Microstructure Of Samples Research Articles

Surface analysis of industrial gate of a die-casting process mould retired from manufacturing site

Due to high heating and cooling casting cycles, the gate part, a crucial part of the mould, suffers from different casting problems. Therefore in the present study, an industrial gate surface of mould retired from a pressure die-casting industry after 60,000 casting cycles has thoroughly been analysed before and after being subjected to a novel enhancement heat treatment (EHT) by oil quenching technique. Here, the surface of different gate parts such as the die-block, runner, gate and casting area, of the industrial gate (IG) of a mould was precisely characterized by x-ray diffraction (XRD), by Fourier transforms infrared (FTIR) spectroscopy, microstructures, density, nanoindentation, hardness and magnetic measurement. This study predicted microstructures for the EHT samples. The novel EHT significantly recovered the mechanical and physical properties of the retired IG mould, particularly the nanohardness at die-block (from 6.83 to 12.89 GPa), gate (from 7.03 to 7.10 GPa) and casting (from 5.77 to 6.74 GPa) regions. After EHT, the internal stresses of the die material decreased and thus, its magnetic coercivity enhanced up to 223%. Therefore, the present study would help the mould manufacturer in predicting the mould’s life and condition during production.

Innovative Hygroscopic Material for Humidity Regulation: Diatomaceous Earth Composite Porous Ceramic

Urbanization in hot and humid regions such as southern China has increased the demand for comfortable indoor environments. In order to design a material for efficient passive indoor humidity regulation, this study investigates a composite material that combines the hygroscopic properties of salt and the adsorption capacity of diatomaceous earth (DE). Firstly, we prepared DE and boehmite into moisture-absorbing porous materials. Then, the initial DE-based sample was innovatively doped with SiO2 nanomaterials and loaded with LiCl to enhance the humidity regulation ability of the composite, especially in the adsorption and desorption ability of water vapour. The microstructure and phase composition of the composite samples were analysed, and we observed an increase in porosity, filling performance and capillary condensation upon the introduction of SiO2 nanoparticles. The hygroscopic salt loaded into the pores can absorb more water when exposed to the ambient humidity. This synergic effect can effectively improve the hygroscopic performance of the composite material while maintaining the stability of the physical and chemical properties. The optimized samples showed a moisture absorption rate of 28% in high-humidity environments, meeting moisture buffer value evaluation standards. The study’s findings lay the foundation for the future integration of these materials through advanced manufacturing technologies.

Environmentally-optimized photocatalytic NOX degradation in cement mortars utilizing recycled red brick and waste glass for sustainable management.

The rapid development of industrialization and urbanization generates huge amounts of solid waste and causes serious air pollution. Utilizing photocatalytic cementitious materials integrated with solid wastes presents an effective strategy for addressing urban air pollution and mitigating environmental impact. This study investigated the use of recycled red brick (RRB) and waste glass (WG) as aggregates in various proportions to replace conventional river sand, while employing nano-TiO2 as a photocatalytic agent at varying dosages to prepare photocatalytic cement mortar. The study evaluated the performance of the prepared samples in terms of compressive strength, hydration heat, water absorption, and NOx degradation. Advanced characterization techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric (TG), and mercury intrusion porosimetry (MIP), were employed to analyze the microstructure of samples. The results indicated that the incorporation of 3wt% TiO2 significantly accelerated cement hydration, resulting in the lowest water absorption rate (9.98%) and porosity (20.09%) as determined by MIP. SEM analysis revealed the incorporation of TiO2 within RRB matrix. Consequently, an increase in RRB content enhanced NOx degradation, achieving a peak reduction of 9% at an RRB: WG ratio of 75: 25. However, this ratio also led to a decrease in compressive strength (30.2MPa) due to the increased porosity of RRB. The development of photocatalytic mortar combining effective NOx removal with satisfactory mechanical properties highlights a resource-efficient method to recycle waste red bricks and glass, addressing both environmental pollution and sustainable waste management, which will provide guidance for government and industry to support timely decision-making on sustainable environmental policies.

Mineralogical Characterization of Mortars in Ancient Portuguese Tile and Embrechado Restorations: The Cases of Maceió (AL) and Salvador (BA)

ABSTRACT Portuguese tiles and embrechados rare colonial historical and artistic heritage capable of safeguarding the luso-bazilian cultural link over time. The inappropriate use of mortars to resettle these elements gives rise to diverse pathological manifestations. Therefore, this article aims to characterize mineralogical mortars used in ancient Brazilian restorations to ascertain their composition and the presence of cementitious material or other contamination. To this end, the microstructure of mortar samples from the Cloister of the Church and Convent of São Francisco (BA) and samples from the Bom Jesus of Martírios Church (AL) were mapped. In this way, the XRD, XRF and SEM/EDS methods were applied. The mortars originating from the construction period of the works (18th and 19th century), mostly made of lime, had a porous microstructure, presence of medium silicon content, absence of chlorine, high calcium oxide content and little contamination. Those from subsequent restorations, mostly cementitious, presented dense microstructure, medium aluminum oxide content, high silicon dioxide content, low to medium calcium oxide content and contamination. It is suggested, therefore, that there be continuous documentary recording of interventions throughout the useful life of the building, to evaluate the performance of practices and thus obtain data with a view to improving processes and readjusting materials. In this sense, preparing detailed reports on the condition of the work before, during and after rehabilitation becomes essential.

Corrosion resistance and electrical conductivity of Ta-modified Titanium bipolar plates for PEMFC

Titanium alloy bipolar plates hold significant promise for proton exchange membrane fuel cells (PEMFC) due to their high specific strength, excellent machinability and low density. However, the surface oxide film readily reacts with fluoride ions (F−) in service environments, forming porous, layered fluorotitanium compounds that compromise service life and stability. To overcome these limitations, this study utilised magnetron sputtering to deposit a 1 μm-thick tantalum (Ta) coating on TA1 titanium alloy substrates. The microstructure, corrosion resistance and electrical conductivity of the Ta-coated samples were systematically investigated and the mechanisms underlying their enhanced performance were analysed. Results showed that the Ta coating featured a dense, uniform microstructure with strong adhesion to the substrate and no detectable metallurgical defects. A gradient distribution of elements within the diffusion layer further strengthened the coating-substrate interface. Moreover, the formation of a Ta2O5 passivation film on the coating surface effectively inhibited fluoride-induced corrosion, reducing the contact resistance from 69.9 to 31.7 mΩ·cm2. These findings provide critical theoretical insights and practical guidance for enhancing the corrosion resistance and electrical conductivity of titanium alloy bipolar plates, paving the way for their broader application in PEMFC systems.

Dissimilar Gas Tungsten Arc Welding of (FeCoNi)96Al4 High-Entropy Alloy and Q235 Structural Steel.

(FeCoNi)96Al4 high-entropy alloy (HEA) is a new material with a strength similar to that of commercial Q235 structural steel, and its elongation is nearly three times greater than that of Q235 steel. Studying the welding process of the (FeCoNi)96Al4 HEA and Q235 steel is expected to further expand the application range of commercial Q235 structural steel and provide a foundation for the engineering application of the (FeCoNi)96Al4 HEA. This study focuses on the dissimilar welded components of (FeCoNi)96Al4 HEA and Q235 steel and analyzes the forming quality, microstructure, and mechanical properties of dissimilar welded samples under different currents. The results show that when the welding current is above 170 A, the 3 mm sheet metal is completely penetrated, and a well-formed weld seam is obtained. The base metal of the (FeCoNi)96Al4 HEA has an FCC structure, whereas the fusion zone of the weld seam is almost entirely a BCC structure. The microstructure of the weld seam exhibits needle-like and block-like grains that are different from those of the base metal. Owing to the difference in microstructure between the weld seam and the base metal, the average microhardness of the welded joint is twice that of the base metal. The strength of the dissimilar welded components reached 460 MPa, maintaining the tensile strength of the (FeCoNi)96Al4 HEA, which is similar to that of the Q235 structural steel. The elongation reached over 30%, which was significantly greater than that of the Q235 structural steel.

Time-varying quantitative characterization of reservoir microscopic pore structure based on digital core

The reservoir physical parameters (such as porosity, permeability, phase permeability, etc.) will change in the process of water injection development with the continuous flushing effect of high magnification water drive, which may have adverse effects on development if they cannot be accurately characterized. In this paper, we try to quantitative characterize the time -varying features of pore structure from the microscopic perspective. We used high-resolution 3D micro-CT (MCT) images to supplement the analysis of the physical properties of the rocks, and we used 3D pore network modeling technology to generate a 3D model of the rock samples. Then the relevant static micro-pore parameters are derived to study the changes of rock properties in different periods of development. Pore parameters were obtained to study the changes in porosity, permeability and pore size distribution of the rocks under different expulsion multiples, and to visualize the time-varying pattern of the microstructure of the rock samples under different stages of water injection. Under low-multiple water-driven conditions (10 PV), the physical properties of the rock samples did not change significantly, with an average facies change of only 1.98%. When reaching high multiples of water drive (more than 500PV), the change rate reaches more than 15%. And with the increase of water drive multiples, the distribution of pore radius and throat radius of rock samples showed an obvious right-shift trend, and the pores and throats increased, which was consistent with the results of CT scanning photographs. Equation fitting of the simulation results reveals that the core micro-parameters show an overall logarithmic relationship with the change of water drive. In this paper, a new application of Micro CT is provided to quantify the microstructure of water-injected reservoirs. By adopting this method, the effect of water-drive multiplicity on reservoir structure can be illustrated from a microscopic perspective. Meanwhile, compared with previous studies, this paper further investigates the effect of time-variation based on the qualitative analysis of the effect of time-variation of water-driven in reservoirs, and regresses time-variation curves and formulas through the changes in multiple water-driven states, which fills in the gap of the current lack of quantitative research and provides new understanding and optimization of the development of oilfields. The study will provide a new perspective for understanding and optimizing oilfield development.

Non-metal cocatalyst CNT-modified emerging g-C3N4 for enhanced treatment of waste drilling fluid filtrate.

Loading with non-metal cocatalysts to regulate interfacial charge transfer and separation has become a prominent focus in current research. In this study, g-C3N4/CNT composites loaded with non-metallic cocatalysts were prepared through in situ pyrolysis using urea and CNTs. Various characterization techniques, including transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), photoelectrochemical (PEC) analysis, fluorescence lifetime spectroscopy (TRPL), electron paramagnetic resonance spectroscopy (ESR), and photoluminescence (PL) spectroscopy, were employed to analyze the sample's microstructure, phase composition, elemental chemical states, and photoelectronic properties. The photocatalytic performance of the g-C3N4/CNT composite in the degradation of actual drilling hydraulic filtrate was evaluated under simulated sunlight irradiation, with the degradation results assessed through COD and chroma measurements. The findings indicate that in g-C3N4/CNT composites loaded with non-metal cocatalysts, the photocatalytic performance improves significantly as the CNT content increases. At a CNT mass fraction of 6.0%, the composite achieves optimal performance, with a COD degradation rate of 0.3742 h-1 and a chroma degradation rate of 81%. These results offer valuable insights into enhancing photocatalytic treatment of waste drilling hydraulic filtrate using g-C3N4-based non-metallic cocatalysts.

Comprehensive Investigation of Ti-Doped Sr3CoSb2O9 Triple Perovskite: Structural, Morphological, Optical, and Dielectric Characteristics

We report a comprehensive investigation of the doped Ti4+ and the pristine Sr3CoSb2O9 triple perovskite material. By conducting a solid-state reaction in the air at room pressure, a stabilized single orthorhombic Immm (SG 71) phase is obtained. For series samples Sr3CoSb2−xTixO9 (x = 0.0, 0.1, 0.3, 0.5), using Rietveld refinements of powdered x-ray patterns, we reach to the conclusion that the Ti4+ doping at B-site has considerable impact on its structural parameters. The microstructure of the series samples was studied using FESEM and associated with EDS mapping for compositional analysis. The optical characteristics studied via optical absorbance measurements indicate that with an increasing doping concentration of Ti4+, the optical bandgap increases for 0.1 sample and then decreases up to 1.50 eV for 0.5 sample. As a result, they can be considered potential candidates for technological applications like photocatalytic systems and solar cells due to their suitable bandgap values and optical absorption-related applications. The FTIR analysis aimed to examine the bond forms and vibrational modes of the synthesized samples. Moreover, the space charge polarization mechanism explains a detailed analysis of temperature-dependent dielectric properties in the 1 KHz-2 MHz frequency range. The dielectric loss behavior is described by the thermally activated relaxation process tailored by the Arrhenius law and characterized by doping Ti4+ ions into the material’s structure. The existence of Co in Co2+ and Co3+ oxidation states, while Sb3+ state is stabilized with doping confirmed by X-ray photoelectron spectroscopy research. The current study thereby advances our knowledge of how these materials’ structural, morphological, optical, and dielectric characteristics are related.

Experimental investigations into corrosion behaviour of DMLS manufactured Ti6Al4V alloy in different biofluids for orthopedic implants

Ti6Al4V alloy is widely used in the biomedical implants industry due to the excellent combination of biocompatibility, mechanical strength & corrosion properties. However, long-time use of Ti6Al4V implants may result in degradation at surge due to corrosive conditions of the human body. In this study, a three-electrode electrochemical cell was used to investigate the corrosion behavior of Ti6Al4V alloy parts manufactured using direct metal laser sintering (DMLS) and conventional cast technique. The corrosion behaviour of Ti6Al4V alloy was investigated in three different biofluids (corrosion media) physiological saline solution (PSS), simulated body fluid (SBF), and phosphate-buffered saline (PBS) using the potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) test. The relevant results showed that the DMLS-produced Ti6Al4V alloy has ~22% higher corrosion resistance than the conventionally cast Ti6Al4V alloy in all three biofluids. The microstructural study revealed that it is due to the fine grains and martensitic microstructure of DMLS-produced samples. Additionally, the DMLS-produced Ti6Al4V alloy in SBF has the lowest corrosion rate of 3.44×10−4 mm per year and exhibits the highest polarization resistance of 3364 Ω.cm2 due to the formation of a stable passive film. Apart from corrosion, the surface characteristics of the corroded samples were also studied using hardness and wettability tests. Additionally, scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction were also performed to understand the reason behind the results obtained. From all these results, it concluded that the corrosion resistance of the cast and DMLS-produced Ti6Al4V alloy in all three biofluids followed the order of PSS <PBS <SBF.

The Effect of the Heating Process on the Warm Deformation Behavior and Microstructure of Medium Mn Steel

This study investigates the effects of heating processes on the microstructure and deformation behavior of medium Mn steel during warm deformation. The samples treated by austenitization maintain an austenitic microstructure during deformation, which transforms into martensite upon cooling to room temperature. In contrast, the room‐temperature microstructure of samples deformed by direct heating to the deformation temperature is dependent on the deformation temperature: deformation above Ac3 results in a martensitic microstructure; deformation within the intercritical range (Ac1–Ac3) produces a mixture of ferrite, martensite, and austenite; and deformation below Ac1 yields a microstructure of ferrite and carbides at room temperature. When the microstructure only contains austenite during deformation, medium Mn steel exhibits excellent work‐hardening capability, characterized by a gradual increase in work hardening with strain until a dynamic balance between hardening and softening. Conversely, when ferrite is present in the microstructure during deformation, the flow behavior is dominated by ferrite, resulting in poor work‐hardening capability, with peak stress reached at low strain, followed by dynamic softening. Microstructure and stress–strain curve analyses reveal that, below 640 °C, ferrite exhibits higher strength than austenite. At 640 °C, the strengths of ferrite and austenite are approximately equal; above this temperature, austenite surpasses ferrite in strength.

Tracing the Formation of Femtosecond Laser-Induced Periodic Surface Structures (LIPSS) by Implanted Markers.

The generation of laser-induced periodic surface structures (LIPSS) using femtosecond lasers facilitates the engineering of material surfaces with tailored functional properties. Numerous aspects of their complex formation process are still under debate, despite intensive theoretical and experimental research in recent decades. This particularly concerns the challenge of verifying approaches based on electromagnetic effects or hydrodynamic processes by experiment. In the present study, a marker experiment is designed to conclude on the formation of LIPSS. Well-defined concentration depth profiles of 55Mn+- and 14N+-ions were generated below the polished surface of a cast Mn- and Si-free stainless steel AISI 316L using ion implantation. Before and after LIPSS generation, marker concentration depth profiles and the sample microstructure were evaluated by using transmission electron microscopy techniques. It is shown that LIPSS predominantly formed by material removal through locally varying ablation. Local melting and resolidification with the redistribution of the material occurred to a lesser extent. The experimental design gives quantitative access to the modulation depth with a nanometer resolution and is a promising approach for broader studies of the interactions of laser beams and material surfaces. Tracing LIPSS formation enables to unambiguously identify governing aspects, consequently guiding the path to improved processing regarding reproducibility, periodicity, and alignment.

Исследование микроструктуры высоконаполненной пленки для упаковки молочной продукции

High-filled, or high-barrier packaging materials are a promising direction of dairy packaging. These films provide safety, quality, and operational stability. In addition, they require no sophisticated equipment for recycling. Mineral calcium carbonate remains the most popular inorganic chemical filler. However, mineral-filled polymer compositions are understudied from the perspective of their structure and properties. These properties depend on the polymer base (binder), the mineral filler, its grinding, the technology of combining in the melt during extrusion, the dispersion of the filler in uncertain environment, etc. By studying the effect of filler concentration on the microstructure of polyethylene film samples, one can assess the dispersion of calcium carbonate in the polymer to reveal the processes behind the changes in the physical and mechanical properties of films. A series of previous studies featured a polyethylene film filled with 20–70% calcium carbonate. In this research, dihydroquercetin in concentrations of 0.5 and 1.0% served as an additional modifying component with antioxidant properties. The film samples were visually homogeneous. The method of scanning electron microscopy indicates a relatively uniform distribution of filler particles (50 wt%). The samples with 70 wt% showed a rather loose and uneven distribution of particles under the X-ray spectroscopy. The micrographs revealed crystalline particles of dihydroquercetin diffusing onto the surface of the packaging material.

Effect of Heat Treatment on Some Thermodynamics Analysis, Crystal and Microstructures of Cu-Al-X (X: Nb, Hf) Shape Memory Alloy

Abstract: Heat treatment is an important technique that can improve the properties of shape memory alloys. In this study the effect of heat treatment at three different temperatures (973 K, 1073 K and 1173 K) on some thermodynamics parameters, crystal structure, and microstructure of Cu_86 Al_12 Nb_2 and Cu_86 Al_12 Hf_2 (mass %) Shape Memory Alloy has been investigated. After heat treatment, the change in the thermal properties of the samples was determined using Differential Scanning calorimetry (DSC). The effect of heat treatment on the crystal and microstructure of the alloy samples were determined at room temperature using X-ray diffraction (XRD), Scanning Electron microscopy (SEM) device. The DSC result showed that in both samples the temperature hysteresis was decreased after heat treatment. Also grain size was decreased by increasing the treatment temperature in both samples. And finally, optical images represented that Hafnium (Hf) is more dissolved in the alloy compared to Niobium (Nb).

Cryogenic Treatment Effect on the Wear Resistance of AM60 Magnesium Alloy

Magnesium alloys were used as structural materials due to their low density. However, the poor wear behavior of magnesium alloys limits their use. In this study, AM60 magnesium alloy was subjected to deep cryogenic heat treatment to enhance the wear properties in dry and wet conditions with different loads. For this purpose, a deep cryogenic treatment at –196°C was applied for 48 h to the AM60 magnesium alloy. On the other hand, the wear performance of the treated sample was compared to the untreated sample using the pin-on-disc method at loads of 1 N, 2 N, and 3 N. The microstructure and wear groove were investigated using imaging techniques, while the XRD method characterized the phase modification. The results showed that the microstructures of the untreated sample drastically changed; the eutectic phase around the β phase was dissolved in the matrix, and some twins were formed after heat treatment. The XRD analysis confirmed the formation of a new β phase belonging to twins and an increase of the current β phase. Regarding hardness behavior, it increased by ~17.5% compared to the untreated sample after cryogenic treatment. In dry conditions, abrasive wear was the primary mechanism, and the wear resistance was better for the treated sample for all loads applied due to probably new phase formation. The treated sample exhibited lower wear resistance against the untreated sample, apparently due to the oxidative wear mechanism.

Lignin Polyurethane Aerogels: Influence of Solvent on Textural Properties.

This study explores the innovative potential of native lignin as a sustainable biopolyol for synthesizing polyurethane aerogels with variable microstructures, significant specific surface areas, and high mechanical stability. Three types of lignin-Organosolv, Aquasolv, and Soda lignin-were evaluated based on structural characteristics, Klason lignin content, and particle size, with Organosolv lignin being identified as the optimal candidate. The microstructure of lignin polyurethane samples was adjustable by solvent choice: Gelation in DMSO and pyridine, with high affinity to lignin, resulted in dense materials with low specific surface areas, while the use of the low-affinity solvent e.g acetone led to aggregated, macroporous materials due to microphase separation. Microstructural control was achieved by use of DMSO/acetone and pyridine/acetone solvent mixtures, which balanced gelation and phase separation to produce fine, homogeneous, mesoporous materials. Specifically, a 75% DMSO/acetone mixture yielded mechanically stable lignin polyurethane aerogels with a low envelope density of 0.49 g cm-3 and a specific surface area of ~300 m2 g-1. This study demonstrates a versatile approach to tailoring lignin polyurethane aerogels with adjustable textural and mechanical properties by simple adjustment of the solvent composition, highlighting the critical role of solvent-lignin interactions during gelation and offering a pathway to sustainable, high-performance materials.

Influence of Long-Term Immersion Tests on the Electrochemical Corrosion Behavior of an Ultrafine-Grained Aluminum Alloy

The long-term corrosion resistance of commercially pure aluminum (AA1050) processed by equal channel angular pressing (ECAP) was evaluated in a saline environment. The study compared the microstructure and corrosion behavior of ECAP-processed samples in route A with 1X, 4X, and 8X passes to an annealed sample using a 3.5% NaCl solution. Characterization techniques, including optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and electrochemical impedance spectroscopy (EIS), were employed. Results indicate that ECAP processing enhances the passive corrosion resistance compared to the undeformed sample. However, the improvement in corrosion resistance did not consistently increase with the number of ECAP passes. Factors such as the distribution of high- and low-angle grain boundaries, dislocation density, and fragmentation and redistribution of coarse dispersoid particles play a significant role in the corrosion behavior post-ECAP. Additionally, findings suggest that long-term immersion tests are required to obtain a more reliable electrochemical response.

Effect of Sintering Temperature on Microstructure and Properties of Zirconia Ceramics for the Needs of Nuclear Energy

The paper provides experimental results of obtaining high-density ZrO2+3%Y2O3 ceramics, which is promising for use as a matrix for immobilization of HLW. The effect of sintering temperature in the range of 1100...1650 °C on the microstructure of the sintered tablets was studied. Phase composition and microstructure of experimental samples were characterized by XRD and SEM. Grain size distribution analysis was carried out using the "Thixomet" image analyzer. Microhardness was determined using a metallographic complex LECO (USA), an inverted microscope IM-3MET and a hardness tester UIT HVB-30. It was established that increase in the sintering temperature leads to a significant increase in the average grain size (from 85 nm to 1000 nm) and increase in the density of the sintered tablets. Sintering temperature should be at least 1550...1650 ºС to produce high-dense ceramics (97...98 % of theoretical value). Obtained ceramics is characterized by high values of microhardness HV &gt; 12 GPa and crack resistance of 5.5...6.3 MPa·m1/2.

Structure and improved corrosion properties of MAO coating on Mg-5Gd-1Zn-0.4Zr formed under various current densities

To investigate the structure and corrosion properties of micro-arc oxidation (MAO) coating on Mg-5Gd-1Zn-0.4Zr (GZ51K) alloys for biomedical application, the alloy was MAO-treated using silicate electrolyte system under current density of 400, 600 and 800 mA/cm2 respectively. The microstructure, surface analysis and corrosion resistance of samples were evaluated by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, potentiodynamic polarisation, electrochemical impedance spectroscopy in SBF solution. The results indicate that the main phases of the MAO coatings were MgO, Mg2SiO4 and MgF2. With the increase of MAO current density, the thickness of the MAO coating decreased from 16.5 to 10.4 μm. When MAO current density is 400 mA/cm2, the specimen shows the best corrosion resistance with a four-order-of-magnitude decrease on Icorr ((1.95 ± 0.01) × 10−10 A/cm2), a four-order-of-magnitude increase on RP((7.67 ± 0.02) × 107 Ω cm2). Even though the thickness of the MAO coatings obtained with 600 and 800 mA/cm2 are very close, the corrosion resistance of the coating prepared under 800 mA/cm2 is better than that under 600 mA/cm2. Generally, MAO treatment can greatly slow down corrosion rate of the GZ51K alloy and keep uniform corrosion mode which is desirable for biodegradable implant applications.

Enhanced photocatalytic H2 generation via in-situ grown CuO-decorated TiO2 nanotubes on Ti-Cu alloys: A synergistic thermo-electrochemical approach

In the present study, we developed a thermo-electrochemical strategy to grow CuO self-decorated TiO2 nanotubes (TiNTs) on Ti-xCu alloys (x = 0, 2, 4, 6, and 8 wt%). The Ti-xCu metastable solid solution alloys were prepared by rapid quenching after solid solution heat treatment. Based on microstructural analyses, unlike all other samples, which consist of the α-Ti phase, the microstructure of the Ti-8Cu sample is biphasic, consisting of α-Ti and the Ti2Cu intermetallic compound. Electrochemical anodization of the Ti-xCu samples results in the in-situ formation of CuO nanoparticles decorating the TiO2 nanotubes on substrates containing Cu. As the Cu concentration increases, the order and integrity of the nanotube arrays gradually decrease while the Cu concentration within the nanotubes increases; however, the Ti-6Cu sample presents a satisfactory structural order and a uniform distribution of Cu. Based on XPS analysis, it has been determined that CuO is the main species decorating the TiNTs. This results in a maximum reduction of the band gap by approximately 0.5 eV for the Ti-6Cu sample compared to the pure Ti sample (3.35 eV), leading to improved absorption of visible light. Furthermore, the CuO species extended the lifetime of charge carriers, as demonstrated by electrochemical impedance spectroscopy. This combination of band gap reduction and enhanced charge carrier separation in Ti-6Cu resulted in a photocatalytic H2 production rate of 35.8 µL/cm2·h, more than ten times higher than the pure Ti sample. These findings hold significant promise for developing efficient and sustainable energy production systems.