Search Results (654)

Personal thermal management (PTM) textiles can reduce building energy consumption and improve personal comfort, yet their practical application is constrained by the inherent trade-off between flexibility, thermal insulation, and mechanical strength. Herein, porous single-component polyimide (PI) fibers were fabricated via coagulation bath-modulated wet spinning of 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA)–4,4′-oxydianiline (ODA) poly(amic acid) (PAA). By tuning the EtOH/H₂O ratio (20/80–60/40) and winding speed (2.6–13.1 mm/s), the fiber cross-sectional morphology evolves from finger-like macropores to uniform spongy networks, with diameters controllable from 120 to 335 μm. The PI porous fibers exhibit a maximum tensile strength of 56.79 MPa, elongation at break of 13.89%, toughness of 4.98 MJ/m³, and thermal conductivity as low as 0.043 W·m⁻¹·K⁻¹. The highly imidized structure was confirmed by FTIR (imidization index = 0.848), and TGA revealed high thermal stability with 5% weight loss temperatures of 491 °C (N₂) and 488 °C (air). Compared with commercial insulators, a single-layer PI fabric (0.892 mm) shows thermal insulation comparable to that of the thicker aramid 1313 fabric (1.588 mm) under the same 100–200 °C hot-plate conditions, while also exhibiting self-extinguishing behavior equivalent to that of aramid 1313. The 5-layer PI stack (3.637 mm) is only half as thick as glass fiber cotton (7.342 mm) but retains 84–91% of its temperature difference, delivering 1.7–1.8 times higher thickness-normalized insulation efficiency. The ultrathin porous PI fabrics integrate robust mechanical performance, excellent thermal shielding, and flame retardancy, and are promising for extreme-environment thermal management including fire protection, spacecraft thermal control, and battery insulation. Full article

The development of sustainable active food packaging materials with multifunctional protective capabilities is highly desirable for improving food safety and extending shelf life. In this study, sulfur- and nitrogen-rich carbon dots (GLCDs) were synthesized from glycine and lipoic acid through a facile hydrothermal approach and subsequently incorporated into chitosan/poly(vinyl alcohol) (PVA) matrices to fabricate multifunctional nanocomposite films. Structural and physicochemical characterization suggested the successful incorporation of GLCDs within the polymer network and suggested favorable interactions between the nanofillers and the chitosan/PVA matrix. The GLCD-incorporated films exhibited enhanced mechanical strength, improved thermal stability, reduced water vapor permeability, and superior UV-shielding performance compared with pristine chitosan/PVA films. Furthermore, the nanocomposite films demonstrated significantly enhanced antioxidant activity, achieving approximately 60% DPPH and 90% ABTS radical scavenging efficiency at higher GLCD loading. The films also exhibited strong antibacterial activity and demonstrated preservation potential based on qualitative observations during storage by reducing visible spoilage and maintaining structural integrity. In addition, the developed films showed excellent cytocompatibility toward NIH-3T3 fibroblast cells with high cell viability after 5 days of culture. The synergistic combination of GLCDs and chitosan/PVA matrices provides an effective strategy for developing biodegradable, multifunctional, and cytocompatible active packaging materials with potential food-packaging applications. Full article

The rapid advancement of information technology and pervasive use of electronic devices has exacerbated electromagnetic radiation pollution and interference, driving the demand for lightweight, flexible, and high-efficiency electromagnetic shielding materials in materials research. As a high-performance elastomer, thermoplastic polyurethane (TPU) possesses excellent elasticity, wear resistance, oil resistance and processability, making it promising for flexible electronics and wearable devices. However, pure TPU is electrically insulating and exhibits nearly no electromagnetic shielding capability, which requires conductive filler incorporation for functional modification. Herein, ternary TPU/MWCNT/BiFeO₃ composites were fabricated via solution blending and hot pressing, using multi-walled carbon nanotubes (MWCNTs) and bismuth ferrite (BiFeO₃) as conductive and dielectric fillers within the TPU matrix. The effects of filler content on the microstructure, thermal stability, mechanical properties and electromagnetic shielding performance of composites, together with the relevant mechanisms, were systematically studied. For the ternary TPU/MWCNT/BiFeO₃ system, the introduction of BiFeO₃ continuously increases the char residue rate of the composites to 16.01%, while accelerating the reaction process during the main thermal decomposition stage. The mechanical properties gradually deteriorate with the increase in BiFeO₃ content, and the composite with 5 wt% BiFeO₃ almost loses its elastomeric characteristics. The electromagnetic shielding effectiveness (SE) presents a trend of initial increase and subsequent decrease. The composite with 3 wt% BiFeO₃ exhibits the optimal shielding performance, with a 24.7% enhancement in total SE compared with the reference TPU/MWCNT composite containing 1% MWCNT. This improvement is attributed to the interfacial polarization and dipole polarization induced by the appropriate amount of BiFeO₃, which effectively strengthen the electromagnetic wave absorption loss capacity of the composites. Full article

In photovoltaic-based hybrid energy storage systems (PV–HESS), rapid power transients accelerate battery degradation, directly reducing the operating lifetime and sustainability of renewable power resources. To address this issue, the current study proposes an optimal coordinated framework for the simultaneous and coordinated tuning of battery and supercapacitor current-loop proportional–integral (PI) controllers. The proposed framework treats the four PI gains of the battery and supercapacitor controllers as a unified optimization problem, applying five metaheuristic algorithms: Genetic Algorithm (GA), Particle Swarm Optimization (PSO), Gazelle Optimization Algorithm (GOA), Artificial Protozoa Optimizer (APO), and White Shark Optimization (WSO). The optimization problem is directly coupled with a full nonlinear MATLAB 2022b/Simulink PV–HESS model, capturing the dynamic interactions among the PV array, bidirectional converters, DC-link capacitor, storage units, and load. A combined Integral of Time-weighted Absolute Error (ITAE) objective function is used to minimize current tracking errors, ensuring the supercapacitor absorbs fast power fluctuations while shielding the battery from high-frequency thermal and electrical stress. The controllers are evaluated across four operating scenarios involving steady irradiance shifts, rapid irradiance fluctuations, load disturbances, and a simultaneous irradiance drop from 1000 W/m² to 400 W/m² with a 33% load increase. The results confirm stable DC-link regulation and effective power sharing. Specifically, APO delivers superior performance in the high-stress scenario, GOA minimizes transient-error indices, and GA achieves the lowest DC-link voltage RMSE. These findings demonstrate that coordinated tuning effectively balances high-frequency dynamics, extending battery service life and enhancing the long-term operational sustainability of solar microgrid storage. Full article

Micro electrical discharge deposition (micro-EDD) enables maskless direct-write metallic tracks on conductive substrates, but reported implementations rely on purpose-built machines with programmable pulse generators and gap servos. This paper reports a low-cost micro-EDD platform retrofitted from a desktop CNC router driven by GRBL firmware, extended with an Android control application for path definition and process supervision. Discharge is produced by an RC relaxation circuit with no pulse generator and no gap feedback. Copper, aluminium, nickel, and titanium electrodes were deposited onto silicon substrates in an argon atmosphere, maintaining a 10 μm separation. The working point, pd ≈ 0.76 Torr·cm, lies within 20% of the argon Paschen minimum. Track width rises linearly with supply voltage over 330–400 V (w = 0.570 V − 99.2 μm, R² = 0.994), extrapolating to a deposition threshold of 174 V, 37 V above the argon breakdown minimum—indicating an energy threshold distinct from breakdown. Across electrode materials, width shows a trend consistent with thermal diffusivity as $w\propto {\alpha }^{0.46}$ (R² = 0.69, N = 4), resolving the inconsistency that copper, the best conductor, gives the widest track. Polarity reversal changes width by factors of 4.6 (Cu) and 7.5 (Al), consistent with anode-dominated energy partition. Péclet numbers remain below 3 × 10⁻⁴ and overlap ratios above 10³, excluding thermal advection and insufficient overlap as causes of the feed-rate collapse. A five-axis kinematic extension is derived, with Z travel identified as the bounding constraint. Full article

Resin-based carbon fiber composites exhibit outstanding comprehensive mechanical properties, including high specific strength, high modulus, corrosion resistance, low weight, stable dimensional performance and low thermal expansion coefficient, and they have been widely deployed in aerospace, wind power generation, automotive manufacturing, national defense equipment and sports equipment sectors. In aerospace engineering, these composites are employed to manufacture aircraft wings, fuselages and other key components, effectively reducing overall aircraft weight and enhancing fuel efficiency. For wind power facilities, large-scale turbine blades manufactured from such materials gain superior fatigue resistance and an extended service life. In automobile production, structural body parts made of these composites cut vehicle weight and improve energy utilization efficiency; in national defense equipment, they serve as lightweight protective components to boost shielding capacity, while high-performance rackets, bicycles and other sporting goods manufactured from the composites deliver better athletic performance and user comfort. Nevertheless, two critical drawbacks restrict their large-scale application in high-end manufacturing fields: insufficient interfacial bonding between carbon fibers and the resin matrix, and the inherent low ductility of cross-linked epoxy matrices. Therefore, strategies to regulate the mechanical performance of resin matrices and fiber–matrix interfaces have become a prominent research hotspot in recent years. This paper systematically reviews recent research advances regarding resin-based carbon fiber composite optimization, focusing on two mainstream technical routes: carbon fiber surface modification and resin matrix regulation. Meanwhile, prospective research directions are proposed, aiming to provide reliable theoretical references for the further development of this field. Full article

We investigated the possibility of developing super austenitic stainless steel Avesta SMO 254 X1NiCrMoCuN20-18-7 (EN 10088-4) and austenitic stainless steel X15CrNiSi25-21 (EN 10095) coated with SiC, resulting in the obtainment of a Metal Matrix Composite (MMC) by additive manufacturing (AM) for the upgrade of nozzles for sulfur recovery thermal reactors. One layer of the MMC targets the outer surface of the part that is in constant contact with the flame and the area is subjected to high friction erosion. The Directed Energy Deposition Laser (DED-LB) method has made it possible to produce a high strength-to-weight ratio. The aim is to engage lower-cost material with similar thermal stability and durability in extreme conditions. The robotic unit used for the application allowed for computer control of the positioning, feeding of the SiC particles inside the shielding gas and deposition in the molten pool. After the solidification process, visual testing (VT) and ultrasonic testing (UT) were applied for non-destructive evaluation, checking for disbonding and subsurface imperfections. Then, samples were tested with microhardness measurements, bond strength, microcracking detection, porosity, interface zone assessments and microstructural analysis. The process achieved 0.4 to 0.7 KJ mm⁻¹ heat input with no defects and the intended nozzle surface passed UT and VT. Controlled parameters provided strong metallurgical bonding. Full article

To address the escalating demand for ultra-high-purity tungsten in advanced applications such as semiconductor targets and nuclear-grade shielding, this study synergistically coupled the processes of thermal decomposition, ammonia dissolution, and segmented evaporation crystallization. The optimal parameters for the thermal decomposition and ammonia dissolution stages were subsequently identified through systematic optimization. By independently regulating the nucleation and crystal growth processes during the crystallization of ammonium paratungstate (APT), the limitation of traditional methods, which require multiple crystallization cycles to achieve high purity, is effectively overcome. Experimental results demonstrated that under optimized conditions—thermal decomposition at ~280 °C and ammonia dissolution at 90 °C—high-purity APT (4N5 grade, total impurities < 50 ppm) was achieved in a single crystallization cycle. Furthermore, under segmented crystallization conditions (nucleation at 80 °C with a stirring speed of 1.26 m/s and growth at 90 °C with a stirring speed of 1.09 m/s), the product exhibited an average particle size of 34.43 μm and a direct recovery efficiency of 73.1%. By suppressing burst nucleation and reducing impurity adsorption, this process provides a critical technological pathway for large-scale production of ultra-high-purity tungsten materials. Full article

Outdoor settings on a campus can respond differently to summer heat and winter cold. This exploratory case study compared twelve predefined settings on a university campus in Tianjin using a summer peak-solar subset and a winter daytime subset drawn from two 72 h analysis windows in June and December 2025. Three Kestrel 5400 LiNK units and eight shielded DS1923 loggers were deployed at a height of 1.5 m. Direct instrument records were combined with archived background-weather and point-specific inputs on a 10 min grid, with measured and calculated fields identified separately. The Universal Thermal Climate Index (UTCI) and mean radiant temperature (Tmrt) were expressed as anomalies from the contemporaneous twelve-location median. Point-cloud proxies at 10, 25, and 50 m described each location. The summer episode was hot and rain-free, whereas the winter episode was mild, humid, and calm. P09 had the largest negative summer ΔUTCI (−6.80 °C), P07 the largest winter deficit (−5.11 °C), and P10 showed a change from positive in summer to negative in winter. These patterns persisted in candidate-substitution and wind-height checks. The assembled case-campus data identify locations for repeat, fully synchronized monitoring. Full article

The Hyperspectral Infrared Atmospheric Sounder II (HIRAS-II) onboard the Fengyun-3 satellites is a Fourier-transform infrared spectrometer that requires high radiometric calibration accuracy, making the characterization and correction of polarization effects essential. Although the gold-coated scan mirror introduces only weak polarization, its rotation changes the polarization orientation relative to the fixed polarization-sensitive axis of the downstream optics, producing scan-angle-dependent radiometric errors. To characterize and correct this effect, we designed and constructed a dedicated polarization test apparatus and used it to conduct a prelaunch thermal-vacuum (TVAC) polarization test. During the test, HIRAS-II observed the same stable 290 K area-source blackbody over a densely sampled scan-angle range, with the internal calibration target and cold shield serving as the warm and cold references, respectively. Guided by a polarization-induced radiometric error model formulated within the two-point calibration framework, we developed a decoupled two-step least-squares method to retrieve the polarization parameters from the resulting measurements. The method first estimates the equivalent polarization-axis angle of the downstream optical system from the phase of the band-averaged angular modulation and then retrieves the effective combined polarization parameter separately for each field of view (FOV) and spectral channel. The retrieved parameters were subsequently used to calculate the scan-angle-dependent polarization correction term and correct the calibrated spectra. After correction, the FOV-averaged standard deviation over the scan angle decreased from 0.023 to 0.007 K, from 0.024 to 0.007 K, and from 0.045 to 0.014 K in the long-wave (LW), mid-wave 1 (MW1), and mid-wave 2 (MW2) bands, respectively. The corresponding maximum reductions in brightness temperature deviation were 0.093, 0.064, and 0.174 K. The model, experimental approach, and retrieved prelaunch parameters establish a basis for the on-orbit evaluation and correction of scan-angle-dependent polarization-induced radiometric errors. Reducing these errors improves the radiometric calibration accuracy of HIRAS-II and helps provide more reliable Level-1 radiance data for atmospheric profile retrievals and data assimilation in global numerical weather prediction (NWP) systems. Full article

This study reports a systematic, single-additive investigation of biodegradable films based on polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) blends (T2308 and F2332) from Ecovio^® for packaging applications by incorporating additives such as nisin, essential oils (tea tree, lemongrass, eucalyptus, clove leaves), curcumin, and zinc oxide nanoparticles. Their effects on structure, morphology, thermal behavior, mechanical properties, barrier performance, and optical properties were evaluated by FTIR, SEM with EDX, TGA, DSC, DMA, XPS, mechanical testing, water vapor permeability, moisture absorption, contact angle measurements and UV/visible transmittance. FTIR confirmed additive incorporation with bonding interactions. SEM revealed matrix-dependent morphologies, with T2308 being denser and more heterogeneous, F2332 being more homogeneous and flexible. DSC/TGA showed curcumin markedly reduces crystallinity and melting enthalpy in T2308 (weaker effects in F2332), while oils generally decrease crystallinity and shift Tg depending on molecular structure. Mechanical testing indicated modulus is highly matrix-dependent: curcumin, nisin, and ZnO decrease stiffness in T2308, whereas F2332 shows smaller or opposite trends. UV shielding increases with curcumin and ZnO, and clove oil improves barrier performance. Biodegradation was assessed only for neat films: weight loss averaged ~4–6% after 49 days, with PET/HDPE remaining largely inert. These results illustrate the importance of matrix–additive interactions in enabling tailored biodegradable packaging materials. Full article

The increasing demand for real-time monitoring systems has accelerated the adoption of distributed sensors operating in the ultra-low-power regime. However, in retrofittable and hard-to-access applications, providing a continuous external power supply is challenging, while batteries are limited by their lifetime and maintenance requirements. Energy harvesting represents a promising approach to enable autonomous sensor operation by exploiting ambient energy sources, including photovoltaic, thermal, mechanical, and electromagnetic sources. In this work, different circuit topologies for near-field electromagnetic energy harvesting are investigated through simulation and experimental validation. The proposed approach exploits the electromagnetic interference generated by shielded commercial power electronics, such as drivers and power supplies, as an available energy source. The results demonstrate the capability of compact and easily deployable circuits to capture and convert near-field electromagnetic energy into usable electrical power. The proposed methodology provides a flexible solution for powering low-power monitoring systems and can be adapted to different environments by tailoring the harvesting circuit parameters to the available electromagnetic source. Full article

The demand for materials with flame-retardant and electromagnetic shielding properties has increased research on sustainable and multifunctional composites. Thermoset-based hybrid composites containing Fe₃O₄ and activated carbon obtained from solid waste were investigated for flame retardancy and electromagnetic shielding. Activated carbon produced by pyrolysis of buckwheat hulls (agricultural waste) exhibited a BET surface area of 714.33 m²/g and a conductivity of 69.5 S/m, and was used as a filler to enhance electrical conductivity, while Fe₃O₄ was added to promote electromagnetic absorption. Composites with 1, 3, 5 and 7 wt% activated carbon at a constant 15 wt% Fe₃O₄, together with a complementary series at 5 wt% activated carbon with 10, 15, 30 and 45 wt% magnetite, were characterized by limiting oxygen index and thermal analysis. LOI values clustered between 32.31% (Nov-5-15) and 33.71% (Nov-3-15), a 1.40-percentage-point spread around the 34.31% reference Novolac. The 850 °C char yield peaked at 56.38% (Nov-3-15) and 55.34% (Nov-7-15), with T₅₀% reaching 898 °C and 882 °C, respectively, while DTA replaced the 529 °C Novolac exotherm with endothermic Tmax values of 485–501 °C. Electromagnetic shielding effectiveness over the 8–12 GHz range varied from 2.97 ± 0.3 dB (unfilled Nov-0) to a maximum of 9.19 ± 1.46 dB (Nov-5-45, 5 wt% activated carbon and 45 wt% Fe₃O₄), with an intermediate value of 7.43 dB for Nov-7-15. These hybrids are thus candidate materials for fire-safe phenolic-thermoset applications, where magnetic–dielectric coupling and a percolated char-barrier network govern flame-retardant performance, demonstrating the potential of waste-sourced carbon in sustainable composite production. Full article

The prolonged operation of semi-enclosed subway tunnels results in waste heat accumulation, energy wastage, and potential safety hazards. Integrating capillary heat exchangers (CHEs) with tunnel linings to form an energy tunnel is an effective approach to addressing these challenges. However, the current design methodologies for energy tunnels are still non-systematic, and the studies on the design optimization of CHE are still inadequate. To address these gaps, the shield energy tunnel demonstration project in Qingdao was selected as the research object, and a three-dimensional fluid–thermal coupled numerical model was established using the COMSOL simulation platform. A total of 48 CHE design configurations were analyzed to evaluate the heat transfer performance and temperature uniformity of the energy segment. The results indicate that the capillary bundle geometry and the installation position of the CHE are the dominant factors. Specifically, the I-shaped CHE achieves the highest heat transfer capacity, while the W-shaped CHE provides the best temperature uniformity. Installing the CHE within the inner arc protective layer, as opposed to the outer arc protective layer, significantly enhances the heat flux per unit area and improves temperature field uniformity. In addition, the reverse-return connection offers only a marginal advantage over the direct-return configuration, and the capillary group spacing exerts a relatively minor influence on both the heat transfer rate and temperature uniformity of the energy segment. This study provides a reference for the design and engineering application of subway shield energy tunnels. Full article

The miniaturization and high-frequency development of electronic devices demand advanced packaging materials that simultaneously possess improved thermal conductivity, notable electromagnetic interference shielding effectiveness, and reliable electrical insulation. Although liquid metals exhibit superior thermal and electrical conductivity, their potential leakage may cause environmental contamination and corrosion of electronic components. Aiming at this dilemma, we designed novel liquid metal microcapsule composites. The composite features Ga-In alloy droplets encapsulated within poly(urea-formaldehyde) shells, which effectively harness the advantageous properties of liquid metals while preventing leakage risks and providing electrical insulation through the polymeric coating. Four microcapsules with different particle sizes (10.6, 9.8, 8.6, and 7.6 μm) were prepared, and LMMCS were synthesized. Comprehensive characterization revealed that, the composite containing 60 wt% of 9.8 μm microcapsules exhibited optimal thermal conductivity (0.527 W·m⁻¹·K⁻¹). The 60 wt% 7.6 μm composite demonstrated the highest volume resistivity (8.99 × 10¹¹ Ω·cm). EMI shielding effectiveness increased with microcapsule loading, while showing non-monotonic diameter dependence at a fixed 60 wt% concentration. Beyond conventional shielding mechanisms, we developed a microcapacitor model that elucidates the size-dependent interfacial polarization and multiple reflection phenomena. This study provides insights for the design of advanced electronic packaging materials, although further reliability and durability tests are needed to validate practical applicability. Full article