Search Results (8,779)

To address the urgent need for electronics operable in extremely high-temperature environments, this paper presents a novel three-terminal, dual-gate, lateral 4H-SiC n-channel depletion-mode junction field effect transistor (JFET) without a backside electrode. Featuring a fully planar electrode layout, the device eliminates the back-gate effect and significantly improves integration compatibility. Experimental results demonstrate stable DC operation up to 500 °C, with an intrinsic gain of 9.79 at room temperature and 6.01 at 500 °C. Comparison with TCAD simulations confirms excellent agreement in the key physical trends of threshold voltage drift and mobility degradation, though quantitative discrepancies are observed and attributed to process-induced parasitic effects such as non-ideal ohmic contacts and interface states. Analysis shows that the new structure broadens the channel depletion layer by optimizing the depletion profile, thereby suppressing channel-length modulation and improving both output resistance and gate control. This work not only provides an effective device platform for high-temperature 4H-SiC analog integrated circuits (ICs) but also deepens the understanding of process-performance correlations, offering clear guidance for process-oriented device optimization. The proposed structure serves as a foundation for developing fully planar, high-temperature 4H-SiC analog ICs with promising potential in aerospace, automotive, and energy exploration systems. Full article

This paper proposes an experimental, intelligent optimization approach to improve the thermal cooling performance of an overclocked graphics processing unit (GPU). A closed-loop liquid-cooling system was built and tested utilizing deionized water and a silver (Ag) nanofluid coolant (0.015% vol.) across a variety of microchannel heat sink topologies with varying fin spacing. Key thermal performance indicators, including GPU temperature, coolant outlet temperature, and thermal resistance, were measured at different coolant flow rates. Experiments revealed that raising the flow velocity and decreasing the fin gap considerably enhanced cooling performance, while the Ag nanofluid consistently lowered GPU temperature by 1–3 °C compared to water. An Artificial Neural Network (ANN) surrogate model was constructed and trained using experimental data to support predictive analysis and system optimization, achieving excellent predictive accuracy with low RMSE. The trained ANN model was combined with the Non-dominated Sorting Genetic Algorithm II (NSGA-II) to perform multi-objective optimization, aiming to minimize GPU temperature and thermal resistance while improving heat removal. The Pareto-optimal solutions revealed that nanofluid-based cooling offered the best trade-off circumstances, with optimal designs occurring at moderate flow rates and small fin spacing. The ANN-NSGA-II multi-objective optimization results indicated that the best thermal performance of the GPU cooling system was achieved when using Ag nanofluid (0.015 vol.%) as the coolant, with an optimal coolant flow rate in the range of 1.30–1.84 LPM and an optimal fin/channel spacing of 0.57–0.71 mm, producing GPU temperatures of 29.18–29.66 °C, coolant outlet temperatures of 29.06–29.41 °C, and a minimized thermal resistance of 0.0106–0.0152 °C/W; thus, overall, the suggested ANN-NSGA-II framework works well as a practical design tool for improving GPU cooling systems and may be used to other high-heat-flux electronic thermal management applications. Full article

A Ti-Al-Si composite coating was prepared on Ti65 titanium alloy using a two-step hot-dipping + pre-oxidation method to improve its tribological performance and high-temperature oxidation resistance. The second-step dipping time strongly affected the coating microstructure and wear behavior. The optimal coating, prepared with a dipping time of 5 min in each step, exhibited negligible wear after oxidation at 800 °C for 1000 h and 2500 h, with slight adhesive wear and oxidative wear as the dominant mechanisms. Longer dipping times led to mixed wear modes and reduced wear resistance. Under high-temperature corrosion conditions, the coating showed good long-term stability in water vapor, with its mass gain following a sub-parabolic law, Δm = 0.39·t^0.47, because the internal multilayered structure effectively blocked inward oxygen diffusion. However, in environments containing NaCl or 75 wt.% Na₂SO₄ + 25 wt.% NaCl, catastrophic hot corrosion occurred, regardless of the presence of water vapor, through a chlorine-driven oxidation–chlorination–reoxidation autocatalytic cycle. In the mixed salt environment, Na₂SO₄ decomposition supplied additional oxygen and alkaline species, accelerating the degradation and spallation of the Al₂O₃ and TiO₂ scales. Water vapor further intensified this cycle by generating HCl, which promoted rapid consumption of Al and Ti in the coating. This study reveals the wear behavior and hot corrosion failure mechanisms of Ti-Al-Si coatings under complex conditions, providing guidance for process optimization and applications in marine atmospheres. Full article

The three-phase region of Mo₃Si-Mo₅Si₃-Mo₅SiB₂(MoSiB) exhibits excellent high-temperature oxidation resistance and is considered a highly promising high-temperature structural material. However, the presence of porous structures significantly increases the surface area exposed to oxidation. Metallic porous materials often suffer from inadequate corrosion resistance and insufficient high-temperature oxidation resistance, whereas ceramic porous materials are plagued by high brittleness. Intermetallic compounds offer a combination of the advantages of both metals and ceramics. Nevertheless, the high-temperature oxidation behavior of porous MoSiB has not yet been systematically elucidated. The study systematically investigates the effect of pore structure on the high-temperature oxidation behavior of porous MoSiB at 1000 °C and 1300 °C, with a focus on oxidation kinetics, phase evolution, surface and cross-sectional morphology and underlying oxidation mechanisms. The effects of porosity and temperature on the oxidation process are also analyzed. The results indicate that at 1000 °C, the material exhibits uniform oxidation, with lower porosity contributing to better oxidation resistance. At 1300 °C, oxidation is limited to the surface layer, where low-viscosity SiO₂(B) rapidly seals the pores to form a dense protective layer. This research reveals the high-temperature oxidation mechanism and phase evolution of porous MoSiB, providing a theoretical foundation for its application in high-temperature structural fields. Full article

Addressing issues such as corrosion and the eccentric wear of metal tubing strings, low heating efficiency, and high operation and maintenance costs of lifting systems in heavy-oil extraction, core equipment comprising carbon-fiber-reinforced PEEK（Polyetheretherketone） multi-layer composite continuous tubing has been developed. This equipment integrates an embedded cable-laying system and an intelligent regulation module, establishing a rodless oil-extraction technology system suitable for heavy-oil reservoirs. This article systematically describes the process structure, preparation principle, core characteristics, and key parameters of this composite continuous tubing. By deriving an equivalent thermal-resistance model for the multi-layer structure and an unsteady-state heat-transfer equation, precise regulation of the wellbore temperature field is achieved. Combined with field tests at Well A in Jinghe Oilfield, the tubing’s effectiveness in reducing viscosity, increasing production, saving energy, and extending the operational cycle in heavy-oil extraction is verified. The results show that the carbon-fiber-reinforced PEEK composite continuous tubing possesses characteristics such as high strength, strong corrosion resistance, low friction, and high thermal insulation. When paired with a viscosity–temperature coupling regulation algorithm, the heating efficiency is improved by 40% compared to traditional electric heating rods. The efficiency ranges from 37% to 43% when the formation thermal conductivity fluctuates by ±20%. Field applications have achieved a 230% increase in daily oil production, a 30% reduction in system energy consumption, and an extension of the hot washing cycle to over 180 days. The development of this tubing breaks through the technical bottleneck of traditional metal tubing, providing a new material solution for the efficient and intelligent development of heavy-oil extraction, and has broad promotional value. Full article

The structural stability of high-temperature-formed oxide films (HTOFs) on SAC305 solder plays a critical role in determining corrosion reliability during long-term thermal exposure, yet the coupled effects of oxide evolution and substrate microstructure changes remain unclear. In this work, SAC305 solder was thermally aged at 150 °C for 10–60 days, and the evolution of the oxide film structure and substrate microstructure was systematically investigated using SEM, XRD, XPS, and electrochemical techniques. The results reveal that HTOF mainly consists of a SnO/SnO₂-layered structure with thickness increasing slightly from approximately 16.5 nm to 18 nm, while increasing micro-cracks and Ag₃Sn coarsening induced by the Kirkendall effect lead to significant reductions in impedance parameters and corrosion resistance. These findings demonstrate that the degradation of HTOF is governed by the coupled effects of oxide defect accumulation and intermetallic phase coarsening, providing a mechanistic insight into the corrosion failure of SAC305 solder under long-term thermal aging conditions. Full article

The safe immobilization of high-level waste (as actinide) remains a critical bottleneck in the disposal of high-level radioactive waste worldwide. Moreover, the higher specific surface area and surface energy of nano-scale powders enable the production of ceramic materials featuring denser crystal structures and superior strength, hardness, and toughness. Therefore, in this study, Gd³⁺ was used as a surrogate for actinides, and Nb⁵⁺ was introduced as a high-valence charge-compensating cation. Nano-scale powders of CaCO₃, ZrO₂, Gd₂O₃, TiO₂, and Nb₂O₅ were employed to prepare a series of defect-fluorite-derived ceramics, CaZr_1-xGd_xTi_2-xNb_xO₇ (x = 0.1–1.0), via a high-temperature solid-state reaction method, aiming to investigate the atomic substitution mechanisms, phase evolution, and chemical stability under high-valence charge compensation. Laboratory X-ray diffraction (XRD), synchrotron X-ray diffraction (SXRD), and backscattered scanning electron microscopy with energy-dispersive X-ray spectroscopy (BSEM-EDX) confirmed a phase evolution sequence from zirconolite-2M to zirconolite-4M and finally to pyrochlore. This behavior is consistent with that reported for other Ln³⁺-Nb⁵⁺ co-doped zirconolite systems. Rietveld refinement of the SXRD data further revealed, for the first time, the site-occupancy mechanism of Gd and Nb in zirconolite-4M. In both zirconolite-2M and zirconolite-4M, Gd preferentially occupies the Ca sites, whereas Nb substitutes at the Ti sites. In the pyrochlore structure, Ca, Zr, and Gd occupy the 16d sites, while Ti and Nb occupy the 16c sites. Static leaching tests following the MCC-1 protocol showed that pyrochlore exhibits the highest leaching resistance, whereas zirconolite-2M shows the lowest. After 28 days, the highest Gd leaching rate was 1.92(1) × 10⁻⁵ g m⁻² d⁻¹. These results provide new insights into actinide immobilization behavior and compositional design in zirconolite-based waste forms. Full article

Global warming-induced extreme heatwaves present a severe threat to global tomato yield and production stability. To elucidate the molecular regulatory mechanisms underlying heat stress tolerance in tomato (Solanum lycopersicum), this study utilized label-free quantitative proteomics to profile alterations in protein abundance in tomato leaves in response to heat stress. A total of 294 differentially expressed proteins (DEPs) were identified, with function enrichment in the systematic activation of core stress-responsive biological processes, including the mitogen-activated protein kinase (MAPK) signaling cascade, the endoplasmic reticulum protein processing, and glutathione metabolism. Among them, heat shock protein (HSP) family members exhibited the most significant changes, particularly two small heat shock proteins (sHSPs), designated as SlsHSP1 and SlHSP17.4. Functional validation showed that silencing either SlsHSP1 or SlHSP17.4 drastically impaired heat tolerance in tomato plants. Specifically, silenced lines displayed excessive reactive oxygen species (ROS) accumulation and reduced antioxidant enzyme activities, with SlsHSP1-silenced plants showing more severe heat-induced phenotypic damage. Subcellular localization assays further demonstrated SlsHSP1 was located in the ER and SlHSP17.4 in the nucleus. Collectively, this study unravels multiple heat defense regulatory networks in tomato, in which organelle-specific sHSPs like SlsHSP1 and SlHSP17.4 synergistically maintain protein homeostasis and cellular redox balance, conferring broad-spectrum stress resistance in plants under high-temperature stress. Full article

Carbon fiber-reinforced polymer (CFRP) composites are widely employed in the aerospace industry due to their excellent properties such as high specific strength and corrosion resistance. However, the delamination and tearing of composites are prone to occur in the machining of CFRP, which significantly affect its performance. The existing laser-assisted cutting model generally simplifies the machining process into high-temperature conventional cutting, and only reflects the thermal effect by modifying the material parameters. The core selective ablation characteristics of laser–CFRP interaction are completely ignored, and the unique mechanical behavior of bare fiber under a large cutting angle is not modeled, and the quantitative correlation between cutting force evolution and machining damage is lacking. In this study, an innovative method of partially exposing fibers is proposed to simulate laser-assisted machining. A micromechanical model is developed to analyze the removal mechanisms of different phases during CFRP processing, and a cutting force prediction model from the micro to macro scale is also established. At the micro-scale, a micromechanical model for fiber cutting in orthogonal machining of CFRP is constructed based on the elastic foundation beam theory. The results show that the proposed cutting force prediction model has high reliability, and the relative error between the predicted value and the experimental measured value is only 7.81%~8.99%. All experiments were repeated three times. Statistical analysis showed that the repeatability of the results was excellent. Compared with conventional cutting, laser-assisted cutting fundamentally changed the failure mode of the fiber from matrix-constrained crushing fracture to controllable free-end large-deflection bending fracture. This transformation leads to a smoother and more regular fiber fracture surface, which effectively inhibits fiber breakage, matrix tearing, and fiber–matrix interface debonding. Quantitative analysis confirms that under laser-assisted processing conditions, the matrix tearing length is positively linearly correlated with the cutting depth, cutting speed, and bare fiber length. Full article

Accurate estimation of the internal spatial-temporal temperature distribution is crucial for the safety and performance management of lithium-ion batteries. However, traditional lumped parameter models overlook spatial gradients, while numerical methods for partial differential equations (PDEs) incur high computational costs. This paper proposes a hard constraint physics-informed neural network (HCPINN) framework for the real-time reconstruction of the axial temperature field in 18,650 cylindrical batteries. By restructuring the neural network’s solution space through distance functions, the Robin boundary conditions are strictly embedded as hard constraints, ensuring exact satisfaction of the prescribed Robin boundary conditions within the mathematical model and eliminating boundary loss terms. An electro-thermal coupled model considering the Arrhenius effect and state-of-charge (SOC) dependent internal resistance is integrated into the loss function to capture the nonlinear heat generation dynamics. Experimental validation across discharge rates from 1C to 4C demonstrates that the HCPINN achieves high estimation accuracy with a mean absolute error (MAE) below 0.34 °C. Furthermore, by leveraging the continuous differentiability of the model, this study quantifies the evolution of spatial temperature gradients and reveals the ideal heat transfer coefficients required for thermal equilibrium are inverted, providing a quantitative basis for the design of advanced battery thermal management systems (BTMS). Full article

This research developed a ZrSi₂-TiB₂-modified alumina fiber/boron phenolic resin ceramizable composite intended to fulfill the criteria for high-temperature resistance, oxidation resistance, and structural load-bearing capacity in reusable thermal protection systems. The composite exhibits a low thermal conductivity of 0.405 W·m⁻¹·K⁻¹, a reduced density of 2.11 g·cm⁻³, and a high mass retention rate of 89.45% after heat treatment at 1200 °C in air. During thermal cycling at 1200 °C with a 30 min dwell time, it consistently demonstrates excellent stability, mass retention, and mechanical properties, indicating its potential for applications in reusable thermal protection systems. Following 20 cycles, the variation in length and width remains below 0.6%, the mass retention surpasses 80%, and the flexural strength remains above 20 MPa after 15 cycles. Microstructural evolution and thermodynamic analysis disclose that the in situ ceramization reaction of ZrSi₂ and TiB₂ consumes oxygen, inhibits oxygen diffusion, and fills pores and microcracks with oxidation products (SiO₂ and B₂O₃), thereby forming self-healing and densifying phases. This synergistic mechanism of self-healing and densification ensures the reusability of the composite. The research illustrates the performance evolution patterns and strengthening mechanisms of the composite under extreme thermal conditions, confirming its outstanding performance in repeated usage evaluations. Full article

Iron-based shape memory alloy (Fe–SMA) rebars can generate internal prestress in cement-based members after restrained thermal activation; however, the temperature actually reached by embedded rebars in cracked UHPFRC is difficult to infer from exposed bar segments. This study investigates electrical resistance activation of 4% prestrained Fe–SMA rebars embedded in pre-cracked UHPFRC beams and clarifies the activation-control problem by combining thermocouple measurements with a calibrated two-dimensional electro-thermal simulator. Twelve beams (150 × 150 × 600 mm) containing either Dramix 3D or Dramix 4D hooked steel fibers were first loaded in three-point bending to a mid-span displacement of 4 mm. The 4D series reached a 9.47% higher average pre-cracking load, confirming that fiber geometry modified the cracked state before heating. During activation, the exposed rebar segment reached 200 °C after approximately 77 s, whereas the embedded working segment reached the same target only after approximately 213 s; at that moment, the exposed segment was already close to 350 °C. The calibrated simulator reproduced the target activation time with an error of approximately 3 s and visualized the localized heat transfer from Fe–SMA to UHPFRC. The results demonstrate that activation control based only on exposed-bar temperature may cause under-activation of the embedded reinforcement, and that direct internal temperature monitoring is required for reliable Fe–SMA activation in cracked UHPFRC members. Full article

Optical fiber sensors deployed in harsh industrial fields, e.g., high-temperature wet-oxygen, face severe challenges in signal attenuation and mechanical degradation. While amorphous silicon oxycarbide (a-SiOC) coatings offer a promising solution due to their adjustable thermo-mechanical properties, balancing their structural density with environmental stability remains a critical technical bottleneck. In this study, a-SiOC coatings were deposited on optical fibers using hexamethyldisilane (HMDS) and trace oxygen via radio-frequency capacitively coupled plasma-enhanced chemical vapor deposition (PECVD). A systematic investigation was conducted to determine the impact of deposition temperature (70–420 °C) on the precursor dissociation kinetics, microstructural evolution, and corrosion resistance of the coatings. An elevation in temperature promotes the elimination of organic terminal groups (–CH₃, –H) and enhances surface diffusion, driving the coating from a loose, carbon-rich “polymer-like” structure (dominated by Si–C bonds) to a dense, inorganic “silica-like” skeleton (dominated by Si–O–Si bonds). High-temperature corrosion tests in a wet-oxygen environment (500–900 °C) demonstrate that the failure mechanism is highly dependent on deposition temperature. Coatings deposited at low temperatures suffer catastrophic cracking due to pronounced oxidative shrinkage and the release of volatile species, whereas coatings deposited at 420 °C exhibit microcracking caused by severe carbon phase separation and stress concentration within the rigid inorganic network. In the present system, 350 °C is identified as the optimal deposition temperature, as it achieves the best balance of network densification and structural flexibility, while exhibiting the best mechanical performance. Full article

Thermal barrier coatings (TBCs) require materials with intrinsically low thermal conductivity and high grain-boundary thermal resistance to maximize the temperature gradient across the top coat. In this work, the effective thermal conductivity of more than 40 prospective TBC oxides belonging to seven structural families (YSZ/YSH, pyrochlores/fluorites A₂B₂O₇, defective fluorites A₃BO₇, fergusonite/monazite ABO₄, and perovskites ABO₃) was systematically deconvoluted into intrinsic grain thermal conductivity (k_grain) and grain-boundary (R_gb) contributions. It is shown that grain-boundary Kapitza resistance dominates heat transport in virtually all advanced oxides, contributing 60–90% to the total thermal resistance of polycrystalline samples. The lowest k_grain values (4–12 W m⁻¹ K⁻¹) are found for cerates and certain tantalates, while the highest R_gb (up to 7.2 × 10⁻⁶ m² K W⁻¹) are characteristic of high-entropy and heavily doped perovskites. Orthorhombically distorted SrCeO₃-based and high-entropy perovskites combine moderate k_grain (4.7–27.9 W m⁻¹ K⁻¹), high R_gb, and tunable thermal-expansion coefficients (10–13 × 10⁻⁶ K⁻¹), making them the most promising candidates for next-generation TBCs. These findings provide a rational basis for microstructure engineering and composition design aimed at maximizing the temperature drop across TBC layers while maintaining phase stability and CMAS resistance. Full article

To meet the demands for high-frequency, high-speed copper-clad laminates characterized by low dielectric constant, low loss, high heat resistance, and good mechanical performance, this study employs cyanate ester resin (CE) as the matrix. Additionally, polyphenylene oxide resin (YP50S), TPOSS, and silicon-intercalated montmorillonite (Si-MMT) are introduced for synergistic modification. Basalt fiber is further incorporated to prepare composite carrier films. The results demonstrate that YP50S significantly accelerates the curing of CE, resulting in a reduction in the curing peak temperature by 89 °C at a concentration of 10 wt%. TPOSS further amplifies this effect. Si-MMT markedly enhances the overall properties, with 3 wt% yielding optimal performance. The dielectric constant decreases to 3.3 at 1 × 10⁷ Hz while maintaining a low dielectric loss. This strategy effectively enhances the overall performance of CE-based composites. Full article