Melting Process Research Articles

Self-Reinforced Biocomposites Made from Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV): An Innovative Approach to Sustainable Packaging Production through Melt Processing

Self-Reinforced Biocomposites Made from Poly(3-hydroxybutyrate-<i>co</i>-3-hydroxyvalerate) (PHBV): An Innovative Approach to Sustainable Packaging Production through Melt Processing

Melt pool super solution reconstruction based on dual path deep learning for laser powder bed fusion monitoring

Melt pool monitoring in laser powder bed fusion (L-PBF) is an important foundation for process control and melting dynamics research. However, due to hardware limitations and the intense metallurgical phenomena during the melting process, the quality of the melt pool monitoring images cannot be guaranteed. This paper proposes a deep learning-based melt pool image super-resolution (SR) reconstruction method based on the particularity of melt pool images. It is an innovative dual-path structure. The first branch utilizes residual-in-residual structures and the efficient channel attention-Net attention mechanism to achieve the adaptive feature extraction of high-frequency information, thereby capturing effective melt pool boundary information. The second branch uses the U-Net structure to address the low utilization of overall characteristics of the melt pool in the chain-based SR network. In addition to the universal peak signal-to-noise ratio and structural similarity index measure metrics, the reconstruction accuracy of melt pool contour features is used to measure model performance, which intuitively reflects the significance of this work for melt pool monitoring. The results demonstrate that the proposed SR reconstruction method enhances the resolution and clarity of melt pool images. Furthermore, SR reconstruction of the melt pool effectively reduces errors in extracting melt pool features. This method provides a network paradigm for high-precision L-PBF monitoring. It integrates important boundary information and overall morphology features of the melt pool through a dual path structure, thereby achieving reliable SR reconstruction. This research will contribute to low-cost in situ monitoring of L-PBF and subsequent process control.

Laser melting, evaporation, and fragmentation of nanoparticles: Experiments, modeling, and applications

This review examines the processes of laser heating, melting, evaporation, fragmentation, and breakdown of metal nanoparticles, as well as the dependences and values of the threshold laser parameters that initiate these processes. Literature results are analyzed from experimental studies of these processes with gold, silver, and other nanoparticles, including laser surface melting and evaporation of nanoparticles and Coulomb fragmentation of nanoparticles by ultrashort laser pulses. A theoretical model and description of the thermal mechanisms of mentioned processes with metal (solid) nanoparticles in a liquid (solid) medium, initiated by the action of laser pulses with the threshold fluences, are presented. Comparison of the obtained results with experimental data confirms the accuracy of the model and makes it possible to use them to evaluate the parameters of laser thermal processing of nanoparticles. Applications of the processes include the laser melting, reshaping, and fragmentation of nanoparticles, the formation of nanostructures and nanonetworks, the laser processing of nanoparticles located on substrates, and their cladding on surfaces in various laser nanotechnologies. The use of laser ignition, combustion, and incandescence of nanoparticles is discussed, as is the use of nanoparticle-triggered laser breakdown for spectroscopy. These laser processes are used in photothermal nanotechnologies, nanoenergy, laser processing of nanoparticles, nonlinear optical devices, high-temperature material science, etc. In general, this review presents a modern picture of the state of laser technology and high-temperature processes with nanoparticles and their applications, being focused on the latest publications with an emphasis on recent results from 2021–2024.

The influence of compounder screw speed on melt processing of thermoplastic polyurethane

The influence of compounder screw speed on melt processing of thermoplastic polyurethane

A General Sol-Gel Route to Fabricate Large-Area Highly-Ordered Metal Oxide Arrays Toward High-Performance Zinc-Air Batteries.

A universal method is demonstrated for the fabrication of large-area highly ordered microporous arrayed metal oxides based on a high-quality self-assembly opal template combined with a sucrose-assisted sol-gel technique. Sucrose as a chelating agent optimizes precursor infiltration and regulates both oxide formation and the melting process of polystyrene templates, thus preventing crack formation during infiltration and calcination. As a result, over 20 metal element-based 3DOM oxides with arbitrary compositions are successfully prepared. Therein, a champion electrocatalyst RuCoOx-IO exhibits outstanding bifunctional oxygen activity with an ultra-narrow oxygen potential gap of 0.598V, and the Zn-air batteries based on RuCoOx-IO air cathode operates for 1380h under fast-charging cycling (50mA cm-2), and reaches a high energy efficiency of 69.5% in discharge-charge cycling. In situ spectroscopy characterizations and density functional theory reveal that the rational construction of Ru─O─Co heterointerface with decoupled multi-active sites and mutual coupling of RuO2 and Co3O4 facilitate interfacial electron transfer, leading to an optimized d-band centers of active Ru/Co and a weakened spin interaction between oxygen intermediates and Co sites, so as to enhance the adsorption ability of *OOH on interfacial Co sites for fast ORR kinetics while favoring the desorption of oxygen intermediates on interfacial Ru during OER.

Radiogenic heat production provides a thermal threshold for Archean cratonization process

A striking feature of the Yilgarn craton at the current erosional level is an abundance of late K-rich granites with radiogenic heat production elevated far above global crustal averages. Extrapolated back in time, the total thickness and contribution to crustal heat production and heat flow from these granites were greater, implying that the deeper crustal sources must also have had elevated radiogenic heat production. Through back-calculated and time-integrated one-dimensional thermal modeling underpinned by geological and geochemical constraints for the model crustal columns, we find that elevated radiogenic heat production provided a significant internal driver for prolonged crustal melting and eventual cratonization of the Yilgarn craton. Our results show that elevated thermal gradients driven by high heat production thermally primed the mid- and deep crust at or above the threshold for large-volume partial melting over long periods of time, as evidenced in the magmatic rock record. This would have been amplified by any additional heat that may have been provided by the mantle melting processes that punctuated the geological history. Over time, advective movement of progressively more radiogenic heat production to the shallower crust would have resulted in two complementary outcomes: progressively refractory deep crust and long-term cooling. The widespread granite “bloom” at 2650−2600 Ma records the final time at which the crust was fertile enough to melt in large volumes and the thermal gradient was hot enough to intersect the solidus. The magnitude of radiogenic heat production in the Yilgarn craton has been underestimated in previous studies, resulting in an underappreciation of the importance of its contribution to internal drivers of magmatism and ultimately cratonization.

Application investigations of force fields for molecular dynamic simulations of medical aluminum particles

The phase transition of metals is a research hotspot in molecular dynamic (MD) simulation. With the increase of the development of MD, different force fields with different requirements have emerged, which helps to select the appropriate force field and also increases the difficulty of selection. In addition, previous studies have been affected by particle size, which affects the melting point accuracy. MD simulation of the melting and condensing behavior of Aluminum (Al) particles was carried out by using EAM force fields from different sources. The thermal behavior of phase transition was studied by means of potential energy, specific heat, MSD, FCC lattice number, etc. The melting and condensation process of 2–10[Formula: see text]nm cubic without boundary under the NPT system was simulated, and the steady-state simulation was discussed by means of an isometric temperature point. It is proved that the borderless simulation can completely eliminate the boundary effect. The parameter setting of efficient use of EAM is widely discussed by using this method, and the effectiveness of the EAM force field is compared, so as to improve the efficiency of scholars engaged in related research and avoid the difficult choice of force field files. The results show that the borderless simulation has quite high advantages in terms of phase transition potential energy and melting point, while the current EAM force field is inherently deficient in this kind of discussion, and the development of new force field is urgent.

Laser‐Based Closed‐Loop Controlled Heat Treatment for Residual Stress Relief of Additively Manufactured AlSi10Mg Components

In laser powder bed fusion of metals small melt pools with extremely short solidification times and steep temperature gradients to the surrounding material exist due to the layer‐wise and selective melting process with small areas of energy input compared to the cooler, solid ambient material. This causes high thermally induced residual stresses (RS), which can lead to the immediate rejection of the component due to critical part deformation and inhomogeneous mechanical properties under load. To prevent this, furnace‐based stress relief heat treatments are commonly applied before cutting‐off the part from the built platform. In this study a novel closed‐loop controlled laser‐based heat treatment using temperature feedback through inline pyrometer measurement is investigated, enabling a fast and highly efficient postprocess stress relief. Therefore, a laser beam is guided by a scanner optics in a meandering pattern over the top surface of AlSi10Mg cantilever specimens. It enables a decrease of near‐surface RS from 158 to 5 N mm−2, resulting in a reduction of displacement by over 90% at material affecting depths up to 3 mm and area rates of 8 to 163 mm2 s−1.

Controlling the heating wall temperature during melting via electric field

Thermal energy storage technology utilizing phase change materials (PCMs) is extensively applied in thermal management and energy storage. The inclination angle (θ) plays a critical factor in the phase change melting processes in practical implementations. However, the precise experimental velocity fields of liquid PCM and the impact of active regulation technology on the heating wall temperature at various angles remain unclear. Herein, a transparent melting experiment platform was established to measure velocity, and adjust θ and manipulate input electric voltage. Results from Particle Image Velocimetry indicated that the installation angle significantly impacts natural convection in the convection-dominated melting regime. The liquid fraction decreased from 73.5 % (when θ = 90°) to 54.4 % (when θ = 150°) due to reduced thermal energy absorption, as input energy was stored as sensible heat on the copper wall. The electrohydrodynamic (EHD) effect mitigated thermal resistance between the heater and the melt front, increasing melt thickness. EHD flow exhibited limited ability to regulate heating wall temperature under strong natural convection, with a 6.5 % decrease observed under +20 kV conditions. As natural convection rates decreased, the decrease rate of heating wall temperature increased to 10.7 %. The EHD effect demonstrated a heightened capability in enhancing heat transfer melting with increasing θ, leading to an increase in temperature difference from 3.3 °C to 5.3 °C under the +15 kV input voltage. These findings suggest that the electric field is an efficacious method for controlling the heating wall temperature at different inclination angles during the melting process.

Biodegradation profile and soil microbiota interactions of poly(vinyl alcohol)/starch-based fertilizers.

Enhanced efficiency fertilizers (EEFs) are critical for sustainable agriculture, providing essential nutrients while minimizing environmental impact. However, developing EEFs that effectively degrade after use remains a significant challenge. This study investigates the biodegradation and nutrient release profiles of EEFs composed of poly(vinyl alcohol) (PVA) and starch-nutrient microspheres. EEFs were developed using a dual-layered approach: spray drying to create starch-nutrient microspheres, followed by melt processing with PVA to form pastilles. A 100-day soil biodegradation test monitored CO2 release as an indicator of microbial activity and material degradation. Comprehensive analyses, including chemical (FTIR), thermal (DSC), and morphological (SEM) assessments, were conducted. The increased CO band intensity (~1640 cm-1) after biodegradation indicated early stages of PVA degradation, accompanied by a rise in the glass transition temperature (Tg). Thermal analysis revealed nutrient release, as evidenced by a decrease in KNO3 peaks. Starch-based EEFs enhanced CO2 release and mycelial coverage, suggesting that starch-containing materials facilitated PVA degradation by improving microbial adhesion. This study underscores the potential of biodegradable EEFs to enhance soil health and reduce pollution, thereby contributing significantly to sustainable agriculture.

Interaction of Kerguelen and Amsterdam-St. Paul dual hotspots with Southeast Indian Ridge

We investigated the influence of the Kerguelen (K) and Amsterdam-St. Paul (ASP) dual hotspots on mantle evolution and crustal accretion in the eastern Indian Ocean. Using surface plate motion constraints from the global plate reconstruction model and the 3-D mantle convection code (ASPECT), we illustrated detailed processes of mantle upwelling, melting, and crustal accretion in the ridge-dual hotspot system. Model results demonstrate that the K hotspot significantly increased the mantle temperature over a wide region of over 1,500 km, leading to a 1–2 km increase in average crustal thickness along the entire Southeast Indian Ridge (SEIR). Only ridge-dual hotspot interaction models can explain key crustal variations along the SEIR. Gravity analysis revealed the K hotspot's long-term interaction with nearby ridges formed significant crustal anomalies, while the ASP hotspot's 10 Myr interaction with SEIR created localized anomalies. The distance between the ridge and hotspot, as well as plume flux, are key factors controlling the strength of ridge-hotspot interaction. The K hotspot, with its relatively higher plume flux, has double the influence distance of the ASP hotspot. Furthermore, our models indicate a possible direct interaction between the K and ASP hotspots, resulting in the ASP plume materials flowing towards the K plume.

Enhancing heat transfer efficiency in solar storage devices using eddy current structures and vibrations

This study introduces a novel phase change material (PCM)-based solar energy storage system integrating Tesla valve-inspired eddy current structures and mechanical vibrations to enhance thermal performance. By systematically optimizing the geometric design and vibration parameters, a 90°shunt angle was identified as the most effective configuration, achieving a significant 59.9% reduction in PCM melting time and completing the melting process in just 178 s. This superior performance was attributed to the generation of strong eddy currents, which disrupted the thermal boundary layer and enhanced heat transfer between the heat transfer fluid (HTF) and PCM. Mechanical vibrations (0.0003 m amplitude and 100 Hz frequency) further improved performance, particularly for shunt angles of 30°and 60°, where melting times were reduced by 13.4% and 13.36%, respectively, demonstrating the synergistic effects of geometry and vibration.The impact of natural convection was evaluated across a range of Rayleigh numbers (11,400 to 1,140,000), revealing that higher Rayleigh numbers enhanced heat transfer, especially for the 90°configuration. In contrast, shunt angles exceeding 90°showed reduced efficiency due to the thickening of boundary layers. Comparative analysis with existing heat transfer enhancement studies demonstrated the superior performance of the proposed system, which achieved greater reductions in melting time compared to designs using fin structures or optimized inclinations. This research provides valuable insights into the development of high-performance, scalable, and sustainable solar energy storage systems, bridging the gap between laboratory innovation and practical application.

Electrocatalytic trends of different Cantor entropy alloys. for alkaline and acidic hydrogen-evolution reactions

Medium- and high-entropy alloys (MEAs and HEAs) are the basis of unique electrocatalysts for hydrogen-evolution reactions (HERs) due to their tunable chemical compositions and microstructures. Here, various Cantor MEAs (CoFeNi, CoFeNiMn, CoFeNiCr) and a HEA (CoFeNiMnCr) made up of affordable non-noble transitional metals with different structures (primary matrix and secondary phases, grain sizes, lattice parameters) were successfully synthesized with an inert-gas melting process. A close correlation was established between their physicochemical properties (elemental composition, microstructure, crystal structure) and the hydrogen-binding ability of the elements in the alloy on the electrocatalytic HER activity and stability in alkaline and acidic media. Advanced performances of electrocatalysts toward HERs were revealed in a specially designed electrochemical cell. Effectively identifying these electrocatalytic trends lays the groundwork for the strategic design of multi-component alloy electrocatalysts for practical HERs.

Investigation of enhanced PCM heat sink design under extreme thermal conditions for high-heat-generating electronic devices

In this study, a novel enhanced phase change material (PCM) heat sink design is proposed to improve energy efficiency and maintain quiet operation under extreme thermal conditions for high-heat-generating electronic devices. To overcome the thermal conductivity and heat transfer limitations of the PCM heat sinks, fins, metal foams, and nanoparticles were integrated. A simulation model for the PCM heat sink was developed based on experiments. The thermal performances of different PCM heat sinks were comprehensively evaluated and compared through an in-depth analysis of their thermal behaviors. Consequently, at the heat flux of 20 kW·m−2, a proposed nano-enhanced PCM heat sink with fins and metal foams reduces the surface temperature of high-heat-generating electronic devices by 40.0 K during pre-heating process and maintains a minimum temperature of 54.47°C, decreasing the temperature by 41.4 K during melting process compared to the PCM heat sink without thermal conductivity enhancers. Furthermore, the proposed PCM heat sink exhibited the longest critical duration, approximately 26 times longer than that of a PCM heat sink without thermal conductivity enhancers. Additionally, within the critical temperature range, employing a PCM with a suitable melting temperature and metal foam parameters is advantageous for the thermal management of high-heat-generating electronic devices.

Investigation of the influence of the air layer on the phase change material melting process inside a hemicylindrical enclosure: A numerical approach

The rapid growth in energy consumption and the associated difficulties have made thermal energy storage processes using phase change materials (PCMs) a prominent subject of study and development in the last century. The exceptional thermo-dynamic characteristics of this material enable it to accumulate substantial quantities of heat within very limited spaces. The present work involved a numerical investigation of the impact of the air layer on the melting time of paraffin wax RT42 (PCM) within an enclosure with a hemicylinder shape. The enthalpy-porosity relationship is analyzed numerically using ANSYS/FLUENT 16 software. The study included three distinct scenarios that examined the thermal and mass characteristics of paraffin wax within a hemicylindrical enclosure, with the curving wall of the enclosure being thermally insulated. The initial scenario lacked any air layer on the heated vertical wall, whereas the subsequent scenario had an air layer measuring 1 mm thick on the same wall. The third scenario contained an air layer measuring 2 mm within the same wall. The findings indicated that including a 1 mm thick air layer would result in a 125% extended complete melting time of paraffin wax. Similarly, including a 2 mm thick air layer would lead to a 225% rise in the complete melting time of paraffin wax. The presented outcome demonstrates the impact of ambient air on thermal storage units during the charging procedure.

Investigation of the Arrangement of Aluminum Fins on the Thermal Behavior of Lauric Acid as a Phase Change Material in a Two-pipe Heat Exchanger by CFD Simulation

BackgroundPhase change material (PCM) thermal storage systems store more thermal energy per unit volume than sensible heat storage systems. PCMs offer a potential solution to reduce energy consumption in various thermal engineering applications. This study aimed to examine how fin arrangement affected the thermal efficiency and melting time of PCMs. MethodsA two-dimensional numerical analysis of the melting process of lauric acid in a heat exchanger featuring two pipelines and fins was conducted using CFD simulation. In most previous investigations, the heat transfer fluid was a single-phase liquid. An enthalpy-porosity technique was used to model the solid and liquid phases of PCM. The governing equations were solved using the commercial software ANSYS Fluent 2021, and the pressure and velocity equations were coupled using the SIMPLE algorithm. Significant FindingsThe best model among the 13 tested was Model 5, which featured 6 fins and a consistent angle of 60 degrees. For Model 5, the melting time was 1818.3 seconds. Due to sensible heating, the fin's temperature (Temp) rose gradually from 300 K to 318 K. Temp then gradually increased as the PCM melted in the phase transition zone between 316.5 K and 321.2 K. Once the phase transition was complete, the PCM's Temp steadily rose from 324 K to 340 K. In Model 5, the inner wall Temp and the maximum Temp of the PCM were closest, at 327.34 K and 333.55 K, respectively. The thermal shock between the PCM and the ambient Temp caused a peak heat flux at the beginning of the PCM loading process.

Bio-functional niobium-based metallic biomaterials: exploring their physicomechanical properties, biological significance, and implant applications.

The significance of biomedical applications of bio-functional niobium (Nb)-based metallic biomaterials is underscored by their potential utilization in implant application. Nb-based metallic materials present reliable physicomechanical and biological properties, thus represent materials highly suitable for implant application. This review provides an overview on the advances of pure niobium and Nb-based metallic materials as implant materials over the past 20 years, and highlights the advantages of Nb-based metallic biomaterials for implant application in terms of their physicomechanical properties, corrosion resistance in biological media, magnetic resonance imaging (MRI) compatibility, cell compatibility, blood compatibility, osteogenesis, and bioactivity. An introduction is provided for the production and processing techniques for Nb-based metallic biomaterials, including traditional melting processes like vacuum arc remelting, additive manufacturing like selective laser melting (SLM), electron beam melting (EBM), spark plasma sintering (SPS), and severe plastic deformation like equal channel angular pressing (ECAP), multi-axial forging (MAF), high pressure torsion (HPT), as well as their physicomechanical properties and implant application. Also suggested are the critical issues, challenges, and prospects in the further development of Nb-based metallic biomaterials for implant applications. STATEMENT OF SIGNIFICANCE: Nb-based biomaterials have gained significant interest for bioimplantable scaffolds because of their appropriate mechanical characteristics and biocompatibility. No prior work has been published specifically reviewing bio-functional Nb-based biomaterials for exploring their physicomechanical properties, biological significance, and implant applications. This review provides an overview on the advances of niobium and Nb-based materials as implant materials over the past 20 years, and highlights the advantages of Nb-based biomaterials for implant application. An introduction is provided for the production and processing techniques for Nb-based biomaterials, as well as their physicomechanical properties and implant application. Also suggested are the critical issues, challenges, and prospects in the further development of Nb-based biomaterials for implant applications.

Heterogeneous to Homogeneous Melting Transition Observed During a Single Process

The melting mechanism at medium heating rates is unclear, owing to the lack of accurate characterizations of structural changes in poly-directional melting conditions. Here, a particular multilayered nanostructure was selected to control the propagation of melting in a single direction. We predicted the heterogeneous to homogeneous melting (HeM to HoM) transition during a single melting process at medium heating rates of 10–400 K/ps by molecular dynamics (MD) simulations, without a change in heating rates. The information on structural changes for the HeM to HoM transition, including the loss of crystallinity and long- and short-range order, are clearly provided by both a single direction and the radial distribution functions. These results contribute to a more comprehensive understanding of the HeM to HoM transition induced by heating rates.

Characteristics of cast Ti53.3-xNb10Zr10Ni10Co10Fe6.7Bx compositionally complex alloys

In the current investigation, elemental boron was added to form a series of Ti53.3-xNb10Zr10Ni10Co10Fe6.7Bx Compositionally Complex Alloys (CCAs). Alloying was done via vacuum arc melting in amounts of 0.0, 5.3, and 10.6 at.%. From the thermodynamic parameters, adding B to the base alloy increased the system’s entropy. The microstructure of the prepared CCAs was characterized using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction (XRD). The mechanical properties of CCAs as related to microstructure were assessed. According to XRD results, B-based intermetallic phases were obtained in the prepared CCAs, which were binary as Ti3B4 and ZrB2 and ternary as FeNbB and Nb3Co4B7. These intermetallic phases notably provided strengthening effects to the B-added alloys. Ti48Nb10Zr10Ni10Co10Fe6.7B5.3 CCA showed the most homogenous microstructure obtained by the arc melting process. Adding B increased Young’s modulus from 141 GPa (without B) to 195 GPa and 260 GPa with 5.3 and 10.6 at.%B, respectively. Hardness also increased from 502 to 606 HV with 5.3 at.% B and to 648 HV with 10.6 at.%B. Accordingly, the wear resistance increased with B addition where 10.6 at.%B sample showed the lowest wear rate among the other conditions. However, 5.3 at.% B was nominated as the optimum addition amount due to its notable microstructure homogeneity.

Influence of ambient pressure on laser beam melting of lunar regolith simulant

The construction of a lunar base requires a huge amount of material, which cannot be entirely transported from Earth. Therefore, technologies are needed to build with locally available resources, such as the lunar regolith. One approach is to directly melt the lunar regolith on the surface and under the vacuum condition of the Moon, using laser radiation. In this article, a lunar regolith simulant is laser beam melted to two-dimensional single-layer-structures using different ambient pressures from 0.05 mbar to 2000 mbar, laser process parameters from 60 W to 100 W laser power, and 1 mm s−1 to 3 mm s−1 feed rates. Additionally, the influence of the ambient gas was investigated using argon as an air alternative. The results show that the ambient pressure on the Moon is not negligible when studying the melting processes of lunar regolith on Earth. With decreasing ambient pressure, the appearance of the melted regolith simulant varies from a shiny to a matt surface. At the highest laser energy density, the thickness of a single-layer increases from 2.6 ± 0.4 mm to 5.3 ± 0.3 mm and the porosity of the melted regolith increases from 17.2 % to 52.2 % with decreasing ambient pressure. Additionally, mechanical properties are determined using 3-point bending tests. The maximum bending strength decreases by 60 % with the increased ambient pressure from 10 mbar to 2000 mbar. Consequently, the development of in-situ resource utilization technologies, which process the lunar regolith directly on the lunar surface, must consider the ambient pressure on the Moon. Otherwise, the processes will not work as expected from the experiments in Earth-based laboratories.