Formation Of Oxide Film Research Articles

Effect of Preheating treatment in Ar Atmosphere on Oxidation Resistance of Mg-Y Alloys and formation of oxide film

Effect of Preheating treatment in Ar Atmosphere on Oxidation Resistance of Mg-Y Alloys and formation of oxide film

Rare earth addition powered corrosion resistance of the surface oxide film on GCr15 bearing steel substrate

Rare earth (RE) has been demonstrated to have a series of positive effects on performance of bearing steel. In this study, we propose a new mechanism that RE element can enhance the corrosion resistance of bearing steel under atmospheric condition by promoting the formation of a thicker surface oxide film with a greater thickness in the inner protective layer which consists of Fe3O4 and Cr2O3. Such an evolution is primarily associated with the dissolved RE element in steel matrix. Besides, EIS data regression can provide a way to quantify the corrosion resistance evolution in surface oxide film on steel substrates.

Electrokinetics-Driven Anodic Oxide Pore Formation: Linear and Weakly Nonlinear Analysis

Abstract Anodization of aluminium in an acidic medium facilitates the formation of well-ordered nanoporous anodic oxide films. The mechanism of pore formation is investigated as a morphological instability using a simplified model. The model accounts for the high field conduction law and field-assisted reactions (oxide formation/dissolution) only at the oxide-solution interface. The role of Butler–Volmer electrokinetics, electrolyte pH, anodic efficiency, and interface curvature on reaction kinetics are taken into account. Linear stability analysis suggests that the oxide film is unstable to well-defined wavelengths in specific ranges of parameters such as anodizing efficiency, applied voltage and electrolyte pH. Subsequently, a weakly nonlinear analysis is carried out to determine the nature of bifurcation beyond the stability threshold. Our findings indicate that the instability exhibits a subcritical nature, well in agreement with experimental observations.

Influence of composition and temperature on oxide film formation for Fe-Cr-Ni alloys in simulated PWR primary water

ABSTRACT The growth of oxide films on Fe-Cr-Ni alloys in simulated pressurized water reactor (PWR) primary system environments was investigated, with focus on the influence of alloy composition and temperature. Oxide film thicknesses were measured for 90 specimens prepared from compact tension (CT) test pieces. Cross-sectional observations were also conducted on coupon specimens using scanning transmission electron microscopy (STEM). The behavior of Ni-based alloys, specifically Alloy 600, and Fe-based alloys, specifically Type 316 stainless steel, were compared. Ni-based alloys exhibit superior corrosion resistance due to slower Fe diffusion kinetics compared to Fe-based alloys, leading to the formation of a nickel-enriched protective layer at the metal-oxide interface. The oxidation rates of Ni-based alloys follow an Arrhenius-type temperature dependence. In contrast, Fe-based alloys show a more complex temperature-dependent behavior, with reduced oxidation rates at higher temperatures that are likely due to changes in oxide dissolution. Higher chromium concentrations in both alloy types improve the protectiveness of the oxide film towards corrosion by forming a more compact inner oxide layer. The study identifies three primary factors influencing oxide film growth: reactions at the metal-oxide interface, diffusion within the oxide layer, and processes at the oxide-solution interface. The relative significance of these processes varies depending on the alloy composition and temperature.

Research on the Corrosion Resistance and Cytotoxicity of Medical Forged Co-28Cr-6Mo Alloy

Co-Cr-Mo alloy as a human body implant material has a long history, because of its excellent corrosion resistance and biocompatibility, and is widely used in human hip joint materials. Co-Cr-Mo alloy in the human body is often in a passivation state; the formation of dense oxide film on the alloy surface prevents further corrosion of the alloy. The main component of the passivation film is the oxide of Cr, so a layer of oxide film formed by Cr on the surface of Co-Cr-Mo alloy is the reason for its good corrosion resistance. In biocompatibility, cytotoxicity is the first choice and necessary option for biological evaluation, and cytotoxicity can quickly detect the effect of materials on cells in a relatively short time. Therefore, this research conducted a comparative evaluation on the corrosion resistance and biocompatibility of forged Co-Cr-Mo alloys produced in domestic and foreign alloys in line with medical standards. Three simulated human body fluids and Princeton electrochemical station were selected for corrosion resistance experiments, and it was found that the corrosion resistance of four alloys in sodium citrate solution inside and outside China would be reduced. All the alloys exhibit secondary passivation behavior in Hanks solution, which improves the corrosion resistance of the alloys. According to the self-corrosion potential Ecorr analysis, the corrosion resistance of domestic B alloy is the best, while that of foreign R31537 alloy is poor. In the biocompatibility experiment, the biocompatibility of Co-Cr-Mo alloy was evaluated through the measurement of contact Angle and cytotoxicity reaction. The experimental results show that Co-Cr-Mo alloy is a hydrophilic material, and the contact Angle of foreign R31537 alloy is smaller, indicating that the surface of R31537 alloy is more suitable for cell adhesion and spreading. According to the qualitative and quantitative analysis of the cytotoxicity experiment, the toxic reaction grade of domestic A, B and R31537 alloy is grade 1, the toxic reaction grade of C alloy is grade 2, and C alloy has a slight toxic reaction.

The influence of CeO2 on the oxidation resistance of TaC/Ni composites

The in-situ TaC/Ni composites with different CeO2 content (0 wt%, 1 wt%, 2 wt%) were prepared by reactive sintering method, and their oxidation behavior in air at 1073 K was analyzed by static cyclic oxidation method to investigate the influence mechanism of CeO2 on the oxidation resistance of composites. The results show that the CeO2 particles are distributed around the TaC particles in the Ni matrix, and the oxidation behavior of composites with different CeO2 content conforms to the linear kinetic law. The oxide film is mainly composed of NiTa2O6 and a small amount of NiO. The generation reactions of Ta2O5 and NiTa2O6 induce a high expansion and compressive stress in oxide scale, leading to the formation of nonprotective oxide film with pores and cracks on the surface. As the addition of CeO2 increases from 0 wt% to 2 wt%, the thickness of oxide scale on composites obviously reduces from 505 μm to 122 μm, and the Ni and Ta oxides content decreases, leading to the reduction of pores and cracks in oxide scale. The Ce ion generated from the dissolution of CeO2 particles mainly distributes in the Ta oxides during the oxidation process, which hinders the outward diffusion of Ni and Ta ions, resulted in the improved oxidation resistance of TaC/Ni composites.

Corrosion behaviors of La doped in-situ synthesized nano TiB2/6061 composites

The microstructure and corrosion behaviors of the in-situ synthesized nano TiB2/6061 composites with La doping were investigated by scanning electron microscope, potentiodynamic polarization and electrochemical impedance spectroscopy in 3.5 wt% NaCl solution. The results indicated that La can make a significant improvement of corrosion resistance for TiB2/6061 composites. The corrosion potential of La-TiB2/6061 composites has increased by 11.31% compared with the composites without La. With La doping, the dispersive distribution of TiB2 particles suppressed the extending of corroded pits, the refined grains promoted the formation of oxide film in passive environment.

Oxidation behavior of 9Cr-RAFM steel at high temperature

The effect of yttrium on the mechanism of oxidation film formation of the 9Cr reduced activation ferritic/martensitic (9Cr-RAFM) steel was investigated. Four alloys yttrium contents ranging from 0 to 0.065% were melted in a vacuum induction furnace and subjected to continuous isothermal oxidation experiments. The alloys were oxidized in air at 600, 700, 800 and 900 °C for 100 h. Oxidation kinetic curves were obtained and analyzed to study the effect of yttrium on the oxidation resistance of the alloys at high temperatures. The oxide films formed on the alloys were observed and analyzed by X-ray diffractometry, scanning electron microscopy and electron probe X-ray microanalysis. The results indicated that the oxidation weight gain of the samples varied with the yttrium content, with the highest gain observed in the yttrium-free alloy sample, and the least in those containing 0.065% yttrium. Adding yttrium significantly enhanced the high temperature oxidation resistance of 9Cr-RAFM alloy by promoting the formation of a selective Cr2O3 oxide film. The film improved the adhesion of the oxide layer to the base metal, reduced the oxidation rate, and thereby enhanced the high-temperature oxidation resistance of the alloy.

On-demand performance optimization of AlGaN/GaN high electron mobility transistors using stoichiometric variation of dielectric alloy AlxTayO

The current research investigates the potential advantages of optimally combining wide bandgap Al2O3 with high dielectric constant (high-κ) Ta2O5 for gate dielectric applications. Various compositions of 10 nm AlxTayO oxide films are grown on the Al0.3Ga0.7N/GaN heterostructure by co-sputtering Al and Ta metals, followed by thermal oxidation at 500 °C. The average root-mean-square roughness of the grown oxide films is ∼1.2–1.4 nm compared to 0.4 nm for as-deposited metal. X-ray photoelectron spectroscopy and transmission electron microscopyconfirm the formation and thickness of the grown oxide films. The bandgap (Eg) of the oxide films calculated from O1s electron energy loss spectra show a linear increase from 4.85 eV for pure Ta2O5 to 6.4 eV for pure Al2O3. The dielectric constant (εox) calculated from capacitance–voltage (CG−VG) measurements decreases linearly from 25.7 for Ta2O5 to 7.9 for Al2O3. The interface trap density (Dit) is estimated from the frequency dispersion of capacitance–voltage (CG−VG) characteristics. The DC and radio frequency (RF) characteristics of AlxTayO/Al0.3Ga0.7N/GaN high electron mobility transistor (HEMT) devices are measured and compared with the Schottky HEMT devices (without any gate oxide). Compared to Schottky HEMT devices, AlxTayO/Al0.3Ga0.7N/GaN HEMT devices show superior DC characteristics, which helps us achieve maximum RF output power. Furthermore, the OFF-state measurements show that the AlxTayO/Al0.3Ga0.7N/GaN HEMT devices can sustain higher source-to-drain voltages, from a minimum of 88 V on pure Ta2O5 metal-oxide-semiconductor (MOS)-HEMTs to a maximum of 138 V on pure Al2O3 MOS-HEMTs before the dielectric breakdown happens, compared to a 57 V breakdown voltage on Schottky HEMT devices. An oxide variation of AlxTayO, with Al composition ratio of 0.34, shows an exceptional ION/IOFF ratio of 4 × 1011, a gate leakage current of 8 × 10−12 A/mm, a near-ideal subthreshold slope of 63.8 mV/dec, and the unity current gain frequency (fT) of 25.6 GHz.

Corrosion of Copper, Cupronickel, Nickel Aluminium Bronze and Super-Duplex Stainless Steel Rotating Cylinder Electrodes in Seawater under Turbulent Flow Conditions

The corrosion of uncoated metals in a marine environment restricts the choice of suitable engineering metals and alloys. Anodic dissolution of metal and cathodic reduction of oxygen are important processes and formation of a surface oxide film can affect both electrode reactions. Charge transfer and mass transfer data can provide information on corrosion rate and mechanism. Several metals and alloys having a history of use in marine engineering are considered, including copper, two copper alloys (cupronickel and nickel aluminium bronze) plus a more recent addition to strong, corrosion resistant alloys (a super duplex stainless steel). The rotating cylinder electrode offers the benefits of a controlled, turbulent flow of electrolyte, facilitating controlled mass transfer in a compact cell geometry which is well-suited to bench-top operation. These features are illustrated using a variety of electrochemical techniques, including open-circuit potential vs time monitoring, linear sweep voltammetry, rotation speed step- or potential step current transients and linear polarisation resistance measurements. Seawater taken from Langstone Harbour, Hampshire, UK, was filtered, air-saturated, pH 8.0 and maintained at 25 °C. Dimensionless group correlations and graphical plots (using an analogous approach to the Koutecky-Levich equation for an RDE) enabled contributions of charge transfer-, mixed- and mass transfer- controlled data to be appreciated, allowing the Tafel slopes of electrode reactions, the diffusion coefficient of dissolved oxygen, the mass transfer coefficient for oxygen reduction and the mean corrosion rate to be estimated.

Effect of laser remelting on the microstructures and properties of NiCoCrAlY-based coatings prepared by high-speed air fuel supersonic flame (HVAF)

In order to improve the oxidation resistance of the coating, laser remelting technology was used to remelt the HVAF multi-component modified coating. The influence of laser remelting technology on the phase state, microstructure characteristics, and isothermal oxidation behavior of coatings was studied. The experimental results indicate that a coating with complete morphology and no defects was obtained on the surface. There is a significant amount of metallurgical bonding and partial mechanical interlocking between the remelted layer and the substrate. The remelted layer is mainly composed of β-NiAl phase, accompanied by a small amount of γ′ phase and oxide phase. The microhardness test results show that the average hardness of the remelted layer is 1.1–1.42 times that of the prepared coating, and the bonding strength has increased by 23 %. After 100 h of high-temperature oxidation, the oxidation rate of the 4N3T4H remelted layer is the lowest, at 1.5 × 10−15 cm2/s, which is one order of magnitude lower than that of the as-sprayed coating. This is because after laser remelting, the remelted layer has the inherent hysteresis diffusion effect of HEA, which can improve the high-temperature oxidation resistance of the remelted layer and basically eliminate many pores and cracks contained in the HVAF coating. The coating density is significantly increased, which is conducive to hindering the diffusion of oxygen. Meanwhile, the oxide of HVAF coating mainly accumulates at pores and cracks, and there is no or late formation of uniform and dense oxide film on the surface. The surface of the remelted coating after oxidation forms a relatively uniform and dense oxide film, providing more effective protection for the substrate.

Reaxff MD Analysis of Substrate Material Properties into Oxide Films during Thermal Oxidation Process of Group IV Semiconductor Materials

Oxide films used in semiconductor devices have attracted much attention because they can protect substrate surfaces from impurities and suppress current loss. In recent years, there have been growing expectations for oxide film formation on Ge substrate materials, which have a uniquely high hole mobility among group IV semiconductor materials. We have investigated an efficient oxide film formation method using reactive molecular dynamics (ReaxFF MD) simulation. We focused on dissociation, the initial step of oxidation, and confirmed how easily dissociation occurs. To search for conditions that promote dissociation, we checked the dangling bound density and adsorption angle on the substrate surface. The wider space between dimers on the Ge substrate may result in a shallower O2 adsorption angle. This increases the dissociation rate because each of the two O2 atoms is more likely to bond to the substrate.

Atomistic insight into structure and properties of oxide films formed upon oxidation of Al–Mg alloys – reactive molecular dynamics study

Oxidation phenomena on metal surfaces can be advanced using atomistic modeling for the study of the structure and properties of the growing oxide films. Molecular dynamics investigations were performed to study thermal oxidation of single-crystal and polycrystalline Al–Mg alloys with low Mg content of up to 2.5 at. %. Structure, topological atom network and surface topography of the oxide films grown on Al–Mg surfaces at 300, 475 and 663 K are determined. Mg-content and temperature dependent oxide films developed on Al-Mg alloy substrates with two-phase oxide film formation as also confirmed experimentally. It is related with a gradual long-range order formation above 475 K for (Al,Mg)-oxide films, for which solid amorphous phase predominates over crystalline phase. The 1.12-nm-thick oxide films grown at 300 K are fully amorphous and build up from (Al, Mg)-oxide which the Al2O3 dominates. Increase of Mg coefficient confirms faster Mg diffusion to oxide/alloy interface at high oxidation temperature and the formation of MgO-like network. The presence of planar crystal defect (grain boundary, GB) into Al-Mg alloy substrate governs the kinetics of oxide film growth and its structure evolution. GB also compensate internal stresses during oxide film growth. Obtained results are in good agreement with experimental observations.

Investigation on Be, Mg, Ca, B, Ga, C, Si, and Ge atoms doped on Al (111) surface and their effect on oxygen adsorption: A first-principle calculation

Oxygen corrosion of the aluminum alloy has a substantial impact on the durability of engineering materials and equipment. To better understand how various alloy elements affect oxygen corrosion, we used first-principle DFT method to study the role of each given dopant atom (Be, Mg, Ca, B, Ga, C, Si, and Ge) in the formation of surface oxide film on the Al (111) surface, in the case replacing a surface Al atom. Our calculations show that the electron gain or loss abilities of these alloy elements differ from that of Al metal, with Be, B, C, and Si atoms tending to penetrate into the surface, Mg, Ca, and Ga atoms protruding, and Ge atom just embedded into the Al (111) surfaces. Additionally, the type of doping element at the Al (111) surface can greatly affect the O2 absorption, predicting that Ca-doped surface absorb the least amount of oxygen, followed by Si-doped surface, with Be-, Mg-, B-, Ga-, C-, and Ge-doped surfaces showing higher O2 absorption. Based on adsorption energy (Eads) and partial density of states (PDOS) analysis, we conclude that the doped Al (111) surfaces can make O2 adsorption different owing to the difference in electronic properties of the doping atoms. These insights draw a greater knowledge of the role of alloy elements in the oxygen corrosion of Al alloys, enabling guidance for designing more corrosion-resistant materials.

Mechanism of Anodic Dissolution of Tungsten in Sulfate–Fluoride Solutions

Thin passive films on tungsten play an important role during the surface levelling of the metal for various applications and during the initial stages of electrochemical synthesis of thick, nanoporous layers that perform well as photo-absorbers and photo-catalysts for light-assisted water splitting. In the present work, the passivation of tungsten featuring metal dissolution and thin oxide film formation is studied by a combination of in situ electrochemical (voltammetry and impedance spectroscopy) and spectro-electrochemical methods coupled with ex situ surface oxide characterization by XPS. Voltametric and impedance data are successfully reproduced by a kinetic model featuring oxide growth and dissolution coupled with the recombination of point defects, as well as a multistep tungsten dissolution reaction at the oxide/electrolyte interface. The model is in good agreement with the spectro-electrochemical data on soluble oxidation products and the surface chemical composition of the passive oxide.

Competitive relationship between the FCC + BCC dual phases in the wear mechanism of laser cladding FeCoCrNiAl0.5Ti0.5 HEAs coating

This work elaborated the microstructure and wear behavior of laser cladding (LC) FeCoCrNiAl0.5Ti0.5 high-entropy alloys (HEAs) coatings on AISI 1045 steel substrates. The microstructure of the HEAs coatings is mainly comprised of a body-centered-cubic (BCC) + face-centered-cubic (FCC) dual-phase structure. Besides, the coating exhibites high hardness. During the friction process, the FCC phase was more prone to deformation and peeling than BCC structure. As the alloying elements (such as Al, Ti, and Cr) tend to form oxide film at high temperatures during friction, the friction process of the LC FeCoCrNiAl0.5Ti0.5 coating was mainly controlled by oxidative wear and adhesive wear mechanisms. Friction test results showed that the coating owned excellent wear resistance and the wear rate of the HEAs coating was only 6.53 % of the wear rate of the steel substrate.

Role of oxidants in the anodic oxidation of 2024 aluminum alloy by dominating anodic and cathodic processes

The addition of oxidants into the electrolyte of Al anodic oxidation can alter the anodic and cathodic reactions, further affects the quality of the oxide film. In this paper, the role of two typical oxidants of H2O2 and Na2MoO4 in the microstructure and corrosion resistance of the oxide film on 2024 aluminum alloy was investigated by the scanning electron microscopy (SEM), Mott Schottky plots and electrochemical impedance spectroscopy (EIS). The addition of H2O2 increases the oxygen evolution amount on the anode Al and more oxygen can participate in the oxide film formation to improve the compactness. The addition of Na2MoO4 results in the deposit of MoO2 on the cathode plate to accelerate the hydrogen evolution reaction by the catalytic action of the MoO2, which further accelerates the anodic reaction to form a thick oxide film. As a result, the corrosion resistance of the oxide film is significantly improved by adding H2O2 or Na2MoO4 due to the promotion of film thickness and compactness.

The oxide films formed under the low oxygen pressure in a particular system containing competing chromium and aluminium

AbstractIn this paper, pre‐oxidation treatment was carried out at 950 °C under oxygen pressure of 10−16 atm for nickel‐10 % chromium‐x % aluminium‐1 % silicon‐0.5 % yttrium(x=0 wt.–%, 1 wt.–%, 3 wt.–%, 5 wt.–%) alloys. Morphology and structure of oxide layers on the alloys after pre‐oxidation were analyzed by scanning electron microscopy and electron discharge spectroscopy. The results showed that a chromium oxide film was formed on the surface of the alloy without aluminium addition, while the oxide layer on the surface of the alloy with aluminium addition gradually transformed into M2O3 (M=aluminium and chromium) oxide film. The oxidation behavior was analyzed by means of chemical thermodynamics, and it was seen that because the interaction coefficient,εijof aluminium and chromium is a positive value, the increase of aluminium addition will strengthen the interaction and increase the diffusion coefficient,Diof aluminium and chromium. The diffusion of chromium and aluminium in each other therefore promotes their interaction, which is beneficial to the formation of the outer oxide film. Thus, with the increase of aluminium addition, the thickness of the outer oxide film gradually increased, and the aluminium content in M2O3 (M=aluminium and chromium) increased significantly, and with 5 % aluminium added, the aluminium oxide of the outer oxide film became the main body.

Effect of Temperature on Thermal Oxidation Behavior of Ti-6Al-4V ELI Alloy.

In this paper, the morphological, micromechanical and tribological characteristics of the Ti-6Al-4V ELI alloy after thermal oxidation (TO) were identified. TO was carried out at temperatures of 848 K, 898 K and 948 K over a period of 50 h. Microscopic examination revealed that an increase in temperature resulted in an improved uniformity of coverage and an increased oxide grain size. Micromechanical tests showed that TO of the Ti-6Al-4V ELI alloy led to an increase in hardness and deformation resistance. Following oxidation, a decrease (by approximately 10-22%) was observed in the total mechanical work of indentation, Wtotal, compared to the as-received material. The formation of protective oxide films on the Ti-6Al-4V ELI alloy also led to the improvement of tribological characteristics, both when tested under dry friction conditions and in Ringer's solution. The sliding wear resistance increased with an increase in the oxidation temperature. However, a greater degree of wear reduction (by approximately 30-50%) was found for the lubricated contact in comparison with the dry friction tests. Surface roughness also increased with the increase in temperature.

Enhancing rubber concrete with supercritical fluid-assisted Nano-SiO2 embedding and high-temperature stirred waste rubber

Using waste rubber particles(WRP) to replace fine aggregates in producing rubber concrete promotes recycling and reduces natural sand consumption, which is crucial for sustainable resource use. Unfortunately, rubber's low rigidity and poor interface bonding with the concrete matrix cause a significant strength loss. Many have done surface treatments on the particles, yet these often result in low efficiency and insignificant strength increases. This paper introduces a novel approach: employing supercritical fluid (CO2) assisted shearing to embed nano-silica and high-temperature stirring for pre-treating rubber particles. This improves the rigidity, removes impurities, and enhances surface smoothness. Thermal Gravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy(FT-IR), Scanning Electron Microscope(SEM), and Energy-Dispersive X-ray Spectroscopy(EDS) tests on treated particles show SiO2 embedded inside, clean surfaces, and hard oxide film formation. Rubber concrete prepared using this shows obvious improvement in mechanical properties compared to untreated rubber particles, with 7-day and 28-day cubic compressive strengths increasing by 74.9 % and 54.8 %, respectively. These increases outperform most reported in the literature.