Oxidation Of Alloys Research Articles

Enhancement of biocompatibility of anodic nanotube structures on biomedical Ti–6Al–4V alloy via ultrathin TiO2 coatings

This work aims to describe the effect of the surface modification of TiO2 nanotube (TNT) layers on Ti-6Al-4V (TiAlV) alloy by ultrathin TiO2 coatings prepared via Atomic Layer Deposition (ALD) on the growth of MG-63 osteoblastic cells. The TNT layers with two distinctly different inner diameters, namely ∼15 nm and ∼50 nm, were prepared via anodic oxidation of the TiAlV alloy. Flat, i.e., non-anodized, TiAlV alloy foils were used as reference substrates. Additionally, a part of the TNT layers and alloy foils was coated with ultrathin coatings of TiO2 by ALD. The number of TiO2 ALD cycles used was 1 and 5 leading to a nominal TiO2 thickness of ∼0.055 and ∼0.3 nm, respectively. The ultrathin TiO2 coating by ALD enabled to optimize the surface hydrophilicity for optimal cell growth. In addition, coatings shaded impurities of V- and F-based species (stemming from the alloy and the anodization electrolyte) that affect the biocompatibility of the tested materials while preserving the original structure and morphology. The evaluation of the biocompatibility before and after TiO2 ALD coating on TiAlV flat surfaces and TNT layers was carried out using MG-63 osteoblastic cells and compared after incubation for up to 96 h. The cell growth, adhesion, and proliferation of the MG-63 on TiAlV foils and TNT layers showed significant enhancement after the surface modification by TiO2 ALD.

Study on the High-Temperature Oxidation of AlCrFeCoNi-Based High-Entropy Alloys with Trace Si Additions

This research investigates the isothermal oxidation behavior of AlCrFeCoNiSix (x = 0, 0.04, 0.08, 0.12at.%) at 900°C for 96hours from multiple aspects, including the oxidation surface, the oxide layer microstructure, and the oxidation mechanisms. The oxidation kinetics curves of the alloys follow the parabolic oxidation law. After 96hours of oxidation at 900°C, the oxide films of the AlCrFeCoNi and AlCrFeCoNiSi0.04 alloys are primarily composed of Al2O3. In contrast, the oxide films of the Si8 and AlCrFeCoNiSi0.12 alloys consist of an outer layer of Cr2O3/spinel oxides and an inner layer of Al2O3.The results show that the third element effect triggered by the addition of Si can promote the generation of an Al2O3 layer, which has a positive effect on the antioxidant of high-entropy alloys.

High-Entropy Prussian Blue Analogue Derived Heterostructure Nanoparticles as Bifunctional Oxygen Conversion Electrocatalysts for the Rechargeable Zinc-Air Battery.

In response to energy challenges, rechargeable zinc-air batteries (RZABs) serve as an ideal platform for energy storage with a high energy density and safety. Nevertheless, addressing the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in RZAB requires highly active and robust electrocatalysts. High-entropy Prussian blue analogues (HEPBAs), formed by mixing diverse metals within a single lattice, exhibit enhanced stability due to their increased mixing entropy, which lowers the Gibbs free energy. HEPBAs innately enable sacrificial templating, an effective way to synthesize complex structures. Impressively, in this study, we successfully transform HEPBAs into exquisite multiphase (multimetallic alloy, metal carbide, and metal oxide) heterostructure nanoparticles through a controlled synthesis process. The elusive multiphase heterostructure nanoparticles manifested two active sites for selective ORR and OER. By integrating CNT into HEPBA-derived nanoparticles (HEPBA/CNT-800), the HEPBA/CNT-800 demonstrates superior activity toward both ORR (E1/2 = 0.77 V) in a 0.1 M KOH solution and the OER (η = 330 mV at 50 mA cm-2) in a 1 M KOH solution. The RZAB with a HEPBA/CNT-based air electrode demonstrated an open-circuit voltage of 1.39 V and provided a significant energy density of 71 mW cm-2. Moreover, the charge and discharge cycles lasting up to 40 h at a current density of 5 mA cm-2 demonstrate its excellent stability. This work provides an alternative avenue for the rational design of HEPBA's derivative for a sustainable rechargeable metal-air battery platform.

Detailing the redox ability of supported Pt-Sn and Pt-In catalysts for CO2-assisted PDH

Alloying Pt with In or Sn crucially improves Pt-based propane dehydrogenation (PDH) catalysts. CO2-assisted PDH (CO2-PDH) offers further benefits through H2 and carbon oxidation, but adds a complex interplay between alloy oxidation, nanoparticle (NP) sintering and carbon formation. Developing Pt-based CO2-PDH catalysts requires deconvoluting the hereto unidentified alloy properties and reaction mechanisms. This is studied through in situ Quick X-ray Absorption Spectroscopy and Temporal Analysis of Products on Pt:Sn/MgAl2O4 (Pt:Sn) and Pt:In/MgAl2O4 (Pt:In) catalysts (3 wt% Pt and 3 wt% In/Sn). Pure CO2 segregates the alloys while cofeeding CO2 and H2 largely retains Pt3Sn and Pt13In9 phases. On Pt:Sn, CO2 mainly interacts with H2 and carbon deposits via a Langmuir-Hinshelwood mechanism. Regenerative H2/O2 cycles cause Sn enrichment with a constant 0.9 nm NP size. Pt:In retained the Pt13In9 phase but showed NP growth from 0.8 to 2.1 nm, with greater susceptibility to alloy segregation and vaporization of In. This highlights Pt:Sn as more promising catalyst.

Element redistribution in the oxide scale during air oxidation of Kanthal AF alloy

Element redistribution in the oxide scale during air oxidation of Kanthal AF alloy

Study on the influence of corrosion degree on the high-temperature oxidation and combustion characteristics of AZ91, WE43 and ZE10 magnesium alloys

Based on magnesium alloy materials, different degrees of corrosion occur on the surface during use, and the corrosion state significantly affects its high-temperature oxidation and combustion characteristics. This study examines various corrosion conditions, investigates the impact of different corrosion levels on the combustion characteristics of magnesium alloys, and analyses the adsorption performance, state density, and oxygen atom diffusion barrier of alloy elements in AZ91, WE43, and ZE10 magnesium alloys based on first-principles calculations. It reveals the mechanism of the impact of each alloy element on the surface oxide film of magnesium alloys and explains the principles of the experimental results. The results indicate that with increasing corrosion time, temperature, and pressure, the time for the surface oxide film to rupture significantly decreases. In the six magnesium alloy systems of quantum calculations, the Mg–Re structure exhibits the strongest stability. According to adsorption energy calculations, the Mg–Al and Mg–Y systems show the best oxygen adsorption performance. Magnesium alloys doped with Y and Ce elements have the highest oxygen atom diffusion barrier. Hence, magnesium alloy systems doped with Y and Ce elements have a dense surface oxide film that remains undamaged even at very high temperatures, demonstrating excellent high-temperature corrosion resistance and providing an explanation for the experimental results.

Hypoeutectic Liquid Metal Printing of 2D Indium Gallium Oxide Transistors.

2D native surface oxides formed on low melting temperature metals such as indium and gallium offer unique opportunities for fabricating high-performance flexible electronics and optoelectronics based on a new class of liquid metal printing (LMP). An inherent property of these Cabrera-Mott 2D oxides is their suboxide nature (e.g., In2O3-x), which leads high mobility LMP semiconductors to exhibit high electron concentrations (ne >1019cm-3) limiting electrostatic control. Binary alloying of the molten precursor can produce doped, ternary metal oxides such as In-X-O with enhanced electronic performance and greater bias-stress stability, though this approach demands a deeper understanding of the native oxides of alloys. This work presents an approach for hypoeutectic rapid LMP of crystalline InGaOx (IGO) at ultralow process temperatures (180°C) beyond the state of the art to fabricate transistors with 10X steeper subthreshold slope and high mobility (≈18cm2Vs-1). Detailed characterization of IGO crystallinity, composition, and morphology, as well as measurements of its electronic density of states (DOS), show the impact of Ga-doping and reveal the limits of doping induced amorphization from hypoeutectic precursors. The ultralow process temperatures and compatibility with high-k Al2O3 dielectrics shown here indicate potential for 2D IGO to drive low-power flexible transparent electronics.

Performance optimization of AlN ultrasonic thin-film sensors deposited by RF magnetron sputtering

The AlN thin-film ultrasonic transducers were deposited by reactive RF magnetron sputtering technique. The effects of deposition parameters: target-substrate distance, argon-nitrogen flow ratio, deposition time, substrate temperature and radial distance from the deposition center on the ultrasonic performance of AlN thin films were studied. A metal electrode layer was deposited on the AlN film transducer to fabricate an ultrasonic temperature sensor, and the effects of the size and thickness of the electrode layer on the performance of the sensor were studied. Piezoelectric response measurements were performed in air over a temperature range of −60 °C–900 °C, and the dependence of ultrasonic response (time-of-flight and pulse echo amplitude) on temperature was analyzed. Long-term heat treatment in air at 750 °C for 128 h showed that the high-entropy alloy oxide protective layer could effectively delay oxidation of the AlN layer and improve the service life of the sensor.

Inhomogeneous distribution of oxides in various 9Cr ODS alloys and their mechanical performance at room temperature and 650 °C

Oxide dispersion strengthened (ODS) steels have been considered as promising structural materials for fusion reactors. In fabricating ODS steels, homogenous distribution of nano-sized oxides is always expected. In this work, Ti and C were respectively added into the 9Cr alloy with 2 wt% Mn, and the effects of individual Ti addition on microstructure and mechanical performance of ODS alloys are studied. Regularly distributed oxides were revealed in the 9Cr alloys fabricated by hot isostatic pressing (HIP), irrespective of alloying compositions, which indicates the strong interaction between oxides and phase interface. Alloying elements within the matrix can be incorporated into these regularly distributed oxides. Oxide nanoparticles will affect the phase transformation behaviors and the microstructure of as-HIPed 9Cr alloys without oxides is different from that of 9Cr ODS alloys. By performing post-HIP heat treatments, the matrix conditions of 9Cr ODS alloys can be adjusted, and ferritic and martensitic 9Cr ODS alloys are respectively obtained. With tensile tests at room temperature and 650 °C, effects of oxides and matrix conditions on 9Cr alloys were evaluated. It is found that individual Ti addition has a softening effect on the 9Cr alloys, despite that whether oxides are added. Simultaneous addition of Ti and C can improve the strength of 9Cr alloys evidently. Poor ductility at 650 °C is a critical issue for 9Cr ODS alloys, while the 9Cr alloys without oxides have favorable combination of strength and ductility at both room temperature and 650 °C.

Evaluation of Elevated Temperature Oxidation of Higher Manganese Ni-Resist Alloy

Nowadays Nickel was used mostly in battery, elevated temperature application and also corrosive environment. The boost of electric and hybrid vehicle had maximized the usage of Nickel as main composition in alloying industry. As such the Nickel price was at peak and become volatile to interest manufacturer. Among affected compound is Ni-Resist alloy. In this study, an alloy known as ductile Ni-resist alloy was modified to minimize its processing cost by decreasing its Nickel weight percentage. The modification was investigated in order to reduce nickel usage in the alloying composition so the alloying process cost can be minimized. More than 12 wt % chromium and manganese were alloyed with 10 wt % nickel during melting stage. Then, the evaluation of properties, oxidation behavior and its microstructure were examined. The results indicated more carbide was formed which later decreased tensile strength at elevated temperature. Oxidation resistance increased with addition of Mn/wt%. After oxidation at 765oC for 25 hours, there are oxide layers visible on the changed alloy.

Plastic recovery and strength enhancement of pre-deformed AZ31B magnesium alloy using transient strong pulse current

Magnesium alloy components are mainly used in aerospace and automotive fields, but poor deformation ability at room temperature restricts their application in other industries. To address this issue, electrically-assisted technology is employed to enhance plasticity of alloys. However, conventional method weaken strength and intensify surface oxidation of such alloys because of prolonged action of current. In view of the above, pre-deformation (PF) treatment in combination with transient induced pulse current treatment (TIPCT) is proposed in the present work so as to balance between plasticity recovery and strength of AZ31B alloy. The results show that the total elongation of PF sample and the corresponding TIPCT specimen first increases and then decreases with the increase in PF percentage under the same voltage. At the same PF percentage, the total elongation of PF and TIPCT specimens also presents the same trend as the voltage increases. At the same time, the total elongation in PF and TIPCT specimens is greater than that of the as-received sample. The maximum total elongation is achieved at the PF percentage of 16 % and the voltage of 6 kV, being 35 % higher than that in the as-received sample. The improvement in total elongation is due to activation of more non-basal dislocations induced by TIPCT and the appropriate amount of microcracks generated by PF. In addition, the TIPCT process also improves the yield strength even if the PF percentage and voltage are changed. Besides that, the work hardening induced by PF treatment and instantaneous action of TIPCT process are the key factors enhancing yield strength. Moreover, comprehensive mechanical properties of TIPCT sample are found to outperform those after direct pulse current treatment (DPCT) under the same PF percentage. Therefore, the proposed composite process provides a feasible scheme to enhance strength and elongation of Mg sheets.

Exploring multimetal interactions between FeNi3 alloy and Lu3Ga5O12 metal oxide for improved water splitting performance

The production of energy from fossil fuels generates greenhouse gases, leading to global warming and various environmental impacts. Extensive research into sustainable alternative fuels has identified hydrogen (H2) as a viable option. With net zero carbon emissions, hydrogen presents a promising solution for sustainable and renewable energy. This study employs a simple gel-matrix method to fabricate Ni-Fe alloy-based nanocomposites in alkaline media (1 M KOH). Achieving outstanding performance in hydrogen generation through the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with impressive turn-over frequencies (TOF) of 2.98 s−1 at 177 mV and 1.48 s−1 at 219 mV. Nanocomposite’s unique structure enhances electroactive surface area (347.5 cm2/gram), extending electrocatalytic active sites and durability to 60 h. It shows excellent performance, characterized by low Tafel slopes of 50 mV/dec and 37 mV/dec, and minimal overpotentials of 219 mV for the oxygen evolution reaction (OER) and 177 mV for the hydrogen evolution reaction (HER), reaching a current density of 10 mA cm−2. This study presents a method for synthesizing high-performance, sustainable metal-alloy/garnet hybrid electrocatalysts, offering a new frontier in design of next-generation materials for advanced energy conversion technologies.

Promoting effect of CO2 on NiCr oxidation: Atomistic origins based on first principles.

The adsorption and dissociation of CO2 on both perfect and oxygen-deficient α-Cr2O3 (0001) surfaces, alongside the subsequent incorporation of the resulting C into the oxide lattice and its impact on oxide growth, are investigated using first-principles calculations. Our findings reveal that oxygen vacancies significantly enhance CO2 adsorption and promote its stepwise decomposition into C and O atoms. The resulting C can spontaneously dissolve into the oxide lattice through the oxygen vacancies. The presence of bulk dissolved C in the Cr2O3 lattice substantially enhances the formation, migration, and clustering of oxygen vacancies in the bulk. These results provide an atomic-level understanding of how CO2 accelerates the oxidation of chromia-forming alloys, offering microscopic insights for controlling oxide growth and mitigating oxidation-induced degradation of high-temperature alloys.

A grey relational analysis of the micro arc oxidation process parameters and their effects on Ti-6Al-7Nb coating performance and corrosion resistance for biomedical uses

Abstract In current investigation micro arc oxidation of Ti6Al7Nb alloy was done to improve its surface properties and corrosion resistance. Mixture of Na2SiO3, Na3PO412H2O and KOH is used as electrolyte. MAO treated Ti6Al7Nb specimens were examined using x-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM) to examine their morphology and phase composition. It was observed that electrolyte composition is simultaneously included in the growing oxide layer during MAO process. From electrochemical study it was found that corrosion resistance of the Ti6Al7Nb increases during EIS testing in 0.9% NaCl solution. It was found that frequency, duty cycle, current and processing time effect the surface roughness, thickness, hardness and corrosion resistance of coating. Out of above mention parameters frequency and duty cycle has major impact on performance parameters. The objective of current investigation is to find out effects MAO process parameters on coating performance parameters such as coating thickness, hardness, surface roughness and corrosion resistance. At duty cycle of 50%, frequency 500 Hz, current 300 mA and processing duration 7.5 min, highest coating thickness 32.96 μm and surface roughness 3.3680 μm was obtained. Process parameters have the influence on pore size, biggest average pore size 3.8519 μm was obtained at duty cycle of 50%, frequency 500 Hz, current 300 mA and processing duration 7.5 min. Grey relational analysis is done to determine which process variable has the most influence on performance parameters. From grey relational analysis technique, it was observed that duty cycle 50%, frequency 500 Hz, current 300 mA, and processing time 7.5 min are ideal process parameters for higher coating thickness, hardness, surface roughness and better corrosion resistance. From grey relation analysis it was also found that frequency has most significant impact on performance parameters after that duty cycle, then current and at last processing time.

A novel pretreatment approach on titanium alloys for electroless nickel

To augment the wear resistance of the titanium alloy, electroless nickel (EN) is an effective method to strengthen the surface properties. However, the oxide layer on the surface of titanium alloy will inhibit the adhesion of EN. Meanwhile, the traditional pretreatment methods are cumbersome steps and time-consuming. To overcome these limitations, this study systematically explores a one-step pretreatment approach through amino tris(methylenephosphonic acid) (ATMPA) and HF, which is designed to improve the binding strength of EN. The results exhibit that the compact composite membrane with Ti-ATMPA and TiF3 are successfully prepared under pH 3.0, which has provided a pretreatment layer to replace the oxidation of titanium alloy during EN process, and the adhesion of EN coating (EN-3.0) based on the pretreatment layer reaches 22.46 MPa. The wear resistance of titanium alloy and EN plating system studied via a friction measurement, and the lowest wear rate exhibit in EN-3.0 plating (880.9 × 10-10mm3/Nm) that is lower than EN-traditional pretreatment with a decrease of 32 %. Moreover, the formation and catalytic model of medial layer are also discussed.

Influence of Process Modes of Plasma Electrolytic Oxidation of Aluminum Alloys on the Structure and Properties of Protective Oxide-Ceramic Coatings

Influence of Process Modes of Plasma Electrolytic Oxidation of Aluminum Alloys on the Structure and Properties of Protective Oxide-Ceramic Coatings

An innovative interlayer improving the interfacial connection of FeCoNiCrTi coating on copper surface

To improve the performance of copper surface, a FeCoNiCrTi high entropy alloy coating was first attempted to be prepared on copper substrate by plasma cladding. The obtained single-layer coating had a smooth and flat surface, but the interfacial connection was poor. Interfacial defect analysis results showed that the alloying elements dominated by Ti in the coating reacted with the CuO formed during the preheating process on copper surface. A large amount of TiO2 and other complex oxides were generated and distributed at the interface, which hindered the interfacial connection. After introducing a Ni60A interlayer, the interface reaction between FeCoNiCrTi alloy and copper oxide was avoided, and the inter-diffusion of elements was promoted, thus forming a good metallurgical bonding. Furthermore, due to the dilution effect of Ni60A interlayer, the performance of FeCoNiCrTi surface layer slightly decreased, but still far superior to the Ni60A coating. The microhardness of FeCoNiCrTi surface layer was about 10.7 times that of copper substrate. The wear loss of the developed coating is only 1/2 of that of the single Ni60A coating at 600 °C. This study has a great significance for extending the application of FeCoNiCrTi high entropy alloy coatings in surface strengthening on copper.

Comparative First-Principles Study of the Y2Ti2O7/Matrix Interface in ODS Alloys

Oxide-dispersion-strengthened (ODS) alloys generally exhibit extraordinary service performance under severe conditions through the formation of ultrafine nano oxides. Y2Ti2O7 has been characterized as the major strengthening oxide in Fe-based ODS alloys. First-principles energetic analyses were performed to investigate the structural, elastic and interface properties of Y2Ti2O7 in either Fe-based or Ni-based ODS alloys. Y2Ti2O7 has comparable elastic constants to bcc-Fe and fcc-Ni and similar elastic deformation compatibility in Y2Ti2O7-strengthened Fe-based and Ni-based ODS alloys is therefore expected. The Ni/oxide interface has generally better thermostability than Fe/oxide across the whole range of the concerned oxygen chemical potential. Further interface bonding and adhesion calculations revealed that Y2Ti2O7 can enhance the bonding strength of Ni/Y2Ti2O7 through d-d orbital interaction between the interfacial YTi layer and Ni layer, while the interface bonding between the Fe layer and YTi layer is weakened compared to the metal matrix. First-principles calculations suggest that Y2Ti2O7 can be a candidate for strengthening nano-oxides in either Fe-based or Ni-based ODS alloys with well-behaved mechanical properties for fourth-generation fission reactors and further experimental validations are encouraged.

The Influence of Si on the High-Temperature Oxidation of Near-alpha Titanium Alloys

The Influence of Si on the High-Temperature Oxidation of Near-alpha Titanium Alloys

On the mechanism and energetics of electrochemical alloy formation between mercury and platinum for mercury removal from aqueous solutions

Mercury pollution is an acute global concern threatening the health of humans and wildlife. Thus, there is a need for new and improved techniques to reduce emissions and remove toxic mercury from aqueous environments. Electrochemical alloy formation, specifically between mercury ions in aqueous solution and a platinum electrode, emerges as a promising solution. Through analysis of reaction mechanisms and energetics related to the formation and dissolution of the PtHg4 alloy, this study aims to deepen our understanding of the underlying processes of effective electrochemical mercury removal. Potentiodynamic measurements indicate rapid alloy formation at a clean platinum surface, proceeding with only trace amounts of metallic mercury on the surface. However, once the electrode surface has sufficient mercury coverage with an alloy thickness of around 1.5 nm, clear evidence of metallic mercury on the surface is observed. Furthermore, the amount of absorbed mercury on the cathode increases linearly in time. The onset potential for the alloy formation is experimentally determined using electrochemical quartz crystal microbalance with dissipation monitoring to be approximately 0.64 V vs. SHE, and the alloy dissolution (oxidation) onset potential is found to be approximately 0.98 V vs. SHE, at a mercury ion concentration of 10 mg/L. Density functional theory calculations are used to provide a theoretical value for the reversible potential from a thermodynamics perspective, yielding a value of 0.78 V vs. SHE at a mercury ion concentration of 10 mg/L. This value is in excellent agreement with the experimental results, suggesting an overpotential of about 0.14 and 0.20 V for the alloy formation and oxidation, respectively. These findings provide important information on the reaction mechanisms and overpotentials of the PtHg4 alloy formation and dissolution, which are key factors for development of large-scale mercury removal based on this technique, as well as fundamental understanding of the electrochemical alloy formation between mercury ions and platinum.