Oxidation Time Research Articles

Estimates of permeability of water vapor in rare earth silicate environmental barrier coatings using the modified theory of deal and grove

The salient elements of the theory of oxide growth under an environmental barrier coating are reviewed. The results from steam oxidation tests recently conducted on environmental barrier coated specimens are reported. The oxide thickness between the ceramic topcoat and Si substrate are reported as a function of time. Also, the results from previously conducted steam oxidation tests are reviewed. An approach to estimate the permeability of water vapor through the various coating systems using the oxide thickness versus time measurements and the theory of oxide growth under an environmental barrier coating is demonstrated. The approach allows one to rank the protection efficiency of the various coating systems against steam oxidation.

Surface-structure-dependent magnetic hyperthermia performance of small Fe nanoparticles

Magnetic hyperthermia therapy (MHT) has received extensive attention due to its advantages, such as high efficiency, noninvasiveness, and no penetration limit. However, the poor performance of small-sized MHT agents limits the MHT treatment efficacy. In this study, the effects of surface properties on the magnetic hyperthermia performance of small-sized Fe nanoparticles (NPs) were explored. The oxidation time of the oxide layer and surface charges that arise due to surface modification are two important parameters of the surface properties of small Fe NPs. The oxidation time greatly affects the magnetism and magnetic hyperthermia properties of the Fe NPs, whereas surface modification only slightly reduces both properties. Overall, this study details a new strategy for developing small-sized magnetic hyperthermia agents that exhibit excellent performance.

A simple two-step approach to the fabrication of VO2-based coatings with unique thermochromic features for energy-efficient smart glazing

Vanadium dioxide (VO2) is considered as one of the most promising materials for the next generation of energy-efficient smart glazing since it experiments a reversible metal-to-insulator transition at near room temperature. Nevertheless, the complexity and high cost associated to the fabrication of VO2-based nanostructures limit the transfer of this technology to the industrial scale. Aware of this opportunity, we present a simple and advantageous method for the fabrication of VO2 coatings on glass substrates which comprises the initial sputtering of vanadium thin films at glancing angles and the subsequent very fast oxidation of such systems in open air atmosphere. Relying on the accurate control of the thermal treatment parameters, as well as the enhanced reactivity of the high surface-to-volume porous deposited structures, thermochromic VO2 coatings were achieved and then characterized by means of scanning electron microscopy, grazing incidence X-ray diffraction, variable temperature UV-vis-NIR spectrophotometry, and resistivity measurements. These investigations allowed us to determine the key role that oxidation temperatures and times not only play in modulating the optical performance of the film, but also in the surprising and advantageous decrease in the transition temperature (up to 12 °C lower than the standard value for pure VO2), which is attained without incorporating doping agents. This fact, together with the remarkable values of luminous transmittance (∼50 %) and solar modulation ability (5–10 %) accomplished for our best samples, opens up an alternative and simpler pathway towards the large-scale manufacturing of VO2 coatings for smart window applications, reaching, on a preliminary basis, similar or even better performances than those obtained so far for single and undoped VO2 films.

Applications and mechanisms of anisotropic two-step Si3N4 etching with hydrogen plasma conditioning

The ability to precisely form Si3N4 spacers is critical to the success of dynamic random-access memory and NAND (NOT AND) flash memory technology development. In this study, we investigated the mechanisms and process windows of an innovative two-step nitride (Si3N4) etch consisting of H2 plasma processing in an inductively coupled plasma chamber followed by either buffered oxide etch (BOE, a mix of NH4F and HF solution) wet clean or in situ NF3 plasma etch. We obtained layer–by-layer removal with each layer’s removal capable of more than 10 nm. We revealed that H can penetrate more than 20 nm deep into the nitride film to transform pristine Si3N4 into SiON after air exposure, which can be subsequently removed by BOE wet clean. The H2 and BOE steps do not need to run back-to-back; the modified SiON layer is stable enough to sustain elevated temperature processing and can be removed by BOE later down-the-line integration. We also demonstrated that using NF3 plasma can have highly selective etch of nitride over oxide due to the incubation time difference between these two types of films. It takes much longer time to initiate the chemical reaction for oxide compared with nitride. Critically, the role of H2 is not the key for high selectivity; instead, it provides an etch directionality and shortens the incubation time for both nitride and oxide.

High sensitivity Ga2O3 ultraviolet photodetector by one-step thermal oxidation of p-GaN films

Gallium oxide (Ga2O3), with an ultra-wide bandgap, is a promising semiconductor material for the manufacture of solar blind ultraviolet photodetectors. The Ga2O3 thin films were successfully prepared by simpler feasible one-step thermal oxidation of p-GaN thin films, which were oxidized at 900 °C with varying oxidation times in the environment with an argon-oxygen ratio of 1000. The effect of different oxidation durations on the physical properties of the Ga2O3 thin films was studied, and particularly, the photoelectric performance of the Ga2O3 thin films was further analyzed. Compared with the GaN thin film, the dark current of the photodetector was approximately reduced by 2.31 × 104 times while the photocurrents of the device maintain the same order of magnitude, causing large photo-to-dark current ratios (PDCRs) of 2.29× 104. Furthermore, the device exhibits impressive characteristics such as high responsivity of 2.13 A/W, super high external quantum efficiency (EQE) of 1040.13%, large detectivity (D) of 1.65 × 1011 Jones, and fast response speed of 0.218/0.112 s under UV light illumination of 254 nm wavelength at −5 V bias. The results indicate that the one-step thermal oxidation can be used as a good application for preparing the device with high sensitivity, fast response and the high-resolution detection.

Preparation and Performance Analysis of a Dimension-Controlled Nano-Drag-Reducing Agent for Low-Permeability Reservoirs

Graphene oxide (GO), as a derivative of graphene, is rich in reactive functional groups on its surface for modification, and the modified graphene oxide (M-GO) has excellent special properties. In this paper, the improved Hummer’s method was used to analyze GO by adjusting the amount of oxidant (potassium permanganate), oxidation time, and temperature, using Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and laser particle size measurement. The successful synthesis of dimension-controlled GO in the range of 630–1000 nm was confirmed. On this basis, modified graphene oxide (O-M-GO) was prepared by grafting octadecyltrimethoxysilane (OCT). The successful synthesis of O-M-GO was confirmed by FT-IR and XRD. Through a contact angle test, the contact angle of GO before modification was 80 ± 0.5° and that of O-M-GO after modification was 105 ± 0.5°. Combined with SEM analysis, the change in the wettability of O-M-GO was clarified. Core flow test results showed that after O-M-GO was injected into the core, the subsequent brine injection pressure decreased by 14.21%, and the permeability was 1.166 times that before the brine injection. When the injection concentration was 50 mg/L, the drag reduction rate was 14%.

Synthesis of g-C3N4 Derived from Different Precursors for Photodegradation of Sulfamethazine under Visible Light

In this study, a series of g-C3N4 nanosheets were prepared by various thermal oxidative etching times from four different precursors (urea, melamine, dicyandiamide and thiourea). The physicochemical properties of these g-C3N4 nanosheets were analyzed in detail using scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence emission spectra, Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) analysis and ultraviolet-visible diffuse reflectance. The results revealed that the g-C3N4 nanosheets obtained a thinner layer thickness and larger specific surface area, with an extension of thermal oxidative etching time. Meanwhile, sulfamethazine (SMZ), one of the most widely used sulfonamides, was used to evaluate the photocatalyst activity of the g-C3N4 nanosheets prepared in this study. Compared to other g-C3N4 nanosheets, urea-derived g-C3N4 nanosheets under 330 min thermal oxidative etching showed the highest photocatalytic activity for SMZ under visible light. In conclusion, our study provides detailed insights into the synthesis and characterization of g-C3N4 nanosheets prepared from various precursors and highlights the importance of thermal oxidative etching time in determining the photocatalytic activity of these materials.

Influence of Hydrogen on Vintage Polyethylene Pipes: Slow Crack Growth Performance and Material Properties

The distribution of hydrogen and how this can be widely achieved plays a significant role in the transition from fossil fuels to clean fuel. Using the existing natural gas pipeline network can be a suitable option for countries with extensive pipeline infrastructure. This study is aimed at investigating the compatibility of the existing polyethylene (PE) distribution pipe network with hydrogen. This paper utilises the cyclic pennsylvania edge notch test (CPENT) method together with material property measurements including melting point, crystallinity, and oxidative induction time (OIT) to understand the impact of exposing two different PE pipe resins to hydrogen at different exposure times. It was found that exposure to hydrogen has a noticeable impact time to failure, while the bulk crystallinity, OIT, and melting point showed little change. A change in crystal orientation was observed, and this likely accounts for the difference in time to failure when exposed to hydrogen.

Chemical industry wastewater treatment by coagulation combined with Fenton and photo‐Fenton processes

AbstractBACKGROUNDChemical industry wastewater is challenging to treat because of the various chemicals they contain. In this study, the treatment of chemical industry wastewater, which produces a wide variety of chemical aids, such as foam control agents, and silicones used in the textile, food and cosmetics industries, by coagulation combined with Fenton or photo‐Fenton oxidation processes was investigated. In coagulation studies, optimum pH and coagulant dose were determined with polyaluminum chloride (PAC), polyaluminum chloride hydroxide sulfate (PACS) and FeCl3 coagulants, while Fe2+, H2O2, pH and oxidation time were optimized in Fenton studies.RESULTSIn the coagulation, higher wastewater treatment was achieved with PAC compared to PACS and FeCl3 coagulants, and 62.6% chemical oxygen demand (COD) and 44.3% total organic carbon (TOC) removal were obtained at 500 mg L−1 PAC and pH 8. In the coagulation and Fenton oxidation, 92.4% COD, 79.7% TOC, 99.8% turbidity, and 96.7% total soluble solids (TSS) were achieved. The application of photo‐Fenton oxidation instead of Fenton oxidation did not cause a significant change in chemical industry wastewater. The cost of chemical industry wastewater treatment by coagulation and Fenton oxidation was calculated as $19.16 m−3, and the cost per kilogram of CODremoved was determined as $2.89 kg−1.CONCLUSIONIn chemical industry wastewater treatment, high TSS and turbidity removal can be achieved by coagulation with PAC, and the wastewater load subjected to Fenton oxidation can be reduced. Efficient wastewater treatment was provided by Fenton oxidation after coagulation. The application of the photo‐Fenton oxidation process instead of Fenton oxidation did not show the expected effect. However, toxicity studies should be performed in treated wastewater using coagulation–Fenton oxidation processes in future studies. © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Investigation of Multistage Oxidation Behavior of Al4SiC4 Powders with Aid of Back Propagation Artificial Neural Network

In order to investigate the multistage oxidation behavior of aluminum silicon carbide (Al4SiC4), back propagation artificial neural network (BP‐ANN) has been trained and employed considering the oxidation temperature, time, and aspect ratio. The results denote that the BP‐ANN model can accurately and efficiently simulate the oxidation behavior of Al4SiC4 powders with different reaction laws. In addition, the extrapolation ability suggests that the BP‐ANN model can maintain a high accuracy with the coefficient of determination ≥0.801 to expand the experimental data to 1.2 times the original range. By incorporating a real physical picture model developed by the research group, the experimental data can be further expanded to 2.2 times. This study can provide a new path to recognize the oxidation behavior of materials with multistage oxidation.

Analytical model for strength of MAX phases considering high‐temperature oxidation and plastic deformation

AbstractAs a promising high‐temperature material, MAX phases have attracted much attention owing to their combined merits of metals and ceramics. In this study, a temperature‐dependent analytical model for prediction of the strength of MAX phases considering high‐temperature oxidation and plastic deformation was proposed. A relationship among the strength, Young's modulus, strain‐hardening exponent, crack size, and temperature was established. The accuracy of the model was verified by a comparison between the model predictions and available experimental data. The proposed analytical model can provide a straightforward and effective way to predict the strength of MAX phases over a wide range of temperatures. Moreover, the quantitative effects of oxidation time, strain‐hardening exponent, and Young's modulus on the strength, as well as their evolution with temperature, were analyzed. The findings of this study would be useful for the high‐temperature strength prediction and design of MAX phase materials.

Processing-controlled radial heterogeneous structure of carbon fibers and primary factors determining their mechanical properties

Commercial polyacrylonitrile (PAN)-based carbon fibers, T800S and T700S, were gradually etched from the surface to the inside by thermal oxidation at 600 °C up to 10 h for investigating microstructure and resulting mechanical properties depending on the position in the radial direction. While T800S showed a gradual decrease in mechanical properties with respect to the oxidation time, those of T700S showed an unusual behavior due to the existence of a transition zone between the skin and the core, where the structural development was shown to be as high as the surface. This transition zone is presumed to be due to the collisions (shear stress-induced alignment) between the skin and core as the difference in their degree of structural development is large. In addition, as a result of analyzing various microstructures over a wide range from macroscopic to atomic/bond scale, it was confirmed that microvoid diameter and crystalline orientation were dominant structural factors in determining the mechanical properties of carbon fibers. However, the graphitic crystal size and ID/IG ratio (the amounts of defects) showed little variation along the radial direction. Based on those overall analyses, more detailed structural sketches of two different types of CFs from the skin to cores are suggested. We believe that the integrated studies on radial heterogeneity and structure-property relationships of carbon fibers provide essential information for manufacturing high-performance carbon fibers.

Study the effect oxidation time on physical properties of cdo thin films prepared by thermal evaporated

thin films were prepared by thermal evaporated method of cadmium metal on a glass substrate, then conventional oxides in air at 500ᵒC and different oxidation times (30, 60 and 90) mint. The characterization of samples were carried out by atomic force microscopy and UV-VIS spectroscopy. Detailed optical and morphological properties of the prepared films are presented at different oxidation times. A UV-VIS transmition spectrum of produced films shows high transmission in visible, IR region and low transmission in UV region. Average grain size in the range of nanometer and decreases with increasing oxidation time.

Preparation of TiO2 Nanotube Arrays with Controllable Morphology and their Superhydrophobic Modification for Photocatalytic Degradation of Water Pollution

TiO2, as a photoactive semiconductor material, where like photocatalysis technology is a hot topic of research in recent years, shows great potential for application in the direction of environmental pollution treatment and solar-chemical energy conversion. In this paper, we prepared titanium dioxide nanotube arrays (TNAs) by a simple one-step anodic oxidation method in an ethylene glycol electrolyte containing ammonium fluoride under optimized conditions. The effects of anodic oxidation voltage, anodic oxidation time and annealing temperature on the growth of TNAs were systematically investigated. It was shown that the sample parameters of TNAs prepared by anodic oxidation were influenced by the anodic oxidation conditions, and the tube diameter and anodic oxidation voltage were positively correlated in a certain range. The TNAs with the best characterization performance were selected for photocatalytic degradation, and methylene blue (MB) was used to simulate the organic pollutants. The results show that TNAs have better photocatalytic activity compared with conventional TiO2. On the basis of this, stearic acid (SA) and TNAs were compounded and modified. The TNAs were made to obtain superhydrophobic properties. The photocatalytic degradation experiments were carried out on them. The results show that the superhydrophobic modification does not affect their photocatalytic activity, so it is possible to achieve photocatalytic degradation of water pollution under the premise of superhydrophobicity, which has greater application prospects in water pollution treatment.

Growth characteristics of scanning micro-arc oxidation coating on Ti6Al4V alloy

ABSTRACT In this study, the ceramic coating was prepared on Ti6Al4V alloy by scanning micro-arc oxidation (SMAO). The growth features of SMAO coating were investigated by combining the voltage and discharge variation. The result shows that a higher working voltage is obtained during SMAO treatment owing to additional resistance from the electrolyte column. As the SMAO goes on, the discharge region moves to the electrolyte column edge, exhibiting an annular shape. The current density with Gaussian distribution is observed between the stainless-steel tube (cathode) and titanium substrate (anode), which causes the SMAO coating to show a higher thickness in the middle and lower on both sides. Similar to traditional MAO, the SMAO coating has an enhancement in the thickness, pore size and Si content with increasing oxidation time, but coating degradation occurs in the later stage of SMAO. The SMAO coating mainly consists of amorphous SiO2, rutile and anatase phases.

Effect of oxidation time on microstructure and mechanical properties of Cf/SiC–Al composites after high-temperature oxidation

Effect of oxidation time on microstructure and mechanical properties of Cf/SiC–Al composites after high-temperature oxidation

Oxidation Kinetics of Ti-6Al-4V Alloys by Conventional and Electron Beam Additive Manufacturing.

New manufacturing processes for metal parts such as additive manufacturing (AM) provide a technological development for the aeronautical and aerospace industries, since these AM processes are a means to reduce the weight of the parts, which generate cost savings. AM techniques such as Laser Powder Bed Fusions (LPBF) and Electron Beam Fusion (EBM), provided an improvement in mechanical properties, corrosion resistance, and thermal stability at temperatures below 400 °C, in comparison to conventional methods. This research aimed to study the oxidation kinetics of Ti-6Al-4V alloys by conventional and Electron Beam Additive Manufacturing. The thermogravimetric analysis was performed at temperatures of 600 °C, 800 °C, and 900 °C, having a heating rate of 25 °C/min and oxidation time of 24 h. The microstructural analysis was carried out by thermogravimetric analysis. Thickness and morphology of oxide layers were analyzed by field emission scanning electron microscope, phase identification (before and after the oxidation process) was realized by X-ray diffraction at room temperature and hardness measurements were made in cross section. Results indicated that the oxidation kinetics of Ti-6Al-4V alloys fabricated by EBM was similar to conventional processing and obeyed a parabolic or quasi-parabolic kinetics. The samples oxidized at 600 °C for 24 h presented the lowest hardness values (from 350 to 470 HV). At oxidation temperatures of 800 and 900 °C, however, highest hardness values (from 870 close to the alpha-case interface up to 300 HV in base metal) were found on the surface and gradually decreased towards the center of the base alloy. This may be explained by different microstructures presented in the manufacturing processes.

Study the electrical properties of ZnOSiO2 detector prepared by free rappid thermal oxidation

Zinc thin films deposited on (n-type)silicon at 510o C with oxidation times (10,20,30,35) sec have been oxidized. Zinc have been deposited by thermal diffusion method using heater instead of conventional furnace .It is found that we can get zinc oxide with outoxegen and closed farneces rapidly. The electrical properties in dark show that the detector is shottky diode, and the best time to obtain the detector is 35 sec, and the ideality factor is 3.3 with a work function of 0.58 ev. It is found that the resalts at light power (50,100,150,200,250) mw/cm2.Show that the detector oxidiced in 35 sec have detectivity factor 540.8 and have a high responsivity which enable the detector to detect the IR signals.

Multi-scale structure characterization of ozone oxidized waxy rice starch

The elucidation of multi-scale structural variation and oxidation reaction mechanism of ozone oxidized waxy rice starch molecules remains a big challenge, limiting its development of intensive processing. In the present work, the changes in the structure of waxy rice starch after ozone treatment were systematically researched by various characterization methods. The study has shown that with the increase in ozone oxidation time, the granules of oxidized starch were polygons with multiple face depressions. It was also observed that ozone first attacked the amorphous zone of the starch granules and then penetrated the crystalline zone. Combining 1D and 2D NMR (1H NMR, 13C NMR, HSQC and HMBC) and other methods, it was proved that ozone oxidation led to ring splitting between C2 and C3 of the glucose unit. The resulting hemiacetal groups showed different types of structures. Among them, the main structures were intramolecular acetals and intermolecular hemiacetals. This research offered theoretical guidance for the utilization of ozone oxidation technology for starch modification and the development of waxy rice new foods.

Effect of coating on the oxidation behavior of turbine rotor material in supercritical water

AbstractHigh‐temperature oxidation behavior of IBN‐1 alloy, Ni–Cr thermally sprayed coating, Ni–Cr thermally sprayed coating with surface shot peening and grinding treatment in supercritical water have been investigated at 650°C under 25 MPa. The oxidation kinetics of IBN‐1 steel follows the parabolic law. Compared with substrate metals, the oxidation resistance of IBN‐1 steel with the three kinds of Ni–Cr coating treatment has been greatly improved due to the formation of Cr‐rich oxide and the oxidation kinetics deviated from the parabolic behavior seriously. The deviation may be attributed to differences in the oxide phase with an increase in oxidation time. Furthermore, the difference in oxidation rate among different Ni–Cr coating surface treatment processes can be observed. The related mechanism has been discussed.