Search Results (25,644)

Four-dimensional (4D) printing integrates additive manufacturing with stimuli-responsive materials to fabricate biomedical implants and functional healthcare devices that undergo programmed, time-dependent changes in shape or function. Unlike static 3D-printed constructs, 4D-printed systems can respond to clinically relevant stimuli such as temperature, hydration, pH, light (including near-infrared), magnetic fields, or electrical inputs. These triggers drive defined actuation mechanisms, most commonly thermomechanical shape-memory recovery, swelling-induced morphing, and magnetothermal activation. This review synthesizes the principal material platforms used for biomedical 4D printing, including shape-memory polymers and alloys, hydrogels, liquid-crystal elastomers, and responsive composites, and links material choice to device behavior and translational feasibility. Applications are discussed across self-expanding stents, cardiac occluders, tissue-engineered constructs, implantable drug delivery systems, and adaptive wearables. Key translational challenges include sterilization compatibility, manufacturing reproducibility and quality control, safe stimulus delivery, predictable biodegradation and long-term biocompatibility, and regulatory pathway definition. Full article

Titanium and its alloys are used in dental and orthopedic implants. However, long-term stability remains a clinical challenge. To overcome this limitation, surface modification has been investigated to improve surface properties. Our previous study demonstrated that the immobilization of secretory leukocyte protease inhibitor (SLPI) on the titanium surface promotes osteoblast adhesion, proliferation, and differentiation in vitro. The current study demonstrated the first in vivo evaluation of SLPI as a bioactive coating for medical implants. Grade 5 titanium screws were coated with 10 µg/mL of recombinant human SLPI (rhSLPI) for 24 h via simple physical adsorption, and the results were preliminarily validated via FE-SEM and ELISA. These SLPI-coated titanium screws (TiSs) were then placed in the tibia of Sprague–Dawley rats for 4 and 8 weeks. The hematological and biochemical parameters (BUN, Creatinine, AST, and Troponin I) demonstrated no acute systemic alterations within the 8-week period across all groups. Moreover, micro-computed tomography (micro-CT) and histological analysis revealed significantly higher bone volume fraction (%BV/TV) at 4 weeks compared to uncoated controls (20.64% 2.452% vs. 11.73% 0.524%). Finally, the biomechanical stability of implants, assessed using the removal torque test, showed that TiSs showed higher strength compared to Ti at both 4 and 8 weeks. In conclusion, this study represents a novel approach to transitioning rhSLPI-coated titanium evaluation from in vitro models to an in vivo rat model. rhSLPI surface functionalization enhances early-stage osseointegration and improves implant mechanical stability without acute hematological and biochemical alterations. These proof-of-concept findings suggest the potential of SLPI as a bioactive coating strategy. Full article

The present work investigated the thermodynamic behaviors of oxygen in a liquid Fe–Ti alloy over a wide Ti concentration range of 11.6–71.2 wt% at 1873 K by integrating equilibrium experiments with thermodynamic modeling. To prevent excessive oxidation during the equilibrium experiments, the liquid alloys were equilibrated in a purified Ar atmosphere with an oxygen partial pressure below ~10⁻²⁰ atm. Two quenching methods—furnace quenching with He gas injection and water quenching via quartz tube suction—were employed to evaluate the effect of cooling rate on total oxygen measurements. While He gas quenching led to higher measured oxygen contents owing to the formation of secondary Ti oxides, the quartz tube suction quenching method consistently yielded significantly lower oxygen values. The dissolved oxygen content increased with increasing Ti content. Electron probe microanalysis identified TiO as a stable equilibrium oxide phase above 11.6 wt% Ti, which was characterized as a face-centered cubic (FCC) rock-salt structure via electron backscatter diffraction analysis. Based on these results, a thermodynamic assessment of oxygen behavior in a liquid Fe–Ti alloy in equilibrium with TiO was performed for the first time using a modified quasichemical model. Consequently, the present model successfully reproduced the Ti–O relationship in the liquid Fe–Ti alloy across both the high-Ti concentration region saturated with TiO and the low-Ti concentration region saturated with Ti₂O₃ and Ti₃O₅. Full article

Conventional titanium alloy production based on the Kroll process features high energy consumption and long procedures, making low-cost, short-process fabrication a research focus in titanium metallurgy. In this work, low-interstitial γ-TiAl alloys were prepared via a coupled self-propagating high-temperature synthesis (SHS)–slag washing refining–vacuum arc remelting (VAR) process using TiO₂ as the raw material. Slag washing refining was performed at 1750 °C with 150 g of CaO-Al₂O₃-SiO₂-CaF₂ mold flux and 1.5 wt.% Ca, followed by VAR under a vacuum of 10⁻²–10⁻³ Pa. γ-TiAl alloy with a composition of Ti 66.01 ± 0.5 wt.%, Al 33.8 ± 0.5 wt.%, O 0.054 ± 0.002 wt.%, N 0.046 ± 0.005 wt.%, and C 0.085 ± 0.008 wt.% was obtained, and the inclusion size was refined to 0–3 μm. This coupled approach provides a scalable, low-cost route for the industrial preparation of low-interstitial γ-TiAl alloys. Full article

TC4DT (ELI) is a damage-tolerant titanium alloy characterized by high fracture toughness and slow crack propagation rates, and is, therefore, considered one of the standard materials for model fasteners in modern equipment. However, its high yield strength leads to excessive tool wear and forming defects. This paper presents a complete FE simulation framework to investigate the thread-rolling process of TC4DT(ELI) bolts M16 × 1.5. Using the actual geometries of the workpiece and rollers, an elasto-plastic three-dimensional finite element model was built in ABAQUS/Explicit to perform verification simulations, with the theoretical blank diameter and forming force as the reference benchmarks. The simulation results agreed well with the actual industrial data. This study carried out single-factor analyses of the effect of three important process parameters—the roll speed, friction coefficient, and initial temperature—on the resulting stress–strain distribution, forming force, and thread formation depth. A modal analysis was performed in ANSYS Workbench to check the structural integrity and avoid resonance while operating. According to the results, the optimized parameters decreased the maximum forming force by 14.8% and improved thread filling. Compared with experimental data, the simulation error in the blank diameter was controlled within 1.2%. The present work, a reliable numerical underpinning for replacing expensive and time-consuming trial-and-error processes, forms a basis for high-performance titanium alloy fasteners and assists in the wider application of such fasteners in modern equipment and any advanced manufacturing industries. Full article

Pin–bushing bearings in heavy-duty construction machinery operating in severe industrial environments are susceptible to accelerated wear, grease degradation, and lubrication failure, yet application-specific guidance for lubricant selection and re-greasing intervals under such conditions remains limited. This study evaluates the combined effects of bushing material (hardened steel, cast bronze, and Cu–Sn alloy), grease type (three commercially used greases with viscosities of 120, 460, and 150 mm²/s at 40 °C), and lubrication interval (8, 12, and 24 h) on grease-condition indicators in a field-operating wheel loader used in slag handling, where surrounding slag temperatures may reach 700–800 °C. A Taguchi L9 orthogonal array was used to define nine experimental configurations, each applied for approximately one week under real operating conditions. Grease samples were characterised using the SKF grease analysis kit based on NLGI consistency grade, base oil release rate, and contamination particle count. All greases showed an increase in NLGI grade from 2 to 3–4 during service, indicating thickening and a possible risk of lubrication channel blockage. Oil release rates decreased by up to 60% in some configurations, indicating reduced base oil mobility during service. When the three grease-condition indicators were evaluated together by Grey Relational Analysis, the combination of steel bushing, type B grease (ISO VG 460, lithium complex with MoS₂), and a 12 h lubrication interval showed the most balanced overall response. These findings provide field-based guidance for grease selection and maintenance scheduling in pin–bushing systems operating under demanding service conditions. Full article

Magnesium alloys exhibit promising application prospects in medical orthopedic implants. However, their practical applications are limited by rapid corrosion, suboptimal osseointegration, and implant-related infections. Although conventional drug-eluting polymer coatings can provide various biological functions, the uncontrolled drug release often compromises long-term therapeutic efficacy. In this study, a self-healing Mg-poly(ε-caprolactone) (PCL)@OHF coating is designed and prepared on WE43 Mg by spin coating to achieve ultrasound-triggered release of osthole. OHF consists of osthole-loaded hollow mesoporous silica nanoparticles (HMSs) modified with Pluronic F127. Drug release studies show that the nanocapsules respond to ultrasound stimulation, with the cumulative release increasing from 39.94% to 75.93% after 7 days. Furthermore, the coating demonstrates intrinsic self-healing capacity upon thermal treatment at 50 °C. Electrochemical and immersion tests reveal that the composite coating provides good barrier protection for the WE43 Mg alloy, evidenced by a decrease in corrosion current density from 2.04 × 10⁻⁶ to 5.94 × 10⁻⁷ A/cm². In vitro biological assays confirm the antibacterial efficacy against Staphylococcus aureus and Escherichia coli, as well as the ability to promote osteogenic differentiation. The results reveal a surface modification strategy that combines self-healing, anticorrosion, and on-demand drug release, offering a promising approach for advanced orthopedic implants. Full article

The article discusses the methods for classifying processes for testing and processing metals by plastic deformation, based on the characteristics of their stress–strain state. The basic methods for determining the stress and strain states using fundamental scalar quantities representing the stress and strain tensors are discussed. Equations have been derived for the quantitative determination of the type of stress–strain state through a combination of principal stresses, represented as the strain rigidity of the deformation mode. A deformable work-hardening alloy, AA7075, from the database Quantor Form 8.2.4 software product, is used, which is deformed at room temperature with an analysis of elastic–plastic deformations. A classification of deformation processes for testing and processing metals by plastic deformation is proposed, using the stress triaxiality parameter and the strain rigidity coefficient. Some 2D and 3D diagrams have been created based on simulation modeling of plastic deformation processes using virtual tools, allowing the grouping of processes according to the measured principal stresses and their combinations, which represent the stress triaxiality and strain rigidity of the deformation mode. By determining the type of grouping in these diagrams and the change in the stress–strain state with increasing strain levels, the characteristic features of the deformation processes used in materials testing and in the processing metals by plastic deformation of metals/alloys have been confirmed. Full article

Titanium and its alloys are widely used for orthopedic implants, but their intrinsic bioinertness may hinder osseointegration. In this study, titanium dioxide nanotube (TNT) arrays were fabricated on Ti-6Al-4V scaffolds via anodization, and their effects on the adhesion behavior of human bone marrow mesenchymal stem cells (hBMSCs) were investigated. Surface characterization showed that anodization successfully generated ordered TNT layers, increased surface roughness, enhanced protein adsorption, and induced an apparent superhydrophilic wetting response. Compared to the untreated scaffold and TNT50, the small-diameter TNT10 surface significantly promoted hBMSC adhesion and proliferation. Microscope imaging further revealed enhanced cell spreading, F-actin organization, and vinculin expression on TNT surfaces, with the most prominent focal adhesion-related staining observed in TNT10. Quantitative proteomic analysis showed that TNT10 was associated with coordinated remodeling of adhesion- and cytoskeleton-related molecular programs, including focal adhesion, cell–substrate junction, and regulation of the actin cytoskeleton. In contrast, TNT50, despite supporting obvious cytoskeletal remodeling, was more compatible with a dynamic, higher-turnover adhesion state. Overall, these findings suggest that small-diameter TNTs provide a more favorable interfacial microenvironment for stable early hBMSC adhesion on porous titanium scaffolds. Full article

Ice adhesion on exposed structures remains a major operational challenge, motivating the search for passive, material-based anti-icing strategies. Molecular dynamics offers a controlled way to investigate ice–surface interactions beyond the limits of experimental setups. In this work, we develop a simulation framework to model the impact of solid hexagonal ice droplets on metallic substrates. Ice impacts are simulated across a range of velocities (10–120 m/s), temperatures (120–250 K), and face-centred cubic surface materials (gold, copper, silver, aluminum, and nickel). Using LAMMPS, mW water force-field, EAM/Alloy metal potentials, and Lennard-Jones water–surface interactions, we quantify phase evolution through angular order parameter and quasi-liquid layer measurements, complemented by the CHILL+ algorithm in OVITO. By isolating all external factors, we show that melting increases with velocity and temperature and correlates with substrate properties: metals with high thermal diffusivity and low Young’s modulus tend to decrease post-collision ice melting. The ratio of the former to the latter, a derived index of merit Υ, significantly correlates with melting percentage and identifies silver as the most effective anti-ice material examined. Statistical analyses strongly suggest that these surface properties influence interfacial melting, supporting the use of this modelling framework for screening and designing anti-icing materials. Full article

X ray photoelectron spectroscopy (XPS) is a key technique routinely employed for the chemical analysis of alloy surfaces, enabling precise nanoscale characterization of near surface elemental composition and chemical states. This review outlines the fundamental principles of XPS, typical data analysis workflows, and critical analytical considerations specific to alloy systems. Given the propensity for oxidation, multicomponent nature, and heterogeneous phase characteristics of alloys, standardized protocols are reviewed for sample preparation, binding energy calibration, peak fitting, quantitative analysis, and depth profiling. For conductive alloys, calibration using the Fermi edge or gold reference standards is specified, and the use of Auger parameters is highlighted to improve the reliability of chemical state identification. This article also systematically summarizes applications of XPS in corrosion protection, high temperature oxidation, surface modification, phase transformation, and failure analysis. It is emphasized that near surface chemical information must be validated in combination with bulk phase, microstructural, and electrochemical characterization to rationally establish relationships between surface chemistry and macroscopic performance. Finally, recent advances in near ambient pressure, in situ, high resolution, and intelligent XPS techniques are reviewed, providing a standardized reference and technical support for alloy research. Full article

Surface topography characterization is essential for evaluating the effects of texturing processes and for describing surface-dependent phenomena. Assessing the relationships between manufacturing, surface geometries, and functional properties requires, firstly, a detailed characterization of surfaces. Conventional parameters defined in ISO 25178-2 describe the statistical distribution of surface heights relative to the mean plane, as well as the arrangement, spacing, and directionality of surface features. They also include height and spatial descriptors, functional properties derived from the Abbott–Firestone curve, and characteristics of individual topographic features, such as peaks and valleys, including their shape, volume, and distribution. While these parameters provide a valuable description of the surface, they are not intrinsically multiscale and provide only a single aggregated descriptor of the surface. Therefore, multiscale parameters complement this description by capturing relative areas and area-scale fractal-like complexity across geometrically decomposed surface features over a range of scales from the nano and micro to the macro scale. The main objective of this study is to evaluate correlations between conventional and multiscale topographic parameters, based on surfaces produced by electrical discharge machining (EDM). The novelty of this study lies in the integrated analysis of correlations between conventional and multiscale parameters, enabling a more comprehensive framework for surface characterization. Full article

This study presents a comparison between the results of process parameter optimization for the deep drawing of an AA5754-O automotive fuel tank, which utilizes two different objective functions. The first objective function is the maximum thinning percentage (max. %Thinning) of the formed part, which is a conventional formability index. The second is Q-value, a metric derived from the Thinning Limit Diagram that accounts for both necking-prone (excessive thinning) and wrinkling-prone (thickening) regions. The experiments were conducted using finite element simulation to model the forming behavior under an inscribed central composite design within the response surface methodology. Three process parameters, which are well known to be important for controlling material flow and achieving a balance between wrinkling and excessive thinning in deep drawing, were varied: blank holder pressure, the height of the male drawbead, and the radius of the female drawbead. Refined second-order response surface models were developed for both objective functions. Optimization based on the response surface models showed that, for the max. %Thinning objective function, the final part exhibited 19.46% maximum thinning but suffered from substantially higher wrinkling, as indicated by a maximum thickening of 36.39%. In contrast, the Q-value-based optimization resulted in a more balanced formability condition, with maximum thinning of 21.74% and maximum thickening of 13.17%. Moreover, the normalized density of elements in the safe zone of the Thinning Limit Diagram was higher, indicating an improvement in formability robustness. Therefore, this study highlights the limitations of conventional thinning-based optimization and demonstrates the potential of the Q-value as an extended practical quantitative formability tool that can simultaneously address necking and wrinkling in sheet metal forming, as presented through the studied automotive fuel tank on behalf of complex components. Full article

This study addresses the issue of insufficient product purity caused by the co-deposition of three major impurity ions—zinc, nickel, and lead—during the electrodeposition process of high-purity manganese. A targeted deep purification method for manganese sulfate electrolyte was developed using dithiocarbamate chelating agents (sodium dimethyldithiocarbamate, SDD). By optimizing key process parameters such as precipitant concentration, reaction temperature, reaction time, and solution pH, combined with density functional theory (DFT) calculations, to elucidate the selective impurity removal mechanism at the molecular level, a novel process for the efficient synergistic removal of Zn²⁺, Ni²⁺, and Pb²⁺ was established. The results showed that under the conditions of precipitant concentration of 1 g/L, solution pH of 6.5, reaction temperature of 55 °C, and reaction time of 2 h, the residual concentrations of Zn, Ni, and Pb in the electrolyte were all below 0.2 mg/L. DFT calculations revealed that SDD coordinates with metal ions through four sulfur atoms, and the absolute values of binding energies follow the order Ni²⁺ > Pb²⁺ > Zn²⁺ > Mn²⁺, indicating thermodynamically preferential capture of impurity ions. After purification, the manganese metal obtained by electrodeposition from the manganese sulfate solution achieved a purity exceeding 99.999%, with Zn, Ni, and Pb contents of 0.11 mg/kg, 0.038 mg/kg, and 0.05 mg/kg, respectively, meeting the raw material requirements for semiconductor-grade copper–manganese alloy targets. Full article

With changes in the global energy structure, ammonia has emerged as a favorable hydrogen storage medium due to its excellent properties. This work details the synthesis of a barium-doped cobalt–iron alloy catalyst via subsequent heat treatment. This alloy efficiently catalyzes the decomposition of ammonia into hydrogen. The results showed that using characterization methods such as TEM and XRD indicated that adding Ba to this system could regulate the microstructure of the Co-Fe alloy. After calcination, the barium promoted a reduction in the particle size of Co-Fe nanoparticles, enabling their uniform dispersion on the surface and a more uniform dispersion and improving the accessibility of the exposed surface. The optimized catalyst (0.05Ba-0.25CoFe/CeO₂) achieved an ammonia conversion of 93.2% at 550 °C under a gas hourly space velocity of 30,000 mL·g_cat⁻¹·h⁻¹. Mechanistic analysis based on XPS and CO₂-TPD results indicated that the barium optimized the electronic structure and alkaline sites of Co-Fe, promoted the desorption of nitrogen, and thereby accelerated the reaction kinetics of ammonia decomposition. This research provides a strategic method and theoretical basis for designing high-performance non-precious metal catalysts for ammonia decomposition. Full article