Oxidation Tests Research Articles

Effect of cyclic oxidation temperature on compressive strength of Cu-based brake pad for high-speed train

The cyclic oxidation tests of Cu-based brake pads at temperatures of 25, 300, 400, 500, 550, 600, 650 and 700 °C were conducted to simulate the oxidation of the friction surface under different braking speeds. Furthermore, the effect of cyclic oxidation temperature on the compressive strength was investigated. The results show that the cyclic oxidation process of Cu-based brake pads can be divided into three stages: mild oxidation (≤400 °C), moderate oxidation (500–600 °C) and severe oxidation (≥650 °C). Mild oxidation results in the formation of spherical Cu2O particles. The surface is covered by Cu2O and Fe2O3 nanosheets for moderate oxidation. Severe oxidation is characterized by a continuous thick CuO film, Fe2O3 nanosheets, and eroded graphite particles. The compressive strength and toughness of Cu-based brake pads show a declining trend as the cyclic oxidation temperature rises. The compressive strength of the Cu-based brake pad after oxidized at 700 °C, recorded at 30.56 MPa, is considerably lower than that of the original samples, which was 132.2 MPa. This reduction in compressive strength is attributed to the embrittlement of the metallic matrix and the formation of pores from graphite oxidation.

Optimizing additive Y2O3 concentration for improving corrosion resistance of ceramic coatings formed by plasma electrolytic oxidation on Zr-4 alloy

Abstract The corrosion resistance of ceramic coatings developed by plasma electrolytic oxidation (PEO) can be improved by embedding particles. Optimizing the concentration of particles in the electrolyte is essential to obtain the best coating performance. This work aims to optimize the concentration of Y2O3 embedded in the PEO coatings on Zr-4 alloy to obtain the best corrosion resistance. Nanoparticles Y2O3 was suspended in the PEO electrolyte at a concentration of 2, 3 and 4 g l−1. The particles were successfully embedded in the PEO coating composed of ZrO2–SiO2. The electrochemical test in an aqueous solution and oxidation test at 600 °C revealed a consistent result that the best corrosion resistance was obtained in the coating formed in the 3 g l−1 Y2O3-containing electrolyte. At the corresponding optimum concentration, the coating contained high SiO2 and tetragonal (t) ZrO2 phase, which potentially formed a stable solid solution ZrO2–SiO2. The improved coating stability enhanced the corrosion resistance during both aqueous solution and high temperature exposure.

Characterization of Seven Species of Camellia Oil: Oil Content, Volatile Compounds, and Oxidative Stability.

In this study, we conducted tests on the seeds from four Taiwanese native Camellia species (C. japonica, C. furfuracea, C. laufoshanensis, and C. formosensis) and three commercialized species (C. oleifera, C. brevistyla, and C. sinensis) for comparison. We examined various aspects of these species, such as seed oil content, suitability for mechanical pressing, volatile components (edible flavor), and oil stability (suitability for cooking), to assess the feasibility of using these four native Taiwanese Camellia seeds as sources of edible oil. The results from solvent extraction tests and mechanical pressing experiments confirm that the seeds from C. furfuracea, C. japonica, and C. laufoshanensis have high oil contents, and their oils are suitable for extraction via the popular mechanical pressing method, with oil yields comparable to or higher than those of the commercialized Camellia species. The volatile components of the oils were collected using MonoTrap adsorbents and analyzed with a thermal desorption system coupled with gas chromatography-mass spectrometry (ATD-GC/MS), primarily consisting of alcohols, ketones, and aldehydes. The results of oxidative stability tests reveal that the seed oils from C. japonica, C. furfuracea, and C. laufoshanensis are higher than or equally stable to those from the commercialized Camellia species. After six months of storage, the stability of these three Camellia seed oils remained relatively high, demonstrating that the seed oils from C. japonica, C. furfuracea, and C. laufoshanensis can withstand high temperatures and can be easily preserved for future applications.

Growth of α-Al2O3 layer involving abnormal oxides in FeCrAl alloy tube fabricated by WEDM process and electrical insulating performance in fusion reactor blanket

The tubular specimens of FeCrAl alloy APMT (Fe-22Cr-5Al-3Mo) were fabricated by a wire electrical discharge machining (WEDM) process. The oxidation characteristics of the machined surface were investigated by means of the oxidation tests performed in air atmosphere at the temperatures of 1273 K and 1373 K up to 100 h. The abnormal oxides such as CuAl2O4 and ZnAl2O4 were grew on the recast layer which was locally remained on the machined surface even after the mechanical polishing procedure. The α-Al2O3 layer involving the abnormal oxides was formed on the machined surface in the oxidation treatment at 1273 K for 10 h. The apparent electrical conductivity of the layer involving the abnormal oxides was larger than that without the abnormal oxides. Thick Al-rich oxide layer was formed under the abnormal oxides when the oxidation treatment was performed at 1373 K. The apparent electrical conductivity of the oxide layer became lower due to the presence of the thick Al-rich oxide. This oxide layer formed at 1373 K could function as an electrical insulating layer to reduce the magnetohydrodynamic pressure drop in liquid breeder blanket systems of magnetic confinement fusion reactors.

Assessing the influence of welding-induced mechanics on oxidation and stress corrosion cracking in an Alloy 600-Alloy 152 M weldment under simulated PWR primary water

The impact of welding-induced mechanics on the oxidation and stress corrosion cracking (SCC) behavior of Alloy 600 in a pressurized water reactor (PWR) primary water was investigated using an Alloy 600-Alloy 152 M weldment. The microstructural analysis found a 0.05 mm-wide composition transition zone from welding. The Alloy 600 heat-affected zone (HAZ) grain size matches the Alloy 600 base (600B). Deformation hardening initially decreases and stabilizes from the fusion boundary (FB) to the 600B Comparing the microstructural characteristics of the specimen from the HAZ at about 0.5 mm from the FB with specimen 600B shows identical composition, but the former exhibits higher Vickers hardness (HV), kernel average misorientation (KAM), dislocation density, and residual stresses. Results from both short- and long-term oxidation tests indicate that the specimen from the HAZ exhibits a greater thickness of the inner oxide film, a higher number of local oxidation sites, and an increased maximum depth of intergranular (IG) oxidation compared to the 600B specimen. Multiple sets of SCC test results demonstrate that the crack growth rate (CGR) in the specimens from the HAZ is higher than that in the base, with the former showing longer IG cracks and a greater proportion of IG cracking.

Composition optimization of (Hf, Ta, Zr, Cr)C high‐entropy carbides for good oxidation resistance

AbstractOxidation resistance is crucial to the potential applications of high‐entropy carbides (HECs) at elevated temperatures. Here, we realize the exploration of (Hf, Ta, Zr, Cr)C high‐entropy carbides (HEC‐TM, TM = Hf, Zr, Ta, and Cr) with good oxidation resistance by optimizing their compositions. To be specific, 21 kinds of HEC‐xTM (x = 0–25 mol%) samples are fabricated by a high‐throughput ultrafast high‐temperature sintering technique, followed by oxidation testing at 1673 K for 30 min. Among all the HEC samples, the as‐fabricated HEC‐0Zr samples are proved to possess the best oxidation resistance with an oxidation depth of only 53 µm. Further study on isothermal oxidation kinetics demonstrates that the as‐fabricated HEC‐0Zr samples follow a linear oxidation law. The good oxidation resistance of the as‐fabricated HEC‐0Zr samples is believed to result from the (Ta, Me)2O5 phase with a low melting point, which can promote the densification of the oxide layer. This research opens up a new way for efficiently discovering new HECs for extreme applications.

Sustainable aviation fuel: Impact of alkene concentration on jet fuel thermal oxidative test (JFTOT)

AbstractOf the processes that are approved to produce synthetic kerosene for use in jet fuel, about half produce olefinic kerosene that is hydrotreated. The alkene concentration in synthetic kerosene is indirectly regulated through the thermal oxidative stability specification. Perceptions about the deleterious influence of alkenes on thermal oxidative stability suggest that olefinic kerosene must be deeply hydrogenated. The extent of olefin saturation required has economic implications. To evaluate what an acceptable alkene concentration in synthetic kerosene is, the impact of alkene concentration on the outcome of the jet fuel thermal oxidative stability test (JFTOT) performed at 325°C in accordance with the ASTM D3241 standard test method was experimentally evaluated. Model synthetic kerosene mixtures to which different concentrations of alkenes (1‐decene, α‐methylstyrene, indene) were added, as well as control samples were studied. In the concentration range investigated, up to 10 wt% 1‐decene, 5 wt% α‐methylstyrene, and 2 wt% indene did not lead to increased fouling in the JFTOT. Fouling passed through a minimum value with increasing alkene concentration and alkene concentration on its own was a poor predictor of thermal oxidative stability. Analysis of the kerosene collected after passing through the JFTOT found measurable changes in density and refractive index. Dissolved oxygen reacting during thermal oxidative stability testing was accounted for mostly in oxygen‐containing products in the kerosene boiling range, which indicated that the heavier products were mainly hydrocarbon in nature. In addition to initiation by autoxidation, the investigation also pointed to the existence of a second thermally initiated fouling pathway that does not require the presence of oxygen.

Evaluation of the Protective Effects of Vitamins E and D on Oxidative Stress and Inflammation Caused by Tamoxifen in the Renal Tissue of Female Wistar Rats

Background: Tamoxifen is an effective drug for breast cancer treatment and its side effects are the production of reactive oxygen species and kidney damage. As antioxidants, vitamins E and D may help decrease kidney dysfunction. Objectives: In the present study, the protective effects of vitamins E and D on renal toxicity caused by tamoxifen in female Wistar rats were investigated. Materials and Methods: Twenty-five adult female rats weighing 180-200 were randomly divided into five groups with 5 rats. Group C, T, TE, TD, and TED were treated with olive oil, tamoxifen, tamoxifen + vitamin E, tamoxifen +vitamin D, and tamoxifen + both vitamins for four weeks. ELISA Kits measured the oxidant and antioxidant tests and TNF-α in kidney tissue. The spectrophotometric method measured urea, uric acid, and creatinine in serum and urine. Results: Tamoxifen significantly decreased the weight of rats, GPx, CAT, SOD levels and increased TNF-α, urinary creatinine level and, serum uric acid, urea levels (P < 0.05). But, treatment with vitamin D and simultaneous administration of vitamins led to a significant decrease in the level of (TNF-α) compared to the tamoxifen group (p < 0.01). Also, the histopathology results showed that the simultaneous administration of vitamins has significantly resolved the damage caused by the use of tamoxifen. Conclusion: The present study's findings showed that using vitamins E and D prevents kidney damage through antioxidant and anti-inflammatory effects. In addition, using vitamins E and D probably showed stronger synergistic effects against kidney damage.

Corrosive behavior of copper canisters under air and aerobic groundwater at early stages of deep geological disposal

Copper oxidation at low temperatures below 140 °C and its effects on corrosive behavior in aerobic groundwater are investigated to estimate the intactness of canisters at early stages of disposal. The Cu coupon surface is covered by fine particles that form thin oxide layers after 30 d of oxidation; a thin Cu2O layer of thickness <100 nm is formed after oxidation at 40 °C; after oxidation at 140 °C, the Cu2O surface changes to a CuO layer of thickness <500 nm. The thickness of the Cu surface oxidized at 90 °C is between those of the surfaces oxidized at 40 and 140 °C. All Cu coupons exhibit similar current densities ranging from 0.77 to 1.87 μA cm−2, although the corrosion potential of the Cu coupon layered with Cu2O is higher than that of the others. Long-term oxidation tests for 406 d reveal no significant changes in the Cu surface at temperatures below 90 °C, indicating no significant change in the electrochemical behavior. The results of this study suggest that the storage of canisters at temperatures below 90 °C has no significant effect on the degradation of canister performance in long-term disposal.

Effect of reactive elements in MCrAlX bond coat for durability improvement of thermal barrier coatings

The effects of reactive elements (RE) in MCrAlX alloy (M: Metals, X: RE) as the bond coat for thermal barrier coatings durability were investigated by both experimental evaluation and density functional theory (DFT) calculations. Cyclic oxidation tests showed that the lifetime of the sample with Y, Hf, and Si as RE displayed approximately twice of the sample with Y only. Furthermore, the interface energies between oxide (α-Al2O3) and bond coat with various RE (Si, Sc, Ti, Y, Zr, Hf, La, and Ce) were calculated by DFT. DFT results indicate that Hf and Si doping effectively reduce the interface energy.

Macroscopic and microscopic element distribution in transition zones of GTAW Alloy 52M weld joint and its PWSCC growth behaviour

The microstructure and element distribution in the transition zone (TZ) of Alloy 52M buttering (52Mb) layer near the fusion boundary to the SA508III low alloy steel in a dissimilar metal weld joint with post-weld heat treatment (PWHT) is characterized. Two macroscopic TZs in the heat-affected zone have lower Cr and Ni contents than the bulk Alloy 52Mb. The first TZ near the fusion boundary has the lowest Cr and Ni compositions, accompanying the highest Fe content. Cr depletion and Ni enrichment along with slight Fe enrichment at the dendrite boundaries in the TZs, are more significant than those in the bulk Alloy 52Mb. The number and the maximum depth of local oxidation penetrations at the alloy-inner oxide interface based on the oxidation tests, the number and the maximum length of locally interdendritic cracks, as well as the average crack growth rate (CGR) in terms of the stress corrosion cracking (SCC) band based on the SCC tests in the first TZ are higher than those in the second TZ. The average SCC CGR is enhanced by macroscopic element dilution, while local oxidation penetration, as well as locally interdendritic SCC, are thought to be enhanced by both the macroscopic dilution of Cr in the TZs and the microscopic Cr depletion at dendrite boundaries.

Investigation into the Reduction of Palm Oil in Foods by Blended Vegetable Oils through Response Surface Methodology and Oxidative Stability Tests.

Recently, there has been a significant transition in the dietary preferences of consumers toward foods containing health-promoting compounds. In addition, as people's environmental awareness increases, they are increasingly looking for sustainable solutions. Palm oil, an oil used extensively by the food industry, does not fit these criteria. This study investigated the development of a complex oil blend consisting of commonly used vegetable oils such as corn, rapeseed, sunflower, and palm oil. The aim was to find the optimal blended oil and compare this combination with palm oil in terms of its oxidative stability, antioxidant capacity, and the composition of bioactive compounds (i.e., fatty acids, tocopherols, and carotenoids). Palm oil was found to have greater oxidative stability as a result of its increased concentration of saturated fatty acids. The optimal blended oil, which consisted of corn and rapeseed oil at a ratio of 4:3 w/w, inhibited the superior antioxidant activity, showing a ~33% increase in DPPH• inhibition activity. ATR-FTIR spectra further verified the existence of a significant quantity of saturated fatty acids in palm oil and unsaturated fatty acids in the blended oil. Finally, several correlation analyses revealed interesting connections between oil samples and investigated parameters. This work has the potential to establish a basis for the mass production of oil blends that possess high concentrations of antioxidant compounds and reduce the use of palm oil.

Exploration on the synergistic effect of antioxidants for coal-to-liquid base oil: From the perspective of oxidation resistance and thermal stability

Coal-to-liquid (CTL) base oil is a high-quality lubricant base oil made from coal. However, its poor oxidation stability and short service life limit its application. Pressurized differential scanning calorimetry and Rotary bomb oxidation test are utilized for the evaluation of oxidation stability. Thermogravimetric analysis is performed for the thermal stability assessment. The results showed the reasonable combination of commercial antioxidants can significantly improve the oxidative and thermal stability of two typical CTL base oils, CTL3 and CTL6. The synergistic mechanism of antioxidants in CTL base oil was studied from the perspective of pyrolysis kinetics and pyrolysis mechanism. For CTL3, adding the compound antioxidant 2,6-di-tert-butyl-4-methylphenol (T501) and n-phenyl-1-naphthylamine (T531) results in an almost eightfold increase in oxidation induction time (OIT) and a 33.4 % increase in activation energy compared to pure CTL3. For CTL6, adding the compound antioxidant dialkyl dithiophosphate (T203) and diphenylamine (L57) results in an almost tenfold increase in OIT and a 10.9 % increase in activation energy compared to pure CTL6. The designed commercial antioxidant compound systems had excellent synergistic effects and the synergistic mechanisms were illustrated.

Oxidation and wear behaviors of MoNbTaW high entropy alloy fabricated via laser energy deposition at elevated temperature

The microstructure, mechanical properties at room temperature, oxidation, and wear behaviors of the MoNbTaW refractory high-entropy alloy (RHEA) at elevated temperatures are investigated. The as-deposited MoNbTaW RHEA maintains a single BCC structure and a dendritic morphology. Furthermore, it demonstrates a high yield stress of 1478 MPa and an ultimate yield stress of 1787 MPa at room temperature. The oxidation tests reveal that the oxidation rate constant initially decreases from 0.83 mg2 cm−4 h−1 to 0.78 mg2 cm−4 h−1, then increases to 12.43 mg2 cm−4 h−1 as the temperature rises from 500 °C to 800 °C. Additionally, a linear oxidation kinetic is observed at 500 and 600 °C, while at 800 °C, the parabolic oxidation kinetics is observed. The transition is linked to the development of a multilayer oxide layer structure and the formation of a thicker oxide scale. The results of wear tests at high-temperature show that the wear depth at 600 °C is about 24.886 μm, which is 3.9 times as much as 500 °C (6.437 μm). This indicates that the wear resistance is reduced at 600 °C. In addition, with the increase in temperature, the wear mechanism changes from adhesive wear to abrasive wear.

The improvement in high-temperature oxidation resistance of Ni0.25Co0.25Cr0.22Mo0.14Re0.14 high entropy alloy via industrial chemical vapor aluminizing process

The effects of the protective coating (NiAl coating) on the high temperature isothermal oxidation resistance of Ni0.25Co0.25Cr0.22Mo0.14Re0.14 high entropy alloy (HEA) was discussed in this work. A nickel aluminide (NiAl) coating was obtained on the Ni0.25Co0.25Cr0.22Mo0.14Re0.14 HEA via the industrial chemical vapor aluminizing (CVA) process. Isothermal oxidation tests were applied to NiAl-coated and uncoated samples in ambient laboratory air for durations of up to 200 h at 1050 °C to investigate the effects of the NiAl coating on high-temperature isothermal oxidation resistance of Ni0.25Co0.25Cr0.22Mo0.14Re0.14 HEA. The results revealed that a protective and slowly growing α-Al2O3 oxide layer formed on the surface of the NiAl-coated HEA samples and remained stable even after 200 h of isothermal oxidation. For uncoated HEA samples, not only Cr2O3 but also non-protective spinel oxides (CoCr2O4 and NiCr2O4) were detected on the surface. Weight gain was observed in the NiAl-coated HEA samples due to the formation of a protective and slowly growing α-Al2O3 oxide layer on the NiAl coating. In contrast, the uncoated HEA samples experienced weight loss even after 6 h of isothermal oxidation, as Cr2O3 lost its stability at 1050 °C and non-protective spinel oxides formed. Therefore, it has been determined that the NiAl coating significantly enhance the isothermal oxidation resistance of the Ni0.25Co0.25Cr0.22Mo0.14Re0.14 HEA. The α-Al2O3 oxide layer has prevented severe oxidation of NiAl-coated samples due to its stability at 1050 °C over 200 h and its slow growth rate.

Oxidation and Flammability Tests for Grape (Vitis vinifera L.) Seed Oil

In this work, studies were performed on oxidative stability by determining the transmittance spectra, the components and trichomatic coordinates, and the color differences for grape seed oils (GSO) subjected to a forced oxidation treatment at temperatures of 100 °C and 120 °C, for 4, 8 and 10 h. For this purpose, a constant airflow of 30 L/min was used. GSO was also subjected to flammability tests on a heated cylindrical surface to determine the lowest temperature at which this oil ignites, correlated with the highest temperature at which the oil does not ignite. According to the results, these temperatures are 475 °C and 470 °C, respectively. At these temperatures, the tested oils were darker in color than the reference oil, with the L* parameter having lower values (91.53 and 89.56, respectively). In addition, the correlation coefficients between the evaluated parameters were significant (p ≤ 0.05).

High temperature oxidation resistance and thermodynamic properties of (TaNbZr)N and (TaNbZr)C quaternary ceramic coating

A TaNbZr-based quaternary ceramic coating with a metallurgical transition layer on a titanium alloy surface has been produced. The quaternary ceramic coatings exhibit a face-centered cubic structure and distinct structural orientation. The introduction of carbon and nitrogen significantly improved high-temperature oxidation resistance compared to metallic coatings in cyclic oxidation tests. Specifically, the (TaNbZr)N coating provided effective thermal protection during 800 °C cyclic oxidation for 100 hours (10 cycles). The phase stability and evolution of quaternary ceramic coatings were clarified using in-situ XRD. Further, first-principles calculations elucidated the enhanced thermal stability and high-temperature performance of (TaNbZr)N and (TaNbZr)C coatings.

Influence of aluminum addition on structure, hardness, and oxidation resistance of Ta1−xAlxN thin films

Ta1−xAlxN thin films with 5, 15, and 40 at.% Al addition were co‐deposited by reactive magnetron sputtering and characterized by Rutherford backscattering spectroscopy (RBS), grazing angle X‐ray diffraction (GAXRD), X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), nanohardness, and oxidation tests. GAXRD and XPS analyses showed, regardless of the % Al added, the non‐existence of ternary nitride Ta1−xAlxN, but always as individual binary nitrides, TaN and AlN. Sample TaAlN_15 obtained the highest hardness and H3/E2 values, possibly due to the AlN grains presence, which were efficient in distorting the TaN lattice. All samples failed oxidation tests at 873 K, showing that the Al addition was not efficient in improving this property for tantalum aluminum nitride thin films.

Phase formation, structure and properties of quaternary MAX phase thin films in the Cr-V-C-Al system: A combinatorial study

Tailoring of individual atomic layers via alloying to synthesize quaternary MAX phases allows for expanding their chemical diversity and fine-tuning of their properties. In this study, Cr-V/C/Al multilayered precursors were deposited via combinatorial magnetron sputtering, creating nanostructured architectures with periodic stacking of nanolayers and varying Cr:V ratios. Their phase transformation and underlying reaction mechanisms during subsequent thermal annealing in argon towards the prospective quaternary solid solution (CrV)n+1AlCn MAX phases formation was systematically studied. Crystallization of (CrV)2AlC starts at approximately 500°C, while growth of higher-ordered (CrV)4AlC3 is observed from 960°C. Notably, intergrowth of (CrV)2AlC and (CrV)4AlC3 structures with coherent interface suggests that (CrV)2AlC acts as template for nucleation of (CrV)4AlC3. Thermal stability and high-temperature oxidation tests found that (CrV)2AlC exhibits higher thermal stability compared to (CrV)4AlC3 and films with Cr72.7V27.3 displayed good oxidation resistance at 1000°C, forming a protective bilayer oxide scale consisting of (Cr,Al)2O3 and Al2O3.

High-temperature oxidation and gas thermal shock studies of IC10 simulated specimens with thermal barrier coatings

PurposeThe purpose of this study is to investigate the effects of high-temperature oxidation tests and gas thermal shock tests on IC10 simulated components with thermal barrier coatings under different temperatures and oxidation times.Design/methodology/approachIn the high-temperature oxidation test, specimens were oxidized at three different temperatures of 850, 980, and 1,100 °C for durations of 10, 20, 50, 100, 200, and 300 h, respectively. In the gas thermal shock test, specimens were pre-oxidized for 10, 20, 50, and 100 h, followed by a high-temperature gas thermal shock test at 1,100 °C.FindingsIn the high-temperature oxidation tests, with increasing oxidation time, the oxidation layer thickened, and the air-film holes diameter decreased. The microstructure of the bond coat transitioned from strip-like to block-like, and internal cracks transformed from numerous and short to larger and deeper. Below the bond coat, a noticeable disappearance layer of strengthening phase appeared, with increasing thickness. The strengthening phase in the substrate transitioned from regular square shapes to circles as temperature increased. In gas thermal shock tests at 1,100 °C, the oxidation weight gain ratio increased with longer pre-oxidation times, whereas the erosion weight loss ratio gradually decreased.Originality/valueThe originality and significance of this study lie in its departure from the typical subjects of high-temperature oxidation and thermal shock tests. Unlike common research targets, this study focuses on IC10 simulative specimens with thermal barrier coatings and air-film holes. Furthermore, it investigates the effects of varying temperatures and oxidation durations.