Oxidation Resistance Ability Research Articles

A facile approach to prepare Cu(I) based adsorbents for selective CO adsorption with excellent oxidation resistance ability

A facile approach to prepare Cu(I) based adsorbents for selective CO adsorption with excellent oxidation resistance ability

Five new flavonoids and their pharmacological activities from Iris tenuifolia Pall.

Five new components including two new isoflavones, 5, 7, 2′, 3′-tetrahydroxy-6-methoxyisoflavone (1), 5, 7, 2′, 3′-tetrahydroxy-8-methoxyisoflavone (2), one flavonol 3, 5, 3′, 4′-tetrahydroxy-7, 2′-dimethoxyflavonol (3), one flavanone (2S)-5, 7, 3′-trihydroxy-2′-methoxyflavanone (4), and one flavanonol (2R, 3R)-3, 5, 3′, 4′-tetrahydroxy-7, 2′-dimethoxyflavanonol (5), along with nine known flavonoids (6–14) were isolated from under ground parts of Iris tenuifolia Pall. Their structures were elucidated by NMR and HRESIMS data and by comparison of CD spectra with compounds having similar structure. The separated compounds were evaluated for in vitro antioxidant activities by DPPH and ABTS. The α-glucosidase inhibitory activity of the compounds were evaluated with the pNPG method, the results indicated flavonoids were potential inhibitors of α-glucosidase. Moreover, in vitro anti-oxidative assay using flow cytometry indicated that compounds 1–5 showed strong oxidation resistance ability on C8D1A cells without affecting the cell viability.

Thermomechanical characterization and conventional rolling of a novel β-solidifying γ-TiAl alloy with excellent comprehensive properties

The development of the β-solidifying γ-TiAl alloys with good oxidation resistance and thermal deformation ability has always been crucial for the practical application. However, increasing the content of the antioxidant elements, such as Nb, Al, etc., tends to be detrimental to the deformability of the alloys. In this work, a novel Nb, Mn containing β-solidifying TiAl alloy with the nominal composition of Ti-43Al-1.5Mn-3Nb-0.2C-0.2Si-0.1B (at. %) (named as NbMn-TiAl) is invented, which goes through the single β phase as well as the α phase during solidification, resulting in the final as-cast microstructure of nearly full lamellar structure (NFL). Subsequently, the isothermal compression tests were performed within a temperature range of 1100 °C–1300 °C and a strain rate range of 0.001 s−1-10 s−1, the hot processing maps and constitutive equation were established. Moreover, the deformation mechanisms were clarified, including the bending/kinking of the α2/γ lamellar colonies, the dynamic recrystallization (DRX) of γ phase and α phase at different temperatures. Rolled bars with a diameter of 12 mm were then directly fabricated from the ingot by conventional hot rolling process. The as-rolled bars exhibited excellent oxidation resistance and mechanical properties that outperform many available TiAl alloys manufactured using various methods.

Improvement of oxidation resistance and alumina regrowth ability of Ni-30Cr-5Al alloy without and with Y: Nanocrystallization effect

Nanocrystallization of Ni-Cr-Al alloys decreases critical Al content (NAl*) for Al2O3 scale formation down to a level much lower than practical alloy Al content (NAl), and this is particularly prominent for the alloys with NAl≤ NAl*. In this work, oxidation of coarse-grained (CG) Ni-30Cr-5Al with NAl > NAl* and its nanocrystalline (NC) counterpart has been studied, with the focuses on the following issues: (i) nanocrystallization effect on Al2O3 steady-state growth and regrowth; (ii) nanograin growth effect on Al2O3 adhesion; and (iii) role of Y played in NC alloys by comparing the differences in oxidation of the NC alloys without and with Y.

Effects of acute heat stress on haemato-biochemical parameters, oxidative resistance ability, and immune responses of hybrid yellow catfish (pelteobagrus fulvidraco × P. vachelli) juveniles.

This study investigated the effect of heat stress on the physiological parameters, oxidation resistance ability and immune responses in juvenile hybrid yellow catfish. Heat stress group exposed to 35°C and control to 28°C. Blood and liver were sampled at different hours' post-exposure. Results showed that red blood cell (RBC), white blood cell (WBC) counts, Hemoglobin (HGB) levels and hematocrit (HCT) values increased significantly (P < 0.05) post-exposure to heat stress. This indicates the increase of cell metabolism. Serum alanine aminotransferase (ALT) and aspartate transaminase (AST) activities, total cholesterol (TC), total protein (TP), triglyceride (TG) and glucose increased significantly (P < 0.05) indicating the need to cope with stress and cell damage. Liver TC, TG, COR hormone, C3 complement increased significantly from 24 to 96h. Heat stress mostly affects the hepatic antioxidant and immune resistance functions, resulting in increments of cortisol levels, lysozyme, superoxide dismutase (SOD), and catalase (CAT) enzyme activities. The increase of Malondialdehyde (MDA), alkaline phosphatase (AKP) indicate stimulation of the immune responses to protect the liver cells from damage. The decrease in Liver TP indicated liver impairment. Decrease in Glycogen content from 6 to 96h indicated mobilization of more metabolites to cope with increased energy demand. Interestingly, results showed that heat stress trigged costly responses in the experimental fish like accelerated metabolism and deplete energy reserves, which could indirectly affect ability of fish to set up efficient long term defense responses against stress. These results provide insight into prevention and management of stress in juvenile hybrid yellow catfish.

Investigation on the effects of pretreatment on the surface characteristics of duplex plasma-treated AISI P20 tool steel

Plasma nitriding (PN) coupled with physical vapor deposition (PVD) has emerged as one of the promising surface treatments to achieve an elevation in the tribological, oxidation resistance, and load-bearing ability of the engineering materials in recent years. However, the consequential impact of heat treatment processes implemented upon the base substrate on enhancing the wear resistance of such materials cannot be disregarded. In the present study, AISI P20 steel samples in as received and heat-treated conditions were selected for the investigation to establish the influence of pretreatment prior to the duplex treatment through microstructural, phase and compositional characterizations carried out by the means of XRD, SEM and EDS analysis followed by surface roughness and microhardness tests. Heat-treated samples were observed to bear higher hardness than the as-received ones, while surface roughness evaluations indicated a reversed behavior. Further, tribological investigations were conducted for an accurate estimation of wear resistance and coefficient of friction of the duplex-coated samples. All the results of the investigations indicated a significant influence of the white compound layer in governing the tribological and mechanical properties of the duplex-coated samples for as received as well as heat-treated samples.

Interesting influence of Al2O3 on the catalytic stability of Co2P, MoP and CoMoP catalysts for dry reforming of methane.

Interestingly, the metal-support interaction (MSI) influence of different metal phosphides on catalytic stability might be different in dry reforming of methane (DRM). After being supported on Al2O3, there was a rise, decline and no change in the catalytic stability of CoMoP, MoP and Co2P, respectively. This was probably because the MSI can tune the structural stability, methane dissociation ability and oxidation resistance ability of metal phosphides, which were the key factors that determined their catalytic stability.

The effect of citric acid on the microstructure and activity of MoP phosphide for dry reforming of methane

A series of MoP catalysts (MoP-CAx) were synthesized by adding citric acid (CA) to solutions of (NH4)6Mo7O24·4H2O and (NH4)2HPO4 with a fixed molar ratio of Mo:P:CA = 1:1: x (x = 0, 1, 4, 8) followed by drying and reduction in H2. The addition of CA had a significant effect on the microstructure (surface area and particle dispersion) and performance of MoP for dry reforming of methane (DRM). Among these MoP-CAx catalysts, the MoP-CA8 was found to show the highest catalyst stability, which should be attributed to the best matching of oxidation resistance ability and methane dissociation ability of MoP.

Oxidation Behavior and Interfacial Bonding Properties of NiCrAl Alloys

AbstractThe oxidation behavior and oxidation kinetics of NiCrAl alloy were studied by XRD, SEM and the thermogravimetric analysis method. The adhesion strength of the films was characterized by micron scratch tester. The results show that the oxide film has not formed at 600 °C and 700 °C, and an oxide layer of Al2O3 has formed at 800 °C. Moreover, an oxide layer composed of Cr2O3 and Al2O3 has formed at 900 °C. After oxidation at 800 °C for 100 h, partial θ‐Al2O3 has transformed to steady‐state α‐Al2O3 and a dense oxide film of Al2O3 with the thickness of about 620 nm has formed on the surface of the NiCrAl alloy. The oxidation kinetics curve of the alloy obeys the parabolic law and there are two oxidation rate constants in the oxidation process. The oxidation rate constant of 1.58×10−4 mg2⋅cm−4⋅h−1 in the early oxidation period (0∼12 h) and the oxidation rate constant of 1.04×10−4 mg2⋅cm−4⋅h−1 in the late oxidation period (12∼100 h) indicate that the oxidation resistance ability of the alloy increases with the extension of oxidation time. With the increase of the oxidation time, the interface bonding strength between the oxide film and the substrate can be improved and reaches 5.21 N at 800 °C for 100 h.

SiC/MoSi2-SiC-Si Oxidation Protective Coatings for HTR Graphite Spheres with Residual Si Optimized.

SiC/MoSi2-SiC-Si coatings for nuclear graphite spheres with different Si-Mo ratios were prepared through two-step pack cementation. XRD, SEM and EDS techniques were used to analyze the composition and microstructure of the coatings. The oxidation resistance performance of the composites at 1773 K, in static air, was investigated. The results showed that the SiC-MoSi2-Si coating could be divided into a denser inner layer and a loose outer layer, as free Si would infiltrate into the inner micropores of the coating under capillary force. When the Si/Mo ratio of the second pack cementation was 7:1, the thickness of the denser inner layer basically reached the maximum and exhibited excellent oxidation resistance ability, with a weight gain of 0.19% after 200 h oxidation. The performance improvement was analyzed as a result of the addition of SiC and C powder in the pack cementation process, effectively increasing the phase interfaces to relax the thermal stress in the coating. With different Si-Mo ratios, the content of residual Si and the formation rate of SiO2 glass layer on the coating surface were also different, thus affecting the anti-oxidation performance. The main reactions occurring at different stages of the oxidation curve were also discussed.

Carbon nanotubes modified by multi-heteroatoms polymer for oxidative dehydrogenation of propane: Improvement of propene selectivity and oxidation resistance

Nanocarbon has been considered as a promising catalyst for oxidative dehydrogenation of propane (ODHP) due to its abundant reactive oxygen species, minimal carbon deposition and distinctive electronic and structural properties. Unfortunately, its further development has been restricted for a lengthy period due to its poor propene selectivity and low durability under high temperature or oxygen-rich conditions. To address these deficiencies, the hybrid catalysts composed of small amount of multi-heteroatoms N, P, S co-doping polymer (PZS) and oxidized carbon nanotubes (OCNTs) were prepared, which can achieve 63% propene selectivity at 14.3% propane conversion with catalytic stability over 20 h in ODHP reactions at 520 °C. This distinctive catalytic performance has reached the best level of reported doped nanocarbon catalysts. In addition, a series of kinetic experiments and structural characterizations on the proposed catalysts indicated that the material has superior oxidation resistance and strong ability to inhibit the formation of carbon oxides. The P–O and S–C species on the catalyst surface play a very important role in improving the propene selectivity and enhancing the oxidation resistance of OCNTs.

Mechanism of efficient remediation of U(VI) using biogenic CMC-FeS complex produced by sulfate-reducing bacteria

Uranium in groundwater during uranium mining activities urgently needs to be remediated through effective and environmental-friendly approaches. The reduction and immobilization of soluble U(VI) using biogenic carboxymethyl cellulose modified iron sulfide complex (biogenic CMC-FeS complex) is one of the emerging and innovative methods. However, its removal mechanism is largely unknown. Here, biogenic CMC-FeS complex with extracellular polymeric substances (EPS) and CMC was successfully synthesized by sulfate-reducing bacteria (SRB) and showed highly dispersible capacity. The tryptophan and tyrosine, which were the main components in EPS produced by SRB on CMC-FeS surface, significantly increased the U(VI) removal capacity of the biogenic CMC-FeS complex compared with chemically synthesized CMC-FeS. U(VI) removal was attributed to the adsorption of soluble U(VI) by ≡FeO+, CMC, tryptophan, and tyrosine on the biogenic CMC-FeS complex, following its reduction by S2-, S22- and Fe2+. Moreover, biogenic CMC-FeS complex with CMC-to-FeS molar ratio of 0.0005 performed well in the presence of bicarbonate (5 mM), humic acid (10 mg/L), or co-existing cations such as Pb2+, Ni2+, Cd2+, Mn2+, and Cu2+ (200 ug/L) at pH 7.0, and displayed relatively high oxidation resistance and stability ability. This work provides an in-depth understanding of the biogenic CMC-FeS complex for the U(VI) removal and contributes to the development of cost-effective U(VI) remediation technologies.

Influence of Gamma Irradiation and Water Aging on the Space Charge Characteristics of Epoxy Micro-Nano Composites.

Epoxy micro-nano composites are well-known to exhibit enhanced electrical, mechanical as well as thermal properties compared to base epoxy resin. Yet, a clear understanding need to be achieved on the long-term aging performance of the epoxy micro-nano composites. The present review article is a comprehensive study on the impact of gamma irradiation and water aging on the space charge characteristics of epoxy micro-nano composites that are applicable as insulant in high-voltage power apparatus. Ion-trapping nanoparticles, which possess good oxidation resistance and high ion trapping ability, are being chosen as nanofillers along with silica micro fillers in epoxy micro-nano composite material for improving the reliability of electrical insulation structures. The epoxy micro-nano composite specimens were subjected to gamma irradiation (4 kGy and 8 kGy) and water aging (under room temperature and at 90 °C), to analyze the effect of aging on space charge accumulation and charge decay characteristics. The mean magnitude of accumulated space charge density of epoxy micro-nano composites tends to increase with an increase in gamma irradiation dose as well as an increment in water diffusion coefficient. The mean lifetime of the space charge decay during depoling has significantly reduced after gamma irradiation and is converse with water aged specimen. Voltage polarity reversal studies have indicated that a part of homo-charge injected from electrodes remained as hetero-charge just after polarity reversal and could result in the distortion of electric field thereby increasing the electric field enhancement factor.

Au–Ag bimetallic nanoparticles decorated silicon nanowires with fixed and dynamic hot spots for ultrasensitive 3D SERS sensing

Abstract Three-dimensional (3D) SERS substrates have being intensively investigated since they can afford substantial hot spots and trap targets exponentially, silicon nanowires (SiNWs) array is a promising candidate due to its facile preparation. Most often, the SiNWs based substrates were decorated with pure Ag or Au nanoparticles (NPs), Au–Ag bimetallic NPs (BMNPs) with superior plasmonic properties and stabilities are rarely studied for the fabrication of SiNWs based SERS substrates. In this work, we reported a facile method to fabricate Au-Ag BMNPs decorated SiNWs as 3D SERS substrates, the effects of Au-Ag BMNPs scale and composition ratios on SERS performance were well investigated through experiments and theoretical simulations. The vertically aligned SiNWs coated with dense Au-Ag BMNPs further improved the sensitivity by forming fixed and dynamic hot spots, and the detection limit of R6G on SiNWs-AuAg can be as low as 10-12 M by using a portable Raman spectroscopy. Meanwhile, the prepared 3D SERS substrate showed a higher SERS enhancement factor (EF) and oxidation resistance ability due to the synergistic effect of Au and Ag atoms in Au–Ag BMNPs. Considering the facile fabrication process and excellent performances, the prepared 3D SERS substrate can be potentially applied for ultrasensitive detection of trace analytes.

Synthesis and characterization of yttrium nitrate hexahydrate

Nanostructured coatings are extensively employed in aerospace applications as they unveil unique and excellent properties because of their nano-sized structural behavior. This article focusses on the study of preparation of yttrium (III) nitrate hexahydrate-based nano-sized structural coating obtained by sol-gel method and the analysis of their properties. The properties that are suitable for aerospace applications such as thermal stability, oxidation resistance ability, heat resistant nature, phase stability were analyzed using Scanning Electron Microscope (SEM), Energy Dispersive X-ray Analysis (EDX) characterization techniques.

Oxidation and ablation behaviour of multiphase ultra-high-temperature ceramic Ta0·5Zr0·5B2–Si–SiC protective coating for graphite

To provide reliable oxidation protection for carbon materials under harsh high-temperature aerobic environments, a dense monolayer-multiphase ultra-high-temperature ceramic Ta0·5Zr0·5B2–Si–SiC (TZSS) coating was fabricated by a combination of dipping and in-situ reaction. The oxidation resistance of the TZSS coating was investigated at 1923 K in air. The results indicated that the TZSS coating could offer at least 70 h of oxidation protection for the matrix material. The synergistic oxygen-blocking effect of the thick oxide layer formed during the oxidation test and the inner coating, played a key role in the oxidation protection process. These were responsible for the excellent oxidation resistance ability of the TZSS coating. Additionally, the ablation performance of the TZSS coating was also investigated under increased heat flux from 2.4 MW/m2 to 4.2 MW/m2. The ablation behaviours changed from the oxidation and evaporation of coating materials to mechanical scouring, corresponding to increased mass and linear ablation rates. Interestingly, after ablation for 40 s under a heat flux of 4.2 MW/m2, a new microstructure composed of “lath-like” Ta4Zr11O32 solid solution grains was found in the ablation center. This oxide layer possessed few micropores, which could provide reliable protection for the matrix material under ultra-high-temperature oxygen-containing airflow erosion, thus preventing further damage to the composite.

The research on oxidation resistance ability and mechanical properties of carbon fiber reinforced phenolic resin composites

Carbon fiber reinforced composite (CFRP) has been widely used in a lot of areas with its distinguished properties, especially mechanical properties. However, both carbon fibers and polymer substrate cannot resist high air temperature environment, limiting the application of CFRP, such as in the aerospace fields. The paper proposes two kinds of carbon fiber with oxidation resistance coatings, which are used as reinforced components to make phenolic resin substrate composites. Weight difference method, mechanical test machine and scanning electron microscope are used to characterize the antioxidation ability, mechanical properties, and surface morphology of composites. The results show that SiC/SiO2 coated carbon fibers and SiC–ZrO2–MoSi2/Ni coated carbon fibers can increase the anti-oxidation ability without decreasing the mechanical properties of composites. The failure temperature is around 1200 °C and 1600 °C respectively.

Effects of Different Drying Methods on Maillard Reaction Products and Their Oxidation Resistant Ability in Oil-Tea Camellia Seed Oil

Effects of Different Drying Methods on Maillard Reaction Products and Their Oxidation Resistant Ability in Oil-Tea Camellia Seed Oil

Factors affecting SiC–ZrO2–MoSi2/Ni antioxidation coating made by composite plating on carbon fibres

ABSTRACTCarbon fibres (CF) have been used in various fields because of their unique properties. However, the oxidation resistance ability of CF is not good enough. The paper discusses the issue of using composite plating method to deposit SiC–MoSi2–ZrO2 coating at the surface of CF. The plating factors, including nanoparticle concentration, plating bath temperature, current density, agitation rate and electroplating time, which affect the structure and performance of coating have been discussed. The energy dispersive spectrometer has been applied to test the mass fraction of nanoparticles in the coating. Also, the surface morphology of coated CF has been characterised by a scanning electron microscope and the antioxidation ability of each sample has been tested by the weight difference method. The results indicate that with the proper plating factors, the coating can improve the antioxidation performance of CF and its reinforced composites. The residual weight of coated CF is over 52% after 1400°C oxidation for 15 min.

High Oxidation Resistance of CVD Graphene-Reinforced Copper Matrix Composites.

Copper-based materials are common industrial products which have been broadly applied to the fields of powder metallurgy, electrical contact, and heat exchangers, etc. However, the ease of surface oxidation limits the durability and effectiveness of copper-based components. Here, we have developed a powder metallurgy process to fabricate graphene/copper composites using copper powders which were first deposited with graphene layers by thermal chemical vapor deposition (CVD). The graphene/copper composites embedded with an interconnected graphene network was then able to be obtained by vacuum hot-pressing. After thermal oxidation (up to 220 °C) in humid air for several hours, we found that the degree of surface oxidation of our samples was much less than that of their pure Cu counterpart and our samples produced a much smaller increase of interfacial contact resistance when used as electrical contact materials. As a result, our graphene/copper composites showed a significant enhancement of oxidation resistance ability (≈5.6 times) compared to their pure Cu counterpart, thus offering potential applications as novel electrical contact materials.