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Corrosion is a multibillion-dollar material degradation issue that affects process industries, transport infrastructure, as well as construction and building activities all over the world [...].
Implantation of titanium alloys (Ti-6Al-4V) or cobalt-chromium-molybdenum alloys (Co-Cr-Mo) for long-segment spinal fixation is the standard surgical treatment for adolescent idiopathic scoliosis (AIS), but long-term presence of the implants in the body may lead to the release of metal nanoparticles. Unlike orthopaedic internal fixation surgeries, spinal implants generally remain in the human body for a lifetime. The release of metal nanoparticles remains a potential clinical issue, but currently there is a lack of strong data on the topic. This study aimed to fill this crucial knowledge gap by providing longitudinal evidence on the dynamics of metal ion release. This is the first step in determining safety characteristics and clinical thresholds. (1) Are serum Ti, Co, and Cr concentrations in patients with AIS after implantation elevated compared with in patients without implantation over a 4-year period? (2) Does surgical removal of implants lead to a reduction in systemic metal nanoparticle load? (3) Is there a correlation between metal ion levels and implant burden? (4) Does implant type (Ti-6Al-4V versus Co-Cr-Mo) influence serum metal concentrations? This was a single-center retrospective cohort study performed at an urban tertiary referral hospital from January 2018 to December 2020. A total of 336 patients with AIS were included, including 60% (201 of 336) who underwent surgical treatment and 40% (135 of 336) who received nonsurgical treatment. Among the 201 patients who underwent AIS operations, 6% (13 of 201) were excluded because of the presence of metal implants in other parts (ulna and radius [n = 5], around the elbow joint [n = 4], femoral shaft [n = 4]), and 15% (31 of 201) were excluded because they were lost to follow-up, resulting in incomplete clinical data. Forty-eight percent (96 of 201) of the patients only received spinal implant treatment without revision surgery (implant group), 23% (46 of 201) of the patients received spinal implant treatment and underwent revision surgery but did not have the implants removed (revision group), and 7% (15 of 201) of the patients received spinal implant treatment, underwent revision surgery, and had the implants removed (removal group). Among the 135 patients with AIS who did not undergo surgery, 6% (8 of 135) were excluded because of the presence of metal implants in other parts (ulna and radius [n = 3], around the elbow joint [n = 3], femoral shaft [n = 2]), and 16% (22 of 135) were excluded because they were lost to follow-up, resulting in incomplete clinical data. Seventy-eight percent (105 of 135) of the patients who did not undergo surgery who met the inclusion criteria were ultimately included in the control group. Since 2015, according to a standardized protocol, serum samples from patients undergoing surgery for AIS and from the nonsurgical control group have been collected. This is part of a broader and ongoing research project for patients with AIS. Between February and April 2025, we determined the metal ion concentrations in the collected blood samples. Serum Ti, Co, and Cr levels were measured via inductively coupled plasma mass spectrometry at multiple postoperative time points. The correlation between metal ion levels and rod length as well as the number of screws were evaluated using correlation analysis. Linear regression analysis was employed to assess the relationship between implant types (Ti-6Al-4V and Co-Cr-Mo), rod diameter, and serum metal concentrations. The extracted implants were subjected to scanning electron microscopy (SEM) combined with energy-dispersive x-ray spectroscopy analysis to examine the surface morphology and elemental composition of the implants. Serum concentrations of Ti, Co, and Cr were higher in patients with spinal implants than in nonsurgical controls at all postoperative time points. At 48 months, the mean ± SD serum Ti was 1.1 ± 0.3 μg/L in the implant group versus 0.2 ± 0.1 μg/L in controls (mean difference 0.9 μg/L [95% confidence interval (95% CI) 0.8 to 1.0]; p < 0.001), for Co it was 0.3 ± 0.2 μg/L versus 0.2 ± 0.1 μg/L (mean difference 0.1 μg/L [95% CI 0.1 to 0.2]; p < 0.001), and for Cr it was 1.0 ± 0.5 μg/L versus 0.1 ± 0.1 μg/L (mean difference 0.9 μg/L [95% CI 0.6 to 0.7]; p < 0.001). Metal levels peaked at 12 months postoperatively and remained elevated for 48 months. Implant removal was associated with a reduction in serum metal concentrations. At 6 months after removal, Ti levels decreased by 1.8 μg/L (95% CI -2.1 to -1.6; p < 0.001), Co levels by 0.4 μg/L (95% CI -0.5 to -0.3; p < 0.001), and Cr levels by 1.2 μg/L (95% CI -1.4 to -1.0; p < 0.001) compared with the removal group. At 12 months after removal surgery, there was no difference in Ti ion concentration between the removal group and the control group (0.2 ± 0.2 versus 0.2 ± 0.1, mean difference 0.0 [95% CI -0.2 to 0.1]; p = 0.38). Similarly, no difference was observed in Co ion concentration (0.2 ± 0.1 versus 0.2 ± 0.1, mean difference 0.0 [95% CI -0.1 to 0.1]; p = 0.62). Additionally, Cr ion concentration did not differ between groups (0.2 ± 0.1 versus 0.1 ± 0.1, mean difference 0.1 [95% CI -0.2 to 0.1]; p = 0.45). Serum metal concentrations correlated positively with implant load (rod length r = 0.85 to 0.87, number of screws r = 0.87 to 0.88; all p < 0.001) and rod diameter (β = 0.54 to 0.58; all p < 0.001).The serum Co concentration had a substantial positive correlation with the use of Co-Cr-Mo implants (β = 0.54; p < 0.001). Similarly, the serum Cr concentration had a substantial positive correlation with the use of Co-Cr-Mo implants (β = 0.58; p < 0.001). SEM analysis confirmed implant surface corrosion and nanoscale defects consistent with metal release. Serum levels of Ti, Co, and Cr increase after posterior spinal fusion in patients with AIS, reaching a peak at 12 months after operation, and remaining elevated for at least 4 years, which suggests continuous release of metal ions from the implants. Removal of the implants was associated with a reduction in serum metal ion levels, confirming that the implants are the main source of metal nanoparticle release. The concentration of metal ions is related to the burden of the implant (such as the length of the rod and the number of screws) and the type of implant. However, the clinical importance of elevated metal ions needs further confirmation. Our findings are preliminary and do not support routine metal ion tests or imaging examinations in patients with AIS treated surgically or recommendations regarding implant removal; however, future research may attempt to correlate ion levels with symptoms or imaging results in the study environment. Level III, therapeutic study.
The Li2CrVSi2 and Li2CrVGe2 DHH alloys are half-metallic ferromagnetic materials with band gaps of 0.7274 eV and 0.7989 eV. In the equilibrium lattice parameter values, the c/a ratio is 2. The alloys' total magnetic moments are 10.0 μB/f.u. The Debye temperatures are 376.801 K and 300.322 K. The formation energy values are -2.883 eV and -4.514 eV, while the cohesive energy values are -8.009 eV and -7.581 eV. These results support structural stability. The Curie temperatures of the Li2CrVSi2 and Li2CrVGe2 DHH alloys are 1349.68 K and 863.39 K. The maximum R(0) and n(0) values are 0.745, 0.743, 12.915, and 12.826, respectively. The extinction coefficient values are 2.565 and 2.466. The bulk modulus of the Li2CrVSi2 and Li2CrVGe2 are 64.2823 GPa and 59.9899 GPa. The maximum heat capacities are 293.699 J/mol.K and 296.787 J/mol.K. Electronic, optical, and thermodynamic properties indicate that the Li2CrVSi2 and Li2CrVGe2 DHH alloys are highly suitable materials for spintronic and optoelectronic technologies. Calculations were performed using the Wien2k program. The GGA + PBE and GGA + mBJ methods were used for electronic properties. Elastic calculations were done with IRElast software. For optical calculations, the photon energy range was selected as 0-10 eV. Thermodynamic calculations were also performed using the Gibbs2 code. Here, the temperatures and pressure were set to 0-1000 K and 0-10 GPa.
In this study, we investigate the structural, electronic, magnetic, and elastic properties of quaternary Heusler alloys FeZrTiX (X = Al, Si) using first-principles calculations based on density functional theory (DFT). The pressure-dependent behavior of these compounds is explored over the range of 0-50 GPa to evaluate their potential for spintronic applications. Our results reveal that the band gap of FeZrTiAl decreases with increasing pressure, while FeZrTiSi exhibits half-metallic behavior beyond 20 GPa-an essential trait for spintronic devices due to the emergence of 100% spin polarization. The total magnetic moment shows minimal variation under pressure, indicating robust and stable magnetic ordering. The elastic constants remain positive throughout the applied pressure range and satisfy the Born mechanical stability criteria, confirming mechanical integrity. Additionally, the Debye temperature increases with pressure, suggesting enhanced lattice stiffness. To complement the DFT insights, machine learning (ML) approaches were employed to predict the scalar band gap of FeZrTiAl and FeZrTiSi. ML models demonstrated good predictive performance as evaluated by the coefficient of determination (R2) and root mean square error (RMSE), capturing trends consistent with DFT calculations. As expected for spin-polarized half-metallic systems, ML predicted scalar band gaps were lower than DFT spin-resolved band gaps, reflecting averaging over spin channels by the models. These combined first-principles and ML results demonstrate that FeZrTiAl and FeZrTiSi possess pressure-tunable magneto-electronic properties, mechanical robustness, and half-metallicity, making them promising candidates for next-generation spintronic applications.
In the biodegradable metal class, Mg-based alloys are considered the most promising candidates for temporary implant manufacture. However, their high corrosion rate in physiological media is considered a main drawback for clinical translation. Conversion coatings address the limitations of Mg-based alloys and provide a strategy to control corrosion and improve surface biocompatibility. In this review paper, a detailed analysis of various conversion coating techniques, including ceramic conversion coatings based on metals, polymeric conversion coatings, bioactive conversion coatings, and hybrid conversion coatings, is performed. Attention is devoted to the corrosion process and parameters, as well as to the biological response in relation to bioactivity or biocompatibility. The main angiogenic and osteogenic signaling pathways are described based on the analyzed conversion coatings, and the evolution of the cellular response is estimated. Although significant progress has been made in the field, there are still challenges associated with synchronizing Mg alloy degradation with new bone formation and with precisely guiding cell signaling responses to achieve a desired biological response. An overall conclusion of the paper consists of the fact that conversion coatings are an important topic, as they can enhance the surface of Mg-based alloys, making them prone to clinical translation.
Designing and developing high-efficient bifunctional electrocatalysts toward both oxygen reduction (ORR) and oxygen evolution (OER) reactions is paramount to advance rechargeable Zn-air batteries (ZABs) technology, but remains challenging. Here, the strong-coupled PdFeNi nanoalloys and oxygen-deficient NiFe2O4 spinel nanohybrids (PdFeNi/NiFe2O4), are fabricated by atomic implantation and in-situ alloying strategy. Due to the dense heterointerfaces, unique lattice strain, abundant oxygen vacancies, and strong metal-support interactions, the electronic distribution and intermediates' adsorption in PdFeNi/NiFe2O4 are collectively optimized, meanwhile promoting lattice oxygen participation in OER. As a result, such PdFeNi/NiFe2O4 nanohybrids manifest outstanding bifunctional electrocatalytic performances with a potential difference of 0.74 V between OER and ORR. Using them as air electrode, the assembled aqueous ZABs can deliver high peak power density (156.1 mW cm-2), and maintain excellent round-trip efficiency (61.4%) after cycling over 1200 h, surpassing that of Pt/C + IrO2 counterparts. Moreover, further fabricated quasi-solid-state ZABs showcase good flexibility, recoverability and practicability, which can be employed to power various electronic devices. This work offers a novel strategy to develop strong-coupled nanohybrids as bifunctional oxygen electrocatalysts, which may spur their applications in clean energy conversion and storage devices.
The present study demonstrates that the corrosion behavior of dental cobalt-chromium (Co-Cr) alloys is strongly influenced by the interaction between microstructure, manufacturing technique, and oral chemical environment. A comparative investigation was conducted on Co-Cr specimens fabricated using four technological routes: conventional casting, CAD/CAM machining, Selective Laser Melting (SLM), and Direct Metal Laser Sintering (DMLS). The study included microstructural characterization, evaluation of generalized corrosion behavior using the rotating electrode technique, assessment of localized crevice corrosion, and quantitative analysis of the release of twenty metallic cations. Extraction tests were performed for 168 h in two media simulating aggressive oral environments: 0.07 N HCl (acidic medium) and a fluoride-containing electrolyte (0.1% NaF + 0.1% KF). Electrochemical measurements were recorded in the current density range of 10-10 to 10-7 A/cm2, while released cation concentrations were quantified at the µg/L level. All alloys exhibited very low corrosion current densities (icorr in the 10-8 to 10-9 A·cm-2 range), confirming overall good corrosion resistance. Among all manufacturing routes, CAD/CAM specimens demonstrated the highest electrochemical performance, with a wide passivity domain extending up to approximately 740 mV/SCE. A statistical interaction analysis between extraction media and manufacturing techniques was performed using the non-parametric Mann-Whitney (MW) U test. Among the analyzed elements, only chromium showed a statistically significant difference between media (p < 0.05), with an approximately 25-fold-higher release in acidic conditions compared with the fluoride medium, confirming the predominant role of proton-induced destabilization of the protective Cr2O3 passive film. In contrast, fluoride-containing media induced selective release of elements such as Cu (3× higher), W (2.5× higher), and Mo (1.4× higher), associated with complexation phenomena. The manufacturing route significantly influences corrosion behavior. Although additive manufacturing technologies (SLM/DMLS) enable highly accurate and customized prosthetic designs, rapid solidification and microstructural heterogeneities may increase susceptibility to localized corrosion compared with more homogeneous CAD/CAM materials. Clinically, these findings suggest that future restorative strategies should incorporate corrosion-aware material selection within digital workflows. As digital dentistry evolves, predictive models integrating patient-specific oral conditions may assist clinicians in selecting the most appropriate material system for long-term performance. In conclusion, the long-term success of dental Co-Cr prosthetic devices depends not only on mechanical strength and precision of fit, but also on sustained electrochemical stability in the complex oral environment.
Magnesium (Mg) alloys are promising for application as degradable bone substitutes due to their appropriate elastic modulus, which is closer to bone than that of permanent metallic biomaterials. Once implanted, Mg implants must provide adequate mechanical support to maintain the integrity of the injured site while promoting bone ingrowth to ensure optimal tissue healing. The aim of this study was to assess the quality of bone regeneration in a dog model via high-resolution X-ray computed tomography (XCT) at 4, 8 and 16 weeks following the implantation of Mg-based fibres into critical-sized defects. These results were compared to those induced by a commercially available bovine bone graft (BBG) and empty (E) controls. At 16 weeks, mechanical characterisation was also performed using digital volume correlation (DVC). Mg promoted greater bone formation (bone volume fraction of 0.77 ± 0.15, 0.53 ± 0.07 and 0.45± 0.06 at 16 weeks for Mg, E and BBG, respectively). New bone formation combined with homogenous and tight integration of the Mg fibres led to the complete restoration of the defect. The newly formed bone showed signs of increasing mineralization (541 ± 50 mg HA.cm-3), remodelling and angiogenesis after 16 weeks, enabling the Mg fibres to facilitate complete tissue healing and provide sufficient mechanical strength (3.32 ± 0.92 MPa and 152 ± 1 MPa for apparent yield stress and Young's modulus, respectively) to support loading. This study suggests that Mg-based fibres can promote osteointegration and osteoconduction enabling the reconstruction of critical-sized defects while maintaining the mechanical integrity of the injured site. STATEMENT OF SIGNIFICANCE: Magnesium is a highly promising biomaterial for bone regeneration; however, its rapid corrosion in physiological environments can compromise mechanical integrity and lead to treatment failure. This study investigates an innovative strategy designed to slow corrosion, combining 1) a magnesium alloy without aluminium, neodymium or gadolinium, elements commonly present in AZ31 or WE24 alloys but associated with poor biocompatibility and 2) a fluorine coating. The biological and mechanical performance of this composite biomaterial were assessed after implantation in a critical-size bone defect, using histological analyses, X‑ray computed tomography, and digital volume correlation to evaluate bone healing. The findings will contribute to the advancement of safe and effective biomaterials that can be translated to clinical solutions for bone tissue regeneration.
Hydrogen diffusion plays a key role in hydrogen-metal interactions and is closely linked to embrittlement in steels. In iron-based alloys, the influence of local atomic environments on hydrogen diffusion is well recognized, whereas the role of alloy composition remains unclear. Fe-Cr binary alloys, therefore, provide a simple and well-defined model system to isolate the effect of Cr on hydrogen diffusion in iron lattices. In this work, hydrogen diffusion in Fe-Cr alloys is investigated using first-principles calculations based on density functional theory. Ab initio molecular dynamics simulations are further employed to evaluate the influence of Cr concentration on hydrogen diffusion coefficients. The results show that hydrogen diffusion in Fe-Cr alloys is strongly suppressed compared with bcc Fe. This suppression is primarily attributed to higher migration energy barriers resulting from strong Fe-Cr interactions and more compact local atomic packing. Charge transfer analysis demonstrates that hydrogen behaves as an electron acceptor, and the amount of charge transferred is inversely related to the migration barrier. In the disordered solid-solution models, the hydrogen diffusion coefficient decreases with increasing Cr content in the low-Cr range, whereas in the ordered alloy models it exhibits a non-monotonic dependence on composition, with a minimum near 25 at. % Cr. These results reveal the electronic and structural origins of composition-dependent hydrogen diffusion in Fe-Cr alloys at the atomic scale.
Metal additive manufacturing (AM) relies on alloy feedstock powders that may come into contact with the workers' skin during handling, yet skin-relevant data on metal release and biological reactivity remain limited. Here, we assessed the cutaneous bioactivity of the fine particle fraction of four gas-atomized Fe-based AM powders (316L stainless steel, Fe-powder A, and tooling steels B and C). Powders were sieved to <10 μm and characterized by scanning electron microscopy and X-ray photoelectron spectroscopy before and after incubation in artificial sweat (ASW). Metal biodissolution was quantified in ASW and keratinocyte culture medium using atomic absorption spectrophotometry. Cellular responses were evaluated in HaCaT keratinocytes using Cell Painting-based phenomics and multiplex cytokine/chemokine profiling and in an ex vivo full-thickness human skin explant model, including superficial barrier disruption, IL-8/CXCL8 quantification, and histological assessment. ASW exposure induced marked shifts in the outermost surface composition across powders, indicating sweat-driven surface transformation. Biodissolution was low and medium-dependent, with Fe dominating the release in ASW, and with an overall metal release remaining limited in cell culture medium. In HaCaT cells, MCP-1/CCL2, IL-6, and IL-8/CXCL8 were quantifiable but showed no significant changes following powder exposure. Cell Painting revealed subtle, shared phenotypic signatures, primarily involving mitochondrial-associated features, without evidence of broad cellular stress. In the ex vivo skin model, AM powders did not increase IL-8/CXCL8 secretion, the particles remained localized to the skin surface without detectable penetration, and coexposure with Staphylococcus epidermidis did not enhance bacterial colonization or induce inflammation. To the best of our knowledge, this is the first study that applies a human skin explant model to evaluate dermal responses to metal AM powders. Overall, the tested AM powders showed low short-term cutaneous reactivity under skin-relevant conditions, providing human-relevant evidence to inform occupational risk assessment in AM environments.
The mechanical response of 7xxx aluminum alloys is strongly influenced by both alloy chemistry and the resulting microstructure. In this study, the effect of precipitate characteristics on the fatigue behavior of three 7xxx aluminum alloys with different total amounts of main alloy elements was systematically investigated. Quantitative microstructural characterization was performed under T6 and T74 heat-treatment conditions by combining scanning electron microscopy, transmission electron microscopy, and electron backscatter diffraction. Meanwhile, hardness measurements, room-temperature tensile tests, and fatigue crack growth experiments were carried out to evaluate the mechanical behavior. The results show that, within the present alloy set, the over-aged condition and the alloys with higher overall alloying levels exhibited lower fatigue crack growth rates, which correlated with the coarsening of intragranular precipitates. Such microstructural evolution is suggested to facilitate dislocation motion and thereby reduce fatigue damage associated with dislocation pile-up in the present alloy set. In this work, three typical 7xxx aluminum alloys with different alloying levels were systematically investigated under T6 and T74 conditions. A statistical criterion was established to distinguish GPII zones from η' precipitates, and a model linking precipitate characteristics to fatigue crack growth behavior was further developed. The present study aims to provide a quantitative framework for understanding and predicting the fatigue behavior of 7xxx aluminum alloys with different total amounts of main alloy elements.
The increasing demand for portable electronics and electric vehicles has made the development of advanced electrochemical energy storage systems essential. Lithium-ion batteries (LIBs), which predominantly use graphite anodes, face limitations in capacity and performance at high current rates. As a result, alternative anode materials such as tin (Sn) and antimony (Sb) have gained attention for both LIBs and sodium-ion batteries (SIBs) as well, due to their high theoretical capacity. However, their practical application is hindered by significant volume expansion during cycling, leading to electrode degradation. This study presents a novel approach to improve the stability and performance of Sn and Sb anodes by incorporating them into a laser-induced graphene (LIG) matrix. LIG was synthesized via laser ablation of a polyimide precursor mixed with metal-salt precursors, directly onto a copper current collector, enabling the in situ formation of Sn and Sb metallic nanoparticles (NPs) and SnSb alloy NPs, embedded in a few graphene layers. The localized high-temperature generated by the laser facilitated nanoparticle formation while simultaneously creating a protective carbon shell around the NPs, mitigating volume expansion and enhancing electrochemical stability. Electrochemical testing demonstrated that the LIG-metal composites exhibited superior performance compared to bare LIG in both LIB and SIB. LIG-Sn composite achieved the specific capacity of 380 mAh g-1 in LIBs and 155 mAh g-1 in SIBs after 80 and 50 cycles, respectively. These results highlight the potential of LIG-based Sn and Sb composites as scalable, binder-free anode materials for next-generation rechargeable batteries.
Bone repair remains a major clinical challenge. Although traditional metal implants, such as titanium and its alloys, provide mechanical strength, they are often limited by stress shielding, insufficient osseointegration, and a lack of biological activity. Recent advances in metallic topological structures offer a promising solution by integrating mechanical adaptability with biological functionality. This review systematically summarizes the design, properties, and biological interactions of metallic topological implants for bone repair. We first compare conventional metallic materials and their limitations, followed by an overview of manufacturing strategies, including structural and surface modification techniques, unit cell-based architectures, topology optimization, and reverse-engineered biological designs. The potential integration of machine learning and 4D printing is also highlighted as a future direction for personalized implant design. At the biological level, we discuss how topological cues regulate cellular responses through mechanotransduction pathways, osteogenic differentiation signaling, angiogenesis regulation, and immune modulation. Finally, we analyze the practical applications of metallic topological structures in orthopedic implants, as well as the remaining technical and translational challenges. Overall, this review emphasizes the potential of metal topologies to create a new generation of implants with greater mechanical adaptability and better biological performance. The Translational Potential of this Article: This work offers insights into the development of orthopedic metallic topological implants with enhanced mechanical and biological performance. The integration of metallic topologies with emerging technologies like 4D printing and machine learning could lead to highly personalized solutions for bone repair, addressing current limitations in clinical applications and improving patient outcomes.
Lightweight high-entropy alloys are primarily designed to overcome the strength-to-density ratio limitations of conventional counterparts and often consist of elements with drastically different melting temperature and vapor pressure. Their chemistry, therefore, imposes challenges on alloy synthesis, particularly through liquid metal engineering routes, since elements with high vapor pressure (e.g., Mg, Zn, Li) vaporize before the higher-melting-point ingredients (e.g., Cu, V, Ni) are fully molten, resulting in volatile element loss. To overcome this challenge, a novel pressure-assisted induction melting (PAIM) process was developed and the proprietary furnace for its implementation was designed and built. The system allows precision melting of up to 10 cm3 of an alloy at temperatures up to 1700 °C while addressing the partial pressure requirements during the melting progress. The chamber is prepared using rough vacuum and re-filled with inert gas such as argon with the operating pressure range from about 10-4 MPa up to maximum of 1.6 MPa (233 psi). The alloy chemical composition can be modified in situ by feeding solid additives at specific melting stages through the isolated airlock without disrupting the pressure conditions within the chamber. The viability of the concept was verified by synthesis of two lightweight non-equimolar high-entropy alloys: Mg-rich Mg50(MnAlZnCu)50 and Al-rich Al35Mg30Si13Zn10Y7Ca5. The experiments showed that sequential multi-step melting procedures, designed based on inputs from FactSage computational analysis, when combined with PAIM synthesis, allowed manufacturing fully dense and chemically homogenous complex alloy compositions with optimal volumes for materials discovery research.
This review investigates the critical role of surface treatment and post-processing techniques in enhancing the performance and biocompatibility of metal bio-implants. The paper addresses the challenges posed by the significant difference in Young's modulus between natural bone (15-45 GPa) and metal alloys (110-240 GPa), which leads to stress shielding effects and potential toxic ion release. The review first details various surface coating methods, including ion implantation and anodization, highlighting their ability to improve tribological resistance, corrosion resistance, and biocompatibility. The detailed analysis gives surface modification techniques, such as laser shock peening, Nitrogen Plasma Immersion Ion Implantation (NP-III), and anodization, which are used to enhance titanium implant properties, such as increasing surface hardness, promoting tissue growth, and creating a bio-active oxide layer. Furthermore, the paper explores post-processing methods such as laser shock peening (LSP) and surface texturing, which are crucial for modifying the surface topography and microstructural properties of implants. It also discusses techniques, particularly laser-based texturing, to reduce friction and wear while inducing beneficial compressive residual stress. The review concludes by emphasizing that a tailored approach to surface modification and post-processing is essential for developing safe and effective bio-implants for a wide range of applications, from bone fixation to load-bearing joints.
Aluminum is the second most widely used metal worldwide, with essential roles in transportation, construction, packaging, and energy infrastructure. Recycling aluminum can save up to 95% of the energy required for primary production, making it a cornerstone of low-carbon manufacturing. However, recycled aluminum alloys inevitably contain higher levels of iron, which promotes the formation of brittle microscopic phases that degrade performance and limit industrial use. These phases can appear in different forms and dispersion depending on alloy composition and processing. Yet, practical guidelines for controlling them remain largely empirical and qualitative, especially when data are limited. To improve this situation, this work separates two key questions that are often conflated in alloy design: which phase type forms, and how strongly that phase affects material behavior once it appears. Using data representative of industrial conditions, we show how alloy chemistry and processing history determine which phases form and govern whether these phases develop as a few large, platelet-like features or as many small, compact particles. By clarifying these distinct roles of composition and processing, the results provide a simple and actionable framework for mitigating deleterious iron-rich phases in recycled aluminum alloys and enabling more quantitative, predictable, and impurity-tolerant sustainable alloy design.
Superalloys are widely recognized as ideal materials for high-temperature structural applications. Traditionally, these alloys have been manufactured from mined metal by using conventional alloying techniques. In this proof-of-concept study, we successfully made a Ni-based superalloy from waste batteries through a single-step selective in situ reduction technique bypassing the conventional norms of superalloy production. Spent batteries from obsolete electronic products and electric vehicles represent a valuable resource, as they house critical metals and minerals (e.g., Co, Ni, Mn, Graphite, and REEs) essential for superalloy production. We recycled these critical metals and minerals from spent batteries and made a Ni-based superalloy. Beyond contributing to responsible material consumption, the comprehensive compositional and structural profiling reveals that this superalloy exhibits potential for oxidative, corrosive, and various structural applications, attributed to its distinctive γ/γ' nanostructure. This cutting-edge study outlines a strategic method for creating superalloys from waste batteries, decreasing the need for traditional mining and alloying.
Ligand isomerism can effectively modulate the properties of clusters. Herein, a series of alloy (AuAg)13 nanoclusters (NCs) capped by 2- or 4-mercaptopyridine were synthesized and well determined. Results showed that all four NCs exhibit pronounced multiphoton absorption under near-infrared (NIR) excitation, and 4-mercaptopyridine coordinated clusters display significantly enhanced multiphoton absorption coefficients and cross-sections compared with their 2-mercaptopyridine coordinated analogues. Complementary density functional theory and time-dependent density functional theory calculations show that 4-mercaptopyridine ligation shifts the relative positions and densities of excited-state energy levels, alters the states contributing to low-energy absorption, and enhances ligand-to-metal charge transfer (LMCT), thereby accounting for the experimentally observed increase in nonlinear optical response. This work provides an intriguing ligand-engineering strategy and a cluster platform for stepwise control of the nonlinear optical behaviour of (AuAg)13 alloy nanoclusters and sheds light on the precise correlation between the ligand structure and nonlinearity at the atomic level.
PCB recycling is crucial due to the growing electronic waste, which poses significant environmental hazards from hazardous materials like heavy metals. Traditional recycling methods, involving strong acids and high temperatures, generate toxic chemical waste and release hazardous fumes. As a result, it is essential to investigate green alternatives to reduce these environmental hazards. This study investigates the recovery of copper from waste printed circuit boards (PCBs) using a green, oxidant-free two-component deep eutectic solvent (DES) composed of choline chloride and malonic acid (ChCl: MOA), without an oxidant agent. The influential parameters-temperature, leaching time, PCB/DES mass ratio, and agitation speed-were optimized using Taguchi method, revealing that higher temperatures and longer leaching durations significantly enhance copper extraction. Analysis of variance (ANOVA) confirmed that temperature, leaching time, and PCB/DES ratio as statistically significant factors, whereas agitation speed had a negligible impact within the studied range. According to the optimization evaluation, maximum copper recovery of 89.5% was achieved under conditions of 100 °C temperature, 360-min leaching time, 0.04 g/g PCB/DES ratio, and 200 rpm agitation speed. Complete recovery was observed for Ag, while Sn showed a moderate recovery of 77.2%, which attributed to its alloying with copper and its limited dissolution in DES. Cu2+ forms stable [CuCl4]2- complexes in the ChCl: MOA DES via strong first-shell coordination with Cl-, as confirmed by molecular dynamics (MD) simulations and UV-Vis spectroscopy. RDF and coordination number analyses reveal a negligible interaction between Cu2+ and MOA. Additionally, hydrogen bonding is dominated by ChCl-Cl- interactions, while MOA is primarily involved in intramolecular hydrogen bonding, limiting its contribution to solvation and metal coordination after leaching.
Background/Objectives:Staphylococcus epidermidis (RP62A) and Staphylococcus aureus (UAMS-1) are clinically relevant pathogens frequently implicated in implant-associated infections due to their ability to form biofilms. RP62A is typically linked to persistent, chronic, low-grade infections, whereas UAMS-1 is associated with acute, invasive disease. Both strains serve as representative models for chronic and acute periprosthetic joint infections (PJIs). The objective of this study was to examine and compare in vitro biofilm formation by RP62A and UAMS-1 on orthopaedic materials/disc surfaces of defined composition. Methods: In vitro biofilm formation assays were performed using orthopaedic disc surfaces composed of cobalt-chromium alloy (CoCr), titanium alloy (Ti), and polyethylene (PE) after 72 h of incubation. Biofilm biomass was quantified using crystal violet staining, with absorbance measured at OD570. A polystyrene (PS) surface served as a control. Additionally, retrieved orthopaedic explant components were used as substrates for in vitro biofilm assays, in which RP62A was incubated for 72 h on the explanted surfaces. Supporting assays on glass slides were conducted to examine strain-specific biofilm-related architecture. Results: In vitro biofilm mass quantification assays showed strong biofilm formation by RP62A across all tested surfaces, with the highest absorbance on CoCr (OD570 = 5.80 ± 0.19). Notably, biofilm formation on CoCr was 76% higher compared to PS (p < 0.0001). No significant differences were observed among all three surface discs (p > 0.1). Biofilm formation was highest on PE for UAMS-1 (OD570 = 1.29 ± 0.09) and was significantly greater than on Ti (178%, p < 0.001) and CoCr (196%, p < 0.0001). In the in vitro assays performed on retrieved explant components, RP62A showed pronounced biofilm accumulation on polyethylene tibial inserts, particularly in regions of mechanical wear and friction. Supporting assays on glass slides were performed to examine strain-specific surface microstructural, revealing dense network-like structures for RP62A and thinner, discontinuous layers for UAMS-1. Conclusions: RP62A formed dense biofilms in vitro on multiple orthopaedic implant materials and retrieved explant components, consistent with its association with chronic periprosthetic joint infections. Increased biofilm accumulation was observed on mechanically worn polyethylene surfaces. In contrast, UAMS-1 showed lower biofilm formation on metallic disc surfaces, indicating strain- and material-dependent differences. These findings highlight the relevance of implant material selection and surface integrity for strategies targeting biofilm-associated implant infections.