Search Results (1,553)

This study investigates the influence of PLA flowability and talc content on the performance of compostable thermoplastic starch/poly(butylene succinate) (TPS/PBS)-based systems for rigid applications. Different PLA grades with varying melt flow index (PLA23, PLA8 and PLA70) and talc contents (0, 5 and 10 wt%) were incorporated. Twelve formulations were compounded by twin-screw extrusion and processed by injection moulding. FTIR confirmed the coexistence of TPS, PBS and PLA phases without evidence of chemical interactions. Morphological analysis showed that PLA flowability plays a key role in phase distribution, with higher-flow PLA promoting improved dispersion and interfacial adhesion, while talc addition (5 and 10 wt%) increased structural heterogeneity; at higher loadings, particularly, DSC analysis revealed that talc acted as a nucleating agent for the PBS phase, increasing crystallisation temperatures from approximately 73 °C to 81 °C depending on formulation. Mechanical results showed that Young’s modulus increased from approximately 1.4 GPa to 2.7 GPa with decreasing PLA flowability and increasing talc content. Formulations containing low-flow PLA reached tensile strengths close to 32 MPa, although elongation at break decreased to values near 2%. In contrast, high-flow PLA formulations exhibited a more balanced mechanical response, with elongation values up to approximately 8%, associated with improved phase dispersion. Hybrid PLA systems showed intermediate behaviour, reaching elongations up to 22% while maintaining modulus values around 1.8 GPa. Talc provided additional reinforcement but reduced deformation capacity. HDT values remained relatively constant, indicating limited improvement in thermomechanical resistance despite increased stiffness. These results demonstrate that the combined control of PLA molecular characteristics and talc content enables tuning of the mechanical and thermomechanical performance of TPS/PBS/PLA/talc systems for rigid packaging applications. Full article

Rising demand for high-performance battery thermal management systems (BTMSs) has rendered single-mode cooling insufficient for advanced lithium-ion batteries (LIBs) in new energy vehicles (NEVs), particularly under high discharge rates. This study proposes a synergistic hybrid BTMS integrating composite phase-change material (CPCM)–aluminum foam with liquid cooling to enhance thermal regulation of cylindrical battery modules under 5 C discharge conditions. Multiple liquid-cooled plate (LCP) configurations, including serpentine, straight, and leaf-shaped designs, together with different flow channel topologies (FCTs), were systematically investigated and optimized. The effects of coolant flow speed (CFS) and ambient temperature were also analyzed. Results indicate that the optimized leaf-shaped LCP with FCT #2 delivers superior performance, limiting the maximum temperature to 309.98 K, reducing temperature difference by 7.6%, and decreasing pressure drop by 88.79% compared to the serpentine configuration. Increasing CFS improves heat dissipation and delays PCM melting, although it raises pressure losses. Furthermore, the proposed system maintains a cell-to-cell temperature difference below 0.51 K, indicating excellent thermal uniformity. Compared to a CPCM-only system, the hybrid BTMS reduces peak temperature by 8.81 K under elevated ambient conditions (309.15 K), demonstrating strong potential for reliable and efficient thermal management in demanding operating environments. Full article

This study established a refined, distributed SWAT modeling framework that integrates elevation-band and snowmelt modules to reconstruct the alpine hydrological and sediment cycles of the Koshi River Basin (KRB) over the period 1990–2024, with climate scenarios constructed using the delta change approach. The KRB, a major transboundary watershed traversing China, Nepal, and India, was selected owing to its critical hydro-climatic role under the destabilizing “Asian Water Tower”; it generates substantial sediment yield, hosts the densest concentration of hydropower potential within the Ganges system, and spans an extreme vertical gradient from Mount Everest to the southern alluvial plains. Results reveal accelerated warming at a rate of 0.21 °C per decade and an overall warming–wetting trend, punctuated by an abrupt interdecadal shift around 2015. Precipitation dominated interannual streamflow variability, with enhanced rainfall triggering basin-wide sediment surges that overwhelmed the natural buffering capacity of the land surface. Conversely, rising temperatures intensified actual evapotranspiration, markedly depleting soil water and reducing total water yield and monsoon runoff, although sustained snow and glacier melt effectively elevated the dry-season low-flow baseline. The integrated climate forcing reshaped the disparity between hydrological extremes, imposing severe seasonal eco-hydrological stress that manifested as a pre-monsoon deficit in terrestrial green water and acute summer sediment outbursts for aquatic habitats. Furthermore, the flood regime exhibited an altered distribution, with mid-to-high frequency floods enhanced while low-frequency extreme flood peaks declined. The hydro-sedimentological regime consequently exhibits pronounced nonlinear responses to climate change, providing a critical, threshold-based scientific foundation for adaptive transboundary water resource management. Full article

Welding aluminum (Al) to titanium (Ti) is particularly challenging because of the large differences in their melting points and the tendency to form cavities and brittle intermetallic compounds. Such issues can be mitigated in friction stir welding (FSW) by understanding the underlying mechanisms of microstructural evolution and tensile fracture behavior. In the present study, FSW was carried out on commercially pure Al and commercially pure Ti. X-ray micro-computed tomography results show that the distribution of Ti fragments depends on their morphology, with fine particles (volume 10³–10⁴ µm³) being distributed homogeneously, while large flakes (10⁷–10⁹ µm³) are concentrated near the joint interface. A three-dimensional analysis of Ti fragment distribution was performed to clarify material flow and particle dispersion within the weld nugget. EDS (Energy-Dispersive Spectroscopy) and EPMA (Electron Probe Microanalysis) composition mapping confirmed the formation of AlTi and Al₃Ti intermetallic phases, with Al₃Ti as the dominant phase (consistent with its lower Gibbs free energy of formation). Because Al is the primary element in the matrix and undergoes the highest degree of deformation, its microstructural evolution in Al was examined using Electron Backscatter Diffraction (EBSD). Grain refinement in Al was attributed to continuous dynamic recrystallization (CDRX). Mechanical mixing and intermetallic formation increased the hardness of the weld, while the tensile response corresponded to a joint efficiency of approximately 77%, alone with an 11% improvement in elongation over base Al. The study further establishes a correlation among Ti particle distribution, local microstructural evolution, and the tensile response of the joint. Fractographic analysis indicates a bimodal fracture mechanism, and failure occurred away from the joint interface, indicating a strong joint. To interpret this behavior, a spring-based model was proposed to relate the fracture location and tensile deformation to the spatial variation in microstructure across the welded zones. This approach provides a conceptual framework that is extendable to other dissimilar material systems with spatially varying microstructures. Full article

The present work proposes a phase change material-based defrosting system (PCM-DS) for vapor compression refrigeration systems (VCRSs). The primary objective is to determine the optimal PCM mass and refrigerant mass flow rate required to melt 1 kg of accumulated evaporator ice. A steady-state macroscopic thermodynamic model, governed by global energy balances and driven by experimental boundary conditions, evaluates the VCRS in both cooling and defrosting operating modes. The PCM-DS is not installed on the experimental setup. The latter is used to obtain experimental data to be used as inputs in the steady-state model. Among the three candidates investigated (OM42, OM46, OM48), OM42 was selected for minimizing system mass and volume constraints. Results demonstrate that integrating the PCM-DS induces only a 3% reduction in the theoretical coefficient of performance (COP) compared with a 5.6% reduction in the case of using the electric heater defrosting (EHD). The core innovation of this work involves proposing and evaluating three distinct energy storage management strategies: unique superheating, unique bypass, and intermittent bypass. The results show that the highest COP is obtained for unique superheating (2.93), followed by unique bypass (2.82) and intermittent bypass (2.81). The work conducted proves the theoretical feasibility of such PCM-DS. Full article

Auxetic metamaterials exhibit unique mechanical behavior due to their negative Poisson’s ratio, but reliable determination of their effective elastic properties remains challenging. In this study, an experimental–numerical approach is proposed to characterize additively manufactured polylactic acid (PLA)-based auxetic sandwich structures. Material properties were first assessed using tensile testing, melt flow rate/volume rate (MFR/MVR) measurements, Fourier-transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), dilatometry, and nanoindentation, revealing stable mechanical behavior, good processability, and slight increases in crystallinity induced by the printing process. Impulse excitation technique (IET) measurements provided highly reproducible resonant frequencies, demonstrating a strong dependence on core geometry and orientation. However, classical ASTM-based evaluation yielded non-physical elastic properties, highlighting its limitations for architected metamaterials. Finite element modal analyses, combined with inverse parameter identification, enabled the determination of effective elastic properties using a transversely isotropic homogenized model. This approach significantly improved the agreement between experimental and numerical results. The findings revealed pronounced anisotropy and orientation-dependent auxetic behavior, including a negative Poisson’s ratio for specific configurations. The proposed methodology provides a suitable framework for the reliable characterization and design of complex metamaterials. Full article

The influence of internal substrate geometry on thermal stability during Laser Directed Energy Deposition Repair (DED-R) remains insufficiently understood, particularly for components containing internal cavities and cooling channels. This study investigates the thermal response of solid (Alpha), blind-hole (Bravo), and channeled (Charlie) AISI 316L substrates using dual infrared thermography, transient finite element modeling, and Short-Time Fourier Transform (STFT)-frequency-domain analysis. Despite substantial differences in internal heat-dissipation pathways, all substrate configurations exhibited similar peak surface temperatures (~1700–2100 °C), indicating that conventional temperature monitoring alone is insufficient to distinguish geometry-dependent melt-pool behavior. To address this limitation, a Spectral Entropy Index (SEI) derived from STFT analysis was proposed to quantify thermal stability. The channeled substrate exhibited the lowest entropy value (H_s = 0.172), compared with the solid (H_s = 0.181) and blind-hole (H_s = 0.183) configurations, indicating a more ordered and predictable thermal response. Furthermore, distinct variations in the spectral stability shadow revealed geometry-dependent oscillatory behavior that was not observable from thermal histories. Finite element simulations showed good agreement with experimental measurements in conduction-dominated regions (RMSE ≈ 46 °C), whereas deviations were observed within the melt-pool region (~250–310 °C), highlighting the increasing influence of fluid-flow phenomena not captured by the conduction-based model. The results demonstrate that internal substrate architecture primarily influences melt-pool stability through frequency-domain thermodynamics rather than significant changes in peak temperature. The proposed STFT method provides a quantitative approach for monitoring thermal stability and assessing the feasibility of L-DED repair over complex internal geometries. Full article

Additive manufacturing (AM) introduces surface roughness that is much larger than that in chemically etched printed circuit heat exchanger (PCHE) channels, limiting the applicability of established design correlation. In this study, four selective laser melting (SLM) 3D-printed stainless steel test sections were tested, namely two semicircular and two rounded-edge semicircular channels, at hydraulic diameters of 2 mm and 4 mm. Water was used as the test fluid in the experiment, with a Reynolds number ranging from 500 to 7000 and wall heat flux ranging from 20 to 90 kW/m². Scanning electron microscopy image characterization shows significant material accumulation concentrated at the rounded edges of the as-built channels. The experimental results show that for the entire flow regime, the printed rounded edge increases the friction factor by approximately 9% for 2 mm and 4 mm channels. The filleting design would increase the effective hydraulic roughness in small-diameter AM channels. The SLM 3D-printed rougher channel has a lower transition Reynolds number and higher turbulent friction factors compared to the etching channel. The data were compared with existing smooth PCHE channel data and rough AM mini-channel correlation, and two empirical correlations were developed for SLM 3D-printed mini-channels for transition and turbulent regimes. Full article

Herein, we report a method to additively manufacture carbon fiber-reinforced siliconized silicon carbide composites. The process involves the pyrolysis of a 3D-printed carbon fiber-reinforced poly-ether-ether-ketone (PEEK) composite to produce a porous carbon fiber-reinforced carbon matrix composite preform, which is subsequently infiltrated with molten silicon to obtain a carbon fiber-reinforced siliconized silicon carbide composite. A key aspect of the method is limiting polymer melt flow during pyrolysis of PEEK, which is achieved by thermally annealing the 3D-printed carbon fiber-reinforced PEEK preform in air at a temperature below PEEK’s melting temperature. Rheological and differential scanning calorimetry (DSC) measurements demonstrate that the thermal annealing treatment altered the melting behavior of PEEK, while NMR and FTIR measurements provided a mechanistic explanation for the structural changes responsible for the behavior. It was also found that dimensional changes during pyrolysis were anisotropic with greater shrinkage in the stacking direction of the material. Full article

The bubble tube of a glass curing furnace was subjected to extreme heat–flow coupling conditions for a long time due to the scouring of melt flow caused by the gas flow bubbling in a high-temperature molten glass environment at 1150 °C, resulting in severe corrosion and structural failure. This paper conducts post-service sampling analysis of an Inconel 690 bubble tube, and systematically studies its corrosion morphologies, product distribution and corrosion mechanisms. The results show that the outer wall of the bubble tube undergoes an oxidation reaction in the high-temperature molten glass to form a Cr-rich oxide layer. However, local spalling occurs under the scouring of the molten glass flow, resulting in continuous corrosion. The corrosion behavior shows obvious asymmetry. The average corrosion rate near the bubble flow side (the inner curve side, 0.118 mm/day) is significantly higher than that on the outer side (0.051 mm/day) due to the higher partial pressure of oxygen and greater flow rate of molten glass. It reveals the synergistic mechanism by which fluid scouring continuously removes the protective Cr-rich oxide scale, thereby accelerating the oxidation–erosion cycle under the heat-flow coupling effect. The results provided experimental evidence and theoretical reference for the material optimization and life prediction of bubble tubes. Full article

The development of 3D-printable polymer–metal composites offers new opportunities for structured catalytic reactor design and process intensification. Here, cyclic olefin copolymer (COC) composites filled with micron-scale aluminum particles (1–15 wt%, 160 µm) were prepared via a two-step compounding and extrusion process to produce filaments suitable for fused filament fabrication (FFF). Thermal analysis confirmed that aluminum incorporation does not significantly alter the glass transition (T_g = 76–77 °C) or thermal stability of the polymer. Melt flow rate measurements indicated processable viscosity (MFR 3.82–4.57 g/10 min), while tensile testing revealed Young’s modulus of 1277 MPa–1783 MPa, maximum stress of 27 MPa–39 MPa, and enhanced strain at break for the 1 wt% Al composite (ε_B = 5.33%). Composites containing up to 15 wt% Al were successfully printed into mechanically robust static mixers, demonstrating complex geometries without particle sedimentation issues. The incorporation of aluminum particles introduces potential functionalities related to thermal management, surface modification, and future catalytic or photocatalytic applications. This work establishes a scalable polymer–metal platform integrating structural stability, geometric complexity, and prospective multifunctional behavior for advanced flow-reactor applications. Full article

Hot-melt extrusion (HME) is widely used in pharmaceutical manufacturing; however, reliable analytical tools are required to simultaneously monitor drug content and excipient stability under thermal processing. In this study, a selective and robust HPLC–UV method was developed and validated for the concurrent determination of triamcinolone acetonide (TA) and triethyl citrate (TEC) in HME polymeric films and porcine buccal mucosa. Chromatographic separation was achieved on a C₁₈ column using an acetonitrile–water mobile phase (30:70, v/v) at a flow rate of 0.6 mL min⁻¹, with detection at 240 nm for TA and 210 nm for TEC. The method was validated for selectivity, linearity, precision, and accuracy, including selectivity assessment in the presence of mucosal extract and polymeric matrix components, and recovery of TA in porcine buccal mucosa. Excellent linearity was obtained over 0.20–12.5 µg mL⁻¹ for TA and 4.5–30.0 µg mL⁻¹ for TEC (r ≥ 0.998), with precision below 6.3% and TA recovery exceeding 94%. Application to extruded films confirmed uniform analyte distribution and enabled simultaneous monitoring of TA degradation and TEC loss under thermal stress. These results demonstrate that the proposed method is suitable for formulation development, process monitoring, and stability assessment of HME-based pharmaceutical systems. Full article

The study investigates the three-dimensional architecture and thermal structure of the Central Andes in centralsouthern Peru, highlighting the interplay between basement structure, Moho geometry, slab configuration, and thermal properties. Basement structural highs and lows acted as zones of weakness that localized deformation during Andean shortening. The Moho exhibits significant lateral heterogeneity, reflecting the combined effects of subduction processes, crustal shortening, magmatic underplating, and lower crustal flow or delamination. Its geometry provides key constraints on crustal thickness, seismic structure, and lithospheric dynamics. The subducting Nazca Plate shows strong along-strike variations in dip and continuity, influenced by plate kinematics and features such as the Nazca Ridge. These variations control mantle wedge development, arc magmatism, and deformation patterns in the overriding plate, contributing to the segmentation of the Andes. Steepslab segments promote mantle melting and volcanic activity, whereas flat-slab regions suppress magmatism. Consistent with these tectonic controls, Qs values increase from northwest to southeast, reflecting a transition from flat-slab conditions with low heat flow and limited geothermal activity to steep subduction zones characterized by active magmatism, elevated heat flow, and significant geothermal potential. This spatial variation underscores the strong coupling between slab geometry, thermal structure, and surface geothermal expression. Full article

Background: Hot-melt extrusion (HME) is a promising technology for the manufacturing of drug products; however, its application is limited by elevated thermal and shear stresses that may induce degradation of thermolabile active pharmaceutical ingredients. One of the approaches to reducing processing temperatures is the use of polymeric systems with tailored thermal and rheological properties. The aim of the study was to develop an approach for the design of polymeric systems exhibiting a transient plasticization window, enabling a reduction in melt viscosity and improved processability under low-temperature extrusion conditions, followed by the formation of a structurally coherent matrix upon cooling. Methods: The compatibility of the initial polymers was assessed using laser microinterferometry. Based on the obtained data, three- and four-component polymeric compositions were designed and prepared by hot-melt extrusion. The resulting materials were characterized by differential scanning calorimetry, melt rheology analysis, and storage stability assessment. Thermal and rheological data were used to iteratively optimize the polymeric systems. Results: A four-component polymeric system based on PVP K-29/32, PEG 400, PEG 1500, and HPC EF was developed, suitable for processing by hot-melt extrusion at 70 °C. The final system enabled formation of a homogeneous extrudate, exhibited reproducible rheological behavior, and remained stable in the solid-state during storage, with no evidence of cold flow. Conclusions: It was established that, in the design of polymeric systems for hot-melt extrusion, the key factor is not achieving the lowest possible glass transition temperature, but rather the design of a system in which viscosity is transiently reduced under processing conditions and followed by structural stabilization upon cooling. The proposed approach may be applied in the development of polymeric premixes for the preparation of dosage forms by hot-melt extrusion, including those incorporating thermolabile active pharmaceutical ingredients. Full article

Laser powder bed fusion (LPBF) poses significant simulation challenges due to its highly nonlinear thermo-fluid-solid coupling. To address this, we propose an adaptive framework coupling the edge-based smoothed finite element method (ES-FEM) and smoothed particle hydrodynamics (SPH) via a bidirectional element-particle transformation algorithm. This integration leverages ES-FEM for modeling solid thermo-mechanical responses and SPH for resolving melt pool dynamics, enabling fully coupled simulation of temperature, fluid flow, and stress within a unified model. The framework comprises three key components: a nodal mass normalization scheme ensuring conservation during transformations, a ghost particle algorithm for solid-fluid heat transfer and interaction, and a bidirectional finite-element-to-particle conversion mechanism. This work represents the first implementation of bidirectional coupling between mesh-free Lagrangian SPH and Lagrangian FEM. The validation against benchmark cases confirms the framework’s accuracy in capturing transient thermal, hydrodynamic, and mechanical behavior. It successfully reproduces key LPBF phenomena, including melt pool morphology, Marangoni flows, and residual stress evolution, demonstrating its suitability for high-fidelity LPBF process simulation. It should be noted that the current ES-FEM-SPH framework has not taken into account the recoil pressure, evaporation, and the interaction between the powder and the molten pool. The powder is regarded as a rigid body. Future work will focus on incorporating these neglected physical factors to further improve the predictive capability of the proposed framework. Full article