Oxide Film Thickness Research Articles

High temperature oxidation enhanced by laser remelted of CoCrFeNiAlx (x = 0.1, 0.5 and 1) high-entropy alloys

In order to further improve the oxidation resistance of CoCrFeNiAlx (x = 0.1, 0.5, and 1) high entropy alloys (HEAs), the surface of CoCrFeNiAlx prepared by vacuum arc melting is controlled by laser surface remelting (LSM) and the high-temperature oxidation properties of CoCrFeNiAlx before and after LSM is systematically studied. The results revealed that, with the increase of Al content, the parabolic velocity constant kp value gradually decreased after LSM treatment. Moreover, CoCrFeNiAl0.1 formed a continuous Cr2O3 oxide layer, CoCrFeNiAl0.5 formed an outer layer of Cr2O3 oxide film and an inner layer of Al2O3 precipitation, and CoCrFeNiAl1 formed a uniform and dense Al2O3 oxide layer on the entire area. After 100 h of oxidation, the oxide film thickness of three alloys is around 5 µm, 4 µm, and 3 µm, respectively. The improvement in oxidation resistance after LSM can be ascribed to the formation of a dense re-melted layer, uniform distribution of the elements, refinement of the re-melted layer.

Modeling of oxide-film thickness in electrolytic in-process dressing grinding with workpiece swing

Modeling of oxide-film thickness in electrolytic in-process dressing grinding with workpiece swing

Enhanced corrosion resistance in accident-tolerant FeCrAl alloy by water-assisted laser surface modification

FeCrAl alloys have been widely developed as an alternative accident-tolerant cladding material in light water reactors since the Fukushima nuclear accident in 2011. A large thermal neutron cross-section is the most severe challenge for FeCrAl alloys in the final commercial use, and a thinner cladding was necessary to overcome this, which led to higher corrosion resistance requirements. To address this issue, a surface treatment process is described here to enhance the corrosion resistance of the FeCrAl alloy via a water-assisted laser modification. By varying the laser power and laser scanning speed, the relationship between corrosion and processing parameters was investigated to better understand the mechanism with various characterizations. A heat-transfer model with boiling heat transfer boundary conditions was built and simulated using a finite element method to reveal the change in temperature field during processing. A corrosion test was performed with a simulated light water reactor (LWR) hydro-thermal environment for 120 h. The corrosion rate and oxide film thickness of the water-assisted laser modified FeCrAl alloy sample decreased by 83 % and 50 %, respectively, compared to the as-received one, and this was ascribed to the formation of protective oxide film during laser processing, along with grain refinement and elimination of holes and scratches.

Study of Vertical Capacitance in an n-Type 4H-SiC Stepped Thick-Oxide Trench MOS Structure

In this work, characteristics of trench sidewall capacitance were investigated in a 4H-SiC stepped thick-oxide (STO) trench metal–oxide–semiconductor (MOS) structure. Multigroup SiC trench MOS capacitor test patterns with different structures and geometric parameters were designed and fabricated. From the capacitance–voltage measurements, the characteristics of the described SiC STO trench MOS were calculated and analyzed, including the thicknesses of the oxide at different locations in trench, the position of the oxide step at trench sidewall, and the flat-band voltages as well as the oxide charge densities of MOS from the upper part and lower part of oxide step at trench sidewall. Results showed that the flat-band voltages of MOS from the upper part (10.2 V) and lower part (12.5 V) of trench sidewall step had pronounced positive shifts over the ideal flat-band voltage (0.36 V), indicating a massive negative charges in the sidewall oxide film. Meanwhile, the net oxide charge density of MOS from the lower part of sidewall step ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 0.92\times10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-2}$ </tex-math></inline-formula> ) was smaller than that from the upper part ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 2.41\times10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-2}$ </tex-math></inline-formula> ), which was likely attributed to the massive shallow states in the oxide and to the poor quality of the thick-oxide film grown via chemical vapor deposition technology. The present works are providing a convenient technology to monitor the trench MOS structure by measuring the capacitance during SiC trench MOSFETs fabrication.

Effect of annealing on magnetic properties of iron-based soft magnetic composites with iron oxide insulator

This study introduces a closed oxidation system for forming an oxide insulating film on the surface of pure-iron powder, using an oxygen concentration analyzer to monitor the progress of the reaction. The closed system is designed such that all the supplied oxygen completely reacts to form an oxide film at 500 ℃. It is established that the oxide-film thickness can be controlled by the quantity of oxygen supplied. XRD analysis indicates that the oxide film is mostly composed of the Fe3O4 phase. The TEM oxygen mapping image shows that the oxide film is uniformly and completely formed on the surface of pure-iron powder. Further, toroidal cores are fabricated by compacting the pure-iron powder coated with an oxide insulating film. To relieve the strain generated during compaction, annealing is performed in the 400–700 ℃ range. At annealing temperatures below 550 ℃, the change in the core loss is not considerable (85.0 W/kg at room temperature (23 ℃) and 94.8 W/kg at 550 ℃). However, above 550 ℃, sudden increase in the core loss is observed (505.9 W/kg at 700 ℃). The Fe3O4 in the oxide film reacts with the Fe phase to form FeO above 570 ℃, which is the eutectoid temperature. This phase transformation damages the insulation of the oxide film, resulting in a sharp increase in the eddy current loss. The hysteresis loss decreases from 71.2 W/kg to 43.9 W/kg with the increase in the annealing temperature. It is determined that the pure-iron powder core coated with an oxide insulating film is heat-resistant up to a temperature of 550 ℃.

Comprehensive noise reduction performance of polyurethane/ferroferric oxide/activated carbon fiber felt coated flexible composites

Aiming at poor noise reduction performance of light and thin fiber aggregate materials, the polyurethane/ferroferric oxide/activated carbon fiber felt coated flexible composite materials were prepared by coating composite method. The effects of composite structure, ferroferric oxide particle content (10–25%), and coating thickness (0.25–1 mm) on the composites' sound absorption and sound insulation properties were systematically studied. The results show that with the increase of coating thickness and ferroferric oxide particle content, the sound absorption curve of the composite obviously moves to low frequency, and the resonance frequency decreases. When the particle content increased from 0% to 20%, the resonance frequency shifted 967 Hz. When the ferroferric oxide content is 25%, the maximum sound absorption coefficient and maximum transmission loss of the composite are 3.5 times and 25 times of that of the fiber felt, respectively. When the polyurethane/ferroferric oxide film thickness is only 0.1 mm, the maximum sound absorption coefficient and the average sound absorption coefficient of the composite are 3.5 times and 2.3 times of those of activated carbon fiber felt, respectively. Compared with single fiber felt, the composite material has better sound absorption, sound insulation, and mechanical properties while maintaining the thin and soft characteristics of the fiber felt.

Atomically Thin Antimony‐Doped Indium Oxide Nanosheets for Optoelectronics

AbstractWide bandgap semiconducting oxides are emerging as potential 2D materials for transparent electronics and optoelectronics. This fuels the quest for discovering new 2D metal oxides with ultrahigh transparency and high mobility. While the former can be achieved by reducing the thickness of oxide films to only a few nanometers, the latter is more commonly realized by intentional doping. This article reports a one‐step synthesis of few‐unit‐cell‐thick and laterally large antimony‐doped indium oxide (IAO). The doping process occurs spontaneously when the oxide is grown on the surface of a molten Sb–In alloy and 2D IAO nanosheets can be easily printed onto desired substrates. With thicknesses at the atomic scale, these materials exhibit excellent transparency exceeding 98% across the visible and near‐infrared range. Field‐effect transistors based on low‐doped IAO nanosheets reveal a high electron mobility of ≈40 cm2 V−1 s−1. Additionally, a notable photoresponse is observed in 2D IAO‐based photodetectors under ultraviolet (UV) radiation. Photoresponsivities of low‐doped and highly doped IAO at a wavelength of 285 nm are found to be 1.2 × 103 and 0.7 × 103 A W−1, respectively, identifying these materials as promising candidates for the fabrication of high‐performance optoelectronics in the UV region.

Effect of storage time on the surface status and resistance spot weldability of TiZr pretreated 5182 aluminum alloy

TiZr pretreatment is generally applied for surface protection of aluminum alloys, especially in the automotive industry, to prevent the adverse effect of surface oxidation on the resistance spot welding (RSW) process. However, the TiZr passivation layer may deteriorate in long-term storage and affects the resistance spot weldability. This paper studies the surface status variation of TiZr pretreated AA5182-O during 18-month storage and the corresponding weld performance. It is found that the TiZr passivation layer maintains its integrity and provides effective protection to extend the acceptable storage life. During the initial three months, both nugget size and mechanical performance of the welds show a mild decrease because of the limited surface oxidation. Meanwhile, the surface resistance rises accordingly to the oxide film thickening and exhibits a high correlation with the weld quality indexes, making it a good representative indicator to assess the weldability deterioration. The early 3-month storage is essential to control the oxide growth and maintain the weldability, and it is recommended to add some additional surface protection measures during this period.

Demonstration of the model of physicochemical processes in heavy liquid metal cooled reactors in an example of the THEADES experiment simulation

Activities have been currently underway across the world to build heavy liquid metal-cooled reactors. Thus, for example, the ALFRED and BREST-OD-300 reactor designs use lead coolant, while the MYRRHA and CLEAR-I reactors use lead–bismuth coolant. The high corrosive and erosive activity of the coolant requires regulations oxygen concentration (1 ÷ 4E-6 wt.%) and flow velocity (0.5 ÷ 2.5 m/s). Due to the complex geometry of the reactor circulation circuit flow paths, numerical simulation methods are used extensively to justify scheduled modes of operation for liquid metal coolants. Correct justification of the complex oxygen transport processes in liquid metals requires the respective physicochemical computation model, which takes into account the main reactions of oxygen with the coolant and the structural materials.This paper presents a physicochemical model, which includes the following processes: erosion, growth, and dissolution of the two-layer oxide film, coagulation and dissolution of metal oxides in the circuit with subsequent deposition on filtering elements, and inflow from mass transfer apparatuses. StarCCM+, a commercial CFD code, was used as the tool in this study. The physicochemical model was implemented using models of passive impurities, which are used to simulate oxygen transport in the circulation circuit.Capabilities of the presented model were demonstrated based on the results of investigating thermohydraulic and physicochemical processes obtained at the THEADES experimental facility. The duration of the simulation was 1000 h.The distributions of impurity concentrations, increased erosive activity areas, as well as the total amount of oxides deposited on filter and the amount of oxygen entering the circuit have been obtained as a result of the calculations. The surface distribution of the oxide film thickness on the test facility surfaces contacting the coolant has also been calculated. These data can be extrapolated to reactor elements that operate under conditions that are similar to the considered experiment. For example, fuel assemblies.Simulation of thermocouples, as well as taking into account manufacturing technology made it possible to improve the accuracy of calculating the flow’s thermohydraulic characteristics as compared to earlier studies.

Niobium Oxide Coated Mesoporous Platinum Nanoparticles for the Oxygen Reduction Reaction

Effective and economic methods of converting chemical energy into electricity or vice versa (i.e., through the use of fuel cells) must be developed to aid in the transition to renewable energy sources. One of the major barriers in the commercialization of fuel cells is the disparity in speed and efficiency between the two fuel cell reactions: the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) of which the latter is orders of magnitude slower.1 Mesoporous Pt prepared by electrodeposition has been shown to have increased activity towards the ORR than the industry standard Pt nanoparticles (NPs) supported on carbon.2 Platinum based catalysts, however, lack long term stability under acidic fuel cell conditions. One method that has been found to mitigate the long-term loss of Pt catalyst stability and activity is coating platinum with nanoscale thin films of niobium oxide.3 In this work, niobium oxide was investigated as a stabilizing coating for mesoporous Pt NP catalysts.Mesoporous Pt NPs were synthesized via electrodeposition to form ~50 nm diameter NPs. The Pt NPs were then coated with niobium oxide films with a varying nanoscale thickness that ranged from 3 to 50 nm. The niobium oxide films were fabricated using atomic layer deposition (ALD) or electrodeposition.3,4 Scanning electron microscopy and transmission electron tomography were used to evaluate the porosity and surface morphology of the Pt NPs before and after coating with niobium oxide. X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy were used to confirm the presence and composition of the niobium oxide films. Electrochemical characterization by cyclic voltammetry and electrochemical impedance spectroscopy under acidic conditions was used to determine an optimal thickness of the niobium oxide film that stabilizes the size and morphology of the Pt NPs while maintaining catalyst activity. The Pt NPs coated with <10-nm thick niobium oxide films were observed to have an increased long-term performance in comparison to their uncoated counterparts. Stabilizing NP catalysts for improving their long-term activity is a vital step towards creating affordable alternatives to fossil fuels by maximizing renewable energy resources. Debe, M. K. Electrocatalyst Approaches and Challenges for Automotive Fuel Cells. Nature 2012, 486, 43–51.Paul, M. T. Y.; Gates, B. D. Mesoporous Platinum Prepared by Electrodeposition for Ultralow Loading Proton Exchange Membrane Fuel Cells. Sci. Rep. 2019, 9, 4161.Eastcott, J.; Gates, B. D. Nanoscale Thin Films of Niobium Oxide on Platinum Surfaces: Creating a Platform for Optimizing Material Composition and Electrochemical Stability. Can. J. Chem. 2017, 96, 260–266.Zhitomirsky, I. Electrolytic Deposition of Niobium Oxide Films. Mater. Lett. 1998, 35, 188–193.

(Digital Presentation) Corrosion Behavior of Aluminum-Carbon Composite Bipolar Plates in Polymer Electrolyte Membrane Fuel Cells

ABSTRACT Bipolar plate (BP) is an important multifunctional component in polymer electrolyte membrane fuel cells (PEMFCs) system (1,2) which should possess some specifications such as superior electrical and thermal conductivity, high corrosion resistance, good mechanical performance, and low cost (3). BP candidate materials are roughly classified into carbon-based and metal-based materials. Carbon-based materials are lightweight and have excellent corrosion resistance, but are inferior to metal-based materials in terms of gas shielding properties and mechanical strength. Metallic materials have the opposite characteristics, and corrosion resistance is a particular and important issue. Aluminum (Al) is considered as a promising BP material because of having some important characteristics such as low density and low cost (4). Earlier, it was proposed that the PEMFC BP can be divided into two parts: gas isolation plate and flow path forming material (5). Normally, metallic BPs are corroded exclusively at the rib part where BP contacts with the gas diffusion layer (GDL), while there is not much corrosion at the bottom of the flow path. Therefore, the corrosion resistance required for the reaction gas isolation plate would not be as high as required for the flow path forming material (5). In this study, a composite BP using Al as the reaction gas isolation plate and a carbon-based material as the flow path forming material was fabricated to investigate the corrosion behavior of Al through power generation test.A single cell was assembled using a BP consisting of a 1 mm thick glassy carbon flow path forming material and an Al reaction gas isolation plate, and the power generation tests were performed for 500-1000 h to investigate the corrosion of Al. Separately, Al plates were subjected to exposure tests in the expected environment during the cell operation. After the exposure and power generation tests, the Al bipolar plates were analyzed by SEM and TEM. Furthermore, in order to improve the contact resistance, a power generation test using a bipolar plate coated with TiN-SBR on both sides of Al isolation plate (6) was also conducted.When Al plate was immersed in water at 80 °C, a thick oxide layer of about 1.3 µm was formed with whitish appearance. On the contrary, Al maintained its gloss after exposer in the saturated steam. After 1000 h power generation test using the Al-carbon BP, the surface of Al diaphragm plate maintained its gloss at cathode side. On the other hand, a thick oxide layer of about 1 µm was formed from center part to outlet part along with the flow field on the anodic plate. It suggests that the water drops were generated on the anodic flow field although the corrosion products were slight enough for safe use of Al as BPs with the channel former made of carbon.Thus, the following findings were obtained as a result of conducting the PEMFC power generation test using a composite BP with Al as the reaction gas isolation plate and glassy carbon as the flow path forming material. No significant corrosion was observed on the Al isolation plate on the cathode side after the 1000 h power generation test, but the anode side turned into white from the center of the flow path to the gas outlet side, and about 1 µm of a thick oxide film was formed.When a power generation test was conducted using Al BP coated with TiN-SBR, the cell voltage was increased significantly which was approached as similar as the performance of graphite. It indicates that Al can be used as bipolar plates without any problem by performing surface treatment in combination with a carbon channel forming material. Acknowledgements The authors thankfully acknowledge the financial support obtained from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. References Y. C. Park, S. H. Lee, S. K. Kim, S. Lim, D. H. Jung, S. Y. Choi, Int. J. Hydrogen Energy, 38, 10567–10576 (2013).S. F. Husby H, O. E. Kongstein, A. Oedegaard, Int. J. Hydrogen Energy, 2, 951–957 (2014).S. H. Lee, V. E. Pukha, V. E. Vinogradov, N. Kakati, S. H. Jee, S. B. Cho, Int. J. Hydrogen Energy, 38, 14284–14294 (2013).C.-H. Lee, Y.-B. Lee, K.-M. Kim, M.-G. Jeong, and D.-S. Lim, Renewable Energy, 54, 46–50 (2013).H. Yashiro, T. Ichikawa, S. -T, Myung, M. Kumagai and S. Kozutsumi, Zairyo-to-Kankyo, 60, 432–434, (2011).S.-T. Myung, M. Kumagai, R. Asaishi, Y.-K. Sun, H. Yashiro, Electrochem. Comm., 10, 480–484 (2008).

(Invited) Electrochemically Induced Deposition of Thin-Film Oxides and Electronic Insulators

Electrodeposition is typically associated with the electroreduction of metal ions for the deposition of metals, alloys or semiconductors. Compounds can be electrodeposited when the metal ions form an insoluble compound upon change of its valence state at the electrode surface. A well-known example is the anodic deposition of MnO2, where aqueous solvated Mn2+ ions are oxidized to the insoluble Mn(IV) in acid sulfate solutions. Alternatively, the precipitation of a compound or oxide can be triggered by changing the local pH at the electrode by a suitable electrochemical reaction. The use of electrochemical formed base from so-called probase molecules has found applications in formation of oxides, phosphates but also organic materials such metal organic frameworks (MOFs). Nitrate was one of the first pro-bases suggested for the electrochemical precipitation of ZnO. An alternate electrochemical approach for depositing compounds and oxides is the electrochemical initiation of a sol-gel reaction first developed for the silica sol-gel process by Shacham et al. [1] During deposition, an electrode is submerged into a precursor solution followed by the application of a cathodic current. The chemical reaction is triggered by electro-generating the OH- catalyst that is required for the polycondensation of the silica precursor. Since this occurs near the surface, the method results in silica thin films deposited only on the electrode surface. Finally, also electro-polymerization can lead to thin insulating films. In this paper, several of these reaction paths will be explored. The initial stages of MnO2 electrodeposition are strongly dependent on the starting surface and determines the adhesion and attainable film thickness [2]. The relationship between (intentionally) introduced meso-porosity, growth rate and film thickness will be discussed. The poor electronic conductivity of oxides makes that the reaction is maintained by ionic conduction through the films, similar as for oxide formation by anodization. For the formation of micron thick oxide films, also good control of hydrodynamic conditions is essential. [3] The resistive nature of the layers typically allows also for good conformality over high aspect ratio substrates. Conformal deposition of oxide thin-film coatings on high aspect ratio structures is typically claimed by Atomic Layer Deposition. Inorganic-organic hybrid films such as metal cones can be similarly deposited by Molecular Layer Deposition (MLD). [4] The nature of the surface limited reactions of these vapor-phase methods allows for the formation of continuous sub-nanometer to a few tens of nanometer thin films with uniform thickness over the most complex architectures. The accuracy of the technique goes at the cost of long deposition cycles especially when very large surface areas with extreme aspect ratios (>100) are involved. The intrinsic resistive nature of the electrodeposited oxide and insulator films allows for excellent conformal coatings with growth rates much more suited for thicker films without loss in conformality or uniformity. In this paper, we will show examples where electrochemical induced deposition process are used also to coat nano-architectures such as our nanomesh with very large surface area (100 cm2 per planar cm2) and aspect ratio (100x). [1] Shacham, B. R., Avnir, D. & Mandler, D. Electrodeposition of Methylated Sol-Gel Films on Conducting Surfaces. Adv. Mater. 384–388 (1999).[2] "Electrodeposition of Adherent Submicron to Micron Thick Manganese Dioxide Films with Optimized Current Collector Interface for 3D Li-Ion Electrodes" Marina Timmermans, Nouha Labyedh, Felix Mattelaer, Stanislaw Zankowski, Stella Deheryan, Christophe Detavernier, and Philippe M. Vereecken, J. Electrochem. Soc. 164, 14, D954-D963 (2017).[3] Aggregate-Free Micrometer-Thick Mesoporous Silica Thin Films on Planar and Three-Dimensional Structured Electrodes by Hydrodynamic Diffusion Layer Control during Electrochemically Assisted Self-Assembly”, G Vanheusden, H Philipsen, SJF Herregods, PM Vereecken, Chemistry of Materials (2021).[4] “Molecular Layer Deposition of "Magnesicone", a Magnesium-based Hybrid Material" Jeroen Kint, Felix Mattelaer, Sofie S. T. Vandenbroucke, Arbresha Muriqi, Matthias M. Minjauw, Mikko Nisula, Philippe M. Vereecken, Michael Nolan, Jolien Dendooven, and Christophe Detavernier, Chem. Mater. 32, 11, 4451–4466, (2020).

Influence of Annealing on Physical, Physiological and Electric Properties of Mono Nickel oxide Thick Films Prepared by using Screen-Printing Technique

To study changes in physical, physiological and electrical properties of AR grade Nickel monoxide (NiO), thick films of NiO were fabricated on a glass substrate and annealed at 250 0C - 400 0C. Using characterization techniques, such as XRD, SEM-EDS and static gas sensing system, the structure of the film was found to be polycrystalline with a cubic structure and chemical composition study confirmed its non- stoichiometric nature. Half bridge method is used for measurement of D.C. resistance of thick films in air atmosphere at 30 0C to 350 0C. The prepared thick films of NiO nanoparticles were analysed for electrical properties and it ascertained that they are semiconducting in nature. The TCR, activation energy as well as film resistivity were measured at selected annealing temperatures. The D.C electrical conductivity results obtained from electrical properties at room temperature is 0.086 × 104 (Ωm) 1. The crystallite size changes from 8.20 nm to 8.54 nm for strong predominant orientation (200) with increase in annealing temperature. Study of correlation between annealing temperature and electrical resistivity showed that there is decrease in resistance with increase in temperature.

Macroporous Vanadium Oxide Ion Storage Films Enable Fast Switching Speed and High Cycling Stability of Electrochromic Devices.

Compared to the significant effort dedicated toward developing efficient electrochromic materials for the working electrodes of electrochromic (EC) devices, the attention paid to developing ion storage counter electrode materials for EC devices has been trivial. Herein, we report that a macroporous crystalline V2O5 film as an ion storage layer paired with a WO3 working electrode results in an EC device with high performance. The macroporous vanadium oxide films are prepared by a simple template-free photodeposition method that allows us to tune the thickness and crystallinity of the film, thus giving access to a full EC device with optimal EC performance: short response time of about 2 s, high electrochromic cycling stability up to 10,000 times, long memory effect over 24 h, and an exceedingly high coloration efficiency of 189 cm2/C that are superior to the state-of-the-art performance of solution-processed vanadium oxide based EC devices. The extraordinary EC performance can be attributed to the macroporous structure, high crystallinity, and optimized thickness of the vanadium oxide films that boost the charge-balancing capability of the films. The easy and controllable preparation and the efficient charge-balancing capability of the macroporous vanadium oxide film make it a promising ion storage material for developing high-performance EC devices.

Fabrication of a reflective polarization wavelength filter via anodization of a Ti grating film.

A reflective-type polarization wavelength filter was fabricated by anodizing a Ti grating film. This polarization filter consisted of a Ti film, an anodized titanium oxide film (thickness ∼25nm), and a photoresist grating with a pitch of 410 nm. The reflectance was less than 10% for both polarizations at 490-675 nm at an incident angle of 9°. In addition, the transverse electric (TE) reflectance of the fabricated element was over 40%, whereas the transverse magnetic (TM) reflectance was 25.8% at 375 nm. Upon increasing the incident angle to 75°, the TE reflectance increased to 77.8% at 375 nm, whereas the TM reflectance decreased to 5.9%.

Influence of non-uniform feature of thermally grown oxide thickness on the local stress state and cracking behavior in TBC

The growth of thermally grown oxide (TGO) at high temperatures is the main reason for inducing the cracking near the YSZ/bond coat interface in the thermal barrier coating (TBC). The non-uniform thickening of TGO can change the local stress state and crack evolution. In this work, a TBC model including non-uniform TGO is established to explore the effect of non-uniform feature of TGO on the local cracking behavior. The continuous growth of TGO is simulated by applying a stress-free strain. The arbitrary path propagation of cracks in YSZ and TGO is realized by the XFEM method. The influences of TGO non-uniform degree and lateral growth rate on the stress variation and crack evolution are discussed. The results show that the non-uniform growth of TGO increases the local oxide film thickness and decreases the amplitude of TGO/bond coat interface, which leads to a greater crack driving force than TGO uniform growth. The increase of TGO non-uniform degree will induce longer TGO crack. The coating life predicted by the uniform TGO model is overestimated. The increase of TGO lateral growth strain leads to the improvement of YSZ crack driving force and TGO crack length, which is independent of TGO non-uniform degree. The results in this study indicate that obtaining uniform TGO with a low growth rate by process optimization will be an important option to improve the durability of TBC.

Influence of Ammonia on the Corrosion Behavior of a Zr–Sn–Nb Alloy in High Temperature Water

Corrosion behaviors, microstructures of oxide films, and hydrogen absorptions of a Chinese domestic Zr alloy in 6.7 × 10−3 mol/L ammonia solution and 2.9 × 10−4 mol/L LiOH+9.3 × 10−2 mol/L H3BO3 solution at 360 °C, 18.6 MPa were studied. Weight gains, oxide film thicknesses, and hydrogen absorptions showed that the corrosion rate in the ammonia solution is a little higher than that in the boron–lithium solution. There is no significant difference in the microstructure and crystalline structure between the oxide films formed in the two types of solutions. The element distributions along the depth direction of the oxide films showed the existence of nitrogen in the oxide film formed in ammonia solution. Moreover, nitrogen was found to be segregated in local areas in a range of about 2 μm from the oxide/metal interface. The corrosion behavior of the Chinese domestic Zr alloy in 360 °C aqueous solution shows no difference with other Zr alloys.

Corrosion behavior of T91 steel in liquid lead-bismuth eutectic at 550 °C: Effects of exposure time and dissolved oxygen concentration

Long-term corrosion behavior of T91 steel was investigated in 550 °C static liquid lead-bismuth eutectic (LBE) at different dissolved oxygen (DO) concentration. It was found that the oxide film formed in the oxygen-saturated LBE consists of iron-lead composite oxide, Fe3O4, Fe-Cr spinel and an inner oxidation zone (IOZ). The IOZ is composed of matrix and FeCr2O4 which follows orientation relationships with the matrix. The thickness of oxide film significantly reduces at DO= 1.26 × 10−6 wt %. Dissolution corrosion and intergranular penetration of Pb-Bi were observed at DO≤ 1.41 × 10−8 wt %. The corrosion mechanism of T91 steel in liquid LBE is discussed.

Effect of the oxidation reaction interface on the accelerated corrosion behaviour of Al–Mg–Si alloy

ABSTRACT Oxide films for Al–Mg–Si alloys with various aluminium oxide contents from 65.99 to 80.97% and thicknesses ranging from 1.7 to 5.1 μm were obtained. The effect of the oxidation reaction interface on the accelerated corrosion behaviour of Al–Mg–Si alloy has been investigated by using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electron probe microanalyzer (EPMA), accelerated corrosion tests and electrochemical tests. Accelerated corrosion tests indicated that incomplete oxide films reduced the corrosion resistance even with increasing oxide film thickness and Al2O3 content in a solution containing 30 g L−1 NaCl and 10 mL HCl (ρ = 1.19 g mL−1). The thicker oxide film effectively inhibited corrosion behaviour, while the thinner oxide film disappeared and its substrate suffered corrosion after immersion for 6 h, corresponding to the dissolution of oxide film and shedding of second-phase practices on interfaces. Accelerated corrosion response of various oxidation reaction interfaces was built by an equivalent electrochemical circuit.

A step towards a better understanding of corrosion of zirconium in nitric acid with additions of fluorine: Focus on the role of the presence of an initial oxide film

The presence of fluorine is known to drastically reduce the corrosion resistance of zirconium in nitric acid. Nevertheless corrosion processes involved for this system appear controversial, especially concerning the role played by the initial oxide film (ZrO2) that can naturally be formed in nitric acid. To study the contribution of the initial oxide film, zirconium samples were pre-oxidized in several ways so as to obtain different thicknesses of the initial oxide film. Then, the corrosion evolution of these samples was studied in nitric acid with fluorine additions. It appears that the initial oxide film present on surface plays a protective role for corrosion. But as the oxide film slowly dissolves, this protective role may only be transitory (depending on the thickness of the initial oxide film). When the oxide film has been sufficiently dissolved, it breaks by a process of initiation, growth and coalescence of pits. Zirconium is then directly attacked by fluorine and its corrosion rate increases largely. After the complete vanishing of the initial oxide film, corrosion becomes uniform and the corrosion rate decreases slowly: the corrosion process is limited by the diffusion and the consumption of fluorine.