查看更多>>摘要：Neuromorphic computing is known for its effi-cient computational speed,low latency,and reduced power consumption,which is considered a pivotal technology to overcome the von Neumann bottleneck.Artificial synapses are an indispensable component of neuromorphic compu-tational artificial neural networks.To guarantee effective and precise processing of optical signals,it must have a high responsivity,detectivity,and the ability to adapt to various environments.Here,a synaptic transistor based on the HfS2/VO2 heterojunction with a responsivity of 8.6 × 103 A·W-1 and a detectivity of 1.26 × 1014 Jones at 405 nm laser was reported.Meanwhile,the typical synaptic behavior was successfully simulated,including postsynaptic currents(PSCs),the transition from short-term plasticity(STP)to long-term plasticity(LTP).When VO2 converts from the semiconductor state to the metal state,the HfS2/VO2 heterojunction transforms into a Schottky heterojunction from a Type Ⅱ heterojunction with temperature.What's important,the heterojunction still exhibits excellent responsivity and detectivity,as well as stability of synaptic properties.In addition,the classical Pavlovian conditioning experiment is simulated under different laser intensity to study the brain's associative learning behavior.The results demonstrate that the HfS2/VO2 heterojunction synapse exhibits significant respon-sivity and detectivity and is adaptable to high-temperature environments,showing great potential for neuromorphic computational applications.
查看更多>>摘要：Catalytic reduction of dinitrogen to ammonia under mild conditions remains an attractive topic for the purpose of lowering energy consumption.Three-atom metal clusters have been proved an ideal model to explore highly efficient catalysts taking advantage of unique geo-metric/electronic structures and cooperative active sites.Here a study of N2 activation and reduction on seventeen bimetallic Nb2M(M=Sc to Cu,and Y to Ag)clusters was reported.Three key processes for ammonia fixation(namely nitrogen activation,hydrogenation,and ammonia desorption)are fully studied,and three preferred systems(Nb2Ni,Nb2Rh and Nb2Pd)are highlighted with out-standing catalytic performance.The d-σ and d-π*orbital hybridizations between these metal clusters and N2 were demonstrated and the internal association with the N ≡ N bond activation was unveiled.By examining the ammonia synthesis on four chosen Nb2M clusters(M=Fe,Ni,Rh and Pd),it can be elucidated that the distal pathway is more favorable than the alternative pathway in these systems.This work not only clarifies the N2 reduction on the bimetallic Nb2M clusters,but also guides efficient bimetallic catalyst design.
查看更多>>摘要：Nonprecious-metal-group single-metal-atom catalysts with bifunctional catalytic capabilities toward the oxygen evolution reaction(OER)and oxygen reduction reaction(ORR)are highly sought after in energy-conver-sion and storage technology.However,producing renew-able and sustainable energy sources remains challenging.Currently,single-transition metal atoms anchored on π-πconjugated two-dimensional(2D)graphitic carbon nitride substrates form π-d conjugated conductive channels that enhance the overall electrocatalytic activity.Herein,first-principles calculations were carried out to design and demonstrate a novel macropore graphitic carbon nitride(g-C10N3)as a promising 2D electrocatalyst substrate to support single-transition metal(TM,from Sc to Au).The"donation-acceptance"charge interaction in the TM-N2 moiety effectively balances the adsorption strength of oxygenated intermediates in Ni@g-C10N3 and Rh@g-C10N3,making them effective bifunctional OER/ORR electrocatalysts with IrO2/Pt-beyond overpotentials being as low as 0.39/0.38 V and 0.54/0.44 V,respectively.Additionally,they possess high stability and conductivity and are less susceptible to oxidation and corrosion under working conditions.This guarantees high activity under ambient conditions.Then,the origin of the OER/ORR activity of TM@g-C10N3 is explained using multilevel descriptors:intrinsic φ,Bader charge,integral crystal orbital Hamilton population(ICOHP),bond length,and d-band center(εd).In particular,for optimal Ni@g-C10N3,the clear hybridization between the Ni-d orbital and surface O-p orbital causes the paired electrons to occupy the bonding orbitals.This enables OH*to be adsorbed on the Ni@g-C10N3,thereby achieving the highest catalytic per-formance.
查看更多>>摘要：Developing luminescent metal-organic frame-works(MOFs)capable of high-efficiency Fe3+sensing has aroused great attraction in the fields of biology,chemistry,etc.However,previous solvothermal methods are limited by organic solvent usage,time consuming,high pressure,and high-energy consumption.Herein,we propose the waste-to-MOF strategy towards the scale-up production of La-MOF nanoparticles through the ball milling of recycled poly(-ethylene terephthalate)(PET)bottles and La(NO3)3·6H2O.PET goes on alkaline hydrolysis to form 1,4-benzenedicar-boxylic acid sodium salt(Na2BDC)and ethylene glycol by ball milling.Subsequently,BDC reacts with La3+to form La-MOF.The as-prepared La-MOF crystal nanoparticles possess a rod-like morphology with the size of few hundred nanometers.Additionally,La-MOF nanoparticles display high selectivity and sensitivity for Fe3+detection.The quenching constant and limit of detection are 5.29 × 103(mol·L-1)-1 and 0.147 pmol·L-1,respectively,thus sur-passing many advanced Fe3+sensors.According to the result of density functional theory,the high Fe3+detection per-formance of La-MOF is related to the complexing of Fe3+with La-MOF,which leads to the gradual dissociation of the coordination bond between terephthalic acid and La3+.It is anticipated that the mechanochemistry milling-based waste-to-MOF strategy provides a new platform for the massive production of functional MOFs in a green manner.
查看更多>>摘要：Vortex beams have attracted great attention due to their promising applications in the fields of high-ca-pacity optical communication,optical micromanipulation,and quantum information processing.Here,we demon-strate vortex beams with flexible control of the topological charge and modes in a carbon dots random laser for the first time.Vortex beams with different types,including the Laguerre-Gaussian(LG),Bessel-Gaussian(BG),LG-su-perposition,and polarized vortex beams with topological charges up to 50,have been successfully achieved.More-over,vortex beams can be well realized in carbon dots random lasers with different emission wavelengths cover-ing from 465 to 612 nm.This work would not only enrich the types of vortex laser,especially for solution-process-able lasers,but also provide a new route to realizing multi-color and wavelength-tunable vortex lasers.
查看更多>>摘要：High-temperature thin-film sensors(TFSs)often suffer from inadequate tolerance to elevated tem-peratures.In this study,an innovative approach is pre-sented to fabricate in situ integrated TFSs with a core-shell structure on alloy components using coaxial multi-ink printing technique.This method replaces traditional layer-by-layer(LbL)deposition and LbL sintering processes and achieves simplified one-step manufacturing.The coaxial TFS includes a conductive Pt core for conducting and sensing and a dielectric shell for electrical isolation and high-temperature protection.The coaxial Pt resistance grid demonstrates excellent high-temperature stability,with a resistance drift rate of only 0.08％·h-1 at 800 ℃,signifi-cantly lower than traditional Pt TFSs.By employing this method,a Pt thin-film strain gauge(TFSG)is fabricated that boasts remarkable high-temperature electromechanical properties.This effectively addresses the problem of sen-sitivity degradation experienced by traditional LbL Pt TFSGs when subjected to high temperatures.We demon-strate the system integration potential of the technique by printing and verifying the functionality of a long-path thin-film resistance grid on turbine blades,which can withstand butane flame up to～1300 ℃.These results showcase the potential of core-shell structure of the coaxial TFS for high-temperature applications,providing a novel approach to develop high-performance TFS beyond traditional mul-tilayer structure.
查看更多>>摘要：Spin logics have emerged as a promising ave-nue for the development of logic-in-memory architectures.In particular,the realization of XOR spin logic gates using a single spin-orbit torque device shows great potential for low-power stateful logic circuits in the next generation.In this study,we successfully obtained the XOR logic gate by utilizing a spin-orbit torque device with a lateral interface,which was created by local ion implantation in the Ta/Pt/Co/Ta Hall device exhibiting perpendicular magnetic ani-sotropy.The angle of the lateral interface is set at 45° relative to the current direction,leading to the competition between symmetry breaking and current-driven Néel-type domain wall motion.Consequently,the field-free magnetic switching reversed is realized by the same sign of current amplitude at this interface.Based on this field-free mag-netic switching behavior,we successfully proposed an XOR logic gate that could be implemented using only a single spin-orbit torque Hall device.This study provides a potentially viable approach toward efficient spin logics and in-memory computing architectures.
查看更多>>摘要：Arsenic materials have attracted great attention due to their unique properties.However,research con-cerning iron-arsenic(Fe-As)alloys is very scarce due to the volatility of As at low temperature and the high melting point of Fe.Herein,a new Fe-As alloy was obtained by mechanical alloying(MA)followed by vacuum hot-pres-sed sintering(VHPS).Moreover,a systematic study was carried out on the microstructural evolution,phase com-position,leaching toxicity of As,and physical and mechanical properties of Fe-As alloys with varying weight fractions of As(20％,25％,30％,35％,45％,55％,65％,and 75％).The results showed that pre-alloyed metallic powders(PAMPs)have a fine grain size and specific super-saturated solid solution after MA,which could effectively improve the mechanical properties of Fe-As alloys by VHPS.A high density(＞7.350 g·cm-3),low toxicity,and excellent mechanical properties could be obtained for Fe-As alloys sintered via VHPS by adding an appropriate amount of As,which is more valuable than commercial Fe-As products.The Fe-25％As alloy with low toxicity and a relatively high density(7.635 g·cm-3)provides an ultra-high compressive strength(1989.19 MPa),while the Fe-65％As alloy owns the maximum Vickers hardness(HV0.5 899.41).After leaching by the toxicity character-istic leaching procedure(TCLP),these alloys could still maintain good mechanical performance,and the strength-ening mechanisms of Fe-As alloys before and after leaching were clarified.Changes in the grain size,microstructure,and phase distribution induced significant differences in the compressive strength and hardness.
查看更多>>摘要：The CoCrFeMnNi high-entropy alloys(HEAs)with a(face-centered cubic)FCC structure has garnered considerable attention for its exceptional ductility and strain hardening ability.However,its yield strength is insufficient for structural applications.In this study,strengthening mechanisms in these HEAs were investi-gated to gain insight into the mechanical properties according to alloy powder size.Moreover,we present a novel approach to achieve both high strength and high ductility through the creation of a bimodal structure con-sisting of both coarse and fine grains via gas atomization and spark plasma sintering processes.A bimodally struc-tured HEA prepared with a mass ratio of 2:8 between coarse particles(75-106 μm)and fine particles(≤ 25 μm)yielded optimal results,with a strength of 491.95 MPa and elongation of 19.64％.This strength value represents an～41％increase compared with the sample that dis-played a fine single microstructure(347.08 MPa for yield strength).The strength enhancement was attributed to the prevention of plastic deformation initiation from the fine particles during deformation.This innovative approach to the creation of HEAs with bimodal structures shows pro-mise for various applications,such as structural compo-nents that require a combination of high strength and high ductility.
查看更多>>摘要：Nb-Si-based alloys show great potential to sur-pass the widely used Ni-based superalloys.The element Sr is widely applied in aluminum and magnesium alloys,but reports about the effects of Sr on Nb-Si-based alloys are quite rare.So,Nb-Si-based alloys with nominal composi-tions of Nb-15Si-24Ti-4Cr-2Al-2Hf-0/0.05/0.15Sr(at％)were prepared by directional solidification and heat treat-ment.The microstructural characterization and room tem-perature fracture toughness of Nb-Si-based alloy were systematically investigated.Results show that all these alloys consist of Nb5Si3 phase embedded within Nb solid solution(Nbss)matrix.The Nb5Si3 phase becomes refined and more discontinuous after adding minor Sr.As for the fracture toughness,0.05 at％and 0.15 at％Sr additions do not cause significant change.The discontinuous and refin-ing mechanism of Sr element was studied,and the analysis of toughness decreasing with Sr addition reveals that the size of Nbss phase plays a crucial role in determining the fracture toughness.
万方数据
维普