Although composite titanium salt coagulants demonstrate excellent performance, there are still some issues and challenges that need to be addressed. Future research can focus on the following aspects: (a) Enhancing Adaptability to Real Water Bodies. Currently, the complex composition of various actual water bodies imposes higher demands on the application of composite titanium salt coagulants. To ensure stable and efficient coagulation performance under complex water quality conditions, future efforts should focus on developing novel composite titanium salt coagulants with stronger specificity and broader applicability, thereby meeting the needs of more complex and demanding application scenarios. (b) Lower- Cost Preparation of Composite Titanium Salt Coagulants. At present, the preparation of composite titanium salt coagulants largely relies on complex processes such as SAT, ED, and sol-gel methods, which hinders their large-scale application. Future research should aim to develop simpler, greener, and more economically viable preparation pathways—for instance, utilizing industrial by-products or waste materials as raw materials—while optimizing the preparation process to reduce energy consumption and production costs. (c) Ensuring Ecological and Health Safety. Current research on the toxicity assessment of titanium-based coagulants has predominantly focused on TiCl₄ and Ti(SO₄)₂. Future studies should strengthen investigations into titanium residue and its ecotoxicological effects during the use of composite titanium salt coagulants. Meanwhile, it is essential to employ a wider range of aquatic organisms (e.g., fish, shellfish, and aquatic plants) for ecotoxicity studies, and to further explore the migration, transformation, and long-term accumulation of residual titanium in water bodies and organisms. This will provide a scientific basis for comprehensively safeguarding water environments and human health.

High-temperature vibration sensors are indispensable key components for the health detection of core equipment in fields such as aerospace and nuclear energy. The BiScO₃-PbTiO₃(BS-PT) system has attracted much attention due to its high Curie temperature (T_C≈450 ℃) and excellent piezoelectricity (d₃₃≈450 pC/N). However, the poor insulation properties of this material hinder its application in high-temperature vibration sensors because high electrical resistivity (ρ) and a long time constant (τ) are critical to prevent thermal runaway and ensure signal integrity. Manganese (Mn) doping is a commonly used modification method for piezoelectric ceramics. Previous studies on Mn-doped BS-PT were controversial regarding the valence state distribution and substitution positions of Mn ions, which could not be conducive to the design of high-temperature piezoelectric ceramics with the collaborative optimization of multiple electrical parameters. Therefore, this work was to clarify the defect chemical mechanism associated with manganese doping through refined structural characterization combined with electrical performance analysis, and to obtain the modified BS-PT piezoelectric ceramic components suitable for high-temperature vibration sensors.

0.365BiScO₃-0.635PbTiO₃-x% MnO₂ (BSPT-x% MnO₂, x=0.00, 0.01, 0.25, 0.50, 0.75, 1.00, 1.25, 1.50, 1.75, 2.00) ceramics were synthesized by a conventional solid-state reaction method. The powders were firstly calcined at 800 ℃ for 2 h and then sintered at 1050 ℃ for 2 h. The phase composition was analyzed by X-ray diffraction (XRD). The rietveld refinements were performed using a software named GSAS. The microstructure and elemental distribution were examined by scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS). The average grain size was estimated by a software named Nano Measurer. The Mn valence states were determined by X-ray photoelectron spectroscopy (XPS). For electrical measurements, poled samples (120 ℃, 5 kV/mm, 30 min) were used. The piezoelectric coefficient (d₃₃) was measured by a model CAS ZJ-6A quasi-static meter. The electromechanical coupling coefficient (k_p) was measured by a model Agilent 4294A impedance analyzer. The temperature-dependent dielectric properties were measured by a model Agilent E4980A LCR analyzer. The high-temperature DC resistivity (ρ) was measured by a model Keithley 6517B high-resistance electrometer. The in-situ d₃₃ was measured by a model Julang TZFD-600 variable temperature quasi-static d₃₃ measurement system.

The Mn doping mechanism and high-temperature performance of BS-PT ceramics are systematically clarified. The XPS results confirm the coexistence of Mn²⁺ and Mn³⁺. To quantitatively verify the substitution site, the rietveld refinement reveals a non-monotonic evolution of unit cell volume. Based on the EDS evidence of Sc segregation without Ti precipitation, Mn ions preferentially substitute for B-site Sc³⁺. The dominant aliovalent substitution introduces defect dipoles accompanied with strong local random electric fields, significantly enhancing a relaxor behavior, while triggering a "hardening" effect that reduces tanδ and ε_r. The decoupling of piezoelectric and dielectric properties is achieved in specific compositions due to the grain boundary effect compensating for the hardening effect, especially obtaining the optimal piezoelectric voltage constant (g₃₃) at the component with x of 1.00. For high-temperature capabilities, the optimal composition (x=1.00) demonstrates a superior stability, with in-situ d₃₃ variation remaining within 20% up to 400 ℃. The thermally stable defect dipoles effectively trap oxygen vacancies, leading to a high resistivity of 10⁹ Ω·cm and an enhanced time constant of 0.072 s at 350 ℃. Consequently, the ceramic with x of 1.00 exhibits a high g₃₃ of 0.012 V·m/N when evaluated at a unified service temperature of 350 ℃, which is 50% higher than that of the undoped counterpart. These results indicate that the modified ceramic achieves an optimal balance of sensitivity and insulation for high-temperature vibration sensors.

This work clarified the Mn doping mechanism in BS-PT ceramics. The results of correlative XPS, Rietveld refinement, and EDS analysis confirmed that Mn ions could preferentially substitute for B-site Sc³⁺. The dominant aliovalent substitution induced a hardening effect, while the recovery of d₃₃ was dominated by grain size restoration. The optimal composition (x=1.00) exhibited a robust stability with d₃₃ variation within 20% at 400 ℃. The thermally stable defect dipoles could obtain a high resistivity (10⁹ Ω·cm) and time constant (0.072 s) at 350 ℃. Meanwhile, a superior piezoelectric voltage coefficient (g₃₃) of 0.012 V·m/N was achieved at 350 ℃, which was 50% higher than that of the undoped counterpart, validating its potential for high-temperature sensors.

The multi-levelled control of multiphase microstructures by the reactive-melt is analogous to "dissolution-reprecipitation" process for liquid-phase sintering in the transformable microstructures of silicon-based ceramics, with silicate-melts and glassy phases at grain boundaries. In contrast to the monolithic ceramics of high-entropy MB₂ and MC, the multi-levelled solid-solutions and the associated multiphase microstructures of M^ⅠB₂-M^ⅡC UHTCs offer ample and novel routes for comprehensive control, better optimization and further enhancement in high-performance UHTCs. The coherent hetero-interfaces created from the multi-levelled solutions via solid-state phase-separations and their interconnected dislocation networks can further improve the high-temperature strength, and those phase-boundaries, grain-boundaries, and solute-segregates allow a precise control over the multiscale semi-coherent microstructures. The research on this synergistic evolution of intergranular phases and sintering-melts at high temperatures along with the multiphase transformation has a promising potential for future advancements in ceramic genomes and levelled structure-property relationship for multiphase UHTCs governed by solid-solutions as enthalpy-regulation.

Bismuth-doped fibers (BDFs) have already proven themselves as active materials that can be used to develop optical devices with unique characteristics in previously inaccessible spectral ranges. Optical amplifiers based on these active fibers exhibit high gain and low noise across all telecommunication spectral bands (from O- to U-band), while BDF-based lasers offer the benefits of high efficiency and wide wavelength tunability. However, existing research still faces significant challenges in achieving a reliable technology for reproducing the parameters of BDFs, as well as in fabricating optical fibers with increased Bi concentrations and low unsaturable losses. Developing a high-gain, ultra-wideband amplifier that can be effectively integrated into existing communication systems remains a challenge. Future research should focus on balancing cost, energy efficiency, and device performance, which can be partially addressed by optimizing the BDF design and the device itself. All of this is necessary to meet the growing demand for high-speed data transmission over fiber-optic communication systems, which is crucial in the context of rapidly evolving artificial intelligence technologies. In this regard, the ability to utilize all available telecommunications bands appears very promising. We believe that progress in this area will undoubtedly lead to the development of optical communication systems with significantly increased bandwidth, where bismuth-doped optical amplifiers are key components. Moreover, thanks to ongoing advances in optical materials and process technology, bismuth-doped fiber technology can pave the way for efficient, reliable, and scalable solutions for next-generation fiber-optic systems.

In transition towards a decarbonized energy system globally, hydrogen plays a crucial role as a zero carbon energy carrier. In this context, solid oxide electrolysis cell (SOEC) technology with its advantages in high-temperature operation significantly reduces material costs and improves overall system energy efficiency, compared to low-temperature solutions such as alkaline and proton exchange membrane electrolysis. SOEC system adopts a non-precious metal ceramic structure. When operating at 650-1000 ℃, electrochemical kinetics acceleration mechanism achieves a conversion efficiency of > 80%, providing a feasible approach to reduce cost of green hydrogen leveling. The existing domestic demonstration projects are limited to a scale of tens to hundreds of kilowatts, and the commercial implementation needs to break through bottleneck of "three highs and one low", thus increasing power density of fuel cell stack, extending its service life, and optimizing system integration, while reducing assets and operation and maintenance costs. Solving these obstacles requires collaborative efforts in three major fields, and innovation in materials and structures must break through conventional design framework of electrodes, electrolytes, and sealing glass. With precise microstructure design and interface stress control, system can maintain a high current density of 2 A·cm^-2, while controlling degradation rate at 1 mV per thousand hours, significantly extending lifespan of battery pack. Multi-energy coupling optimization is crucial, which requires integrating the SOEC with industrial waste heat and renewable resources, thus utilizing low-grade thermal energy (i.e., 200-300 ℃), efficiently offsetting internal heating demand, reducing external electricity consumption by approximately 30%, and comprehensively improving energy utilization efficiency. For those localized supply chains, establishing a complete domestic production capacity from precursor powder to single cell manufacturing, stacking and assembly to system integration is particularly crucial. The goal is to control stacking cost at RMB 2500 per kW and achieve an operating life of 5×10⁴ h, laying a foundation for large-scale applications. At present, although the SOEC has significant energy efficiency advantages, its promotion and application still face multiple constraints, i.e., gradual decay of oxygen electrodes under high temperature and high vapor partial pressure, mechanical and electrochemical damage caused by power fluctuations, and daunting initial capital investment. Subsequent exploration should focus on preparing new electrode materials with a higher stability, establishing flexible thermoelectric synergistic regulation mechanisms to adapt to fluctuating renewable energy, and promoting standardization and cost reduction and efficiency improvement throughout entire industry chain. The cost of photovoltaic and wind power continues to decrease, coupled with increasing demand for green hydrogen in chemical and metallurgical fields. Solid oxide electrolysis cell technology is expected to be widely applied in "electricity hydrogen ammonia/methanol" integrated system, distributed energy system, and sustainable refining scenarios. This technology will undoubtedly become a key pillar technology supporting the dual carbon goals in China.

The issue of electromagnetic pollution has become increasingly severe with the development of the electronic communication technology. The excessive electromagnetic waves pose risks to the national security and the human health in daily life. Consequently, wave-absorbing materials have gradually garnered public attention. Biomass, with its inherent network structure, can be used to produce porous carbon for addressing electromagnetic pollution. Among various biomass sources, coconut shells are widely distributed in China and have long been treated as agricultural by-products or waste. Recycling and utilizing coconut shells to prepare wave-absorbing materials not only helps mitigate electromagnetic pollution but also offers a new approach for the high-value application of agricultural by-products such as coconut shells.

The experimental materials included coconut shells purchased from Hainan Wenchang Coconut Shell Co., Ltd.. Potassium hydroxide (KOH), calcium carbonate (CaCO₃), hydrochloric acid (HCl), and paraffin wax (C₂₅H₅₂) purchased from Shanghai Titan Scientific Co., Ltd. The coconut shells were processed into 1-2 cm pieces, cleaned, and dried at 80 ℃ for 24 h. The dried pieces were then ground into powder using a pulverizer and sieved through a mesh with an aperture of 250-300 μm. The coconut shell powder was mixed with CaCO₃ and KOH at mass ratios of 1.0∶1.0∶0.5, 1∶1∶1, 1∶1∶2, and 1∶1∶3, respectively. The mixtures were uniformly ground in a pulverizer to obtain alkalized coconut shell powder, which was subsequently dried. The dried alkalized powder was placed in a tube furnace, which was purged with nitrogen gas (N₂), and then carbonized at 700 ℃ for 2 h. The resulting product was neutralized with hydrochloric acid (HCl) under magnetic stirring for 12 h, washed with deionized water until neutral, and finally dried at 80 ℃ for 24 h , then the coconut shell-based porous carbon was obtained.

In this study, coconut shell was utilized as the carbon source, based on its inherent multi-level network structure and high carbon content. Using KOH and CaCO₃ as dual activators, a one-step carbonization method was employed to prepare coconut shell-based carbon wave-absorbing materials with superior microwave absorption performance. Compared to pure coconut shell carbon and coconut shell carbon activated solely with an equal mass of KOH, the sample prepared with dual activators exhibited more uniform surface pore distribution and hierarchical structure. This specific structure played a critical role in enhancing the electromagnetic wave absorption performance. Consequently, the dual-activator method offered a novel approach for preparing porous carbon materials with complex three-dimensional micro/mesoporous structures. At 700 ℃, the gradual addition of activator resulted in enlarged pores and increased defects in the porous carbon structure, ultimately causing pore collapse. Higher activator concentrations led to larger pore diameters, which reduced electromagnetic wave reflection efficiency and consequently diminished microwave absorption performance.

A coconut shell-based porous carbon material with excellent wave-absorbing performance was successfully prepared via a one-step carbonization method combined with a dual-activator (KOH and CaCO₃) activation process. By adjusting the mass ratios of KOH to CaCO₃, the pore structure of the resulting carbon material was modulated, leading to varied electromagnetic wave absorption properties. The optimal absorption performance was achieved under the conditions of a carbonization temperature of 700 ℃ and a mass ratio of coconut shell powder : CaCO₃∶KOH = 1∶1∶1. The material obtained under these conditions exhibited a minimum reflection loss (RL_min) of -45.79 dB at a sample thickness of 5.0 mm and a frequency of 5.12 GHz. This study utilized a simple one-step carbonization process to produce effective wave-absorbing materials with abundant coconut shell waste, providing valuable theoretical guidance for the development of high-performance absorbers and significantly broadening the application prospects for biomass-derived wave-absorbing materials.

Across diverse application domains, glass materials are engineered to meet increasingly stringent criteria with regard to performance, reliability, and sustainability. It is worth mentioning that the most advanced display modules and semiconductor chips are currently manufactured mostly in East Asia. This geographic imbalance provides unique opportunities and challenges for both of the glass industry and academia. New applications such as ultra-thin glass for flexible display modules and glass core substrate for semiconductor packaging will present unprecedented functionalities and benefits to glass materials.

With the continuous pursuit of higher efficiency and larger thrust-to-weight ratio in aero-gas-turbine engines, the turbine inlet temperature has already exceeded 1300 ℃, imposing increasingly stringent requirements on the thermal resistance and protective capability of hot-section structural materials. Environmental barrier coatings (EBCs) have become a crucial technology to ensure efficient and reliable service of ceramic matrix composite (CMC) turbine components under such extreme working conditions. However, the service environment of EBCs is exceptionally complex. Coatings are continuously exposed to corrosive gaseous species within combustion products, among which the ingression and reaction of molten calcium-magnesium-aluminum-silicate (CMAS) deposits represent one of the most detrimental degradation mechanisms.

To mitigate CMAS-induced deterioration, numerous strategies have been proposed, including compositional modification (doping, high-entropy ceramics), structural design optimization (multilayer or graded coatings), and surface engineering (laser or ion beam treatments). Although these approaches can improve corrosion resistance to some extent, most of them inevitably alter the coating chemistry or structural system, which tends to induce thermal expansion mismatch with the substrate and promotes premature failure during thermal cycling. Therefore, how to enhance CMAS-corrosion resistance while maintaining thermomechanical compatibility remains a critical challenge. Laser glazing (LG) is a surface-modification technique that locally melts and rapidly solidifies the coating surface to form a dense glaze layer. It improves surface compactness and seals microdefects without altering the coating composition, thereby presenting a promising method for improving CMAS-corrosion resistance. In this work, laser glazing is introduced to enhance the CMAS-resistance of EBCs, and the CMAS-corrosion behavior together with the underlying improvement mechanisms are systematically investigated.

SiC ceramic substrates were purchased from Fuzhou Pengkun Optoelectronics Co., Ltd. The samples were cylindrical (diameter 25.4 mm, thickness 3 mm) and mechanically grit-blasted prior to coating deposition. Yb₂Si₂O₇/Si (YbDS) EBCs were deposited on the substrates by atmospheric plasma spraying (APS). Commercial Yb₂Si₂O₇ and Si powders (Shanghai Shuitian Materials Technology Co., Ltd.) were used, and the bond coat consisted of 90% (in mass fraction) Si and 10% Yb₂Si₂O₇. A picosecond ultraviolet pulsed-laser system was subsequently applied to modify the surface microstructure of APS YbDS coatings. Four sets of parameters (L1-L4) were obtained by adjusting the laser power (6 W or 20 W) and scanning speed (100-300 mm/s). CMAS bulk material was synthesized by high-temperature melting. CMAS powder was mixed with ethanol and uniformly brushed onto the coating surface, followed by drying to achieve a coating mass of 5 mg/cm². The coated samples were exposed at 1350 ℃ for 10, 60 h, and 120 h. After corrosion, the evolution of microstructure and phase composition was analyzed to reveal the degradation behavior.

The APS-prepared YbDS coating exhibited a surface roughness of ~3.7 μm and a porosity of ~4.87%, with typical APS defects such as pores, unmelted particles, and microcracks. After laser glazing, four modified surfaces were obtained. Among them, sample L2 demonstrated the most favorable structural morphology and was selected for subsequent corrosion tests. The L2 coating showed a reduced surface roughness of ~1.824 μm and a homogeneous, dense glaze layer of ~9.6 μm thickness. Moreover, the glazed surface phase completely transformed from Yb₂Si₂O₇ to Yb₂SiO₅. During CMAS corrosion, the YbDS coating surface was continuously covered by a loose mixture of Ca₂Yb₈(SiO₄)₆O₂ and CMAS residual glass. In contrast, the laser-modified L2 coating was covered by a compact Ca₂Yb₈(SiO₄)₆O₂ reaction layer. After corrosion, both coatings displayed Ca₂Yb₈(SiO₄)₆O₂ and secondary Yb₂Si₂O₇ phases; however, their structural evolution differed significantly. After 120 h of corrosion, the YbDS coating suffered severe structural degradation, including interfacial delamination and partial spallation in cross-sectional observations. Conversely, the L2 coating maintained structural integrity, and its corrosion depth was consistently lower under the same conditions.

The improved CMAS resistance of the L2 coating can be attributed to three synergistic mechanisms: Surface densification, Laser glazing produced a dense, continuous glaze layer that sealed APS-induced pores and cracks, effectively delaying CMAS infiltration pathways; Protective reaction-layer formation, The Yb₂SiO₅ glaze reacted with CMAS to form a dense Ca₂Yb₈(SiO₄)₆O₂ layer, which further hindered molten-salt penetration ;Enhanced non-wettability, Laser glazing significantly reduced surface roughness and improved hydrophobicity. As a result, molten CMAS appeared as aggregated hemispherical droplets rather than fully spreading, making it more easily removed by high-velocity gas flow during service.

The findings of this study demonstrate that laser glazing effectively enhances the CMAS-corrosion resistance of YbDS coatings. The improvement originates from the combined effects of surface densification, pore/crack sealing, phase transformation to Yb₂SiO₅, and subsequent formation of a compact Ca₂Yb₈(SiO₄)₆O₂ reaction layer during corrosion. Additionally, the smoother and less wettable glazed surface reduces the adhesion and spreading tendency of CMAS, enabling molten deposits to be removed more easily under aerodynamic forces. As a result, the degradation rate of the coating is substantially suppressed, delaying the propagation of corrosion-induced cracks and maintaining structural integrity over prolonged exposure. Moreover, the laser-induced modifications do not alter the coating architecture or introduce thermal expansion mismatch, making the technique compatible with existing EBC design frameworks. Overall, laser glazing represents a promising strategy for improving the durability and service lifetime of EBC systems in next-generation high-temperature aero-engine applications.

It is effective to introduce self-healing components, network intermediate oxides and rare-earth silicates into the SiC_f/SiC composite matrix to fill the pores and cracks of the material via generating self-healing components during the oxidative corrosion process, and forming a dense oxide layer on the surface of the material to resist further erosion by the oxidizing medium, thus improving the water and oxygen corrosion resistance of the composites. However, there are still some challenges. Firstly, the research on the oxidation corrosion mechanism of composite materials is still in-depth, and there is a lack of data on oxidation kinetics, oxidative corrosion rate and oxidative corrosion depth, and the basic research on the damage evolution mechanism of materials in different environments is still relatively weak. It is thus necessary to construct a complete and reliable performance database of SiC_f/SiC composites modified with different substrates, clarify the oxidative corrosion damage mechanism, and provide design parameters and theoretical support for the practical application of composites. Secondly, the effective temperature range of a single modified substance to improve the oxidative corrosion performance of composites is limited. The temperature range of B group is below

1000 ℃, and the temperature range of Al group is 1000-1300 ℃. The synergistic effect of multiple modification strategies is explored via introducing multiple modified substances into the matrix of composites at the same time. It is expected to achieve the oxidation and corrosion properties of SiC_f/SiC composites in a wide temperature range and achieve a long-life cycle protection. Finally, it is also worth to develop new preparation processes, such as nano-infiltration and transient eutectic (NITE), or use hybrid processes to achieve material densification and improve the performance of SiCf/SiC composite substrates while modifying them.

Ti-6Al-4V (TC4) titanium alloy is widely used in industrial and biomedical fields due to its excellent mechanical properties and biocompatibility. However, its inherently poor wear resistance significantly limits its further application. Plasma electrolytic oxidation (PEO) as a green and efficient method for in-situ fabrication of ceramic coatings with strong adhesion to the substrate, offering an excellent solution for surface protection of titanium alloys. However, conventional PEO coatings exhibit a porous outer layer composed mainly of high friction TiO₂, resulting in insufficient wear and friction reduction performance. To overcome this limitation, incorporating MoS₂ (a solid lubricant with a layered structure) can be introduced to the PEO coating to form a composite coating, which has been demonstrated as an effective approach to enhance its tribological properties. Although previous studies have confirmed the potential value of TiO₂/MoS₂ composite coatings in antifriction, most studies rely on high concentrations of MoS₂ additives or prolonged treatment times, which often lead to particle agglomeration and high energy consumption. Even at lower concentrations, the friction coefficient remains high, and systematic studies on the influence of key process parameters, such as applied voltage are still lacking. Therefore, this study aims to systematically investigate the effects of different PEO voltages on the microstructure, chemical composition, and tribological properties of TiO₂/MoS₂ composite coatings under low MoS₂ concentration and short processing time, so as to provide theoretical and practical guidance for the design and fabrication of high-performance wear resistant and antifriction coatings.

In this study, Ti-6Al-4V alloy was employed as the substrate. TiO₂/MoS₂ composite coatings were fabricated in a single-step process via PEO with incorporation of MoS₂ nanoparticles. The applied voltage was varied at 400, 500 V, and 600 V. The influence of voltage on the coating surface morphology was characterized using scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM). Localized chemical analysis of different regions on the coating surface was performed by energy dispersive spectroscopy (EDS) attached to the SEM. Phase composition was further determined by X-ray diffraction (XRD). Finally, the tribological properties of the coatings were evaluated using a ball-on-disk friction and wear tester.

The test results demonstrate that as the PEO applied voltage increases, the pore size, coating thickness, surface roughness, and deposited MoS₂ content of the coatings all increase. Tribological tests on samples prepared at different voltages demonstrated that the coating produced at 500 V exhibited the lowest friction coefficient of approximately 0.2, representing a 69.2% reduction compared to the substrate, indicating excellent antifriction performance. In contrast, coatings prepared at 400 V and 600 V exbibited significantly higher friction coefficients of 0.75 and 0.82, respectively, and suffered from severe adhesive and abrasive wear. The primary reasons for this behavior are as follows: At the lower voltage (400 V), the coating thickness is thin and the MoS₂ content is insufficient to provide effective lubrication. During the running-in stage, the coating lacks adequate capacity to accommodate wear debris, leading to inadequate debris removal. This results in pronounced abrasive wear, rapid penetration of the coating, and direct interaction between the substrate and the counterface, thereby increasing the friction coefficient. At the higher voltage of 600 V, although the coating thickness and MoS₂ content increase substantially, the surface roughness rises significantly ((4.7 ± 0.3) μm). This leads to the generation of large, coarse debris during the initial running-in stage. Before the coating can effectively accommodate these debris particles, they cause rapid spallation of the coating, generating even more debris and accelerating wear. Under these conditions, the MoS₂ particles embedded in the outer layer fail to provide any meaningful lubrication, and the coating is quickly worn through, resulting in a sharp increase in the friction coefficient. At the applied voltage of 500 V, the coating exhibits moderate thickness and surface roughness, maintaining adequate coating thickness and MoS₂ content without excessive surface roughness. The friction and wear mechanism of the TiO₂/MoS₂ composite coating under this voltage can be elucidated as follows: The inherent porous outer layer of the PEO coating undergoes initial smoothing of surface asperities during friction, generating wear debris containing embedded MoS₂ particles that fill surface depressions and inherent pores. With continued sliding, the MoS₂ particles within the debris gradually spread across the contact interface. Owing to their unique two-dimensional layered structure, these particles undergo interlayer sliding under shear stress, forming a continuous surface film with excellent lubricating properties. Furthermore, the porous structure of the coating not only accommodates wear debris but also functions as a reservoir for MoS₂ particles, enabling continuous replenishment of lubricant to areas where the surface lubricating film becomes locally depleted, thereby achieving remarkable self-lubricating performance.

At the optimized voltage of 500 V, the TiO₂/MoS₂ composite coating exhibits a moderate thickness ((28.0 ± 0.6) μm) and surface roughness ((3.0 ± 0.2) μm), along with a relatively high MoS₂ content. This combination results in the lowest friction coefficient of 0.2, representing a 69.2% reduction compared to the uncoated Ti-6Al-4V substrate; During the friction process, MoS₂ particles embedded in the TiO₂/MoS₂ composite coating are progressively exposed under shear stress and undergo interlayer sliding. This leads to the formation of a lubricating film on the wear track, which provides effective self-lubrication and significantly enhances the tribological performance of the Ti-6Al-4V alloy.