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The surface oxidation of 2D transition metal dichalcogenides (TMDs) has recently gained tremendous technological and fundamental interest owing to the multi‐functional properties that the surface oxidized layer opens up. In particular, when integrated into other 2D materials in the form of van der Waals heterostructures, oxidized TMDs enable designer properties, including novel electronic states, engineered light‐matter interactions, and exceptional‐point singularities, among many others. Here, the evolving landscapes of the state‐of‐the‐art surface engineering technologies that enable controlled oxidation of TMDs down to the monolayer‐by‐monolayer limit are reviewed. Next, the use of oxidized TMDs in van der Waals heterostructures for different electronic and photonic device platforms, materials growth processes, engineering concepts, and synthesizing new condensed matter phenomena is discussed. Finally, challenges and outlook for future impact of oxidized TMDs in driving rapid advancements across various application fronts is discussed. [ABSTRACT FROM AUTHOR]

In this study, the oxidation of Ga–polar GaN(0001) surface simulated by using originally developed charge‐transfer‐type interatomic potential is reported on. The adjusted potential parameters reproduce the cohesive energies in the range of 0.3 eV atom−1 and atomic forces with correlation coefficient as high as 0.9, compared to the results of first‐principles calculations for more than 9000 structures associated with oxidation of GaN. The oxidation simulations reveal the formation of a periodic gallium oxide (GaOx) layer grown on GaN(0001) with O atoms replacing N atoms. The atomic distance between Ga–Ga in the GaOx layer along GaN[0001] direction is 3.05 Å, which is longer than wurtzite GaN (2.63 Å) and is quantitatively in agreement with the recent photoelectron holography measurement. The distances of the Ga atoms projected onto the GaN(11–20) plane are determined to be 3.19 Å for the GaOx layer and 2.79 Å for the interfacial GaN. These distances also align quantitatively with the scanning transmission electron microscopy imaging of the native oxide on GaN(0001). Further oxidation simulation in a larger model of 2304 atoms suggests the formation of the layered structure even in the subsequent layers away from the interface of GaN and gallium oxide. [ABSTRACT FROM AUTHOR]

[Display omitted] • Surface partially oxidized Re 3 Co 2 @NCF was synthesized via a hydrothermal followed by pyrolysis strategy. • The Re 3 Co 2 @NCF electrocatalyst exhibited outstanding HER performance and stability in alkaline condition. • The partially oxidized surfaces resulting from the electronic interaction between Re and Co led to the enhanced HER activity. Although the theoretical electrocatalytic activity of rhenium (Re) for the hydrogen evolution reaction is comparable to that of platinum, the experimental performance of reported rhenium-based electrocatalysts remains unsatisfactory. Herein, we report a highly efficient and stable electrocatalyst composed of rhenium and cobalt (Co) nanoalloy embedded in nitrogen-doped carbon film (Re 3 Co 2 @NCF). The Re 3 Co 2 @NCF electrocatalyst exhibited remarkable hydrogen evolution performance, with an overpotential as low as 30 ± 3 mV to reach a current density of 10 mA cm−2. In addition, the Re 3 Co 2 @NCF demonstrated exceptional stability over several days at a current density of 150 mA cm−2. Theoretical calculations revealed that alloying cobalt with rhenium altered the electronic structure of the metals, causing partial oxidation of the superficial metal atoms. This modification provided a balance for various intermediates' adsorption and desorption, thereby boosting the intrinsic activity of rhenium for hydrogen evolution reaction. This work improves the electrocatalytic performance of rhenium to its theoretical activity, suggesting a promising future for rhenium-based electrocatalysts. [ABSTRACT FROM AUTHOR]

The Ta2AlC material is designed to enhance the performance of Ag-based electrical contact materials as a reinforcement phase. With a work function of 6.7192 eV, Ta2AlC demonstrated significantly higher values than reinforcement phase materials such as SnO2, ZrO2, and the commonly used MAX phase materials. Consequently, the arc erosion performance of an Ag–Ta2AlC composite was investigated under air conditions. Gas breakdown mainly occurred due to electron avalanches, with the observation of a streamer breakdown mechanism in a strongly nonuniform field. The arc exhibited concentrated erosion on the surface of the Ag–20 vol% Ta2AlC material, resulting in a higher arc energy. As the volume fraction of the Ta2AlC material increased to 30% and 40%, the eroded area became more dispersed. In particular, Ag–30 vol% Ta2AlC displayed the lowest arc energy (3.395 kJ) and shortest arcing time (33.26 ms). Among the four tested components, the Ag–30 vol% Ta2AlC composite demonstrated superior arc erosion resistance. Oxides of Ag2O, AgO, Ta2O5, and Al2O3 were formed through the interaction of ionized Ag and Ta2AlC particles. By combining the electromagnetic force and plasma flow force, sputtered particles and bulges were generated on the eroded surface. These research findings contribute to broadening the applications of Ag–MAX materials in the realm of electrical contacts.

The oxidation of multi-walled carbon nanotubes (MWCNTs) using cold plasma was investigated for their subsequent use as adsorbents for the removal of dyes from aqueous solutions. The properties of MWCNTs after plasma modification and their adsorption capacities were compared with pristine and chemically oxidized nanotubes. The modification process employed a reactor where plasma was generated through dielectric barrier discharges (DBD) powered by high-voltage nanosecond pulses. Various modification conditions were examined, such as processing time and pulse voltage amplitude. The degree of oxidation and the impact on the chemistry and structure of the nanotubes was investigated through various physicochemical and morphological characterization techniques (XPS, BET, TEM, etc.). Maximum oxidation (O/C = 0.09 from O/C = 0.02 for pristine MWCNTs) was achieved after 60 min of nanopulsed-DBD plasma treatment. Subsequently, the modified nanotubes were used as adsorbents for the removal of the dye methylene blue (MB) from water. The adsorption experiments examined the effects of contact time between the adsorbent and MB, as well as the initial dye concentration in water. The plasma-modified nanotubes exhibited high MB removal efficiency, with adsorption capacity proportional to the degree of oxidation. Notably, their adsorption capacity significantly increased compared to both pristine and chemically oxidized MWCNTs (~54% and ~9%, respectively). Finally, the kinetics and mechanism of the adsorption process were studied, with experimental data fitting well to the pseudo-second-order kinetic model and the Langmuir isotherm model. This study underscores the potential of plasma technology as a low-cost and environmentally friendly approach for material modification and water purification. [ABSTRACT FROM AUTHOR]

Reducing silicon particle size in lithium-ion battery anodes not only mitigates surface stress, prevents pulverization, and reduces SEI film cracking but also significantly enhances surface area, thereby amplifying the impact of particle surface chemistry on performance. In this study, the surface of silicon particles with 80-nm diameter were oxidized in air to prepare Si@SiOx with a core–shell structure. We investigated the effect of different oxidation levels of the shell on the cycling performance of the nanosized silicon particles. The results showed that longer heating times decreased initial coulombic efficiency (ICE) but improved cycling performance. An interesting phenomenon was observed that, when the oxidation level was high, fast charging reduced battery capacity; while at lower oxidation levels, fast charging maintained or even slightly increased battery capacity. Based on electrochemical analysis, we proposed an explanation for this phenomenon: for small-sized nanoparticles with a large specific surface area, the effect of potential is particularly significant. The oxidation level of the particle surface affects the impedance of the SEI film, and high charge/discharge rates will also produce bias voltage, both of the two factors will limit the formation of crystallized Li15Si4 (c-Li15Si4). Reducing the amount of c-Li15Si4 can effectively improve the cycling performance of the electrode, but excessive bias voltage will sacrifice the lithium storage capacity of the electrode. For the designing of small size silicon particles, both factors should be considered. [ABSTRACT FROM AUTHOR]

The complex structure of Ti/HA (HA: hydroxyapatite) implants prepared by additive manufacturing technology plays an essential role in its application in bone repair. Digital light processing (DLP) is widely used to prepare bioceramics with complex structures. However, it is a challenge to prepare Ti/HA biomaterials by DLP due to the high ultraviolet (UV) absorption of Ti powder. In the present work, TiH2 powder coated with a TiO2 layer is selected to reduce the UV absorption and improve the curing depth for DLP printed green bodies of TiO2@TiH2/HA, because the TiO2@TiH2 powder can be reduced by 12.7% compared to the TiH2 powder without any oxidation. Then, the shell layer of TiO2 undergoes dehydrogenation and reduction reaction with the core phase of TiH2 during the sintering process to transfer TiO2@TiH2/HA into TixOy@Ti/HA. In addition, the effects of HA content on compressive strength and biocompatibility are investigated in the TixOy@Ti/HA biomaterials. The results show that when adding 60 vol%HA, the maximum monolayer curing depth of the slurry reaches 90.1 ± 3.5 µm. 40%TixOy@Ti/60%HA shows the maximum effect in promoting the pre‐osteoblast differentiation and a relatively high compressive strength of 48.7 ± 3.5 MPa. This work provides an experimental basis for the preparation of ceramic–metal composites with high UV absorptivity using DLP. [ABSTRACT FROM AUTHOR]

Abstract The surface oxidation of 2D transition metal dichalcogenides (TMDs) has recently gained tremendous technological and fundamental interest owing to the multi‐functional properties that the surface oxidized layer opens up. In particular, when integrated into other 2D materials in the form of van der Waals heterostructures, oxidized TMDs enable designer properties, including novel electronic states, engineered light‐matter interactions, and exceptional‐point singularities, among many others. Here, the evolving landscapes of the state‐of‐the‐art surface engineering technologies that enable controlled oxidation of TMDs down to the monolayer‐by‐monolayer limit are reviewed. Next, the use of oxidized TMDs in van der Waals heterostructures for different electronic and photonic device platforms, materials growth processes, engineering concepts, and synthesizing new condensed matter phenomena is discussed. Finally, challenges and outlook for future impact of oxidized TMDs in driving rapid advancements across various application fronts is discussed.

Titanium carbide (TiC) exhibits excellent chemical stability and high electrical conductivity, making it suitable for composites with unique structures and exceptional absorption abilities. In this work, TiO2@TiC composites with varied morphology were synthesized by oxidizing TiC at 400°C, for various durations. With the increase of oxidation time, small white TiO2 particles grew in situ on the surface of TiC particles, ultimately leading to the formation of a continuous structure in which TiO2 covered the surface of the TiC particles. These results indicate that the impedance matching and electromagnetic wave (EMW) absorption properties of TiO2@TiC composites can be modified by adjusting the oxidation time. The minimum reflection loss (RLmin) of the highly oxidized TiO2@TiC composite (TO-4 sample) reached −16.2 dB at a thickness of 2.9 mm. When the thickness was increased from 1.2 mm to 4.7 mm, the composites achieved the broadest effective absorption bandwidth of 13 GHz (from 5 to 18 GHz). These enhanced EMW absorption properties can be ascribed to the presence of defects, pores, heterointerfaces, TiO2, and TiC within the composites, which induce dipole polarization loss, interface polarization loss, and conduction loss. This practical solution provides a method for preparing TiO2@TiC materials with EMW-absorbing properties using oxidation technology. [ABSTRACT FROM AUTHOR]

The change in surface properties of long-flame coal of limited metamorphic development on steeping with mixtures based on Portland cement is considered. The passivating liquids employed are the filtrate and suspension of cement solution used in grouting the bottom of mine workings. Treatment of coal with mineralized cement mixtures transforms surface groups that may be oxidized to groups that cannot be oxidized. The mineral layer formed on the coal surface prevents the development of oxidation. The results indicate that cement suspensions may be used to reduce the oxidation of the coal's contact surface in mine workings. [ABSTRACT FROM AUTHOR]

Copyright of New Building Materials / Xinxing Jianzhu Cailiao is the property of New Building Materials 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.)

The demand for soft magnetic amorphous metal powders with high saturation magnetization values and low energy loss has increased to achieve high-performance inductors for mobile electronic devices. In this study, Fe-based Fe92.3Si3.5B3.0C0.7P0.5 (wt.%) amorphous metal powders were prepared using different atomization methods for controlling the surface oxidation of the metal alloy powder. Conventional high-pressure water atomization and the newly developed high-speed water screen atomization methods were used for preparation. Regardless of the preparation methods, both alloy powders were amorphous, and their magnetic flux density (Bs) values were more than 165 emu/g. Compared to the powders from the conventional high-pressure water atomization method, the amorphous metal powder manufactured using the high-speed water screen atomization process had lower eddy current loss because of the formation of a thin and uniform oxide layer. Furthermore, the magnetic properties of the consolidated magnetic cores fabricated with the amorphous powders produced by the high-speed water screen atomization method using compact-pressing techniques were characterized. Magnetic powders with fewer surface oxidation layers exhibited increased initial permeability and a smaller coercive field, leading to a lower core loss value. The magnetic core made from Fe92.3Si3.5B3.0C0.7P0.5 (wt.%) amorphous powder with an oxide content of 0.12 (wt.%) using the high-speed water screen atomization method exhibited an initial permeability of 25 in the frequency range up to 5 MHz, and a loss of 237 mW/cm3 with Bm = 0.2 T at 1 MHz. [ABSTRACT FROM AUTHOR]

We investigated the impacts of spherical and triangular-plate-shaped lipid-coated silver nanoparticles (AgNPs) designed to prevent surface oxidation and silver ion (Ag+) dissolution in a small-scale microcosm to examine the role of shape and surface functionalization on biological interactions. Exposures were conducted in microcosms consisting of algae, bacteria, crustaceans, and fish embryos. Each microcosm was exposed to one of five surface chemistries within each shape profile (at 0, 0.1, or 0.5 mg Ag/L) to investigate the role of shape and surface composition on organismal uptake and toxicity. The hybrid lipid-coated AgNPs did not result in any significant release of Ag+ and had the most significant toxicity to D. magna, the most sensitive species, although the bacterial population growth rate was reduced in all exposures. Despite AgNPs resulting in increasing algal growth over the experiment, we found no correlation between algal growth and the survival of D. magna, suggesting that the impacts of the AgNPs on bacterial survival influenced algal growth rates. No significant impacts on zebrafish embryos were noted in any exposure. Our results demonstrate that the size, shape, and surface chemistry of AgNPs can be engineered to achieve specific goals while mitigating nanoparticle risks. [ABSTRACT FROM AUTHOR]

Use and performance criteria of photonic devices increase in various application areas such as information and communication, lighting, and photovoltaics. In many current and future photonic devices, surfaces of a semiconductor crystal are a weak part causing significant photo-electric losses and malfunctions in applications. These surface challenges, many of which arise from material defects at semiconductor surfaces, include signal attenuation in waveguides, light absorption in light emitting diodes, non-radiative recombination of carriers in solar cells, leakage (dark) current of photodiodes, and light reflection at solar cell interfaces for instance. To reduce harmful surface effects, the optical and electrical passivation of devices has been developed for several decades, especially with the methods of semiconductor technology. Because atomic scale control and knowledge of surface-related phenomena have become relevant to increase the performance of different devices, it might be useful to enhance the bridging of surface physics to photonics. Toward that target, we review some evolving research subjects with open questions and possible solutions, which hopefully provide example connecting points between photonic device passivation and surface physics. One question is related to the properties of the wet chemically cleaned semiconductor surfaces which are typically utilized in device manufacturing processes, but which appear to be different from crystalline surfaces studied in ultrahigh vacuum by physicists. In devices, a defective semiconductor surface often lies at an embedded interface formed by a thin metal or insulator film grown on the semiconductor crystal, which makes the measurements of its atomic and electronic structures difficult. To understand these interface properties, it is essential to combine quantum mechanical simulation methods. This review also covers metal-semiconductor interfaces which are included in most photonic devices to transmit electric carriers to the semiconductor structure. Low-resistive and passivated contacts with an ultrathin tunneling barrier are an emergent solution to control electrical losses in photonic devices. [ABSTRACT FROM AUTHOR]

Al-containing MAX phase ceramic has demonstrated great potential in the field of high-performance low-voltage electrical contact material. Elucidating the anti-arc erosion mechanism of the MAX phase is crucial for further improving performance, but it is not well-understood. In this study, Ag/Ti3AlC2 electrical contact material was synthesized by powder metallurgy and examined by nanoindentation techniques such as constant loading rate indentation, creep testing, and continuous stiffness measurements. Our results indicated a gradual degradation in the nano-mechanical properties of the Ti3AlC2 reinforcing phase with increasing arc erosion times, although the rate of this degradation appeared to decelerate over arc erosion times. Specifically, continuous stiffness measurements highlighted the uneven mechanical properties within Ti3AlC2, attributing this heterogeneity to the phase’s decomposition. During the early (1–100 times) and intermediate (100–1000 times) stages of arc erosion, the decline in the nano-mechanical properties of Ti3AlC2 was primarily ascribed to the decomposition of Ti3AlC2 and limited surface oxidation. During the later stage of arc erosion (1000–6200 times), the inner region of Ti3AlC2 also sustained arc damage, but a thick oxide layer formed on its surface, enhancing the mechanical properties and overall arc erosion resistance of the Ag/Ti3AlC2.

BACKGROUND: Nickel foam (NF) is widely used as battery electrode matrix and electrochemical process cathode. However, the surface of NF is prone to oxidation, which may affect its ability to reduce oxygen and produce H2O2, but the influence mechanism is still unclear. In this paper, surface oxidation of the NF was regulated by pickling and drying pretreatment, and the surface oxides were characterized by X‐ray photoelectron spectroscopy (XPS) and energy dispersive X‐ray spectrometry (EDS). The NF was used as the substrate, graphite powder as the catalyst, and PTFE as the binder to prepare graphite‐coated NF composite electrodes. The effect of NF surface oxidation on their ability to generate H2O2 was investigated. RESULTS: The results demonstrated that after pickling and drying, the NF surface generated a large amount of NiO, which increased the charge transfer resistance of the NF by 20.3%, and accelerated further reduction decomposition of H2O2. The rotating ring‐disk electrode (RRDE) tests further confirmed that NiO can reduce the two‐electron oxygen reaction selectivity, which was detrimental to H2O2 electrosynthesis. The graphite‐coated NF composite electrode with pristine NF as the substrate can produce 869.1 mg L−1 of H2O2 and maintain relatively good reusability. CONCLUSION: Overall, the surface oxidation of NF is not conducive to H2O2 electrosynthesis, and it is necessary to prevent oxidation during electrode preparation. This study provides a valuable reference for the preparation of NF electrodes and can promote the further study of in situ H2O2 electrosynthesis. © 2023 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Gypsum-based composites are recognized as environmentally friendly and efficient materials suitable for modern construction. The mechanical properties of gypsum-based composites are crucial for determining their suitability for various applications. In this study, chopped carbon fibers (CCFs) were used to improve the compressive strength of gypsum materials. Hydrogen peroxide (H2O2) and sodium hypochlorite (NaClO) were used to oxidize the surface of CCFs to improve their dispersity in gypsum-based composites. The oxidized CCFs were dispersed using polycarboxylate ether superplasticizer (PCE), hydroxypropyl methyl cellulose ether (HPMC) dispersant and ultrasonic treatment, and the compressive strength of CCF-reinforced gypsum-based composites (CGC) was studied systematically. The surface roughness of oxidized CCFs increased with the content of hydrophilic oxygen-containing functional groups, such as hydroxyl (C-OH) and carbonyl (C=O) groups. The compressive strength of CGC was significantly improved by adding dispersed CCFs. The addition of 2.0 wt% of 3 mm CCFs and 1.0 wt% of 6 mm CCFs, dispersed using PCE, resulted in compressive strength enhancements of 50.9% and 72.4% of hardened gypsum, respectively. This improvement was attributed to the synergistic effect of PCE adsorption on the CCF surface and the steric hindrance between PCE and gypsum particles, promoting efficient dispersion of CCFs within the gypsum paste. [ABSTRACT FROM AUTHOR]

The efficient separation of chalcopyrite (CuFeS2) and galena (PbS) is essential for optimal resource utilization. However, finding a selective depressant that is environmentally friendly and cost effective remains a challenge. Through various techniques, such as microflotation tests, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM) observation, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy measurements, this study explored the use of ferric ions (Fe3+) as a selective depressant for galena. The results of flotation tests revealed the impressive selective inhibition capabilities of Fe3+ when used alone. Surface analysis showed that Fe3+ significantly reduced the adsorption of isopropyl ethyl thionocarbamate (IPETC) on the galena surface while having a minimal impact on chalcopyrite. Further analysis using SEM, XPS, and Raman spectra revealed that Fe3+ can oxidize lead sulfide to form compact lead sulfate nanoparticles on the galena surface, effectively depressing IPETC adsorption and increasing surface hydrophilicity. These findings provide a promising solution for the efficient and environmentally responsible separation of chalcopyrite and galena. [ABSTRACT FROM AUTHOR]

As a new type of nuclear reactor, the Gen-IV reactor attracts increasing interest from the industry. Tritium is produced in lead-cooled fast reactors (LFR), sodium-cooled fast reactor (SFR), and other Gen-IV reactors. It is necessary to study the tritium permeation behavior of 15-15Ti stainless steel as a candidate cladding and structural material in Gen-IV reactors. In this study, gas-driven permeation experiments were conducted to measure the high-temperature deuterium transport behavior parameters of 15-15Ti stainless steel. The results showed that the deuterium permeation behavior of 15-15Ti and 316L stainless steels is similar. Additionally, this study discussed the effects of microstructures and surface oxidation on the permeability of stainless steels. This study will aid in evaluating tritium permeation in lead-based fast reactors and other Gen-IV reactors and whether tritium permeation barrier or tritium-removal devices are necessary. • The deuterium transport behavior of 15-15Ti stainless steel was investigated through gas-driven permeation experiments. • The deuterium permeation behavior of 15-15Ti stainless steel is similar to that of 316L stainless steel. • The effects of microstructure and surface oxidation films on the permeability of 15-15Ti stainless steels were discussed. [ABSTRACT FROM AUTHOR]

The oxidation of multi-walled carbon nanotubes (MWCNTs) using cold plasma was investigated for their subsequent use as adsorbents for the removal of dyes from aqueous solutions. The properties of MWCNTs after plasma modification and their adsorption capacities were compared with pristine and chemically oxidized nanotubes. The modification process employed a reactor where plasma was generated through dielectric barrier discharges (DBD) powered by high-voltage nanosecond pulses. Various modification conditions were examined, such as processing time and pulse voltage amplitude. The degree of oxidation and the impact on the chemistry and structure of the nanotubes was investigated through various physicochemical and morphological characterization techniques (XPS, BET, TEM, etc.). Maximum oxidation (O/C = 0.09 from O/C = 0.02 for pristine MWCNTs) was achieved after 60 min of nanopulsed-DBD plasma treatment. Subsequently, the modified nanotubes were used as adsorbents for the removal of the dye methylene blue (MB) from water. The adsorption experiments examined the effects of contact time between the adsorbent and MB, as well as the initial dye concentration in water. The plasma-modified nanotubes exhibited high MB removal efficiency, with adsorption capacity proportional to the degree of oxidation. Notably, their adsorption capacity significantly increased compared to both pristine and chemically oxidized MWCNTs (~54% and ~9%, respectively). Finally, the kinetics and mechanism of the adsorption process were studied, with experimental data fitting well to the pseudo-second-order kinetic model and the Langmuir isotherm model. This study underscores the potential of plasma technology as a low-cost and environmentally friendly approach for material modification and water purification.

Electrical breakdown is an important physical phenomenon in power equipment and electronic devices. Recently, the mechanism of AC and DC breakdown has been preliminarily revealed as electrode–dielectric interface breakdown and bulk breakdown, respectively, based on space charge dynamics through numerical calculations. However, the AC breakdown mechanism still lacks enough direct experimental support, which restricts further understanding and the design and development of electrical structures. Here, in this study, LDPE films with various thicknesses ranging from 33 μm to 230 μm were surface modified with ozone for different durations to experimentally investigate DC and AC breakdown mechanism. The results indicate that carbonyl groups (C=O) were introduced onto the film surface, forming shallow surface traps and leading to a decreased average trap depth and an increased trap density. Such a surface oxidation modulated trap distribution led to enhanced space charge injection and bulk electrical field distortion, which decreased DC breakdown strength as the oxidation duration went longer, in all film thicknesses. However, such decreases in breakdown strength occurred only in films below 55 μm under AC stresses, as the enhanced electrical field distortion at the electrode–dielectric interface was more obvious and dominating in thin films. These experimental results further confirm the proposed electrode–dielectric interface breakdown of dielectric films and provide new understandings of space charge modulated electrical breakdown, which fulfills dielectric breakdown theory and benefits the miniaturization of power equipment and electronic devices. [ABSTRACT FROM AUTHOR]

In the vast family of two-dimensional (2D) van der Waals materials, 2D magnets have unique advantages in the experimental realization of numerous theoretical works and fundamental exploration of high-performance spintronic devices in the 2D limit. Fe3GeTe2 (FGT), as a typical 2D metallic ferromagnet, is a promising candidate to achieve functional devices at room temperature due to its relatively high Curie temperature (TC) and strong perpendicular magnetic anisotropy (PMA). Here, we investigated self-modulated magnetic properties of FGT nanoflakes in an ambient environment by anomalous Hall effect (AHE). Unique double square-shaped hysteresis loops are observed in oxidized Fe3GeTe2 nanoflakes induced by ambient effects. We propose a phenomenological model based on antiferromagnetic/ferromagnetic coupling in the FGT nanoflakes with oxidized surface layers to elucidate this observation. Compared with a single square-shaped hysteresis loop of well-preserved FGT, double square-shaped hysteresis loops exhibit four-resistance plateaus, which can be regarded as a kind of media for information storage or sensing, showing potential applications in next-generation spintronic devices. [ABSTRACT FROM AUTHOR]

Lytic polysaccharide monooxygenases (LPMOs) catalyze the oxidation of β-(1,4)-linked polysaccharides, such as cellulose, in a reaction that requires an electron donor and H2O2 as co-substrate. Several LPMOs include a carbohydrate-binding module (CBM), which promotes action on insoluble substrates. Herein, a fluorescent labeling technique was used to track LPMO action on microcrystalline cellulose and evaluate the impact of CBMs on the distribution of LPMO activity across the fiber surface. Confocal microscopic images revealed that the distribution of oxidized positions on the cellulose surface was CBM-dependent: fluorescent spots were concentrated in reactions with a CBM-containing LPMO whereas they were more dispersed for a CBM-deficient LPMO variant. The more dispersed oxidation pattern for the CBM-free LPMO coincided with the release of fewer soluble reaction products. [ABSTRACT FROM AUTHOR]

Low-temperature joining of SiC ceramics using raw CaO-Al 2 O 3 -MgO-SiO 2 mixed powders (CAMS-P) and CaO-Al 2 O 3 -MgO-SiO 2 glass (CAMS-G) as additives for the liquid-phase sintering of SiC nanopowders (NITE phase) in combination with surface oxidation was studied. Using CAMS-P as an additive for SiC joining required 1650 °C and produced a lower shear strength of 77.2 ± 3.5 MPa, compared to untreated SiC (108.2 ± 15.8 MPa). Using CAMS-G as an additive, the compactness of SiC joints obtained at 1550 °C was higher than that of NITE joints obtained at 1650 °C with CAMS-P as an additive. Nonetheless, the low joining temperature resulted in gaps and delaminations at the interface, and the joints strength was only 48.3 ± 5.6 MPa. Incorporating CAMS-G as an additive and surface oxidation achieved reliable NITE phase joining at 1550 °C, with no observed gaps or delaminations at the interface. The resulting joints strength was as high as 100.0 ± 0.8 MPa. The joining mechanism was discussed and compared, involving microstructural analysis. [ABSTRACT FROM AUTHOR]

The structural properties of Fe in celadon glazes provide information about its production process and coloration mechanism. We provide a spatial perspective to the Fe properties of reduction-fired celadon glazes using depth-resolved Fe K-edge X-ray absorption spectroscopy (XAS) performed on the glaze cross-sections. The XAS spectra collected from the cross-sections were compared to those collected from the surfaces. The depth-resolved XAS results show that surface oxidation occurs with a typical reduction-firing profile. A 30–60 μ m transition region between two Fe valency proportions near the surface and the glaze interior was observed. The XAS spectra taken from the surfaces showed that it is sensitive to only ∼ 10 0 –10 1 μ m near the surface. The possibility of surface oxidation in synthetic glazes or ceramic artifacts limits the interpretation of fluorescence XAS spectra collected from glaze surfaces because it does not always represent the properties of the glaze interior and the glaze as a whole. • Surface oxidation and depth profile of Fe valencies were observed in celadon glaze. reduction-fired celadon glaze. • The interpretation of glaze surface XAS spectra is limited by surface oxidation. • Surface oxidation is affected by cooling atmosphere and Fe content in celadon glaze. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) ceramics are widely used as structural materials for various applications. However, the extraordinarily high hardness, brittleness, low material removal rate, and severe tool wear of these materials significantly impact the performance of conventional mechanical processing techniques. In this study, we investigated the influence of different parameters on the material removal rate, surface quality, and surface oxidation during the laser processing of SiC ceramic samples using a high-repetition-frequency femtosecond laser at a wavelength of 1030 nm. Additionally, an experimental investigation was conducted to analyze the effects of a burst mode on the material removal rate. Our results demonstrate that the surface oxidation, which significantly affects the material removal rate, can be effectively reduced by increasing the laser scanning speed and decreasing the laser scanning pitch. The material removal rate and surface quality are mainly affected by laser fluence. The optimal material removal rate is obtained with a laser fluence of 0.4 J/cm2 at a pulse width of 470 fs. [ABSTRACT FROM AUTHOR]

The development and evaluation of novel stainless steel-based composites for direct contact with liquid aluminum alloys has been carried out. The Steel Ceramic Composite consisted of 60 vol% 316L stainless steel powder and 40 vol% of MgO or TiO2 ceramic powder. The sample were manufactured using uniaxial pressing and subsequent surface pre-oxidation at 850, 1000 °C for 24 h.The corrosion resistance of composite was investigated against molten AlSi7Mg0.3 alloy using crucible corrosion tests. The tests were carried out at 850 °C for 24 h and 168 h. The influence of pre-oxidation on the corrosion resistance of the samples was analyzed using XRD and SEM/EDS. The corrosion phases formed in the aluminum alloy were investigated using SEM/EDS/EBSD and PSEM/ASPEX/AFA and included the assessment of aluminum alloy contamination by evaluation of corrosion precipitation content, quantity and size. The sample Steel-MgO exhibited excellent corrosion resistance with negligible contamination of the aluminum alloy.

The formation of functional metal oxide crystals is widely required in CMOS backend processes. Recently, digitally processed DC sputtering (DPDS) was developed as an alternative layer-by-layer process to pulsed-laser deposition (PLD) for device development. DPDS enables the alternating process of depositing ultra-thin layers of metals and oxidizing them by using pulses of reactive gases that are partially synchronized with the sputtering of specific metals. However, it was found that crystallites were formed inhomogeneously due to damage by oxygen radicals, and there was room for improvement in crystallinity. Therefore, pulsed non-radical oxidation (NRO) was introduced into DPDS to avoid radical damage. We therefore designed a DPDS sequence using dual-cathode sputtering and gas pulses synchronized with sputtering interruptions. The sufficient oxidation for the metal few layers using NRO was confirmed. We also demonstrated the space group control of monoclinic (Er0.1Y0.9)2SiO5 and the reduction of oxygen vacancies, due to DPDS-NRO. [ABSTRACT FROM AUTHOR]

Copyright of Acta Scientiarum Naturalium Universitatis Sunyatseni / Zhongshan Daxue Xuebao is the property of Sun-Yat-Sen University 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.)

Boron-containing materials, and in particular boron nitride, have recently been identified as highly selective catalysts for the oxidative dehydrogenation of alkanes such as propane. To date, no mechanism exists that can explain both the unprecedented selectivity, the observed surface oxyfunctionalization, and the peculiar kinetic features of this reaction. We combine catalytic activity measurements with quantum chemical calculations to put forward a bold new hypothesis. We argue that the remarkable product distribution can be rationalized by a combination of surface-mediated formation of radicals over metastable sites, and their sequential propagation in the gas phase. Based on known radical propagation steps, we quantitatively describe the oxygen pressure-dependent relative formation of the main product propylene and by-product ethylene. Free radical intermediates most likely differentiate this catalytic system from less selective vanadium-based catalysts.

Solid-state cold spray additive manufacturing (CSAM) was used to fabricate pure tantalum (Ta) and the high-temperature mechanical and deformation behavior of this material was investigated. The pure Ta fabricated using CSAM consists of irregularly shaped powder particles elongated in the direction perpendicular to the spraying direction. In addition, microstructural evolution occurs in the process of accommodating harsher plastic deformation along the boundaries between powder particles. Compression test results confirmed that the room temperature yield strength was approximately 901 MPa, which is four to six times higher than that of pure Ta produced using conventional processes such as vacuum arc melting etc. Moreover, CSAM Ta has excellent mechanical properties even at high temperatures, and these properties were confirmed to be retained up to approximately 950 °C. Surface and microstructural observations after deformation revealed that the sample crumbled in a compression test at 800 °C. However, the sample retained its shape at temperatures above 800 °C. This phenomenon was a result of the interaction between high-temperature oxidation behavior and microstructural evolution, i.e. dynamic recrystallization. Based on these findings, the relationship among the microstructure, room-to high-temperature mechanical properties, and deformation behaviors are also discussed.

Understanding the process of oxidation on the surface of GaN is important for improving metal-oxide-semiconductor (MOS) devices. Real-time X-ray photoelectron spectroscopy was used to observe the dynamic adsorption behavior of GaN surfaces upon irradiation of H2O, O2, N2O, and NO gases. It was found that H2O vapor has the highest reactivity on the surface despite its lower oxidation power. The adsorption behavior of H2O was explained by the density functional molecular dynamic calculation including the spin state of the surfaces. Two types of adsorbed H2O molecules were present on the (0001) (+c) surface: non-dissociatively adsorbed H2O (physisorption), and dissociatively adsorbed H2O (chemisorption) molecules that were dissociated with OH and H adsorbed on Ga atoms. H2O molecules attacked the back side of three-fold Ga atoms on the (0001̅) (−c) GaN surface, and the bond length between the Ga and N was broken. The chemisorption on the (101̅0) m-plane of GaN, which is the channel of a trench-type GaN MOS power transistor, was dominant, and a stable Ga-O bond was formed due to the elongated bond length of Ga on the surface. In the atomic layer deposition process of the Al2O3 layer using H2O vapor, the reactions caused at the interface were more remarkable for p-GaN. If unintentional oxidation can be resulted in the generation of the defects at the MOS interface, these results suggest that oxidant gases other than H2O and O2 should be used to avoid uncontrollable oxidation on GaN surfaces.

This review focuses on techniques for modifying the surface of carbon that is produced from sustainable resources, such as pyrolytic carbon. Many of these materials display high specific surface area and fine particle distribution. Functionalization of a surface is a commonly used approach in designing desired surface properties of the treated material while retaining its bulk properties. Usually, oxidation is a primary step in carbon functionalization. It can be performed as wet oxidation, which is a type of chemical surface modification. Wet oxidation is usually performed using nitric acid and hydrogen peroxide, as well as using hydrothermal and solvothermal oxidation. On the other side, dry oxidation is representative of physical surface modification. This method is based on corona discharge and plasma oxidation which are promising methods that are in line with green chemistry approaches. Whilst the oxidation of the carbon surface is a well-known method, other chemical modification techniques, including cycloadditions and various radical reactions on graphene layers, are presented as an alternative approach. Regarding secondary functionalization, coupling organosilanes to activated carbon is a common technique. Organosilanes bearing reactive groups present a bridge between inorganic species and polymer systems, e.g., epoxy and polyurethane resins, and facilitate the use of carbonaceous materials as reinforcing components for polymers and thermosetting resins. Along with the presented functionalization methods, this review also provides an overview of new applications of modified (i.e., functionalized) carbon materials, e.g., for the building industry, wastewater treatment, semiconducting materials and many more. [ABSTRACT FROM AUTHOR]

The aim of this study is to design viable eco-friendly adsorbents that may be further employed for detoxifying living organisms or decontaminating polluted waters of heavy metal ions. Here are highlighted some results concerning the surface chemistry modification of pectins via oxidation of apple-fruits with ozone in water, concentrated hydrogen peroxide or ozone in hydrogen peroxide. The quality and quantity of carboxylic and phenolic functional groups on intact and chemically-modified pectins were established by using the Boehm titration method, which has shown that these have increased in all cases—especially for three times when using ozone in hydrogen peroxide. Textural changes in the surface of were determined by scanning electron microscopy (SEM) and adsorption–desorption of nitrogen; by oxidation, both the specific surface area and total volume of pores increase, the most significant one being encountered in the case of the sample oxidized with ozone in hydrogen peroxide (three times and, respectively, four times higher). The thermal behaviour and stability of the oxidized pectins versus intact pectins from apple-fruits was studied by thermogravimetry (TG), derivative thermogravimetry (DTG) and differential thermal analysis (DTA) in both inert (nitrogen) and oxidative (air) atmospheres; the thermal behaviour indicates just slight modifications due to the appearance of carboxylic and phenolic functional groups, while the overall stability was basically not affected. The sorption properties of these materials were investigated for the immobilization of Pb2+ and Hg2+ from aqueous solutions, by measuring the adsorption isotherms; the chemical modification of pectins by oxidation has significantly improved the adsorption capacity. [ABSTRACT FROM AUTHOR]

van der Waals In2Se3 has attracted significant attention for its room‐temperature 2D ferroelectricity/antiferroelectricity down to monolayer thickness. However, instability and potential degradation pathway in 2D In2Se3 have not yet been adequately addressed. Using a combination of experimental and theoretical approaches, we here unravel the phase instability in both α‐ and β′‐In2Se3 originating from the relatively unstable octahedral coordination. Together with the broken bonds at the edge steps, it leads to moisture‐facilitated oxidation of In2Se3 in air to form amorphous In2Se3−3xO3x layers and Se hemisphere particles. Both O2 and H2O are required for such surface oxidation, which can be further promoted by light illumination. In addition, the self‐passivation effect from the In2Se3−3xO3x layer can effectively limit such oxidation to only a few nanometer thickness. The achieved insight paves way for better understanding and optimizing 2D In2Se3 performance for device applications. [ABSTRACT FROM AUTHOR]

Surface oxidation, as one of fundamental chemical reactions in metals, greatly affects their properties. Herein, we develop a new quaternary GaInSnZn liquid metal with the melting temperature of 9.7 °C, which is the lowest among all reported Ga-based liquid metals. With high-resolution transmission electron microscopy, we directly observed the oxide layer formed on the surface of the liquid metal. The initially formed oxide layer is revealed to be amorphous and very sensitive to electron beam. Prolonged irradiation results in its structural change from amorphous to crystalline phases. The present finding refreshes the basic understanding of surface oxidization of liquid metals and opens up the possibility of tuning surface structures and morphologies by using electron beam irradiation.

Surface oxidation, as one of fundamental chemical reactions in metals, greatly affects their properties. Herein, we develop a new quaternary GaInSnZn liquid metal with the melting temperature of 9.7 °C, which is the lowest among all reported Ga-based liquid metals. With high-resolution transmission electron microscopy, we directly observed the oxide layer formed on the surface of the liquid metal. The initially formed oxide layer is revealed to be amorphous and very sensitive to electron beam. Prolonged irradiation results in its structural change from amorphous to crystalline phases. The present finding refreshes the basic understanding of surface oxidization of liquid metals and opens up the possibility of tuning surface structures and morphologies by using electron beam irradiation.

Oxygen defects govern the behavior of a range of materials spanning catalysis, quantum computing, and nuclear energy. Understanding and controlling these defects is particularly important for the safe use, storage, and disposal of actinide oxides in the nuclear fuel cycle, since their oxidation state influences fuel lifetimes, stability, and the contamination of groundwater. However, poorly understood nanoscale fluctuations in these systems can lead to significant deviations from bulk oxidation behavior. Here we describe the use of aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy to resolve changes in the local oxygen defect environment in [Formula: see text] surfaces. We observe large image contrast and spectral changes that reflect the presence of sizable gradients in interstitial oxygen content at the nanoscale, which we quantify through first-principles calculations and image simulations. These findings reveal an unprecedented level of excess oxygen incorporated in a complex near-surface spatial distribution, offering additional insight into defect formation pathways and kinetics during [Formula: see text] surface oxidation.

In this study, chalcopyrite was oxidized in hydrogen peroxide (H2O2) solutions of different concentrations to simulate different degrees of oxidation in real ores, and the effects of H2O2 treatment on chalcopyrite surface properties and flotation performance were investigated by surface analysis techniques and floatation experiments, which implied the reason for the poor grade and recovery of oxidized chalcopyrite concentrate in the production process of the ore. Flotation results showed that when the concentration of H2O2 increased from 0% (by weight) to 5%, the flotation recovery of chalcopyrite decreased sharply. However, with increasing H2O2 concentration from 5% to 30%, chalcopyrite recovery improved relatively to different degrees with different collector concentrations. Analyses of X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma-atomic optical emission spectrophotometry (ICP-OES) results indicated that the pretreatment with H2O2 caused that hydrophilic substance formed on chalcopyrite surface with the dissolution of copper ions, and the dissolution amount of copper increased with the increase of H2O2 concentration. UV–visible spectrophotometer and Fourier transform infrared spectrum (FTIR) studies indicated that the pretreatment of chalcopyrite with H2O2 had little effect on the adsorption amount of potassium butyl xanthate (PBX) on chalcopyrite surface. However, due to the dissolution of copper ions, PBX interacted with chalcopyrite mainly as buthyl dixanthogen (BX)2.

Carbon surface oxidation was investigated to assess the effects of porosity and particle size on its course. Carbon xerogels that differed in porosity (micro-, micro-meso-, and micro-meso-macroporous materials) and particle size (from fine powders to monolithic cubes) were prepared. The prepared materials were characterized in detail with nitrogen sorption, SEM, and HRTEM. The oxidation of carbon xerogels was studied by isothermal thermogravimetry (TG) in an oxidizing atmosphere (50% O 2 and 50% Ar). Isothermal TG experiments showed that the effects of particle size and porosity are interrelated and should be evaluated together as both significantly influence diffusion and heat transfer during carbon oxidation. On the basis of isothermal TG data, apparent kinetic parameters were determined assuming that carbon burn-off, the creation of oxygen surface groups, and the decomposition of created oxygen surface groups are reactions controlling the carbon surface oxidation. Detailed analysis of the obtained parameters proved that porosity and particle size do not affect the basic chemical reactions that occur on the carbon surface during oxidation. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Repulsive interaction of oxidized carbon black reduced agglomeration. • Onset of solidification was shifted to higher particle loadings. • Electronic conductivities of aqueous suspensions were independent of shear intensity. • Lower viscosity, higher conductivity fluid suspensions were formed. • Electrostatic stability does not lead to desired conductive additive performance. The macroscopic properties of carbon black suspensions are primarily determined by the agglomerate microstructure built of primary aggregates. Conferring colloidal stability in aqueous carbon black suspensions should thus have a drastic impact on their viscosity and conductivity. Carbon black was treated with strong acids following a wet oxidation procedure. An analysis of the resulting particle surface chemistry and electrophoretic mobility was performed in evaluating colloidal stability. Changes in suspension microstructure due to oxidation were observed using small-angle X-ray scattering. Utilizing rheo-electric measurements, the evolution of the viscosity and conductivity of the carbon black suspensions as a function of shear rate and carbon content was thoroughly studied. The carboxyl groups installed on the carbon black surface through oxidation increased the surface charge density and enhanced repulsive interactions. Electrostatic stability inhibited the formation of the large-scale agglomerates in favor of the stable primary aggregates in suspension. While shear thinning, suspension conductivities were found to be weakly dependent on the shear intensity regardless of the carbon content. Most importantly, aqueous carbon black suspensions formulated from electrostatically repulsive primary aggregates displayed a smaller rise in conductivity with carbon content compared to those formulated from attractive agglomerates. [ABSTRACT FROM AUTHOR]

The friction behavior of rough polycrystalline diamond (PCD) surfaces is important in many applications and devices that are required to operate in various harsh environments and it can be argued that a thorough understanding of the friction behavior is essential to the application performance. However, the interplay between electrochemical corrosion, capillary adhesion and friction behavior of PCD in multi-asperity contacts is still poorly understood. In this work, we quantify the interfacial capillary adhesion at contact interfaces and its effect on the friction response, between a colloidal microsphere and rough PCD films before and after electrochemical corrosion, for water-immersed, low RH, and humid air conditions. For these multi-asperity contacts, we demonstrate how electrochemical corrosion influences the surface hydrophilicity of the PCD surfaces, and how capillary adhesion due to water condensation contributes to the friction force. We estimate the capillary forces from both the microscopic lateral force experiments and elastoplastic boundary element method (BEM) contact calculations. The combined results indicate strongly that the observed increase in friction force on electrochemically-corroded PCD surfaces is governed by enhanced capillary adhesion at the contact interface, as affected by surface hydrophilicity and environmental humidity. [Display omitted] [ABSTRACT FROM AUTHOR]

Surface oxidation of the oriented silicon steel usually occurs during the first soaking in annular furnace. It negatively influences the magnetic performance and the MgSO4 coating of the strip. The surface oxidation is closely related to the high H2O content atmosphere between the layers of the strip. As the H2O content within the coil is hard to measure, the mass transfer model of the oriented silicon steel coil during the first soaking in annular furnace is built in this paper. Furthermore the correlations between H2O content and the magnetic performance distribution are also analyzed via experiment in actual production. The result shows that the H2O content within the coil increased as the height declined in axial direction. Plenty of H2O concentrated near the bottom of the coil as a result of the tight joint between the coil and the plate. The maximum H2O content within the coil is about 80 vol%. The magnetic performance of the strip tended to decline while the H2O content rose especially at the edge of the strip. Most magnetic property defects appeared at the outer ring and the bottom of the coil. The oxidizing atmosphere between the layers of the strip could be weakened significantly through improving the diffusion conditions at the bottom surface of the coil. [ABSTRACT FROM AUTHOR]

In fire investigations, the most important aspect is determining the presence of a liquid accelerant at the fire scene. The presence or absence of accelerants is critical evidence during trials for fire cases. Upon exposure to high temperatures, metallic substances undergo oxidation, which can be imparted by accelerants in the fire. Oxides and substrates found on metal surfaces offer valuable information on the characteristics of fire, including exposure temperature, duration, and involvement of a liquid accelerant. In this study, we investigated the oxidation behavior of copper at high temperatures in a simulated flame environment using ethanol combustion. After oxidation, the morphological, oxide phase composition, and microstructural features of specimens were characterized by observation, X-ray diffraction, X-ray photoelectron energy spectroscopy, transmission electron microscopy, and scanning electron microscopy with energy-dispersive spectroscopic analysis. The elemental carbon with a hexagonal structure deposited on the sample’s surface was found, which may be incomplete combustion and the chemical composition of ethanol. Copper has a preferred orientation of oxide on the (111) crystal plane, which differs from oxidation in ordinary hot air that is related to the large Coulomb force of the (111) crystal plane. Hot air convection due to combustion may cause large areas of oxide layer on the copper surface to crack and peel. Oxide properties and surface state of metals strongly depended on oxidation duration, temperature, and atmosphere. These data shall offer reference information for determining the presence of combustion accelerants at fire scenes.

Anti-oxidation properties of Cr substitution were investigated by comparing TiFe and TiFe 0.9 Cr 0.1. Kinetic measurements reveal that the degradation rate of TiFe 0.9 Cr 0.1 is slower than that of TiFe, indicating that Cr substitution drastically enhances the anti-oxidation properties of the mother alloy TiFe. In order to understand the mechanism of this effect, X-ray photoelectron spectroscopy (XPS) was used to identify the surface chemical state of these alloys, which indicates that Cr plays quite an important role in the suppression of surface oxidation. It is clarified that the deactivation of TiFe is caused by the oxidation of Ti on the surface and, as a result, the obstruction of hydrogen penetration. On the contrary, with the substitution of Cr for Fe in TiFe 0.9 Cr 0.1 , the Ti oxidation becomes more difficult even though the Cr was totally oxidized, which makes it easier to keep the initial activated state of hydrogenation (Ti with a low oxidation state). It also further demonstrated that Cr acts as a sacrificial element, undergoing complete oxidation to protect Ti from oxidation, and assists in keeping metallic Ti0, which is crucial for maintaining the hydrogen absorption kinetics. Therefore, the Cr substitution for Fe significantly improves the anti-oxidation properties of TiFe-based alloys. • Cr substitution improves the anti-oxidation properties of TiFe alloy. • The oxide layer composition changed when Fe was substituted by Cr in TiFe alloy. • Cr acted as a sacrificial element to prevent the oxidation of Ti. • Ti oxidation is the primary cause of the deactivation of TiFe alloy. [ABSTRACT FROM AUTHOR]