Variation Of Hydrogen Content Research Articles

The impact of frequency and power on the ultrasonic purification of aluminum alloy

In this study, the variations in hydrogen content and oxide content in alloys under 0 W, 500 W, 1000 W, 1500 W, 2000 W, 2500 W, 3000 W, and at 20 kHz, 30 kHz, 40 kHz were investigated. Hydrogen content was assessed using porosity and computed tomography, while oxygen content in the alloy was measured using element analyzer and elemental scanning. Compared to other conditions, the melt had the lowest hydrogen and oxide contents at a frequency of 20 kHz and an ultrasonic power of 2500 W, with values of 0.099 cm3/100 g and 0.0015 %, respectively. Experimental observations also indicate that the variations in hydrogen content and oxide content in the alloy during ultrasonic treatment are almost similar. In most cases, lower hydrogen content corresponds to lower oxide content in the same alloy. This is because hydrogen bubbles and oxides become a single entity. At the same time, ultrasonic purification increases the tensile strength of the alloy to 200.1 MPa and the elongation rate to 0.72 %. This study primarily investigates the relationship between hydrogen bubbles and oxides in aluminum melt under different ultrasonic frequencies and power levels, providing significant reference for the purification of various fluids under ultrasonic fields.

Variation of hydrogen content in gear steel after carburizing and heat treatment and its effect on fatigue properties

In this study, the variation of hydrogen contents in gear steel 17Cr2Ni2MoVNb after gas carburizing, low-pressure carburizing and heat treatment was investigated by means of thermal desorption spectrometry (TDS) analysis. The results showed that there was an additional peak at around 255 ℃ in the TDS curves for the specimens after gas carburizing and quenching in comparison with that for the specimen after low-pressure carburizing, which was absorbed presumably from the high temperature environmental gas. The results of fatigue tests showed that the fatigue limits for the specimens after gas carburizing with the additional hydrogen desorption peak and after low-pressure carburizing without the additional hydrogen desorption peak were both about 980 MPa. It could be attributed to the fact that the absorbed hydrogen content in the gas-carburized specimens was decreased from 0.084 mass ppm to 0.057 mass ppm after fatigue tests, which was too small to have evident effect on the fatigue properties of the steel.

Effect of current density on the texture, residual stress, microhardness and corrosion resistance of electrodeposited chromium coating

Textures and residual stresses are generated during electrodeposition of chromium coatings, which directly affect the performance of the coating. In this work, the variations of texture, hydrogen content, residual stress, microhardness and corrosion resistance of chromium deposited from hexavalent [Cr(VI)] chromium bath using direct current deposited technique were investigated. Electrodeposition experiments were carried out on the low carbon steel substrate by varying the key variable current density. The macrotexture of the coatings was studied by XRD. The crystal orientation and dislocation density were analyzed by EBSD. Residual stress was measured by the indentation method. The research demonstrated that a single preferred orientation on the (222) plane was found at current densities of 20 A/dm2, 35 A/dm2 and 50 A/dm2. At 40 A/dm2, a mixed preferred orientation on the (222) + (211) planes was discovered. Furthermore, the formation of the chromium coating texture was affected by the variation of hydrogen content, for higher hydrogen promoting grain growth along the (222) crystal plane. Notably, the microstructure-property relationship was developed. At the single preferred orientation of (222) plane, the corrosion resistance was more favorable. At the mixed preferred orientation of (222) + (211) planes, the coating surface achieved higher microhardness, but formed higher residual stress and more microcracks. Moreover, the better electroplating parameter was proposed. At 35 A/dm2, the coating had the fewer microcracks and the better overall performance. The higher microhardness of 753 HV was found. The more favorable corrosion resistance was discovered, with the breakdown potential and passive current density of 804.7 mV and 2.220 × 10−6 A/dm2. The lower residual stress of 61 MPa was found, which was about 81 % lower than the maximum stress. It was significant in industry for the enhancement of the service life of substrate and the optimization of the chromium coating process.

Investigation of the Effect of Disorder on the Tauc Edge of Hydrogenated Amorphous Silicon Using Dunstan’s Bandgap Fluctuations Model

The optical absorption edge in both Urbach and Tauc regions are analyzed for hydrogenated amorphous silicon optical data of Cody et al and Viturro and Weiser . Dunstan’s model, introduces disorder into the band-band absorption through a linear exponential distribution of local energy gaps. This model has a simple mathematical form and has a clear physical meaning in comparison to the somewhat similar models of O’Leary and Guerra, yet Dunstan’s model is unjustly neglected in literature. The most important physical parameter of the model is the energy gap parameter- Eo, which represents the separation between the valence and conduction band edges, it can be considered as the mobility gap of the material. Dunstan’s model is found successful in capturing the optical data of Cody et al and, Viturro and Weiser. A plot of the energy parameters of the Dunstan and Cody models, Eo against Eopt respectively, was proposed here to separate the masking contribution of tail-related absorption from the real change of the band gap, and was found fruitful for this purpose. This is because Eo is a function only of the separation between valence and conduction band edges, while the meaning of the optical energy Eopt is ambiguous because it is also a function of absorption due to tail-related absorption that results from disorder. This simple plot of Eo vs. Eopt , through the slope ΔEo/ΔEopt of the fitting straight line , was capable of distinguishing the different relative contributions of disorder between Cody et al and Viturro and Weiser optical data, Eo value was found less sensitive to hydrogen content variation for Viturro and Weiser data which is interpreted due to their better control of the thin film deposition process. Keywords: optical energy gap, absorption coefficient, amorphous semiconductor, mobility gap

Economic Analysis of Methanating CO2 and Hydrogen-Rich Industrial Waste Gas in Depleted Natural Gas Reservoirs

This study explored underground biomethanation as a means to achieve carbon neutrality and promote carbon circular utilization by methanating CO2 and hydrogen-rich industrial waste gas in depleted natural gas reservoirs (MECHIG). This approach not only aids the development of carbon capture, utilization, and storage (CCUS) technologies, but also effectively processes industrial waste gas, thereby reducing pollutant emissions. In order to verify the feasibility of the MECHIG concept, this study builds upon the analysis of the MECHIG process overview and employs the net present value (NPV) analysis method to investigate its economic viability. Additionally, the study conducts a sensitivity analysis on six factors, namely methanation efficiency, facility site investment, hydrogen content in waste gas, natural gas prices, operation and maintenance (O&M) investment, and CO2 capture and injection prices. The results indicate the following: (1) Under the baseline scenario, the NPV of the MECHIG concept is approximately CNY 5,035,100, which suggests that the concept may be economically viable. (2) The fluctuation in natural gas prices has the most significant impact on NPV, followed by facility site investment and methanation efficiency. In contrast, the variations in hydrogen content in waste gas, O&M investment, and CO2 capture and injection prices have relatively smaller effects on NPV. (3) To ensure the economic feasibility of the concept, the acceptable fluctuation ranges for the factors of methanation efficiency, facility site investment, hydrogen content in waste gas, natural gas prices, O&M investment, and CO2 capture and injection prices are −16.78%, 5.44%, −32.14%, −4.70%, 14.86%, and 18.56%, respectively.

Acoustic Plasmons in Nickel and Its Modification upon Hydrogen Uptake

In this work, we study, in the framework of the ab initio linear-response time-dependent density functional theory, the low-energy collective electronic excitations with characteristic sound-like dispersion, called acoustic plasmons, in bulk ferromagnetic nickel. Since the respective spatial oscillations in slow and fast charge systems involve states with different spins, excitation of such plasmons in nickel should result in the spatial variations in the spin structure as well. We extend our study to NiHx with different hydrogen concentrations x. We vary the hydrogen concentration and trace variations in the acoustic plasmons properties. Finally, at x=1 the acoustic modes disappear in paramagnetic NiH. The explanation of such evolution is based on the changes in the population of different energy bands with hydrogen content variation.

Simulation of the effect of evaporation and gas composition during plasma spheroidization of titanium particles

A 3D model was proposed that describes the in-flight behavior of titanium particles in the plasma environment, developed in the commercial CFD Ansys Fluent software, which described the heating of particles. The rate of evaporation was investigated based on the gas compositions, and the mass evaporated on the surface of the particle along the trajectory under plasma conditions. To evaluate the spheroidization rate of titanium particles, the calculated temperature and flow histories were established. Significant heat exchange behaviors are presented due to the variations in hydrogen content and feed rate. The simulation results have demonstrated that the range of 0-4% of H2 and at a low injection feed rate of 3-10 g/min minimized the evaporation rate and increased the spheroidization rate of particles.

Hydrogen abundance estimation and distribution on (101955) Bennu

Asteroids were likely a major source of volatiles and water to early Earth. Quantifying the hydration of asteroids is necessary to constrain models of the formation and evolution of the Solar System and the origin of Life on Earth. The OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) mission showed that near-Earth asteroid (101955) Bennu contains widespread, abundant hydrated phyllosilicates, indicated by a ubiquitous absorption at ~ 2.7 μm. The objective of this work is to quantify the hydration—that is, the hydrogen content—of phyllosilicates on Bennu's surface and investigate how this hydration varies spatially. We analyse spectral parameters (normalized optical path length, NOPL; effective single-scattering albedo, ESPAT; and Gaussian modeling) computed from the hydrated phyllosilicate absorption band of spatially resolved visible–near-infrared spectra acquired by OVIRS (the OSIRIS-REx Visible and InfraRed Spectrometer). We also computed the same spectral parameters using laboratory-measured spectra of meteorites including CMs, CIs, and the ungrouped C2 Tagish Lake. We estimate the mean hydrogen content of water and hydroxyl groups in hydrated phyllosilicates on Bennu's surface to be 0.71 ± 0.16 wt%. This value is consistent with the hydration range of some aqueously altered meteorites (CMs, C2 Tagish Lake), but not the most aqueously altered group (CIs). The sample collection site of the OSIRIS-REx mission has slightly higher hydrogen content than average. Spatial variations in hydrogen content on Bennu's surface are linked to geomorphology, and may have been partially inherited from its parent body.

Comparison of the Effects of Environmental Treatments on Hydrogen Concentration and Energy Gap Variations of Hydrogenated Amorphous and Polymorphous Silicon Films Prepared by PECVD Technique

Hydrogen to silicon (Si–H) bond concentration and strength play important roles in high quality hydrogenated amorphous silicon layers prepared by PECVD techniques. In this paper, a number of amorphous and polymorphous Si layers have been deposited at different plasma conditions where a wide range of hydrogen concentration in the films are obtained. Some of the samples were stored in free air and the others in nitrogen for eight days. The layers were analyzed using AFM, FTIR, Raman, UV–Visible, and TEM immediately after deposition and after treatments. The results indicate that in the amorphous films with appreciable amount of embedded silicon nanocrystals, the variation of hydrogen content behaves differently than that of the amorphous films. It has been observed that treatment in the air increases the energy gap of the nanocrystals surrounded by oxide shells, formed around the surface nanocrystals, due to the quantum confinement effects.

Research of the influence of electron beam welding of titanium alloys on hydrogen distribution in the weld

The paper presents the results of analyzing distribution of hydrogen in welded joints obtained by electron beam welding of titanium alloys VT20 and VT23. The distribution of hydrogen in the cross section of welded joints was measured in the area of the weld, in the heat-affected zone and in the base metal by means of spectral analysis using low-voltage pulse discharge on the spectrograph ISP-51. It was established that hydrogen peaks in fixed joints obtained by electron beam welding, unlike argon arc welding, are located not only in the heat-affected area, but also in the сentral part of the welded joint. Chemical analysis of fractures of fixed joints investigated with the aid of a scanning electron microscope Hitachi S-3400N showed that the pores in the welded joints made by electron beam welding occur due to the desorption of capillary-condensed contaminants located in the defects of the edge surface into the melt and due to selective grain boundary fusion because of insufficient temperature conditions of whole grain melting. It was found that emerging variations in hydrogen content, with formation of defects, are influenced by the temperature conditions of heating of the welded edges, the welding rate and the thickness of welded blanks.

Nanoscale Probing of Local Hydrogen Heterogeneity in Disordered Carbon Nitrides with Vibrational Electron Energy-Loss Spectroscopy.

In graphitic carbon nitrides, (photo)catalytic functionality is underpinned by the effect that residual hydrogen content, manifesting in amine (N-H x) defects, has on its optoelectronic properties. Therefore, a detailed understanding of the variation in the local structure of graphitic carbon nitrides is key for understanding structure-activity relationships. Here, we apply aloof-beam vibrational electron energy-loss spectroscopy in the scanning transmission electron microscope (STEM) to locally detect variations in hydrogen content in two different layered carbon nitrides with nanometer resolution. Through low dose rate TEM, we obtain atomically resolved images from crystalline and disordered carbon nitrides. By employing an aloof-beam configuration in a monochromated STEM, radiation damage can be dramatically reduced, yielding vibrational spectra from carbon nitrides to be assessed on 10's of nanometer length scales. We find that in disordered graphitic carbon nitrides the relative amine content can vary locally up to 27%. Cyano (C≡N) defects originating from uncondensed precursor are also revealed by probing small volumes, which cannot be detected by infrared absorption or Raman scattering spectroscopies. The utility of this technique is realized for heterogeneous soft materials, such as disordered graphitic carbon nitrides, in which methods to probe catalytically active sites remain elusive.

The effect of hydrogen content and welding conditions on the hydrogen induced cracking of the API X70 steel weld

The self-restraint testing was used to investigate the influence of hydrogen content, preheating, and post-heating on the sensitivity of welding of API X70 pipeline steel to hydrogen induced cracking (HIC). The variation of hydrogen content was applied using a low hydrogen electrode E8018-G and a high hydrogen (cellulosic) electrode E8010-P1. Diffusible hydrogen of these electrodes was measured by mercury displacement method. The average diffusible hydrogen content of cellulosic electrode E8010-P1 and low hydrogen electrode E8018-G were 43.6 and 1.1 ml/100 g of weld metal, respectively. The results of visual inspection, penetrant test, and macroscopic examination showed that welding with cellulosic electrode leads to cracking unless both preheating and post-heating are applied. However, in the case of low hydrogen electrode, cracking occurs only if no preheating or post-heating is applied. The microstructure of the welded specimens in different conditions by optical and scanning electron microscopy (SEM) showed that the dominant phase in the weld zone of all specimens is bainite. The microhardness profile displayed that hardness limitation (350 HV) cannot predict the sensitivity to cold cracking; therefore, other parameters such as hydrogen content should also be considered.

Variation in hydrogen content of vitrinite concentrates with rank advance

Vitrinite concentrates isolated from Indian Permian coals with mean random reflectance (Rr) ranging from 0.52% to 1.92% have been subjected to petrographic and ultimate analyses. The data set of vitrinite concentrates created has been used to study the variations of various chemical rank related parameters, viz. C, atomic O/C ratio, atomic H/C ratio and H, with Rr. The variations of C, atomic O/C and atomic H/C have manifested as continuous polynomial functions, while the variation of H is distinctly different. H is found to increase initially with Rr up to 0.9% Rr and then decreases with rank advance. The variation suggests maturation of vitrinite in the rank range has taken place via two distinct yet contiguous phases. The first phase of evolution is characterized by loss of oxygen with enrichment of hydrogen, while the second phase is marked by loss of hydrogen. The evolved phases could be best described by equations linking Rr with elemental composition as: Rr=−2.1618+0.0329C+0.0285H (C<85%) and Rr=−2.7569+0.0648C − 0.3350H (C>85%), where C and H stand for % carbon and % hydrogen, respectively on dmmf basis.

Mechanical properties of ultrananocrystalline diamond films modified by hydrogen concentration in deposition atmosphere

Ultrananocrystalline diamond (UNCD) films on silicon were prepared by microwave plasma chemical vapor deposition method using argon-rich CH4/H2/Ar plasmas. The grains with different sizes were obtained by deposition in different atmosphere and the sizes of grain were measured after the deposition by X-ray diffraction (XRD). The influences of the grain size on the development of the morphology of ultrananocrystalline diamond (UNCD) films and their mechanical properties have been investigated by variation of hydrogen content from 5% to 20% in the deposition atmosphere. Their morphology and topography have been characterized by scanning electron microscopy (SEM) and surface profilometer. The influences of the hydrogen concentration on the mechanical properties of the deposited UNCD films are investigated by using nano-indentation and nano-scratch tests. It was found that the grain size, growth rate and surface roughness are increased with the increase of the hydrogen concentration. This changes the morphology of the films from granular to needle-like clusters. It can also be seen that the elastic modulus is increased with the addition of hydrogen; the hardness increased monotonically from 5% to 15% hydrogen, then decreased for 20% hydrogen with the maximum at 15% hydrogen; and the elastic recovery is 72–78%. Hardness and toughness are all decisive for protecting nature of the coatings. The scratch tests proved a strong adhesion of the UNCD coatings up to 45mN and their protective effect on silicon substrates. The hydrogen has significant influence on the mechanical properties. Detailed experimental results and failure mechanisms for UNCD film deposition in argon-rich plasma are discussed. The deposited highly smooth UNCD film is also expected to be applicable in medical implants, surface acoustic wave (SAW) devices and micro-electromechanical systems (MEMS).

Hydrogen content variation for enhancing the lubricated tribological performance of DLC coatings with ester

There are many types of DLC (diamond-like carbon) coatings, which mainly differ from each other according to their hydrogen content, sp2 and sp3-bonded carbon atoms and alloying elements (such as Ti, Cr, W or Zr). The lubricated tribological performance of these coatings depends on the lubricant. Controversially, the same lubricant delivers different tribological performances with differently produced DLC coatings. It has been observed that the presence of hydrogen has a remarkable effect on the tribological performance of DLC coatings in inert and vacuum environments. In this paper, the hydrogen content of two different types of DLC coatings, a-C:H:Me (metal containing hydrogenated amorphous carbon) and a-C:H, was varied, in order to obtain an optimized tribological behavior with a synthetic ester (TMP ester). The tribological performance of the coatings with TMP ester is examined in a pin-on-disk tribometer. It could be shown that increasing the hydrogen content in a DLC coating improves their tribological performance with TMP ester. Besides, a-C:H type of coatings is found to be more suitable for TMP ester regarding low friction coefficients.

Spectroscopic ellipsometry studies on hydrogenated amorphous silicon thin films deposited using DC saddle field plasma enhanced chemical vapor deposition system

Hydrogenated amorphous silicon (a-Si H) films deposited on crystalline silicon substrates using the DC saddle field (DCSF) plasma enhanced chemical vapor deposition (PECVD) system have been investigated. We have determined the complex dielectric function, ε(E)=ε1(E)+iε2(E) for hydrogenated amorphous silicon (a-Si:H) thin films by spectroscopic ellipsometry (SE) in the 1.5–4.5eV energy range at room temperature. The results indicate that there is a change in the structure of the a-Si:H films as the thickness is increased above 4nm. This is attributed to either an increase in the bonded hydrogen content and, or a decrease of voids during the growth of a-Si:H films. The film thickness and deposition temperature are two important parameters that lead to both hydrogen content variation and silicon bonding change as well as significant variations in the optical band gap. The influence of substrate temperature during deposition on film and interface properties is also included.

The effect of hydrogen release at room temperature on the ductility of steel wire rods for pre-stressed concrete

The present study investigated the variation of reduction in area at fracture with the storage time of a high-carbon steel wire rod for pre-stressed concrete. The steel used in this study was an 11-mm diameter, hot-rolled and controlled-cooled wire rod produced without vacuum degassing. The wire hydrogen content and its reduction in area were measured for storage times up to 960h at room temperature. The hydrogen content decreased from 1.85ppm immediately after cooling to nearly 0.55–0.60ppm after 216h and then stabilized, while the reduction in area increased from 20% to around 37% during this same period of time. Analysis of the hydrogen content variation over time suggests that the release of hydrogen is responsible for an increase in the ductility of the steel. It was also shown, by comparing the results from two models regarding the amount of hydrogen release from the wire, that this phenomenon may be controlled by diffusion when reversible traps are present.

Structural and Magnetic Phase Transitions in ErFe2Hx Hydrides

Temperature dependences of the lattice parameters, magnetization and magnetic susceptibility have been measured for the ErFe2Hx hydrides with different hydrogen content x and for the ErFe2D3.1 deuteride. For the samples with a hydrogen content of about 3.1, structural transition from the cubic to the rhombohedral phase has been observed in the temperature range 280 – 310 K. Small variation of hydrogen content does not shift the transition temperature, but influences the amount of the low-temperature rhombohedral phase. The temperature dependence of magnetization shows up an anomaly in the range of the phase transition, which is due to the difference in the magnitudes of magnetic moments and exchange interactions in two phases. Structural and magnetic studies point to a diffusion nature of the phase transition. Upon heating the samples in vacuum there takes place decomposition of the hydride. The hydride with x = 1.6 which forms at the intermediate stage of decomposition possesses an ordering temperature higher than that for the parent ErFe2 compound.

Regional geology, depositional environment and maturity of organic matter of Early to Middle Jurassic coals, coaly shales, shales and claystones from the Eastern Pontides, NE Turkey

Jurassic coals, coaly shales, shales and claystones from the Eastern Pontides in NE Turkey have been investigated using microscopical, petrophysical and detailed organic geochemical methods in order to determine their catagenetic stage, to reveal the composition of the organic matter and to discuss the depositional environment. The Liassic–Dogger period in the Eastern Pontides was characterised by the presence of a rift system which resulted in rock units of very variable lithology and facies. Coal seams, ranging from a few centimetres to several decimetres and intercalated with shales, claystones and sandstones occur within the basal part (the Aggi Formation) as well as in the uppermost part (the Hamurkesen Formation) of the rift deposits. All coal seams investigated are at a catagenetic maturation stage corresponding to subbituminous B up to low volatile bituminous ranks. They represent a depositional environment of short-lived swamp areas with intense aerobic reworking of the higher plant detritus by heterotrophic bacteria, but with possible anaerobic microenvironments at deeper levels. At least some coal seams were influenced temporarily by marine ingressions. Most samples are impure humic coals with highly variable chemical compositions as indicated by the broad range of their hydrogen contents. This variation in hydrogen content is partly attributed to variable contributions of algal material. On the other side, considering several analytical results, the hydrogen variation is primarily due to bacterial reworking that affected the composition of the organic matter to variable extent and resulted especially in an enrichment of bacterial lipids. Bacterial reworking by an active microbial community within the upper layer of the peat swamp is inferred from elevated concentrations of iso-alkanes even exceeding those of the corresponding n-alkanes in several samples which, to the best of our knowledge, have not been observed with coals before.

A Dehydrogenation and Annealing Method of a-Si by Microwave

AbstractWe propose a new method for selective crystallization of amorphous silicon and source/drain ion impurities activation by microwave annealing. We have measured FTIR to investigate hydrogen content variation in PECVD a-Si film and examined the poly-Si grain structure by SEM. We have also observed the Raman spectroscopy in order to investigate the grain growth mechanism during microwave annealing.In our experiment, a-Si layer between microwave absorbing layers was fully crystallized in 60 seconds and hydrogen content of a-Si under microwave reflective layer was not varied after 20 minutes microwave annealing. These results indicate that proposed method may be implemented for fabricating a-Si and poly-Si TFTs on the same glass substrate. We have fabricated the poly-Si and a-Si TFTs employing microwave annealing for active layer crystallization and source/drain activation by our method.