Oxidation Time Research Articles

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.

Effect of anodizing pretreatment on laser joining stainless steel to CFRTP

Metal-carbon fiber reinforced thermoplastic (CFRTP) hybrid joints have demonstrated its effectiveness in achieving lightweight design concept in engineering application. However, it is difficult to produce high-reliability joint due to differences in physical as well as chemical properties between metal and CFRTP. In this study, porous oxide film was prepared by anodizing treatments with various anodic oxidation times on steel surface to enhance joint performance of laser-welded steel/CFRTP. The maximum steel/CFRTP joint fracture load of 1960 N was reached, which was three times as much as that obtained with pretreated steel. The results indicated that porous structure was introduced into steel surface by anodization process, which resulted in better wettability of molten CFRTP and higher surface roughness, thus contributing to the enhancement of joint area as well as mechanical interlocking at the interface, further improving joint performance. Meanwhile, more Cr-O-C chemical bonds were produced because Cr-rich oxide film formed after anodizing contributed to interfacial chemical reaction. The chemical bond between oxide film and CFRTP was proved through density functional theory (DFT) calculation. Additionally, with the increase of anodic oxidation time, chemical bond content and surface roughness first enhanced and then reduced, which suggested that the porous structure prepared with 20 min anodizing time could best improve the interfacial mechanical interlocking, and promote the chemical bonding as well as steel/CFRTP joint interfacial bonding.

Influence of Furnace Pressure on the Growth Characteristic of Oxide Film on Piercing Plug Steel

Different oxidation processes are carried out by using 20Cr2Ni4 piercing plug steel to study the influence of furnace pressure on the growth characteristic of oxide film in high‐temperature C2H5OH–H2O atmosphere. The results show that oxide film under different processes shows clearly two layers. The inner film is porous with the main constituents of FeO and Fe3O4 while the outer film is dense with large bubbles. The elemental Ni aggregates as a dot‐like substance in the inner oxide, where the enrichment of Cr lags behind the frontier boundary of Ni distribution. It is found that the thickness of the oxide film shows a parabolic relationship with product of the square root of oxidation time and furnace pressure. High furnace pressure can keep the pressure balance of the bubbles to swell to sufficient size, but may cause cracking during the relief process of pressure.

Composite materials based on thermoplastic elastomers modified with maleinated polypropylene

The results of modification of a composite material based on a filled styrenic thermoplastic elastomer with maleinized polypropylene are presented. The dependence of strength, technological and operational properties of mixed compositions on temperature is shown. The results on the oxidative induction time of the developed compositions were obtained, which allowed us to conclude about the compatibilizing effect of maleinized polypropylene.

Novel sunlight-induced monochloramine activation system for efficient microcontaminant abatement

As an eco-friendly and sustainable energy, solar energy has great application potential in water treatment. Herein, simulated sunlight was for the first time utilized to activate monochloramine for the degradation of environmental organic microcontaminants. Various microcontaminants could be efficiently degraded in the simulated sunlight/monochloramine system. The average innate quantum yield of monochloramine over the wavelength range of simulated sunlight was determined to be 0.068 mol/Einstein. With the determined quantum yield, a kinetic model was established. Based on the good agreement between the simulated and measured photolysis and radical contributions to the degradation of ibuprofen and carbamazepine, the major mechanism of monochloramine activation by simulated sunlight was proposed. Chlorine radical (Cl∙) and hydroxyl radical (HO∙) were major radicals responsible for microcontaminant degradation in the system. Moreover, the model facilitated a deep investigation into the effects of different reaction conditions (pH, monochloramine concentration, and water matrix components) on the degradation of ibuprofen and carbamazepine, as well as the roles of the involved radicals. The differences between simulated and measured degradation data of each microcontaminant under all conditions were less than 10 %, indicating the strong reliability of the model. The model could also make good prediction for microcontaminant degradation in the natural sunlight/monochloramine system. Furthermore, the formation of disinfection byproducts (DBPs) was evaluated at different oxidation time in simulated sunlight/monochloramine with and without post-chloramination treatment. In real waters, organic components showed more pronounced suppression on microcontaminant degradation efficiency than inorganic ions. This study provided a systematic investigation into the novel sunlight-induced monochloramine activation system for efficient microcontaminant degradation, and demonstrated the potential of the system in practical applications.

Initial damage behavior of Al2O3‐modified SiCf/SiC–B4C composites after oxidation under wet atmosphere at 1200°C

AbstractAl2O3 was incorporated into SiCf/SiC–B4C composites to improve their mechanical properties after oxidation. The results showed that Al2O3 reduced the weight gain of these composites, and the oxidized layer became smooth and dense. The fibers pull‐out lengths of the Al2O3‐modified composites were longer than that of virgin composites oxidized for the same amount of time. Compared with the virgin composites, the tensile strength retention rate of Al2O3‐modified composites was improved by 7.3% and 8.4% after oxidation times of 50 and 100 h, respectively. But Al2O3 modification led to 20.6% and 44.3% improvements in σonset (acoustic emission, AE onset stress) as well as 76.5% and 95.5% the improvements in σmin (first AE stress), respectively. Further investigation indicated that a higher proportion of high‐energy level events occurred in the Al2O3‐modified composites when the load just reached the damage thresholds stress compared with the virgin composites.

Long-term oxidation of Ti3Al0.8Sn0.2C2 in air at 1200 °C

The addition of Sn into the raw materials is currently one of the most widely used methods to improve the purity and mechanical properties of Ti3AlC2. It follows in this work to investigate the oxidation behavior of the resulting Ti3Al0.8Sn0.2C2 at 1200 °C with the oxidation time up to 500 h. The oxidation kinetics shows that its oxidation resistance is much worse than that of common MAX phases including Ti3AlC2, Ti2AlC, and Cr2AlC. The oxide layer mainly consists of TiO2 and Al2O3, with only a small amount of SnO2 at the beginning of the oxidation stage. Cracks induced by the internal thermal stress penetrate through the entire oxide layer after only 1 h, which is an important reason for the rapid oxidation of the internal substrate layer. This work is expected to provide some inspiration and reference for Ti3Al0.8Sn0.2C2 used as the potential high-temperature structural material.

Oxidation and mechanical properties of SiC fibers after high temperature exposure in air and steam

SiC fibers are widely used in composites exposed to high temperature oxidizing environments. The present study compares the oxidation behavior of SiC fibers and the associated changes in tensile strength upon their exposure to dry air and steam for up to 50 hours at temperatures from 950°C to 1350°C. In both cases, the scale thickness and oxide microstructure were analyzed by scanning electron microscopy. When the SiC fibers were oxidized in air, a crack-free amorphous oxide layer formed at temperatures up to 1200°C, whereas a cracked, crystallized oxide layer was found at 1350°C. By contrast under steam environment, a crystalline oxide forms at 950°C for oxidation times longer than 30 h. In both environments, the fiber strength decreased with increasing exposure time and temperature, the degradation being faster after oxidation in steam compared to dry air. This appears to relate to residual stress in the oxide scale and a reduction in the cross section of the load-bearing unoxidized SiC. An increase in defect size may also contribute to the loss of strength. The oxide scale follows parabolic growth kinetics in both dry air and in steam from 950°C to 1350°C, except at 1350°C for over 30 hours. The oxidation rate in steam is faster than that in dry air, with activation energies of 79.8±1.4 kJ/mol in steam and 153.6±3.4 kJ/mol in dry air, respectively. This work is relevant to the application of SiC fibers and SiC fiber reinforced composites in air and steam environments at high temperature.

Ultrabroad electromagnetic absorbing core-shell SiC@SiO2 nanocomposites derived from in situ oxidation SiC whiskers

The amazing developing electromagnetic technology has brought severe challenges to the military and civilian fields, efficient electromagnetic wave absorption (EWA) materials with high-temperature resistance are urgent needed. In this paper, SiC@SiO2 nanocomposites with unique core-shell structures were successfully prepared using a straightforward method by in situ oxidation SiC whiskers. By regulating the sintering temperature and oxidation time, the microstructures and EWA performance of SiC@SiO2 nanocomposites were explored. The results show that the core-shell SiC@SiO2 nanocomposites obtained after sintering at 1200 ℃ for 0.5 h exhibits the best EWA performance, where the minimum reflection loss (RLmin) of −36.80 dB at the thickness of 2.68 mm and the effective absorption bandwidth (RL<-10 dB, EAB) of 9.85 GHz at a matching thickness of 4.24 mm. Specially, the EAB can reach up 10.98 GHz with the filling content of only 10%, which surpasses most SiC-based absorbers. The ultrabroad absorbing bandwidth can be attributed to that the unique core-shell structures of SiC whiskers with in-situ grown SiO2 layers on the surface provide good impedance matching, multiple reflection and scattering and interface polarization effects. This work provides a new strategy for the design of high temperature resistant absorbing materials.

Reflood oxidation performances of Cr-coated Zr-Sn-Nb alloy cladding tubes at 1000 °C∼1200 °C

Reflood plays an important role in preventing the serious accident process. In this paper, the reflood oxidation performances of Cr-coated Zr-Sn-Nb alloy cladding tubes at 1000 °C, 1100 °C and 1200 °C were studied by high-temperature steam oxidation followed by in-situ water quenching. The oxidation kinetics, macroscopic morphology, phase transformation and microstructural evolution were investigated. Cr coating can provide excellent anti-reflood oxidation protection for Zr-Sn-Nb alloy, resulting in an oxidation rate constant of only 1/4–1/7 of that of uncoated Zr-Sn-Nb alloys. However, the cladding tube degraded into fragments due to excessive thermal stress during the in-situ water quenching after reflood oxidation at 1200 °C for 4000 s. After reflood oxidation at 1000 °C and 1100 °C, the most prominent feature of the surface is a porous flocculation structure main due to the formation of volatile products, while after 1200 °C, it is a fine mackerel scale-like structure accompanied by protruding whiskers main owing to Cr3+ rapidly migrates outward to the outer surface via short circuit paths. After oxidation, the cross-section of Cr-coated Zr-Sn-Nb alloys exhibits a multi-layer structure. The thickness of each layer changes approximately linearly with oxidation time. However, due to the redox reaction, compared to that after oxidation for 2000s, the Cr2O3 layer becomes thinner and the residual Cr coating becomes thicker after oxidation at 1200 °C for 4000 s.

Chemically tailored graphite oxide nanoparticles for improving material properties of canola protein-based films

Canola protein obtained from canola meal, a byproduct of the canola industry, is an economical biopolymer with promising film-forming properties. It has significant potential for use as a food packaging material, though it possesses some functional limitations that need improvement. Incorporating nanomaterials is an option to enhance functional properties. This study aims to produce canola protein films by integrating GO exfoliated at several oxidation times and weight ratios to optimize mechanical, thermal, and barrier properties. Oxidation alters the C/O ratio and adds functional groups that bond with the amino/carboxyl groups of protein, enhancing the film properties. Significant improvement was obtained in GO at 60 and 120 min oxidation time and 3% addition level. Tensile strength and elastic modulus increased 200% and 481.72%, respectively, compared to control. Control films showed a 37.57 × 10−3 cm3m/m2/day/Pa oxygen permeability, and it was significantly reduced to 5.65 × 10−3 cm3m/m2/day/Pa representing a 665% reduction.

An integrated experimental and analytical approach on mechanical characterization of advanced powder metallurgy aluminium metal matrix composites reinforced with different particulates

Over the last few decades, ‘Discontinuously Reinforced Particulate Composites (DRPCs)’ are a popular class of composite materials with considerable challenge in processing, characterization and machinability because of their increased strength-weight ratio, stiffness, specific strength and oxidization when compared to various metals and their alloys. This paper discusses experimental and numerical investigation on mechanical characteristics of aluminum metal matrix reinforced with various reinforcement particulates such as silicon carbide, aluminium oxide, and zirconium oxide, compaction pressure (kN) and hold time (s) based on Design of Experiments (DOE) and Finite Element Analysis. Initially this paper discusses the process optimization of Aluminum Matrix reinforced with different particulates experimentally to identify the favourable processing conditions by varying reinforcement materials, compaction pressure (kN) and hold time (s) based on TDOE (Taguchi’s Design of Experiments). Further, this paper concentrates to determine ‘maximum principal stress, equivalent elastic strain and equivalent (von-mises) stress’ based on Finite Element Analysis (ANSYS Workbench-2023R1). The results of the experimentation showed that the highest hardness values were achieved with ZrO2 reinforcement material. Increasing the compaction pressure from 8 to 12 kN resulted in a slight decrease in surface roughness and porosity. Higher compaction pressures have assumed to facilitate better particle distribution and improved interfacial bonding, leading to smoother surfaces and lower void content. The simulation results showed that the maximum principal stress achieved were (2235.8 MPa) SiC, (3444.4 MPa) Al2O3, and (3582.5 MPa) ZrO2. The equivalent elastic strain achieved was (0.2488) SiC, (0.2421) Al2O3 and (0.262) ZrO2. The equivalent (Von Mises) stress achieved was (28751 MPa) for SiC, (24880 MPa) for ZrO2 and (26972 MPa) for Al2O3. This experimentation and simulation demonstrated that the PM process can be used to fabricate DRAMMC with different reinforcement particulates. The understanding gained experimentally and analytically from this research can be applied for future processing of Aluminum Matrix Reinforced with different particulates.

Effect of shell-dependent variation on the photocatalytic activity of flower-like core-shell SnSe@SnO2

Flower-like core-shell SnSe@SnO2 was prepared by low-temperature in situ oxidation. The relationship between different oxidation times and the formation of core-shell structures of the samples was explored. The results showed that SnSe was obtained by thermal oxidation of SnO2 in close contact with air. The size range of the flower-like core-shell structure SnSe@SnO2 was 15–20 μm. The flower-like structure was self-assembled from nanoplates with a thickness of about 200 nm. This flower-like core-shell structured SnSe@SnO2 has a band gap of about ∼1.4 eV. The electrochemical characterization of the samples was analyzed for charge transfer phenomena at the junctions as well as at the interface between the shell layer and the aqueous solution. The effect of different SnO2 shell layers on the photocatalytic degradation activity of the composites for methylene blue was evaluated. The samples with SnSe oxidized in air for 8 h showed optimal photocatalytic performance and displayed excellent photostability and reusability. In addition, O2− was the main active species for the degradation of the organic dye methylene blue.

Direct laser patterning of ruthenium below the optical diffraction limit

We describe a method that can be used to produce ruthenium/ruthenium oxide patterns starting from a ruthenium thin film. The method is based on highly localized oxidation of a small surface area of a ruthenium film by means of exposure to a pulsed laser under ambient conditions. Laser exposure is followed by dissolution of the un-exposed ruthenium in a NaClO solution, which leaves the conductive, partially oxidized ruthenium area on the substrate. Spatially selective oxidation, material removal, and, by implication, patterning, are, therefore, achieved without the need for a photoresist layer. Varying the exposure laser parameters, such as fluence, focus diameter, and repetition rate, allows us to optimize the process. In particular, it enables us to obtain circular Ru/RuO2 islands with a sub-diffraction-limited diameter of about 500 nm, for laser exposure times as short as 50 ms. The capability to obtain such small islands suggests that heat-diffusion is not a limiting factor to pattern Ru by laser heating on a (sub-)micron scale. In fact, heat diffusion helps in that it limits the area where a sufficiently high temperature is reached and maintained for a sufficiently long time for oxidation to occur. Our method provides an easy way to produce metallic Ru/RuO2 (sub-)micron structures and has possible applications in semiconductor manufacturing.

Microstructure evolution and failure mechanism of Cr-coated Zry-4 in air and steam at 1200 °C

The dense and uniform Cr coating is successfully applied to the Zry-4 (zircaloy-4) substrate using multi-arc ion plating as an accident-tolerant fuel cladding. The isothermal oxidation behavior of the Cr-coated Zry-4 is investigated in air and steam at 1200 °C. The mass gain, microstructure evolution and phase composition of the Cr-coated Zry-4 after different oxidation times are compared. The mass gain of Cr-coated Zry-4 in air is higher than in steam. In air, the dense Cr2O3 layer consisted of bulk Cr2O3, while protruding flake Cr2O3 is found on the surface of the Cr coating in steam. The degradation process and oxidation failure mechanism of the Cr-coated Zry-4 in air and steam at 1200 °C are analyzed.

Microstructure evolution during oxidation of quinary Ti3(AlSiSn)C2 at high temperatures and induced probable performance

Quinary Ti3Al0.6Si0.2Sn0.2C2 and Ti3Al0.5Si0.4Sn0.1C2 solid solution bulks were synthesized via hot-pressing process. High temperature oxidation behaviors were then investigated over a temperature range of 800–1200 °C. The weight gain per surface area and oxidation layer thickness were measured to study the oxidation kinetics. The as-synthesized compounds with varying solid solution ingredients exhibited comparable oxidation kinetics which fitted a parabolic kinetic better with the oxidation duration of 0–20 h, while it appeared to get more complicated after prolonging the oxidation time. The microstructure evolution and phase compositions of the oxide scales during breakaway oxidation were characterized to illuminate the oxidation mechanism. The oxidation layers exhibited a multi-layer structure resulting from the disparities between the diffusion and migration energies of the multi-elements. Anticipated performance induced by high temperature oxidation was further explored through investigation on the crack self-healing and tribological optimization capacities. It was revealed that cracks could be filled by predominant TiO2 and Al2O3 with a high efficiency at 1000 °C during annealing in air. At 800 °C, Ti3Al0.6Si0.2Sn0.2C2 exhibited self-lubricating properties that was attributed to the formation of smoothing tribo-oxide films, as demonstrated by the increasing oxygen content of the friction surface during sliding.

Three-Dimensional Electrode-Enhanced Ozone Catalytic Oxidation for Thiamethoxam Wastewater Treatment: Performance, Kinetics, and Pathway

Thiamethoxam is a second-generation neonicotinoid pesticide that is used worldwide. In this study, a three-dimensional electrode-enhanced ozone catalytic oxidation system (3DE-GAC-O3) was constructed to pretreat thiamethoxam wastewater, with granular active carbon as the particle electrode. The effects of catalytic oxidation time, current density, ozone concentration, initial thiamethoxam concentration, pH, and particle electrode dosage on thiamethoxam degradation were investigated. A response surface method based on the Box–Behnken design was employed to optimize the 3DE-GAC-O3 process. The results revealed that the 3DE-GAC-O3 system exhibited higher efficiency compared with the 3D electrode method, ozone catalytic oxidation, or 2DE-O3. The optimal operating conditions included a particle electrode dosage, ozone concentration, current density, solution pH, catalytic oxidation time, and initial thiamethoxam concentration of 18 g/dm3, 12 g/h, 25 A/m2, 7, 300 min, and 500 mg/dm3, respectively. The corresponding chemical oxygen demand removal rate reached 93.86 ± 0.95%. Thiamethoxam degradation followed a second-order reaction kinetics equation, and the rate constant decreased with increasing the initial thiamethoxam concentration. Free-radical quenching experiments indicated that both O2∙− and ∙OH were present within the 3DE-GAC-O3 system, with ∙OH being the predominant species. A GC-MS analysis revealed the formation of several intermediate products, which were characterized based on the mass fragmentation pattern. Additionally, a probable degradation pathway for thiamethoxam was proposed. Therefore, 3DE-GAC-O3 is an efficient method for the pretreatment of thiamethoxam wastewater.

A ReaxFF molecular dynamics study of the micro-dynamic oxidation behavior of Ni-Al alloys

Revealing the oxide-formation process at the atomic scale is challenging but extremely important for explaining the oxidation mechanism of an alloy. In this study, the microscopic dynamic oxidation behavior of nickel-based high-temperature alloys was simulated using reactive-force-field molecular dynamics. Adsorption was found to first occur in the vicinity of the Al atoms, which detach more readily from the surface of the alloy than the Ni atoms, giving rise to an uneven oxide-film distribution, surface stresses, and high-stress areas in the vicinity of Al. Outer-oxide growth mainly occurs through the outward diffusion of Al atoms, while the bond-distribution data reveal that the oxide is an intermediate state and that longer oxidation times only result in the transfer of charge from Al to O. Ni atoms were found to survive jumping at high temperatures, while surface roughness increased leading to oxygen atoms that are more inclined to diffuse into the interior of the alloy.

High-temperature oxidation behavior of AlCoCrFeNi2.1 eutectic high-entropy alloy: Microstructure evolution and microhardness

In this work, the high-temperature oxidation behavior at 820 °C of an AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) prepared by vacuum induction melting was studied, while the evolution of microstructure and microhardness at different oxidation times (1 h, 3 h, 5 h, 10 h, 20 h, 30 h, and 50 h) were also investigated. The prepared AlCoCrFeNi2.1 EHEA shows a typical FCC/BCC bi-phase microstructure with Cr-rich precipitation phase. Compared to 304 stainless steels, the AlCrCoFeNi2.1 EHEA exhibits a better oxidation resistance, which is due to the continuous and dense Al2O3 generated during high-temperature oxidation process. The AlCoCrFeNi2.1 EHEA also has an excellent high-temperature structure stability, proved by that the phase composition and elemental composition of each phase remain almost unchanged with the increase in oxidation time. After high-temperature oxidation, the microhardness of AlCoCrFeNi2.1 EHEA decreases as expected, however, with the increase in oxidation time, the microhardness shows a noticeable increasing trend due to the solid solution strengthening of the σ phase and formation of the α-Cr phase.

Room Temperature Ultrafast Oxidative Desulfurization with Sodium Hypochlorite in the Presence of Silica-Supported Catalysts.

A series of silica-supported catalysts containing molybdenum, tungsten, and vanadium oxides as the active phase was investigated in the process of oxidative desulfurization with sodium hypochlorite. It was shown for the first time that catalysts containing vanadium oxide as the active phase are more stable under oxidation conditions with sodium hypochlorite and retain their effectiveness at increased dosages of the oxidant and at high initial sulfur contents. The catalysts were characterized in detail by a complex of methods: Fourier transform infrared, X-ray spectral fluorescence, transmission electron microscopy, scanning electron microscopy, and low-temperature nitrogen adsorption/desorption. Key factors affecting the oxidation of dibenzothiophene (DBT) were investigated: oxidant and catalyst amount, oxidation time, initial sulfur content, and acetonitrile amount. Under optimized conditions, the DBT conversion rate was 100% in 5 min at room temperature (25 °C), NaClO/S molar ratio 6:1, catalyst amount 2 wt %. In the real sample of the straight-run diesel fraction, the sulfur content was reduced from 10,100 to 3030 ppm. The V(10%)/SiO2 catalyst retains its activity for 5 oxidation-regeneration cycles.