Oxide Layer Research Articles

Surface modification of rare earth elements to enhance the electrochemical stability of Ni-rich Co-free cathodes

The Ni-rich Co-free cathode materials are considered the most optimistic choice for the long-term economic development of lithium-ion batteries (LIBs) due to the limited supply and high prices of cobalt. In this study, a uniform samarium oxide (Sm2O3) layer was coated on the surface of LiNi0.8Mn0.17Fe0.03O2 (NMF) cathode materials through wet subsequent heat treatment. Compared with the unmodified cathode materials, the modified cathode materials exhibit better electrochemical performance at high voltage. The specific discharge capacity of the modified cathode materials increased from 37.5 mAh g−1 (NMF) to 118.2 mAh g−1 after 200 cycles at 1 C and the retention rate increased from 21.18% to 69.77%. The samarium oxide coating effectively inhibits the reaction between the cathode materials and the electrolyte. Therefore, our study proposes a simple and scalable method for modifying nickel-rich cobalt-free cathode materials.

Characterizing oxidation, thickness, and composition of metallic glass thin films with combined electron probe microanalysis and X-ray photoelectron spectroscopy

Metallic glass thin films (MGTFs) are a recently developed class of alloy coatings with potential applications ranging from biomedical devices to electrical components. Their tribological performance in service conditions is dictated by MGTF bulk composition but can be limited by the native oxide surface that inevitably forms upon exposure to atmosphere. Surface oxidation, thickness, and composition of ZrCuNiAl MGTFs were characterized using a combination of X-ray photoelectron microscopy (XPS) and electron probe microanalysis (EPMA). MGTF samples with nominal thicknesses of 50, 500, and 1500 nm were sputtered onto Si and SiN wafer substrates within a high vacuum deposition chamber and their amorphicity was confirmed by X-ray diffraction. XPS depth profiling identified the thin film composition and showed that the surface oxide was dominated by a mixed layer of mostly ZrO2, a little oxidized Al, and some metallic Zr. EPMA X-ray intensities were acquired as a function of beam energy to excite characteristic X-rays from different depths of the MGTFs and reconstructed using open-source thin film analysis software BadgerFilm, to determine the composition and thickness of sample layers. EPMA results constrain the composition to be Zr54Cu29Al10Ni7 within 0.7 at. % variation and total thicknesses to be 49, 470, and 1546 nm. Using the oxide composition identified from XPS depth profiling as an input for BadgerFilm analysis, EPMA results indicate the surface oxidation layer on each of the thin film samples was 6.5 ± 1.1 nm thick and uniform across a 0.25 mm region of the film.

Effect of the simultaneous addition of lanthanum and nickel on the oxidation behavior and related area-specific resistance of ferritic stainless steels for solid oxide fuel cell interconnects

The effects of simultaneous lanthanum and nickel addition on the oxidation behavior and area-specific resistance (ASR) of stainless steels for fuelcell interconnects were investigated. The La and Ni addition promoted the entire growth of the oxide layer and increased the roughness of the metal/oxide interface. Despite the thicker oxide scale, these alloys prevented the increase of ASR compared to the alloy with only Ni added. The void analysis indicated that simultaneous La and Ni addition could prevent void growth, leading to lower ASR. The above findings can be interpreted in terms of the fast La diffusion and convoluted metal/oxide interface.

In-vitro fretting tribocorrosion and biocompatibility aspects of laser shock peened Ti-6Al-4V surfaces

Laser shock peening without coating (LSPwC), a prospective surface modification technique for improving the mechanical aspects of Ti-6Al-4V alloy for automotive/aerospace sector, is also expected to dictate the efficiency of this material class for implant application. Here we unravel the impact of LSPwC on Ti-6Al-4V material surface characteristics, in-vitro tribocorrosion and biocompatibility. Micrography show the presence of nano and sub-micron sized pore after LSPwC process. The role of nano and sub-micron sized pores along with topography modification induced by LSPwC to serve as cues for controlling gene expressions, cell adhesion and activities offer novel insights in this research direction. A detailed X-ray photoelectron spectroscopy analysis detected local chemical non-stoichiometry with reduced number of oxygen diffusion channels. A crucial outcome of this oxide layer modification is the negative skewness (−0.55 ± 0.11) and reduced kurtosis (3.49 ± 0.14) of the surface, along with localized plastic deformation. These factors are correlated with the shift in potential during fretting tribo-corrosion from −800 to −250 mV after LSPwC, accompanied by a lower coefficient of friction of 0.4. Furthermore, the presence of well-spread cells and the up-regulation of beneficial genetic markers (Ki67) on LSPwC surfaces have the potential to form a better bone-material interface. The findings open new frontiers of the LSPwC-treated Ti-6Al-4V surface to synergistically modulate the tribocorrosion and biocompatibility aspects, with exciting possibilities for biomedical implants.

Oxidative corrosion resistance of a CrxFeyNi1-x-y composition spread alloy film (CSAF) in dry air

Composition Spread Alloy Films (CSAFs) were used to study the resistance to oxidative corrosion of CrxFeyNi1-x-y alloys in dry air and determine the critical Cr composition, xCr∗, necessary to prevent bulk oxidation. CrxFeyNi1-x-y CSAFs were made using physical vapor deposition (PVD) and then oxidized in dry air between 100 – 500 °C for periods of 1 h. A sharp passivation boundary was observed at 300 °C separating alloys showing evidence of heavy oxidation from Cr-rich alloys that were passivated. X-ray photoelectron spectroscopy (XPS) depth profiling was used to measure the extent of oxidation and penetration depth of the oxide layer on either side of the passivation boundary. XPS measurements confirmed the presence of a critical Cr composition, xCr∗, ranging from 18 to 26 at.%. For alloys with xCr≥xCr∗, a sufficiently thick passivating layer of oxidized Cr, Cr(ox), had formed on the top surface preventing the oxidative corrosion of either Fe or Ni. On the other hand, when xCr<xCr∗, bulk oxidation was observed, with appreciable Fe(ox) and/or Ni(ox) measured on the surface and often penetrating through the entire alloy film thickness. The trajectory of xCr∗ plotted within CrxFeyNi1-x-y composition space supports the trend towards using higher Cr-content stainless steel grades in harsh oxidative environments.

High-temperature ablation behavior and failure mechanism of (Hf0.25Zr0.25Ti0.25Ta0.25)C high-entropy carbide in wide temperature range

The ablation behavior of (Hf0.25Zr0.25Ti0.25Ta0.25)C was investigated using a plasma flame gun over a wide temperature range of 2070–2600℃. The structural transformation during ablation and the effect of temperature on the failure mechanism were discussed. Results showed a sharp increase in mass and linear ablation rates from 0.23 mg·cm−2·s−1 and 4.6 μm·s−1 at 2070℃ to 4.6 mg·cm−2·s−1 and 37 μm·s−1 at 2600℃. This variation was attributed to the temperature's impact on on the microstructure and composition of the oxide layer. During ablation, Hf/Zr-rich oxycarbides preferentially nucleated within the amorphous Hf-Zr-Ti-Ta-C-O layer, leading to phase separation of the oxide layer. With increasing ablation temperature, the filler and binder oxides with low melting point (e.g., (Hf,Zr)TiO4, TaZr2.75O8) were rapidly consumed. The skeleton oxides (e.g., (Hf,Zr)O2) failed to bond and peeled off. The transiently formed (Hf,Zr,Ti,Ta)Ox layer was repeatedly destroyed and reconstructed, resulting in the continuous damage and eventual failure of the matrix.

Nb speciation and microstructural characterization of the oxide layer formed on neutron-irradiated Zr-2.5 Nb alloy in high-temperature water

It is crucial to understand the degradation mechanisms of the alloy Zr-2.5Nb, which make the pressure boundary in Canada Deuterium Uranium reactors. In the present study, Zr-2.5Nb coupons were exposed for 567 days at 325 °C with and without neutron-irradiation in simulated primary water chemistry. A combination of scanning/transmission electron microscopy with energy dispersive X-ray spectroscopy, and electron energy loss spectroscopy was used to investigate the base metal and oxide. The obtained results suggest that the distribution of nanopores and the variation in Nb oxidation state likely create a gradient in the oxygen concentration and electrochemical potential through the film.

Atomic diffusion and electrical reliability of NiAl/SiO2 interconnect: Breakdown voltage and TDDB characteristics

This study reports the effects of post-annealing on the electrical reliability of a NiAl/SiO2 interconnect structure for potential use as post-Cu interconnect. Our materials characterization using transmission electron microscopy and secondary ion mass spectrometry discloses that annealing at elevated temperatures induced the diffusion of Al into SiO2: Al, for a 400 °C-annealed sample, diffused only to a few nanometers from the interface, forming a thin aluminum-rich oxide layer, while samples annealed at higher temperatures show an extensive Al diffusion and interfacial reactions. In a voltage ramp dielectric breakdown test, the 400 °C annealed sample shows the lowest breakdown voltage, possibly, due to the aluminum-rich oxide layer serving as a self-forming barrier while the samples annealed at higher temperatures display a drastic reliability degradation with the annealing temperature increasing. In addition, analyzing data acquired from time-dependent dielectric breakdown tests using the E-model helps us predict the lifetime of the 400 °C sample to be longer than 105 h at 1 MV/cm.

Microstructure and properties of oxide-reinforced FeCrAl matrix alloy manufactured by selective laser melting

In this work, nano-Y2O3 dispersed FeCrAl powders (NYD-Fe) were used to produce oxide dispersion strengthened (ODS) alloy by selective laser melting (SLM), and their microstructures and properties were investigated in detail by the kinds of characterization techniques. The results indicate that the Y2O3 particles adhered to the surface of FeCrAl powder absorb more laser, thus increasing the laser energy demand. High quality ODS deposits can be obtained at 600 mm/s and 180 W parameters. The ODS samples deposited by SLM exhibit coarse columnar grains with [001] texture. The Ti-rich nanoparticles and core-shell structured nanoparticles (Y- and O-rich core surrounded by a Ti-rich shell) are observed in ODS alloys. The precipitation formation of core-shell structured nanoparticles involves ball milling amorphization and dissolution reprecipitation. The ODS-180 alloy exhibits a higher ductility compared to FeCrAl-180 alloy, which is caused by the cellular structure with high density dislocations and the nano-sized precipitates inhibit the dislocation motion. The wear rate of the ODS-180 alloy is 51% lower than that of FeCrAl-180 alloy, which is mainly ascribed to the hardness and interface oxide layer resulting from its specific microstructural features.

Enhancing wear resistance of laser-clad AlCoCrFeNi high-entropy alloy via ultrasonic surface rolling extrusion

The AlCoCrFeNi high-entropy alloy (HEA) coating was synthesized by laser cladding and subsequently processed by ultrasonic surface rolling extrusion (USRE) with varying static loads of 100 N, 200 N, and 300 N. This study aimed to explore the effects of static load on the microstructure, mechanical properties, and tribological characteristics of the coatings. The findings indicate that increased static load results in the precipitation of martensitic phases, grain refinement, enhanced microhardness, and an elevated dislocation density. Specifically, after USRE with 300 N static load, the coating's microhardness reaches 753 HV, 1.4 times greater than the un-USRE coating. This enhancement is attributed to the synergistic effect of martensite phase transformation, grain refinement, and dislocation strengthening. The volume wear rate of the coating decreases to 1.31 × 10−4 mm3·N−1·m−1 following USRE at 300 N, demonstrating superior resistance to abrasive wear due to the high microhardness. Besides, the high-density dislocations facilitate rapid migration and diffusion of oxygen elements, thereby enhancing the oxide layer's protective properties and improving the coating's resistance to oxidation wear.

Ball-milled biochar-modified zero-valent aluminum activates peroxodisulfate for phenol degradation: Enhancement of catalysis by membrane-breaking effect

Zero-valent aluminum (ZVAl) is a potential activator for peroxodisulfate (PDS), yet the dense oxide film on its surface hampers electron transfer for the O−O bond cleavage of PDS. We synthesized zero-valent aluminum-biochar (BM-ZVAl@BC) composites through ball milling, which effectively disrupted the native oxide layer on BM-ZVAl@BC. Within the BM-ZVAl@BC/PDS system, biochar (BC) not only suppressed the rapid oxidation of BM-ZVAl@BC but also enhanced the dispersion and electron transfer rate of ZVAl, thereby improving the overall catalytic efficiency. Consequently, the phenol removal efficacy in the BM-ZVAl@BC/PDS system was notably improved. Optimal catalytic performance of the prepared BM-ZVAl@BC was achieved at a charcoal-to‑aluminum mass ratio of 2:1, resulting in 95.7 % phenol removal after 180 min. Quenching experiments and electron spin resonance (ESR) analysis revealed that both free radicals (SO4•−, •OH, and O2•−) and non-radical species (1O2) contributed to phenol degradation, with SO4•− and •OH playing predominant roles. In summary, the BM-ZVAl@BC/PDS system represents an effective and promising technology for the remediation of phenolic water pollutants.

Enhanced microwave absorption and corrosion resistance of carbonyl iron encapsulated by silicone modified epoxy resin

The novel silicone modified epoxy resin (ER) was synthesized and used to encapsulate the carbonyl iron powders (CIP) with core–shell structure by in-situ polymerization method. The silicone modified epoxy resin coating was introduced to enhance both microwave absorption and corrosion resistance of carbonyl iron. Microstructure analysis demonstrated that CIP were densely covered with ER shell. Hydroxyl (–OH) and amino group (–NH2) present in silicone-modified epoxy resin, and chemically interact with the metal oxide layer on carbonyl iron to form covalent bonds or hydrogen bonds, improving interfacial adhesion and uniform dispersion of CIP. The ER shell effectively strengthens the microwave absorption ability and corrosion resistance of CIP. The reflection loss peak reached − 52.1 dB and effective absorption bandwidth achieved 7.8 GHz (10.2 GHz − 18 GHz). The epoxy resin coating significantly reduced the charge transfer resistance (Rct) and corrosion current density (Jcorr), indicating improved corrosion protection. Polarization resistance (Rp) and corrosion rate (CR) analysis further verified corrosion resistance. The epoxy resin-coated CIP exhibit excellent microwave absorption and corrosion resistance, indicating widespread application in anti-electromagnetic interference field.

Unveiling the feature of deposition of oxygen and water molecules on the zirconium surface: A molecular dynamic study

Unveiling the feature of deposition of oxygen and water molecules on the zirconium surface at microscale is crucial during the initial stages of zirconium oxide layer formation in Pressurized Water Reactors (PWRs) or Light Water Reactors (LWRs). In this work, we use molecular dynamic simulations to study the feature of deposition of oxygen and water molecules on the zirconium surface. A special focus of this work is a formula our built for the number of atoms adsorbed by the metal surface at the considered moment of time. The results show that the surface density of atoms for the crystallographic plane (10-10) in is 3 times greater than that for the crystallographic plane (11-20). The effective surface density σ(10-10) for the crystallographic plane (10-10) is greater than the similar value σ(11-20) for the crystallographic plane (11-20). Furthermore, in a sufficiently wide range of temperatures, the mechanical properties of zirconium crystals during tensile deformation are practically independent of the diffusion of oxygen atoms along the grain boundaries. This distinct feature may be providing basis understanding for the experimental puzzle of oxidation rate of zirconium alloys.

Nanostructured Yb2SiO5/mullite-SiC/Si environmental barrier coating with long-term stability at 1250 °C

In this work, nanostructured Yb2SiO5/mullite-SiC/Si environmental barrier coatings (EBCs) were prepared to investigate the effect of heat treatment on the microstructure and phase transition of nanostructured Yb2SiO5/mullite-SiC/Si coatings. The Yb2SiO5 content and microstructure evolution in the coatings were thoroughly analyzed before and after heat treatment. The results demonstrate a slight decrease in the porosities of nanostructured Yb2SiO5 and mullite-SiC coatings, accompanied by a gradual growth in grain sizes with increasing heat treatment time, indicating the nanostructured EBCs show good resistance to sintering. Moreover, the thickness of thermal growth oxidation layer is only 200 nm at 1250 °C for 500 h of heat treatment. In particular, the presence of the Yb2O3 phase has been observed to exert a favorable influence on the thermal stability of nanostructured EBCs. This work provides an innovative strategy for designing advanced EBCs with excellent high-temperature thermal stability.

Construction of Fe-based amorphous active surface microenvironment and its synergistic Fenton-like treatment of organic pollutants

Fe-based amorphous materials with the superiorities of high efficiency and low Fe sludge secondary pollution can be seen as a potential alternative to Fenton catalysts. However, catalyst deactivation on the catalyst surface hinders the sustainability of high degradation activity. In this study, the degradation capabilities of FeBCCr amorphous alloys in methylene blue (MB) solution by Fenton-like method were explored. The optimum (Fe81B10C9)99Cr1 ribbon with a more uniform Fe3B-like amorphous structure, which exhibits a thin and easily-peeled oxide layer, provides unique dynamic self-renewing to obtain excellent efficiency and recyclability. The degradation rate with 0.05 g/L (Fe81B10C9)99Cr1 ribbon reached 0.248 min−1 and the recyclability reached a charming record of over 90 times with a dosage of 0.1 g ribbon. The activation energy of (Fe81B10C9)99Cr1 ribbon (12.97 kJ mol−1) was found to be superior to that of most metallic catalysts. More importantly, the boron-rich film in the interfacial region can both retard further oxidation of iron and provides a channel for electron transmission, which can contribute to the persistence of a highly active microenvironment with more Fe(Ⅱ) sites and highly utilization of H2O2. The limit segmentation method has verified the good performance in both heterogeneous and homogeneous reactions. This study introduces a strategy for designing high-performance non-noble metallic catalysts through cluster structure regulation, which provides a novel Fenton-like amorphous material with long recyclability of high degradation activity for water remediation.

High sensitivity in quantitative analysis of mixed-size polystyrene micro/nanoplastics in one step

As emerging environmental pollutants, microplastics (MPs) and nanoplastics (NPs) pose a serious threat to human health. Owing to the lack of feasible and reliable analytical methods, the separation and identification of MPs and NPs of different sizes remains a challenge. In this study, a hyphenated method involving filtration and surface-enhanced Raman spectroscopy (SERS) for the separation and identification of MPs and NPs is reported. This method not only avoids the loss of MPs and NPs during the transfer process but also provides an excellent SERS substrate. The SERS substrate was fabricated by electrochemically depositing silver particles onto the reduced graphene oxide layer coated on stainless steel mesh. Results show that polystyrene (PS) MPs and NPs are efficiently separated on the SERS substrate via vacuum filtration, resulting in high retention rates (74.26 % ± 1.58 % for 100 nm, 80.50 % ± 2.67 % for 500 nm, and 97.73 % ±0.11 % for 5 μm) and low limit of detection (LOD). The LOD values of 100 nm, 500 nm, and 5 μm PS are 8.89 × 10−5, 3.39 × 10−5, and 1.57 × 10−4 μg/mL, respectively. More importantly, a linear relationship for uniform quantification of 100 nm, 500 nm, 3 μm and 5 μm PS was established, and the relationship is Y = 225.61 lgX + 1076.36 with R2 = 0.980. The method was validated for the quantitative analysis of a mixture of 100 nm, 500 nm PS NPs, 3 μm and 5 μm PS MPs in a ratio of 1:1:1:1, which successfully approaches the evaluation of evaluated PS NPs in the range of 10−4–10 μg/mL with an LOD value of approximately 7.82 × 10−5 μg/mL. Moreover, this method successfully detected (3.87 ± 0.06) × 10−5 μg MPs and NPs per gram of oyster tissue.

New insights into oxidation mechanism and kinetics of 9Cr–1Mo ferritic-martensitic steel in oxygen-saturated liquid lead-bismuth eutectic

The evolution of oxide scales on a 9Cr–1Mo ferritic-martensitic steel (T91) in oxygen-saturated liquid LBE at 500 °C was investigated. While taken out at around 500 °C, the T91 steel, after corrosion, shows clean surface with little LBE adhesion due to the poor wettability induced by surface oxides, due to the formation of an oxide layer. The results reveal the evolution of surface oxides from irregular strip shapes to regular crystalline grains, and stack-packed equiaxed crystals in the outer magnetite layer. Thermally-induced cracks were captured in the oxide scale on T91 steel after 1,000h exposure to LBE. A new oxidation mechanism is proposed, with consideration of the formation of the outer layer by metal dissolution/oxide precipitation, and a thin film of chromium oxide at the inner/outer layers interface. The dependency of temperature and oxygen concentration on the oxidation kinetics of T91 steel in LBE at the present condition is discussed.

The Effect of Sulfuric Acid Anodization on the Electrochemical Properties of Aluminum Alloy AlSi10Mg Prepared by Selective Laser Melting

Aluminum alloy, AlSi10Mg, prepared by selective laser melt (SLM) fabrication was anodized in 9.8% sulfuric acid (Type II) at 15 V for a total of 23 min. Experiments were performed to study the potentiostatic anodization process and its effects on the oxide coating morphology, thickness, and electrochemical properties of the alloy. Prior to anodization, the alloy microstructure is composed of aluminum cells encapsulated in a silicon network. Anodizing the abraded and polished AlSi10Mg surface produced a porous oxide layer with a thickness of 5 μm. The oxide coating weight was 698 ± 29 mg/ft2. The oxide coating forms in the aluminum cells that are isolated from one another by the silicon eutectic phase. In electrochemical tests, the anodic and cathodic potentiodynamic polarization currents were suppressed by factors of 15× and 215×, respectively, as compared to the unanodized controls. The data indicate the anodic oxide coating suppresses the cathodic more than the anodic reaction rate. Linear polarization resistance (R p) values increased by 279× after anodization. The corrosion current density values (j corr) decreased by 133× after anodization. Taken together, the electrochemical data indicate the anodic oxide coating (unsealed) increases the corrosion resistance of the SLM alloy by two orders of magnitude.

Enhanced service performances of in-situ Mg-Sialon/MgAl2O4 folding structure in low carbon Al2O3–C refractories: Phase reconfiguration of nano-MgSiN2

The utilization of in-situ ceramic combination effectively addressed the issue of weak bonding at the interface in low carbon Al2O3–C refractories, enhancing the material service performances. In this study, nano-MgSiN2 synthesized from molten salt was utilized for incorporation of Al2O3–C refractories, as well as in assessment of mechanical properties, thermal shock stability, oxidation resistance and corrosion resistance. The findings demonstrate that the molten salt medium can lower synthesis temperature and decrease particle size of nano-MgSiN2. In addition, nano-MgSiN2 undergone phase reconfiguration at 1500 °C to form Mg(g) and Si3N4(s). The folding structure Mg-Sialon/MgAl2O4 were formed through phase reconfiguration of Mg(g) and Si3N4(s). This change enhanced interfacial bonding strength of Mg-Sialon/Al2O3 and MgAl2O4/Al2O3. The mechanical properties and thermal shock stability of refractories were enhanced by novel reconfiguration technology, resulting in CCS value of 176.9MPa. Simultaneously, Mg-Sialon transformation facilitated the interconnection of the oxide layer, enhancing oxidation resistance and corrosion resistance.

Effect of humidity on the friction and wear behavior of C/C-CuNi composites

The friction behavior and wear performance of C/C-CuNi composites under varying humidity conditions were investigated. Lower levels of humidity (30 %–50 % RH) resulted in the formation of a lubrication layer composed mainly of graphite and CuO, which led to adhesive wear of the composites together with stable and low coefficients of friction (∼0.144) as well as a low wear rate. However, when the relative humidity exceeded 70 %, there was an increased tendency for the formation of a brittle layer predominantly consisting of Cu(OH)2 and Cu2(OH)2CO3 compounds due to tribo-chemical reactions between the composites and H2O and CO2 in humid air. Subsequently, this brittle oxide layer caused abrasive wear accompanied by fluctuations in the coefficient of friction along with increased wear rates.