Surface Oxidation Research Articles

Low-cycle fatigue behavior of coated and uncoated single crystal Ni-based superalloy at various temperatures

Within this work, the effect of different oxidation-resistant coatings on the low-cycle fatigue (LCF) behavior and damage mechanisms of third-generation single crystal (SC) Ni-based superalloy was investigated. Stress-controlled LCF tests of bare alloy, MCrAlY-coated and PtAl-coated thin-walled specimens were carried out at 760 °C, 850 °C and 980 °C. A unique clamping system was meticulously designed to overcome the clamping challenge in high-temperature furnaces. The cracking behaviors and failure modes were determined by advanced microstructure characterization. The results show that the coatings are detrimental to the LCF lifetime of thin-walled specimens, especially at low-medium temperatures of 760 °C and 850 °C. For bare alloy, the tip cracks nucleate from the surface oxide layer, whereas cracks in the coating-substrate system nucleate prematurely from the coating surface and propagate to the substrate. The oxygen diffusion and the frontward propagation of cracks are synergistically enhanced in the SC substrate, resulting in oxidation-assisted crack propagation and ultimate failure. Finally, A fatigue life prediction model is proposed by introducing coating-induced crack initiation and oxidation effects, where the predictive results fit well with experimental results. This study provides a comprehensive insight into the damage mechanisms and coating-induced LCF life degradation of the coating-substrate system.

Synthesis and properties of quasi-one-dimensional BiSBr crystals via the Bridgman-Stockbarger technique

This investigation details the synthesis and comprehensive characterization of semiconducting bismuth sulfobromide (BiSBr) crystals, emphasizing their structural and optoelectronic properties. Using the Bridgman-Stockbarger technique, we synthesized large, high-quality BiSBr crystals, which were systematically examined through techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. These methods confirmed the crystals’ quasi-one-dimensional structure and their exceptional stability, demonstrating an absence of surface oxidation, which is a significant advantage for optoelectronic applications. The study establishes a correlation between the crystals’ unique structural characteristics and their enhanced optoelectronic properties, particularly regarding light absorption and thermal conductivity, thereby underscoring their potential in sustainable energy technologies. This work not only advances our understanding of BiSBr as a promising material for optoelectronic devices, but also paves the way for future research into its practical applications in energy conversion and storage systems.

Corrosion resistance of magnesium alloy surfaces substantially upgraded by gradient energy irradiation of femtosecond lasers

The poor corrosion resistance of magnesium (Mg) alloys is known to constitute a major obstacle to their practical applications. In this work we proposed an approach of femtosecond laser multi-grid-scanning with the gradual decreasing energy fluence, to modulate the surface oxide properties for the anti-corrosion performance enhancement. This kind of laser processing can significantly increase the oxide passivation layer thickness by more than 100 times compared with the bare sample, and improve the oxygen content on the material surface to as high as 55.87%. Simultaneously, the available size of MgO nanograins is further refined and has more spatially uniform distribution. Moreover, the massive production of micro/nano-structures by the femtosecond laser irradiation tends to promote the surface into the superhydrophobic with a contact angle of CA=162 ± 2 ° and a slide angle of SA=1.5 ± 0.5 °. As a result, the obtained optimal values for the corrosion current density and the annual corrosion rate are reduced to Icorr = 0.5 μA/cm2 and CR = 7×10-3mm/y, respectively, more than 2 orders of magnitude lower than the bare sample. Such a method provides an efficient strategy to enhance the corrosion resistance of metal surfaces for future applications.

Temperature dependence of the friction and wear behavior of pure tungsten

In this work, the friction and wear characteristics of rolled pure tungsten were investigated by using atomic force microscope (AFM) and field emission scanning electron microscope (SEM) with electron backscatter diffraction (EBSD) characterization techniques. A ductile to brittle transition (DBT) related frictional wear behaviors have been discovered. The results indicated that the coefficient of friction maintains an almost constant value of 0.45 at low temperatures (≤ 400 °C), whereas it consistently decreases at 600 °C due to the generation of a surface oxide. The wear rate varies with temperatures and reaches a maximum at 200 °C due to the transition of the tungsten matrix from brittleness to pseudoplasticity, which leads to severe adhesive wear and large mass loss. In addition, the evolution of sub-grains underneath the friction layer and Vickers microhardness were evaluated as well. This work provides insight into understanding the relationship between temperatures, microstructure and the frictional properties of tungsten materials, and thus provides guidance for improving frictional wear behaviors in tungsten materials.

Towards detailed combustor wall kinetics: An experimental and kinetic modeling study of hydrogen oxidation on Inconel

Gas-phase hydrogen combustion is ubiquitous in industrial processes, and the associated surface kinetics on heat-resistant alloys plays a crucial role in designing efficient low-carbon technologies. We conducted new temperature programmed reduction experiments to determine the reducibility of materials following an oxidation cycle. These experiments were modeled using a thermoconsistent multi-site microkinetic model for H2 heterogeneous oxidation on Inconels, which was validated against literature experiments. This competitive adsorption model considers iron bulk content, hydrogen spillover and subsurface oxygen migration on hydrogen surface oxidation kinetics. New X-ray diffraction experiments confirmed the postulated crystallographic structures in the Inconel samples, suggesting their presence on the surface scale. The phenomenological model was coupled with several state-of-the-art gas-phase oxidation mechanisms to assess gas/surface reactions interaction as a function of material and temperature. The results reveal a complex interaction in which surface removes H radicals from the gas-phase, while the Bradford (H2+OH) reaction converts OH into H2O, promoting water adsorption on Inconel. This interaction was found to give rise to gas-phase thermokinetic oscillations. The model predicts a non-monotonous effect of reactor area-to-volume ratio on reactivity and emphasizes the impact of Inconel composition on product selectivity. Overall, the multi-site model provides new insight into the contrasting reactivities among active sites, bridging the gap between material science and heterogeneous combustion modeling.

Surface anchoring requirements for vanadia clusters on titanium oxide surfaces and their impact on activity for oxidative dehydrogenation of ethanol

Titanium oxide site requirements for the anchoring of catalytically active forms of dispersed vanadia species are investigated. Using a series of oxygen-modified titanium nitride materials, we systematically modify the available vanadia-anchoring moieties on the titanium-bearing support surface. This strategy in turn results in a very narrow size distribution of well-dispersed vanadia clusters anchored on the support. This synthesis technique ensures that only highly dispersed vanadia is present on the catalyst surface even at nominal monolayer coverages. A deeper insight into the catalytic behavior for ethanol partial oxidation of the active vanadia species is obtained by comparing intrinsic kinetic and thermodynamic parameters of kinetically relevant reaction steps (heat of ethanol adsorption, hydrogen abstraction activation energy, and the energetics of catalyst reoxidation). It is found that these parameters are dependent on the relative amount of oxygen in the titanium-bearing support and the resulting distribution of vanadia species, which validates the premise of a potential participation of lattice oxygen atoms of the titania support into the catalytic activity of active vanadia species.

Stable production of hydrogen peroxide over zinc oxide @ zeolitic imidazolate Framework-8 composite catalysts

A promising method of producing hydrogen peroxide (H2O2) is the electrochemical two-electron water oxidation reaction (2e− WOR). In this process, it is important to design electrocatalysts that are both earth abundant and environmentally friendly, as well as offering high stability and production rates. The research of WOR catalysts, such as the extensively used transition metal oxides, is mainly focused on the modification of transition metal elements. Few studies pay attention to the protective heterostructure of metal oxides. Here, we demonstrate for the first time an organometallic skeleton protection strategy to develop highly stable WOR catalysts for H2O2 generation. Unlike the pure ZnO and zeolite imidazole framework-8 (ZIF-8) catalysts, ZnO@ZIF-8 enabled the production of hydrogen peroxide at high voltages. The experimental results demonstrate that the ZnO@ZIF-8 catalyst stably generates H2O2 even under a high voltage of 3.0 V vs. RHE, with a yield reaching 2845.819 μmol/min g−1. ZnO@ZIF-8 shows a relatively low overpotential, with a current density of 10 mA cm−2 and an overpotential of 110 mV. The ZnO@ZIF-8 catalyst’s maximal FE value was 4.72 %. Moreover, the ZnO@ZIF-8 catalyst exhibits remarkable durability even after an extended 60-hour stability test. Operando Raman and theoretic calculation analyses reveal that the metal–organic skeleton being encapsulated on the metal oxide surface synergizes with each other, not only expanding the electrochemical surface area, but also adjusting the catalyst metal sites’ adsorption capacity. A novel approach to the modification of 2e− WOR metal oxide catalyst is presented in this work.

Experimental and statistical physics illumination of Pb(II) adsorption on magnetic chitosan-graphene oxide surface

Adsorption stands for a promising technique for heavy metal remediation. Herein, a high efficiency adsorbent based on magnetic chitosan-graphene oxide (MCGO) was prepared via a simple co-precipitation procedure. Afterwards, adsorption behaviour of Pb(Ⅱ) on MCGO surface was illuminated via batch adsorption experiment and statistical physics calculation. Result presents, MCGO reaches adsorption percent and adsorption quantity 93.06 % and 372.24 mg·g−1 for Pb(Ⅱ) in 44 min, showcasing favorable remediation efficiency. Statistical physics calculation proposes multi-ionic adsorption mechanism. With the increase of temperature, adsorption site density is increased to yield ameliorated adsorption capacity. Moreover, calculation result of the thermodynamic functions designates exothermic, randomness increasing, spontaneous and energy releasing feature. Kinetic fitting based on various models assigns chemical interaction as the rate controlling step. Finally, adsorption mechanism was clarified in atomic level via spectroscopic inspection. Specifically, C=O, C–O, O–H, N+ and –C(=O)NH– contribute to Pb(Ⅱ) adsorption via donating lone pair electrons. This work provides both experimental and statistical physics insights for understanding the adsorption behaviour of typical heavy metal pollutants onto the surface of bio adsorbent like magnetic chitosan-graphene oxide.

THE INFLUENCE OF ABUTMENT SURFACE TREATMENT ON PULL-OFF BOND STRENGTH BETWEEN (5)YTTRIA STABILIZED ZIRCONIA CROWN AND TITANIUM IMPLANT ABUTMENT

ABSTRACT Aim: The objective of this research was to evaluate the effect of mechanical method and energetic method of surface treatments for Ti-abutment base (Ti-Base, Dentium/Korea) on the pull-off bond strength with (5)Y-TZP crown. Materials and Methods: : Forty titanium implant abutments were used in this study and randomly assigned to four groups (n = 10 for each group) according surface treatment methods of titanium abutment: group (1) act as control without surface treatment for Ti-abutment, group (2) bur surface treatment of Ti-abutment, group (3) sandblast (50-µm aluminum oxide) surface treatment for Ti-abutment, group (4) plasma surface treatment for Ti-abutment. Then, forty implant analogs were placed in the center of acrylic mold. After that abutment was tightened on the each analog with (35 N/cm) torque . Forty (5)Y-TZP crowns fabricated by CAD/CAM system that had special design with occlusal O-hole cemented to all abutments using Allcem dual-cure resin cement. All specimens were then subjected to thermos-cycling with (5000) cycles. With a universal testing machine record pull-off bond strength for all samples, Collected data were analyzed using a one-way analysis of variance at a significance level of (p < 0.01) . Results:, The bur treated abutment (group 2) group showed the highest bond strength values, followed by sandblast treated abutment (group 3) and plasma treated abutment (group 4). Control group was the lowest value of tensile strength. Conclusion: Surface treatments of Ti-abutment had observed effect on pull-off (tensile bond strength) between Ti-abutment and (5)Y-TZP crown Bur and sandblast cause roughness of surface and increase bond strength , plasma cause reactive surface for increasing tensile bond strength.

Oxidizing methanol at cubic-hexagonal junction of NiO-ZnO at low onset potential

A bimetallic, low-cost electrocatalyst consisting of non-noble nickel (Ni) and zinc (Zn) metal was synthesized for the effective oxidation of methanol (CH3OH). The formation of cubic NiO (nickel oxide) and hexagonal ZnO (zinc oxide) was confirmed by various spectrophotometric analyses. NiO-ZnO modified with -COOH functionalized MWCNT, NiO-ZnO-f-MWCNT exhibited significant methanol oxidation reaction (MOR) activity without any substantial oxygen evolution reaction (OER). At a lower onset potential value of 1.33 V versus RHE (reversible hydrogen electrode), the catalyst NiO-ZnO-f-MWCNT demonstrated a high current density of 3.88 × 103 Am-2 in 1 M KOH and 1 M CH3OH. The catalyst NiO-ZnO-f-MWCNT, with the lowest Tafel slope value compared to the other synthesized catalysts, was found to be stable without significantly losing current density, for about 500 cycles and 25000s. Density functional theory (DFT) calculation unveiled that all the steps involved during the interaction of CH3OH and the catalyst surface for oxidation of CH3OH were exergonic indicating a thermodynamically feasible and favourable process of MOR. The electrocatalytic activity was found to be dependent on the concentration of both Ni and Zn. An increase in Ni concentration hampered the MOR by favouring the OER.

Determining the influence of relative humidity on the working parameters of a gas sensor based on zinc oxide

This paper investigates the dependence of operating parameters of a gas sensor based on zinc oxide obtained by the method of direct current magnetron sputtering. The production of gas sensor films was carried out using a VUP-5M vacuum unit with an original material-saving magnetron. The study of the dependence of the working parameters of the gas sensor was carried out under standard conditions. It was found that with increasing humidity, the electrical resistance of the gas sensor decreases and, accordingly, the sensitivity to the target gas decreases. A significant reaction of the gas sensor to an increase in humidity was observed in the range of 65–80 % relative humidity. The mechanism of influence of relative humidity on the sensitivity of a gas sensor based on ZnO was investigated. The change in resistance of the gas sensor is caused by trapped electrons on adsorbed oxygen molecules on the surface of the sensitive layer. The capture of electrons from the conduction zone leads to bending of the conduction zone and an increase in the space charge zone, respectively, to a change in the resistance of the sensitive layer of the gas sensor. In the atmosphere, when O2 molecules are adsorbed on the ZnO surface, they remove an electron from the conduction band. The reaction of oxygen adsorbed on the ZnO surface with reducing gases and the replacement of adsorbed oxygen with other molecules changes the bending of the conduction band and reduces the area of space charge. Adsorption of water on the surface of zinc oxide occurs according to the dissociation mechanism, which consists in the adsorption of steam molecules or hydroxyl groups with the subsequent displacement of previously adsorbed oxygen and free electrons and, accordingly, leads to a decrease in the sensitivity of the gas sensor. In addition, the adsorption of water vapor (H2O) molecules leads to less chemisorption of oxygen species on the ZnO surface due to the reduction of the surface area, which is responsible for the sensor response. Approaches to reduce the influence of relative humidity on the sensitivity of a gas sensor based on zinc oxide have been proposed

Advanced supercapacitor electrodes: Synthesis and electrochemical characterization of graphene oxide-bismuth metal-organic framework composites for superior performance

The primary requirements for a viable supercapacitor electrode material are increased energy density, high specific capacitance, and excellent cycle stability. The desired outcome may be attained by combining diverse active materials. In this research, two Bi-MOFs with 1,4-benzenetdicarboxylic (H2BDC) and 1,3,5-benzenetricarboxylic (H3BTC) organic linkers were synthesized by facile solvothermal method and bonded on the surface of graphene oxide to produce FGO-Bi(BTC) and FGO-Bi(BDC) composites. The electrochemical characteristics of the two electroactive compounds were evaluated by GCD, CV, and EIS tests in a three-electrode setup. Comparative electrochemical analyses demonstrated that the composites exhibit remarkable performance with reduced charge transfer resistance. In the three-electrode configuration, FGO-Bi(BDC) and FGO-Bi(BTC) exhibited specific capacitances of 559 and 422 F g-1 at 1 A g-1, respectively. After conducting 10,000 cycles of charge and discharge at 8 A g-1, the FGO-Bi(BDC) and FGO-Bi(BTC) electrodes exhibited impressive retention rates of 97.6% and 95.64% for their initial specific capacitance (Cs). Notably, the three-electrode system's results indicated superior electrochemical performance of the FGO-Bi(BDC) electrode over the FGO-Bi(BTC) electrode. This superiority is attributed to the FGO-Bi(BDC)'s larger specific surface area (SSA) and reduced oxygen concentration. For a more practical assessment, the FGO-Bi(BDC) composite was selected for evaluation in the two-electrode system. The FGO-Bi(BDC)//FGO-Bi(BDC) two-electrode system demonstrated a cyclic stability of 94.2% over 10,000 cycles, attaining a substantial Cs of 295 F g-1 at 1 A g-1. Moreover, it accomplished a power density of 750 W kg-1 and an energy density of 34.61 Wh kg-1, emphasizing the exceptional electrochemical attributes that position the FGO-Bi(BDC) composite as a promising electrode material for supercapacitors.

Copper foil microforming through underwater laser oblique impact

Laser-induced cavitation impact forming is a high-speed forming process that employs a high-energy laser to produce cavitation in a liquid and act on the workpiece. When the laser is irradiated vertically to the workpiece surface through the guide hole, oxidation occurs on the produced workpiece's surface, affecting the surface quality. Laser-induced cavitation oblique impact workpiece formation is proposed in this paper. The surface quality of the workpiece created at various angles is investigated by adjusting the angle between the laser and the guide hole. A finite element model (FEM) was employed to simulate the temperature change and collapse speed of laser-induced cavitation, and a hydrophone was utilized to measure the impact pressure of laser-induced cavitation under various guide holes. The variations in forming depth and surface quality of the workpiece caused by laser-induced cavitation oblique impact were investigated experimentally. The experimental results show that as the angle between the laser and the guide hole increases from 0° to 90°, the width of the oxidized area on the surface of the formed micro-groove decreases from 513 μm to 0 μm, the forming depth of the micro-groove decreases from 80 μm to 20 μm, and the surface roughness of formed parts decreases from 2.93 μm to 0.56 μm. The oxidation of the formed workpiece surface during the oblique laser impact is primarily caused by the laser irradiation, according to the analysis of the surface oxidation mechanism of the formed micro-grooves. When the angle between the laser and the guide hole is 60°, all of the heat emitted by the laser is focused to the guide hole's inner surface. The angle between the laser and the pilot hole was set to 60° in the experiment, and the micro-groove structure was generated by three impacts, with the thickness distribution of the formed groove investigated. The results demonstrate that the largest thinning of the micro-groove cross-section occurs at the mold's entry and the bottom of the micro-groove, with thinning rates of 20 % and 15 %, respectively.

Impact of aging of primary and secondary polystyrene nanoplastics on the transmission of antibiotic resistance genes in anaerobic digestion

Sewage sludge is a significant reservoir of nano/microplastics (NPs/MPs) and antibiotic resistance genes (ARGs). Research has revealed that NPs/MPs may exert an inhibitory effect on anaerobic digestion (AD) of sludge. Moreover, NPs/MPs can influence microbial community diversity and composition, potentially increasing ARGs dissemination. The morphological changes to NPs/MPs surface due to aging contribute to modifying hydrophobic properties. To date, there is limited comprehension regarding how various surface properties of NPs influence ARGs dissemination during AD. This study investigated the impact of primary aged/non-aged and secondary aged/non-aged polystyrene nanoplastics (PSNPs) on ARGs and mobile genetic elements (MGEs) propagation during AD. The findings indicated that the UV-aging process resulted in surface oxidation and distinct morphological characteristics in both primary and secondary PSNPs, while the surface oxidation effect was more pronounced in the secondary aged PSNPs. High concentrations (150 μg/L) of primary and secondary PSNPs inhibited methane production, with secondary PSNPs causing greater inhibition by 16 to 20 % compared to control. In contrast, low concentration (25 μg/L) had negligible or slightly positive effects on methane production. PSNPs at 150 μg/L reduced total VFA concentration, indicating an inhibitory effect on the fermentation step in the AD process. Primary and secondary PSNPs exhibited changes in EPS characteristics. ARGs abundance was enriched in reactors amended with PSNPs, with the highest abundance of 8.54 × 105 copies/g sludge observed in the secondary aged PSNPs (150 μg/L) reactor. Reactors exposed to aged PSNPs exhibited a relatively higher abundance of ARGs compared to reactors exposed to non-aged PSNPs. Exposure to PSNPs increased the microbial community diversity within the digesters and triggered the enrichment of Comamonadaceae and Syntrophaceae, belonging to Proteobacteria phylum. On the other hand, archaeal communities tended to shift towards hydrogenotrophic methanogens in PSNPs reactors. The correlation analysis showed that Comamonadaceae were positively correlated with the majority of ARGs and intl1. A positive correlation was observed between MGEs and most ARGs, suggesting that the increased proliferation of ARGs under PSNPs exposure may be linked to the abundance of MGEs, which in turn promotes the growth of hosts carrying ARGs. These findings suggest that aged and non-aged NPs could substantially impact the spread of ARGs and MGEs, which also led to notable alterations in the composition of the microbial community. Overall, this study provides valuable insights into the multifaceted impacts of PSNPs with various characteristics on AD processes, microbial communities, and ARGs proliferation, highlighting the urgent need for comprehensive assessments of NPs pollutants in the environment.

Size- and Shape-Dependent Interactions of Lipid-Coated Silver Nanoparticles: An Improved Mechanistic Understanding through Model Cell Membranes and In Vivo Toxicity.

The widespread use of silver nanoparticles (AgNPs) in various applications and industries has brought to light the need for understanding the complex relationship between the physicochemical properties (shape, size, charge, and surface chemistry) of AgNPs that affect their ability to enter cells and cause toxicity. To evaluate their toxicological outcomes, this study systematically analyzed a series of homogeneous hybrid lipid-coated AgNPs spanning sizes from 5 to 100 nm with diverse shapes (spheres, triangles, and cubes). The hybrid lipid membrane comprises hydrogenated phosphatidylcholine (HPC), sodium oleate (SOA), and hexanethiol (HT), which shield the AgNP surface from surface oxidation and toxic Ag+ ion release to minimize its contribution to toxicity. To reduce any significant effects by surface chemistry, the HPC, SOA, and HT membrane composition ratio was kept constant, and the AgNPs were assessed using embryonic zebrafish (Danio rerio). While a direct comparison cannot be drawn due to the lack of complementary sizes below 40 nm for triangular plates and cubes due to synthetic challenges, significant mortality was observed for spherical AgNPs (AgNSs) of 5, 20, 40, and 60 nm at 120 h postfertilization at concentrations ≥6 mg Ag/L. In contrast, the 10, 80, and 100 nm AgNSs, 40, 70, and 100 nm triangular plate AgNPs (AgNPLs), and 55, 75, and 100 nm cubic AgNPs (AgNCs) showed no significant mortality at 5 days postfertilization following exposure to AgNPs at concentrations up to 12 mg Ag/L. With constant surface chemistry on the AgNPs, size is the dominant factor driving toxicological responses, with smaller nanoparticles (5 to 60 nm) being the most toxic. Larger AgNSs, AgNCs, and AgNPLs from 75 to 100 nm do not show any evidence of toxicity. However, when closely examining sizes between 40 and 60 nm for AgNSs, AgNCs, and AgNPLs, there is evidence that discriminates shape as a driver of toxicity since sublethal responses generally were observed to follow a pattern, suggesting toxicity is most significant for AgNSs followed by AgNPLs and then AgNCs, which is the least toxic. Sum frequency generation vibrational spectroscopy showed that irrespective of size or shape, all hybrid lipid-coated AgNPs interact with membrane surfaces and "snorkel" between phases into the lipid monolayer with minimal energetic cost. These findings decisively demonstrate that not only smaller AgNPs but also the shape of the AgNPs influences their biological compatibility.

Oxide coated nickel powder as support for platinum(0) nanoparticles: Magnetically separable catalysts for hydrogen generation from the hydrolysis of ammonia borane

We report the development of a novel method for the preparation of magnetically separable platinum nanoparticles. Magnetic nickel nanopowder is initially synthesized in a radiofrequency plasma reactor where in-line passivation was carried out with oxygen gas, resulting in the formation of nickel oxidecoated nickel particles. Following this, platinum nanoparticles are deposited onto the surface of the oxidecoated nickel nanopowder, forming Pt0/Ni@NiO nanocatalysts for the hydrolytic dehydrogenation of ammonia borane. The Pt0/Ni@NiO nanoparticles, containing 0.24 % wt. Pt, exhibit remarkable catalytic activity in the hydrolytic dehydrogenation of ammonia borane, with a turnover frequency of 468 (mol H2)×(mol Pt)−1×min−1 for releasing 3 equivalent H2 gas per mole of ammonia borane from its hydrolysis at 25 ºC. This heightened catalytic activity of Pt0/Ni@NiO nanoparticles is attributed to the favorable metal-support interaction between the platinum(0) nanoparticles and oxide surface, namely the bonding of platinum to the oxide surface, as elucidated by the XPS analysis. More importantly, Pt0/Ni@NiO nanoparticles can be separated from the reaction solution by using an external magnet.

Rolling Element Bearing Damage in the Presence of Applied Electric Current

Modern wind turbines and battery electric vehicles have bearings in close proximity to electrical generators, motors, and inverters. These systems have motivated new research focused on damage mechanisms associated with low- and high-level electric currents in rolling element bearings. This work presents a study on the influence of applied electric current and lubricant selection on bearing surface damage. Direct current was applied to a rotating tapered roller bearing with axial load and oil lubrication. Tests were conducted with various levels of applied current and two different oils (additized and non-additized). Micropitting, white etching cracking (WEC), and the formation of a surface white layer were investigated using both optical microscopy and scanning electron microscopy. Some of the tested bearings had black oxide surface treatment on their rollers and raceways. The black oxide was evaluated with regard to the prevention of the WEC damage mode. The occurrence of the described damage modes depended on the type of oil used and the application of electric current. Higher electric currents increased bearing surface damage in these tests.

Corrosion Behavior of 20G and TP347H in Molten LiCl-NaCl-KCl Salt.

The corrosion behavior of 20G and TP347H materials was investigated in molten LiCl-NaCl-KCl salt. The corrosion rates of these materials in molten chloride salt are high and are strongly affected by the alloying surface oxide formation. The 20G shows uniform surface corrosion with almost no protective oxide formation on the surface. In contrast, the austenitic steel TP347H exhibits better corrosion resistance in molten chloride salts due to its high Cr content. Owing to the highly corrosive nature of molten chloride salts, the Cl- in molten salt could react with oxides and alloy, inducing intergranular corrosion of austenitic steel in molten chloride salt environments.

Redox behavior of unsubstituted cobalt phthalocyanine in nanostructured Langmuir-Schaefer films

Although the properties of unsubstituted metal tetrapyrroles in solutions have received attention in numerous work, the physico-chemistry of their thin films remains poorly investigated. In this work, we constructed thin films of unsubstituted cobalt phthalocyanine on the surface of quartz plates and indium tin oxide (ITO) electrodes using the Langmuir-Schaefer (LS) and drop casting techniques. In LS films, CoPc species are involved in strong intermolecular interactions, which result in formation of CoPc nanostructures and prominent changes in the ultraviolet-visible spectrum. Electrochemical reduction of CoPc in LS films at −0.9 V (versus silver chloride electrode) results in formation of Co(I) species. In contrast to the highly reactive nature of Co(I)Pc in solution, these species generated in thin films are relatively resistant to dioxygen due to the dense packing of CoPc units. These findings can further the development of CoPc-based resistive sensors utilizing not only common Co(II), but also Co(I) species, which may possess different sensitivity toward analytes.

Spatiotemporal variability of surface ozone and associated meteorological conditions over the Arabian Peninsula

This study investigates the spatiotemporal variability of surface ozone (O3) over the Arabian Peninsula (AP) between 2005 and 2019, focusing on the Arabian Gulf (AG). The analysis explores the relationship between surface O3 data from the Copernicus Atmosphere Monitoring Service (CAMS) with boundary layer height (BLH), 2 m temperature (T2M), downward ultraviolet radiation at the surface (UVB), and 10 m wind speed (WS) and direction from the fifth generation European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis (ERA5). Also, the study considers Carbon Monoxide (CO) and Nitrogen Oxides (NOx) surface emissions from the Tropospheric Chemical Reanalysis version 2 (TCR-2). Furthermore, it investigates the impact of El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) on surface O3 variations on a seasonal scale. Surface O3 observations from 15 ground-based stations across the AP were used to evaluate CAMS-O3, showing a good agreement between CAMS and the observations. The analysis of mean diurnal variations of CAMS-O3 and ERA5 reveals that surface O3 is highest over the eastern parts of the AP, mainly the AG, peaking during summer, followed by spring, fall, and winter. This seasonal cycle is also observed, to a large degree, in BLH, T2M, UVB, and WS. The results also reveal insignificant correlation between surface O3 and ENSO, but stronger correlation with IOD, especially over the AG during summer and fall. The analysis indicates that elevated T2M and UVB during daytime and elevated BLH during nighttime are significant contributors to increased levels of O3 over the AG.