Tianmushan Laboratory

Thermoelectric cooling technology has important applications for processes such as precise temperature control in intelligent electronics. The bismuth telluride (Bi 2 Te 3 )–based coolers currently in use are limited by the scarcity of Te and less-than-ideal cooling capability. We demonstrate how removing lattice vacancies through a grid-design strategy switched PbSe from being useful as a medium-temperature power generator to a thermoelectric cooler. At room temperature, the seven-pair device based on n-type PbSe and p-type SnSe produced a maximum cooling temperature difference of ~73 kelvin, with a single-leg power generation efficiency approaching 11.2%. We attribute our results to a power factor of >52 microwatts per centimeter per square kelvin, which was achieved by boosting carrier mobility. Our demonstration suggests a path for commercial applications of thermoelectric cooling based on Earth-abundant Te-free selenide-based compounds.

Thermoelectrics have been limited by the scarcity of their constituent elements, especially telluride. The earth-abundant, wide-bandgap ( E g ≈ 46 k B T ) tin sulfide (SnS) has shown promising performance in its crystal form. We improved the thermoelectric efficiency in SnS crystals by promoting the convergence of energy and momentum of four valance bands, termed quadruple-band synglisis. We introduced more Sn vacancies to activate quadruple-band synglisis and facilitate carrier transport by inducing SnS 2 in selenium (Se)–alloyed SnS, leading to a high dimensionless figure of merit ( ZT ) of ~1.0 at 300 kelvin and an average ZT of ~1.3 at 300 to 773 kelvin in p-type SnS crystals. We further obtained an experimental efficiency of ~6.5%, and our fabricated cooler demonstrated a maximum cooling temperature difference of ~48.4 kelvin at 353 kelvin. Our observations should draw interest to earth-abundant SnS crystals for applications of waste-heat recovery and thermoelectric cooling.

Developing zero-global warming potential refrigerants has emerged as one area that helps address global climate change concerns. Various high-efficiency caloric cooling techniques meet this goal, but scaling them up to technologically meaningful performance remains challenging. We have developed an elastocaloric cooling system with a maximum cooling power of 260 watts and a maximum temperature span of 22.5 kelvin. These values are among the highest reported for any caloric cooling system. Its key feature is the compression of fatigue-resistant elastocaloric nitinol (NiTi) tubes configured in a versatile multimode heat exchange architecture, which allows the harnessing of both high delivered cooling power and large temperature spans. Our system shows that elastocaloric cooling, which only emerged 8 years ago, is a promising direction for commercializing caloric cooling.

Thermoelectric technology experienced rapid development over the past 20 years, with the most promising applications being in both power generation and active cooling. Among existing thermoelectrics, tin selenide (SnSe) has had particularly rapid development owing to the unexpectedly high thermoelectric efficiency that has been continuously established over the past decade. Several transport mechanisms and strategies used to interpret and improve the thermoelectric performance of SnSe have been important for understanding and developing other material systems with SnSe-like characteristics. Similar to other thermoelectrics, building commercially viable SnSe-based devices requires advances in device efficiency and service stability. Further optimization across all material systems should enable thermoelectric technology to play a critical role in the future global energy landscape.

Most industrial applications concern output torque, rotor mass, and utilization of rare Earth permanent-magnet (PM) material of electrical machines. Generally, it is challenging to improve these aspects simultaneously. The objective of this article is to propose a novel concentrated-flux-type PM machine with irregular magnets and iron poles (CPMIP). The configuration has following advantages. First, the employment of quasitrapezoid magnets with opposite magnetization direction and large cross-section helps to enhance the flux-focusing effect and thus the torque generation. Second, the quasitriangular iron poles can improve the magnetic self-shielding effect well, and thus the rotor yoke can be removed completely and the rotor mass could be reduced significantly. Third, due to the reduction of PM volume and the improvement of torque output, the PM utilization ratio of electrical machine can be increased greatly. The schematic structure and pole patterns of the proposed electric machine are presented. Subsequently, the equivalent magnet circuit is established to validate the performance improvement of the CPMIP machine. Then, the design improvement with offset iron-pole arc is proposed to suppress torque ripple and balance torque output and PM utilization ratio capability well. Following that, an electrical machine with the irregular magnets and iron poles is designed. Then, the electromagnetic characteristics of the proposed pole designs are compared with those of the electric machines with conventional radial, Halbach, and consequent-pole patterns. Finally, the research prototype is developed, and experiments are conducted to verify the design concept and analysis of CPMIP machine.

The extraordinary work hardening ability and fracture toughness of the face-centered cubic (fcc) high-entropy alloys render them ideal candidates for many structural applications. Here, the deformation and failure mechanisms of an equiatomic CrCoNi medium-entropyalloy (MEA) were investigated by powerful laser-driven shock experiments. Multiscale characterization demonstrates that profuse planar defects including stacking faults, nanotwins, and hexagonal nanolamella were generated during shock compression, forming a three-dimensional network. During shock release, the MEA fractured by strong tensile deformation and numerous voids was observed in the vicinity of the fracture plane. High defect populations, nanorecrystallization, and amorphization were found adjacent to these areas of localized deformation. Molecular dynamics simulations corroborate the experimental results and suggest that deformation-induced defects formed before void nucleation govern the geometry of void growth and delay their coalescence. Our results indicate that the CrCoNi-based alloys are impact resistant, damage tolerant, and potentially suitable in applications under extreme conditions.

Due to the rising concept of advanced air mobility (AAM), electric vertical take-off and landing (eVTOL) aircraft has become the hotspot for academic research and commercial application. This paper provides a comprehensive review of latest researches related to autonomous eVTOL. It examines key technologies involved in autonomous eVTOL, including automated flight control, sensing & perception, safety & reliability, and decision making. It also addresses the technical, regulatory, and societal challenges associated with the wholesale adoption of autonomous eVTOL into AAM. The paper concludes with a discussion of future trends and recommendations, including the importance of integration with air traffic management, urban infrastructure and human-machine interaction. It aims to be a useful resource for those involved in the research, policy, and industry of autonomous eVTOL technology.

Abstract Volcanic ash is a major threat to aviation safety. The softening/melting temperatures of volcanic ash lie far below typical aero‐engine operating temperatures. Thus, molten ash can accelerate the failure of thermal barrier coatings (TBCs). Here, inspired by natural superhydrophobic surfaces (e.g., the lotus leaf), a molten‐volcanic‐ash‐phobic TBC, which provides a large possibility to eliminate molten ash issues of TBCs, is developed. A hierarchically structured surface is first prepared on a (Gd 0.9 Yb 0.1 ) 2 Zr 2 O 7 (GYbZ) pellet by ultrafast laser direct writing technology, aiming to confirm the feasibility of the biomimetic microstructure to repel molten volcanic ash wetting. Then biomimetic‐structured GYbZ TBCs are successfully fabricated using plasma spray physical vapor deposition, which reveals “silicate” phobicity at high temperatures. The exciting molten‐volcanic‐ash‐phobic attribute of the designed surfaces is attributed to the lotus‐leaf‐like dual‐scale microstructure, emulating in particular the existence of nanoparticles. These findings may be an important step toward the development of next‐generation aviation engines with greatly reduced vulnerability to environmental siliceous debris.

Abstract Thermoelectrics have great potential for use in waste heat recovery to improve energy utilization. Moreover, serving as a solid-state heat pump, they have found practical application in cooling electronic products. Nevertheless, the scarcity of commercial Bi 2 Te 3 raw materials has impeded the sustainable and widespread application of thermoelectric technology. In this study, we developed a low-cost and earth-abundant PbS compound with impressive thermoelectric performance. The optimized n-type PbS material achieved a record-high room temperature ZT of 0.64 in this system. Additionally, the first thermoelectric cooling device based on n-type PbS was fabricated, which exhibits a remarkable cooling temperature difference of ~36.9 K at room temperature. Meanwhile, the power generation efficiency of a single-leg device employing our n-type PbS material reaches ~8%, showing significant potential in harvesting waste heat into valuable electrical power. This study demonstrates the feasibility of sustainable n-type PbS as a viable alternative to commercial Bi 2 Te 3 , thereby extending the application of thermoelectrics.

Heterogeneous microstructural design has been proven to be an effective strategy in breaking the strength–ductility dilemma in nanostructured metals. However, the precise control of heterogeneous microstructures to achieve strength–ductility synergy remains challenging. Here, we demonstrate a novel powder metallurgy approach for creating three-dimensional (3D) core–shell nanostructures with highly tunable shell thickness and grain size distributions. These 3D nanostructures enable superior strength–ductility synergy in pure copper, pushing the boundary of the Ashby map to unchartered territory. A combination of microstructural characterization, atomistic simulations and crystal plasticity modeling reveals that the generation and accumulation of geometrically necessary dislocations near the core–shell interface play a pivotal role in accommodating the strain gradient and sustaining a high strain-hardening rate during plastic deformation . Our work provides a viable approach for designing bulk nanostructured materials with 3D heterogeneous ingredients and demonstrates a promising pathway for the development of strong and ductile materials .

Superficial flow velocity perception is inspired by aquatic organisms and has become increasingly important for underwater robots and vehicles. Existing marine electromagnetic velometers require very large AC coils with high power consumption for excitation, limiting their mobility and underwater applications. Permanent magnet excitation is preferable for miniature flow sensors because of low power consumption, small size, and high sensitivity. However, permanent magnet excitation has not been applicable due to the high output drift caused by electrode polarization voltage. This paper proposes a permanent magnet-based flow velocity meter that measures the velocity based on the electrode output current instead of the output voltage. The relationship between the output current and the fluid velocity, fluid conductivity, permanent magnet parameters, and electrode position during permanent magnet excitation is derived, and a finite element simulation is conducted. A signal processing circuit is designed to obtain the current output. The experimental results show that the output drift ratio of the proposed sensor is 92% lower than that of the sensor measuring the voltage output, and the measurement <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is 0.998 in the test range of 0-0.875m/s.

Abstract Thermoelectrics has applications in power generation and refrigeration. Since only commercial Bi 2 Te 3 has a low abundance Te, PbSe gets attention. This work enhances the near‐room temperature performance of p‐type PbSe through enhancing carrier mobility via lattice plainification. Composition controlled and Cu‐doped p‐type PbSe crystals are grown through physical vapor deposition. Results exhibit an enhanced carrier mobility ≈2578 cm 2 V −1 s −1 for Pb 0.996 Cu 0.0004 Se. Microstructure characterization and density functional theory calculations verify the introduced Cu atoms filled Pb vacancies, realizing lattice plainification and enhancing the carrier mobility. The Pb 0.996 Cu 0.0004 Se sample achieves a power factor ≈42 µW cm −1 K −2 and a ZT ≈ 0.7 at 300 K. The average ZT of it reaches ≈0.9 (300–573 K), resulting in a single‐leg power generation efficiency of 7.1% at temperature difference of 270 K, comparable to that of p‐type commercial Bi 2 Te 3 . A 7‐pairs device paired the p‐type Pb 0.996 Cu 0.0004 Se with the n‐type commercial Bi 2 Te 3 shows a maximum cooling temperature difference ≈42 K with the hot side at 300 K, ≈65% of that of the commercial Bi 2 Te 3 device. This work highlights the potential of p‐type PbSe for power generation and refrigeration near room temperature and hope to inspire researchers on replacing commercial Bi 2 Te 3 .

Abstract A complex electromagnetic environment is a formidable challenge in national defense areas. Microwave‐absorbing materials are considered as a strategy to tackle this challenge. In this work, lightweight, flexible, and thermal insulating Carbon/SiO 2 @CNTs (CSC) aerogel is successfully prepared coupled with outstanding microwave absorbing performance, through freeze‐drying and high‐temperature annealing techniques. The CSC aerogel shows a strong reflection loss (−55.16 dB) as well as wide effective absorbing bandwidth (8.5 GHz) in 2–18 GHz. It also retains good microwave absorption properties under tension and compression. Radar cross‐sectional (RCS) simulation result demonstrates the CSC processing a strong reduction ability of RCS compared with a metal plate. Further exploration shows amazing flexibility and good thermal insulation properties of CSC. The successful preparation of this composite aerogel provides a broad prospect for the design of microwave‐absorbing materials.

This article presents a novel radial-flux surface-mounted PM (SPM) machine with quasi-cylindrical pole pattern (QCPP). With the proposed configuration, the cogging torque and torque ripple of surface-mounted machines could be greatly decreased due to the adoption of large eccentric distance and the reduction of high-order airgap flux density harmonics. Moreover, the increase of fundamental flux component helps to improve torque generation well. Additionally, the magnet poles are semi-embedded into the rotor, and thus the sleeve in conventional SPM machines is no longer necessary, which helps to reduce the airgap size and improve the torque output further. Besides, the quasi-cylindrical magnet could offer lower rotor eddy loss and higher anti-demagnetization capability than conventional radial and eccentric pole patterns. Studies have been conducted on the novel structure to validate its advantages. Firstly, the topological structure and working principle of the QCPP machine are presented. Then, the influence of the QCPP structural parameters on the torque performance is investigated. Next, an electrical machine with quasi-cylindrical pole pattern is designed. Subsequently, the electromagnetic characteristics, such as flux density distribution, back EMF, average torque, cogging torque, torque ripple, eddy loss in sleeve, rotor stress and anti-demagnetization capability, of the proposed machine are analyzed and compared with those of conventional SPM machine with eccentric magnetic poles and skewing slots. Finally, one research prototype is developed, and experiments are carried out to evaluate the design concept and performance of the proposed QCPP machine.

Lithium (Li)-metal batteries (LMBs) with stable solid electrolyte interphase (SEI) and dendrite-free formation have great potential in next-generation energy storage devices. Here, vertically aligned 3D Cu2S nanosheet arrays are fabricated on the surface of commercial Cu foils, which in situ generate ultrathin Cu nanosheet arrays to reduce local current density and Li2S layers on the surfaces to work as an excellent artificial SEI. It is found that Li presents a 3D-to-planar deposition model, and Li2S layers are reversibly movable between the 3D nanosheet surface and 2D planar surface of Li during long-term cycling. This enables ultrasmooth and dense Li deposition at 1 mA cm-2, presenting an average thickness of ≈53.0 µm at 10 mAh cm-2, which is close to the theoretical Li foil thickness and is highly reversible at different cycles. Thus, 1150 stable cycles with high Coulombic efficiency (CE, 99.1%) at ether-based electrolytes and 300 stable cycles with high CE (98.8%) at carbonate electrolytes are realized in half-cell with a capacity of 1 mAh cm-2 at 1 mA cm-2. When coupled with commercial cathodes (LiFePO4 or LiNi0.8Co0.1Mn0.1O2), the full cells present substantially enhanced cyclability under high cathode loading, limited (or zero) Li excess, and lean electrolyte conditions, even at −20 °C.

The exclusive selectivity of the chlorine evolution reaction (CER) is crucial for the chlor-alkali industry to obtain pure chlorine gas and avoid the cost of separating the byproduct oxygen. However, 100% CER selectivity remains a challenge for the currently known CER catalysts. Here, we report a catalyst of atomic single-layer Ir clusters on CeO 2 nanorods (Ir SL /CeO 2 ). Under the strong metal/support interaction, Ir SL has a strong adsorption to oxygen, thereby suppressing the oxygen evolution reaction. Coupled with the uniform active sites of the single-layer Ir clusters, Ir SL /CeO 2 achieves almost 100% CER selectivity in acidic NaCl solution ranging from open circuit potential to practical current density levels. In addition, Ir SL /CeO 2 exhibits 1.7 times higher catalytic activity than its single-atom counterparts, and its noble metal efficiency is 84 times higher than that of commercial anodes (DSAs). Our finding provides a solution to the selective catalysis of chlor-alkali electrolysis.

Metastable β-type Ti alloys that undergo stress-induced martensitic transformation and/or deformation twinning mechanisms have the potential to simultaneously enhance strength and ductility through the transformation-induced plasticity effect (TRIP) and twinning-induced plasticity (TWIP) effect. These TRIP/TWIP Ti alloys represent a new generation of strain hardenable Ti alloys, holding great promise for structural applications. Nonetheless, the relatively low yield strength is the main factor limiting the practical applications of TRIP/TWIP Ti alloys. The intricate interplay among chemical compositions, deformation mechanisms, and mechanical properties in TRIP/TWIP Ti alloys poses a challenge for the development of new TRIP/TWIP Ti alloys. This review delves into the understanding of deformation mechanisms and strain hardening behavior of TRIP/TWIP Ti alloys and summarizes the role of β phase stability, α″ martensite, α′ martensite, and ω phase on the TRIP/TWIP effects. This is followed by the introduction of compositional design strategies that empower the precise design of new TRIP/TWIP Ti alloys through multi-element alloying. Then, the recent development of TRIP/TWIP Ti alloys and the strengthening strategies to enhance their yield strength while preserving high-strain hardening capability are summarized. Finally, future prospects and suggestions for the continued design and development of high-performance TRIP/TWIP Ti alloys are highlighted.

Metallic alloys have played essential roles in human civilization due to their balanced strength and ductility. Metastable phases and twins have been introduced to overcome the strength-ductility tradeoff in face-centered cubic (FCC) high-entropy alloys (HEAs). However, there is still a lack of quantifiable mechanisms to predict good combinations of the two mechanical properties. Here we propose a possible mechanism based on the parameter κ, the ratio of short-ranged interactions between closed-pack planes. It promotes the formation of various nanoscale stacking sequences and enhances the work-hardening ability of the alloys. Guided by the theory, we successfully designed HEAs with enhanced strength and ductility compared with other extensively studied CoCrNi-based systems. Our results not only offer a physical picture of the strengthening effects but can also be used as a practical design principle to enhance the strength-ductility synergy in HEAs.

Abstract Superhydrophobic surfaces integrating photo‐thermal and electro‐thermal have been regarded as one of the most promising anti‐/deicing approaches in all‐weather conditions. However, excessive energy consumption remains a significant obstacle to their development. Bioinspired by the energy storage and conversion functions of creatures surviving in extremely cold environments, the naturally anisotropic porous wood is performed as a substrate and a photo/electro‐thermal superhydrophobic phase change wood with highly efficient anti‐/deicing performance is developed. The abundant and unique anisotropic wood channels coated with polypyrrole (PPy) nanoparticles, combining with phase change materials (PCMs), results in superior energy conversion performance in the longitudinal channels and increased loading capacity for PCMs. Meanwhile, the superhydrophobic carbon nanotubes (CNT) coatings endow wood with excellent encapsulation and durable stability. Owing to the photo/electro‐thermal efficiency up to 91.1% and 96.7% under low‐temperature conditions, the photo/electro‐thermal superhydrophobic phase change wood exhibits high‐performance anti‐/deicing for application in wooden building roofs. This strategy offers potential toward developing sustainable, all‐weather and highly efficient anti‐/deicing.

Abstract Fast shape‐reconfiguration with large morphing amplitude is crucial for intelligent materials/structures that require tunable functions and adaptivity to different environments. However, the morphing strategies are rare in combining ultrafast speed, large amplitude, and high energy‐efficiency simultaneously. Herein, a class of 2D and 3D chiral mechanical metamaterials are proposed to tackle this challenge based on prestressed bistable metallic shells. The metamaterial is architected by cylindrical cores and slender bistable shells with an anti‐chiral arrangement. The bistable shell has a flat extended shape and a rolled‐up shape that can wrap on the connected cylindrical cores compatibly, and thus endow the metamaterials with a tunable morphing amplitude that can even extend to infinity. By experiments, simulations and theoretical modelling, it is demonstrated that the bistable shell can transform from the extended state to the rolled‐up state with a transitional speed of 7.56 m s −1 , which provides the 2D and 3D metamaterials with 25.38‐ and 101.14‐times body area/volume variation per second, respectively. Moreover, a smart trapper for capturing moving objects and a phononic structure with tunable band gaps are realized based on the metamaterials. This work provides a straightforward platform to design metamaterials and their derived systems with ultrafast and large‐amplitude shape‐reconfigurability.