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Copyright of Special Steel is the property of Daye Special Steel Co. Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Electrodeposited chromium plating continues to be widely used in a number of specialized areas, such as weapons, transport, aerospace, etc. However, the formation of texture, hydrogen content and residual stress can degrade the serviceability and lead to material failure. The effect of post heat treatment processes on the relationship of texture, hydrogen content, residual stress and corrosion resistance of hexavalent [Cr(VI)] chromium coatings deposited on Cr–Ni–Mo–V steel substrates was investigated. Macrotexture was measured by XRD. Microtexture, dislocation density and grain size were studied by EBSD. With the increase of the heat treatment temperature, it was found that the fiber texture strength of the (222) plane tended to increase and subsequently decrease. Below 600 °C, the increase in the (222) plane texture carried a decrease in the hydrogen content, residual stress, microhardness and an increase in the corrosion resistance. In addition, crack density and texture strength were less affected by the heat treatment time. Notably, relatively fewer crack densities of 219/cm2, a lower corrosion current density of 1.798 × 10−6 A/dm2 and a higher microhardness of 865 HV were found under the preferred heat treatment temperature and time of 380 °C and 4 h, respectively. The hydrogen content and residual stress were 7.63 ppm and 61 MPa, with 86% and 75% reduction rates compared to the as-plated state, respectively. In conclusion, in our future judgement of the influence of heat treatment on coating properties, we can screen or determine to a certain extent whether the heat treatment process is reasonable or not by measuring only the macrotexture. [ABSTRACT FROM AUTHOR]

Copyright of Petroleum Refinery Engineering is the property of Petroleum Refinery Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In biological systems, nanobubbles (NBs) effectively enhance hydrogen molecule retention and scavenging reactive oxygen species (ROS), but the underlying mechanisms remain elusive. To investigate this, we prepared hydrogen NB water samples with consistent dissolved hydrogen levels but varying NB densities to explore their physicochemical properties and effects on green algae (Chlorella vulgaris) under oxidative stress induced by copper ions (Cu2+) and cadmium ions (Cd2+). The results indicated a strong correlation between the hydrogen NB number density and the 25 % inhibitory concentration of Cu2+ over 24 h, with ROS removal efficiency increased with the NB number density. Gas chromatography showed that the hydrogen NBs in the solution had a high gas density that enhanced hydrogen transport into C. vulgaris. With regard to mitochondrial activity, hydrogen NBs were observed to enhance the function of mitochondrial complexes I and V and increase the mitochondrial membrane potential. Experiments with C. vulgaris mitochondrial electrodes showed that the electron transfer rates increased significantly in the presence of hydrogen NBs. We concluded that the high gas density of hydrogen NBs augments intracellular hydrogen delivery and strengthens mitochondrial functions.

Copyright of Bányászati és Kohászati Lapok - Kohászat is the property of Hungarian Mining & Metallurgical Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effects of ultrasonic treatment on grain refinement and hydrogen removal in three kinds of magnesium alloys—Mg-3Ca, Mg-6Zn-1Ca, and AZ80 alloys—were investigated in this study. After ultrasonic treatment, the grains of the magnesium alloys were refined to varying degrees. The degassing effect was characterized by measuring the densities and hydrogen content of ingots. The results indicated that the application of ultrasonic treatment in these magnesium alloys was able to remove hydrogen and obviously refine the microstructure. In this experiment, both the measurement of the density of the ingots and the solid-state hydrogen measurement reflected the degree of degassing. The highest degassing efficiencies were 53.8%, 67.5%, and 34.9% for the Mg-3Ca, Mg-6Zn-1Ca, and AZ80 alloys, respectively. The lowest hydrogen content of the AZ80 alloy reached 8.2 cm3/100 g, and the corresponding tensile strengths were 174 Mpa, 79 Mpa, and 6.2%, which represented increases of 41.5%, 38.6%, and 87.9%, respectively. The cavitation effect and acoustic streaming effect with an appropriate ultrasonic treatment duration resulted in grain refinement, degassing, and the uniform dispersion of second phases. This can significantly improve mechanical properties and provide a basis for industrial production. [ABSTRACT FROM AUTHOR]

Blending hydrogen into natural gas can increase fuel reactivity and the risk of jet fires in case of pipeline leakage though it is an effective delivery method. In this work, horizontal jet fires of hydrogen-blended natural gas at various operating pressures and hydrogen content were investigated experimentally. The flame temperature, lift-off distance, and flame length were measured for the scenarios with 0%–50% hydrogen content (in volume fraction) and 200–800 Pa. Results show that with the increase of hydrogen content, the flame temperature rises while the lift-off distance and flame length decrease. The flame length is slightly affected when the hydrogen content is less than 10% and a maximum reduction in flame length is 13.7% as the blended hydrogen content increases to 50%. Further theoretical analysis suggested the dimensionless correlations of the temperature distribution along the jet axis, lift-off distance, and flame length with different hydrogen content, respectively. The research results may provide reference for the risk assessment of hydrogen-blended natural gas pipelines. • Experiments address the impacts of hydrogen on jet fire properties of natural gas. • A modified nondimensional model for temperature distribution is proposed. • Flame lift-off distance of different hydrogen content is analyzed dimensionless. • A normalized model is developed to predict the flame length for all hydrogen content. [ABSTRACT FROM AUTHOR]

Based on the visualized gas cloud explosion pipeline test platform, the influence of the sudden contraction structure on the deflagration characteristics of the hydrogen-methane-air gas cloud is investigated. The results show that the changes of flame propagation velocity, explosion overpressure, and flame temperature after deflagration of the premixed gas cloud all present three stages: rapid increase, rapid decline, and secondary acceleration caused by the sudden contraction of pipeline structure. The equivalence ratio significantly affects the hydrogen-methane-air detonation process in the sudden contraction of the pipe structure. As the hydrogen content increases, the flame propagation becomes faster and the explosion impact becomes greater. The formation of "Tulip" flame is closely related to the flame propagation speed. During the process of flame propagation, inertia dominates, causing the flame propagation speed to reach its first peak at the abrupt contraction structure. [Display omitted] • The effect of sudden contraction pipeline on premixed gas detonation is examined. • The detonation process of pre-mixed gas clouds undergoes three stages. • The speed of flame propagation is closely related to inertia. • The flame structure of the "tulip" is closely related to the flame speed. • The effect of hydrogen and equivalence ratio on deflagration is examined. [ABSTRACT FROM AUTHOR]

the results are presented for investigation of electrical conductivity of nano crystalline diamond (NCD) films with thickness of 0.5–0.6 microns grown on silicon Si(100) substrates by the CVD metho d using methane-hydrogen and methane-hydrogen-oxygen mixtures. By the metho d of heating in vacuum with using hydrogen analyzer AB-1, the concentration of hydrogen in the studied films was determined and the relationship between the content of hydrogen in the NCD film and its conductivity was estimated. It has been shown that high-temperature processing in vacuum at the temperature of 600°C leads to desorption of hydrogen from the films and to a significant increase in their resistance. [ABSTRACT FROM AUTHOR]

Key issues facing the development of hydrogen gas turbines include achieving low NOx emissions on hydrogen-enriched fuels, prevention of flashback and thermoacoustic instability. The present experimental investigation shows the fuel feasibility of MILD combustion and multi-nozzle array combustion with hydrogen-enriched fuels. The combustion characteristics, such as the range of combustion stability, NOx/CO emissions, and reaction zone distribution, have been determined for hydrogen contents ranging from 0% to 50% by volume. Compared to the MILD model combustor, the multi-nozzle array model combustor can achieve a broader range of stable combustion up to 40% by volume. As the hydrogen content increases from 0% to 40% by volume, the lean blowout (LBO) temperature of the multi-nozzle array model combustor decreases from 1600 K to 1400 K. When the hydrogen content reaches 50% of the volume, both the MILD model combustor and the multi-nozzle array model combustor exhibit thermoacoustic instability at high equivalence ratios. For the multi-nozzle array model combustor, NOx emissions are less than 20 ppm@15% O 2 and CO emissions are less than 30 ppm@15% O 2 in the adiabatic temperature range of 1400 K–2100 K. NOx emissions of the multi-nozzle array combustor are higher than that of the MILD combustor, but remain ultra-low due to the flue gas recirculation ratio. With increasing hydrogen content, the reaction zone becomes more concentrated along the axial and radial directions. The lift-off height of the reaction zone is 1.6 nozzle diameters at 40% by volume hydrogen content, which ensures the safety of the nozzles and prevent flashback. • Flue gas recirculation induced by high-speed jet ensures combustion stability for the multi-nozzle array model combustor. • The multi-nozzles array model combustor has excellent combustion stability with a hydrogen content of less than 40% Vol. • NOx emissions are less than 20 ppm@15%O 2 when the hydrogen content ranges from 0% to 40% Vol. • The reaction zone lift-off has achieved at 40% Vol hydrogen content which ensures the safety of the nozzles. [ABSTRACT FROM AUTHOR]

Diamond‐like carbon (DLC) has attracted much attention due to its unique properties such as excellent physicochemical and biological properties. Herein, DLC coatings are deposited on four different silicon substrates using a radio frequency plasma‐assisted chemical vapor deposition (RF‐PECVD) technique. The structure and mechanical properties of DLC coatings deposited on different types of silicon substrates under different powers are compared. The surface morphology of the samples is characterized by scanning electron microscopy. The surface roughness of DLC films deposited on different silicon substrates is measured by scanning probe microscopy (SPM). The structural changes of the coatings are investigated by visible Raman spectroscopy. The analysis of DLC films deposited on different silicon substrates reveals that the structure of DLC films deposited on silicon is affected by different crystal directions of silicon substrates (different atomic densities in different crystal directions) and different conduction modes (electronic conduction and hole conduction). Regarding the DLC films deposited on the same substrate, the overall performance of P‐type silicon is better at 150 W, and the overall performance of N‐type silicon is better when the deposition power is 100 W. [ABSTRACT FROM AUTHOR]

The relative proportions of different chemical components in wood tissues is one of the underlying factors that control wood properties. These proportions vary within and between woody tissues, and an accurate description of these variations is critical for parameterizing forest biogeochemical budgets and models. White spruce (Picea glauca (Moench) Voss) spacing intensities trials in the Petawawa Research Forest, Ontario, Canada, were sampled to evaluate variations in carbon (C), nitrogen (N), and hydrogen (H) concentrations between different tissue types, i.e., bark, cambium, knots, earlywood, latewood, and wood. Samples were freeze-dried and oven-dried to test the impact of the drying methods on these chemical elements. Freeze-dried C (51.14) and H (6.18) concentrations were significantly higher than those of oven-dried C (50.55) and H (6.06). Freeze-dried N (0.18) did not differ from oven-dried N (0.17). The spacing intensities impacted C, H, and N, with C content being higher in wider square spacings (4.3 m and 6.1 m), while the reverse was true for N and H, which exhibited higher content in smaller square spacings (1.2 m and 1.8 m). The results of this study also suggested that when it comes to the content of chemical elements, bark and knots should be treated as separate fuel types, whereas other woody tissues can be aggregated. [ABSTRACT FROM AUTHOR]

The new experimental setup has been built at the 11b channel of the IBR-2 research reactor at FLNP, JINR, to study the elemental composition of samples by registration of prompt gamma emission during thermal neutron capture. The setup consists of a curved mirror neutron guide and a radiation-resistant HPGe high-purity germanium detector. The detector is surrounded by lead shielding to suppress the natural background gamma level. The sample is placed in a vacuum channel and surrounded by a LiF shield to suppress the gamma background generated by scattered neutrons. This work presents characteristics of the experimental setup. An example of hydrogen concentration determining in a diamond powder made by detonation synthesis is given and on its basis, the sensitivity of the setup is calculated being ∼4 μg.

The effects of ultrasonic treatment on grain refinement and hydrogen removal in three kinds of magnesium alloys—Mg-3Ca, Mg-6Zn-1Ca, and AZ80 alloys—were investigated in this study. After ultrasonic treatment, the grains of the magnesium alloys were refined to varying degrees. The degassing effect was characterized by measuring the densities and hydrogen content of ingots. The results indicated that the application of ultrasonic treatment in these magnesium alloys was able to remove hydrogen and obviously refine the microstructure. In this experiment, both the measurement of the density of the ingots and the solid-state hydrogen measurement reflected the degree of degassing. The highest degassing efficiencies were 53.8%, 67.5%, and 34.9% for the Mg-3Ca, Mg-6Zn-1Ca, and AZ80 alloys, respectively. The lowest hydrogen content of the AZ80 alloy reached 8.2 cm3/100 g, and the corresponding tensile strengths were 174 Mpa, 79 Mpa, and 6.2%, which represented increases of 41.5%, 38.6%, and 87.9%, respectively. The cavitation effect and acoustic streaming effect with an appropriate ultrasonic treatment duration resulted in grain refinement, degassing, and the uniform dispersion of second phases. This can significantly improve mechanical properties and provide a basis for industrial production.

Hydrogen ingress into zirconium cladding can cause embrittlement and affects the service safety of nuclear fuel cladding. Traditional hydrogen analysis methods like hydrogen determination instrument method and metallographic method, can only give the hydrogen content or density in a small area of the sample, however, the hydrogen distribution within the zirconium alloy cannot fully understand owing to limited scope of methods. In addition, those methods require the zirconium alloy to be cut, which prevents any opportunity for other performance analysis. A nondestructive analysis of hydrogen content and distribution is helpful to predict and evaluate zirconium alloy cladding service performance. Neutron has a higher sensitivity to hydrogen than the other elements (Zr, Sn, Fe, Nb et al.) in commercial zirconium cladding. Therefore, the hydrogen in zirconium alloys can easily be seen by neutron imaging method. Herein, the neutron tomography for threedimensional (3D) hydrogen distribution analysis and quantitative determination in hydrided zirconium alloys were introduced. A series of ZrSnNb alloy calibration samples with designed hydrogen concentrations up to 1 150 ppm were prepared, and studied using neutron tomography. In this way, the 3D hydrogen distribution of the calibration samples was obtained and the quantitative relationship between the hydrogen contents and image gray values was determined. It is observed that the image gray value increases linearly with the hydrogen content. Accordingly, the hydrogen content and distribution in hydrided samples are determined accurately. In addition, the metallographic method and inert gas pulse infrared absorption method were used to verify the feasibility of quantitative method for hydrogen distribution in zirconium alloys with neutron tomography. The hydrogen content and distribution determined using neutron tomography are consistent with the results of contrast methods. Consequently, neutron tomography can be efficient for 3D hydrogen distribution analysis and quantitative determination in hydrided zirconium alloys. This work provides a threedimensional, nondestructive testing method for the study of hydrogen distribution and content in zirconium alloy cladding, which can provide technical support for its optimization of manufacturing process and improvement of service performance.

This paper investigates the instability characteristics of CO/H2/air and CH4/H2/air mixtures in a narrow channel under standard temperature and pressure conditions. The CO/H2 mixture exhibits a greater overpressure growth rate and maximum explosion overpressure as compared to the CH4/H2 mixture at the same hydrogen content. As the hydrogen content increases, the maximum explosion overpressure (Pmax) value increases, while the corresponding time (θ) value gradually decreases. The maximum explosion overpressure of CH4/H2 and CO/H2 mixtures is 28.27 kPa and 25.09 kPa, respectively. The flame wrinkles to form cells due to the Darius-Landau instability, and the interaction between the vortex tube and premixed flame affects the structure of turbulent premixed combustion. The oscillation frequency of the overpressure increases with increasing hydrogen content, and the oscillation belongs to the Helmholtz oscillation. The CO/H2 mixtures exhibit greater flame thickness than CH4/H2 mixtures, resulting in lower Peclet numbers and therefore greater relative importance of heat losses. As the hydrogen content increases, the sensitivity coefficient of R99 (OH + CO <=> H + CO2) in the CO/H2 mixture gradually decreases, while the sensitivity coefficients of R38 (H + O2 <=> O + OH) and R84 (OH + H2 <=> H + H2O) increase. The elementary reaction R38 plays a leading role in increasing the laminar burning velocity of the CH4/H2 mixture. The trend of R38 variation in the two mixtures is opposite with increasing hydrogen content. [ABSTRACT FROM AUTHOR]

The hydrogenation behavior of Ti44Al6Nb1Cr2V (at%) alloy at temperature range of 1373–1693 K and its effect on microstructure and room-temperature mechanical properties were studied systematically in this study. The results show that hydrogen content increases with the increase in temperature, and the maximum hydrogen content is 0.126 wt% at 1693 K. The heat of solution of hydrogen is calculated as 82.9 kJ·mol−1 by curve fitting, indicating that hydrogen absorption in TiAl alloys is endothermic. Hydrogen promotes the lamellar colony size because hydrogen promotes the diffusion of elements. Hydrogen stabilizes B2 phase during hydrogenation resulting in more residual B2 phase in the hydrogenated alloy. The nanohardness and elastic modulus decrease after hydrogenation due to that hydrogen weakens the bonds. The Ti44Al6Nb1Cr2V alloy exhibits higher plasticity and lower flow stress hydrogenation with 0.039 wt% H, and the ultimate compressive strength decreases from 1220 to 1130 MPa, while the fracture strain is enhanced by 26%. [ABSTRACT FROM AUTHOR]

The casting table with lubricating oil and wiper is applied simultaneously to produce super-high-strength 7055 aluminum alloy (Al7055) ingots, and 30 T Al7055 ingots with a diameter of 582 mm were cast successfully. In this study, the microstructure and macrosegregation of the ingots were investigated using an optical microscope (OM). The research results show that the hydrogen content in the liquid metal can be decreased from 0.198 mL/100 g Al to 0.103 mL/100 g Al when three rotors are used in the degassing tank. Compared with the conventional hot-top casting table, the surface quality can be improved by using the casting table with oil lubrication. The temperature gradient between the ingot center and edge can be decreased by using the wiper during the casting process from 320 °C to 150 °C, the cracking tendency caused by the ingot temperature gradient can be decreased, the segregation layer thickness is decreased by about 87%, and the ingot can be homogenized at a high temperature by using the heat of the feed itself. [ABSTRACT FROM AUTHOR]

Diamond-like-carbon "DLC" coatings can be deposited in many different ways, giving a large range of material properties suitable for many different types of applications. Hydrogen content significantly influences the mechanical properties and the tribological behavior of DLC coatings, but its determination requires techniques that are not available in many research centers. Thus, it is important to find alternative indirect techniques, such as Raman spectroscopy or nanoindentation (hardness measurements), which can give comparative and indicative values of the H contents in the coatings, particularly when depositions with a reactive gas flow are being studied. In this work, "DLC" composite coatings with varying H content were deposited via Physical Vapor Deposition (PVD) magnetron sputtering in a reactive atmosphere (Ar + CH4). An Ion Beam Analysis was used to determine the elemental depth profile across the coating thickness (giving both average C:W:H ratios and film density when combined with profilometer measurements of film thickness). The hardness was evaluated with nanoindentation, and a decrease from 16 to 6 GPa (and a decrease in the film density by a factor of two) with an increasing CH4 flow was observed. Then, the hardness and Raman results were correlated with the H content in the coatings, showing that these indirect methods can be used to find if there are variations in the H content with the increase in the CH4 flow. Finally, the adhesion and tribological performance of the coatings were evaluated. No significant differences were found in the adhesion as a function of the H content. The tribological properties presented a slight improving trend with the increase in the H content with a decrease in the wear rate and friction. [ABSTRACT FROM AUTHOR]

Light elements alloying with metallic Fe can change the properties and therefore play a key role in the structure and dynamics of planetary cores. Hydrogen and silicon are possible light elements in the rocky planets' cores. However, hydrogen storage in Fe-Si alloy systems remains unclear at high pressures and high temperatures because of experimental difficulties. Taking advantage of pulsed laser heating combined with high-energy synchrotron X‑ray diffraction, we studied reactions between FeSi and H in laser-heated diamond-anvil cells (LHDACs) up to 61.9 GPa and 3500 K. We found that under H-saturated conditions the amount of H alloying with FeSi (0.3 and <0.1 wt% for the B20 and B2 structures, respectively) is much smaller than that in pure Fe metal (>1.8 wt%). Our experiments also suggest that H remains in the crystal structure of FeSi alloy when recovered to 1 bar. Further density functional theory (DFT) calculations indicate that the low-H solubility likely results from the highly distorted interstitial sites in the B20 and B2 structures, which are not favorable for H incorporation. The recovery of H in the B20 FeSi crystal structure at ambient conditions could open up possibilities to understand geochemical behaviors of H during core formation in future experiments. The low-H content in FeSi alloys suggests that if a planetary core is Si-rich, Si can limit the ingassing of H into the Fe-rich core. [ABSTRACT FROM AUTHOR]

The article is devoted to the optimization of the degassing parameters of the AlSi9Cu3(Fe) alloy. The alloy was degassed with a solid degasser (Ecosal) and nitrogen or argon. The variable parameters were time and type of degasser. The test castings were made in permanent molds with an internal diameter of 25 mm and a length of 150 mm. The effect of the degassing time and the amount of degasser on the mechanical properties, as well as the hydrogen content and density index were investigated. The ALU SPEED TESTER developed by FMA was used to test the hydrogen content and the density index. Magmasoft software was used to design the geometry of the test castings. A significant effect of the solid degasser and degassing time on both the density index and the hydrogen content was demonstrated. Replacing nitrogen with argon did not bring any significant improvement in the above-mentioned parameters. The effect of degassing parameters on the mechanical properties of the EN AC-46000 alloy was much less significant, but was still visible. The optimal degassing parameters needed to obtain the highest strength parameters of the EN AC-46000 gravity die castings were determined. [ABSTRACT FROM AUTHOR]

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effect of ultrasonic treatment parameters, including ultrasonic treatment duration, frequency resonance, and treatment temperature, on the degassing of Mg-3.03Ca alloys was investigated. The results indicated that the optimum degassing efficiency could be obtained under the ultrasonic resonant condition. When applying ultrasonic treatment for 90 s with 150 W at 700 °C, the minimum hydrogen content and the highest degassing efficiency are obtained, respectively (42.8 cm3/100 g and 27.5%). The ultrasonic treatment can remove the gas from the melt and refine the microstructures. Finally, the mechanism of ultrasonic degassing and refinement was analyzed. [ABSTRACT FROM AUTHOR]

Hydrogenated microcrystalline silicon (μc-Si:H) thin films were deposited by an radio frequency (RF) (13.56 MHz) magnetron sputtering at different substrate temperatures (100–300 °C), and the influences of substrate temperature on the growth and properties of μc-Si:H thin films were investigated. Surface roughness and crystallinity of the thin films increase as substrate temperature increases. And all thin films are at the transition region (Xc = 49.2 %~61.0 %). The μc-Si:H thin films deposited at lower substrate temperature (≤200 °C) represent a weak (220) preferred orientation, while the thin films deposited at higher substrate temperature (≥250 °C) exhibit a weak (111) preferred orientation. The μc-Si:H thin films have a dense structure, and the structural compactness of the thin films slightly increases with substrate temperature increasing. The Fourier transform infrared spectroscopy (FT-IR) results indicate that the μc-Si:H thin films have a low hydrogen content (3.9 at%–5.6 at%), which is in favor of reducing light-induced degradation effect. [ABSTRACT FROM AUTHOR]

TC21 alloy is hydrogenated under different initial hydrogen pressures at hydrogenation temperatures in the range of 450 °C–850 °C. Hydrogen absorption characteristic and kinetics during the heat preservation stage and cooling stage, hydrogen content and activation energy are investigated. The hydrogen absorption reaches equilibrium first at higher hydrogenation temperature and initial hydrogen pressure during the heat preservation stage. The hydrogen absorption reaches equilibrium first at lower hydrogenation temperature and initial hydrogen pressure during the cooling stage. Mechanisms of hydrogen absorption are analyzed during the heat preservation stage and the cooling stage. Phase compositions of the hydrogenated TC21 alloys are analyzed by XRD. Hydrogen content increases first and then decreases, then increases slightly, and finally decreases with the increase of hydrogenation temperature. Hydrogen content increases gradually with the increase of initial hydrogen pressure. The activation energy of hydrogen absorption in TC21 alloy is about 18.304 kJ/mol. [Display omitted] • H absorption mechanisms were diverse between heat preservation and cooling stage. • H content was affected by hydrogenation temperature and initial hydrogen pressure. • The activation energy of H absorption was about 18.304 kJ/mol. [ABSTRACT FROM AUTHOR]

Degradation of polypropylene (PP) and polystyrene (PS) surfaces under electron beam in ultra-high vacuum is studied by electron spectroscopy, pattern recognition, and atomic force microscopy. Effects on hydrogen, carbon sp2/sp3 content, and microstructure are quantified and correlated. Electron irradiation at 1500 eV causes hydrogen and C sp3 content decrease and surface morphology modification. Roughness changes from 29 to 15 nm on PP, whereas it remains 5 nm on PS. Decreasing C sp3 content in PP, contrary to PS, indicates C–H, C–C bonds scission and carbonization. Cross-linking predominates over carbonization in PS, confirming its better stability, in agreement with surface morphology data. [ABSTRACT FROM AUTHOR]

The casting table with lubricating oil and wiper is applied simultaneously to produce super-high-strength 7055 aluminum alloy (Al7055) ingots, and 30 T Al7055 ingots with a diameter of 582 mm were cast successfully. In this study, the microstructure and macrosegregation of the ingots were investigated using an optical microscope (OM). The research results show that the hydrogen content in the liquid metal can be decreased from 0.198 mL/100 g Al to 0.103 mL/100 g Al when three rotors are used in the degassing tank. Compared with the conventional hot-top casting table, the surface quality can be improved by using the casting table with oil lubrication. The temperature gradient between the ingot center and edge can be decreased by using the wiper during the casting process from 320 °C to 150 °C, the cracking tendency caused by the ingot temperature gradient can be decreased, the segregation layer thickness is decreased by about 87%, and the ingot can be homogenized at a high temperature by using the heat of the feed itself.

• Experiments extends hydrogen-blended natural gas jet fire data under high pressure. • A model based on initial conditions for jet flame length prediction is proposed. • An inverse method is employed to determine the weighting coefficients. • The accuracy of weighted multi-point source model is significantly improved. Adding hydrogen into natural gas significantly impacts the flame length and radiation characteristics of a jet fire. A series of large-scale hydrogen-blended natural gas (HBNG) jet fire experiments within a pressure range of 1.6 to 4 MPa and hydrogen contents varying from 0 % to 100 % are conducted in this paper, and the flame length and radiative heat flux are measured. The flame length of HBNG jet fire decreases by 5 % when hydrogen volume fraction increases from 0 % to 20 %, and decreases by 25 % when it increases to 100 %. The higher radiative heat flux region (>4kW/m2) remains essentially invariant when the hydrogen volume fraction is less than 20 %, while decreases significantly when it exceeds 50 %. A model based on initial conditions has been proposed, resulting in a significant 10 % improvement in the accuracy of flame length prediction. An inverse method is employed to determine the distribution of weighting coefficients under various hydrogen contents. As the hydrogen content increases, the enhanced momentum effect leads to a more uniform geometric shape and a more balanced distribution of weighting coefficients. The deviations between the predicted values of the radiation model and the experimental data indicate the accuracy of the radiation model is strongly dependent on the flame length prediction model. By employing the new flame length correlation formula and optimizing weighting coefficients, the accuracy of the weighted multi-point source (WMPS) model is significantly improved. [ABSTRACT FROM AUTHOR]

DLC coatings have been proven in formulated oils used in the automotive industry. The development of electric cars and its consequences on the future of the internal combustion engine makes it increasingly necessary that these coatings take their place in other applications where lubrication is generally of lower quality such as for example strips cold rolling where DLC shows significant potential both for production and finishing cold rolling. As a result, the interest of the behavior of these coatings in base oils takes on a new dimension. In this study, we explore the influence of the composition and the sp3/sp2 ratio on tribological behavior of DLC coatings in mineral and synthetic base oils. Hydrogenated DLC films deposited by conventional PECVD with various levels of hydrogen measured by Elastic Recoil Detection Analysis (ERDA) and non-hydrogenated DLC films deposited by PLD in the nanosecond mode (ns-PLD) and by cathodic arc evaporation, thus allowing to have different sp3/sp2 ratios confirmed by Multiwavelength Raman spectrometry, are tested and compared. The tests are performed on a ball-on-flat device with coated balls to better evaluate wear level. The behavior of highly hydrogenated DLC is of particular interest; with a very high level of durability in both base oils and friction level which comparatively varies between low and very low depending on the base oil. [ABSTRACT FROM AUTHOR]

The effect of ultrasonic treatment parameters, including ultrasonic treatment duration, frequency resonance, and treatment temperature, on the degassing of Mg-3.03Ca alloys was investigated. The results indicated that the optimum degassing efficiency could be obtained under the ultrasonic resonant condition. When applying ultrasonic treatment for 90 s with 150 W at 700 °C, the minimum hydrogen content and the highest degassing efficiency are obtained, respectively (42.8 cm3/100 g and 27.5%). The ultrasonic treatment can remove the gas from the melt and refine the microstructures. Finally, the mechanism of ultrasonic degassing and refinement was analyzed.

• Various cold metal transfer modes were utilized to deposit aluminum alloy walls. • The classical cold metal transfer mode produced walls with the lowest porosity. • The lowest hydrogen content was associated with the lowest porosity. • The majority of pore sizes range between 51 and 100 μm. • Most pore sphericities fall within the range of 0.61 to 0.7. The paper evaluates the effect of the welding mode of the CMT-based direct energy deposition arc (DED-Arc) process on the porosity of AA5087 aluminum alloy walls. Three welding modes were used to produce the walls: cold metal transfer (CMT), CMT-Pulse (CMT-P), and CMT Cycle-Step (CMT-CS) with heat inputs of 128.5 J/mm, 150.4 J/mm, and 152 J/mm, respectively. Porosity was assessed with a light microscopy (LM) and computer tomography (CT). The wall produced with the lowest heat input had the lowest average porosity of 0.641 % compared to CMT-P (0.799 %) and CMT-CS (0.766 %). CT results followed the same trend with porosity of 0.21 %, 0.32 %, and 0.27 % for CMT, CMT-P, and CMT-CS, respectively. The porosity level strongly correlates with the hydrogen content. The lowest porosity (CMT) at the lowest hydrogen content (5.29 ppm) is associated with lower hydrogen solubility in a molten pool at lower heat inputs. Most of the detected pores in all modes ranged from 51 to 100 μm in size. [ABSTRACT FROM AUTHOR]

We have demonstrated the growth of NbC-Amorphous C films that manifest a well-known nanocomposite structure (Klages and Memming, 1990; Nedfors et al., 2011; Sala et al., 2021). The films were deposited using reactive DC sputtering in a CH 4 /Ar atmosphere using an insulating substrate near room temperature. A metallic Nb sputtering target was sputtered in an argon/CH 4 atmosphere with a pressure range of 5.9 to 8.5 mTorr as the CH 4 flow was also varied. Crystalline NbC films were deposited at room temperature at the lowest CH 4 flow rate. The films exhibited ohmic electrical response at room temperature. The DC electrical resistivity scaled almost 4 orders of magnitude from 4.39 × 10−4 Ω-cm to 1.08 × 10−1 Ω-cm through changes in CH 4 flow rates and the resultant C content of the films. The large variation in resistivity cannot be attributed to the changes in sample composition, e.g. volumetric mixing. It is postulated from XRD and TEM results that the large change in resistivity is due to the decreasing NbC crystallite size with increasing CH 4. This leads to additional three-dimensional nanoscale intragranular interfaces and results in increased resistivity. X-ray reflectivity measurements were conducted, and the modelled film density was found to match the expected density for the film compositions as measured using X-ray photoelectron spectroscopy. Elastic recoil detection analysis (ERDA) was used to quantify H content of the films. The H content increased from 5.5 to 22 atomic percent with corresponding increase in CH 4 flow. Transmission electron microscopy utilizing precession electron diffraction (PED) was conducted and showed a strong dependence of crystallinity on CH 4 flow. A multilayer layer sample with varying CH 4 flowrates was examined with TEM and showed that films were amorphous in nature for flow rates above 10 SCCM CH 4 ; in agreement with XRD results. • Film density varies linearly with Nb content. • Electrical resistivity varies non-linearly changing by ∼4 orders of magnitude. • Film composition is readily controlled via methane gas flow. • ERDA showed H content 5.5 to 22 atomc percent. • TEM PED analysis showed films became amorphous at flow rates >10 SCCM. [ABSTRACT FROM AUTHOR]

• Premixed methane-hydrogen-air flame evolution and pressure dynamics are captured. • The relationship between flame characteristic and laminar burning velocity is analyzed. • Kinetic factors affecting laminar burning velocity are revealed. This work is aimed at exploring flame evolution and pressure dynamics of methane-hydrogen-air explosion experimentally and numerically by changing equivalence ratio and hydrogen content. For the flame evolution, the smooth distortion vanishes at equivalence ratio of Ф = 1.4, the prominent cellular structure and distorted tulip flame start to form with increasing hydrogen content. For the pressure dynamics, as the equivalence ratio increases, both maximum explosion overpressure and maximum pressure rise rate increase and then decrease, and both of them continue to increase with increasing hydrogen content. H + O2 = O + OH is the main elementary reaction with positive effect on the laminar burning velocity. The main elementary reactions with negative effects are H + O2(+M) = HO2(+M) and CH3 + H(+M) = CH4(+M). H radical always dominates on the rich side or the lean, stoichiometric side with high hydrogen content. As the hydrogen content increases, the main oxidation pathways of CH4 undergoes the transfer from CH4 → CH2(S) → CH2 → CO to CH4 → CH2(S) → CH2 → CH → CO → CO2. The research results are helpful to improve combustion efficiency of internal combustion engine and ensure process safety of hydrogen doped natural gas pipeline transportation. [ABSTRACT FROM AUTHOR]

• The variation of hydrogen content after carburizing and heat treatment is studied. • There is only one peak at around 415 ℃ after forging and tempering. • There is an additional peak at around 255 ℃ after gas carburizing and quenching. • There is no hydrogen absorption during the low-pressure carburizing. • The absorbed hydrogen have no evident effect on the fatigue properties of the steel. 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. [ABSTRACT FROM AUTHOR]

• The effect of H content on pyrolytic pathways of fluorinated alkanes is unveiled. • The thermal stability of fluorinated alkanes decreases with the rising H content. • Fluorinated alkanes with lower H contents yield more suffocating pyrolytic products. • Yields of flammable alkenes, corrosive and toxic products rise with the H content. Halon extinguishants have been prohibited due to the caused damages to the stratospheric ozone layer. For Halon replacement, ozone-friendly fluorinated alkanes are used as transitional Halon substitutes. In order to unravel the relationship between chemical structures and fire-extinguishing performance of fluoroalkane agents, we investigated the effects of hydrogen content on pyrolytic and fire-extinguishing mechanisms of fluoroalkanes including HFC-236fa (CF 3 CH 2 CF 3), HFC-227ea (CF 3 CHFCF 3) and PFC-218 (CF 3 CF 2 CF 3), which may provide some guidance on efficient exploration of new substitutes for Halon extinguishant. Both the experimental and theoretical methods were employed in this study. It was found that the energy barrier of CF 3 · fire extinguishing free radical generated by the three fluorinated alkanes increases slightly with the increase of H content. The reduction of hydrogen content notably promotes the thermal stability of fluorinated alkanes and the productivity of incombustible pyrolytic products. The HFC-236fa agent exhibits remarkable cooling effect upon the combustion cycle via endothermic pyrolysis, while the PFC-218 agent extinguishes flame predominantly through the dilution effect on the flammable gas. Remarkably, a lower hydrogen content effectively inhibits the production of flammable alkenes, corrosive and toxic pyrolytic products. Although PFC-218 agent exhibits the highest fire-extinguishing concentration (FEC) relative to the other two counterparts, the PFC-218 manifests the subtlest combustion promotion and releases the least corrosive products, which inhibits the suddenly risen temperature in the combustion region and reduces corrosive and poisonous products. These findings provide new understanding and guidance on the molecular designing and screening of environmental-friendly and efficient Halon substitutes. [Display omitted] [ABSTRACT FROM AUTHOR]

• Change in olefin selectivity of silver(I) ion/IL stationary phase was studied. • The effect of temperature, hydrogen content, and duration was investigated by GC. • Higher heating temperatures provided a greater decrease in selectivity. • A more remarkable decline in selectivity was caused by a greater hydrogen content. • A ternary gas mixture exhibited unexpected alkyne/alkene selectivity change. The olefin/paraffin selectivity offered by ionic liquid (IL) stationary phases can be enhanced through the addition of silver(I) ion, which is well-known to undergo selective complexation with unsaturated compounds. However, such stationary phases often suffer from the loss of chromatographic selectivity as silver(I) ion can be reduced to elemental silver. To maintain the separation performance of silver(I) ion/IL stationary phases, an understanding of factors and conditions that promote the reduction of silver(I) ion is needed. In this study, capillary gas chromatography columns featuring a stationary phase consisting of the 1-decyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C 10 MIM+][NTf 2 −]) IL impregnated with [Ag+][NTf 2 −] were examined to investigate the effects of temperature, hydrogen content in exposure gas stream, and time of heating/exposure events on olefin selectivity. Retention factors of representative analytes, such as C 6 olefins and paraffins as well as aromatic compounds, were measured after subjecting the columns to the aforementioned conditions, followed by an evaluation of selectivity factors over time. Selectivity factors of olefins and aromatic compounds were observed to decrease significantly when the stationary phases were heated to temperatures higher than 110°C as well as being subjected to mixed gas streams containing greater than 50 mol% of hydrogen. As constant column heating temperatures were applied under exposure gas mixtures containing hydrogen and nitrogen, a gradual decrease in analyte selectivity factors was observed under prolonged periods of time. However, application of a ternary gas mixture comprised of 25/50/25 mol% hydrogen/nitrogen/methane resulted in an increase in the 3-hexyne/ cis- 2-hexene selectivity when measured at 120°C for 60 h, due to a smaller decrease in the retention factor of 3-hexyne compared to cis- 2-hexene. [ABSTRACT FROM AUTHOR]