Multilayer Oxide Research Articles

Flexural strength of novel glass infiltrated monochrome and multilayer high yttrium oxide containing zirconia upon various sintered cooling rates.

The sintering technique and cooling strategy influence the strength of zirconia. This study examined the impact of altering the cooling rate of glass-infiltrated monolayer and multilayer 5 mol% yttria-partially stabilized zirconia (5Y-PSZ) on their strength. One-hundred eighty (180) specimens (width×length×thickness = 10×20×2mm) were prepared using monolayer (Mo: Cercon-xt) and multilayer (Mu: Cercon-xt ML) 5Y-PSZ. Randomly distributed specimens (n = 15/group) were sintered with traditional (T) versus glass infiltrated (G) technique and cooled down with different cooling rates: slow (S: 5°C/min), normal (N: 35°C/min), and fast (F: 70°C/min). Four-point bending test was used to measure flexural strength (σ). Microstructures were investigated by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Three-way ANOVA and Tamhane comparisons were determined for a significant difference of σ (p<0.05). Weibull analysis was determined for Weibull modulus (m). The highest σ (MPa) was seen for GMuS (696.8 ± 69.8). Mo-PSZ and Mu-PSZ showed no significant difference in σ. G-sintering presented significantly higher σ (659.9 ± 79.3) than T-sintering (426.0 ± 63.7). S-cooling (560.9 ± 126.1) had the highest σ. The highest m-value was observed in GMuN (12.1 ± 3.8). A significant difference in σ was indicated due to cooling rates and sintering techniques (p<0.05). Glass infiltration significantly enhanced strength through elastic gradience. F-cooling reduced grain size, impaired grain boundary integration, and increased the tetragonal to monoclinic phase transition, significantly decreasing flexural strength in traditional sintering. Nevertheless, F-cooling was recommended for glass-infiltrated 5Y-PSZ to enhance strength while reducing processing time.

Unraveling the Correlation between the Interface Structures and Tunable Magnetic Properties of La1-xSrxCoO3-δ/La1-xSrxMnO3-δ Bilayers Using Deep Learning Models.

Perovskite oxides are gaining significant attention for use in next-generation magnetic and ferroelectric devices due to their exceptional charge transport properties and the opportunity to tune the charge, spin, lattice, and orbital degrees of freedom. Interfaces between perovskite oxides, exemplified by La1-xSrxCoO3-δ/La1-xSrxMnO3-δ (LSCO/LSMO) bilayers, exhibit unconventional magnetic exchange switching behavior, offering a pathway for innovative designs in perovskite oxide-based devices. However, the precise atomic-level stoichiometric compositions and chemophysical properties of these interfaces remain elusive, hindering the establishment of surrogate design principles. We leverage first-principles simulations, evolutionary algorithms, and neural network searches with on-the-fly uncertainty quantification to design deep learning model ensembles to investigate over 50,000 LSCO/LSMO bilayer structures as a function of oxygen deficiency (δ) and strontium concentration (x). Structural analysis of the low-energy interface structures reveals that preferential segregation of oxygen vacancies toward the interfacial La0.7Sr0.3CoO3-δ layers causes distortion of the CoOx polyhedra and the emergence of magnetically active Co2+ ions. At the same time, an increase in the Sr concentration and a decrease in oxygen vacancies in the La0.7Sr0.3MnO3-δ layers tend to retain MnO6 octahedra and promote the formation of Mn4+ ions. Electronic structure analysis reveals that the nonuniform distributions of Sr ions and oxygen vacancies on both sides of the interface can alter the local magnetization at the interface, showing a transition from ferromagnetic (FM) to local antiferromagnetic (AFM) or ferrimagnetic regions. Therefore, the exotic properties of La1-xSrxCoO3-δ/La1-xSrxMnO3-δ are strongly coupled to the presence of hard/soft magnetic layers, as well as the FM to AFM transition at the interface, and can be tuned by changing the Sr concentration and oxygen partial pressure during growth. These insights provide valuable guidance for the precise design of perovskite oxide multilayers, enabling tailoring of their functional properties to meet specific requirements for various device applications.

Comparative Retention Analysis of Intercalated Cations Inside the Interlayer Gallery of Lamellar and Nonlamellar Graphene Oxide Membranes in Reverse Osmosis Process: A Molecular Dynamics Study.

Over the past decade, multilayered graphene oxide (GO) membranes have emerged as promising candidates for desalination applications. Despite their potential, a comprehensive understanding of separation mechanisms remains elusive due to the intricate morphology and structural arrangement of interlayer galleries. Moreover, a critical concern of multilayered GO membranes is their susceptibility to swelling within aqueous environments, which hinders their practical implementation. Therefore, this study introduces cation intercalation within GO laminates to elucidate the underlying factors governing swelling behavior and subsequently mitigate it. Moreover, this study performed nonequilibrium molecular dynamics simulations on the cation (Mg2+ or K+)-intercalated lamellar and nonlamellar GO membranes to understand the effect of the arrangement of GO sheets on the retention time of intercalated cations within GO layers, water permeance, and salt rejection mechanism in the reverse osmosis process using cation-intercalated GO membranes. Our results highlight that lamellar GO membranes exhibit higher water permeance, attributed to their well-defined interlayer gallery structure. On the other hand, nonlamellar GO membranes display superior salt rejection due to their complex interlayer gallery structure that impedes salt permeation. Moreover, the structural complexity of nonlamellar GO membranes contributes to greater stability by retention of the more intercalated cations for a longer time within the layers. Furthermore, it is observed that a higher percentage of Mg2+ cations remained inside the GO laminates as compared to K+ cations, hence resulting in the greater stability of the Mg2+-intercalated GO membrane in the aqueous environment.

Synthesis of multi-layer graphene oxide from HCl-treated coke and Brazilian coals by sulfuric acid thermal exfoliation and ozone oxidation

This study involved the synthesis and characterization of graphene oxide (GO) from mineral coke and bituminous coal. HCl treated and non-HCl treated ultrafine powder obtained from both precursors were treated with H2SO4, followed by thermal treatment, and oxidation with ozone and ultra-sonication for GO production. The synthesized materials were characterized using Fourier transform infrared spectroscopy (FTIR), zeta potential (ZP), particle size distribution (PSD), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The results confirmed the exfoliation of the material primarily at the edges of its structure and the formation of multilayer graphene oxide (GO) from mineral coke and bituminous coal. Furthermore, it was found that carbonaceous materials with graphitic morphology are easier to exfoliate and oxidize, leading to the production of higher quality graphene oxide. Therefore, the GO synthesized from mineral coke exhibited the best quality in this study. The methodology used proposes an innovative approach, offering a faster, more economical, and environmentally friendly synthesis compared to the traditional Hummers' method, thereby adding value to other raw materials that can be utilized in this process, such as Brazilian coke and coal.

Alloying effects of Al, Si and Fe on Ni-20Cr alloy oxidation in water vapour at 650 °C

Ni-20Cr alloys with or without minor elements (Al, Si, Fe) were oxidized in Ar-5 H2O at 650°C. The undoped alloy formed a feathery NiO external scale and a thick internal oxidation zone (IOZ). Additions of Al, Si and Fe improved oxidation resistance by changing oxide morphologies and reducing the IOZ. For Al and Si additions, more surface area formed a chromia scale with Al2O3 or SiO2 precipitates underneath. In addition, needle-shaped precipitates with a lamellar structure of chromia mixed with alumina or silica were observed. For Fe addition, a multi-layered oxide scale was formed with additional Fe-rich spinel, improving oxidation resistance.

Studying the Structure and Properties of Epoxy Composites Modified by Original and Functionalized with Hexamethylenediamine by Electrochemically Synthesized Graphene Oxide.

In this study, we used multilayer graphene oxide (GO) obtained by anodic oxidation of graphite powder in 83% sulfuric acid. The modification of GO was carried out by its interaction with hexamethylenediamine (HMDA) according to the mechanism of nucleophilic substitution between the amino group of HMDA (HMDA) and the epoxy groups of GO, accompanied by partial reduction of multilayer GO and an increase in the deformation of the carbon layers. The structure and properties of modified HMDA-GO were characterized using research methods such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy and Raman spectroscopy. The conducted studies show the effectiveness of using HMDA-OG for modifying epoxy composites. Functionalizing treatment of GO particles helps reduce the free surface energy at the polymer-nanofiller interface and increase adhesion, which leads to the improvement in physical and mechanical characteristics of the composite material. The results demonstrate an increase in the strength and elastic modulus in bending by 48% and 102%, respectively, an increase in the impact strength by 122%, and an increase in the strength and elastic modulus in tension by 82% and 47%, respectively, as compared to the pristine epoxy composite which did not contain GO-HMDA. It has been found that the addition of GO-HMDA into the epoxy composition initiates the polymerization process due to the participation of reactive amino groups in the polymerization reaction, and also provides an increase in the thermal stability of epoxy nanocomposites.

Study of surface plasmon resonance with zirconium oxide multilayer coatings of silver and gold films: reflection polarization modes and sensitivity

We propose a surface plasmon resonance (SPR) sensor based on multilayer films with silver (Ag) and gold (Au) interfaces coated with a thin layer of zirconium oxide (ZrO2) in Kretschmann configuration. A dielectric layer of ZrO2 acts as the prism coating and the second layer is deposited after the metal film in the dielectric/metal/dielectric (DMD) system. In order to achieve the best design for the sensor, the dependence of the sensitivity on the angle of incidence and the thickness of the alternating layer is comprehensively explored. The polarization change results are shown with the angles Ψ and ∆ which are the traditional ellipsometry measurement angles of the optical properties of the DMD system. The advantage of Ag/ZrO2 multilayers over Au and Au/ZrO2 for SPR refractive index detection in terms of sensitivity, as well as the Ag/ZrO2 interface offers the possibility of studies with promising features for SPR users to generalize this type of interface. The proposed DMD sensor is expected to find application in biochemical sensing due to its resolution.

Hot corrosion behavior of Co-W coated ferritic stainless steel in molten chloride salt

The hot corrosion behavior of CoW multilayered oxide-coated FSS430 in molten NaCl-KCl (44.53–55.47 wt%) at 700 °C in an air atmosphere was investigated. The effects of CoW multi-layer oxide coating on the oxidation resistance and hot corrosion resistance of the substrate were studied by analyzing the mass change, corrosion products, surface morphology, and cross-sectional structure. The results showed that the CoW multi-layer oxide coating suppressed the interdiffusion of elements, and thus, effectively reduced the corrosion rate under the experimental conditions from 4.98 × 10−8 to 2.42 × 10−9 (g2·cm−4·s−1). Also, the coating was proved to inhibit the outward diffusion of Cr in the substrate and reduced the hot corrosion caused by the loss of Cr into the molten chloride salts.

Superconducting properties of bismuthate/manganite epitaxial multilayers

We report epitaxial growth and superconducting properties of superconductor/ferromagnet (S/F) multilayers consisting of an s-wave superconducting bismuthate BaPb0.75Bi0.25O3 (BPBO) and a ferromagnetic insulating manganite La0.875Sr0.125MnO3 (LSMO). We demonstrate that the superconductivity of BPBO sandwiched by LSMO is preserved down to a thickness close to the superconducting coherence length. The superconducting transition temperature of BPBO is unaffected by the magnetization alignment of the LSMO layers, which is in sharp contrast to YBa2Cu3O7 showing a clear magnetic exchange interaction. While the stable s-wave superconductivity in the S/F oxide multilayer demonstrated in this work is promising for the development of quantum spin devices with strong spin–orbit coupling, the absence of the magnetic exchange field effect highlights the importance of interface engineering for the realization of a strongly exchange-coupled s-wave S/F oxide interface.

On oxidation film structure of SIMP steel exposed in stagnant oxygen-saturated LBE at 600 °C

To understand the impact of multilayered oxide films on the liquid-metal resistance, SIMP steels with three different Si levels were investigated. A novel composite oxidation film, namely amorphous SiO2 packed by Cr2O3, was formed along the prior high-angle grain boundaries in internal oxidation zone to impede the inward diffusion of oxygen. Evolved into the inner layer, the amorphous SiO2 films stayed there, while Cr2O3 transformed into FeCr2O4. Moreover, outward diffusion of chromium facilitated the transformation from lower sublayer to upper sublayer in inner layer. This multilayer plays a critical role in improving the oxidation resistance of SIMP steel.

High temperature oxidation and thermal properties of laminated Ti3Al(Si)C2-TiC/Nb based composites obtained by spark plasma sintering

This paper describes high-temperature oxidation behavior and thermal properties of metal-ceramic laminated composites fabricated by spark plasma sintering of Ti3Al(Si)C2-filled preceramic papers (TAC) and Nb foils. The high-temperature oxidation tests were carried out in air at 800–1300 °C. The phase composition and microstructure of the oxide layers were analyzed by X-ray diffraction and scanning electron microscopy, respectively. The thermal properties were measured by the laser flash method in the temperature range of 30–800 °C. The evolution of the microstructure of the reaction layer (RL) formed at TAC/Nb interfaces was studied. The passive oxidation of the surface TAC layers results in the formation of outer TiO2 and inner continuous Al2O3 phase at temperatures up to 1100 °C, while local accelerated oxidation occurs above 1100 °C. As a result of breakaway oxidation, a multilayer oxide structure consisting of TiO2, Al2TiO5, Al2O3 and SiO2 phases were formed. The oxidation of inner Nb layers from the side surface can lead to high volume expansion and generation of stresses in the ceramic and metal layers due to the formation of Nb2O5 oxide phase. The stress relaxation occurred by complex mechanisms, including plastic deformation of the Nb layers, delamination at the interfaces, and formation of cracks in the reaction and TAC layers. The high temperature exposure results in slight increase in columnar grains in the reaction layers at 1200 °C, while the thickness of RL remains unchanged. The TAC/Nb composites exhibit higher thermal conductivity and diffusivity compared to monolithic TAC ceramic composites.

EFFICIENT SYNTHESIS OF ZNO AS AN ELECTRODE OF PIEZOELECTRIC NANOGENERATORS

Piezoelectric nanogenerators (NGs) hold immense promise as self-powered devices for harvesting mechanical energy from the environment. This study introduces an efficient and scalable synthesis method for zinc oxide (ZnO) nanorods, a pivotal material in piezoelectric nanogenerators (NGs), with several key results. A Chemical Bath Deposition technique is employed, optimizing parameters such as growth time, temperature, and precursor concentrations to achieve well-aligned and high-quality ZnO nanorods. The structural and morphological characteristics of the synthesized nanorods are systematically investigated using advanced characterization techniques. The synthesized ZnO nanorods exhibit an average length of 400nm, demonstrating their slender shape. Furthermore, the study determines an energy gap value of 3.5 eV for multilayer zinc oxide thin films, indicating the transition from the valence band to the conduction band. Notably, thermal annealing at 500°C leads to a substantial increase in average output voltage, reaching 1.95 V, a fourfold improvement compared to as-deposited nanopowders. These findings emphasize the efficiency and potential of the proposed synthesis method and underscore its practical applications in enhancing energy harvesting capabilities for sustainable power generation from mechanical sources in piezoelectric NGs.

Synthesis and Promising Applications of Graphene and Related Materials

In recent years, there has been extensive research on graphene and its derivatives, driven by their remarkable physicochemical and functional properties. Various forms of graphene, such as multi-layer graphene, graphene oxide, and graphene quantum dots, have shown immense potential to revolutionize multiple technologies. This review critically examines the synthesis and applications of graphene and related materials. In the synthesis section, we explore methods ranging from top-down techniques, which involve breaking down larger structures into graphene layers, to bottom-up approaches, where graphene is built up from smaller constituents. In the application segment, we comprehensively discuss the diverse uses of graphene and its derivatives. This includes their roles in electronic applications, energy storage systems, tribological applications, healthcare technologies, water desalination processes, and mechanical applications. By exploring various applications, we aim to highlight the wide-spread applications of graphene-based materials and their composites in shaping the future of multiple technologies.

Thermal effusion of water and carbon oxides from multilayered graphene oxide thin films

Thermal effusion of water and carbon oxides from multilayered graphene oxide thin films

“Ion-cage” structure of graphene oxide membranes with stable interlayer spacings towards efficient desalination

Multilayered graphene oxide (GO) membrane with sub-nanometer channels is an ideal candidate for desalination. However, excluding small ions using GO-based membranes in the pressured filtration processes remains a great challenge due to the tortuous transport paths of laminates and their water-swelling characteristic. In our previous work, we developed the cation-controlled theory to precisely regulate the interlayer spacing of GO membranes in aqueous solutions. In this work, we proposed an “ion-cage” strategy to enhance the stability (anti-swelling) of the K-controlled GO (icGO-K) membrane for achieving efficient desalination. The icGO-K membrane, coated with positively charged polyethyleneimine (PEI) on its upper and lower surfaces, immobilized intercalated cation K+ between the laminates by electrostatic repulsion to maintain the stability of the confined interlayer spacing. The icGO-K membrane demonstrated superior rejection of 95.3 %, 83.2 %, 81.8 %, and 70.7 % for MgCl2, MgSO4, NaCl, and Na2SO4 while maintaining competitive permeance of ∼ 3.5 L m-2h−1 bar−1 in the desalination process. More importantly, the icGO-K membrane exhibited ultra-long desalination stability up to 720 h. The enhanced performance can be attributed to the synergistic effect of the confined interlayer spacing and surface electrostatic repulsion. Overall, this work provides attractive strategy to fabricate fine-tuning 2D laminate nanochannels for high efficiency of desalination application.

Crafting Insulating Polymer Mediated and Atomically Precise Metal Nanoclusters Photosensitized Photosystems Towards Solar Water Oxidization.

Atomically precise metal nanoclusters (NCs) have been deemed as a new generation of metal nanomaterials because of their characteristic atomic stacking fashion, quantum confinement effect, and multitude of active sites. The discrete molecular-like energy band structure of metal NCs endows them with photosensitization capability for light harvesting and conversion. However, applications of metal NCs in photoelectrocatalysis are limited by the ultrafast charge recombination and unfavorable stability, impeding the construction of metal NC-based photosystems. In this work, we elaborately crafted multilayered metal oxide (MO)/(metal NCs/insulating polymer)n photoanodes by a facile layer-by-layer (LbL) assembly technique. In these well-defined heterostructured photoanodes, glutathione (GSH)-wrapped metal NCs (Agx@GSH, Ag9@GSH6, Ag16@GSH9, and Ag31@GSH19) and an insulating poly(allylamine hydrochloride) (PAH) layer are alternately deposited on the MO substrate in a highly ordered integration mode. We found that photoelectrons of metal NCs can be tunneled into the MO substrate via the intermediate ultrathin insulating polymer layer by stimulating the tandem charge transfer route, thus facilitating charge separation and boosting photoelectrochemical water oxidation performances. Our work would open a new frontier for judiciously regulating directional charge transport over atomically precise metal NCs for solar-to-hydrogen conversion.

Extraction of Vitamin B12 from Aqueous Solution by using Solid- Liquid Extraction and Ultra Sonic Frequency

A new method to uptake vitamin B12 in aqueous solution as pharmaceutical preparations by adsorption on the solid phase surface by using a multi-layer graphene oxide derivative compounds while the ultrasonic frequency wave was used to increase the efficiency of the extraction of drug from aqueous solution. Interlayer drug extraction conditions were optimized by studying a number of conditions that affect the extraction rate, including pH, ultrasound frequency, residence time of the solution inside the ultrasound device, the effect of the amount of graphene oxide derivative, and vitamin B12 concentration. The effect of temperature was also studied and a number of thermodynamic factors were generated. From the results, it was found that the best weight for the economically useful graphene oxide derivative is 0.01 grams at a concentration of 20 ppm relative to the concentration of the vitamin using an acidic medium of 2.1. The best temperature is 40 0C and within 50 Hz of the frequencies of the ultrasound device during the incubation period of 50 minutes. The proposed method was also applied to pharmaceutical samples containing vitamin B12, and the extraction rate was 95.35 %, with a very small error rate of 0.0465.

Effect of Secondary Oxidants (CO2 and/or H2O) on Oxidation of Fe-20Cr-(Mn, Si)

Ferritic heat resisting alloys are widely used in industry owing to their combination of economy, reasonable strength, and high temperature corrosion resistance. Alloy design centres on forming and maintaining an external, slow growing protective oxide scale by selective oxidation of the desired metal, commonly chromium. Design methods based on diffusion theory succeed when the service environment is oxygen or clean, dry air. However, they can fail badly when secondary oxidants (like CO2 and water vapour) are present, which is commonly the case in energy production etc. This work investigates the effect of CO2 and H2O on corrosion behaviour of Fe-20Cr, in comparison with that in pure O2. The alloying effect of Si and Mn on oxidation behaviour of Fe-20Cr in different gases is also investigated.Model alloys Fe-20Cr, Fe-20Cr-1Si, Fe-20Cr-2Mn (all in wt%) were arc melted and annealed. Sample coupons were cut, ground, mechanically polished to 3mm finish, and further electro-polished to remove subsurface deformation zones. They were then exposed to Ar-2O2, Ar-20H2O-2O2, Ar-20CO2-2O2, Ar-CO2-H2O and Ar-CO2-H2O-O2 (all vol%) gas mixtures, at 650°C for 150h. Corrosion products and cross-sections were examined using optical microscopy, X-ray diffraction, Raman Spectroscopy and scanning electron microscopy equipped with energy dispersive X-ray spectrometry.The alloy behaved protectively in Ar-2O2, forming a very thin Cr2O3 layer on its surface. However, when CO2 or/and H2O was added to oxygen, breakaway oxidation resulted, forming thick multi-layered oxide scales. Detailed analysis revealed that this multi-layered structure contains four layers, where the outer layer was Fe2O3, overlying an Fe3O4 layer and FeCr2O4 spinel innermost layer, and an internal oxidation zone was formed beneath the scale. In the low environment of Ar-20CO2-20H2O, Fe3O4 layer, FeCr2O4 spinel layer and internal oxidation zone formed a three-layered structure. No Fe2O3 was found, which is attributed to the decrease in oxygen partial pressure.Carburisation of Fe-20Cr also resulted from exposure to the three CO2-bearing gases. The deepest and densest internal carburisation zone formed in Ar-20CO2-2O2. In Ar-20CO2-20H2O-2O2 and Ar-20CO2-20H2O, internally precipitated carbides were sparser, but still obvious.Silicon addition dramatically improved the oxidation resistance of Fe-20Cr. Weight gains in all gases were sharply decreased compared with those of Fe-20Cr. As with Fe-20Cr, a very thin Cr2O3 layer on the Si-bearing alloy reacted in Ar-2O2,together with a thin underlying silica layer, indicating that the alloy was fully protected. Unlike Fe-20Cr, the Fe-20Cr-1Si alloy was also protected in Ar-20CO2-2O2. However, when water vapour was present, the alloy started to go into breakaway, forming local Fe-rich oxide nodules. In Ar-20H2O-2O2, some small nodules, consisting of external Fe2O3 and inner spinel were distributed on an otherwise thin, protective chromia scale. In Ar-20H2O-20CO2-2O2 and Ar-20H2O-20CO2, an additional Fe3O4 layer was observed in nodules, between Fe2O3 and inner spinel. Thus, for Fe-20Cr-1Si samples, Fe3O4 can only be observed if 20%CO2 and 20%H2O were both present. Additionally, some small internal oxide particles were observed at breakaway nodule areas in all these three gasses. Internal carbides were found only under the big iron oxides nodules grown in Ar-20CO2-20H2O-2O2.Manganese addition did not much influence the corrosion resistance of Fe-20Cr. In general, oxide morphologies were similar to those of Fe-20Cr. In Ar-2%O2 gas, a thin Mn rich chromium oxide layer was formed over the entire alloy surface, indicating that sample was fully protected. Multi-layered thick oxides developed when CO2 or/and H2O were added. For high gases with the addition of H2O or CO2 (Ar-20H2O-2O2, Ar-20CO2-2O2, and Ar-CO2-H2O-O2), three-layered oxide structures were found to be made up of Fe2O3, Fe3O4, and spinel layers, in sequence from the outer surface to the inner alloy. It is worth noting that the oxide layers were not completely continuous in Ar-20CO2-2O2. About 15% of the cross-section area was protected which indicated that Mn can slightly improve the corrosion resistance in dry CO2 and O2 environments. In lower oxygen partial pressure gas (Ar-CO2-H2O), no Fe2O3 was found, and only Fe3O4 and spinel constituted the oxide scale. The main difference was that the internal oxidation zone became tiny on Fe-20Cr-2Mn samples. Internal carbides were still found under inner oxide in all CO2 bearing gases, most obviously in Ar-20CO2-2O2. However, in all cases the carbide quantities were far less than those in Fe-20Cr, indicating that Mn addition partially inhibited carburisation.After the thermodynamics of the reaction product phase assemblages are considered, this complex pattern of reaction products is discussed in terms of the permeability of different oxides to carbon- and hydrogen-bearing species, along with interactions between secondary oxidants on oxide surfaces and grain boundaries.

Understanding the role of oxide layers on color generation and surface characteristics in nanosecond laser color marking of stainless steel

This study conducts an experimental analysis of Laser Color Marking (LCM) on Stainless Steel, aiming to elucidate the role of oxides in color formation. Employing a nanosecond pulsed fiber laser, we systematically varied process parameters to successfully generate a diverse array of distinctive colors. Remarkably, a myriad of colors became evident at the micro-scale, offering a striking contrast to the macroscopic view dominated by a singular prominent color. These colors exhibited a notable increase in oxygen composition, reaching levels as high as 24.5%, coupled with the formation of a thin oxide film spanning thicknesses from 220 to 850 nm. The prevalence of chromium oxides resulted in greenish or bluish shades, whereas iron oxides’ dominance produced brownish and reddish hues. Particularly intriguing was the revelation of a multi-layer oxide film in samples like brown. Furthermore, the nature of oxides was also found to have an influence on surface characteristics. Chromium oxide-dominated colors exhibited ablation depth, while iron oxide-dominated colors resulted in surface overgrowth due to their porous nature. Correspondingly, Vickers hardness of samples dominated by chromium oxides showcased a significant enhancement in microhardness compared to those with iron oxide dominance. Lastly, we observed minimal degradation in surface roughness characteristics after LCM, with variations ranging from 262 nm to 463 nm, compared to 150 nm for untreated samples. These comprehensive findings provide valuable insights for optimizing the LCM process for stainless-steel color markings.

Microstructure and electrical property of composite Co-W/CuO multilayered oxide coating for solid oxide fuel cell interconnector

To overcome the challenges related to the electrical resistance owing to the growth of the Cr-containing oxide layer in the SOFC system at high temperature, a composite coating of Co-W/CuO was fabricated on ferritic stainless steel for interconnectors by composite electroplating and pre-oxidation treatment. Compared to the Co-W alloy coating, the addition of CuO led to the formation of Cu-Co spinels and Cu-W composites, which affected the surface microstructure of the coating. Scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) and transmission electron microscopy (TEM) investigations shows that CuWO4 nano-particles formed in the Cr-rich layer beneath the CoWO4 layer, of which the lattice deviation leads to the formation of oxygen vacancies. The CuWO4 acted as conductive pathways, reducing the electrical resistance. Long-term oxidation exposure further demonstrated that the Co-W/CuO coated SUS 430 exhibited a stable electrical conductivity of 10.23 mΩ cm2.