Search Results (903)

Metal additive manufacturing (AM) plays an increasingly important role in sustainable production owing to its material efficiency, design freedom, and compatibility with circular economy (CE) strategies. Yet the high cost and environmental burden of producing virgin metallic powders remain major barriers to large-scale adoption. This review synthesizes current and emerging approaches for recycling metallic powder feedstocks within AM, organizing them into four pathways: reusing, reconditioning, repurposing, and resourcing. Reusing preserves powders within the AM loop through controlled handling and qualification strategies, whereas reconditioning applies mechanical, thermal or chemical treatments to restore powder properties. Repurposing redirects powder to alternative value-added routes, including wire feedstock, metal–polymer composites, extrusion materials, and elemental or oxide recovery. Resourcing generates new powder from end-of-life powder, printing scrap, and waste through mechanical size reduction, atomization-based processes, or solid-state conversion routes. Across these pathways, the review highlights technological advances, process limitations, and cross-cutting challenges related to oxidation, morphology deterioration, contamination, and scalability, and identifies underexplored methodologies with potential for AM-specific recycling. By integrating insights across the field, this work outlines the expanding landscape of metallic powder circularity and demonstrates how diversified recycling strategies can reduce environmental impact, lower material costs, and support a more sustainable AM ecosystem. Full article

The selection of materials for enhancing the energy performance of historic mosque structures, which form a significant part of Türkiye's cultural heritage, should be based on scientifically supported methodologies and should also consider their architectural nature. In this work, an innovative Energy3D–MADA approach is developed for the comparative evaluation of thermal performance and sustainable selection of heritage natural stones. The proposed framework concentrates on the thermal aspect, while environmental, economic, mechanical, and material-related acoustic indicators are used as supplementary decision indicators. The study examined eight representative heritage natural stones using a representative Ottoman composite masonry wall. For the four climatic regions of Türkiye, the energy performance was predicted, and 32 scenarios were obtained. The annual heating and cooling energy requirements, total operational energy, operational CO ₂ emissions, and costs of wall manufacturing were investigated through Energy3D. The results of the simulation indicated that the natural stones had a considerable impact on the performance of historic mosque buildings. Od Stone (Tuff) had the lowest heating and cooling annual energy demand, the minimum total operational energy consumption, and the fewest operational CO ₂ emissions among all the alternatives considered, while Red Granite had the greatest energy demand. Compared to Red Granite, Od Stone achieved reductions in annual heating energy of 31%, in total operational energy consumption of 22–25%, and in operational CO ₂ emissions of 22–25%, with only about a 1% increase in comparative initial construction cost. Spearman's rank correlation analysis (ρ) indicated the same ranking in all climate regions, which demonstrated the ranking consistency of the Energy3D-based analysis. Overall, the Energy3D simulation outcomes were combined with the LODECI, MEREC, SPC, SIWEC-M, and ALPAS techniques to formulate a decision-support system for the comparative analysis and prioritization of heritage natural stones, to support sustainable mosque design and heritage conservation planning. Full article

Aligned recycled carbon fiber (rCF)/polyetherimide (PEI) tapes are a promising material for lightweight aerospace thermoplastic composite structures with reduced environmental impact, provided that their directional properties can be translated into robust components. To assess the viability of rCF/PEI for aircraft interior applications, this study tracks the development of the “Eco Bracket” across four key stages: sustainability screening, coupon characterization, microstructural interpretation, and application-level structural assessment. A project-level life-cycle assessment compared an Additive Fusion Technology (AFT) rCF/PEI bracket with cast and milled aluminum routes and yielded a short-term climate impact of 0.678 kg CO₂-eq for rCF/PEI, representing a significant reduction compared to 5.1 kg CO₂-eq for cast aluminum and 20.9 kg CO₂-eq for milled aluminum. Coupon testing characterized the anisotropic mechanical response of the rCF/PEI tape, including the elastic moduli and strengths under axial and transverse tension, in-plane shear, and axial and transverse compression. Scanning electron microscopy of a representative fracture surface showed a rough, fiber-dominated morphology with exposed fiber bundles, pull-out, and local variations in matrix coverage, supporting the interpretation that consolidation and local wet-out quality govern the transfer from coupon capability to component performance. At the application level, the manufactured rCF/PEI bracket achieved a peak load of 3517.6 N, corresponding to 93% of the strength of an industry-standard polyetherketoneketone (PEKK) reference bracket, and failed in the fastener-hole region predicted as critical by the finite element model. The combined results indicate that aligned rCF/PEI tapes can deliver mechanical properties consistent with the design requirements of aircraft interior brackets, while process robustness, fiber-path fidelity, and local consolidation quality remain the key barriers to repeatable component performance. Full article

As naturally occurring bioactive molecules derived from plants, polyphenols exhibit significant potential for the functional modification and structural regulation of metal–organic frameworks (MOFs) due to their unique ortho-phenolic hydroxyl groups, excellent metal-coordinating ability, and favorable biocompatibility. This review systematically summarizes the functional roles of polyphenols in MOF systems, including their use as organic ligands to directly participate in framework construction, as surface modifiers to optimize MOF interfacial properties, or as encapsulation hosts to enable controlled loading and release. Polyphenol–MOF composites constructed based on these strategies demonstrate broad application prospects in fields such as biomedicine, food science, environmental remediation, and catalysis. This paper further analyzes the key challenges currently facing the research community, including unclear mechanisms of interfacial interactions, insufficient stability assessments under complex conditions, and a lack of scalable green synthesis processes. Future research should delve deeper into the relationship between polyphenol structures and MOF topological configurations and drive the transition from functional composites to functional synergies. These efforts will be key to realizing the practical application of such materials in intelligent food manufacturing, precision medicine, and sustainable environmental management. Full article

This paper explores the technical, economic, and environmental viability of producing secondary wrought aluminium alloys from post-consumer scrap. The technical review relates to the industrial-level use of laser-induced breakdown spectroscopy (LIBS) in automated scrap sorting under realistic operating conditions. First, process scrap was used to determine the accuracy of LIBS in sorting and separating wrought aluminium alloys, and then the method was applied to post-consumer scrap streams. The melted products were then analyzed, and their chemical compositions were confirmed using optical emission spectroscopy (OES) to meet the established alloy specifications. The economic analysis compares traditional recycling routes of cast alloys with a second route in which recyclers provide already sorted secondary wrought alloys, with a focus on cost and market feasibility. Simultaneously, an environmental analysis using life cycle analysis (LCA) measures the effects of sorting and manufacturing procedures. The results show that LIBS can effectively sort secondary wrought aluminium under controlled input conditions. The process reaches a break-even point in about five years when a 50% price premium for secondary wrought alloys over mixed scrap is assumed. The method is environmentally beneficial, with the global warming potential per kilogram of aluminium reduced by over 95% compared to the global average. The findings highlight the significant potential of combining advanced sorting technologies, new business models, and sustainability-oriented practices to support the implementation of circular material flows in aluminium recycling. Full article

The increasing availability of recycled carbon fibres (rCFs) from manufacturing waste and end-of-life composite structures offers new opportunities for sustainable, high-performance composites. However, the discontinuous nature of recycled fibres requires efficient alignment and consolidation. In this study, highly aligned discontinuous carbon fibre tapes were manufactured from recycled carbon staple fibres and bio-based polyamide 11 (PA11) fibres using a textile-based processing route and compression moulding. Two material systems containing nominal fibre mass fractions of 50 wt.% and 70 wt.% rCF were investigated. The resulting laminates were characterised in terms of fibre volume content (FVC), fibre orientation distribution, and mechanical performance. FVC of up to 56.72 vol.% were achieved for the 70 wt.% rCF material. Tensile testing revealed a significant increase in stiffness and strength with increasing fibre content, reaching values of 48.1 GPa and 866 MPa. The longitudinal compression modulus and the in-plane shear modulus showed similar trends, while the transverse tensile strength and compressive strength remained strongly influenced by local defects and fibre–matrix interactions. A 2D mesoscopic image analysis demonstrated a pronounced preferential fibre orientation, with approximately 69% of the analysed fibre regions aligned within ±10° of the dominant fibre direction. The derived alignment coefficient η₀ correlated well with the tensile modulus, confirming the strong influence of mesoscopic fibre architecture on mechanical performance. The results demonstrate that the combination of bio-based PA11 and oriented rCF, enabled through textile-based alignment technologies, provides a promising pathway towards sustainable lightweight composite structures. Full article

Global decarbonization represents one of the defining challenges of the 21st century. Geothermal energy offers a robust alternative for reducing fossil fuel dependency for both residential and industrial heating and cooling. While shallow geothermal systems are versatile and high-performing, comprehensive Life Cycle Assessments (LCA) remain scarce in the literature. This study evaluates the environmental impact of the manufacturing and installation processes of next-generation coaxial probes featuring a galvanized steel outer tube and an internal polyethylene pipe. The LCA identifies material composition as the primary environmental driver: steel production accounts for 41% of the total impact, while the hot-dip galvanization process contributes 30%, significantly affecting the “climate change” and the “resource use” categories. A comparative LCA with conventional double U-tube installations shows similar overall environmental impacts. A sensitivity analysis on the coaxial probes was conducted to explore potential mitigation strategies aimed at reducing the associated environmental impacts, providing indications for sustainable eco-design. The LCA results demonstrate that optimizing the design, specifically by reducing the steel quantity in the coaxial outer tube and avoiding the zinc coating process, results in a 34% reduction in total environmental impact, confirming that LCA is a fundamental tool for supporting the environmental sustainability of developing technologies. Full article

Background: The development of naturally derived pharmaceutical excipients has attracted increasing interest as alternatives to conventional synthetic materials. Methods: In this study, starch–beeswax composites were prepared using native rice starch (RS) and spray-dried rice starch (SDRS) through melt levigation (ML) and emulsification (EM) techniques at starch-to-beeswax ratios of 9:1, 8:2, and 7:3. The physicochemical properties, surface hydrophobicity, morphology, tabletability, and lubrication performance of the resulting composites were evaluated and compared with magnesium stearate (MGS) and hydrogenated vegetable oil (HVO). Results: Co-processing with beeswax markedly increased the water contact angle from 35.4° and 59.7° for RS and SDRS, respectively, to values ranging from 94.5° to 125.1°, indicating successful modification of surface hydrophobicity. SEM analysis demonstrated changes in particle morphology and surface appearance following co-processing, while FT-IR confirmed the coexistence of characteristic starch- and beeswax-associated spectral features without evidence of detectable covalent modification. Co-processed formulations generally maintained or improved tabletability relative to their corresponding starch bases, with SDRS-based composites producing substantially harder tablets than RS-based formulations. The composites also reduced tablet ejection force and improved tablet mechanical properties compared with lubricant-free formulations. Among all samples, SDRS-EM-73 exhibited the best overall performance, reducing ejection force from 386.5 N for the lubricant-free control to 89.2 N, a value comparable to HVO (93.0 N), while producing tablets with high hardness (60.9 N), low friability (0.16%), and acceptable disintegration time (44.8 s). Conclusions: These findings demonstrate that co-processed starch–beeswax composites, particularly SDRS-EM-73, show considerable potential as naturally derived excipients for tablet manufacturing and may serve as sustainable alternatives to conventional tablet lubricants. Full article

Fe-based medium-entropy alloys (MEAs) are a cost-effective class of multi-principal-element alloys with tunable mechanical behavior. Their key advantage lies in the ability of Fe-rich, non-equiatomic compositions to regulate phase stability, deformation behavior, and strain hardening without relying heavily on expensive Co, Ni, or V. Increasing evidence shows that metastable face-centered cubic (FCC) matrices can provide excellent combinations of strength and ductility when their transformation behavior is properly controlled. Through compositional tuning and microstructural regulation, the phase stability, stacking-fault energy, precipitation behavior, and deformation pathways of Fe-based MEAs can be adjusted to achieve a balance between strength, ductility, and service reliability. This review critically synthesizes the metastability, microstructure, strengthening mechanisms, and service-oriented design principles of Fe-based MEAs. The literature discussed in this review was selected from peer-reviewed studies that report clear links among alloy composition, processing history, microstructure, deformation behavior, and mechanical or service-related properties. Unlike reviews that mainly classify alloy systems or deformation modes, this work emphasizes how metastability engineering and microstructural design can be integrated to guide application-specific alloy development. Representative Fe-rich non-equiatomic alloy systems are compared to clarify how alloying and processing regulate metastability, precipitation behavior, transformation kinetics, and strain partitioning. This review highlights that superior properties arise from the coordinated control of metastability, heterogeneous microstructures, and strengthening mechanisms. A central conclusion is that controlled transformation kinetics, rather than the pursuit of a maximum martensite fraction, is the key design variable for sustaining strain hardening and achieving stable strength–ductility synergy. Remaining challenges include quantitative deconvolution of coupled mechanisms, reliable prediction of local metastability, long-term microstructural stability, manufacturability, cost–performance balance, and integration of high-throughput experiments with computational alloy design. Overall, this review provides a service-oriented design framework for high-performance, low-cost Fe-based MEAs through the integrated control of composition, metastability, microstructure, processing, strengthening mechanisms, and application-specific performance. Full article

Integration of composites into the fabrication process of structural assemblies within the aerospace, automotive, marine or civil engineering industries represents a rational solution adopted by leading companies which are guided by the necessity for novel low-weight, high-strength, and high-stiffness materials. During the manufacturing process and throughout the service life, fiber-reinforced polymer structures are subjected to impact loading, either accidentally or as an inherent requirement of the operational cycle. Firstly, general aspects regarding impact loading and some parameters used for its characterization are briefly described. Recent progress regarding the influence of the stacking sequence, fiber type, and impactor geometry on the impact performance of Kevlar and glass fiber reinforced composite materials is emphasized. Additionally, the effects of environmental factors (such as temperature, UV radiation, or humidity) on the impact energy absorbed by polymers reinforced with each of the two types of synthetic fibers are presented. Finally, the importance of directing the researcher’s judgment towards improving the characteristics of materials subjected to impact, from a sustainable perspective, is motivated through the presentation of the impact behavior of polymer composites reinforced with Kevlar fibers or glass fibers hybridized with vegetable fibers. Full article

Meat and meat products are highly susceptible to microbial spoilage, lipid oxidation, moisture loss, discoloration, and sensory deterioration, creating a need for effective, safe, and sustainable packaging solutions. Although previous studies have investigated biodegradable polymers, nanomaterials, and active packaging systems separately, an integrated assessment connecting material design, preservation mechanisms, safety, sustainability, and commercial feasibility remains limited. This review addresses this gap by critically evaluating recent advances in biodegradable nanocomposite films and coatings for meat preservation. Current evidence demonstrates that the incorporation of nanoscale reinforcements and bioactive agents into biopolymer matrices can enhance their mechanical performance, gas and moisture barrier properties, antimicrobial activity, antioxidant capacity, and controlled release behavior. However, these advantages are strongly influenced by the nanofiller characteristics, concentration, dispersion, polymer-nanofiller interactions, food matrix composition, and storage conditions. Excessive nanomaterial incorporation may promote aggregation, induce structural defects, reduce flexibility, and increase migration concerns. Despite promising preservation outcomes, most available studies remain limited to laboratory-scale investigations, variable testing protocols, and insufficient validation under real commercial conditions. Key challenges hindering industrial adoption include nanoparticle migration, long-term safety assessment, regulatory uncertainty, production costs, consumer acceptance, and limited life-cycle evaluation. Future research should focus on safe-by-design formulations, standardized real-food testing, scalable manufacturing approaches, controlled-release technologies, and integrated assessments of preservation efficiency, safety, economic feasibility, and environmental sustainability. Overall, biodegradable nanocomposite packaging represents a promising approach for extending meat shelf life; however, successful commercialization requires balancing enhanced preservation performance with safety assurance and industrial practicality. Full article

Polyhydroxybutyrate (PHB) composites represent a promising sustainable solution to address the environmental challenges posed by conventional polymers across multiple sectors. This comprehensive review synthesizes current knowledge on PHB-based composites, examining their development, performance, and biodegradation characteristics in diverse applications such as packaging, biomedical devices, agriculture, aerospace, and environmental remediation. Various composite fabrication methods, including melt blending, solution casting, electrospinning, and in situ polymerization, are evaluated for their impact on functional properties. Natural fiber- and nanomaterial-reinforced PHB composites are critically analyzed for their mechanical integrity, thermal stability, surface chemistry, biodegradability, and environmental compatibility. Practical challenges, including manufacturing scalability, cost-effectiveness, and long-term stability in complex environments, are discussed within circular economy and regulatory frameworks to situate PHB composites for realistic industrial and environmental deployment. This review provides timely insights for researchers and practitioners aiming to develop environmentally compatible, scalable biopolymer-based solutions across multiple domains. Full article

During operation, several parts of the thermal reactor burners sustain heavy damage and need to be replaced. Different solutions for parts manufacturing are investigated: thermal spraying, Selective Laser Melting (SLM), and hardfacing by Directed Energy Deposition plasma arc (DED-arc). Based on the comparison to original material and the duration of usage, application of those three methods for replacement is studied in order to determine the most suitable one, with Additive Manufacturing (AM) being proposed for targeting the problem. Thermal-sprayed items have a zirconium-oxide-based outer layer. SLM produces a monolithic item, while with the help of DED-arc, a composite structure with a sound metallurgical bond between the base and the added material is produced. The microstructures with the interface zones are observed. Samples are machined and ground, and their friction characteristics are taken with the help of acoustic emission (AE) and Electrical Contact Resistances (ECR) sensors during scratching. As a result, overlaying of the base stainless steel by DED-arc is proposed due to the better metallurgical stability of the added mixture in a hot environment above 800 °C and its hardness characteristics. Full article

Amid the accelerated global transition toward sustainable electromobility, Chinese Electric Vehicles (EVs) have forged a complex, evolving communication ecosystem across overseas social media platforms. Conceptualizing global digital discourse as a complex adaptive system (CAS), this study integrates CAS theory with Competitive Framing theory to systematically elucidate the thematic configurations, framework dynamics, and ecological activation mechanisms underlying the international image of Chinese EVs. By integrating unsupervised BERTopic modeling, Large Language Model (LLM) semantic mapping, the Entropy Weight Method (EWM), and Social Network Analysis (SNA), this inquiry operationalizes a comprehensive computational communication framework to mine large-scale behavioral and textual data from YouTube. The empirical findings unveil that: (1) international audience perceptions have broken through the traditional “low-cost manufacturing” stereotype, spontaneously giving rise to a multidimensional, composite cognitive schema centered on smart ecosystems and design experiences; (2) driven by the interplay of rational and irrational user feedback loops, the ecological activation efficiencies across diverse discursive dimensions exhibit pronounced nonlinear variances, characterized by a “strong activation of intelligent ecosystems versus a long-tail stagnation of cost-effectiveness salience”; and (3) positive technological frameworks and negative geopolitical or regulatory risks engage in fierce, adversarial contestation and structural hybridization within a highly volatile network topology, culminating in a unique “dual-core” configuration. Theoretically, this study enriches the scholarly understanding of country-of-origin and corporate brand images through a complex systems lens; methodologically and practically, it offers a high-fidelity, actionable quantitative paradigm for global brand empowerment and targeted cross-border public opinion governance. Full article

Selective laser melting (SLM) can effectively suppress metallurgical defects inherent to conventional manufacturing; however, subsequent aging treatments essential for engineering applications introduce secondary precipitates that alter the electrochemical homogeneity of the matrix. The underlying mechanism by which such precipitation behavior governs corrosion resistance remains elusive. In this study, a Fe-30Mn-8Al-1.5C-2.5Ni steel was investigated to elucidate the corrosion morphology and electrochemical behavior of the as-built, 450 °C-aged, and 750 °C-aged specimens during immersion in a 3.5 wt.% NaCl solution. The results demonstrate that the inherent Mn microsegregation and high-density subgrain boundaries induced by SLM trigger preferential localized anodic dissolution on the surface of the as-built sample, culminating in the formation of a loose, porous manganese oxide product layer. Aging treatment at 450 °C induces extensive precipitation of κ-carbides within grain interiors and along grain boundaries, accompanied by localized depletion of Al and Mn at the phase interfaces. A pronounced micro-galvanic coupling established between the κ-carbides and the adjacent Al-depleted zones directly compromises the continuity of the passive film, thereby further deteriorating the corrosion resistance. In contrast, aging at 750 °C relieves the residual stress and eliminates the as-built elemental microsegregation. The resulting compositional homogenization of the matrix reduces the localized electrochemical driving force, which promotes a uniform reaction of Al at the surface to construct a continuous, compact Al-rich passive film, thereby sustaining the highest charge-transfer resistance during long-term immersion. This work elucidates the correlation among the intrinsic defects of SLM, aging-induced solute-depleted zones, κ-carbide precipitation, and localized micro-galvanic corrosion, providing a fundamental basis for tailoring the microstructure and corrosion resistance of additively manufactured lightweight steels. Full article