to 100% and specificity from 87% to 100%. There was significant heterogeneity among studies in breath testing protocol and breath analyzer used. Full-text studies had low risk of bias in most assessed domains.ConclusionHydrogen breath levels predict bowel preparation adequacy but existing studies have significant limitations. Further studies should use standardized methods and consider the real-world practicality of self-administered home breath testing.

High Volumetric Hydrogen Storage Capacity using Interpenetrated Metal–Organic Frameworks

AbstractMetal–organic frameworks with extremely large specific surface areas can reach very high gravimetric hydrogen storage capacities. However, these ultra‐porous materials possess typically a very low density and, therefore, a poor volumetric hydrogen storage capacity. Here we study experimentally the influence of interpenetration on the volumetric and gravimetric hydrogen storage capacity by comparing two metal–organic frameworks of the MFU‐4 family, non‐interpenetrated MFU‐4l and CFA‐7 with an interpenetrated structure. At 77 K the absolute volumetric hydrogen uptake of CFA‐7 is more than twice that of MFU‐4l.