In this study, an innovate strategy was proposed to modulate the microstructure and surface properties of micro arc oxidation (MAO) coatings by tailoring the cathode shape. Departing from the conventional flat cathode configuration, MAO coatings were prepared on a Ti surface using annular cathodes with different numbers of rings (1, 5, and10 rings). A comprehensive experimental investigation was conducted to systematically clarified the influence of cathode geometry on the growth behavior and surface properties of the coatings. The experimental findings unequivocally demonstrate that the ring-shaped cathode significantly improve the microstructure and properties of MAO coatings through the precise regulation of the micro arc discharge behavior. The coating formed under a 10-ring cathode mode (MAO-10) emerged as the top performer, showcasing an excellent comprehensive performance. In detail, MAO-10 sample manifested a notable reduction in porosity, a substantial increase in the thickness of the layer, a remarkable enhancement in wear resistance, a significant improvement in corrosion resistance, and a pronounced elevation in the substrate-coating interfacial bonding strength. This research not only provides a novel paradigm for the controlled modification of MAO coating but also substantiates the micro arc discharge cathode shape design engineering as a viable approach for achieving high-performance surface coating.

Developing high-temperature structural ceramics that simultaneously possess robust mechanical integrity and superior electromagnetic wave absorption (EWA) remains a formidable challenge for next-generation aerospace stealth technologies. In this work, we report the fabrication of SiO2@C/SiOC composites featuring multiscale gradient core-shell heterostructures through a synergistic integration of selective laser sintering (SLS), precursor impregnation pyrolysis (PIP), and nano-silica gel infiltration. By meticulously regulating the PIP cycles and heat-treatment temperatures, a hierarchical architecture was engineered in which a phase-tunable SiOC matrix accommodates micro/nano SiO2@C core-shell units. The optimized P6-1400 sample, derived from 6 PIP cycles and 1400 oC heat treatment, exhibits an exceptional performance balance: a flexural strength of 71.5 MPa, a compressive strength of 77.3 MPa, and a wide effective absorption bandwidth of 3.2 GHz at a minimal matching thickness of 3.1 mm. Systematic characterization and first-principles density functional theory calculations reveal that the significant 10.234 eV potential difference at the SiO2/C interface triggers intense Maxwell-Wagner-Sillars interfacial polarization and optimizes impedance matching. This multi-phase evolution, characterized by in-situ precipitated SiC nanocrystals and graphitic carbon, facilitates the formation of a complex conductive-dielectric loss network. Our findings provide a scalable and robust pathway for designing integrated structural-functional systems, positioning these composites as premier candidates for extreme-environment stealth engineering.

A niobium (Nb)-doped micro arc oxidized coating (MAO) was fabricated on a titanium substrate, and microwave hydrothermal (MH) post-treatment was applied to regulate the microstructure of the coating, aiming to enhance bone-implant osseointegration and antibacterial performance. The experimental results showed that the as-prepared MAO coating was composed of nanocrystalline TiO2 and a large amount of amorphous phase containing oxygen, Nb, calcium, phosphorus, and other bioactive elements. After MH treatment, short rod-like hydroxyapatite (HA) crystals were uniformly formed on the porous surface of the Nb-doped MAO coating, resulting in a well-ordered crystalline structure with tight interfacial bonding between the HA crystals and the MAO coating. The incorporation of Nb and MH post-treatment synergistically optimized the surface microtopography and chemical composition of the MAO coating, which markedly enhanced in vitro bioactivity, in vivo osseointegration, and antibacterial properties.

Micro-arc oxidation (MAO) coatings represent an effective surface modification strategy for extending the service life of zirconium alloys in pressurized water reactors. In this study, the oxide coating was in situ fabricated on zirconium alloy surface via MAO, and the effects of the different cathode configurations on the microstructure and properties of the coating were systematically investigated. All coatings were composed of tetragonal ZrO2 (t-ZrO2) and monoclinic ZrO2 (m-ZrO2), with m-ZrO2 being the dominant phase. Changing the cathode configuration from a plate to a ring significantly increased coating thickness, which further grew with the number of rings. The thickest coating was obtained with the 10-ring cathode configuration (MAO-4). The corrosion resistance and bonding strength of the MAO-4 coating also exhibited a similar increasing trend. The MAO-4 coating exhibited the lowest corrosion current density (3.88 x 10-7 A/cm2) and the highest corrosion potential (-0.102 V). Its bonding strength reached 13.63 N, which is 2.4 times higher than that of the coating prepared with the plate cathode. Moreover, this oxide coating exhibited outstanding radiation resistance, with damage levels reduced to 41.7 % of that of the uncoated zirconium alloy. These findings offer valuable theoretical and technical guidance for optimizing coating architectures in nuclear materials, with promising implications for improving the safety and stability of nuclear fuel cladding.

The biomimetic porous scaffold with excellent biomechanical compatibility was successfully created using 3D printing, micro arc oxidation (MAO) and microwave hydrothermal treatment (MHT). Initially, the scaffold's elastic modulus and compression strength could be adjusted by altering the pore size and type, resulting in a porous scaffold with a low modulus and high strength. The deformation process displaced a layer by layer fracture at a 45 degrees angle. Subsequently, a bioactive coating containing uniform and abundant of hydroxyapatite (HA) crystals was applied to the scaffold's surface through MAO and MHT. This coating did not significantly impact on the elastic modulus and compression strength. The difference in thickness between the inner and outer coating on the porous scaffold was primarily due to the variations in the micro arc discharge capability within the pore structure. Compared to MHT-treated STS and DoST, the MHT-treated DiST porous scaffold exhibited superior apatite-inducing ability, likely due to the abundant HA crystals formation on the surface. After a 6-week in vivo animal experiment, it was observed that the MHT-treated DiST porous scaffold demonstrated enhanced osseointegration ability, attributed to the high bioactivity of HA crystals and good mechanical compatibility. The research findings suggested a transformation in the bone in-growth pattern of the porous scaffold from distant osteogenesis to contact osteogenesis. Therefore, the biomimetic multi-scale porous scaffold with outstanding biomechanical compatibility could be a promising candidate for repairing bone defects.

A multilayer hard ceramic layer coated Ti composite was prepared through plasma electrolytic oxidation (PEO) combined with microwave hydrothermal (MH) treatment. After PEO and PEO-MH treatment, the in-situ formed ceramic coating significantly affected the deformation behavior of the Ti matrix, and the deformed slip bands appeared at a greater deformation on the Ti matrix during the tensile process; the deformation texture was also observed. Additionally, compared to pure Ti, the tensile strength, yield strength and elongation of the PEO and PEO-MH exhibited slight increases. The presence of the hard ceramic layer effectively inhibited crack propagation at the substrate/coating interface. Moreover, the self-interlocking effect at the coating/substrate interface generated by the corrosion grooves further optimized the stress distribution at the coating/substrate interface, and the ratio of amorphous to crystalline phases also played a crucial role in adjusting the deformation behavior of the Ti matrix. After MH treatment, the PEO-MH possessed more titania nanocrystalline clusters and a multilayer structure, promoting more uniform deformation of the Ti composite. Notably, an intriguing crystalline-to-amorphous phase transformation process was observed through in situ tensile tests and molecular dynamics simulation. This phase change, which occurs at the crack tip, effectively alleviates the stress concentration phenomenon, resulting in lattice distortion that ultimately enhances the strength of the Ti composite. This research provides crucial insights into the application of Ti composite in high-load environments and establishes a solid foundation for their broader utilization in the future.

To address the biological inertness of pure titanium implants, a composite coating with a strontium-doped hydroxyapatite (Sr-HA) phase and H2Ti5O11·H2O nanorods was engineered via ultrasonic-assisted micro-arc oxidation (UMAO) with hydrothermal treatment (HT). The ultrasonic field was applied to modulate the MAO discharge behavior, enhancing ion transport and coating formation. Structural characterization revealed that UMAO-HT coatings exhibited a lower anatase/rutile ratio and higher Sr-HA crystallinity, as compared to MAO-HT. In vitro simulated body immersion studies showed that UMAO-HT induced rapid apatite formation within 24 h, with a better apatite-inducing ability than the conventional MAO-HT. Density functional theory (DFT) simulations demonstrated that Sr substitution in HA lowered the (001) surface work function, enhancing Ca2⁺ adsorption energy and promoting apatite phase nucleation. This work reported the synergistic effects of ultrasonic-induced microstructure optimization and Sr-HA higher bioactivity, providing a mechanistic framework for designing next-generation bioactive coatings with enhanced osseointegration potential.

Acid electrolytic oxidized water (AEOW) has found widespread application in various fields due to its high sterilization efficiency, environmental sustainability, and ease of preparation. However, challenges such as the substantial costs associated with anode electrode preparation, the limited selectivity of chlorine evolution, instability, and significant energy consumption have hindered its advancement. To address the aforementioned issues, a design of TiO2-SnO2-RuO2 electrodes, with the objective of enhancing the carrier separation efficiency, was achieved by leveraging the composite effect of the TiO2-SnO2 heterostructure and SnO2-RuO2 Schottky junction structure (a metal-semiconductor interface facilitating charge separation). The porous structure of TiO2 and the rod-like structure of SnO2 facilitate the dispersion and anchoring of RuO2, thereby enhancing the activity of chlorine evolution reaction (CER) and stability of the electrode. The inhibitory effect of SnO2 on the oxygen evolution species on the surface of RuO2 enhances the chlorine evolution selectivity of Ru-SMT-1h. These designs reduce the specific energy consumption (SEC) of AEOW preparation and enhances the AEOW preparation quality. The prepared Ru-SMT-1h electrode exhibited a overpotential of 12 mV at 10 mA/cm2 for CER, accompanied by the highest chlorine evolution selectivity. The active chlorine concentration (ACC) of the prepared AEOW was 35.276 mg/L, and the killing rate of Staphylococcus aureus reached 100 %. Notably, the specific energy consumption was as low as 8.399 kW & sdot;h/kg during the AEOW preparation process. The Ru-SMT1h demonstrates exceptional stability, with a stability superior to 165 hours during AEOW preparation. The development of this high-efficiency AEOW preparation electrode is significant for public sterilization.

The mechanism of passivity breakdown on MoO3 3 films is studied. It confirms that the molybdate is generated easily on the surface of Mo immersed into the 3.5 wt% NaCl solution. The diffusion coefficient of oxygen vacancy in the MoO3 (as the precursor of molybdate) is approximately 10-(- 18) - 10(- 19 )cm(2)/s( 2 )/s by analyzing the Mott-Schottky curves and electrochemical impedance spectroscopy (EIS). It proves that this value obtained by experiment is corresponding to the calculated result based on the density functional theory (DFT). The diffusion barrier value of oxygen vacancy is 0.27 eV (26.05 kJ/mol) according to the diffusion coefficient at different temperatures. Both the experimental and calculated results demonstrate that the breakdown of MoO3 film is due to the adsorption of Cl-- on the surface, and Cl-- could increase the diffusion coefficient of oxygen vacancy, in turn, promoting the transport rate of point defects. A theoretical model was proposed for the breakdown of MoO3 passive film.

As an innovative finishing technique, electrolytic plasma polishing (EPP) is effective in improving the surface quality of Ti-6Al-4V alloy. In this paper, the microstructural evolution of Ti-6Al-4V alloy at different polishing voltages was investigated by means scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), transmission electron microscopy (TEM). Furthermore, the in-situ tensile test was performed via SEM to systematically characterize the mechanical properties and fracture behaviors. According to the research results, EPP significantly reduced scratches and crests on the surface at 300 V, reducing the average surface roughness to 1/24 of its original value. Subsequent to EPP treatment at 300 V, the ultimate tensile strength (UTS) of the Ti6Al-4V alloy peaked at 1094.5 +/- 25.2 MPa, with an elongation increase of approximately 16 % compared to the untreated sample. Finally, fracture modeling was performed through finite element simulation and in-situ tensile test. Initiated in surface microcracks, the crack developed rapidly along slip lines. The tensile damage caused by axial stresses extended from surface microcracks to the entire fracture, thus causing the material to fracture.

A SiC-SiO2 nano-composite coating was prepared via a novel liquid-phase plasma-assisted particle deposition and sintering (LPDS) method to enhance the oxidation resistance of the Ti-6Al-4V alloy. For comparison, a conventional plasma electrolytic oxidation (PEO) ceramic coating is fabricated on the Ti-6Al-4V alloy. The microstructure and formation mechanisms of both ceramic coatings were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results indicated that the thickness of the SiC nano-composite coating (similar to 40 mu m) increased significantly by 285 % compared to the PEO coating (similar to 14 mu m). The microstructural evolution and isothermal oxidation performance of the PEO and SiC-SiO2 nano-composite coating were comparatively investigated at 800 degrees C. After 100 h, the thickness gain of the SiC-SiO2 nano-composite coating (similar to 14 mu m) was lower than that of the PEO coating (similar to 26 mu m). The improved oxidation performance is primarily attributed to the outermost layer containing abundant SiC nanoparticles, which transform into SiO2 during the oxidation process and effectively inhibiting the inward penetration of oxygen.

Electrolytic Plasma Polishing (EPP), an innovative technology for polishing, has been utilized to improve the surface performance of 6061 aluminum alloys. An orthogonal experimental approach was carried out to investigate the multiple factors influencing the surface quality of aluminum alloys during the polishing process. The results indicated that peaks and scratches on the surface were successfully removed after polishing, with the average roughness reduced to 0.138 mu m, approximately 1/8 of the original roughness. Additionally, the EPP process enhanced the substrate's corrosion resistance and hydrophobicity. Finally, it is proposed that the mechanism of surface smoothing effect of EPP is attributed to the combined action of plasma chemical dissolution and cavitation forces peeling. This research indicates EPP as a promising finishing technique with considerable potential for enhancing the surface performance of aluminum alloys in electronic component applications.

In this study, a HfSi2-HfO2-SiO2 nanocomposite coating is prepared on a TiAl alloy via a one-step liquid plasma-assisted particle deposition and sintering (LPDS) method to enhance its ablation resistance. For comparison, a conventional plasma electrolytic oxidation (PEO) coating is fabricated on the substrate. The phase composition, microstructure, and elemental distribution of the coatings are investigated via scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Moreover, the ablative resistance of the coated samples under flame (> 1500 degrees C) ablation is evaluated using a methyl acetylene polypropylene gas spray gun. The results show that numerous HfSi2 particles are incorporated into the coating with partial oxidation to HfO2 during the LPDS, thus resulting in a larger thickness by approximately eight folds compared with the thickness of the PEO coating. After ablation for 360 s, 15.4 % of the PEO coating peeled off, whereas no exfoliation occurred on the HfSi2-HfO2-SiO2 nanocomposite coating. The nanocomposite coating exhibits the smallest thickness after ablation. The superior high-temperature ablation resistance of the nanocomposite coating is primarily attributed to the presence of an oxygen-consuming HfSi2 phase. Furthermore, the formation of HfO2 during high-temperature ablation effectively anchors the ceramic coating, thereby impeding crack propagation and hindering oxygen diffusion. Hence, LPDS is a prominent strategy for the design and fabrication of multifunctional ceramic coatings that incorporate various functional particles, which can enhance the thermal protection of alloy substrates.

The bacterial infection and poor osseointegration of Ti implants could significantly compromise their applications in bone repair and replacement. Based on the carrier separation ability of the heterojunction and the redox reaction of pseudocapacitive metal oxides, we report an electrically responsive TiO2-SnO2-RuO2 coating with a multilayered heterostructure on a Ti implant. Owing to the band gap structure of the TiO2-SnO2-RuO2 coating, electron carriers are easily enriched at the coating surface, enabling a response to the endogenous electrical stimulation of the bone. With the formation of SnO2-RuO2 pseudocapacitance on the modified surface, the postcharging mode can significantly change the surface chemical state of the coating due to the redox reaction, enhancing the antibacterial ability and osteogenesis-related gene expression of the human bone marrow mesenchymal stem cells. Owing to the attraction for Ca2+, only the negatively postcharged SnO2@RuO2 can promote apatite deposition. The in vivo experiment reveals that the S-SnO2@RuO2-NP could effectively kill the bacteria colonized on the surface and promote osseointegration with the synostosis bonding interface. Thus, negatively charging the electrically responsive coating of TiO2-SnO2-RuO2 is a good strategy to endow modified Ti implants with excellent antibacterial ability and osseointegration.

The construction of heterojunction photocatalysts is an excellent strategy for treating wastewater. Herein, a three-dimensional nanoflower-like TiO2/WO3 heterojunction photocatalyst was synthesized in situ on the surface of pure Ti substrate by plasma electrolyte oxidation (PEO) combined with a subsequent process, and the abundant network topology and lattice defects improved the adsorption performance of the photocatalyst. The construction of Z-scheme heterojunction not only promotes the separation of photogenerated carriers, but also enhances the light absorption ability and greatly improves the photocatalytic performance of photocatalysts. Under the synergistic effect of adsorption and photocatalysis, the degradation rate of MB reached 86.2% in 2 hours, which was significantly higher than that of the single-component photocatalyst. Finally, the synthesis of TiO2/WO3 heterojunction photocatalysts by this process and the reaction mechanism of heterojunction photocatalysts for the degradation of organic dyes were illustrated by combining experiments and DFT calculations. In conclusion, this study opens up a new process for synthesizing Z-scheme heterojunction photocatalysts, which brings new insights for photocatalytic treatment of water pollution.

The present study focuses on the formation of a hydroxyapatite-modified amorphous micro-arc oxidized (MAO) coating on the TiNbZrSn medium entropy alloy (TNZS MEA) through micro-arc oxidation and microwave hydrothermal treatment (MHT). The TNZS MEA primarily consists of a body-centered cubic (bcc) and hexagonal closed-packed (hcp) structure, exhibiting a low elastic modulus and high yield strength. A porous coating with an amorphous structure was obtained after MAO treatment, displaying superior corrosion resistance to MAOed Ti. After MHT, the MAOed TNZS MEA exhibited a multilayered structure consisting of three layers: an external growth layer (hydroxyapatite nanorods), an inner layer (amorphous and crystalline structures), and a substrate layer. This composite structure demonstrated enhanced superior apatite-inducing ability and corrosion resistance compared to MHTed Ti. The improvement in bioactivity and a slight decrease in corrosion resistance can be attributed to the incomplete structure of hydroxyapatite nanorods when compared to MHTed Ti. Consequently, this work successfully achieved a hydroxyapatite-modified multilayered oxidized coating with gradient perfor-mance in term of bioactivity and corrosion resistance, establishing it as a promising candidate material for hard tissue repair.

A plasma electrolytic polishing (PEP) technique was used to yield high-quality, precise surfaces of a TC4 alloy to ensure high reflectivity. An orthogonal experiment was carried out to investigate the multiple factors affecting the surface quality of the alloy during the polishing process. The factors that affect the surface roughness are ranked as follows based on the extent of the effect: temperature > time > voltage > depth. The surface crest and trough area decreases by an order of magnitude, and the average roughness of the alloy is reduced to approximately 1/27 of its original magnitude after PEP. The vapour gaseous envelope (VGE) ascends as the bubble expanded under the buoyant force of the electrolyte, causing the thickness of the plasma-gas layer close to the electrolyte-air interface to increase. Further, it is proposed that the mechanism of surface smoothing during the PEP process involves a combination of discontinuous discharge, electrochemical reactions, and dissolution, thereby finishing the surface of the TC4 alloy. This work provides an alternative to the surface finishing of TC4 by PEP, which is expected to be a promising technique for polishing complex structures, especially porous structures (such as 3D printed Ti, Cu, Al, Nb, Mg, and their alloys).

Tweaking the amount of precipitation and solute segregation is a successful strategy employed in modern micro-alloyed Mg alloys to tailor the microstructure and texture towards improved strength and formability. In the current work, Ca and / or Y are added to AZ31B alloy to examine the synergistic effect of various alloying elements on the texture and microstructure evolution during recrystallization and grain growth. The work examines the segregation behavior of alloying elements with respect to different matrix compositions and different grain boundaries and aims at gaining insights into favorable growth mechanisms that lead to texture modifications. The results demonstrate that in the AZW alloy (Mg-3Al1Zn-1.0Y wt.%) no Y solute was available in the matrix due to precipitation with Al and Mn. Hence, the texture of this alloy was very similar to typical magnesium basal textures. By the co-addition of Ca and Y in the AZWX alloy (Mg-3Al-1Zn-0.3Ca-1.0Y wt.%), the amount of Ca solute in the matrix remained large enough because Y replaced Ca in forming stable Al2Y precipitates. This resulted in a strong texture modification on the basis of Ca availability in solid solution and its co-segregation with Al and Zn at grain boundaries. The recrystallization kinetics in the AZWX alloy was therefore markedly retarded due to solute and precipitation related effects. Correspondingly, the AZW alloy showed the fastest recrystallization kinetics due to the lack of solute drag at the grain boundaries. The third alloy, AZX (Mg-3Al-1Zn-0.3Ca) containing Ca but no Y was in between because it demonstrated grain boundary segregation but less than the counterpart in the AZWX alloy. It is believed that the co-addition of Ca and Y to the basic MgAl-Zn alloy magnifies the synergistic role of solute elements in triggering anisotropic segregation among grain boundaries. This seems significant in modifying the grain boundary mobility characteristics during growth, which grants non-basal grains a growth advantage, resulting in annealing texture modification. This work sheds light on a successful magnesium alloying strategy by tailoring the type and level of precipitation and anisotropic segregation to achieve a desired texture modification. (c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The fabrication process for the uniform large-scale MoS2, WS2 transition-metal dichalcogenides (TMDCs) monolayers, and their heterostructures has been developed by van der Waals epitaxy (VdWE) through the reaction of MoCl5 or WCl6 precursors and the reactive gas H2S to form MoS2 or WS2 monolayers, respectively. The heterostructures of MoS2/WS2 or WS2/MoS2 can be easily achieved by changing the precursor from WCl6 to MoCl5 once the WS2 monolayer has been fabricated or switching the precursor from MoCl5 to WCl6 after the MoS2 monolayer has been deposited on the substrate. These VdWE-grown MoS2, WS2 monolayers, and their heterostructures have been successfully deposited on Si wafers with 300 nm SiO2 coating (300 nm SiO2/Si), quartz glass, fused silica, and sapphire substrates using the protocol that we have developed. We have characterized these TMDCs materials with a range of tools/techniques including scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), micro-Raman analysis, photoluminescence (PL), atomic force microscopy (AFM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and selected-area electron diffraction (SAED). The band alignment and large-scale uniformity of MoS2/WS2 heterostructures have also been evaluated with PL spectroscopy. This process and resulting large-scale MoS2, WS2 monolayers, and their heterostructures have demonstrated promising solutions for the applications in next-generation nanoelectronics, nanophotonics, and quantum technology.