Oxide Layer Research Articles

Effect of irradiation on the corrosion of 304 stainless steel in pressurized water reactor (PWR) simulated water chemistry

In this study, the corrosion behavior of pre-ion-irradiated 304 SS is compared to that of un-irradiated 304 SS in simulated Pressurized Water Reactor (PWR) conditions for both early stages of corrosion and longer exposure times. Transmission electron microscopy is used to characterize the oxide scale. The study shows that although the pre-irradiated microstructure does not change the nature of the oxide and its dual-layer structure (i.e. inner/outer oxide layers) formed on 304 SS, the path of growth of the inner oxide layer is affected by the irradiated microstructure resulting in oxide protrusions into the matrix; a mechanism is proposed.

Multi-layer formation by oxidation and solid-state crystallization of cold sprayed amorphous coatings during dry sliding wear

Amorphous alloy coatings, known for the exceptional wear resistance, have emerged as a key solution for enhancing the wear performance of magnesium alloys under harsh environments. In this study, Fe-based amorphous alloy coatings were deposited on magnesium alloy by cold spraying technology, and the influence of microstructural evolution on the wear performance of coatings under dry sliding wear conditions was discussed. The results showed that a dense adherent oxide layer with a thickness of ∼700 nm comprising nanograins of less than 8 nm was formed at the outmost surface, which played a role of self-lubricating. Underneath, a 1 μm thick nanocrystalline-amorphous layer with nanograins of ∼20 nm dispersed in the amorphous alloy matrix was formed through in-situ crystallization induced by flash temperature. This composite structure prevented the formation of shear bands in amorphous alloys and enhanced the durability. Therefore, the transition from abrasive wear to adhesive wear was a consequence of the microstructural evolution from a dual-phase composite layer to a self-lubricating oxide layer.

THE OXIDATION-RESISTANT Mo30Si60B10 COATING FOR PROTECTION OF THE T2 PHASE-BASED MOLYBDENUM ALLOY

This study focuses on fabrication of a Mo30Si60B10 coating with elevated silicon content, which enhances working properties of Mo-alloy based on the Т2 phase (t-Mo5SiB2). The Mo30Si60B10 coating has a columnar structure. The alloy is characterized by hardness of 17 GPa; Young’s modulus of 304 GPa, and elastic recovery of 29%. Deposition of the coating increased hardness by 40%; the Young’s modulus, by 18%; and elastic recovery, by 25%. Oxidation tests at 1200°C demonstrated that the specific mass loss of the alloy with Mo30Si60B10 coating was 1.5-fold lower than that of the uncoated alloy. An 18 μm thick oxide layer based on a-SiВO and containing MoO2 particles was formed on the alloy surface. The coating contributes to a ∼14-fold reduction of oxide layer thick. The increase in oxidation resistance of alloy after coating deposition is related to sealing of substrate defects and formation of an a-SiВO layer with elevated silicon content.

Ablation-resistant yttrium-modified high-entropy refractory metal silicide (NbMoTaW)Si2 coating for oxidizing environments up to 2100 °C

Refractory high-entropy alloys (RHEAs) are pivotal in ultra-high temperature applications, such as rocket nozzles, aerospace engines, and leading edges of hypersonic vehicles due to their exceptional mechanical ability to withstand severe thermal environments (in excess of 2000 °C). However, the selection of materials that satisfy the stringent criteria required for effective ablation resistance remains notably restricted. Here, a novel yttrium-modified high-entropy refractory metal silicide (Y-HERMS) coated on a refractory high-entropy NbMoTaW alloy is developed via pack cementation process. The developed Y-HERMS coating with sluggish diffusion effect demonstrates extraordinary ablation resistance, maintaining near-zero damage at sustained temperatures up to 2100 °C for a duration of 180 s, surpassing state-of-the-art high-performance silicide coatings. Such exceptional ultra-high ablation performance is primarily ascribed to the in-situ development of a high viscosity Si-Y-O oxide layer with increased thermal stability and the presence of high-melting Y(Nb0.5Ta0.5)O4 oxides as skeleton structure. Theoretical results elucidate that the Y-HERMS promotes the formation of SiO2, which impedes the diffusion of O into metal silicide layer, synergistically contributing to the superior ablation resistance. These findings highlight the potential of utilizing high-entropy materials with excellent ablation resistance in extreme thermal environments.

Process optimization and tribological behavior of Ti-48Al-2Cr-2Nb prepared by selective electron beam melting

Selective electron beam melting (SEBM) technology was utilized to fabricate TiAl alloys which possess low density and excellent high-temperature performance, to achieve lightweight design of automotive engines. The forming process of Ti-48Al-2Cr-2Nb was systematically optimized, and found that the microstructure of TiAl formed by SEBM consisted of a layer of alternating γ-band structure and duplex-like structure. As the energy density increases, grain coarsening, proportion increasing of high angle grain boundaries, and anisotropy strengthening occur successively. The forming quality of TiAl reaches its peak at an energy density of 22.5 J/mm3, at which point its mechanical properties and wear resistance also perform the best. Subsequently, in-depth friction experiments at high and room temperatures were conducted, and it was found that at room temperature, as the load increased, the friction coefficient of the samples decreased and the wear rate increased. In addition, the friction coefficient decreases from 0.54 to 0.44, while the wear rate increases from 19.90×10−5 mm3/(N·m) to 25.97×10−5 mm3/(N·m). At this point, abrasive and adhesive wear were the main wear mechanism. Under high temperature conditions, the wear mechanism of the substrate is mainly abrasive wear, adhesive wear, and oxidative wear. And the friction coefficient decreases from 0.69 to 0.49. At lower temperatures, the detached debris was filled and solidified on the wear marks under the action of the friction ring, forming a hardened layer called “enamel”, which can alleviate the negative effects of wear. Under the influence of extreme high temperature environment, the unworn surface forms a light blue oxide film due to rapid oxidation, known as the “burning blue” phenomenon. Along with the high-temperature oxidation phenomenon confirmed by EDS, the oxide layer is more prone to peeling off and forming debris. In addition, melting softening occurs inside the annular wear scar, which increases the amount of deformation under external force, ultimately leading to a significant increase in wear.

Comparison of oxidation resistance of high-entropy (Ti0.2Zr0.2Hf0.2Ta0.2Nb0.2)C/SiC composites prepared by different methods at 1300–1600 °C

Dense monolithic (Ti0.2Zr0.2Hf0.2Ta0.2Nb0.2)C/SiC (HEC/SiC) composites were prepared via single-source-precursor (SSP) and solid-state reaction (SSR) method, respectively. The SSP-method nanocomposite features HEC nanoparticles uniformly dispersed within β-SiC, while the SSR-method composite is a microcomposite containing micro-sized HEC and β-SiC particles. The oxidation tests at 1300–1600 ºC show that the HEC/SiC nanocomposites exhibit much better oxidation resistance than that of the HEC/SiC microcomposites. Firstly, the generated metal-containing complex oxides ((Zr,Hf)6Ta2O17, Ti(Ta,Nb)2O7, and Ta-doped rutile TiO2) become more facile for sintering due to the nano-scaled HEC phase. Secondly, the cracks resulting from the oxidation of HEC nanoparticles are fewer and smaller, decreasing the number of channels for oxygen to pass through and channels need to be healed by SiO2. Finally, the homogeneous distribution of the HEC nanoparticles within β-SiC ensures the homogeneity of the complex oxide layer, significantly reducing the cracks caused by volume expansion and preventing the oxide layer from peeling off.

Tuning the toughness, strength, and biological properties of functionally graded alumina/titania-based composites for use in bone repair applications

In this study, functionally graded composite (FGC) was prepared using a high-energy ball mill by fabricating five layers of alumina (Al2O3), titania (TiO2), hydroxyapatite (HA), and iron oxide (Fe3O4), which were sintered at 1100 °C to create an FGC sample. Scanning electron microscopy (SEM), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and weight loss measurements were used to assess bioactivity and biodegradation after immersing samples in simulated body fluid (SBF). Also, the antimicrobial activity and biocompatibility of these layers were evaluated. Furthermore, their electrical, dielectric, and mechanical properties were examined. The results revealed that all sintered layers were bioactive, and adding HA and Fe3O4 enhanced this desired property. Also, S. aureus bacterial growth was inhibited by TiO2 and Fe3O4. Fortunately, the sintered layers showed no cytotoxic effect, validating the ICP findings that demonstrated acceptable biodegradation. Adding HA and Fe3O4 enhanced fracture toughness in another hopeful outcome, which is crucial for biomaterial efficacy and long-term therapeutic success. Moreover, the compressive strength of all the layers and the FGC sample was 191.7, 182.2, 171.18, 159.8, 142.5, and 171.1 MPa. Layers 3, 4, and 5 notably had a compressive strength similar to cortical bone. This means that implanting these layers into human bone will protect the bone around them from stress-shielding action. Finally, the successive increase in HA/Fe3O4 contents increased the electrical conductivity. Accordingly, the prepared FGC sample and its layers are attractive bone substitute materials.

The structural, mechanical, optical and dielectric properties of aminated PMMA-Ag-GO nanocomposite for coatings

The present study reports the synthesis and characteristics of an aminated PMMA-Ag-GO polymer nanocomposite (PNGAg) for coatings. The XRD diffractogram data indicated the presence of crystallinity in samples. The lattice strain of (002) planes and crystallite size were computed to estimate the number of graphene oxide (GO) layers. The homogenous dispersion of GO with silver (Ag) nanoparticles over the surface of the samples was verified by the SEM and EDAX tests. The thermal stability and interaction of fillers with aminated PMMA is confirmed by of TGA–DTA and FTIR analysis. Moreover, the substantial shift of FTIR bands supports the bonding of functional groups with Ag decorated GO and the stability of nanocomposite. The estimated mechanical properties like flexural strength and composite modulus (> 90 MPa) supported the applicability of PNGAg as coatings. The UV-Vis spectroscopy evidenced the characteristic absorption peaks of GO in line with range of UVC radiation in aminated PMMA. Along with high values of relative permittivity, the shift of loss tangent maxima to higher end with increase in GO concentration is attributed to greater number of interfaces. Owing to the functionalisation by naproxen along with dispersion of GO, contributed to MWS polarisation and hence strengthen the dielectric properties. As the concentration of GO rises from 0.1 mol% to 0.7 mol%, substantial shift of AC conductivity (i.e 2.49 × 10−6 Scm−1 to 37.9 × 10−6 Scm−1) is observed. The high conductivity of PNGAg5 at 0.9 mol% GO suggests the presence of numerous layers, leading to increased interfacial polarization and a higher dielectric constant. In addition to that, the semi-circle in impedance plot and bulk resistance also supported the optimal dielectric properties of samples. As a whole, the results have shown that PNGAg nanocomposites are good coating materials for wide variety of devices.

Disentangling different interfacial effects of reduced thin layer magnetizations

Abstract Thin buried magnetic layers ranging from thicknesses of a few atomic monolayers to several nanometers are omnipresent in the fields of magnetism and spintronics. For the functionality and fine tuning of devices build with such layers, exact knowledge of the depth dependent magnetic properties is essential. Especially the interfacial magnetic properties are important. Hence, understanding how magnetism is affected by structural variations, such as thickness or interface roughness, is mandatory. In this study, we use x-ray resonant magnetic reflectometry and magnetometry to study the high-resolution depth dependent magnetization profiles of thin magnetic transition metal layers sandwiched between an oxide and chromium layer. Compared to bulk materials, the room temperature saturation magnetization of these layers is reduced by up to 67%. These reductions are extremely sensitive to small structural variations. From the magnetic depth profiles, we disentangle different effects contributing to the magnetization reduction and the exact magnetic properties of the interface.

Study of endogenous chloride ion content on the behavior of steel bar depassivation in sea sand concrete

In this study, we investigated the chloride concentration in sea sand that induces corrosion in steel bars, as well as the corrosion mechanisms of steel bar within sea sand concrete. Different analytical techniques indicated that the chloride concentration for steel bar corrosion in sea sand concrete was 0.03% (when the water-binder ratio was in the range of 0.4∼0.6). First, the calcium silicate in sea sand concrete reacted with Fe3+ to reduce the compactness of the oxide layer and increase the corrosion risk of steel bars. Second, as the water-binder ratio and chloride concentration gradually increased, the loose structure of the passive film increased, and the relatively dense structure decreased, which made it easier for chloride ions to penetrate the outer layer of the passive film to erode the steel matrix. Besides, the reaction of chloride ions with C3A to form Friedel's salt optimized the pore structure and reduced the content of free chloride ions. However, the adverse effect of chloride ions on the passive film of steel bars exceeded the beneficial impact of porosity reduction. These findings allow us to better apply sea sand to improve the sustainable development of environment.

Parametric Analysis of Indium Gallium Arsenide Wafer-based Thin Body (5 nm) Double-gate MOSFETs for Hybrid RF Applications.

The electrical behavior of a high-performance Indium Gallium Arsenide (In- GaAs) wafer-based n-type Double-Gate (DG) MOSFET with a gate length (LG1= LG2) of 2 nm was analyzed. The relationship of channel length, gate length, top and bottom gate oxide layer thickness, a gate oxide material, and the rectangular wafer with upgraded structural characteristics and the parameters, such as switch current ratio (ION/IOFF) and transconductance (Gm) was analyzed for hybrid RF applications. This work was carried out at 300 K utilizing a Non-Equilibrium Green Function (NEGF) mechanism for the proposed DG MOSFET architecture with La2O3 (EOT=1 nm) as gate dielectric oxide and source-drain device length (LSD) of 45 nm. It resulted in a maximum drain current (IDmax) of 4.52 mA, where the drain-source voltage (VDS) varied between 0 V and 0.5 V at the fixed gate to source voltage (VGS) = 0.5 V. The ON current(ION), leakage current (IOFF), and (ION/IOFF) switching current ratios of 1.56 mA, 8.49Í10-6 μA, and 18.3Í107 μA were obtained when the gate to source voltage (VGS) varied between 0 and 0.5 V at fixed drain-source voltage (VDS)=0.5V. The simulated result showed the values of maximum current density (Jmax), one and twodimensional electron density (N1D and N2D), electron mobility (μn), transconductance (Gm), and Subthreshold Slope (SS) are 52.4 μA/m2, 3.6Í107 cm-1, 11.36Í1012 cm-2, 1417 cm2V-1S-1, 3140 μS/μm, and 178 mV/dec, respectively. The Fermi-Dirac statistics were employed to limit the charge distribution of holes and electrons at a semiconductor-insulator interface. The flat-band voltage (VFB) of - 0.45 V for the fixed threshold voltage greatly impacted the breakdown voltage. The results were obtained by applying carriers to the channels with the (001) axis perpendicular to the gate oxide. The sub-band energy profile and electron density were well implemented and derived using the Non-Equilibrium Green's Function (NEGF) formalism. Further, a few advantages of the proposed heterostructure-based DG MOSFET structure over the other structures were observed. This proposed patent design, with a reduction in the leakage current characteristics, is mainly suitable for advanced Silicon-based solid-state CMOS devices, Microelectronics, Nanotechnologies, and future-generation device applications.

Oxidized textured stainless steel surface with passivation layer as a high temperature selective solar absorber

A nanocrystalline textured stainless steel (SS) surface passivated with an AlCr oxide layer is proposed for use as a high temperature solar selective absorbers (SSAs). The textured SS surface was prepared by oxidizing in air at 800 °C for 30 min. The heating resulted in outward diffusion of the SS substrate Mn atoms, their oxidation on the surface, and formation of octahedral Mn3O4 nanocrystals, which play a role of textured surface. The passivation AlCr oxide single layer was deposited on the textured surface using reactive RF magnetron sputtering to protect the SS from further oxidation. The solar absorptivity αs and thermal emissivity ε298K of the as-deposited SSAs were 0.84 and 0.165, respectively. In order to study high temperature stability, SSAs were heat treated under air conditions at 600-900 °C for 0.1-300 h. SSAs demonstrated thermal stability at 600 °C for at least 300 h and degradation of optical properties with performance criterion PC < 0.05 at 700, 800, and 900 °C for 300 h, 30 h, and 1 h, respectively. The increase in thickness of the surface Cr2O3 layer on SS substrate was identified as the main degradation mechanism of SSA optical performance. SSAs demonstrated a high activation energy of 330±30 kJ/mol. The obtained data can be used to design high temperature SSAs for concentrating solar energy systems operating under vacuum or air conditions at 500 °C.

Investigations on Cylindrical Surrounding Double-Gate (CSDG) MOSFET using AlxGa1-xAs/InP: Pt with La2O3 oxide layer for fabrication.

The Cylindrical Surrounding Double-Gate MOSFET has been designed using Aluminium Gallium Arsenide in its arbitrary alloy form alongside Indium Phosphide with Lanthanum Dioxide as a high-ƙ dielectric material. The heterostructure based on the AlxGa1-xAs/InP: Pt has been used in the design and implementation of the MOSFET for RF applications. Platinum serves as the gate material, which has higher electronic immunity toward the Short Channel Effect and highlights semiconductor properties. The charge buildup is the main concern in the field of MOSFET design when two different materials are considered for fabrication. The usage of 2 Dimensional Electron Gas has been outstanding in recent years to help the electron buildup and charge carrier accumulation in the MOSFETs regime. Device simulation used for the smart integral systems is an electronic simulator that uses the physical robustness and the mathematical modeling of semiconductor heterostructures. In this research work, the fabrication method of Cylindrical Surrounding Double Gate MOSFET has been discussed and realized. The scaling down of the devices is essential to reduce the area of the chip and heat generation. By using these cylindrical structures, the area of contact with the circuit platform is reduced since the cylinder can be laid down horizontally. The coulomb scattering rate is observed to be 18.3 % lower than the drain terminal when compared to the source terminal. Also, at x = 0.125 nm, the rate is 23.9 %, which makes it the lowest along the length of the channel; at x = 1 nm, the rate is 1.4 % lesser than that of the drain terminal. A 1.4 A/mm2 high current density had been achieved in the channel of the device, which is significantly larger than comparable transistors. The conventional transistor occupies a larger area than the proposed cylindrical structures transistor and is also efficient in RF applications.

LBE corrosion behavior of helium pre-irradiated martensitic steel

In the design of the spallation target of CiADS, T91 steel was selected for the most critical component, the beam window. A Si-modified martensitic steel (SIMP) has been currently developed, which has better corrosion resistance and is planning to replace T91 as a material of beam window in the future. In order to assess the effect of irradiation damage on the microstructure evolution and corrosion behavior of the SIMP, the pre-irradiated samples with irradiation doses from 5×1015 to 3×1017 He/cm2 exposed in static lead-bismuth eutectic (LBE) with saturated oxygen at 350 °C for 4000 h were investigated. Results show that pre-irradiation neither change the double-layer structure of the oxide layer nor significantly affect the corrosion rate. This may be due to the slow diffusion of elements at low temperatures, and the low irradiation dose not reaching the threshold for triggering accelerated corrosion.

Dynamic splitting tensile mechanical behavior of magnesia-carbon refractories under impact loading

To enhance understanding of the dynamic tensile failure mechanism of MgO-C refractories, the Split Hopkinson Pressure Bar test combined with digital image correlation techniques were utilized. The dynamic failure behavior of specimens with different heat treatments and graphite content was investigated under various impact velocities. The MgO-C specimens exhibit severer damage and a more tortuous crack path with higher impact velocity. The SiC and forsterite phases generate during heat treatment are advantageous in inhibiting crack propagation, while the formation of oxide layer makes the material more susceptible to brittle fracture. Due to the presence of microcracks, high graphite samples lead to a reduction in tensile strength, but result in a wider fracture zone, which dissipates impact energy. Compared with the significant increase of strength under compressive impact loading, the critical tensile strain rate of MgO-C is easier to achieve after which the tensile strength decreases.

Boosting Corrosion Resistance of Mg-Li Alloy: Implanting Bioinspired Superhydrophobic Surfaces into MAO Matrix for Enhanced Protection

The corrosion problem has significantly impeded the practical application of Mg-Li alloys. In this report, a method that combines micro-arc oxidation (MAO) with electrochemical deposition is developed to create a superhydrophobic matrix on Mg-Li substrate. The combination approach harnesses the superiority of both coverages, including MAO as the dense, firmly bonded ceramic oxide layer on the metal substrate and the superhydrophobic surface (SHS) implanted into MAO matrix. The MAO-SHS coating exhibits high mechanical stability, maintaining the superhydrophobicity due to the “implanting effect” even after a long distance of friction effect. For corrosion inhibition, compared to the bare Mg-Li with icorr of 9.26 × 10-5 A/cm2, the icorr for MAO and MAO-SHS is 7.83 × 10-6 A/cm2 and 7.50 × 10-9 A/cm2, respectively, representing the reduction of approximately one and four orders of magnitude. Focusing the atmospheric corrosion inhibition, MAO-SHS proves to manipulate the dynamic evolution of saline solution evaporation and salt particle deliquation. The salt particle crystalized from saline solution on MAO-SHS is found to have significantly smaller contact area than that of the bare Mg-Li and MAO. By employing atomic force microscopy (AFM), the adhesion force of salt particle is revealed as ca. 45 nN, 13 nN, and 2 nN for salt particle on Mg-Li, MAO, and MAO-SHS, respectively. This suggests that the salt can be more easily removed from the MAO-SHS surface, thereby reducing the susceptibility to corrosion. The in situ deliquation is conducted to understand the formation of the droplet on different surfaces. The air in the SHS layer hinders chloride ingress and the SHS layer seals the pores in MAO layer, proving the synergistic effect afforded by MAO-SHS to achieve superior corrosion resistance.

Mid-infrared waveguide-integrated and photo-thermoelectric graphene photodetector based on germanium-on-silicon platform

Mid-infrared (MIR) photonic integration is desirable in the development of MIR spectroscopy and “lab-on-a-chip” sensing. The germanium-on-silicon (GOS) platform offers a promising solution for MIR photonic integration, extending the operational wavelength to a longer band by eliminating the light-absorbing buried oxide layer. However, MIR photodetectors on the GOS platform remain undeveloped due to the challenging heterogeneous integration of active materials on silicon and inadequate light absorption in the photodetection region. Here, we demonstrate a photo-thermoelectric graphene photodetector on the GOS platform, taking advantage of zero-bias operation and easy heterogeneous integration of graphene. By employing split-gate architecture and plasmonic enhancement to strengthen the light-graphene interaction, we achieve a responsivity of 1.97 V W−1 and noise equivalent power of 2.8 nW Hz−1/2 at the wavelength of 3.7 µm. This work enables waveguide-integrated MIR photodetection on the GOS platform for the first time, and it holds great potential for on-chip MIR sensing and imaging applications.

Oxidation of Sintered Refractory Alloy (Ni3Al)

Ni3Al is a superalloy which is of particular interest at high temperatures due to its high resistance to oxidation with the formation of a protective oxide layer that performs better than NiO and Cr2O3. Among the factors likely to affect the reaction mechanism and modification of the oxidation kinetics, the surface state appears to be a very important parameter. In the case of sintered materials, the surface condition will be linked to the porosity of the material and therefore to densification. This work essentially has two parts. The first consists of developing Ni3Al sinters intended for oxidation, studying the densification mechanisms and bringing together the results obtained by dilatometry at variable temperature and by differential thermal analysis which made it possible to demonstrate sintering in a reactive liquid phase extremely fast SHS type, with instantaneous formation of the Ni3Al phase. The second part is devoted to the isothermal oxidation between 1100 and 1350°C of cubic-shaped sinters (4mm edge) under a flow of oxygen for 24 hours. The shape of the parabolic curves is correlated with morphological and microstructural observations to deduce the diffusional kinetic regime which controls the speed of the reaction. On the other hand, these observations highlighted a very strong adhesion due to the indentations of the Al2O3 oxide in the metal at the oxide/metal interface. Various techniques (Density – XRD – SEM and Microanalysis) to characterize the sinters and the oxidation products complete our study.

Hierarchical design of self-standing FeNi-based metallic glass by in-situ surface amorphous oxide construction for durable and efficient oxygen evolution

As the driving force to accelerate water electrolysis in commercialization, electrocatalysts concurrently satisfying electrocatalytic activity, mechanical flexibility and low cost are essential in the design to lower the kinetic barriers of oxygen evolution reaction (OER). Herein, we present a strategy to in situ construct amorphous metal oxide layers on different compositions of self-standing non-precious FexNiyP20 (at.%) metallic glasses (AMO-MG). With the mechanical flexibility, the processed FexNiyP20 MGs, particularly at Fe30Ni50P20, reaches low OER overpotentials of 238 at a current density of 10 mA cm−2 and a Tafel slope of 33 mV dec−1 in 1.0 M KOH solution while preserving a long-term durability exceeding 60 h. Further studies indicate these robust OER activities appear to be directly linked with the unique surface patterns of the in situ formed AMO layer providing abundant active sites, low charge transfer resistance and superior structural-integration. Modelling analysis further shows that both Fe and Ni sites in AMO layer act as active sites leading to a strong charge transfer for effective H2O adsorption and an optimization of rate-determining step of OER process. Such in situ AMO-MG hierarchical structure therefore provides a novel structure-integration strategy and win–win situation to design and commercialize high-performance alloy catalysts for OER.

Hydrogen permeation in iron-chromium-aluminum (FeCrAl) alloys and the effects of microstructure and surface oxide

Iron–chromium–aluminum (FeCrAl) class alloys are candidates for use as cladding for accident-tolerant fuels and moderators. In this context, hydrogen isotope permeation in FeCrAl alloys is an important material property. In the present work, the apparent permeability, effective diffusivity, and apparent solubility of hydrogen in the FeCrAl alloys C26M and Kanthal D (KD) were measured with gas-driven hydrogen permeation. Permeation measurements were conducted at temperatures of 400 to 700 °C and at gas-driven pressures from 1 to 100 kPa. In particular, the effect of grain size on hydrogen transport was studied with KD samples with three different microstructures: nanocrystalline (NC), ultra-fine grained (UFG), and coarse-grained (CG). The UFG and NC specimens had higher apparent activation energies (73.4 kJ mol-1 and 65.2 kJ mol-l, respectively) for hydrogen permeability than the CG sample (46.9 kJ mol-1). An aluminum oxide layer formed on the primary- and secondary-side surfaces of all samples subjected to permeation experiments which demonstrated the propensity of FeCrAl alloys to form these innate oxide permeation barriers.