Oxide Layer Research Articles

EIS Study of Oxide Layer in Porous Tantalum

EIS Study of Oxide Layer in Porous Tantalum

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.

Electrical resistance based residual strength prediction method for SiC/SiC mini-composites after stress-free oxidation

A stress-free oxidation model considering the microstructural characteristics of SiC/SiC mini-composites was proposed based on the electrical resistance change before and after oxidation. The relationship between the electrical resistance and the thickness of the internal fiber oxide layer was established. The stress-free oxidation tests were carried out at different temperatures for different oxidation times. The results of the oxide layer thickness calculated by the model agree well with those of the SEM observation. Based on the microstructure of tensile fracture after oxidation, the residual strength model of SiC/SiC mini-composites was proposed. The residual strength of the specimens after stress-free oxidation was calculated based on the oxide layer thickness obtained from the model. The error between the calculated and experimental results is within 14.48 %.

Effect of the Atmosphere on the Properties of Aluminum Anodizing

This study aims to quantify the effect of process parameters on the anodizing of Al6061 aluminum. To achieve this, studies on layer thickness, the porosity of the anodized surface, electrochemical techniques, X-ray diffraction, grain size estimation, and statistical analysis were conducted for three different atmospheres (without air, air, and oxygen). Parameter levels were established as follows: temperature (30 °C, 45 °C, and 60 °C), time (20 min, 40 min, and 60 min), electrolyte concentration (0.5 M), voltage (9 V), and current intensity (0.600 A). A 33 experimental design (three factors, three levels) was proposed, and mathematical models were obtained using general factorial design. The experimental design was used to determine the three most important variables in the optimal condition. A total of 27 tests were conducted using sulfuric acid electrolytic solutions, of which 12 samples were selected by the factorial design method, which simultaneously evaluates the effects of factors and their interactions in a single experiment. Measurement of porosity and oxide layer thickness was performed using scanning electron microscopy. The purity of the anodic layer formed was characterized using X-ray diffraction techniques with a vertical goniometer X-ray diffractometer. The electrochemical behavior is presented through potentiodynamic polarization curves for the anodic layer. A general factorial design and an analysis of variance (ANOVA) were conducted to establish the significant factors for layer thickness, grain size, and reaction rate. Finally, the best results and their parameters for each response are presented.

Effect of CrN coating on the hot salt corrosion fatigue behavior of titanium alloy

The dwell fatigue behavior of CrN coated titanium alloys were carried out in air and hot salt corrosive environment at 500 ℃. The results indicate that the decrease of the elastic modulus difference between the coating and the substrate alleviates the deformation mismatch issue at high temperature. Stress relaxation at the crack tip caused by Cr transition layer oxidation can improve the fatigue properties of the coated samples. Furthermore, the CrN coating enhances the corrosion fatigue properties, which is related to the barrier effect of the coating on the corrosive medium. The crack growth mode in the substrate transition from stress corrosion crack to fatigue damage crack.

Characterization of field emission from oxidized copper emitters

In this work, the field electron emission from oxidized copper emitters was studied by aging with radii in the range of 80–300 nm. The samples were prepared by an electrochemical etching method using an H3PO4 solution. The samples were exposed to air for 30 d to form an oxide film owing to aging. Measurements were carried out under high vacuum conditions in the range of 10−6 mbar. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM- EDS) was used to calculate the emitter radius, study the purity of the samples, and detect the oxide layers. Current–voltage (I-V) characteristics were studied and analyzed using Murphy-Goode (MG) plots and rectification tests. Furthermore, the spatial distribution of the electron emission and current stability were recorded and used to analyze the electron emission behavior of the tip surface. The trap density was also studied when the oxide layer was 3 layers thick. The results show that the emitters passed the orthodoxy test at low voltages. It was found that traps play an important role in increasing the switch-on current as the area of the oxide layer increases. It was found that the emitter acts as a point capacitor based on the charging and discharging processes of the electrons in the traps. The emission pattern showed great stability, which opens up prospects for this type of emitter in industry.

Effects of Thermal Exposure Temperature on Room-Temperature Tensile Properties of Ti65 Alloy.

As a critical material for high-temperature components of aero-engines, the mechanical properties of Ti65 alloy, subjected to high-temperature and long-term thermal exposure, directly affect its service safety. The room-temperature tensile properties of the Ti65 alloy after thermal exposure to temperatures ranging from 450 °C to 650 °C for 100 h were investigated. The results indicate that as the thermal exposure temperature increases, the strength of Ti65 alloy initially increases and then decreases, while ductility exhibits a decreasing trend. The strength of the thermally exposed alloy positively correlates with the size and content of the α2 phase. The ductility of the thermally exposed alloy is comprehensively influenced by the surface oxidation behavior, α2 phase, and silicides. After the prolonged thermal exposure, stress concentration at the crack tips within the oxide layer was enhanced with the increased thickness of the surface TiO2 oxide layer, leading to premature fracture due to reduced alloy ductility. Furthermore, the α2 phase in the matrix promotes the planar slip of dislocations, while silicides at the α/β phase boundaries hinder dislocation motion, causing dislocation pile-ups. Both behaviors facilitate crack nucleation and deteriorate alloy ductility.

Bonding Behavior and Quality of Pressureless Ag Sintering on (111)-Oriented Nanotwinned Cu Substrate in Ambient Air.

(111)-oriented nanotwinned Cu ((111)nt-Cu) has shown its high surface diffusion rate and better oxidation resistance over common polycrystalline Cu (C-Cu). The application of (111)nt-Cu as an interface metallization layer in Ag-sintered technology under the role of oxygen was investigated in this work, and its connecting behavior was further clarified by comparing it with C-Cu. As the sintering temperature decreasing from 300 to 200 °C, the shear strength on the (111)nt-Cu substrate was still greater than 55 MPa after sintering for 10 min. The fracture surface correspondingly changed from the interface of Ag/die to mixed fracture mode, involving the interface of the Ag/Cu substrate and Ag/die. The existence of copper oxide provided a tight connection between Ag and the (111)nt-Cu substrate at all of the studied temperatures. Although lots of small dispersed voids were seen at the interface between copper oxide and (111)nt-Cu at 300 °C, these impurity-induced voids would not necessarily be a failure position and could be improved by adjusting the sintering temperature and time; for example, 200 °C/10 min or heating to 300 °C, and then start cooling at the same time. The microstructure of Ag-Cu joint on (111)nt-Cu behaved better than that on C-Cu. The thinner copper oxide layer and the higher connection ratio of the interface between copper oxide and Ag were still found on the (111)nt-Cu connection's structure. The poor connection between copper oxide and Ag on C-Cu easily became the failure interface. By controlling the thickness of copper oxide and the content of impurity-induced voids, the use of (111)nt-Cu in advanced-packaging could be improved to a new level.

Enhanced Electro‐Resistance and Tunable Asymmetric Depolarization Behavior in Hf0.5Zr0.5O2 Ferroelectric Tunnel Junction by Bottom Oxide Interfacial Layer

AbstractElectro‐resistance (ER) plays a crucial role in the application of hafnia‐based ferroelectric tunnel junctions (FTJs), pivotal devices widely acknowledge for their potential in non‐volatile memory and neuromorphic networks. Leveraging atomic layer deposition (ALD) enhances the flexibility in fabricating bilayer FTJs by combining a ferroelectric layer with another oxide layer. Introducing additional layers is necessary to achieve a sufficient storage window for implementing intriguing functions, albeit at the risk of increased depolarization field strength. Hence, selecting a suitable inserted layer becomes paramount. In this study, a novel strategy to enhance the performance of Ge‐based Hf0.5Zr0.5O2 FTJs is presented by incorporating bottom interfacial layers (ILs) with distinct band energy characteristics. The optimized FTJs exhibit significantly improved endurance, lower coercive voltage, and enhanced retention properties. Notably, an intriguing asymmetric retention behavior driven by the imprint field (Eimp) is observed, which can be mitigated by integrating TiO2 ILs. Most importantly, an effective method to manipulate depolarization behavior in hafnia‐based devices through ILs is introduced, leading to enhanced non‐volatility and synaptic behavior in FTJs.

Enhanced cyclic oxidation resistance of Metcoloy II coated ASTM A53 Grade B steel by electric arc thermal spray

This study evaluates the enhanced cyclic oxidation resistance of Metcoloy II coatings applied to ASTM A53 Grade B steel substrates using electric arc thermal spray, across temperatures ranging from 500 °C to 700 °C. The research identifies distinct performance differences between coated and uncoated samples under cyclic oxidation conditions. Initially, both sample types exhibited mass increases due to oxide formation. However, uncoated samples developed non-protective iron oxides, while Metcoloy II coatings formed a protective layer of chromium and nickel oxides. During 500 oxidation cycles at 500 °C, uncoated samples showed a rapid mass increase, indicative of accelerated oxidation, whereas Metcoloy II coatings experienced a controlled mass gain, reflecting effective protection by chromium and aluminum oxides. At 700 °C, the mass variation trends were similar for both types initially; however, uncoated samples suffered significant mass loss due to iron oxide volatilization, emphasizing their susceptibility. Conversely, Metcoloy II coatings exhibited a reduced but steady mass increase, indicating their resilience under high-temperature conditions. Microstructural analysis confirmed the presence of a protective oxide layer in the coated samples, which is essential for reducing substrate oxidation. Although challenges such as coating detachment and thinning were observed, particularly at higher temperatures, Metcoloy II coatings maintained their protective role. This study highlights the coating's effectiveness in extending the lifespan of steel substrates subjected to cyclic oxidation, providing valuable insights for optimizing protective coatings in demanding industrial applications and advancing material science strategies for enhanced durability.

Cracking in semiconductor devices–effect of plasticity under triaxial constraint

A semiconductor device integrates dissimilar materials of small sizes and complex geometries. During fabrication, the materials are deposited at various temperatures. Both deposition and change in temperature cause stresses in the materials. Under the stresses, ductile materials may deform plastically, and brittle materials may crack. Here we focus on how plastic deformation in the ductile materials affects cracking in nearby brittle materials. We study a model structure in which a metal line is encased by a silicon substrate and a brittle oxide layer. In the triaxially constrained metal, the stresses readily exceed the yield strength of the metal. Such high stresses in the metal elevate the stresses in the oxide. The degree of triaxial constraint varies with the aspect ratio of the metal. We compute the stress in the oxide, as well as the energy release rate of an edge crack and a long channel crack. We discuss strategies to avert cracking in the oxide.

Investigation on the microstructure and high-temperature properties of AlN coating through oxygen addition

This study meticulously examines how oxygen incorporation alters the microstructure, mechanical, and high-temperature properties of AlN coating prepared via cathodic arc deposition. Substitution of nitrogen by oxygen in the AlN lattice leads to the formation of Al(OxN1-x)y metastable solid solutions from wurtzite Al(O)N structure to cubic AlO(N) structure, culminating in a full conversion to γ-Al2O3 with increased oxygen content. This substitutive solid solution induces solid solution strengthening and grain refinement effect, thereby escalating hardness from ∼18.5 GPa for AlN to ∼23.9 GPa for Al(O0.18N0.82)1.09. Despite an observed tendency towards enhanced thermal decomposition of oxynitride coatings upon annealing, the occurrence of α-Al2O3 oxide phase significantly preserves the mechanical integrity at elevated temperatures, outperforming pure AlN coating. Notably, the strategic alteration by minimal oxygen incorporation facilitates the formation of an Al-rich oxide layer, which exhibits superior anti-oxidative characteristics. After oxidation at 1100 °C for 10 h, the Al(O0.10N0.90)1.03 with an oxide layer of ∼1.2 μm exhibits remarkable oxidation resistance.

Thermal Corrosion Properties of Composite Ceramic Coating Prepared by Multi-Arc Ion Plating

In this study, a NiCr/YSZ coating was applied to a γ-TiAl surface using multi-arc ion plating technology to enhance its high-temperature performance and explore the mechanisms of high-temperature oxidation and thermal corrosion. The thermal corrosion properties of the γ-TiAl matrix and NiCr/YSZ coating were investigated at 850 °C and 950 °C using a constant-temperature corrosion test in a 75% Na2SO4 + 25% NaCl mixture. The results indicate that after 100 h, the thermal corrosion weight gain of the coating samples was 70.1 mg/cm2 at 850 °C and 118.2 mg/cm2 at 950 °C. At these temperatures, sulfide formation on the surface increases, leading to a loose and porous surface. After 100 h of high-temperature corrosion at 850 °C, the primary oxidation product on the surface of the coating was tetragonal-ZrO2. At 950 °C, Y2O3, which mainly acts as a stabilizer in YSZ, reacted with Na2SO4, resulting in the continuous consumption of Y2O3. This reaction caused a substantial amount of tetragonal-ZrO2 to transform into monoclinic-ZrO2, altering the volume of the ceramic layer, which induced internal stress, crack propagation, and minor spallation. A continuous and dense internal thermally grown oxide (TGO) layer effectively impeded the diffusion of molten salt substances and oxygen, thereby significantly improving the thermal corrosion resistance of the thermal barrier coating.

Janus-structured graphene scaffold for bottom-up lithium deposition: A progressive gradient approach

Graphene-based materials have been explored as hosts for Li metal anodes, but their high interfacial activity and short diffusion distances frequently result in dendrite formation on the surface. Herein, we utilize the adjustable conductivity and Li affinity of graphene oxide (GO) to develop a Janus structure comprising a top GO layer and a bottom reduced graphene oxide (rGO) layer. The progressive conductivity and lithiophilicity gradient structure of GO/rGO enables a bottom-up Li deposition mode, rendering an average Coulombic efficiency of 99.1 % over 350 cycles at 1 mA cm−2 and 1 mAh cm−2. Full cells equipped with a LiFePO4 cathode maintain a capacity retention of 85 % after 350 cycles at 1 C. This innovative approach provides fresh insights into the development of graphene-based hosts, offering significant potential for future Li metal battery applications.

Fatty Imidazolines as a Green Corrosion Inhibitor of Bronze Exposed to Acid Rain

Acid rain is one of the primary corrosive agents on bronze exposed to the atmosphere. Bronze naturally forms a layer of oxides on its surface called patina, protecting it from corrosion. However, when exposed to acid rain, this layer dissolves, making it necessary to use a corrosion inhibitor or stabilize the patina. This study investigated fatty imidazolines derived from agro-industrial waste bran as a corrosion inhibitor of SAE-62 bronze in simulated acid rain (pH of 4.16 ± 0.1). Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curve (PC) measurements were used to evaluate corrosion inhibition efficiency, which was 90% for an inhibitor concentration of 50 ppm. The EIS measurements showed that the fatty imidazolines formed a protective film that stabilized the patina on the bronze surface to a certain extent by hindering the charge transfer process. SEM–EDS analyzed the morphology and composition of the protective oxide layer. The results were complemented by Raman spectroscopy and XRD analysis, indicating cuprite, tenorite, cassiterite, and covellite in the patina layer formed on the bronze surface. The SEM analysis showed that the protective coating on the bronze surface was homogeneous using a 50-ppm inhibitor concentration. The XRD analysis suggested the presence of an organic complex that stabilizes the corrosion products formed on the bronze surface.

Fabrication of nickel oxide decorated CNTs/GO nanohybrid: A multifunctional electrocatalyst for overall electrochemical water splitting

Hydrogen production from water as renewable energy resource is vital to fulfil the huge energy demands without any hazardous environmental impact. Pursuing the efficient, durable and economical electrocatalyst other than benchmark expensive materials such as Pt, Ru, and Ir, for water electrolysis is a big challenge to produce the hydrogen as clean fuels. Here, we have successfully decorated nickel oxides nanoparticles over the carbon nanotubes covered by the graphene oxide layers (GO/NiO@CNTs/GO) using a facile hydrothermal method and utilized as electrocatalyst for electrochemical water splitting. The surface morphology and structure was assessed using a variety of analytical techniques, including scanning electron microscopy (SEM), energy dispersive X-rays spectroscopy (EDX) and X-ray diffraction (XRD). As prepared nanohybrid (GO/NiO@CNTs/GO) was utilized as multifunctional electrocatalyst to investigate the water electrolysis potential via different electrochemical techniques including linear sweep voltammetry (LSV), and cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry. The fabricated electrode exhibited a lower overpotential of 236 mV and 208 mV at the standard current density of 10 mAcm−2 under alkaline and acidic conditions, respectively. Enhanced double layer capacitance (Cdl) and reduced charge transfer resistance (Rct) also showed the boosted performance for the hybrid materials with long term stability. The carbon based nanohybrid (GO/NiO@CNTs/GO) showed the promising potential having multifunctional characteristics including oxygen and hydrogen evolution reactions along with overall electrochemical water splitting.

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.

Assessment of the microstructure, adhesion and elevated temperature erosion resistance of plasma-sprayed NiCrAlY/cr3C2/h-bn composite coating

This study uses an air jet erosion tester to investigate the erosion behavior of NiCrAlY/Cr3C2/h-BN composite coatings that are plasma-sprayed at three different temperatures and 40 m/s on T22 boiler steel alloy. 30 and 90° are the impingement angles. To identify the erosion mechanism, SEM and X-ray diffraction techniques are used to analyze the surface morphology and phase generated on the eroded surface. Findings of erosion test indicate that the erosion resistance was notably enhanced by addition of Cr3C2 and h-BN because of its lubricating characteristics and capacity to reduce frictional forces during erosion. The combined influence of Cr3C2 and h-BN enhanced the coating hardness and erosion wear resistance, thereby improving its overall resistance to erosion. The weight loss method was employed to calculate the erosion rate, and the NiCrAlY/Cr3C2/h-BN coating showed up to 30.55% and 34.48% lower erosion rate as compared to uncoated T22 substrate at 600 °C for 30° and 90° impact angles, respectively. This characteristic is affected by the hard reinforcement Cr3C2's high-temperature stability, the h-BN's self-lubricating ability, the formation of a protective oxide layer that forms at 600 °C, and the eroded coating's ductile behavior of material removal. The study also reveals that the NiCrAlY/Cr3C2/h-BN coating system on T22 boiler steel alloy has excellent erosion resistance, making it suitable for use in high-temperature and erosive environments in boiler systems and similar industries.

Mixed phase iron oxides thin layers by atmospheric-pressure chemical vapor deposition method

This paper provides a simple method for producing a metal oxide thin layer methodology by atmospheric pressure chemical vapor deposition (APCVD) synthesis over stainless steel substrates. This methodology enables the formation of thin iron oxide layers at its performance at various temperatures of 330 °C, 430 °C, and 530 °C. The deposition arises from thermal decomposition of the iron organometallic precursor Fe3(CO)12, forming a thin layer of iron oxide is, by the ozone present in the reaction chamber promoting the deposition of the iron oxide particles over the substrate. The Raman characterization suggest that at 330 °C, a mixture of hematite and magnetite is predominant on the as deposited substrates, also hematite modes show to be more pronounced as the band at 300 cm-1 narrows. Conversely, magnetite is prominent at higher synthesis temperatures, exhibiting a more intense Eg5 mode at 680 cm-1. The particles exhibit a uniform morphology, with both metal oxide phases coexisting. The average diameter of the particles is 50 nanometers as scanning electronic microscopy shows in a transversal sample section.•The formation of particles is attributed to the combination of iron ions +2 and +3 in the deposition process and their interaction with oxygen in the given synthesis parameters at atmospheric pressure chemical vapor deposition (APCVD).

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.