Hydrogen Content Research Articles

Mechanism Analysis of the Reduction Process of the NiO-YSZ Anode of a Solid Oxide Fuel Cell by Hydrogen

Abstract Reduction of the nickel oxide-yttria stabilized zirconia (NiO-YSZ) anode is a significant step before the operation of a solid oxide fuel cell (SOFC). However, phenomena which occur during the reduction and their mechanism analyses are not summarized sufficiently. In this study, we investigated the influence of the hydrogen concentration, water vapor concentration of the reduction gas, Y2O3 content of the YSZ material of the anode, and temperature on the reduction process. The results showed that water vapor added to the hydrogen during reduction caused a temporary stasis period of the open circuit voltage. The length of the temporary stasis period was almost irrelevant to the water vapor concentration. During reduction, the length of the temporary stasis period of the open circuit voltage was negatively associated with hydrogen concentration and temperature, but positively associated with Y2O3 content of the YSZ material of the anode. After reduction, the SOFC showed better initial performance when the hydrogen concentration or the water vapor concentration during the reduction were higher. The classical shrinking core model can be used to explain these phenomena.

The nontrivial effects of annealing on superconducting properties of Nb single crystals

The effect of annealing on the superconducting properties of niobium single crystals was studied using optical, magnetic, and scanning tunneling microscopy (STM) methods. Pieces of the same crystal boule were studied before and after the annealing at 800 ∘C , 1400 ∘C , and near the melting point of niobium (2477 ∘C ). The initial samples had a high hydrogen content and low-temperature imaging revealed large hydrides (hundreds of micrometers) appearing below 190 K. The formation of these large precipitates is already completely suppressed by annealing at 800 ∘C . However, the overall superconducting properties of the annealed samples did not improve and, in fact, worsened. In particular, the superconducting transition temperature decreased, the upper critical field increased, and the pinning strength increased. In the STM study, the sample was annealed initially at 400 ∘C , measured, annealed at 1700 ∘C , and measured again. The STM revealed a ‘dirty’ superconducting gap with a significant spatial variation in tunneling conductance after annealing at 400 ∘C . The clean gap was recovered after annealing at 1700 ∘C . This is likely due to oxygen redistribution near the surface, which is always covered by oxide layers in as-grown crystals. Our results indicate that vacuum annealing at least up to 1400 ∘C , while removing a large percentage of hydrogen, introduces additional nanosized defects, likely hydride precipitates, that act as efficient pair-breaking and pinning centers. The dimensionless scattering rate is estimated to have increased from Γ=0.2 to about Γ=0.4 after annealing at 1400 ∘C . These results on single crystals differ drastically from those obtained in polycrystalline bulk niobium (i.e. cut from superconducting radio-frequency cavities), where annealing is known to have a significant positive effect that is attributed to the improvement of the crystalline structure masking the more subtle influence of the hydrides.

Advancing biohydrogen production through indirect photolysis: Insights from numerical simulation using the lattice boltzmann method

Hydrogen production through biochemical reactions is regarded as one of the most potential alternative technologies for producing hydrogen because of its efficacy, renewability, and environmental friendliness. Indirect biophotolysis is one of the most potential biohydrogen production technologies. In this study, a platform based on a coupled lattice Boltzmann method with cellular automata (LBM-CA) was developed to investigate the effects of different illumination intensities and carbon dioxide (CO2) concentrations on indirect photolysis in a bioreactor. The bioreactor was divided into two distinct parts. The first part as a photobioreactor had a transparent window at the top wall of the bioreactor that allowed solar illumination to enter the domain to generate glucose through the conversion of CO2 to carbohydrates (such as glucose) while the second was opaque where hydrogen was produced from carbohydrates by microorganisms. The results show that in the first part of the bioreactor, biofilm grew once CO2 was available. However, there is a lag in the biofilm growthand biohydrogen production between the first and the second part of the bioreactor because they depend on glucose production in the first part. The biofilm concentration increased as illumination increased, especially in the early stages, while the biofilm growth mainly occurred in the first part of the bioreactor. Increasing illumination could increase biofilm concentration by 92.4 % and reduce the lag time. It is also observed that increasing CO2 concentration changed the normalized biofilm concentration considerably, from − 40.9 % to 18.8 %. This can be attributed to increased nutrient availability for microorganism growth and glucose production in the first part of biophotolysis, resulting in greater concentrations of glucose as the main nutrient in the next part. Changing the inlet concentration leads to variations in the normalized hydrogen concentration in the range of − 72.9 % to 49.5 %.

Hydrogen embrittlement and strain rate sensitivity of electrodeposited copper: part I – the effect of hydrogen content

Slow strain rate tensile testing was conducted on electrodeposited copper, which is a candidate coating material for used nuclear fuel containers. Embrittlement was observed in electrodeposited copper containing 26.4 ± 1.0 ppm hydrogen, with a strain rate sensitivity such that the embrittlement was exacerbated at lower strain rate (5 × 10−7 s−1). Tensile tests conducted at 100° and 200 °C also intensified embrittlement when compared with tests conducted at room temperature. In contrast, electrodeposited copper containing only 5.25 ± 0.97 ppm hydrogen exhibited ductile behavior at all tested strain rates and temperatures. These findings suggest that a previously unexplained slow strain rate hydrogen embrittlement can operate in electrodeposited copper provided that the hydrogen concentration is sufficiently high. Further analyses revealed that the deformation of embrittled copper is achieved by the formation of internal microcracks which coalesce at the point of failure.

Evaluation of hydrogen embrittlement susceptibility of underwater laser direct metal deposited 316L stainless steel

Underwater laser direct metal deposition (UDMD) shows great application potential in underwater high-performance repair. The susceptibility of underwater repaired components to hydrogen embrittlement (HE) is not extensively researched yet. In this study, HE in 316L stainless steel repaired by UDMD is systematically investigated and compared with in-air direct metal deposited (DMD) 316L and conventionally manufactured (CM) 316L. The experimental results show that the high cooling rates involved in UDMD contribute to a “austenite-ferrite” solidification mode. The cellular structure with a high-density of dislocations increases the tensile strength of as-built UDMD 316L. Thermal desorption spectroscopy analysis reveals that the hydrogen concentrations are similar for 316L manufactured by three processing methods, suggesting that the complex microstructural features by UDMD and DMD do not provide additional H-trapping sites. SSRT results show that the HE susceptibility is in the sequence: CM 316L (30.7%) > UDMD 316L (15.1%) > DMD 316L (9.6%). Compared with CM 316L, the stable cellular structure and higher stability towards martensitic transformation of as-built 316L are beneficial for the HE resistance. In the hydrogen-charged UDMD 316L, the hydrogen-assisted dislocation movement and mechanical twinning formation enhance the localized plasticity and induce cracking. The micron-sized oxide particles and micro-pores further contribute to the fast decohesion of interfaces in the presence of hydrogen. Those combined effects lead to the reductions in tensile strength and elongation of the hydrogen-charged UDMD 316L.

Factors affecting conversion of methane-hydrogen mixtures into nanostructured carbon and hydrogen

At the catalytic decomposition of methane, along with hydrogen, it is possible to obtain carbon nanofibers. The addition of hydrogen to the initial reaction mixture makes it possible to increase significantly the efficiency of the overall process by minimizing the contribution of the catalyst deactivation process caused by coking. As found, the maximum yields of hydrogen and nanostructured carbon over the NiO–CuO/Al2O3 catalyst is achieved at an inlet hydrogen concentration of 13 vol%. The accumulated carbon is represented by well-structured carbon nanofibers, which are resistant to the gasification reaction. The original stacked structure is preserved after the treatment of these fibers in a hydrogen medium. Using numerical methods, the hydrogen productivity at 610 °C was found to be 49.3 mL/(mgcat·h) at an optimal value of the residence time of 5 × 10−3 s.

Long-term trends of pH, alkalinity, and hydrogen ion concentration in an upwelling-dominated coastal ecosystem: Ría de Vigo, NW Spain

The present study focuses on the Ría de Vigo (NW Spain), a coastal embayment influenced by the Canary Current Upwelling System, which is among the world’s significant Eastern Boundary Upwelling Ecosystems. The research assesses historical changes in the marine carbonate system by generating 25-year weekly time series at six stations . Assessing ocean acidification in the region is complex due to diverse factors influencing coastal carbon dynamics, making predictions more challenging. To capture the specific dynamics in Ría de Vigo, ensembles of Neural Networks were applied. These networks were trained with a data set obtained in several oceanographic cruises, in order to retrieve pH, hydrogen ion concentration and alkalinity, achieving a root mean square error of 0.0272 pH units, 0.588 nmol kg-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {kg}^{-1}$$\\end{document}, and 10.6 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu$$\\end{document}mol kg-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {kg}^{-1}$$\\end{document}, respectively. Subsequently, time series of the selected variables were generated, applying data of predictors measured at the aforementioned stations . An increase in normalized alkalinity was observed for all stations, except in the surface layer at the innermost location. A decrease in pH and an increase in hydrogen ion concentration were observed for all points, with trends that exceed reported rates of ocean acidification in the open ocean.

Electrosynthesis-Induced Pt Skin Effect in Mesoporous Ni-Rich Ni-Pt Thin Films for Hydrogen Evolution Reaction.

A Pt skin effect, i.e., an enrichment of Pt within the first 1-2 nm from the surface, is observed in as-prepared electrodeposited Ni-rich Ni-Pt thin films. This effect, revealed by Rutherford backscattering (RBS), is present for both dense thin films and mesoporous thin films synthesized by micelle-assisted electrodeposition from a chloride-based electrolyte. Due to the Pt skin effect, the Ni-rich thin films show excellent stability at the hydrogen evolution reaction (HER) in acidic media, during which a gradient in the Pt/Ni ratio is established along the thickness of the thin films, while the activity at the HER remains unaffected by this structural change. Further characterization by elastic recoil detection with He ions analysis shows that hydrogen profiles are similar to those of Pt: a surface hydrogen peak coincides with the Pt skin, and a gradient in hydrogen concentration is established during HER in acidic media, together with a considerable uptake in hydrogen. A comparative study shows that in alkaline media, hydrogen evolution has little to no effect on the structural properties of the thin films, even for much longer times of exposure. The mesoporous thin films, in addition to their higher efficiency at HER compared to dense thin films, also show lower internal stress, as determined by Rietveld refinement of grazing incidence X-ray diffraction patterns. The latter also reveal a fully single-phase and nanocrystalline structure for all thin films with varying Ni contents.

Eco-Friendly Polyurethane Foams Enriched with Waste from the Food and Energy Industries

In recent years, there has been considerable focus on ensuring that energy is used in the most efficient manner possible. This is due to the fact that globally, over 70% of energy is generated from fossil fuels. Consequently, the matter of designing and utilizing materials that will negate energy losses within the construction industry is of paramount importance. Simultaneously, the necessity for a sustainable approach to the design and production of materials is strongly emphasized. This paper presents an innovative approach to the use of a combination of mineral and plant-based fillers in polyurethane foam technology as a thermal insulation material with the potential to be used in construction to reduce energy consumption. Polyurethane composites containing fly ash from biomass combustion and the addition of rice, sunflower, and buckwheat husks as plant fillers were proposed. The structure of the obtained materials was studied, and the most important physical properties were analyzed. These included apparent density, dimensional stability, water absorption, and the effects of UV radiation and water influence on the carbon, hydrogen, nitrogen, and oxygen content. Moreover, the mechanical properties of the materials were investigated, including compressive strength and brittleness. Additionally, the foams were subjected to flammability tests using a cone calorimeter. Furthermore, additional parameters were determined, including the limiting oxygen index and the vertical and horizontal flammability tests. The results demonstrate the beneficial effects of combining mineral and vegetable fillers in polyurethane foam.

Advances in electrocatalytic dehydrogenation of ethylamine to acetonitrile.

The electrocatalytic dehydrogenation of ethylamine (EDH), owing to its high hydrogen content, holds broad prospects in electrochemical hydrogen (H2) production, H2 storage, and addressing energy issues, thus deserving wide attention. In this feature article, we first summarized the fundamentals of thermocatalytic and electrocatalytic EDH and reviewed the recent state-of-the-art advances in catalyst research, specifically platinum group metal (PGM) catalysts and non-PGM catalysts. We systematically discussed the potential applications of electrocatalytic EDH in energy storage and conversion. Finally, we provide our perspective on the key challenges and future developments in this field. We believe this feature article will offer helpful guidance for oriented design and optimization of stable and efficient catalysts for electrocatalytic EDH and related energy applications.

Microstructures, hydrogen concentrations, and seismic properties of a tectonically exhumed sliver of oceanic mantle lithosphere, Moa Island, Timor-Tanimbar outer-arc, eastern Indonesia

We characterize and quantify the microstructure, hydrogen concentrations, and seismic properties of a tectonically exhumed sliver of oceanic lithospheric mantle outcropping in the Moa Island (Leti archipelago, Timor-Tanimbar outer-arc). The 18 spinel peridotites (lherzolites and harzburgites) have coarse-porphyroclastic microstructures and olivine crystal-preferred orientations (CPO) with axial-[010] (also known as AG-type) or [100](010) (A-type) patterns, similar to those observed in peridotitic xenoliths from oceanic mantle lithosphere. These coarse-porphyroclastic microstructures are variably overprinted by growth of strain-free olivine neoblasts and crystallization of secondary pyroxenes. Recrystallized fractions vary from 6.9 up to 31.3%. The interstitial (cuspate) shapes and CPOs of clinopyroxene, uncorrelated with the olivine CPOs, indicate that refertilization by a reactive melt percolation post-dated deformation. Seismic properties are calculated based on the modal compositions and CPOs of all samples. Increase in the recrystallized olivine fraction decreased the seismic anisotropy, since static recrystallization produced some dispersion of the CPO, but did not change drastically the texture acquired during deformation. Mean seismic velocities (mean Vp = 7.9 km.s−1; mean Vs = 4.5 km.s−1) and anisotropy (mean maximum S wave polarization anisotropy = 4.5%), estimated by considering coherent orientation of the foliation and lineation of all samples, are within the range of typical values for the uppermost mantle. The nominally anhydrous minerals contain small amounts of hydrogen (olivine: 13–18 ppm H2O by weight; orthopyroxene: 58–175 wt ppm H2O and clinopyroxenes: 244–288 wt ppm H2O). A bulk water content of 50 wt ppm H2O is estimated based on NAMs for the Moa peridotites, in agreement with previous estimates for the oceanic mantle lithosphere based on peridotitic xenoliths. This is the first direct measurement of the hydrogen concentrations in peridotites from an oceanic mantle lithosphere which experienced melt extraction.

Design of a pilot-scale microwave freeze dryer for in situ neutron imaging.

The gentle yet cost-effective drying of sensitive products in the food and pharmaceutical industries is becoming increasingly important. To maintain sensitive ingredients, color, structure, and viability of micro-organisms, often freeze-drying is the only possible way to preserve the product. As many products come in as bulk material, they are dried on heated shelves resulting in poor heat and mass transport through the bed. Resulting in a very time and cost intensive process. Therefore, efforts are being made to improve the mass and heat transport of the process. The outer mass transport through the bulk can be improved by continuous mixing of the pellets, facilitating the removal of water vapor from the condenser. In addition, the issue of limited heat transport can be addressed by using volumetric energy input from microwaves. This process is called dynamic microwave freeze-drying. As dynamic microwave freeze-drying is a combined drying and mixing process, with particle properties continuously changing during drying, it is necessary to gain a more detailed insight into the process. For this purpose, a drier is designed that is capable of in situ neutron imaging, a method sensitive to a material's hydrogen content. This paper presents the design of a pilot-scale microwave freeze dryer for in situ neutron imaging and shows the first images taken during the dynamic microwave freeze-drying of bulk particles at the Center for Energy Research, Budapest Neutron Center in Budapest, Hungary.

Experimental investigation and CFD study of direct reduction of iron ore in the conical fluidized bed

The reduction behavior of iron ore is the fundamental process in ferrous metallurgy. Considering the gas–solid interface-structure relationship, heterogeneous transfer-reaction behavior, and multiple reaction kinetics, this work provides an effective analytical tool to investigate the fluidized reduction of iron ore. The conical fluidized bed is numerically examined to be capable of preventing de-fluidization induced by the sticking behavior, due to the steady circulation of flow pattern and full fluidization of coarse agglomerates. Compared with the hydrogen concentration, the gas velocity shows a stronger influence on the agglomerate reduction rate for the more efficient gas–solid contact. For the simulated transitions of Fe2O3 → Fe3O4 → Fe(1-x)O → Fe are assumed to overlap each other, there exist discrepancies between computed and theoretical reduction degrees. The experimental and numerical findings can be used to develop a methodology for optimizing the operational complexity and economic benefits of the fluidized reduction of iron ore.

The synergistic effect of Cl doping and Bi coupling to promote the carrier separation of BiOBr for efficient photocatalytic nitrogen reduction

Photocatalytic nitrogen reduction reaction (NRR) is a sustainable process for ammonia synthesis under mild conditions. However, photocatalytic NRR activity and are generally limited by inefficient carrier separation and transfer. Therefore, parallel engineering of bulk phase doping and surface coupling is critical to achieving the goal of efficient NRR. In this study, Cl doped BiOBr nanosheet assemblies (BiOBr/Cl) were constructed in delicately designed deep eutectic solvents (DESs), combined with ionothermal methods at low temperatures and Bi3+ exsolution reduction strategy at high temperatures. The unique liquid state and reducibility of DESs induce the reduction of Bi3+ and the in situ coupling of Bi quantum dots at the surface of BiOBr/Cl nanosheets along with the construction of Bi-BiOBr/Cl nanosheet assemblies. The experimental results show that Cl doping could reduce the exciton dissociation energy and promote its dissociation to free carriers. Bi quantum dots could form tightly coupled Schottky junction with BiOBr/Cl enabling the efficient and unidirectional transmission of photogenerated electrons from BiOBr/Cl to metal Bi. The formed electron deficient region at Schottky interface promotes the adsorption and activation of N2. The hierarchical structure of Bi-BiOBr/Cl nanosheet assembly benefits to providing more N2 adsorption active sites. The DFT calculation shows that the accumulation of high concentration of active hydrogen in Bi-BiOBr/Cl leads to a significant decrease of energy barrier of the first step hydrogenation of N2. Bi-BiOBr/Clis more inclined to adsorb nitrogen for NRR in comparison with H* for hydrogen production. The synergistic effect of Cl doping and Bi coupling result in a high NRR activity of Bi-BiOBr/Cl photocatalyst of 6.67 mmol·g−1·h−1, which was 11.3 times higher than that of initial BiOBr. This study provides a promising strategy for designing highly active NRR photocatalysts with high efficiency carrier dissociation and transport.

Influence of dissolved hydrogen and IG Cr carbide on the oxidation behavior of Alloy 600 in hydrogenated primary water

The internal oxidation (IO) and preferential intergranular oxidation (PIO) behavior of Alloy 600 depending on the dissolved hydrogen (DH) content and the IG Cr carbide in hydrogenated primary water were characterized in detail using analytical electron microscopy techniques. The oxidation layer was unstable when the DH concentration was such that Ni was in the vicinity of Ni/NiO equilibrium and it could easily be peeled off. Hence, the grain boundaries of the bare metal were attacked. PIO occurred and Cr-rich oxide identified as Cr2O3 was formed at the oxidized grain boundary. NiO emerged when the DH concentration was such that Ni was in an oxidizing state, whereas Ni enrichment occurred inside the oxidized grain boundary when the DH concentration was such that Ni was in a reducing state with respective to Ni/NiO equilibrium. The IG Cr carbide strongly affected the PIO behavior by means of the consumption of oxygen penetrating into the grain boundary. The depth of the IO layer decreased as the DH concentration increased. The different oxidation behaviors depending on the DH content and IG Cr carbide are believed to affect the PWSCC resistance of Alloy 600 significantly.

Cattle manure thermochemical conversion to hydrogen-rich syngas, through pyrolysis and gasification

The fundamental significance of using cattle manure as a case study is the risk of continuing pollution, caused by its poor management in connection to the increasing demand for animal-derived food. Pyrolysis and gasification, effective solutions with real valorization potential, are the proposed techniques of converting this type of waste into valuable products. After a complete initial characterization, cattle manure is converted into hydrogen-rich syngas, using a modular hybrid fixed-bed reactor, at a generous thermal range, 700 °C to 875 °C, under different process agents, without the use of steam or the addition of catalysts. In comparison to gasification, the quantification of syngas demonstrates higher yields in pyrolysis processes, but with a lower energy potential. The content of the syngas in hydrogen, ⁓ 25 vol% and hydrocarbons, ⁓ 25 vol%, emphasized by an energetic value of ⁓ 17 MJ/m3, holistically places the gasification process in a slight advantage in relation to pyrolysis, exceeding the values presented by other studies on similar matrices and technical conditions. The forecast investigation of syngas composition through polynomial functions shows a significant drop in hydrogen and hydrocarbon concentrations after the 80-min sampling period.

Recent advances in measuring the effects of diet on gastrointestinal physiology: Sniffing luminal gases and fecal volatile organic compounds.

Despite the huge pool of ideas on how diet can be manipulated to ameliorate or prevent illnesses, our understanding of how specific changes in diet influence the gastrointestinal tract is limited. This review aims to describe two innovative investigative techniques that are helping lift the veil of mystery about the workings of the gut. First, the gas-sensing capsule is a telemetric swallowable device that provides unique information on gastric physiology, small intestinal microbial activity, and fermentative patterns in the colon. Its ability to accurately measure regional and whole-gut transit times in ambulant humans has been confirmed. Luminal concentrations of hydrogen and carbon dioxide are measured by sampling through the gastrointestinal tract, and such application has enabled mapping of the relative amounts of fermentation of carbohydrates in proximal-versus-distal colon after manipulation of the types and amounts of dietary fiber. Second, changes in the smell of feces, via analysis of volatile organic compounds, occur in response to the diet, and by the presence and therapy of irritable bowel syndrome and inflammatory bowel disease. Such information is likely to aid our understanding of what dietary change can do to the colonic luminal microenvironment, and may value-add to diagnosis and therapeutic design. In conclusion, such methodologies enable a more complete physiological profile of the gastrointestinal tract to be created. Systematic description in various cohorts and effects of dietary interventions, particularly when co-ordinated with the analysis of microbiome, are needed.

Evaluation of the properties of bio-asphalt derived from waste cooking oil and low-density polyethylene through the pyrolysis process

The aim of this study is to prepare a bio-asphalt for flexible pavement construction using a fixed-bed pyrolysis reactor. This method involves incorporating waste cooking oil (WCO) and low-density polyethylene (LDPE) as feedstock materials. Through this study, an attempt has been made to make use of waste materials and promote the use of environmentally friendly binders in sustainable road construction. The pyrolysis experiment was conducted at different temperatures, varying from 250oC to 500 oC for different blends of waste cooking oil (WCO) and low-density polyethylene (LDPE), i.e., 1:0, 3:1, 1:1, 1:3, and 0:1, respectively. At a temperature of 350oC, the pyrolysis process is more effective for converting various blends of waste cooking oil (WCO) and low-density polyethylene (LDPE) into bio-asphalt. The maximum bio-asphalt yield of 82wt% was reported for the 1:3 blend at a temperature of 350oC. The elemental analysis of an equal mass of waste cooking oil (WCO) and low-density polyethylene (LDPE) reported a carbon content of 83.93wt%, a hydrogen content of 13.29wt%, and a lower oxygen content of 2.55wt%. The Gas Chromatography Mass Spectrography (GC-MS) analysis indicated the presence of chemical compounds such as pentadecane, heptadecane, dodecane, cyclopentylpropyl, and hexacosene in the 1:1 blend. The thermogravimetric and derivative thermogravimetric analyses indicate that the 1:1 blend and 1:3 blend can withstand temperatures around 473oC and 475oC, respectively. The Fourier transform infrared spectroscopy (FT-IR) analysis showed the presence of alkane, alkene, ester, and other aromatic compounds. Based on this present study, it has been noted that the chemical composition of a 1:1 blend of waste cooking oil (WCO) and low-density polyethylene (LDPE)-based bio-asphalt contains similar chemical compositions as asphalt binder, and it can be used as a modifier for conventional asphalt binder.

Impact of Relative Humidity on the Formation of Low-Frictional Interface and its Continuity in Tribological Systems with Hydrogenated Carbon Nitride Coatings

The impact of relative humidity on the formation of low-frictional interface in hydrogenated carbon nitride (CNx:H) coatings sliding against Si3N4 balls and the formation continuity was elucidated through friction tests conducted in both air and nitrogen atmospheres with controlled relative humidity levels. In air atmosphere, a carbonaceous tribolayer with a transformed structure from the initial CNx:H was formed on Si3N4 at less than the critical humidity that existed in 1.0–3.0% RH, resulting in low friction (μ < 0.05) and a low specific wear rate of the balls (< 2 × 10–9 mm3/N·m). In contrast, this tribolayer failed to form above 3.0% RH. In nitrogen atmosphere, within the 0.25–1.0% RH range, the tribolayer continued to form concurrently with wear progression, maintaining low friction for over 50,000 cycles. However, in less than this humidity range, the lifetime of low friction was limited owing to the tribolayer’s structural alteration. Thus, relative humidity influences not only the formation of the low-frictional interface but also the formation continuity. On the CNx:H friction surface, hydrogen, hydroxyl, and oxygen groups from environmental water and oxygen molecules continued to chemisorb owing to tribochemical reactions on the uppermost few nanometers during continuous low friction in a nitrogen atmosphere, while hydrogen content of CNx:H desorbed. This study experimentally confirmed the critical role of controlling relative humidity in tribological systems using CNx:H coatings to achieve low friction and improve its durability of low friction through the continuous formation of the low-frictional interface.

Study on the flow and heat transfer characteristics of gaseous hydrogen in heat exchange tubes coupled with ortho-para hydrogen conversion

Hydrogen as a clean energy to deal with carbon emissions has been favored by many scholars, while the problems of low efficiency and high energy consumption in the process of liquefaction storage and transportation have become one of the important factors restricting the development of it. The combination of heat exchanger and ortho-para (O–P) hydrogen converter has attracted considerable attention as a high efficiency and low energy consumption technology. In this paper, based on the catalyst-filled spiral wound heat exchanger (CSWHE) and coupled with ortho-para hydrogen conversion, the flow and heat transfer characteristics of gaseous hydrogen are studied. Firstly, low-temperature O–P hydrogen catalytic conversion experiments and flow characteristics experiments were carried out by filling catalyst in the heat exchange tube. and an equation for calculating pressure drop in the section filled catalyst was proposed. Secondly, a new numerical model was established validated by the experiments. The influence of catalyst on heat transfer and the effects of velocity on the heat transfer performance and O–P hydrogen conversion efficiency were studied by numerical simulation. Finally, this paper analyzed the significant factor affecting the para hydrogen content at outlet: reaction time. And an equation for calculating para hydrogen content at outlet with reaction time was proposed. This study is expected to provide a reference for the design of CSWHE.