Search Results (1,003)

In Directed Energy Deposition (DED), modeling the molten pool temperature field is crucial for precise temperature control, process optimization, and quality improvement. However, conventional numerical methods suffer from limitations such as high computational costs and poor transferability. This study proposes a physics-informed neural network with dynamic learning rate (DLR-PINN) model, which integrates transfer learning to enable rapid prediction of 3D temperature fields and dimensions of molten pools across process parameters. Its validity is verified by a finite element method (FEM) calibrated via single-track DED experiments. Results show that DLR-PINN exhibits superior convergence and stability compared to traditional PINN. Combined with transfer learning, training efficiency is significantly enhanced, with a single prediction taking only 10 s. Using the FEM as the benchmark, it achieves a mean absolute percentage error (MAPE) of 0.53% for temperature prediction, and MAPE of 3.69%, 2.48%, and 6.96% for molten pool dimension predictions, respectively. Sensitivity analysis of process parameters reveals that scanning speed has a significantly greater regulatory effect on molten pool characteristics than laser power. Additionally, the temperature field of the flat-top heat source is more uniform than that of the Gaussian heat source, which is more conducive to improving printing quality and efficiency. Full article

Part segmentation can be used to overcome limitations of additive manufacturing (AM) processes such as Direct Energy Deposition of Metals (DED). In this case subparts of soft martensitic steel 1.4313 produced by conventional manufacturing (CM) and AM are joined by laser welding. This paper reports the difference in thermal conductivity of conventional and additive manufactured parts. The thermal conductivity was calculated from the thermal diffusivity, the specific heat, and the bulk density. Furthermore, the temperature was measured during welding and the microstructure analyzed. The far field temperature was measured using eight K-type thermocouples and the microstructure was analyzed by metallography and light microscopy. The results showed that the thermal conductivity of AM material is 8% lower and therefore the heating rate 5% lower compared to CM material. The lower thermal conductivity is explained in the literature by its higher dislocation density, unfavorable alloying element distribution and a lower rest austenite content. AM introduces structural complexity that hampers electron and phonon transport, thereby reducing the thermal conductivity despite similar base chemical compositions. The heat-affected zone is only clearly visible on the CM side due to carbide formation. In DED parts, it comes to different phases in non-equilibrium states, which complicates the identification of carbides and the HAZ. The findings are important for the design of hybrid components to improve the the joint integrity and functionality of hybrid parts. Full article

Melt electrowriting (MEW) is an advanced additive manufacturing technology that can produce micro- or nano-scale fibres, achieving accurate fibre deposition, and is suitable for manufacturing high-precision, miniature products. This review introduces the key principles and parameters that influence the performance of melt electrowriting and explores the current mathematical modelling under four stages: (1) heating and extrusion system, (2) formation of the Taylor cone, (3) formation and injection of the melt jet, and (4) deposition of the melt jet. In addition, current applications of melt electrowriting in emerging areas, such as tissue engineering, energy, filtration, and bioengineering, are introduced while discussing its combination with other additive manufacturing technologies. Finally, recent challenges, including production time, cost, and precision are covered, while the future research directions are to improve technology and introduce new materials. Full article

Borophene, a two-dimensional (2D) allotrope of boron, has emerged as a highly promising material owing to its exceptional mechanical strength, electronic conductivity, and diverse structural phases. Unlike graphene and other 2D materials, borophene exhibits inherent anisotropy, flexibility, and metallicity, offering unique opportunities for advanced nanotechnological applications. This review presents a comprehensive summary of recent progress in borophene synthesis methods, highlighting both bottom–up strategies such as chemical vapor deposition (CVD) and molecular beam epitaxy (MBE), and top–down approaches, including liquid-phase exfoliation and sonochemical techniques. A key challenge discussed is the stabilization of borophene’s polymorphs, as bulk boron’s non-layered structure complicates exfoliation. The influence of substrates and doping strategies on structural stability and phase control is also explored. Moreover, the intrinsic physicochemical properties of borophene, including its high flexibility, oxidation resistance, and anisotropic charge transport, were examined in relation to their implications for electronic, catalytic, and sensing devices. Particular attention was given to borophene’s performance in hydrogen storage and hydrogen evolution reactions (HERs), where functionalization with alkali and transition metals significantly enhances H₂ adsorption energy and storage capacity. Studies demonstrate that certain borophene–metal composites, such as Ti- or Li-decorated borophene, can achieve hydrogen storage capacities exceeding 10 wt.%, surpassing the U.S. Department of Energy targets for hydrogen storage materials. Despite these promising characteristics, large-scale synthesis, long-term stability, and integration into practical systems remain open challenges. This review identifies current research gaps and proposes future directions to facilitate the development of borophene-based energy solutions. The findings support borophene’s strong potential as a next-generation material for clean energy applications, particularly in hydrogen production and storage systems. Full article

Against the backdrop of accelerating global energy transition, developing high-performance energy-storage systems is crucial for achieving carbon neutrality. Traditional electrode materials are limited by a single densification storage mechanism and low conductivity, struggling to meet demands for high energy/power density and a long cycle life. Carbon/high-entropy alloy nanocomposites provide an innovative solution through multi-component synergistic effects and cross-scale structural design: the “cocktail effect” of high-entropy alloys confers excellent redox activity and structural stability, while the three-dimensional conductive network of the carbon skeleton enhances charge transfer efficiency. Together, they achieve synergistic enhancement via interfacial electron coupling, stress buffering, and dual storage mechanisms. This review systematically analyzes the charge storage/attenuation mechanisms and performance advantages of this composite material in diverse energy-storage devices (lithium-ion batteries, lithium-sulfur batteries, etc.), evaluates the characteristics and limitations of preparation techniques such as mechanical alloying and chemical vapor deposition, identifies five major challenges (including complex and costly synthesis, ambiguous interfacial interaction mechanisms, lagging theoretical research, performance-cost trade-offs, and slow industrialization processes), and prospectively proposes eight research directions (including multi-scale structural regulation and sustainable preparation technologies, etc.). Through interdisciplinary perspectives, this review aims to provide a theoretical foundation for deepening the understanding of carbon/high-entropy alloy composite energy-storage mechanisms and guiding industrial applications, thereby advancing breakthroughs in electrochemical energy-storage technology under the energy transition. Full article

Stainless steel is essential in high-performance industries due to its strength, corrosion resistance, and biocompatibility. However, conventional manufacturing methods limit material efficiency, design complexity, and customization. Additive manufacturing (AM) has emerged as a powerful alternative, enabling the production of stainless-steel components with complex geometries, tailored microstructures, and integrated functionalities. Key AM methodologies, including laser powder bed fusion (L-PBF), binder jetting, and directed energy deposition (DED), are evaluated for their effectiveness in producing stainless-steel components with optimal performance characteristics. This review highlights innovations in stainless-steel AM, focusing on microfabrication, multi-material approaches, and post-processing strategies such as heat treatment, hot isostatic pressing (HIP), and surface finishing. It also examines the impact of process parameters on microstructure, mechanical anisotropy, and defects. Emerging trends include AM-specific alloy design, functionally graded structures, and AI-based control. Applications span biomedical implants, micro-tooling, energy systems, and automotive parts, with emphasis on microfabrication for biomedical micromachines and precision microforming. Full article

Laser-Directed Energy Deposition (L-DED) is an additive manufacturing technique used for producing and repairing components, mainly for coating applications, depositing metal matrix composites such as cemented carbides, composed of hard metal carbides and a metallic binder. In this sense, this study evaluated the preparation of a ready-to-press WC-25Co powder as a reliable feedstock for L-DED process. This powder required pre-heat treatment studies to prevent fragmentation during powder feeding, due to the absence of metallurgical bonding between WC and Co particles. In the current study, the Taguchi methodology was used, varying laser power, powder feed rate, and scanning speed to reach an optimised deposition window. The best bead morphology resulted from 2400 W laser power, 11 mm/s scanning speed, and 9 g/min feed rate. Moreover, defects such as porosity and cracking were mitigated by applying a remelting strategy of 2400 W and 9 mm/s. Therefore, a perfect deposition is obtained using the optimised processing parameters. Microstructural analysis of the optimised deposited line revealed a fine structure, comprising columnar and equiaxed dendrites of complex carbides. The average hardness of the deposited WC-25Co powder on a AISI 1045 steel was 854 ± 37 HV0.2. These results demonstrate the potential of L-DED for processing high-performance cemented carbide coatings. Full article

The critical challenge of achieving precise geometric control in laser directed energy deposition (L-DED) of Inconel 690 for nuclear applications is addressed by this study. We established a data-driven optimization framework that reduces time-consuming trial-and-error experiments. A comprehensive process-geometry dataset was generated through full-factor experiments. Pearson correlation analysis revealed significant correlations: strong positive correlations between laser power and bead width (r = 0.82) and depth (r = 0.85), and between powder feed rate and height (r = 0.70). A hybrid machine learning model was subsequently developed. It used a Backpropagation Neural Network (BPNN) to achieve excellent prediction of width, height, and depth (R² ≤ 0.962). It also generated 100 uniformly distributed Pareto optimal process parameter sets via the Non-dominated Sorting Genetic Algorithm II (NSGA-II). Experimental validation confirmed the model’s high predictive accuracy—relative error ≤ 5% for width/depth, and a maximum relative error of 5.34% for height. This demonstrates the framework’s effectiveness for reliable multi-objective process optimization in high-precision deposition tasks. It also highlights its potential for use in nuclear component repair and other material systems. Full article

Numerous studies on specific cannabis compounds (cannabinoids and phenolic acids) have demonstrated their therapeutic potential, with their administration methods remaining a key research focus. Transdermal drug delivery (TDD) systems are gaining attention due to their advantages, such as painless administration, controlled release, direct absorption into the bloodstream, and its ability to bypass hepatic metabolism. The thin films obtained via pulsed laser deposition consist of micro- and nanoparticles capable of migrating through skin pores upon contact. This study investigates the interaction of phenolic compounds in hemp seeds with pulsed laser beams. The main goal is to achieve the ablation and deposition of these compounds as thin films suitable for TDD applications. The other key objective is optimizing laser energy to enhance the industrial feasibility of this method. Thin layers were deposited on glass and hemp fabric using dual pulsed laser (DPL) ablation on a compressed hemp seed target held in a stainless steel ring. The target was irradiated for 30 min with two synchronized pulsed laser beams, each with parameters of 30 mJ, 532 nm, pulse width of 10 ns, and a repetition rate of 10 Hz. Each beam had an angle of incidence with the target surface of 45°, and the angle between the two beams was also 45°. To improve laser absorption, two approaches were used: (1) HS-DPL/glass and HS-DPL/hemp fabric, in which a portion of the stainless steel ring was included in the irradiated area, and (2) HST-DPL/glass and HST-DPL/hemp fabric—hemp seeds were mixed with turmeric powder, which is known to improve laser interaction and biocompatibility. The FTIR and Micro-FTIR spectroscopy (ATR) performed on thin films compared to the target material confirmed the presence of hemp-derived phenolic compounds, including tetrahydrocannabinol (THC), cannabidiol (CBD), ferulic acid, and coumaric acid, along with other functional groups such as amides. The ATR spectra have been validated against Gaussian 6 numerical simulations. Scanning electron microscopy (SEM) and substance transfer tests revealed the microgranular structure of thin films. Through the analyzes carried out, the following were highlighted: spherical structures (0.3–2 μm) for HS-DPL/glass, HS-DPL/hemp fabric, HST-DPL/glass, and HST-DPL/hemp fabric; larger spherical structures (8–13 μm) for HS-DPL/glass and HST-DPL/glass; angular, amorphous-like structures (~3.5 μm) for HS-DPL/glass; and crystalline-like structures (0.6–1.3 μm) for HST-DPL/glass. Microparticle transfer from thin films on the hemp fabric to the filter paper at a human body temperature (37 °C) confirmed their suitability for TDD applications, aligning with the “whole plant medicine” or “entourage effect” concept. Granular, composite, thin films were successfully developed, capable of releasing microparticles upon contact with a surface whose temperature is 37 °C, specific to the human body. Each of the microparticles in the thin films obtained with the DPL technique contains phenolic compounds (cannabinoids and phenolic acids) comparable to those in hemp seeds, effectively acting as “microseeds.” The obtained films are viable for TDD applications, while the DPL technique ensures industrial scalability due to its low laser energy requirements. Full article

Additive manufacturing (AM) is an Industry 4.0 technology that assists or replaces the conventional manufacturing (CM) of complex geometries in various sectors, including transport, steel, aerospace, military, and architecture. The aim is to improve processes, reduce energy consumption, atmospheric emissions, and solid waste, and streamline stages while complying with the new environmental regulations. The main objective of this work was to carry out a cradle-to-gate Life Cycle Assessment (LCA), considering the raw material extraction, pre-processing, manufacturing, and post-processing stages, comparing two manufacturing methods for the same ER-90 metal flange part, conventional forging and wire and arc additive manufacturing (WAAM), all following the requirements and operations proposed by the ISO 14040/44 standard. WAAM is a Directed Energy Deposition (DED) technology that uses welding techniques to produce 3D objects with more complex geometries. Compared to the forging industry, which requires a lot of heat and kinetic energy in its metal part production stages, WAAM is a more sustainable and modern alternative because it does not require high temperatures and energy to produce the same parts. The environmental indicators compared in the process stages were energy consumption, greenhouse gas (GHG) emissions, and solid waste. The total energy consumption in AM was 18,846.61 MJ, the GHG emissions were 864.49 kgCO₂-eq, and the solid waste generated was 142.34 kg, which were 63.8 %, 90.5%, and 31.6% lower than the environmental indicators calculated for CM, respectively. Full article

The escalating challenges of greenhouse gas emissions, coupled with the severe depletion of oil reserves and the surging global energy demand, have emerged as critical concerns requiring urgent attention. Against this backdrop, biodiesel has been recognized as a viable alternative fuel for compression ignition (CI) engines. The primary objective of this research is to review the application of biodiesel in CI engines, with a focus on enhancing fuel properties and improving atomization performance. This article examines the spray and atomization characteristics of biodiesel fuels and conducts a comparative analysis with diesel fuel. The results show that biodiesel has a longer spray tip penetration, smaller spray cone angle, larger Sauter mean diameter (SMD) and faster droplet velocity due to its higher viscosity and surface tension. Blending with other fuels, such as ethanol, butanol, dimethyl ether (DME) and di-n-butyl ether, results in reduced viscosity and surface tension in these mixed fuels, representing a simple and effective approach for improving biodiesel atomization performance. A comprehensive analysis of spray and droplet impingement is also conducted. The findings reveal that biodiesel exhibits a higher probability of fuel–wall impingement, suggesting that future research should focus on two key directions: first, developing combined strategies to enhance impact-induced secondary atomization while minimizing fuel deposition; and second, investigating single-droplet impingement, specifically that of microscale biodiesel droplets and blended fuel droplets under real engine operating conditions. This paper also presents several advanced techniques, including air-assisted atomization, dual-fuel impingement, nano-biodiesel, and water-emulsified biodiesel, aimed at mitigating the atomization limitations of biodiesel, thereby facilitating the broader adoption of biodiesel in compression ignition engines. Full article

Chromium–aluminum nitride (CrAlN) coatings were deposited on polished H13 tool steel substrates using direct current (DC) magnetron sputtering. The Cr/Al composition in the target was varied by inserting either four or eight chromium (Cr) plugs into cavities machined into an aluminum (Al) plate target. Nitrogen was introduced as a reactive gas to facilitate the formation of the nitride phase. Coatings were deposited at substrate bias voltages of −30 V, −50 V, and −60 V to study the combined effects of composition and ion energy on coating properties. Compositional analysis of coatings deposited at a −50 V bias revealed Cr/Al ratios of approximately 0.8 and 1.7 for the 4- and 8-plug configurations, respectively. This increase in the Cr/Al ratio led to a 2.6-fold improvement in coating hardness. Coatings produced using the eight-Cr-plug target exhibited a nearly linear increase in hardness with increasing substrate bias voltage. Cross-sectional scanning electron microscopy revealed a uniform bilayer structure consisting of an approximately 0.5 µm metal interlayer beneath a 2–3 µm CrAlN coating. Surface morphology analysis indicated the presence of coarse microdroplets in coatings with the lower Cr/Al ratio. These microdroplets were significantly suppressed in coatings with higher Cr/Al content, especially at increased bias voltages. This suppression is likely due to enhanced ion bombardment associated with the increased Cr content, attributed to Cr’s relatively higher atomic mass compared to Al. Coatings with lower hardness exhibited greater scratch resistance, likely due to the influence of residual compressive stresses. The findings highlight the critical role of both Cr/Al content and substrate bias in tailoring the tribo-mechanical performance of PVD CrAlN coatings for wear-resistant applications. Full article

Directed Energy Deposition is an additive manufacturing subgroup that uses a laser beam to melt the wire or powder to create a melt pool. In the current study, a scientometric analysis has been carried out to analyze the contribution of countries, publication type analysis, distribution of publications over the years, keywords analysis, author analysis, cited journal, categories, institutes of publication, and report the practical implications. Firstly, the database was extracted from the Web of Science and then post-processed with CiteSpace 6.2.R4 and VOSviewer 1.6.20 software. Afterward, the associated results had been extracted and reported. It was found that China is the leader according to publication, followed by the USA and Germany, which mostly published their achievements in article and proceeding paper formats, which are increasing annually. According to the keywords, additive manufacturing, Laser Metal Deposition, and fabrication are the most commonly used. Based on the CiteSapce and VOSviewer results, Lin, Xin and Huang, Weidong are the authors with the highest publication rates. In addition, Additive Manufacturing, Materials & Design, and Materials Science and Engineering: A are the most cited journals, and regarding the categories, materials science, multidisciplinary, applied physics, and manufacturing engineering are the most commonly used DED processes. Northwestern Polytechnical University, Fraunhofer Gesellschaft, and the United States Department of Energy (DOE) have performed the most research in the field of DED. Full article

The conventional manufacturing of refractory complex concentrated alloys (RCCAs) for high-temperature applications is complicated, particularly when material costs and high melting points of the materials processed are considered. Additive manufacturing (AM) could provide an effective alternative. However, the extreme temperatures involved represent significant challenges for manufacturing defect-free alloys using this approach. To address this issue, we investigated the preparation of a CrNbTiZr quaternary complex concentrated alloy from an equimolar blend of elemental powders using commercially available powder-blown L-DED technology. Initially, the alloys exhibited some defects owing to the internal stress caused by the temperature gradients. This was subsequently resolved by optimizing the deposition strategy. SEM, XRD and EDS were used to analyze the alloy in the as-deposited condition, revealing a BCC phase and a secondary Laves phase. Furthermore, Vickers hardness testing demonstrated a correlation between the hardness and the volume fraction of the Laves phase. Finally, successfully performed compression tests confirmed that the prepared material exhibits high-temperature strength and therefore is promising for high-temperature application under extreme conditions. Full article

Metal–Organic Frameworks (MOFs) have emerged as advanced porous crystalline materials due to their highly ordered structures, ultra-high surface areas, fine-tunable pore sizes, and massive chemical diversity. These features, arising from the coordination between an almost unlimited number of metal ions/clusters and organic linkers, have resulted in significant interest in MOFs for applications in gas storage, catalysis, sensing, energy, and biomedicine. Beyond their stand-alone properties and applications, recent research has increasingly explored the integration of MOFs with other substrates, particularly electrodes, polymeric thin films, and glass surfaces, to create synergistic effects that enhance material performance and broaden application potential. Coating MOFs onto these substrates can yield significant benefits, including, but not limited to, improved sensitivity and selectivity in electrochemical sensors, enhanced mechanical and separation properties in membranes, and multifunctional coatings for optical and environmental applications. This review provides a comprehensive and up-to-date summary of recent advances (primarily from the past 3–5 years) in MOF coating techniques, including layer-by-layer assembly, in situ growth, and electrochemical deposition. This is followed by a discussion of the representative applications arising from MOF-substrate coating and an outline of key challenges and future directions in this rapidly evolving field. This article aims to serve as a focused reference point for researchers interested in both fundamental strategies and applied developments in MOF surface coatings. Full article