Measurement Of Hydrogen Concentration Research Articles

Diffusible Hydrogen Testing in Australia

Diffusible hydrogen content in weld metals is a determining factor in the development of hydrogen-assisted cold cracking. In view of the importance of accurate and reliable quantification of diffusible hydrogen content, a number of industry standards have been developed to provide guidance on standardisation of methods for measurement of diffusible hydrogen content. A variety of test methods are currently used by industry and research organisations for the measurement and qualification of consumables and these test methods are generally accepted to be valid and comparable. However, the maintenance and calibration of the various hydrogen test methods is a matter of self regulation and, for this reason, the reliability and reproducibility of results across various test methods and laboratories is currently a matter of interest for Australian industry. Further, a more advanced and rapid measurement system is being utilised and a broad-based, independent and closely controlled trial is required to compare against traditional test methods and validate its application. In order to address these interests, the current work was commissioned by the Welding Technology Institute of Australia (WTIA) Technical Panel 2 — Working Group on Welding Metallurgy, primarily to assess the comparative performance of the various test methods (mercury displacement, gas chromatography, hot extraction) across a number of Australian laboratories with a uniform sample set produced under controlled welding conditions. A secondary aim was to determine the validity of the rapid test method known as Hot Extraction at 400°C.

Trace Analysis of Deuterium by Reduction of Mercury (II) Oxide

Recently we developed an analyzer capable of measuring hydrogen concentrations of less than 5 cm3/1000 cm3. The analyzer is characterized by the fact that it uses a carrier gas purifier, a thermal conductivity detector, high- and low-temperature separation columns, and an “after-cut method”to remove impurities from sample and carrier gases. In the after-cut method, nitrogen gas is removed by switching gas lines. In the analyzer, a trace reduction detector is also used to detect extremely small amounts of hydrogen based on the reduction reaction of mercuric oxide with hydrogen. This is another distinctive characteristic of this analyzer.In the present study, we evaluated the performance of the analyzer in measuring deuterium concentrations. We measured spectra for five sample gases with different concentrations and examined the peaks and retention times of the spectra. The peaks and retention times were stable within a relative standard deviation of less than 10%, and a definite linear relationship between the peaks and deuterium concentrations was also observed. Based on these results, we have considered how to develop an analyzer capable of directly measuring the deuterium existing in natural air.

Effect of Different Solvent Characteristics on the Proton‐Ligand and Sm+3‐Ligand Formation Constant of Butanamide‐3‐[2‐[(2‐Hydroxyphenyl Methylene) Amino]Ethylimino]N‐Phenyl(BHPAP) in Mixed Solvents

AbstractComplexes equilibrium of (BHPAP) with proton and Sm+3 ion has been measured in various mixed aqueous solvents, viz.; methanol‐water, ethanol‐water, acetone‐water and dioxane‐water. Based on potentiometric equilibrium measurements of hydrogen ion concentration at 30 °C, ionic strength 0.1 M KNO3 and in the above various mixed solvents, the values of protonation constant of BHPAP‐Sm+3 complex have been evaluated. The variation of protonation and stability constants with the inverse of dielectric constant or mole fraction of solvent was studied. Application of Fuoss expression and consideration of electrostatic and non‐electrostatic effects are made to explain the above constants.The solid complexes were isolated for each Pr+3 and Nd+3‐BHPAP. Elemental analysis, conductance, infrared spectra, and electronic spectra for these solutions and TG, DTG and DTA measurements characterized these solids. The ligand behaves towards the metal ion as a dibasic tetradentate ligand.

Prevalence of small bowel bacterial overgrowth and its association with nutrition intake in nonhospitalized older adults.

To determine the prevalence of small bowel bacterial overgrowth (SBBO) in older adults and to assess whether SBBO is associated with abdominal complaints and nutrient intake. Cross-sectional survey. Eight senior residence sites in Stuttgart, Germany. Older adults living independently in senior residence houses. The prevalence of SBBO was measured in 328 subjects, of whom 294 were aged 61 and older, by measuring hydrogen concentration (parts per million; ppm) in exhaled air after ingestion of 50 g glucose. Anthropometric data were obtained and nutritional status was recorded with a computer-aided diet history. The prevalence of a positive hydrogen breath test (>10 ppm increase) was 15.6% in older adults, compared with 5.9% in subjects aged 24 to 59. The intake of inhibitors of gastric acid production contributed significantly to the high prevalence of a positive breath test in older adults, which was associated with lower body weight, lower body mass index, lower plasma albumin concentration, and higher prevalence of diarrhea. Subjects with a positive hydrogen breath test consumed significantly less fiber, folic acid, and vitamins B2 and B6 than those without. No difference was observed in the intake of energy, protein, fat, or carbohydrates. Prevalence of SBBO is associated with reduced body weight, which is paralleled by reduced intake of several micronutrients. Malabsorption resulting from diarrhea might be an aggravating factor contributing to weight loss in these subjects.

Influence of alloying on hydrogen-assisted cracking and diffusible hydrogen content in Cr-Mo steel welds

Study of hydrogen-assisted cracking and measurement of diffusible hydrogen content in different Cr-Mo steel welds shows that under identical conditions, susceptibility to cracking increased and diffusible hydrogen content decrease with increase in alloy content. Hydrogen permeation studies show that hydrogen diffusivity decreases and solubility increases with increase in alloy content. Thus decrease in diffusible hydrogen content with increase in alloying is attributed to increase in apparent solubility and decrease in apparent diffusivity of hydrogen. Analysis of the results indicates that variation of diffusible hydrogen content and apparent diffusivity of hydrogen with alloy content can be represented as a function of carbon equivalent CE1 originally proposed to predict the hardness in the heat-affected zone of alloy steel welds.

Measurement of hydrogen concentration in thick mineral or rock samples

This paper describes an application of a proton–proton elastic recoil coincidence spectroscopy to hydrogen analysis using a proton microbeam at an energy of 20 MeV. This method provides depth profiles of hydrogen over a thickness of 200 μm of silicate samples in a short time. A typical beam size is as small as 27 × 32 μm. The depth resolution is about 10 μm. The present work proves that the proton–proton elastic recoil coincidence spectroscopy is a promising method for measurements of hydrogen in mineral and rock samples with thickness up to 200 μm.

An electrochemical hydrogen meter for measuring hydrogen in sodium using a ternary electrolyte mixture

An electrochemical sensor for measuring hydrogen concentration in liquid sodium that is based on a ternary mixture of LiCl, CaCl 2 and CaHCl as the electrolyte has been developed. DSC experiments showed the eutectic temperature of this ternary system to be ∼725 K. Impedance spectroscopic analysis of the electrolyte indicated ionic conduction through a molten phase at ∼725 K. Two electrochemical hydrogen sensors were constructed using the ternary electrolyte of composition 70 mol% LiCl:16 mol% CaHCl:14 mol% CaCl 2 and tested at 723 K in a mini sodium loop and at hydrogen levels of 60–250 ppb in sodium. The sensors show linear response in this concentration range and are capable of detecting a change of 10 ppb hydrogen in sodium over a background level of 60 ppb. Identification of this electrolyte system and its use in a sensor for measuring hydrogen in sodium are described in this paper.

Some problems on the resistance method in the in situ measurement of hydrogen content in palladium electrode

Some problems on the resistance method in determining the hydrogen content in PdH x electrodes are discussed. First, the resistivity ratio of PdH x , the temperature coefficient of resistivity and the resistance of PdH x , and the resistance of Pd having undergone hydriding–dehydriding cycles are discussed. It is found that the resistivity ratio is somewhat higher than the resistance ratio with the same x value and their difference depends on the internal stress-state arising from hydrogen insertion. Another fact that has been omitted in past work is that the temperature coefficients of PdH x resistance and resistivity increase while x 0.7. The Pd resistance decreases with hydriding–dehydriding cycle number due to the shape deformation of the electrode, which occurs. Second, the effect of the non-uniform distribution of x in the electrode on determining the hydrogen content is discussed theoretically. It is proved that errors are particularly significant when the Pd+H system is in the mixed α+β phase or the resistance is near the maximum value. Finally, we calculate the additional potential drop and hence the apparent resistance of the PdH x electrode caused by the co-conduction of electrolyte, the concentration-cell effect, the collection of electrolysis current and other imperfect configurations of the electrode in the in situ measurement of electrode resistance, using a direct current. It is found that an electrode with a large ratio of length to radius, an active surface, a surrounding electrolyte with high conductance and a high electrolysis current will all induce substantial additional resistance. At the same time, some advice on measuring the PdH x resistance is presented.

Passivated thick film catalytic type H 2 sensor operating at low temperature

Thick film catalytic sensors operable at a temperature of 120 °C have been developed to measure hydrogen concentration (HC) in 0–10% (v/v) range. The sensors consists of a glass encapsulated Pt-heater coated with a catalytic thick film and a compensating element without the active film. An rf sputtered PTFE thin film on active element has been found to improve resistance of the sensors to poisoning due to hexamethyldisilazane (HMDS) and iodine etc. During operation, temperature of compensating element is held constant at 120 °C to offset the effect of ambient temperature variations. A simple circuit for control of sensor temperature and measurement of its response is described. The sensors showed linear response up to 10% (v/v) of hydrogen in ∼40 standard cm 3/min air flow with response and recovery times of ∼30 and 50 s, respectively. The sensors were found to have a stable response when operated continuously for a period of 1 year.

Effects of sample preparation on the measurement of organic carbon, hydrogen, nitrogen, sulfur, and oxygen concentrations in marine sediments

The elemental composition of marine sediment provides useful information for the study of environmental processes including biogeochemical cycling and contaminant partitioning. It is common practice to acidify marine sediment samples to remove carbonate before measuring the concentrations of organic carbon (C). To date, however the effects of acidification on the concentrations of hydrogen (H), nitrogen (N), sulfur (S) and oxygen (O) in marine sediments have not been explicitly addressed. Acidification may contaminate or alter the sediment samples and create experimental artifacts affecting the validity of resulting H/C, C/N and O/C ratios. The objective of this study was to quantify how various preparation techniques affect the measured concentrations of C, H, N, S and O in marine sediments. Effects of four different pretreatments: unacidified (whole), acidification by HCl vapor, acidification by direct addition of HCl, and combustion were evaluated using five marine sediments and a standard reference material. The magnitude of carbonate loss between the vapor and direct acidification treatments was evaluated using stable C isotope analysis. Carbonates were most effectively removed by direct addition of HCl; and our results agree with findings of other studies which found direct addition of HCl to be the most accurate method for measuring organic C. However, the acid treatments elevated the apparent concentration of H and O; and in a few cases concentrations of N and S were significantly affected by acidification. In general, combustion significantly reduced all elemental concentrations compared to the whole sample. Based on these results, we recommend analysis of the untreated whole sediment for determining N, H, O, and S.

Hydrogen distribution in multipass submerged arc weld metals

Hydrogen distribution in multipass submerged arc weld metal has been measured and analysed. The measurement of initial hydrogen content in a molten pool by obtaining samples directly from the pool shows that the effect of dilution on the initial hydrogen content can be neglected. The transient hydrogen distribution in multipass weld metal has also been measured. This can be fairly well explained by the present hydrogen diffusion model using the two-dimensional source solution.

Water detection on atmosphereless celestial bodies: Alternative explanations of the observations

Alternative explanations are proposed for the results of the three types of remote sensing experiments in which water ice is supposed to be found on the surfaces of atmosphereless celestial bodies: (1) measurements of hydrogen content by the neutron spectrometer on Lunar Prospector, (2) observations of the absorption bands near 3 μm in reflectance spectra of asteroids, and (3) radar observations of polar regions of Mercury. Calculations have shown that in the first two types of observations solar wind protons chemically trapped by oxygen atoms in hydroxyl groups or other radiation defects in oxygen‐bearing particles on the surfaces of atmosphereless bodies can be mistaken for water. Higher hydrogen content in the lunar polar regions, especially in polar craters, as compared to equatorial zones can be due to sharp decrease of escape probability with temperature. Spots of high hydrogen content in equatorial zones of the Moon can be explained by variations of degassing rates in different materials. Solar wind origin of OH groups may account for 3‐μm absorption by asteroids of M and E classes thought to be differentiated. Strong, highly depolarized radar echoes from polar and lower latitude craters of Mercury can be explained by decrease of the dielectric loss of silicate material with temperature, which solves the problems of delivery and thermal stability of low‐loss material on Mercury surface, being consistent with the observed regional variations of radar brightness. The possibilities considered in the paper should be taken into account in interpretation of the observations aimed on search of water.

Endoscopic measurement of intragastric hydrogen and methane concentrations for the diagnosis of intragastric fermentation

Endoscopic measurement of intragastric hydrogen and methane concentrations for the diagnosis of intragastric fermentation

Ion channeling studies of hydrogen in homoepitaxially grown CVD diamond

Abstract Using ion channeling measurements in conjunction with the resonant 1 H( 15 N,αγ) 12 C nuclear reaction or with proton Rutherford backscattering spectrometry we studied the incorporation of hydrogen from the plasma into homoepitaxial (100) and (111) CVD diamond films. The measured hydrogen concentration and the structural defect density of the diamond lattice derived from proton channeling yields were observed to be correlated. Hydrogen lattice location studies for different incident ion channeling directions showed no dominant fraction of H occupying either one of the two theoretically predicted sites. These results suggest that in CVD films with quite high dislocation densities and relative H concentrations above 10 −3 , hydrogen is predominantly incorporated at structural defect sites uncorrelated with the lattice symmetry.

The Effect of Jet Mixing on the Combustion Efficiency of a Hot Fuel-Rich Cross-Flow

Many combustion systems inject air into a hot fuel-rich cross-flow to minimize carbon monoxide emissions. The aim of this study is to improve the understanding of the relationship between mixing, chemical kinetics, and combustion efficiency for air jets in a hot reacting cross-flow. Carbon monoxide and hydrogen concentration measurements have been made for nine different round jet configurations issuing air into a hot reacting cross-flow. The unmixedness was measured for the 18 round jets module. The study indicates that the maximum combustion efficiency depends primarily on the overall equivalence ratio. An equivalence ratio of approximately 0.8 leads to the best combustion efficiency for all of the round jet modules. The predominance of the equivalence ratio highlights the importance of premixing prior to combustion. At constant equivalence ratio, low momentum flux ratios yield higher emissions. The combustion efficiency improves as the number of jets increases. The same flow conditions optimized both H2 and CO combustion efficiencies.

The influence of the kinetics of the hydrogenation of Nd–Fe–B alloys on hydrogen distribution in the alloy phases

We present results of experiments on hydrogenation of Nd 16Fe 75.8B 8.2 controlled by two parameters: the amount of hydrogen and the rate of feeding the sample with hydrogen at low pressures. By proper combination of these parameters four different schemes for the hydrogenation process were generated: (1) selective hydrogenation of the Nd-rich phase, (2) hydrogenation of the Nd-rich phase followed by diffusion of hydrogen into the Nd 2Fe 14B phase, (3) simultaneous partial hydrogenation of both phases, (4) simultaneous complete hydrogenation of both phases. For the first two cases the results of measurements of equilibrium pressure versus hydrogen concentration at room temperature are presented in the form of a p– c diagram with three phase regions: (1) Nd+NdH y +Nd 2Fe 14B, (2) NdH y +Nd 2Fe 14B+Nd 2Fe 14BH x<2.7 , (3) NdH y +Nd 2Fe 14BH x>2.7

Ultrasonic and resistive hydrogen sensors for inert gas-water vapour atmospheres

Hydrogen concentration measurements were developed for a series of experiments in which a molten oxide is mixed with water to study vapour explosion phenomena. The gas mixture to be analysed consisted of hydrogen with water vapour and either helium or argon. Two types of sensor have been developed for these tests. The first is an ultrasonic sensor, which detects variations in the acoustic velocity within a 0.4 mm-diameter palladium wire. The sensor measures hydrogen concentrations in the range 0.1-100%, at atmospheric pressure, over an operating temperature range of 200-400 °C. The response time (for 0-90% of the final response) is about 30 s at 180 °C and 8 s at 380 °C. The second sensor consists of a palladium coil, constructed with 0.05 mm-diameter wire that is wound around a ceramic tube. Measurements of wire resistance were used to detect partial pressure of hydrogen. This sensor operates at 150-300 °C and measures hydrogen concentrations of 1-100%. The response time is short, 1-2 s for a temperature of 300 °C.

Measurement of hydrogen content in ultrathin diamond-like carbon films using low-energy elastic recoil detection analysis

Abstract We performed direct measurement of hydrogen content in diamond-like carbon (DLC) thin films using elastic recoil detection analysis (ERDA) of hydrogen atoms forward-scattered by a 2 keV beam of helium ions. DLC films were prepared in an electron cyclotron resonance (ECR) microwave plasma chemical vapor deposition (CVD) system. Use of a low-energy beam in conjunction with a small incidence angle allowed measurements of hydrogen content in the surface region of films of various thickness (2.4, 5 and 100 nm). Analysis of resultant spectra indicates that a higher negative substrate bias voltage produces lower hydrogen content; these findings are consistent with those obtained on thick DLC films using high-energy (2–3 MeV) ERDA. Accordingly, this confirms the suitability of using the low-energy ERDA system described to measure hydrogen content in ultrathin (

Nuclear reaction analysis of hydrogen migration in silicon dioxide films on silicon under 15N ion irradiation

Hydrogen concentration profiles in wet, thermally grown SiO 2/Si layer structures were measured using the 15N nuclear reaction analysis (NRA) method: the measured hydrogen concentration in the SiO 2 layer is initially about 2.2×10 20 cm −3 and almost constant throughout the SiO 2. For the NRA measurement of the initial H-profile a low dose of 15N ions has been taken in order to minimize a change in the profile by the NRA measurement itself. After high dose 15N ion irradiation an accumulation of hydrogen in the SiO 2/Si transition region (called interface) is observed together with a loss of hydrogen through the surface. SiO 2/Si structures with a SiO 2 film thickness of 32, 92 and 173 nm were investigated. A rapid initial increase of the H concentration in the transition region with increasing irradiation fluence is observed for all three samples. In the 32 and 92 nm samples prolonged irradiation leads to a subsequent reduction of the H concentration at the interface.

モリブデナイト結晶中の水素の拡散，脱離の観察

Diffusion and desorption of hydrogen in a bulk of molybdenite crystal are studied by measurement of gas emitted from the bulk crystal during cleavage experiment for observation of gases in a bulk, electron stimulated desorption (ESD) for measurement of hydrogen concentration on the surface and temperature programmed desorption (TPD) for estimating ion of an activation energy of diffusion and desorption process. The cleavage and ESD experiments are performed to observe the change of hydrogen concentration in the bulk and on the surface by the sample heating. These experiments show that a mount of hydrogen in the bulk reduces at about 500°C and that the hydrogen concentration on the surface and thermal desorption of hydrogen from the bulk also begin to increase around 500°C. The increase of hydrogen concentration on the surface suggests that the activation energy for thermal desorption is lager than the diffusion energy in the bulk to (0001) surface. However, in this case this may not be applicable because of similar temperature behavior of surface hydrogen and desorbed hydrogen. The mechanism of the diffusion and the desorption process is discussed. The activation energy for the desorption induced by diffusion of hydrogen in the bulk to (0001) surface is about 76 kJ/mol.