Superior Oxidation Resistance Research Articles

Highly stable carbon-coated nZVI composite Fe0@RF-C for efficient degradation of emerging contaminants

Nanoscale zerovalent iron (nZVI) has garnered significant attention as an efficient advanced oxidation activator, but its practical application is hindered by aggregation and oxidation. Coating nZVI with carbon can effectively addresses these issues. A simple and scalable production method for carbon-coated nZVI composite is highly desirable. The anti-oxidation and catalytic performance of carbon-coated nZVI composite merit in-depth research. In this study, a highly stable carbon-coated core-shell nZVI composite (Fe0@RF-C) was successfully prepared using a simple method combining phenolic resin embedding and carbothermal reduction. Fe0@RF-C was employed as a heterogeneous persulfate (PS) activator for degrading 2,4-dihydroxybenzophenone (BP-1), an emerging contaminant. Compared to commercial nZVI, Fe0@RF-C exhibited superior PS activation performance and oxidation resistance. Nearly 95% of BP-1 was removed within 10 min in the Fe0@RF-C/PS system. The carbon layer promotes the enrichment of BP-1 and accelerates its degradation through singlet oxygen oxidation and direct electron transfer processes. This study provides a straightforward approach for designing highly stable carbon-coated nZVI composite and elucidates the enhanced catalytic performance mechanism by carbon layers.

Tailoring oxidation resistance of Cantor alloy by addition of Ta and Al

High-entropy alloys are widely investigated for applications in the nuclear engineering field, the aerospace sector, and various other high-temperature applications. High-temperature oxidation behaviour is a typical issue in such applications. In the current work, an effort is made to tailor the oxidation behaviour of Cantor alloy (CoCrFeMnNi) in the air at 1000 °C with the addition of Ta and Al. Both CoCrFeMnNiTa as well as CoCrFeMnNiAl alloys exhibit considerable resistance to oxide scale spallation as well as develop multi-layered complex oxide scales. CoCrFeMnNiTa primarily forms rutile-type CrTaO4 oxide, which drastically reduces the inward diffusion of oxygen and nitrogen and suppresses the escape of other alloying elements. Nonetheless, the better result is obtained through the Al addition, as evidenced by the comparatively lower oxidation rate constant of CoCrFeMnNiAl in comparison to CoCrFeMnNiTa alloy. This is attributed to the superior oxidation resistance for CoCrFeMnNiAl could be related to the emergence of distinctive Cr2O3 and Al2O3 scales. Additionally, the oxide scale of CoCrFeMnNiTa was not completely smooth and showed some spallation whereas the oxide scales of CoCrFeMnNiAl remained smooth, continuous, and had stronger oxide-substrate interface adhesion.

Interlayer cross-linked MXene enables ultra-stable printed paper-based flexible sensor for real-time humidity monitoring

With an abundance of hydrophilic active sites present on the surfaces, MXene exhibits significant potential for application in the field of humidity monitoring. Nevertheless, achieving the high response intensity, excellent response sensitivity, structural stability, and oxidation resistance in the MXene-based humidity sensors remains a formidable challenge. Herein, we propose a humidity sensor made from the paper-based flexible sensor with copper electrode and polyethyleneimine/silver nitrate cross-linking modified MXene composite materials. The humidity sensor prepared in this work presents a satisfactory capacitance response rate (819.9 % in 97 % RH) and favorable sensitivity (6.9/11.9 s for response/recovery time). Meanwhile, the humidity sensor possesses outstanding structural stability (less than 3 % attenuation of the capacitance response after 100 bending cycles) and superior oxidation resistance. Moreover, the real-time humidity monitor assembled based on the humidity sensor has realized the effective monitoring of human skin humidity and dynamic respiration. Consequently, this study provides a viable approach for achieving reliable real-time humidity monitoring, demonstrating significant potential in the realms of intelligent actuators, sensing devices, and health care.

Surface morphology and oxidation products of DOP-26 iridium alloy upon high-temperature exposure to air

The DOP-26 Ir alloy is employed for fuel sealing in isotope batteries and exhibits superior oxidation resistance at high temperatures under low oxygen conditions. This study investigated the oxidation behavior of the DOP-26 Ir alloy in air, focusing on the correlation between the oxidation temperature and time. X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy were conducted to examine the phase, morphology, and valence of the alloy upon oxidation. The findings provide a comprehensive understanding of the high-temperature oxidation kinetics of DOP-26 Ir alloy in the air, and these results could potentially be applied to the design and application of radioisotope thermoelectric generators.

Microstructure evolution and oxidation resistance properties of oxide dispersion strengthened FeCrAl alloys at 1100 °C

Oxide dispersion strengthened (ODS) FeCrAl alloys were prepared by mechanical alloying (MA) and spark plasma sintering (SPS) technology. To reveal the high temperature oxidation properties, ODS FeCrAl alloys were exposed to dry air for various times (1h, 4h, 10h, 20h, 45h, 70h, and 100h) at 1100 °C to investigate the microstructure evolution. The results illustrated that a flat and adherent alumina scale was gradually thickened on the alloy substrate with the increase of the oxidation time. In particular, it was observed that large-size reactive element (RE) oxides were inclined to be associated with cavities close to the gas interface and these cavities were progressive evolution to be larger-size pores with longer exposure time, while tiny RE oxides were not dispersed with cavities after 100h oxidation. In addition, α-Al2O3 with a double-scale structure were mainly composed of inner columnar grains and outer equiaxed grains, as well, the growth of α-Al2O3 scales illustrated that the oxidation rate decreased with oxidation reaction proceeding. For one thing, Ti segregation along grain boundaries (GBs) near the gas interface decreased the outward diffusion of the Al ions to weaken the oxidation rate. Furthermore, the gradual coarsening of columnar grains near the alloy substrate implied a longer diffusion path of O atoms, thereby accounting for slower oxidation process. To sum up, ODS FeCrAl alloys with thinner oxide thickness demonstrated the superior oxidation resistance than other materials, which would make it one of the promising candidate structural materials applicated in accident-tolerant fuel (ATF) cladding materials.

First-principles calculation, synthesis, and oxidation mechanism of Ta1-xHfxC ultra-high temperature ceramics

According to first-principles calculations, the mechanical properties of Ta1-xHfxC (x = 0.2, 0.4, 0.5) improve as the Ta content increases due to enhanced bonding between Ta and C atoms. The negative mixing enthalpies indicate that all three solid solutions can be prepared as single-phase materials. Single-phase Ta1-xHfxC (x = 0.2,0.4,0.5) were prepared using Spark Plasma Sintering. Studies on oxidation reveal that Ta0.5Hf0.5C demonstrates the most superior oxidation resistance among the three compositions. During oxidation, forming a Ta2O5-Hf6Ta2O17 layer is essential for improving oxidation resistance. The research indicates that balancing the ratio of Ta and Hf is crucial for achieving optimal mechanical properties and oxidation resistance in practical applications.

A novel high-Cr CoNi-based superalloy with superior high-temperature microstructural stability, oxidation resistance and mechanical properties

A novel high-Cr CoNi-based superalloy with superior high-temperature microstructural stability, oxidation resistance and mechanical properties

Probing optoelectronic and thermoelectric properties of double perovskite halides Li2CuInY6 (Y = Cl, Br, I) for energy conversion applications

Recently, double perovskite halides (DPHs) become crucial due to their potential applications in optoelectronic devices due to their stability, non-toxicity, superior oxidation resistance, high conversion efficiency, and high temperature stability. In the current study, we explored DPHs Li2CuInY6 (Y = Cl, Br, I) employing Wien2k package to analyze the structural stability, optoelectronic and thermoelectric features. The formation energy and Born stability criteria are computed to confirm thermodynamic and structural stability. Studied DPHs have direct bandgaps nature investigated by modified Becke and Johnson (mBJ) potential. Calculated values of bandgap decreases, when replace halide ion from Cl to I, indicate tuning from visible to infrared (IR) region of electromagnetic spectrum. Their band edge tuning across the visible to infrared border is reliant on replacement, which makes them suitable for projects involving opto-electronic devices. Further, optical features are investigated in terms of incident photon energy in order to assess the optical output. Lastly, electronic thermoelectric performance is computed using the figure of merit (ZT) for all DPs. Computed results of direct bandgap and optical behavior show that DP Li2CuInCl6 can be used as photovoltaic devices as compared to DPs Li2CuInBr6 and Li2CuInI6.

Effect of Laser Scan Speed on Defects and Texture Development of Pure Chromium Metal Fabricated via Powder Bed Fusion-Laser Beam.

Chromium (Cr) metal has garnered significant attention in alloy systems owing to its exceptional properties, such as a high melting point, low density, and superior oxidation and corrosion resistance. However, its processing capabilities are hindered by its high ductile-brittle transition temperature (DBTT). Recently, powder bed fusion-laser beam for metals (PBF-LB/M) has emerged as a promising technique, offering the fabrication of net shapes and precise control over crystallographic texture. Nevertheless, research investigating the mechanism underlying crystallographic texture development in pure Cr via PBF-LB/M still needs to be conducted. This study explored the impact of scan speed on relative density and crystallographic texture. At the optimal scan speed, an increase in grain size attributed to epitaxial growth was observed, resulting in the formation of a <100> cubic texture. Consequently, a reduction in high-angle grain boundaries (HAGB) was achieved, suppressing defects such as cracks and enhancing relative density up to 98.1%. Furthermore, with increasing densification, Vickers hardness also exhibited a corresponding increase. These findings underscore the efficacy of PBF-LB/M for processing metals with high DBTT properties.

The effect of nitrogen on the isothermal oxidation of substoichiometric zirconium carbide: Microstructural and spectroscopic investigations

The oxidation behavior of hot-pressed sub-stoichiometric zirconium carbide was investigated through isothermal flow-tube furnace experiments at temperatures ranging from 1000 to 1600 °C. Auxiliary gas composition influence on the oxidation of ZrC0.63 was studied by introducing oxygen to substrates held under either pure argon or nitrogen environments. During furnace ramp-up, prior to isothermal oxygen exposure, nitrogen flow was found to infiltrate the substrate resulting in ZrCxNy formation which provided superior oxidation resistance to the as-received ZrC0.63. Ex situ investigation of ceramic-oxide interfacial regions revealed the presence of carbon precipitate in both material sets at treatment temperatures of up to 1400 °C, along with the presence of the ZrCxOy system. At sufficiently high test temperatures, resulting scale formations for the N2/O2 systems were found to be less porous than the Ar/O2 counterparts, with a higher degree of c-/t-ZrO2 crystallites present at room temperature attributed to nitrogen incorporation into the anion sublattice of ZrO2.

Superior oxidation resistance of a Y-Hf co-doped Al18Co30Cr10Fe10Ni32 eutectic high-entropy alloy at 1100–1300 °C

We report a study on the oxidation behavior of Al18Co30Cr10Fe10Ni32 eutectic high-entropy alloy co-doped with reactive elements (RE) Y and Hf at 1100–1300 °C. The highly stable eutectic microstructure of γ’/β phases within this alloy contributes to a low coefficient of thermal expansion, thus a low residual stress in the Al2O3 scale. The spinel with a low thickness is formed at the top of Al2O3 scale at 1100 °C due to the low Al diffusion coefficient of γ’-phase and low aspect ratio of β-phase in maze-like eutectic region. As the oxidation temperature increases, the oxidation products transition to exclusive Al2O3 at 1200 °C and 1300 °C, facilitated by the increased Al diffusion coefficient. The Al2O3 scale exhibits a dominated columnar grain microstructure at 1100–1300 °C, suggesting that the inward O diffusion plays more critical role than Al diffusion and thus leads to the low oxidation rate. Besides, the segregation of S to scale/metal interface is inhibited by the uniform RE distribution in the alloy resulting from the fine eutectic microstructure in the alloy. Overall, this alloy exhibits low residual stress in the oxide scale, slow oxidation rate, and the lack of interfacial sulfur segregation, thus contributing to its superior oxidation resistance. The strong oxidation resistance of Y-Hf co-doped Al18Co30Cr10Fe10Ni32 eutectic high-entropy alloy makes it a potential candidate for advanced oxidation-resistant alloy or coating applications.

Vertically interconnected structure enhances the thermal management capability of copper-based composites

Efficient thermal management relies on constructing a network structure. Here, we propose an efficient strategy for fabricating an in-plane vertically interconnected network by integrating copper nanoparticles and nanowires through electrospinning and vertically stacking hot-pressing. This approach offers a dual benefit: creating an in-plane vertically interconnected thermal conductive network while simultaneously protecting the fillers against oxidation. Furthermore, the combination of multi-dimensional hybrid fillers reduces interfacial thermal resistance. Thus, the (Cu NPs-Cu NWs)@PVP/PVA film with hybrid fillers achieves a high thermal conductivity of 22.71 Wm-1K-1, along with superior thermal stability, oxidation resistance, and flexibility, making it promising for advanced electronic device thermal management.

Effect of Fe doped Co–Ni protective coatings on the oxidation behavior and electrical properties of SOFC alloy interconnect materials

In order to enhance the oxidation resistance and electrical properties of interconnects for solid oxide fuel cells (SOFCs), three Co–Ni alloy coatings with varying contents of Fe doping were prepared onto SUS 430 substrate using electroplating method and oxidized in air at 800 °C for 1000 h. The experimental results demonstrated that the alloy coating significantly enhanced both the oxidation resistance and electrical properties of the interconnect substrate. The multi-layer oxidation structure blocked Cr from diffusing outward. Notably, the (Co,Fe)3O4/(Ni,Co)O in the oxidized layer of 5% Fe doped Co–Ni coated steel completely transformed into (Fe,Co,Ni)3O4 spinel layer after long term oxidation, which had the lowest activation energy and the strongest ability of restricting oxygen diffusion inward. Thus, the 5% Fe doped Co–Ni coated steel showed superior oxidation resistance (kp = 8.76 × 10−14 g2 cm−4 s−1) and excellent electrical properties (ASR = 13.19 mΩ cm2) following oxidation for 1000 h.

Effect of Pt on Stress Rupture Properties of Pt-Modified Nickel Aluminide Coatings at 1100 °C.

Platinum plays a crucial role in the superior high-temperature oxidation resistance of Pt-modified nickel aluminide (PtAl) coatings. However, PtAl coatings usually serve in thermo-mechanical coupling environments. To investigate whether Pt contributes to the high-temperature mechanical properties of PtAl coating, stress rupture tests under 1100 °C/100 MPa were performed on PtAl coatings with varying Pt contents. The different coatings were obtained by changing the thickness of the electroplated Pt layer, followed by a diffusion heat treatment and the aluminizing process in the present work. The results of the stress rupture tests indicated that an increasing Pt content resulted in a significant decrease in the stress rupture life of PtAl-coated superalloys under 1100 °C/100 MPa. Theoretical calculations and microstructural analysis suggested that an increased coating thickness due to the Pt content is not the main reason for this decline. It was found that the cracks generated close to the substrate in high-Pt-coated superalloys accelerated the fracture failure.

High-purity rayon-based carbon fiber felt prepared by halogen gas purification for superior thermal insulation and oxidation resistance

High-purity rayon-based carbon fiber (CFRay) felt holds significant promise for applications in thermal protection systems and semiconductor crystal growth furnaces. This study employs halogen gas purification and high-temperature purification techniques in the fabrication of high-purity CFRay felt. Additionally, the influence of the purification process on the thermal insulation and oxidation resistance of CFRay felt is investigated. The glow discharge mass spectrometer analysis reveals that purification at a lower temperature of 2300 °C achieves a purity level of 6.9 ppm, surpassing both purified CFRay felt without halogen at 2300 °C (56.1 ppm) and high-temperature treated CFRay felt at 3000 °C (10.4 ppm). Thermal insulation and dynamic-static oxidation resistance tests show that the properties of CFRay felt are concurrently affected by the heat treatment temperature. Compared to high-temperature purification, halogen gas purification operates at lower temperatures, preventing the graphitization of CFRay, thereby ensuring high purity while enhancing thermal insulation and demonstrating relatively superior oxidation resistance. This study offers novel insights into the preparation and performance adjustment of high-purity CFRay felt.

Revealing the superior oxidation resistance of alloy 690 in deaerated supercritical water at 600 °C through advanced characterization

The corrosion behavior of a well-polished Alloy 690 in deaerated supercritical water at 600 °C was examined. The study found that the weight gain follows a near-cubic rate law. A key observation was that the direct external oxidation and the rapid transition from internal to external oxidation within the initial 24-h exposure are responsible for its superior oxidation resistance. As exposure time increases, the transformation of Cr-rich spinel oxides and Ni-rich networks in the internal oxidation zone into Cr2O3 leads to the expansion of the protective chromia layer, effectively slowing down the oxidation process. Conversely, the Cr2O3 layer at the grain boundaries (GBs) was less effective at preventing oxidation, resulting in a significantly faster oxidation rate in these areas compared to the bulk grains. The extensive GB oxidation exhibits little consequential correlation with carbides.

Oxidation behavior of AlCoCrFeNi bond coating in the YSZ-TBCs produced by APS and PS-PVD method

This study prepared the 7YSZ ceramic coatings based on AlCoCrFeNi bond coating by APS and PS-PVD methods, respectively. Two AlCoCrFeNi/7YSZ thermal barrier coating systems with different microstructures of ceramic coatings were obtained, and oxidation experiments at 1000 °C and 1100 °C were carried out for the two thermal barrier coating systems. The results showed that the AlCoCrFeNi/7YSZ(PS-PVD) thermal barrier coating system exhibits superior oxidation resistance compared to the AlCoCrFeNi/7YSZ(APS) thermal barrier coating system at 1000 °C and 1100 °C, which was attributed to the ceramic coating with a unique feather-columnar structure prepared by PS-PVD. Both thermal barrier coatings in this study produced a continuous and dense TGO layer composed of Al2O3 after oxidation experiments. The oxidation rate constants kp of this study's two thermal barrier coatings were lower than the selected MCrAlY/YSZ thermal barrier coating systems under the same experimental conditions. It indicates that the AlCoCrFeNi bond coating exhibited excellent oxidation resistance and possesses the potential to be a new type of bond coating material.

Microstructures and Antioxidation of W Self-Passivating Alloys: Synergistic Effect of Yttrium and Milling Time

Tungsten and its alloys are widely recognized as key components in high-temperature environments. In this study, self-passivating W-Si-xY alloys with varying Y content were prepared using mechanical alloying (MA) and spark plasma sintering (SPS). The synergistic effects of Y content and milling time on the microstructures and oxidation resistance of the alloys were revealed. This study found that the oxidation resistance of the alloys increased as the Y content increased. However, the effect of milling time on oxidation resistance was complex. For W-Si-xY alloys with low Y content (0Y and 2Y), the oxidation resistance decreased with increasing milling time. In contrast, for W-Si-xY alloys with high Y content (4Y and 6Y), the oxidation resistance increased with increasing milling time. This enhanced oxidation resistance is due to the microstructural changes in the protective composite layer, including the size and distribution of W5Si3, Y2Si2O7 aggregates, and W-Y-O melt. The thickness of the oxide layer on the W-Si-6Y alloy after being oxidized at 1000 °C for 2 h was only 70.7 μm, demonstrating its superior oxidation resistance.

Ultrafast synthesis of high-entropy carbides up to 3,273 K for superior oxidation resistance

Ultrafast synthesis of high-entropy carbides up to 3,273 K for superior oxidation resistance

Improved oxidation resistance while maintaining slag corrosion resistance of MgO–SiC–C refractories with moderate amounts of liquid phase

AbstractMgO–SiC–C refractories with superior hot strength, oxidation resistance and slag resistance have potential to become substitute refractories for matte smelting furnace. In the present work, the influence of glass powder addition on phase compositions, hot strength, oxidation resistance, and slag resistance of MgO–SiC–C refractories was investigated. The liquid phase introduced by glass powder filled the pores, blocking the channel for the ingress of the oxygen and thus improving the oxidation resistance. Although the oxidation resistance of such refractories was improved with 1–3 wt% glass powder addition, their hot strength and slag corrosion resistance decreased when the glass powder content was 2–3 wt%. To balance the mechanical properties, oxidation resistance and slag resistance, low amount glass powder addition (1 wt%) was considered better choice.