Mitigating Lattice Distortion of High‑Voltage LiCoO_(2)via Core‑Shell Structure Induced by Cationic Heterogeneous Co‑Doping for Lithium‑Ion Batteries

Inactive elemental doping is commonly used to improve the structural stability of high-voltage layered transition-metal oxide cathodes.However,the one-step co-doping strategy usually results in small grain size since the low diffusivity ions such as Ti^(4+)will be concentrated on grain boundaries,which hinders the grain growth.In order to synthesize large single-crystal layered oxide cathodes,considering the different diffusivities of different dopant ions,we propose a simple two-step multi-element co-doping strategy to fabricate core–shell structured LiCoO_(2)(CS-LCO).In the current work,the high-diffusivity Al^(3+)/Mg^(2+)ions occupy the core of single-crystal grain while the low diffusivity Ti^(4+)ions enrich the shell layer.The Ti^(4+)-enriched shell layer(~12 nm)with Co/Ti substitution and stronger Ti–O bond gives rise to less oxygen ligand holes.In-situ XRD demonstrates the constrained contraction of c-axis lattice parameter and mitigated structural distortion.Under a high upper cut-off voltage of 4.6 V,the single-crystal CS-LCO maintains a reversible capacity of 159.8 mAh g^(−1)with a good retention of~89%after 300 cycles,and reaches a high specific capacity of 163.8 mAh g^(−1)at 5C.The proposed strategy can be extended to other pairs of low-(Zr^(4+),Ta^(5+),and W6+,etc.)and high-diffusivity cations(Zn^(2+),Ni^(2+),and Fe^(3+),etc.)for rational design of advanced layered oxide core–shell structured cathodes for lithium-ion batteries.

Lightweight and High-Performance Microwave Absorber Based on 2D WS2-RGO Heterostructures

Two-dimensional(2D)nanomaterials are categorized as a new class of microwave absorption(MA)materials owing to their high specific surface area and peculiar electronic properties.In this study,2D WS2-reduced graphene oxide(WS2-rGO)heterostructure nanosheets were synthesized via a facile hydrothermal process;moreover,their dielectric and MA properties were reported for the first time.Remarkably,the maximum reflection loss(RL)of the sample-wax composites containing 40 wt% WS2-rGO was-41.5 dB at a thickness of 2.7 mm;furthermore,the bandwidth where RL<-10 dB can reach up to 13.62 GHz(4.38-18 GHz).Synergistic mechanisms derived from the interfacial dielectric coupling and multiple-interface scattering after hybridization of WS2 with rGO were discussed to explain the drastically enhanced microwave absorption performance.The results indicate these lightweight WS2-rGO nanosheets to be potential materials for practical electromagnetic wave-absorbing applications.

Two‑Dimensional Black Phosphorus Nanomaterials:Emerging Advances in Electrochemical Energy Storage Science

Two-dimensional black phosphorus(2D BP),well known as phosphorene,has triggered tremendous attention since the first discovery in 2014.The unique puckered monolayer structure endows 2D BP intriguing properties,which facilitate its potential applications in various fields,such as catalyst,energy storage,sensor,etc.Owing to the large surface area,good electric conductivity,and high theoretical specific capacity,2D BP has been widely studied as electrode materials and significantly enhanced the performance of energy storage devices.With the rapid development of energy storage devices based on 2D BP,a timely review on this topic is in demand to further extend the application of 2D BP in energy storage.In this review,recent advances in experimental and theoretical development of 2D BP are presented along with its structures,properties,and synthetic methods.Particularly,their emerging applications in electrochemical energy storage,including Li−/K−/Mg−/Na-ion,Li–S batteries,and supercapacitors,are systematically summarized with milestones as well as the challenges.Benefited from the fast-growing dynamic investigation of 2D BP,some possible improvements and constructive perspectives are provided to guide the design of 2D BP-based energy storage devices with high performance.

Phase thermal stability and mechanical properties analyses of(Cr,Fe,V)–(Ta,W)multiple-based elemental system using a compositional gradient film

High-entropy alloys(HEAs)generally possess complex component combinations and abnormal properties.The traditional methods of investigating these alloys are becoming increasingly inefficient because of the unpredictable phase transformation and the combination of many constituents.The development of compositionally complex materials such as HEAs requires high-throughput experimental methods,which involves preparing many samples in a short time.Here we apply the high-throughput method to investigate the phase evolution and mechanical properties of novel HEA film with the compositional gradient of(Cr,Fe,V)-(Ta,W).First,we deposited the compositional gradient film by co-sputtering.Second,the mechanical properties and thermal stability of the(Cr0.33Fe0.33V0.33)x(Ta0.5W0.5)100−x(x=13-82)multiplebased-elemental(MBE)alloys were investigated.After the deposited wafer was annealed at 600℃for 0.5 h,the initial amorphous phase was transformed into a body-centered cubic(bcc)structure phase when x=33.Oxides were observed on the film surface when x was 72 and 82.Finally,the highest hardness of as-deposited films was found when x=18,and the maximum hardness of annealed films was found when x=33.

Effect of rare earth Nd^(3+)doping contents on physical,structural,and magnetic properties of Co-Ni spinel ferrite nanoparticles

Rare earth(RE)low doping has a significant influence on the structural,morphological,and magnetic properties of spinel ferrite nanoparticles.Therefore,rare earth neodymium(Nd)oxide was fully doped into spinel ferrite with a composition of Co_(0.80)Ni_(0.20)Nd_xFe_(2-x)O_4(x=0.0,0.05,0.10,and 0.15)using the sol-gel auto combustion method.Structural analysis of the synthesized samples with low doping of Nd using X-ray diffraction(XRD)and Rietveld refinements reveals a pure single-phase cubic structure,while the second phase appears with increasing content of Nd^(3+)at x=0.10 and 0.15.Scanning electron microscopy(SEM)and high-resolution transmission electron microscopy(HR-TEM)show well-shaped spherical grains within the nanometer range of the pure Co_(0.80)Ni_(0.20)Fe_(2)O_(4) sample,while larger grains with the presence of agglomeration are observed with doping of Nd^(3+)into the spinel ferrite nanoparticles.The magnetic parameters,i.e.,saturation magnetization M_s,remanence and magnetic moments exhibit decreasing trend with Nd^(3+)doping and M_s values are in 65.69 to 53.34 emu/g range.The coercivity of the Nd-doped Co-Ni spinel ferrite sample was calculated to be 1037.76 to~827.24 Oe.This work demonstrates remarkable improvements in the structural and magnetic characteristics of Nddoped Co-Ni spinel ferrite nanoparticles for multiple versatile applications.

Excited state biexcitons in monolayer WSe_(2)driven by vertically grown graphene nanosheets with high-density electron trapping edges

Interface engineering in atomically thin transition metal dichalcogenides(TMDs)is becoming an important and powerful technique to alter their properties,enabling new optoelectronic applications and quantum devices.Interface engineering in a monolayer WSe_(2)sample via introduction of high-density edges of standing structured graphene nanosheets(GNs)is realized.A strong photoluminescence(PL)emission peak from intravalley and intervalley trions at about 750 nm is observed at the room temperature,which indicated the heavily p-type doping of the monolayer WSe_(2)/thin graphene nanosheet-embedded carbon(TGNEC)film heterostructure.We also successfully triggered the emission of biexcitons(excited state biexciton)in a monolayer WSe_(2),via the electron trapping centers of edge quantum wells of a TGNEC film.The PL emission of a monolayer WSe_(2)/GNEC film is quenched by capturing the photoexcited electrons to reduce the electron-hole recombination rate.This study can be an important benchmark for the extensive understanding of light–matter interaction in TMDs,and their dynamics.

Mode-locked fiber laser of 3.5 μm using a single-walled carbon nanotube saturable absorber mirror

We report on a mid-infrared fiber laser that uses a single-walled carbon nanotube saturable absorber mirror to realize the mode-locking operation.The laser generates 3.5 μm ultra-short pulses from an erbium-doped fluoride fiber by utilizing a dual-wavelength pumping scheme.Stable mode-locking is achieved at the 3.5 μm band with a repetition rate of 25.2 MHz.The maximum average power acquired from the laser in the mode-locking regime is 25 mW.The experimental results indicate that the carbon nanotube is an effective saturable absorber for mode-locking in the mid-infrared spectral region.

Micro thermoplastic forming of a Pd-based metallic glass:theory and applications

Metallic glasses(MGs)are considered as the ideal materials for miniature fabrication because of their excellent micro thermoplastic forming ability in the supercooled liquid region.The understanding and controlling of micro filling process are fundamental for miniature fabrication and their applications,yet presently remain unresolved issues.A universal kinetic equation was proposed to describe the filling kinetics of viscous metallic glass supercooled liquid in micro molds with general cross sectional shapes by using a Pdbased MG as the modeling material and a series of potential applications based on the micro thermoplastic forming of the MG were developed.

Multiscale frictional behaviors of sp^(2) nanocrystallited carbon films with different ion irradiation densities

sp^(2) nanocrystallited carbon films with large nanocrystallite sizes,smooth surfaces,and relative high hardness were prepared with different ion irradiation densities regulated with the substrate magnetic coil current in an electron cyclotron resonance plasma sputtering system.Their multiscale frictional behaviors were investigated with macro pin‐on‐disk tribo‐tests and micro nanoscratch tests.The results revealed that,at an ion irradiation density of 16 mA/cm^(2),sp^(2) nanocrystallited carbon film exhibits the lowest friction coefficient and good wear resistant properties at both the macroscale and microscale.The film sliding against a Si_(3)N_(4) ball under a contact pressure of 0.57 GPa exhibited a low friction coefficient of 0.09 and a long wear life at the macroscale.Furthermore,the film sliding against a diamond tip under a contact pressure of 4.9 GPa exhibited a stable low friction coefficient of 0.08 with a shallow scratch depth at the microscale.It is suggested that sp^(2) nanocrystallites affect the frictional behaviors in the cases described differently.At the macroscale,the contact interface via the small real contact area and the sp^(2) nanocrystallited transfer layer dominated the frictional behavior,while the sp^(2) nanocrystallited structure in the film with low shear strength and high plastic resistivity,as well as the smooth surface morphology,decided the steady low nanoscratch properties at the microscale.These findings expand multiscale tribological applications of sp^(2) nanocrystallited carbon films.

Facile active control of a pulsed erbium-doped fiber laser using modulation depth tunable carbon nanotubes

Short pulsed fiber lasers have been widely made using single-walled carbon nanotubes as a saturable absorber(SA). However, most of the currently used devices can only operate in one determined operation state with an unchangeable modulation SA depth in the cavity, which significantly limits their application in photonic devices.In this paper, well-aligned carbon nanotube arrays are synthesized using zeolite AlPO_4-5 as a template, which features anisotropic optical absorption. The linear optical absorption of the as-synthesized carbon nanotube arrays can easily be tuned by adjusting a polarization controller, thus providing a tunable modulation depth for the carbon nanotube SA. By exploiting this SA in an erbium-doped fiber laser cavity, both Q-switched and modelocked pulsed lasers are achieved by simply adjusting a polarization controller under a fixed pump power of 330 mW. In addition, the repetition rate of the Q-switching and pulse duration of the mode-locking can be tuned according to the variation of modulation depth. Moreover, soliton molecules can be obtained when the modulation depth of the SA is 4.5%.

In-situ TEM studies on stick–slip friction characters of sp^(2) nanocrystallited carbon films

Carbon films with two different kinds of sp^(2) nanocrystallited structure were investigated to study the stick–slip friction with the in-situ and ex-situ tests.In-situ transmission electron microscope(TEM)observation and nanofriction tests revealed that the origins of stick and slip varied with shear stress and film deformation.At the stick stage,shear stress gradually increased with the contact strengthened until reached the shear strength to break the interfacial adhesion;at the slip stage,the shear stress decreased and accompanied with film deformation.During the sliding process,adhesive deformation resulted in the large stick–slip step while ploughing deformation led to a smoother step.Ex-situ nanofriction tests on a series of sp^(2) nanocrystallited carbon films with different irradiation energies showed the expected sliding behavior with the in-situ results.This study first clarified the mechanism of stick–slip friction with the in-situ TEM observation,which plays the important role for the micro and nano application of sp2 nanocrystallited carbon films.

Superhydrophobic,photo-sterilize,and reusable mask based on graphene nanosheet-embedded carbon(GNEC)film

The 2019 coronavirus disease(COVID-19)has affected more than 200 countries.Wearing masks can effectively cut off the virus spreading route since the coronavirus is mainly spreading by respiratory droplets.However,the common surgical masks cannot be reused,resulting in the increasing economic and resource consumption around the world.Herein,we report a superhydrophobic,photo-sterilize,and reusable mask based on graphene nanosheet-embedded carbon(GNEC)film,with high-density edges of standing structured graphene nanosheets.The GNEC mask exhibits an excellent hydrophobic ability(water contact angle:157.9°)and an outstanding filtration efficiency with 100%bacterial filtration efficiency(BFE).In addition,the GNEC mask shows the prominent photo-sterilize performance,heating up to 110℃quickly under the solar illumination.These high performances may facilitate the combat against the COVID-19 outbreaks,while the reusable masks help reducing the economic and resource consumption.

Current-carrying friction in carbon coated ball bearing

In this work,we proposed a method for coating the whole surfaces of bearing balls uniformly by carbon film with a rotatable ball clamp.We studied the carbon/carbon friction with a self-designed currentcarrying ball bearing friction test system.A notable and instant friction force drop of 28%and significant carbon film wear alleviation were found when currents were applied.By using TEM-,SEM-,and EDS-analysis,special carbon stacks with a mixture of large wear particles and oxide were found in the wear areas under current applied condition.We elucidated the current-carrying friction mechanisms as follows:(1)wear particles formation;(2)wear particles charged by tribomicroplasma;(3)formation of surface passivated carbon stacks under electric force;(4)sliding between passivated carbon surfaces.This work may facilitate the development of novel solid-lubricated ball bearings and lay some foundations for current-carrying rolling friction.

Generation and modulation of multiple 2D bulk photovoltaic effects in space-time reversal asymmetric 2H-FeCl_(2)

The two-dimensional(2D)bulk photovoltaic effect(BPVE)is a cornerstone for future highly efficient 2D solar cells and optoelectronics.The ferromagnetic semiconductor 2H-FeCl_(2) is shown to realize a new type of BPVE in which spatial inversion(P),time reversal(T),and space−time reversal(PT)symmetries are broken(PT-broken).Using density functional theory and perturbation theory,we show that 2H-FeCl_(2) exhibits giant photocurrents,photo-spin-currents,and photo-orbital-currents under illumination by linearly polarized light.The injection-like and shift-like photocurrents coexist and propagate in different directions.The material also demonstrates substantial photoconductance,photo-spin-conductance,and photo-orbital-conductance,with magnitudes up to 4650(nm·μA/V^(2)),4620[nm·μA/V^(2)/(2e)],and 6450(nm·μA/V^(2)/e),respectively.Furthermore,the injection-currents,shift-spin-currents,and shift-orbital-currents can be readily switched via rotating the magnetizations of 2H-FeCl_(2).These results demonstrate the superior performance and intriguing control of a new type of BPVE in 2H-FeCl_(2).

High-power mid-infrared femtosecond master oscillator power amplifier Er:ZBLAN fiber laser system

High-power femtosecond mid-infrared(MIR)lasers are of vast importance to both fundamental research and applications.We report a high-power femtosecond master oscillator power amplifier laser system consisting of a singlemode Er:ZBLAN fiber mode-locked oscillator and pre-amplifier followed by a large-mode-area Er:ZBLAN fiber main amplifier.The main amplifier is actively cooled and bidirectionally pumped at 976 nm,generating a slope efficiency of 26.9%.Pulses of 8.12 W,148 fs at 2.8μm with a repetition rate of 69.65 MHz are achieved.To the best of our knowledge,this is the highest average power ever achieved from a femtosecond MIR laser source.Such a compact ultrafast laser system is promising for a wide range of applications,such as medical surgery and material processing.

Bone-inspired(GNEC/HAPAAm)hydrogel with fatigue-resistance for use in underwater robots and highly piezoresistive sensors

A novel bone-inspired fatigue-resistant hydrogel with excellent mechanical and piezoresistive properties was developed,and it exhibited great potential as a load and strain sensor for underwater robotics and daily monitoring.The hydrogel was created by using the high edge density and aspect ratio of graphene nanosheet-embedded carbon(GNEC)nanomaterials to form a three-dimensional conductive network and prevent the expansion of microcracks in the hydrogel system.Multiscale progressive enhancement of the organic hydrogels(micrometer scale)was realized with inorganic graphene nanosheets(nanometer scale).The graphene nanocrystals inside the GNEC film exhibited good electron transport properties,and the increased distances between the graphene nanocrystals inside the GNEC film caused by external forces increased the resistance,so the hydrogel was highly sensitive and suitable for connection to a loop for sensing applications.The hydrogels obtained in this work exhibited excellent mechanical properties,such as tensile properties(strain up to 1685%)and strengths(stresses up to 171 kPa),that make them suitable for use as elastic retraction devices in robotics and provide high sensitivities(150 ms)for daily human monitoring.

Design,modeling and experiments of broadband tristable galloping piezoelectric energy harvester

Galloping based piezoelectric energy harvester is a kind of micro-environmental energy harvesting device based on flowinduced vibrations.A novel tristable galloping-based piezoelectric energy harvester is constructed by introducing a nonlinear magnetic force on the traditional galloping-based piezoelectric energy harvester.Based on Euler-Bernoulli beam theory and Kirchhoff’s law,the corresponding aero-electromechanical model is proposed and validated by a series of wind tunnel experiments.The parametric study is performed to analyse the response of the tristable galloping-based piezoelectric energy harvester.Numerical results show that comparing with the galloping-based piezoelectric energy harvester,the mechanism of the tristable galloping-based piezoelectric energy harvester is more complex.With the increase of a wind speed,the vibration of the bluff body passes through three branches:intra-well oscillations,chaotic oscillations,and inter-well oscillations.The threshold wind speed of the presented harvester for efficiently harvesting energy is 1.0 m/s,which is decreased by 33% compared with the galloping-based piezoelectric energy harvester.The maximum output power of the presented harvester is 0.73 mW at 7.0 m/s wind speed,which is increased by 35.3%.Compared with the traditional galloping-based piezoelectric energy harvester,the presented tristable galloping-based piezoelectric energy harvester has a better energy harvesting performance from flow-induced vibrations.

Construction of multiple interfaces and dielectric/magnetic heterostructures in electromagnetic wave absorbers with enhanced absorption performance:A review

The construction of structures with multiple interfaces and dielectric/magnetic heterostructures enables the design of materials with unique physical and chemical properties,which has aroused intensive interest in scientific and technological fields.Especially,for electromagnetic(EM)wave absorption,enhanced interface polarization and improved impedence match with high Snoek's limitation could be achieved by multiple interfaces and dielectric/magnetic heterostructures,respectively,which are benificial to high-efficiency electromagnetic wave absorption(EWA).However,by far,the principles in the design or construction of structures with multiple interfaces and dielectric/magnetic heterostructures,and the relationships between those structures or heterostructures and their EWA performance have not been fully summarized and reviewed.This article aims to provide a timely review on the research progresses of high-efficency EM wave absorbers with multiple interfaces and dielectric/magnetic heterostructures,focusing on various promising EWA materials.Particularly,EM attenuation mechanisms in those structures with multiple interfaces and dielectric/magnetic heterostructures are discussed and generalized.Furthermore,the changllenges and future developments of EM wave absorbers based on those structures are proposed.

0.33 mJ, 104.3 W dissipative soliton resonance based on a figure-of-9 double-clad Tm-doped oscillator and an all-fiber MOPA system

We demonstrate, for the first time, to the best of our knowledge, an all-fiber figure-of-9 double-clad Tm-doped fiber laser operating in the dissipative soliton resonance(DSR) regime. Stable mode-locked rectangular pulses are obtained by using the nonlinear amplifying loop mirror(NALM) technique. A long spool of high-nonlinearity fiber(HNLF) and a segment of SMF-28 fiber are used to enhance the nonlinearity of the NALM loop and to obtain a large all-anomalous regime. Output power and pulse energy are further boosted by using a three-stage master oscillator power amplifier(MOPA) system. At the maximum pump power, average output power of up to 104.3 W with record pulse energy of 0.33 mJ is achieved with a 2 μm DSR-based MOPA system.

High-temperature friction behavior of amorphous carbon coating in glass molding process

In the glass molding process,the sticking reaction and fatigue wear between the glass and mold hinder the service life and functional application of the mold at the elevated temperature.To improve the chemical inertness and anti-friction properties of the mold,an amorphous carbon coating was synthesized on the tungsten carbide-cobalt(WC–8Co)substrate by magnetron sputtering.The friction behavior between the glass and carbon coating has a significant influence on the functional protection and service life of the mold.Therefore,the glass ring compression tests were conducted to measure the friction coefficient and friction force of the contact interface between the glass and amorphous carbon coating at the high temperature.Meanwhile,the detailed characterization of the amorphous carbon coating was performed to study the microstructure evolution and surface topography of the amorphous carbon coating during glass molding process by scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS),Ramon spectroscopy,and atomic force microscope(AFM).The results showed that the amorphous carbon coating exhibited excellent thermal stability,but weak shear friction strength.The friction coefficient between the glass and coating depended on the temperature.Besides,the service life of the coating was governed by the friction force of the contact interface,processing conditions,and composition diffusion.This work provides a better understanding of the application of carbon coatings in the glass molding.