Search Results (136)

Under high-Mach-number flight conditions, the combustion chambers of hypersonic vehicles encounter extreme thermal environments marked by unilateral heating, high-heat-flux density, and supercritical pressure. Traditional hydrocarbon fuel cooling often suffers from insufficient heat sinks, high-temperature cracking and coking blockages, making it difficult to meet long-endurance thermal protection requirements. Liquid metal, due to its extremely high thermal conductivity, wide liquid phase temperature range, low Prandtl number and electromagnetic pump driving capability, has become a key technology for breaking through the bottleneck of high-heat-flux thermal protection. Apart from the magnitude of heat flux, the heat-transfer time scale (such as the characteristic thermal response time of the wall and the fluid) is also crucial. During hypersonic flight, transient thermal loads can change within milliseconds, requiring rapid thermal response. Liquid metals, due to their high thermal diffusivity, have a shorter thermal diffusion time compared to hydrocarbon fuels. This review employs a systematic literature review of approaches using gallium-indium-tin alloy, GaInSn, focusing on three core directions: the flow and heat-transfer characteristics of liquid metals, the optimization of cooling micro-channels, and the application of thermal protection systems. It summarizes the research progress at home and abroad, compares and analyzes the performance differences and applicable scenarios of typical liquid-metal working fluids, and summarizes the advantages and disadvantages of existing models, structural designs, and system schemes. The research shows that liquid metals can significantly alleviate thermal stratification and eliminate coking, and deep, narrow, tree-shaped, and biomimetic micro-channels can effectively enhance heat transfer. The liquid-metal-fuel dual-channel waste heat recovery and thermoelectric power generation system has demonstrated engineering application potential. Currently, the field still faces key challenges, such as unclear heat-transfer mechanisms under extreme conditions, the lack of general heat-transfer correlation formulas, insufficient compatibility with high-temperature materials, poor miniaturization and vibration resistance of electromagnetic pumps, and low system integration. In the future, efforts should be focused on developing multi-field coupled heat-transfer models under extreme thermal environments using engineered micro-channel structures, corrosion-resistant materials, and lightweight electromagnetic pumps, promoting the research and development of integrated thermal protection, heating and power generation systems, and providing support for the development of advanced thermal management systems for hypersonic aircraft and aviation engines. Full article

Because antimony trisulfide (Sb₂S₃) is abundant on Earth, non-toxic, and naturally has a low lattice thermal conductivity, it has garnered increasing interest as a possible thermoelectric material. One factor contributing to its anisotropic transport behavior is the orthorhombic structure in which Sb₂S₃ crystallizes, which is made up of one-dimensional (Sb₄S₄)_n ribbons. For thermoelectric energy conversion, its comparatively broad band gap (~1.5–1.7 eV) leads to a high Seebeck coefficient, usually in the 200–600 μV/K range. However, due to its inherently low carrier mobility, pristine Sb₂S₃ exhibits poor electrical conductivity, thereby restricting its power factor. Recent research indicates that composite engineering, nanostructuring, and doping (e.g., with elements such as Ln, As, Se, Ni, Zn, and Fe) can enhance the dimensionless figure of merit (ZT) by increasing carrier concentration while suppressing phonon transport. ZT values in bulk Sb₂S₃ range from 0.1 to 0.2 to approximately 0.5 in optimized nanostructured or doped systems. Higher ZT values (>1) are expected to be possible with advanced band engineering and defect management. According to these results, Sb₂S₃ is a promising mid-temperature thermoelectric material that can be used for waste-heat recovery and possibly integrated into hybrid photovoltaic–thermoelectric systems. Full article

With the rapid advancement of the IoT society and growing awareness of environmental issues, thermoelectric conversion technology—which directly converts waste heat into electricity—is gaining attention as a self-powered, autonomous power source capable of driving countless devices. While currently mainstream metal-based inorganic thermoelectric materials demonstrate high performance, their high rigidity and brittleness, as well as their frequent inclusion of toxic heavy metals, have limited their application in biological systems and on curved surfaces. As a next-generation alternative, single-walled carbon nanotubes (SWCNTs)—which possess excellent flexibility, electrical conductivity, and mechanical strength while being low in toxicity—are garnering significant attention. However, n-type SWCNT materials, which are essential for thermoelectric module fabrication, have faced two major barriers to practical application: low atmospheric stability (they easily revert to p-type upon exposure to atmospheric oxygen and moisture) and thermoelectric performance that falls short of inorganic materials. This review comprehensively outlines the latest composite approaches designed to overcome these critical challenges and achieve both extreme atmospheric stability and high thermoelectric performance in n-type SWCNT materials, along with the flexibility required to withstand severe deformation. Three main strategies are discussed. The first is the organic/polymer approach, which involves doping with organic small molecules that control the LUMO level or bicyclic organic superbases with strong electron-donating properties, as well as polymer coating, to achieve long-term stable n-type characteristics and high power output even in air or under severe high-temperature conditions. The second is the inorganic hybrid strategy, which involves nanoscale compositing with inorganic materials such as Bi₂Te₃ and Cu₂O; this reduces thermal conductivity through phonon scattering via interface control, while the inorganic layer physically blocks oxygen to ensure long-term atmospheric stability. The third approach involves ultra-long-term stabilization techniques, such as bulk encapsulation using cationic or gemini surfactants, and environmentally friendly aqueous processes utilizing natural amino acids. Furthermore, we discuss the latest developments in imparting practical-level toughness (flexibility) capable of withstanding thousands of bending cycles and high tensile stress through the introduction of dynamic covalent network polymers and elastomers. The conformal flexible thermoelectric power generation modules created through the integration of composite optimization, low-environmental-impact processes, and doping techniques will serve as a crucial foundational technology for realizing a sustainable next-generation electronics society, including future wearable devices, artificial skin, and smart sensor networks. Full article

PbTe–MgTe based compounds have been demonstrated as promising medium-temperature thermoelectric materials, and significant research efforts have been devoted to enhancing their performance. However, previous studies have primarily focused on low MgTe concentrations (within the solubility limit of ~6 mol%), and a systematic understanding of intrinsic defect behaviors in the PbMgTe solid solution remains lacking. In this work, we perform high-throughput density functional theory calculations to systematically evaluate a comprehensive set of intrinsic defects (including vacancies, anti-sites, and interstitials) in the PbMgTe solid solution modeled by SQS. To the best of our knowledge, this is the first systematic defect study in the PbMgTe system at this composition. Our calculations reveal that vacancies (V_Pb, V_Mg, V_Te) and Mg interstitials (Mg_i) exhibit low formation energies, with acceptor and donor behaviors that effectively facilitate p-type and n-type conductivity, respectively. Notably, these defects induce modifications in the electronic structure that lead to a significant enhancement of the density of states (DOS) near the band edges. Consequently, the Seebeck coefficient is markedly improved compared to that of intrinsic PbMgTe. Our work not only provides valuable insights for defect engineering in PbMgTe-based materials but also establishes a mechanistic link between defect-induced DOS changes and thermopower enhancement, advancing beyond previous studies that focused primarily on formation energies. These findings help bridge the performance gap between n-type and p-type thermoelectric properties. Full article

There has been a rising trend for recovering waste heat, especially after the invention of new types of semiconductors. Among all available utilization options, thermoelectric generation (TEG) systems are promising for recovering waste heat. Thermoelectric devices are environment-friendly, operate silently, and are suitable for low- to high-power applications. This review paper presents a comprehensive study of TEGs, starting with the current problem, state of the art, advantages, disadvantages, generation and related principles, and applications, and covers different arrangements (individual and combined) and working fluids. Furthermore, this article systematically covered various experimental and numerical studies, including optimization, offering insights into heat exchanger configurations, working fluids, and performance parameters. Here, an effort is made to describe the contributions of individual/coupled TEG systems. As a coupled system, the individual TEG system is used with other systems like solar, distillation, solar pond, etc., for cogeneration and enhanced efficiency. The thermal/system parameters of individual/coupled systems are thoroughly discussed, and their impact on efficiency and power generation is illustrated. It was found that the design of the heat exchanger configuration varies from plate type to an efficient liquid-based electricity generation system in these TEG systems. The working fluid inside the fluid loop of a thermoelectric generation system varies from simple fluids to nanofluids. The current state of thermoelectric generation technology is facing challenges in module materials, equipment cost optimization, and commercialization. The progressive TEG generation capabilities have improved with recent advancements in these areas. The power densities are increasing from 0.5 to 1.2 W/cm² in earlier standalone TEGs to 2.5–4.8 W/cm² in recent optimized hybrid configurations, and overall system efficiencies are rising from an average of 5.2% (standalone) to 18.7% in coupled solar-TEG or waste heat recovery systems. The reported maximum ZT values are also improved from ~1.2 to 2.1–2.8 in next-generation materials. Liquid-based heat exchangers in conjunction with nanofluids are the most efficient way to maximize temperature gradient coefficient (0.75–0.92) and minimize parasitic losses. While flexible, ionic, and hybrid next-generation material platforms are still in the early phases of development (TRL 3–5), liquid-based heat exchanger systems improved with nanofluids are closest to commercialization (Technology Readiness Level, TRL 6–8). Therefore, further research in these areas is required to mitigate these challenges. Finally, the recent developments in the thermoelectric generation field and future research direction are briefly discussed. Full article

The escalating global demand for renewable energy has positioned solar photovoltaics (PV) as a critical technology for achieving net-zero emissions. However, PV efficiency is strictly limited by thermal degradation, where elevated operating temperatures significantly reduce power output and accelerate material aging. This review systematically evaluates the integration of advanced phase change materials (PCMs) as a passive thermal management solution. We analyze the transition from material-level innovations—including nano-enhanced PCMs, 3D conductive frameworks, and shape-stabilization—to system-level hybrid architectures such as liquid—PCM, heat pipe-fin, and thermoelectric generator (TEG) integrations. Synthesis of recent empirical data (2024–2026) demonstrates that optimized PCM composites can achieve PV temperature reductions of up to 32 °C and electrical efficiency enhancements exceeding 19%. Furthermore, techno-economic assessments reveal that these systems can reduce the levelized cost of energy (LCOE) by 5–15% and achieve energy payback times as short as 1.5 years. Finally, this paper identifies critical research gaps in long-term outdoor durability, AI-driven predictive modeling, and sustainable bio-based encapsulation, providing a strategic roadmap for the commercialization of next-generation solar thermal management systems. Full article

The transition toward a sustainable hydrogen economy requires the development of advanced materials capable of efficient hydrogen storage and energy conversion. In this work, we present a comprehensive first-principles investigation of the structural, electronic, elastic, and thermoelectric properties of cubic perovskite hydrides XMoH₃ (X = Na, K, and Rb) using the density functional theory within the generalized gradient approximation combined with the Boltzmann transport theory. The calculated gravimetric hydrogen storage capacities are 2.48 wt%, 2.19 wt%, and 1.64 wt% for NaMoH₃, KMoH₃, and RbMoH₃, respectively, indicating moderate storage potential. Elastic analysis confirms mechanical stability and reveals predominantly brittle-to-intermediate behavior with mixed bonding characteristics. Electronic band structures and density of states demonstrate metallic conductivity, driven mainly by Mo-d orbital contributions near the Fermi level, which may facilitate charge transport and hydrogen mobility. Thermoelectric analysis shows temperature-dependent electrical and thermal conductivities, with KMoH₃ and NaMoH₃ exhibiting relatively higher power factors at elevated temperatures, although the overall figure of merit (ZT < 0.3) remains below the threshold for high-performance thermoelectric applications. Despite these limitations, the combined properties of structural stability, metallic conductivity, and moderate hydrogen storage capacity highlight the potential of XMoH₃ compounds as multifunctional materials for integrated hydrogen storage and thermal energy recovery systems. This study provides fundamental insights into the design of perovskite hydrides and underscores their relevance as tunable platforms for future sustainable energy technologies. Full article

Bi₂Te₃-based materials are benchmark room-temperature thermoelectrics, widely used in refrigeration, waste heat recovery, and microdevice thermal management. Magnetron sputtering demonstrates significant potential as an effective strategy for the mass production of superior Bi₂Te₃ thin films, offering advantages such as dense microstructure, controllable composition, good repeatability, and compatibility with semiconductor processes. However, existing studies largely focus on individual factors affecting film properties, lacking a systematic understanding of the interrelationships among process parameters, microstructures, and thermoelectric performance. Poor comparability across studies due to varying deposition conditions further limits insight into key controlling mechanisms. Recent efforts have centered on three regulatory aspects in magnetron sputtering: (1) optimization of sputtering parameters (e.g., power, pressure, temperature, and target composition); (2) post-annealing treatment; and (3) doping modification. Notable progress has been made in enhancing thermoelectric performance through these approaches. This paper provides a comprehensive overview of recent advancements in the fabrication of Bi₂Te₃ thin films via magnetron sputtering, focusing on how process parameters, post-treatment, and doping affect microstructure, stoichiometry, and thermoelectric properties. The aim is to elucidate structure-performance correlations and guide the optimized preparation of high-performance films. Full article

The inherent coupling of electrical and thermal transport parameters poses a significant challenge for enhancing the thermoelectric figure of merit (zT) in PbTe-based materials. Herein, we report a synergistic co-doping strategy employing Mn and Sn in p-type PbTe to simultaneously optimize the band structure and suppress lattice thermal conductivity. Sn incorporation not only induces additional Pb vacancies, thereby increasing hole carrier concentration, but also facilitates the enhanced solubility of Na dopants within the matrix, as confirmed by microscopic and compositional analyses. More importantly, the cooperative effect of Mn and Sn substantially enhances convergence between the L and Σ valence bands, leading to an increased density-of-states effective mass and a pronounced enhancement of the Seebeck coefficient. Meanwhile, multiscale lattice defects introduced by co-doping effectively scatter phonons over a broad frequency spectrum, reducing the lattice thermal conductivity to near the theoretical minimum (~0.5 W m⁻¹ K⁻¹). As a result, the Pb_0.91−xNa_0.04Mn_0.04Sn_xTe system achieves an exceptional peak zT of ~2.2 at 823 K, a high room-temperature zT of ~0.4, and a favorable average zT of ~1.3 over the temperature range of 303–823 K. Notably, the room-temperature zT of ~0.4 represents the highest value reported to date for p-type PbTe in the room-temperature region. This work demonstrates that Mn and Sn co-doping provides a compelling pathway for realizing both high peak and average thermoelectric performance, advancing PbTe-based materials toward practical waste-heat recovery applications. Full article

Nanotechnology has emerged as a key driver in radioisotope batteries, which offer unique advantages for long-term, maintenance-free energy supply in deep space exploration, medical implants, and nuclear waste utilization. This review summarizes recent progress in applying nanomaterials and nanostructures to overcome the limitations of nuclear batteries, including low energy conversion efficiency and poor stability. The main content focuses on the three primary conversion mechanisms of thermoelectric, radio-voltaic, and radio-photovoltaic batteries, discussing high-performance thermoelectric nanomaterials such as SiGe alloys, wide-bandgap semiconductors including diamond and SiC for enhanced carrier collection, and nanoscale radionuclide ources to mitigate self-absorption losses. This review further elaborates on how nanostructure regulation and interface engineering have significantly improved carrier collection efficiency and device stability. These advances have enabled notable civilian applications, such as the BV100 and “Zhulong No.1” nuclear batteries. Despite this progress, challenges remain in ensuring long-term material stability under extreme environments, maintaining performance consistency during macroscopic device integration, and addressing the high fabrication costs. The review concludes by outlining future research directions, including the development of novel nanomaterial systems, innovative nanostructure designs, scalable manufacturing processes, and enhanced device stability and safety, to further advance next-generation radioisotope batteries. Full article

Aerogels represent an extraordinary class of materials characterized by remarkable properties, including an exceptionally high porosity (approximately 99.8%), minimal weight, extraordinarily low density, low thermal conductivity, a diminished dielectric constant, and a reduced refractive index. These attributes arise from their extensive micro-meter-sized pores. In recent years, there has been a notable surge of interest in carbon or carbon nanotube (CNT) based aerogels due to their compelling potential across various applications, encompassing sensors, energy systems, and catalysis, among others. In the context of our ongoing investigation, we have successfully synthesized lightweight aerogels by incorporating copper and carbon nanotubes (Cu-CNT) through electrospinning. Intriguingly, these aerogels exhibit an electrical conductivity of approximately 0.5 × 103 S/cm, positioning them within the realm of semiconductors. Concurrently, their density measures approximately 1.669 g/c.c (similar to CNTs), underscoring their notably low mass. These semi-conductive aerogels, uniquely characterized by their lightweight nature and expansive surface area (approximately 442 m²/g), manifest considerable potential across a spectrum of applications. This includes catalytic processes, energy storage mechanisms, bio-sensing technologies, thermoelectric systems, and the burgeoning domains of micro and wearable electronics. The distinctive combination of properties within these aerogels augments their suitability for these diverse applications, offering the prospect of innovative and impactful advancements in various scientific and technological arenas. Full article

Gallium-based liquid metals have garnered significant attention due to their distinct combination of metallic and liquid behavior at room temperature. This review systematically examines the fundamental properties and advanced multifunctional applications of this class of materials. Key characteristics such as low melting point, excellent fluidity, high electrical and thermal conductivity, and biocompatibility are first highlighted. Subsequently, progress in four major application areas is discussed. In sensing, these materials enable the fabrication of highly compliant and responsive devices capable of monitoring strain, temperature, and electromagnetic fields. Within biomedical engineering, their inherent low toxicity and biocompatibility underpin advances in biosensing platforms, precision drug delivery, and engineered tissue scaffolds. For energy-related applications, they are utilized in batteries and high-efficiency thermoelectric systems for converting heat into electricity. In catalysis, their dynamic and tunable interfaces facilitate efficient carbon dioxide conversion and selective thermocatalytic reactions. This review summarizes current advances in the application of gallium-based liquid metals and provides critical perspectives on future developments and opportunities in this technology. Full article

The field of perovskites continues to advance each day, with new materials being discovered in order to eliminate the toxic and less efficient ones. Some of the challenges currently facing the perovskite industry include coming up with materials with higher electrical conductivity and lower thermal conductivity, as well as p-type semiconductors. In an attempt to address these challenges, this study modeled two novel perovskites from potassium hexachloroosmate (VI) (K₂OsCl₆) by replacing some of the chlorine atoms with those of silver, then characterized their structural, electronic (using both conventional and hybrid functionals), and thermoelectric properties using Quantum Espresso and BoltzTrap2 codes. The calculations were performed within the framework of density functional theory. The results showed that the novel materials exhibited higher density, lower thermal conductivity, lower band gaps, and positive Hall coefficient, unlike the K₂OsCl₆ sample. These materials can thus be used in areas such as in p–n junctions, thermoelectric devices, and optoelectronic devices. However, since this study was purely computational, the properties need to be verified through an experimental study. Full article

Conventional thermoelectric generators (TEGs) suffer from thermal resistance introduced by ceramic substrates and thermal interface materials, which limits the achievable temperature gradient across the junctions and reduces conversion efficiency. To overcome this limitation, a pin-fin integrated thermoelectric device (iTED) is proposed, in which the hot-side heat exchanger is incorporated directly into the hot-side interconnector, eliminating the ceramic and associated greases. An explicitly coupled thermal-fluid-electric finite-volume model is developed in ANSYS Fluent’s user-defined scalar (UDS) environment to quantify the simultaneous thermal-fluid-electric behavior of the iTED for inlet temperatures of 350 $\le T_{\mathrm{in}}\mathrm{K}\le$ 650, Reynolds numbers of 3000 $\le \mathrm{Re}\le$ 15,000, and load resistances ranging from 0.01 to ${10}^6$% of the internal device resistance ($R_{\mathrm{int}}$), for a fixed cold-side temperature of 300 K. The model is validated against established tube-bank correlations (2.2% agreement in pumping power) and a one-dimensional Explicit Thomson Model (1.2–6.9% agreement across all electrical system response quantities). Compared with an equivalently sized conventional TEG, the iTED achieves a 4.6-fold higher maximum power output (23.9 [W] vs. 5.2 [W] at Re = 15,000), a 2.8-fold higher thermal conversion efficiency (8.1% vs. 2.9%), and a 4.8-fold higher performance index (7.8 [-] vs. 1.6 [-] at Re = 3000), all at $T_{\mathrm{in}}$ = 650 K. A performance index analysis reveals that lower Reynolds numbers and higher inlet temperatures maximize the net power benefit, delineating the operational envelope in which the iTED produces more electrical power than is needed for fluid pumping. These findings demonstrate that device-level restructuring—specifically, the elimination of interfacial thermal resistance via integrated pin-fin heat exchangers—can yield performance improvements comparable to or exceeding those achievable through material advances alone. Full article

At present, the advancement of thermoelectric technology remains largely focused on developing high-performance thermoelectric materials, while comparatively little attention is directed towards its fundamental principles. To address this gap, this study introduces a new physical quantity, the “thermoelectric diffusion potential”, which clarifies the physical interpretations of various thermoelectric coefficients. Analyses reveal that, within a thermoelectric element, the Seebeck coefficient represents a balance between the thermoelectric diffusion field and electrostatic field, rather than between temperature and voltage differences. Using the thermoelectric diffusion potential, the relationship between the Seebeck and Peltier coefficients can be derived directly. Building on this framework, two additional physical quantities, namely the “thermoelectric energy” and “thermoelectric energy flow”, associated with the thermoelectric diffusion potential, are introduced. The formulation of thermoelectric energy flow helps derive the energy conversion relationship at the interface on a macroscopic level. Specifically, energy conversion at the interface occurs between thermoelectric and thermal energy flows, while within the element, it takes place between thermoelectric and electrical energy flows. Owing to the dual nature of internal energy in thermoelectric materials, manifesting as both thermal and electrical energy, the conversion within the element can also be regarded as one between thermal and electrical energy flows. The proposed quantities constitute an important complementary interpretation for the existing thermoelectric framework. Full article