Decrease In Hydrogen Content Research Articles

Occurrence of metabolic alkalosis in rumen lactic acidosis: A review article

The pH of the extracellular fluids is one of the most vigorously regulated variables of the body. Acidosis is associated with an increase in hydrogen ion concentration (decreasing pH), whereas alkalosis is caused by a decrease in hydrogen ion concentration (increasing pH). The published literature indicates that the occurrence of metabolic alkalosis in acute rumen lactic acidosis is most probable in the early and end stages of sub-acute rumen lactic acidosis or acute cases resulting from rumen lactic acidosis.

A low-power readout circuit for nanowire based hydrogen sensor

This paper presents a fully integrated lock-in amplifier intended for nanowire gas sensing. The nanowire will change its conductivity according to the concentration of an absorbing gas. To ensure an accurate nanowire impedance measurement, a lock-in technique is implemented to attenuate the low frequency noise and offset by synchronous demodulation or phase-sensitive detection (PSD). The dual-channel lock-in amplifier also provides both resistive and capacitive information of the nanowire in separate channels. Measurement results of test resistors and capacitors show a 2% resolution in the resistance range 10–40kΩ and a 3% resolution in the capacitance range 0.5–1.8nF. Moreover, a 28.7–32.1kΩ impedance variation was measured through the lock-in amplifier for a single palladium nanowire that was exposed to a decreasing hydrogen concentration (10% H2 in N2 to air). The chip has been implemented with UMC 0.18μm CMOS technology and occupies an area of 2mm2. The power consumption of the readout circuit is 2mW from a 1.8V supply.

Eukaryotization of the early biosphere: A biogeochemical aspect

The synthesis of data on the paleobiology and geochemistry of the Archean and Proterozoic and the ecology, biochemistry, and comparative genomics of living organisms provides a means for reconstructing the development of biological complexity on the subcell, organism, and ecosystem levels. The conditions and time of the origin of oxygenic photosynthesis, eukaryotic cells, and multicellular animals were determined. These evolutionary events had a profound influence on the global biogeochemical cycles, sedimentogenesis, and climate of the Earth. Irreversible geochemical changes in the biosphere and the biochemical evolution of living systems are described as complementary processes. A decrease in hydrogen concentration in the early biosphere, an increase in oxygen concentration in the ocean, and changes in the bioavailability of metals (Fe, Ni, Co, V, W, Cu, Mo, etc.) known as enzyme activators were considered as key factors of eukaryotization. The reasons for variations in the availability of the metals in the biosphere were distinguished. The continuity of life was maintained owing to the preservation of the functionality of archaic metabolism types through the compartmentalization of biochemical reactions and the complication of cellular metabolic networks. The metabolic cascades of living cells probably recapitulate this prolonged evolutionary process. The exhaustion of abiogenic hydrogen sources stimulated the symbiosis of hydrogen-producing and hydrogen-consuming prokaryotes and the involvement of simple hydrogen-bearing volatile compounds (CH4, NH3, H2S, and, finally, H2O) as a substrate for life, which eventually predefined the chemical composition of the terrestrial atmosphere strongly dominated by nitrogen and oxygen as by-products of exchange reactions. The oxygenation of the ocean diminished the mobility and bioavailability of some metals that had served as the earliest enzyme activators. The evolutionary response to this process was the formation of mechanisms of extraction, accumulation, and the retention of ancient activator metals (e.g., Fe, W, and Ni) in the cell and in the ecosystem, as well as the active involvement of new metals (e.g., Mo, Cu, and Zn). Oceanic biota became the main concentrator and reservoir for these metals. The appearance of eukaryotic cells, the increasing role of heterotrophy, an increase in biodiversity, the complication of trophic relationships, the acceleration of the cycle of biophile elements, and other features of the biosphere eukaryotization were to large extent a response to the narrowing of the geochemical basis of life. A pivotal point in the prolonged process of biosphere eukaryotization was a series of glaciations at the end of the Proterozoic (750–540 Ma) and the active oxygenation of the ocean, which enabled the global expansion of eukaryotic organisms.

Effect of the ionization energy loss density of high-energy bismuth, krypton, and xenon ions on the development of hydrogen blisters in silicon

Radiation-induced athermal hydrogen removal from single-crystal silicon subjected to irradiation by high-energy heavy Bi+ (E = 710 MeV), Kr+ (E = 85 and 250 MeV), and Xe+ (130 MeV) ions is detected experimentally. The decrease in the hydrogen concentration depends on the specific ionization energy losses of high-energy heavy ions. At high specific ionization losses of Bi+ ions with E = 710 MeV (22.5 keV/nm), the hydrogen concentration decreases to a level at which blisters cannot be observed in an optical or electron microscope (which is likely to be 1 at % hydrogen at the peak of the calculated hydrogen concentration profile). At medium specific ionization losses of Xe+ ions with E = 130 MeV (12.5 keV/nm) and Kr+ ions with E = 250 and 85 MeV (9.5 and 8.5 keV/nm, respectively), the hydrogen concentration decreases to a level that does not affect blister formation but determines the blister failure (flaking) conditions.

Hydrogen-Inclusion-Induced Critical Current Deviation of Nb/AlOx/Nb Josephson Junctions in Superconducting Integrated Circuits

Josephson junctions with niobium electrodes connected with palladium, which is employed in the bump metallization, have about 20% larger critical current density than those with electrodes not connected with palladium. This increase in the critical current density coincides with the desorption of hydrogen from the niobium electrodes. Hydrogen incorporates during the fabrication process and desorbs in an atmosphere when the niobium surface is covered with palladium. The decrease in hydrogen concentration in niobium electrodes causes an increase in the critical current density of the junctions. Most of the change can be attributed to the niobium work function change, with some of it due to the change in superconductivity of niobium. Elastic deformation can also be added as a cause. As hydrogen diffuses fast in niobium and stops in aluminum, hydrogen concentration differences arise within a circuit, which result in a critical current deviation beyond statistical scattering. This mechanism explains why the junctions at both ends of a serial array of circuits exhibit abnormal critical current about 20% larger than the average.

The Effect of Ultraviolet Exposure on Solution Process of Silicon Thin Film

Cyclopentasilane, which has a chemical shift at 3.7 ppm as revealed by 1 H NMR, was used as a precursor for solution-processed Si films after photopolymerization. X-ray photoelectron spectroscopy revealed a Si 2p peak at 99.68 eV, showing a binding energy shift of about 0.3 eV due to a decrease in hydrogen content resulting from UV exposure. Meanwhile, Raman shifts maintained their demonstration of the amorphous Si phase of the films. Based on these results, we confirm the modification of the amorphous Si structure due to UV exposure on polysilane solution during solution process.

High Temperature Post-deposition Annealing Studies of Layer-by-layer (LBL) Deposited Hydrogenated Amorphous Silicon Films

AbstractHigh temperature post-deposition annealing studies were done on hydrogenated amorphous silicon thin films deposited by plasma-enhanced chemical vapour deposition (PECVD) using the layer-by-layer (LBL) deposition technique. The films were annealed at temperatures of 400 °C, 600 °C, 800 °C and 1000 °C in ambient nitrogen for one hour. Auger electron spectroscopy (AES) depth profiling results showed that high concentration of O atoms were present at the substrate/film interface and at film surface. Very low concentration of O atoms was present separating silicon layers at regular intervals from the film surface and the substrate due to the nature of the LBL deposition and these silicon oxide layers were stable to high annealing temperature. Reflectance spectroscopy measurements showed that the onset of transformation from amorphous to crystalline phase in the LBL a-Si:H film structure started when annealed at temperature of 600 °C but the X-ray diffraction (XRD) and Raman scattering spectroscopy showed that this transition only started at 800 °C. The films were polycrystalline with very small grains when annealed at 800 °C and 1000 °C. Fourier transform infrared spectroscopy (FTIR), measurements showed that hydrogen was completely evolved from the film at the on-set of crystallization when annealed at 800 °C. The edge of the reflectance fringes shifted to longer wavelength decrease in hydrogen content but shifted to shorter wavelength with increase in crystallinity.

Hydrogen Delayed Fracture Properties and Internal Hydrogen Behavior of a Fe–18Mn–1.5Al–0.6C TWIP Steel

The hydrogen delayed fracture (HDF) properties and internal hydrogen behavior were investigated in a Fe–18Mn–1.5Al–0.6C steel, a representative twinning induced plasticity (TWIP) aided steel. Slow strain rate tests (SSRT) were employed on both smooth and notched specimens to evaluate the effects of diffusible hydrogen on the HDF properties of the steel. Results showed that the fracture stress, fracture strain and time to fracture of the hydrogen pre-charged specimens were relatively insensitive to the amount of diffusible hydrogen. Fracture surface exhibited a ductile dimple fracture mode regardless of the diffusible hydrogen concentration. It was found that most hydrogen became non-diffusible after SSRT. The major trapping sites of hydrogen were dislocations, grain boundaries and twins. The activation energies for detrapping of hydrogen were estimated 35 kJ/mol for dislocations or grain boundaries, and 62 kJ/mol for twins. A comparison of the HDF properties of the present steel with those of other high strength steels revealed that the TWIP steel appeared to be relatively immune to hydrogen delayed fracture. This was due to the combined effects of (a) higher hydrogen solubility of austenite matrix (b) negligible portion of diffusible hydrogen to the total hydrogen, (c) decrease of diffusible hydrogen content during the deformation, and (d) no transformation of austenite to either e or α′ martensite.

Influence of hydrogen levels on porosity and mechanical properties of Mg alloy castings

The effects of hydrogen levels on microstructure of porosity and mechanical properties of magnesium alloy castings were investigated. The hydrogen content of AZ91 alloy melt under Ar+HFC-134a mixed gas protection was 103 cm3 kg−1, which was less than that of 139 cm3 kg−1 under flux protection, therefore the effect of gas protection was better. The porosity ratio in microstructure of castings melted under gas protection was 1˙8%, which was also less than that of 2˙6% under flux protection. The hydrogen content of melt under flux protection and degassed with Ar gas was 70 cm3 kg−1, and the corresponding porosity ratio in microstructure of castings was only 0˙6%. The density of the samples was increased with decreasing hydrogen content. The tensile strength of AZ91 alloy casting sample under flux protection and degassed with Ar gas was 21% higher than that of undegassed one, and the elongation was also 50% higher.

Hydrogen detection and quantification at polymer surfaces investigated by elastic peak electron spectroscopy (EPES)

The elastic peak electron spectroscopy (EPES) combined with the electron single scattering model calculations is applied for detecting and quantifying hydrogen at a surface region of selected polymers: polyethylenes (low, high densities and ultra high molecular weight – PELD, PEHD, PEUHMW), polypropylene – PP, polystyrene – PS, and poly[methyl(phenyl)silylene] – PMPSi. The physics under the procedure is based on an electron quasi-elastic scattering on a target atom (a recoil effect). The photoelectron C 1s and Auger electron C KLL spectra induced by Mg Kα radiation (1253.6eV) are used for characterization of the polymer surfaces' damage produced by incident electron irradiation when applying the EPES method. The polymer surfaces irradiated with low electron dose revealed hydrogen content and C sp2/sp3 ratio close to the nominal values. Ongoing electron irradiation led to the hydrogen content decrease and the C sp2 percentage growth. The effect of surface charging on the recoil effect is also discussed.

Ion conducting properties of hydrogen-containing Ta 2O 5 thin films prepared by reactive sputtering

Hydrogen-containing Ta 2O 5 (Ta 2O 5:H) thin films are considered to be a candidate for a proton-conducting solid-oxide electrolyte. In this study, Ta 2O 5:H thin films were prepared by reactively sputtering a Ta metal target in an O 2 + H 2O mixed gas. The effects of sputtering power and post-deposition heat treatment on the ion conducting properties of the Ta 2O 5:H thin films were studied. The ionic conductivity of the films was improved by decreasing the RF power and a maximum conductivity of 2 × 10 −9 S/cm was obtained at an RF power of 20 W. The ionic conductivity decreased by heat-treatment in air, and no ion-conduction was observed after treatment at 300 °C due to the decrease in hydrogen content in the films.

In situ ERDA measurements of hydrogen isotope concentrations in palladium at atmospheric pressure

In situ elastic recoil detection analysis (ERDA) measurements in gases at atmospheric pressure have been carried out using 15MeV 4He ion beams. The beams are extracted through a molybdenum foil having a thickness of 5μm. The maximum depth of analysis is about 4μm for the palladium hydride and palladium deuteride (PdHx and PdDx, x=0.7–0.8) samples. The temperature of the samples rises stepwise from room temperature to 180°C. ERDA spectra are obtained every 2min. Hydrogen and deuterium in the samples are discharged in the temperature range of 120–140°C in a vacuum. Decrease in the hydrogen concentration in the PdHx sample heated in a vacuum follows a first order in the value of x and an apparent activation energy of discharge of hydrogen is 1.05eV. On the other hand, the hydrogen and deuterium concentrations decrease at about 80°C in air. No isotope effects are observed in both a vacuum and air. The temperature at which the hydrogen concentration decreases in helium gas is almost the same as that in a vacuum. It indicates that hydrogen and deuterium atoms are discharged by chemical reactions with air and that there are no effects of cooling of the thermocouple by convection of air.

Influence of impurity hydrogen on coarse grain evolution in high purity aluminum foils for electrolytic capacitors

Two aluminum plates with 99.99 mass% purity with different hydrogen contents of 0.17 and 0.41 mass ppm were hot-rolled to 10 mm in thickness, cold-rolled by 99% to 130 μm in thickness, annealed at 250°C for 2 h, cold-rolled by 15% to 110 μm in thickness and finally annealed, which is similar to commercial processes of high purity aluminum foils for electrolytic capacitors. The foils were subjected to optical macro- and micro-scopies, thermal desorption spectroscopy (TDS), hydrogen micro-print technique (HMPT) and electron back-scattering diffraction pattern (EBSP) analysis and the effect of impurity hydrogen on the growth of off-cube grains in a recrystallized microstructure with a strong cube texture was investigated. It was confirmed that abnormal grain growth of off-cube grains becomes more conspicuous with the increase in the amount of impurity hydrogen in the original ingot. The HMPT analysis showed that hydrogen concentration in the cube-oriented region was larger than in the off-cube grain. The grain size in the cube-oriented region decreased with decreasing hydrogen content. From these facts and the result of TDS, supersaturated hydrogen atoms were presumed to segregate to low angle grain boundaries, the boundaries between cube-oriented grains, which can provide the driving force for the abnormal grain growth.

Thermodynamic Study on Hydrogen Generation from Different Glycerol Reforming Processes

This work is to study the thermodynamic property of a glycerol aqueous reforming process to generate hydrogen for fuel cells. Three ways of processing glycerol have been considered: autothermal reforming, a combination of water aqueous reforming and oxidation; aqueous hydrogen peroxide reforming; and the water aqueous reforming process. Thermodynamic analysis on three of them has been carried out, and the results show that the side reaction of methanation in each process route leads to a dramatic decrease of hydrogen content in the gas product, which consequently should be limited kinetically. Comparison among them indicates that, in the absence of methanation, the hydrogen content produced from water aqueous reforming of glycerol is the highest, followed by that from autothermal reforming and that from aqueous hydrogen peroxide reforming. It has also been shown that the requirements of external energy input to sustain these reforming reactions appear inversely among them. Therefore, it can be concluded thermodynamically that the external energy can be reduced at the price of losing hydrogen yield due to the exothermic oxidation, which consumes hydrogen to release energy.

Vibrational nonequilibrium and electronic excitation in the reaction of hydrogen with oxygen behind a shock wave

A theoretical analysis of ignition and combustion processes in a hydrogen-oxygen mixture behind a shock wave is presented (1000 K ≤ T ≤ 2500 K; 2.0 atm ≥ P ≥ 0.3 atm). The experiments performed using stoichiometric mixtures with the detection of OH (2Σ+) and rich mixtures with the detection of OH (2Π) were interpreted in terms of a general kinetic approach. In this case, the apparent rate constant of the chain branching reaction H + O2 → O + OH was the only adjustable parameter. It was found that this rate constant increased with decreasing hydrogen content and exceeded equilibrium values. In this context, the mechanism of chain branching, which occurs through the formation of the vibrationally excited radical HO2(v), and the role of secondary vibrationally nonequilibrium O2 and O2(1Δ) molecules and the reaction H + O2(1Δ) → O + OH are discussed. New mechanisms of the formation and quenching of electronically excited OH(2Σ+) radicals, O(1 D) atoms, and O2(1Δ) molecules are considered. The results of a nonempirical (ab initio) analysis of molecular systems and the corresponding estimations of reaction rate constants were widely used.

Photoelectron spectroscopy and secondary ion mass spectrometry characterization of diamond-like carbon films

Photoelectron spectroscopy at different photon energies was used to optimize the photoexcitation cross section for valence band study of diamond-like hydrogenated carbon films. The electronic states of diamond-like carbon (DLC) were studied by synchrotron radiation photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. The valence band spectra measured at different excitation energies show the gradual emergence of the p– π band in relation to the sample annealing and ion bombardment amorphization. The p– π band of the annealed DLC was characterized by localized p z states whilst the formation of the amorphous carbon surface was accompanied by appearance of the delocalized p z states in the gap. Secondary ion mass spectrometry and thermal desorption spectroscopy showed that sample annealing was accompanied by hydrogen content decrease.

2020 ナノインデンテーションにおける高強度鋼の変形特性に及ぼす水素の影響(S16-2 物理的・力学的現象,S16 インデンテーションの物理と応用)

Nanoindentation was used to study the effect of dissolved hydrogen on the nano plastic deformation in engineering steel. In this study, the results of high strength steel, SCM435 and carbon steel, S15C were discussed. We focused on the hydrogen effect on both onset and the resistance of plastic deformation at nano scale. Nano hardness was found to be increased with increasing in hydrogen content in SCM435 steel. The displacement burst of indentation curve was observed in both materials. The result of SCM435 steel, however, exhibited large scatter due to the large surface roughness. We, thus, investigated the displacement burst which occurred in the same grain of S15C steel. The result revealed that hydrogen increased the indentation force which induced displacement burst. Contrary to this, this force value decreased with a decrease in hydrogen content.

Electronic and Vibration Spectra of Hydrogenated Carbon Single‐Wall Nanotubes

Carbon single‐wall nanotubes (SWNTs) were loaded with 5.4 wt.% H by exposing to a hydrogen pressure of 50 kbar at 500°C. Investigation of the optical transmission spectra showed that the hydrogenation significantly suppressed the high‐frequency conductivity σ of free carries in the SWNTs and also eliminated the band‐to‐band electronic transitions. Instead, a narrow line of the C‐H stretching vibrational mode appeared at 2845 cm−1. A gradual removal of hydrogen from the hydrogenated SWNTs by vacuum annealing at T≥500°C resulted in an approximately linear decrease in the intensity of this line with decreasing hydrogen content. This evidenced that most H atoms in the hydrogenated SWNTs were covalently bonded to the carbon atoms. The complete removal of hydrogen by vacuum annealing at 700°C partly restored σ and the intensity of the electronic transitions characteristic of the initial SWNTs.

Effect of process atmosphere on the mechanical properties of rapidly solidified powder metallurgy Al–Ti–Fe–Cr alloys

Highly heat-resistant Al 93.1Ti 2.3Fe 2.3Cr 2.3 (at.%) rapidly solidified powder metallurgy (RS P/M) alloy was prepared under a well-controlled atmosphere of highly purified argon gas. The Al 93.1Ti 2.3Fe 2.3Cr 2.3 RS P/M alloy exhibited high strength exceeding 300 MPa and good ductility with elongation of 11% at 573 K. Reduction of the H 2O partial pressure in the P/M processing atmosphere lead to suppression of pore formation and decreased hydrogen content in P/M alloys, resulting in improved mechanical properties of the powder-consolidated alloys under high-temperature service conditions.

Change of hydrogen concentration after ion beam irradiation on polyimide films with 100–400 °C annealing

Irradiation damage in the several thickness polyimide films induced by 2.0MeV He ions has been evaluated by Rutherford backscattering (RBS) and elastic recoil detection (ERDA) methods. For the samples without annealing, gradual decrease of hydrogen content has been observed with the increase of ion dose. After 5min annealing at 100°C, a large amount of hydrogen atoms disappeared suddenly. Then small and continuous depletion of hydrogen content was also observed after ion beam irradiation. After 5min annealing at 300°C, hydrogen concentration has recovered for the 100°C annealed film in the case of no ion beam irradiation. Initial depletion rate of hydrogen for annealing and change of hydrogen content for the successive ion beam irradiation was found to be dependent on the film thickness.