Search Results (631)

Titanium alloys are widely used in clinical settings due to their excellent mechanical properties and biocompatibility. However, the biologically inert surface of titanium alloys limits interfacial bioactivity and bone integration, which may compromise long-term implant stability. Therefore, this study innovatively proposes a synergistic “composition design and process adaptation” strategy. Specifically, borosilicate bioactive glasses (BSBGs) with a high B₂O₃ content (36 mol%), co-doped with strontium (Sr) and magnesium (Mg), were designed and systematically compared with Sr/Mg-doped silicate bioactive glasses (SBGs). Both glasses were subsequently deposited onto Ti6Al4V substrates using atmospheric plasma spraying. The results showed that the BSBG coating exhibited an initial boron release concentration of up to 116 mg/L but exhibited excellent cytocompatibility, which is likely related to the synergistic regulation of Sr, Mg, and B ions. Moreover, the BSBG coating induced Ca-P compound mineralization within 24 h, significantly faster than the SBG coating, which required a minimum of 3 days, confirming superior biomineralization kinetics. Both coatings achieved a bonding strength of 30 MPa, meeting clinical requirements. In vivo experiments confirmed that the BSBG coating significantly promoted new bone regeneration and implant osseointegration. This work not only delivers experimental validation supporting the implementation of high-boron-content bioactive glass coatings but also provides a practical method for designing rapidly degradable and highly bioactive coatings to facilitate improved osseointegration. Full article

Leaf-color mutants are crucial for elucidating chlorophyll metabolism mechanisms. Here, we identified yel, a stably inherited rice mutant with a dwarf and yellow-green leaf phenotype controlled by a single recessive nuclear gene. Using BSA-seq, we mapped the candidate causal gene to OsMPEC, encoding a magnesium protoporphyrin IX monomethyl ester cyclase with a G→T substitution. Multi-omics analysis revealed that the functional deficiency of OsMPEC protein—despite unchanged transcript levels—triggers global transcriptional repression of the chlorophyll metabolic network. This defect caused distinct metabolic consequences: impaired synthesis at the early stage (yel1) and toxic metabolite accumulation at the later stage (yel2). Furthermore, metabolic collapse induced systemic reprogramming of hormone signaling, shifting from pro-growth to stress and senescence modes. We propose that the yel phenotype is associated with a self-reinforcing inhibitory loop of “passive synthesis inhibition” and “active degradation acceleration.” This study clarifies OsMPEC’s role in chlorophyll homeostasis and demonstrates how a single genetic defect drives phenotype- through to network-level cascading effects. Full article

Biodegradable Mg–Ca–Sr alloys are promising candidates for temporary implant applications, but their degradation behavior is strongly influenced by alloy composition and electrolyte chemistry. This comparative short-term study investigated how increasing the Sr content from 0.5 to 1.5 wt.% influences the electrochemical response and surface characteristics of cast Mg–0.5Ca–xSr alloys in 0.9% NaCl and calcium- and magnesium-free Dulbecco’s phosphate-buffered saline (DPBS). Potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy, quantitative image analysis, and energy-dispersive X-ray spectroscopy were used. Increasing the Sr content reduced the corrosion-current density from 0.0110 to 0.0039 mA/cm² in NaCl and from 0.297 to 0.169 mA/cm² in DPBS, while the corresponding calculated corrosion rates decreased from 2.51 to 0.886 mm/year and from 6.66 to 3.79 mm/year, respectively. Replicated EIS measurements of both alloys showed that Mg–0.5Ca–1.5Sr exhibited higher charge-transfer resistance than Mg–0.5Ca–0.5Sr in both NaCl (253 ± 15 versus 184 ± 14 Ω·cm²) and DPBS (853 ± 48 versus 615 ± 42 Ω·cm²). NaCl-exposed surfaces showed more porous and discontinuous deposits and a greater number of visible pit-like defects, whereas DPBS produced comparatively continuous P-containing deposits. Overall, increasing the Sr content to 1.5 wt.% was associated with lower polarization-derived global corrosion kinetics and a more resistive interfacial response, whereas electrolyte composition strongly influenced both interfacial impedance and surface-deposit morphology. These findings represent comparative short-term electrochemical and surface-characterization data obtained at 23 ± 1 °C and should not be interpreted as measures of long-term physiological degradation or in vivo performance. Full article

Aiming at the rapid corrosion of degradable magnesium alloys in physiological environments and the insufficient long-term protection of single plasma electrolytic oxidation (PEO) coatings, Mg-Mn-Fe layered double hydroxide (LDH) and baicalin (BA)-loaded LDH/BA composite coatings were prepared in situ on PEO-pretreated ZE21C magnesium alloy substrates. BA was stably anchored on the LDH surface via coordination bonds between its oxygen-containing functional groups and laminate metal sites. Benefiting from the physical barrier of the LDH lamellar structure and the corrosion inhibition effect of baicalin, the LDH/BA coating significantly improved the corrosion resistance of the magnesium alloy matrix. The composite coating exhibited peroxidase-like catalytic activity for reactive oxygen species generation, which could be enhanced by near-infrared irradiation. It also possessed stable photothermal conversion performance and pH-responsive drug release behavior under acidic conditions. Biological characterization demonstrated that BA-loaded LDH composite coatings exert potent inhibitory effects on 143B cell proliferation. This work integrates long-term corrosion resistance, controlled drug release, and photoresponsive catalytic functions onto magnesium alloy surfaces, providing an effective strategy for developing high-performance biodegradable magnesium alloys. Full article

In this study, graphite particles and short-cut carbon fibers were used to prepare a hybrid-reinforced composite with AZ91 magnesium alloy as the matrix via the powder metallurgy process. The effects of different added phase ratios on microstructure, density, compressive strength, and fracture morphology were investigated. The results show that the addition of 5% graphite particles alone reduced the compressive strength by 20.1% compared to pure magnesium, attributed to interfacial delamination and interlaminar peeling in the graphite’s layered structure. The introduction of carbon fibers effectively compensates for this degradation. When the carbon fiber content was increased to 10% (with graphite fixed at 5%), the compressive strength reached a peak of 375 MPa—a 63.0% increase over the graphite-only system—and the fracture strain rose to 16.98%. However, an excessive amount of carbon fibers (15%) led to agglomeration, causing the porosity to rise to 9.1% and resulting in a significant decline in mechanical properties. Microstructural analysis indicates that carbon fibers exert a reinforcing effect by sharing the load and constraining the lateral deformation of the matrix, while graphite particles induce microcracks and pores, resulting in a weakening effect; under appropriate ratios, the two can achieve synergistic reinforcement. This study provides experimental evidence for the component design and performance control of high-strength, rapidly dissolving magnesium-based composites. Full article

Bioresorbable stents (BRS) have been explored in cardiovascular intervention to provide temporary mechanical support while reducing long-term foreign material. The coronary experience has shown both the potential and the limitations of this strategy. First-generation polymeric stents demonstrated feasibility but were limited by thick struts, insufficient radial strength, delayed healing, and increased scaffold thrombosis. In contrast, metallic bioresorbable platforms improved mechanical performance, but each material system still faces trade-offs between strength, degradation rate, and biological response. Transcatheter pulmonary valve replacement (TPVR) may represent a clinically meaningful setting for renewed BRS development. Patients with congenital heart disease often require repeated pulmonary valve interventions over a lifetime, and permanent metallic frames may increase cumulative implant burden and complicate future treatment. However, TPVR imposes distinct requirements, including large-diameter expansion, stable anchoring, fatigue resistance, controlled degradation, and leaflet-frame integration. This review summarizes the lessons learned from coronary BRS, discusses material considerations for TPVR-oriented stent design, and evaluates current preclinical evidence for bioresorbable and regenerative pulmonary valve platforms. Particular attention is given to magnesium–zinc alloys as a tunable material strategy for future bioresorbable TPVR frames. Although direct evidence for fully bioresorbable metallic TPVR devices remains limited, this approach provides a rational framework for next-generation pulmonary valve intervention. Full article

Magnesium alloys are promising candidates for biomedical implants, but their rapid corrosion limits clinical use. Simulated body fluid (SBF) is commonly used to evaluate corrosion behaviour; however, Ca-P and carbonate deposits can mask the intrinsic performance of protective coatings. Tris(hydroxymethyl)aminomethane (Tris) has been proposed as an SBF modifier, although its effect on coated magnesium remains poorly understood. While Tris modifies the buffering characteristics of the solution, it also alters the stability of Mg(OH)₂ and the precipitation equilibria of corrosion products, resulting in more aggressive corrosion conditions than standard SBF. Here, the corrosion behaviour of AZ31 alloy, a plasma electrolytic oxidation (PEO) coating, and a sol-gel sealed PEO coating was investigated in SBF with and without Tris. Electrochemical impedance spectroscopy, immersion tests, pH monitoring, and post-immersion SEM/EDS analyses were used to evaluate coating performance under physiological and aggressive conditions. The results show that AZ31 and PEO coatings exhibit higher apparent corrosion resistance in SBF without Tris due to corrosion-product stabilization and Ca-P-rich deposits that partially block electrolyte access. In contrast, SBF with Tris accelerates degradation, causing uniform corrosion of AZ31 and premature PEO failure through electrolyte penetration and coating cracking. The PEO-AR/ZTP system maintains the highest electrochemical resistance and the best protective performance in both media. Full article

In this study, zinc-doped magnesium ferrite (Zn_x-Mg_1−xFe₂O₄) nanoparticles were synthesized using a facile combustion method and investigated for their electrochemical sensing and photocatalytic applications. The structural, morphological, and optical properties of the synthesized nanoparticles were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDAX), Fourier-transform infrared spectroscopy (FTIR), Energy band gap (Eg) and UV-Vis spectroscopy. The synthesized Zn–MgFe₂O₄ nanoparticles exhibited crystallite sizes ranging from 18.7 to 27.9 nm with an optical band gap of 1.86–1.89 eV. The catalyst achieved degradation efficiencies of 78% for Eriochrome Black T and 85% for Methyl Orange within 120 min, while the electrochemical sensor exhibited excellent linearity toward HgCl₂ detection (R² = 0.99664), demonstrating the multifunctional capability of the synthesized nanostructure. The synergistic effects of Zn doping contributed to enhanced electrical conductivity, catalytic activity, and structural stability. The novelty of this work lies in the development of combustion-synthesized Zn–MgFe₂O₄ nanoparticles as a multifunctional material capable of simultaneously achieving efficient photocatalytic degradation of organic dyes and sensitive electrochemical detection of mercury chloride using a simple and scalable synthesis route. These findings demonstrate that Zn–MgFe₂O₄ nanoparticles hold significant potential for integrated environmental remediation and electrochemical sensing applications. Full article

Magnesium alloys are used or considered for lightweight structures and biodegradable implants, but high electrochemical activity, limited wear resistance, and localized corrosion still limit their service reliability. Plasma electrolytic oxidation (PEO), also called micro-arc oxidation (MAO), forms an adherent ceramic scaffold. Discharge channels, interconnected pores, thermal cracks, and a mechanically weak outer layer mean that the as-formed coating is rarely a complete protective system. This review examines advanced PEO/MAO-based composite coatings through a process–structure–function lens and develops an application-oriented design framework. The discussion covers PEO/MAO process-window control, electrolyte and particle engineering, sol–gel and polymer sealing, layered double hydroxide/inhibitor systems, self-healing reservoirs, superhydrophobic and slippery interfaces, Ca-P/hydroxyapatite and polymer biofunctionalization, and duplex coatings for wear, electrical, and thermal functions. Emphasis is placed on how these modules regulate defect connectivity, mass transport, interfacial stability, damage response, tribocorrosion, and biodegradation, as well as on the evidence needed to support each claimed function. The analysis indicates that coating performance is governed not by multilayer complexity alone, but by the compatibility among the ceramic scaffold, functional module, dominant failure mode, and service-specific validation protocol. Chloride-exposed structures require durable pore sealing and active inhibition; wear-critical components require coupled corrosion–wear assessment; and biodegradable implants require a degradation window that balances corrosion moderation, cytocompatibility, biofunctionality, and residual mechanical integrity. Remaining challenges include interfacial durability, finite inhibitor reservoirs, wetting-state instability, process reproducibility, scale-up, and life-cycle impacts. The proposed process maps and validation criteria are intended to support modular, testable, and application-specific PEO/MAO surface systems for magnesium alloys. Full article

Aluminum/magnesium (Al/Mg) hybrid structures are promising candidates for lightweight engineering, but reliable joining is still limited by brittle intermetallic compounds (IMCs), oxide films, pores, cracks, and corrosion-related degradation. This review summarizes recent advances in Al/Mg dissimilar-metal joining, including solid-state welding, fusion welding, brazing, resistance-based joining, and mechanical joining. Emphasis is placed on process characteristics, interfacial reactions, defect formation, mechanical properties, service reliability, and simulation-assisted process understanding. The reviewed studies indicate that joint reliability cannot be interpreted solely from IMC thickness; phase type, continuity, spatial distribution, interfacial morphology, and involvement in the fracture path are also critical. Solid-state and high-speed impact processes can restrict continuous Al–Mg reaction layers by reducing thermal exposure and promoting plastic contact, whereas fusion-based processes provide greater manufacturing flexibility but require stricter control of molten-pool behavior, Mg evaporation, porosity, and interlayer stability. Recent numerical simulations and data-driven studies are further discussed as tools for mechanism-guided parameter design. This review provides an integrated comparison of joining routes and highlights future needs for standardized testing, fatigue and corrosion evaluation, thermal-cycling assessment, coupled service-performance analysis, and process selection for engineering applications. Full article

Alkali-activated materials (AAMs) are widely regarded as promising alternatives to ordinary Portland cement for marine engineering because of their low carbon footprint, efficient utilization of industrial by-products, and potentially favorable mechanical and durability performance. However, their long-term application in marine environments remains challenging, as the original advantages of AAMs can be progressively weakened by the individual and coupled actions of aggressive seawater ions, particularly chloride (Cl⁻), sulfate (SO₄²⁻), and magnesium (Mg²⁺). These ions affect AAMs through distinct but interconnected mechanisms, including chloride binding and transport, competitive ion interactions, phase transformation, destabilization of reaction products, pore-structure evolution, and the subsequent degradation of macroscopic properties. Meanwhile, the response of AAMs to marine exposure is highly system-dependent, since precursor chemistry, activator design, reaction-product assemblage, and pore structure strongly govern their resistance to ion attack. In recent years, considerable efforts have been devoted to improving the marine durability of AAMs through composition and phase design, pore-structure refinement, and transport control. Nevertheless, current understanding remains fragmented, particularly regarding the coupled effects of multiple seawater ions and the links between microstructural evolution and long-term performance. The primary purpose of this review is to provide a systematic overview of the marine durability of AAMs from the perspectives of multi-ion threats, material-dependent responses, and existing mitigation strategies. Particular emphasis is placed on the roles of Cl⁻, SO₄²⁻, and Mg²⁺, the controlling effects of precursor and activator chemistry, and the translation of micro-mechanisms into macroscopic durability evolution. By integrating these aspects within a unified framework, this review aims to support the design and application of AAMs for reliable long-term use in coastal and offshore engineering. Future research should prioritize standardized multi-ion exposure protocols, coupled transport–reaction models, long-term field validation, and durability assessment of reinforced AAM concretes under realistic marine conditions. Full article

To reveal the influence of pulsed current density on the microstructural evolution and mechanical properties of Mg-Gd-Y-Zn-Zr rare-earth magnesium alloy wires, extruded Mg-10Gd-3.4Y-1.3Zn-0.4Zr alloy wire was selected as the research material. By regulating the current density in the range of 12–20 A/mm², the effects on temperature rise behavior, microstructural evolution, and mechanical properties were systematically investigated. The results show that as the current density increases from 12 A/mm² to 20 A/mm², the measured surface peak temperature rises from 207 °C to 497 °C, and the mechanical properties among the electropulsing-treated samples exhibit a trend of first increasing and then decreasing. Among these treated samples, the optimal combination of strength and ductility is achieved at a current density of 15 A/mm², at which the tensile strength and elongation reach 312.2 MPa and 13.6%, respectively. Microstructural analysis indicates that appropriate pulsed electrical parameters promote the dissolution, fragmentation, and homogenized dispersion of block-shaped long-period stacking ordered (LPSO) phases, thereby optimizing the internal strain state and facilitating the activation of non-basal <c+a> slip. However, when the current density increases to 20 A/mm², excessive thermal input leads to grain coarsening and a network-like W-phase precipitation, indicating that excessive energy input can lead to microstructural instability and mechanical degradation. Full article

Freshwater scarcity is driving the construction industry to seek alternative mixing waters, and seawater is an abundant resource; however, its suitability is commonly judged by total salinity, which overlooks the fact that coastal seawater chemistry varies hugely between locations and may govern long-term strength performance in varying locations. To address this problem, this study investigates the long-term strength performance and its microstructural and phase transformation of cement mortars mixed with seawater, with the aim of establishing a technical understanding between region-specific seawater chemistry and mortar strength. Seawater was collected from four coastal locations in Tamil Nadu, India, and characterized for chloride, sulfate, magnesium, organic solids, and related parameters. The cement mortar cubes were cast with each seawater, and compressive strength was measured from 3 to 360 days; the microstructural and phase changes underlying the strength behavior were examined at 360 days using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). All samples showed accelerated early-age strength gain from the catalytic effect of chloride and sulfate ions, followed by strength loss at later ages caused by the same ionic environment, with a critical strength loss between 28 and 56 days. The Chennai sample, with the highest chloride and sulfate concentrations, suffered the most severe degradation of 11.5% loss of peak strength, which is attributed to ettringite and gypsum formation together with magnesium attack that consumed Portlandite to form non-cementitious brucite and secondary Calcite. In contrast, the Rameshwaram sample, with exceptionally low sulfate, exhibited superior stability with 3.5% loss, while Puducherry and Tuticorin showed intermediate degradation of 3.9% and 7.8% respectively, with the Puducherry sample further compromised by high organic solids. The results identify the chloride to sulfate ratio, rather than total salinity, as the key predictor of long-term strength performance. The main takeaway for the cement industry is that the suitability of seawater as mixing water is highly site-specific, and a detailed chemical analysis quantifying sulfate and magnesium content is an indispensable prerequisite for strength assessment and material selection before seawater is adopted in marine and coastal construction. Full article

The development of sustainable flame-retardant polymer composites is important for expanding the practical use of bio-based plastics while reducing reliance on petroleum-derived and halogenated materials. In this work, biodegradable polylactic acid (PLA) composites were prepared using raw wood-derived biochar as a degradable carbon-based filler and magnesium hydroxide (MH) as a halogen-free flame-retardant additive. PLA/Biochar/MH composites were prepared by melt compounding and compression molding, followed by systematic evaluation of their structural, thermal, flame-retardant, mechanical, and stability-related properties. The flame-retardant performance, evaluated by limiting oxygen index (LOI) and UL-94 (UL: Underwriters Laboratories) vertical burning tests, was significantly enhanced by the combined biochar/MH system. Biochar alone slightly increased the LOI of PLA, while MH-containing composites exceeded the practical 21% LOI threshold, with PLA/Biochar20/MH20 achieving the highest LOI value of 26.2%. This improvement was attributed to char formation, heat absorption, gas dilution, and magnesium oxide-supported barrier formation. The composites also maintained reasonable dimensional stability after accelerated aging with thickness changes below 1%. Overall, this study demonstrates that combining biodegradable PLA with degradable biochar and halogen-free MH provides a promising sustainable strategy for developing flame-retardant PLA-based composites with improved residue formation and dimensional stability. Full article

Plasma electrolytic oxidation (PEO) has emerged as a leading surface engineering technology for improving the tribological and corrosion performance of lightweight structural alloys, including aluminum, magnesium, titanium, and zirconium. Unlike conventional anodizing or line-of-sight deposition processes, PEO forms thick, multiphase ceramic oxide coatings metallurgically bonded to the substrate through plasma-assisted in situ oxidation, enabling treatment of complex and internal geometries that competing technologies cannot reach. The tribological performance of PEO coatings is governed by coupled interactions among electrolyte chemistry, electrical discharge behavior, phase evolution, porosity development, and residual stress state. This review critically evaluates the friction, wear, and tribo-corrosion behavior of PEO coatings under dry sliding, lubricated, high-temperature, marine, and vacuum environments, and systematically examines the influence of processing parameters, microstructural evolution, transfer layer formation, and counterface interactions on coating performance. Hybrid and duplex systems incorporating solid lubricants, polymer impregnation, sol–gel sealing, and multilayer architectures are discussed as strategies to overcome limitations associated with brittleness and surface porosity. Current research challenges, including fatigue degradation, coating defect control, limited cross-study standardization, and incomplete mechanistic understanding of process–microstructure, tribological relationships, are critically assessed. Emerging directions encompassing self-lubricating adaptive coatings, AI-guided process optimization, and multifunctional hybrid architectures are highlighted as pathways toward next-generation surface systems. This review provides a mechanism-based framework for understanding tribological behavior in PEO coatings and identifies critical opportunities for future industrial implementation in aerospace, automotive, marine, biomedical, and energy applications. Full article