A new robust bio-inspired route by using lysozyme aqueous solution for surface modification on 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX)was described in this paper.HMX crystals were coated by in situ phase transitio...A new robust bio-inspired route by using lysozyme aqueous solution for surface modification on 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX)was described in this paper.HMX crystals were coated by in situ phase transition of lysozyme(PTL)molecules.The HMX decorated by PTL was characterized by SEM,XRD,FTIR and XPS,demonstrating a dense core-shell coating layer.The coverage of lysozyme on HMX crystal was calculated by the ratio of sulfur content.The surface coverage increased from 60.5% to 93.5% when the content of PTL was changed from 0.5 wt% to 2.0 wt%,indicating efficient coating.The thermal stability of HMX was investigated by in situ XRD and DSC.The thermal phase transition temperature of HMX(β to δ phase)was delayed by 42℃ with 2.0 wt% PTL coating,which prevented HMX from thermal damage and sensitivity by the effect of PTL coating.After heating at 215℃,large cracks appeared in the naked HMX crystal,while the PTL coated HMX still maintained intact,with the impact energy of HMX dropped dramatically from 5 J to 2 J.However,the impact energy of HMX with 1.0 wt% and 2.0 wt% coating content(HMX@PTL-1.0 and HMX@PTL-2.0)was unchanged(5 J).Present results potentially enable large-scale fabrication of polymorphic energetic materials with outstanding thermal stability by novel lysozyme coating.展开更多
Improving the energy conversion efficiency in metallic fuel(e.g.,Al)combustion is always desirable but challenging,which often involves redox reactions of aluminum(Al)with various mixed oxidizing environments.For inst...Improving the energy conversion efficiency in metallic fuel(e.g.,Al)combustion is always desirable but challenging,which often involves redox reactions of aluminum(Al)with various mixed oxidizing environments.For instance,Al-O reaction is the most common pathway to release limited energy while Al-F reaction has received much attentions to enhance Al combustion efficiency.However,microscopic understanding of the Al-O/Al-F reaction dynamics remains unsolved,which is fundamentally necessary to further improve Al combustion efficiency.In this work,for the first time,Al-O/Al-F reaction dynamic effects on the combustion of aluminum nanoparticles(n-Al)in oxygen/fluorine containing environments have been revealed via reactive molecular dynamics(RMD)simulations meshing together combustion experiments.Three RMD simulation systems of Al core/O_(2)/HF,n-Al/O_(2)/HF,and n-Al/O_(2)/CF4 with oxygen percentage ranging from 0%to 100%have been performed.The n-Al combustion in mixed O_(2)/CF_4 environments have been conducted by constant volume combustion experiments.RMD results show that Al-O reaction exhibits kinetic benefits while Al-F reaction owns thermodynamic benefits for n-Al combustion.In n-Al/O_(2)/HF,Al-O reaction gives faster energy release rate than Al-F reaction(1.1 times).The optimal energy release efficiency can be achieved with suitable oxygen percentage of 10%and 50%for n-Al/O_(2)/HF and n-Al/O_(2)/CF_4,respectively.In combustion experiments,90%of oxygen percentage can optimally enhance the peak pressure,pressurization rate and combustion heat.Importantly,Al-O reaction prefers to occur on the surface regions while Al-F reaction prefers to proceed in the interior regions of n-Al,confirming the kinetic/thermodynamic benefits of Al-O/Al-F reactions.The synergistic effect of Al-O/Al-F reaction for greatly enhancing n-Al combustion efficiency is demonstrated at atomicscale,which is beneficial for optimizing the combustion performance of metallic fuel.展开更多
In recent years,nanogenerators(NGs)have attracted wide attention in the energy field,among which triboelectric nanogenerators(TENGs)have shown superior performance.Multiple reports of electrospinning(ES)-based TENGs h...In recent years,nanogenerators(NGs)have attracted wide attention in the energy field,among which triboelectric nanogenerators(TENGs)have shown superior performance.Multiple reports of electrospinning(ES)-based TENGs have been reported,but there is a lack of deep analysis of the designing method from microstructure,limiting the creative of new ES-based TENGs.Most TENGs use polymer materials to achieve corresponding design,which requires structural design of polymer materials.The existing polymer molding design methods include macroscopic molding methods,such as injection,compression,extrusion,calendering,etc.,combined with liquid-solid changes such as soluting and melting;it also includes micro-nano molding technology,such as melt-blown method,coagulation bath method,ES method,and nanoimprint method.In fact,ES technology has good controllability of thickness dimension and rich means of nanoscale structure regulation.At present,these characteristics have not been reviewed.Therefore,in this paper,we combine recent reports with some microstructure regulation functions of ES to establish a more general TENGs design method.Based on the rich microstructure research results in the field of ES,much more new types of TENGs can be designed in the future.展开更多
By employing three reflecting volume Bragg gratings, a near-infrared 4-channel spectral-beam-combining system is demonstrated to present 720 W combined power with a combining efficiency of 94.7%. The combined laser be...By employing three reflecting volume Bragg gratings, a near-infrared 4-channel spectral-beam-combining system is demonstrated to present 720 W combined power with a combining efficiency of 94.7%. The combined laser beam is near-diffraction-limited with a beam factor M^2-1.54. During this 4-channel beam-combining process, no special active cooling measures are used to evaluate the volume Bragg gratings as combining elements are under the higher power laser operation. Thermal expansion and period distortion are verified in a 2 k W 2-channel beam-combining process, and the heat issue in the transmission case is found to be more remarkable than that in the diffraction e-se. Transmitted and diffracted beams experience wave-front aberrations with different degrees, thus leading to distinct beam deterioration.展开更多
The Cu2O and Au-doped Cu2O films are prepared on MgO （001） substrates by pulsed laser deposition. The X-ray photoelectron spectroscopy proves that the films are of Au-doped Cu2O. The optical absorption edge decrease...The Cu2O and Au-doped Cu2O films are prepared on MgO （001） substrates by pulsed laser deposition. The X-ray photoelectron spectroscopy proves that the films are of Au-doped Cu2O. The optical absorption edge decreases by 1.6% after Au doping. The electronic and optical properties of pure and Au-doped cuprite Cu2O films are investigated by the first principles. The calculated results indicate that Cu2O is a direct band-gap semiconductor. The scissors operation of 1.64 eV has been carried out. After correcting, the band gaps for pure and Au doped Cu2O are about 2.17 eV and 2.02 eV, respectively, decreasing by 6.9%. All of the optical spectra are closely related to the dielectric function. The optical spectrum red shift corresponding to the decreasing of the band gap, and the additional absorption, are observed in the visible region for Au doped Cu2O film. The experimental results are generally in agreement with the calculated results. These results indicate that Au doping could become one of the more important factors influencing the photovoltaic activity of Cu2O film.展开更多
In terahertz communication,the direct frequency conversion structure in which orthogonal mixer is the main frequency conversion unit,makes engineers get into trouble of in-phase(I)branch and quadrature(Q)branch imbala...In terahertz communication,the direct frequency conversion structure in which orthogonal mixer is the main frequency conversion unit,makes engineers get into trouble of in-phase(I)branch and quadrature(Q)branch imbalance,carrier wave leakage,etc.These damages result in system performance tremendous degrades.We proposed a semiblind method to estimate the I/Q imbalance of THz orthogonal modulator,based on predefined preamble and pilot symbols for quadrature amplitude modulation(QAM).In this paper,a transmitter with Y band quadrature mixer and 20Gbps base-band signal has been tested.The bandwidth of the baseband signal was 7GHz,and the modulation type was 16QAM.By this method,7dB improvement of the system’s symbol Mean Square Error(MSE)has been got.That means the proposed method can be used to eliminate the I/Q imbalance effectively.展开更多
Recently generation of strong magnetic(B)fields has been demonstrated in capacitor coils heated by high power laser pulses[S.Fujioka et al.,Sci.Rep.3,1170(2013)].This paper will present a direct measurement of B field...Recently generation of strong magnetic(B)fields has been demonstrated in capacitor coils heated by high power laser pulses[S.Fujioka et al.,Sci.Rep.3,1170(2013)].This paper will present a direct measurement of B field generated with an open-ended coil target driven by a nanosecond laser pulse using ultrafast proton radiography.The radiographs are analyzed with particle-tracing simulations.The B field at the coil center is inferred to be ~50 T at an irradiance of ~5×10^(14) W·cm^(-2).The B field generation is attributed to the background cold electron flow pointing to the laser focal spot,where a target potential is induced due to the escape of energetic electrons.展开更多
Electromagnetic pulses(EMPs)produced by the interaction of a TW femtosecond laser with solid targets at the Compact Laser Plasma Accelerator(CLAPA)are measured and interpreted.The statistical results confirm that the ...Electromagnetic pulses(EMPs)produced by the interaction of a TW femtosecond laser with solid targets at the Compact Laser Plasma Accelerator(CLAPA)are measured and interpreted.The statistical results confirm that the intensities of the EMPs are closely related to both target material and thickness.The signal of the titanium target is more abundant than that of the copper target with the same thickness,and the intensity of EMP is positively correlated with the target thickness for aluminium foil.With the boosted EMP radiations,the energy of accelerated protons is also simultaneously enhanced.In addition,EMPs emitted from the front of the target exceed those from the rear,which are also pertinent to the specific target position.The resonant waveforms in the target chamber are analyzed using the fast Fourier transform,and the local resonance and the attenuation lead to changes of the frequency spectra of EMPs with variation of detecting positions,which is well supported by the modeling results.The findings are beneficial to gaining insight into the mechanism of EMP propagation in a typical target chamber and providing more information for EMP shielding design.展开更多
Size and morphology are critical factors in determining the electrochemical performance of the supercapacitor materials,due to the manifestation of the nanosize effect.Herein,different nanostructures of the CrN materi...Size and morphology are critical factors in determining the electrochemical performance of the supercapacitor materials,due to the manifestation of the nanosize effect.Herein,different nanostructures of the CrN material are prepared by the combination of a thermal-nitridation process and a template technique.High-temperature nitridation could not only transform the hexagonal Cr_(2)O_(3)into cubic CrN,but also keep the template morphology barely unchanged.The obtained CrN nanostructures,including(i)hierarchical microspheres assembled by nanoparticles,(ii)microlayers,and(iii)nanoparticles,are studied for the electrochemical supercapacitor.The CrN microspheres show the best specific capacitance(213.2 F/g),cyclic stability(capacitance retention rate of 96%after 5000 cycles in 1-mol/L KOH solution),high energy density(28.9 Wh/kg),and power density(443.4 W/kg),comparing with the other two nanostructures.Based on the impedance spectroscopy and nitrogen adsorption analysis,it is revealed that the enhancement arised mainly from a high-conductance and specific surface area of CrN microspheres.This work presents a general strategy of fabricating controllable CrN nanostructures to achieve the enhanced supercapacitor performance.展开更多
Shock compression experiments on a new kind of 47Zr45Ti5Al3V alloys at pressures between 28 and 200 GPa are performed using a two-stage light gas gun.The Hugoniot data are obtained by combining the impedance-match met...Shock compression experiments on a new kind of 47Zr45Ti5Al3V alloys at pressures between 28 and 200 GPa are performed using a two-stage light gas gun.The Hugoniot data are obtained by combining the impedance-match method and the electrical probe technique.The relationship between the shock wave velocity Us and particle velocity up can be described linearly by U_(s)=4.324(±0.035)+1.177(±0.012)up.No obvious evidence of phase transition is found in the shock compression pressure range.The calculated U_(s)-up relationship obtained from the additive principle is different from the experimental data,indicating that theα→βphase transition occurs below 28 GPa.The Grüneisen parameterγobtained from the experimental data can be expressed byγ=1.277(ρ0/ρ).The zero-pressure bulk modulus B0s=97.96 GPa and its pressure derivative B_(0s)=3.68.The P–V–T equation of state for 47Zr45Ti5Al3V is given using the Vinet equation of state to describe the cold curve and the Debye model for the thermal contributions.展开更多
Chemical inclusions significantly alter shock responses of crystalline explosives in macroscale gap experiments but their microscale dynamics origin remains unclear.Herein shock-induced energy localization,overall phy...Chemical inclusions significantly alter shock responses of crystalline explosives in macroscale gap experiments but their microscale dynamics origin remains unclear.Herein shock-induced energy localization,overall physical responses,and reactions in a-1,3,5-trinitro-1,3,5-triazinane(a-RDX)crystal entrained various chemical inclusions were investigated by the multi-scale shock technique implemented in the reactive molecular dynamics method.Results indicated that energy localization and shock reaction were affected by the intrinsic factors within chemical inclusions,i.e.,phase states,chemical compositions,and concentrations.The atomic origin of chemical-inclusions effects on energy localization is dependent on the dynamics mechanism of interfacial molecules with free space volume,which includes homogeneous intermolecular compression,interfacial impact and shear,and void collapse and jet.As introducing various chemical inclusions,the initiation of those dynamics mechanisms triggers diverse decay rates of bulk RDX molecules and hereby impacts on growth speeds of final reactions.Adding chemical inclusions can reduce the effectiveness of the void during the shock impacting.Under the shockwave velocity of 9 km/s,the parent RDX decay rate in RDX entrained amorphous carbon decreases the most and is about one fourth of that in RDX with a vacuum void,and solid HMX and TATB inclusions are more reactive than amorphous carbon but less reactive than dry air or acetone inclusions.The lessdense shocking system denotes the greater increases in local temperature and stress,the faster energy liberation,and the earlier final reaction into equilibrium,revealing more pronounced responses to the present intense shockwave.The quantitative models associated with the relative system density(RD_(sys))were proposed for indicating energy-localization mechanisms and evaluating initiation safety in the shocked crystalline explosive.RD_(sys)is defined by the density ratio of defective RDX to perfect crystal after dynamics relaxation and reveals the global density characteristic in shocked systems filled with chemical inclusions.When RD_(sys)is below 0.9,local hydrodynamic jet initiated by void collapse dominates upon energy localization instead of interfacial impact.This study sheds light on novel insights for understanding the shock chemistry and physical-based atomic origin in crystalline explosives considering chemical-inclusions effects.展开更多
Alumina supports modified by lanthanum （La） and barium （Ba） were prepared by peptization. Catalysts with different KOH contents supported on modified alumina were prepared by impregnation method. Various technique...Alumina supports modified by lanthanum （La） and barium （Ba） were prepared by peptization. Catalysts with different KOH contents supported on modified alumina were prepared by impregnation method. Various techniques, including N2 adsorption-desorption （Brunauer-Emmet-Teller method, BET）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and fourier transform infrared absorption spectroscopy （FT-IR）. Catalytic activity for microalgae oil conversion to methyl ester via transesterification was evaluated and analyzed by GC-MS and GC. BET results showed that the support possessed high specific surface area, suitable pore volume and pore size distribution. Activity results indicated that the catalyst with 25 wt% KOH showed the best activity for microalgae oil conversion. XRD and SEM results revealed that Al-O-K compound was the active phase for microalgae oil conversion. The agglomeration and changing of pore structure should be the main reasons for the catalyst deactivation when KOH content was higher than 30 wt%.展开更多
In the context of the gradual popularity of electric vehicles(EVs),the development of lithium battery systems with high energy density and power density is regarded as the foremost way to improve the range of EVs.LiNi...In the context of the gradual popularity of electric vehicles(EVs),the development of lithium battery systems with high energy density and power density is regarded as the foremost way to improve the range of EVs.LiNi_(1-x-y)Co_(x)Mn_(y)O_(2)(NCM)cathodes have been the focus of researchers due to their high energy density,excellent power performance,and low-temperature resistance.However,the elaboration of the decay mechanism of NCM cathode based on lithium metal batteries(LMBs)is still being restricted to the primary level.In the past decades,the development and application of advanced in-situ characterization tools have facilitated researchers'understanding of the internal operation mechanism of batteries during charging and discharging.In this minireview,the latest progress of in-situ observation of the NCM cathode by X-ray diffraction(XRD),fourier transform infrared(FT-IR)spectroscopy,Raman spectroscopy,atomic force microscopy(AFM),transmission electron microscope(TEM),optical microscope,and other characterization tools is summarized.The mechanisms of structural degradation,cathode-electrolyte interfaces(CEIs)composition,and dynamic changes of NCM,electrolyte breakdown,and gas production are elaborated.Finally,based on the existing research progress,the opportunities and challenges for future in-situ characterization technology in the study of the mechanism of LMBs are discussed in depth.Therefore,the purpose of this minireview is to summarize recent work that focuses on the outstanding application of in-situ characterization techniques in the mechanistic study of LMBs,and pointing the way to the future development of high energy density and power density LMBs systems.展开更多
Volatile elements—such as carbon, hydrogen, sulfur, nitrogen, and halogens—are minor constituents of Earth’s deep interior. Despite their low abundances, deep volatiles mediate major Earth processes, including magm...Volatile elements—such as carbon, hydrogen, sulfur, nitrogen, and halogens—are minor constituents of Earth’s deep interior. Despite their low abundances, deep volatiles mediate major Earth processes, including magma generation, volcanism, mantle convection, and plate tectonics, which control the exchange of volatiles between Earth’s deep interior and its surface. Over geological time, deep volatiles play critical, primary roles in governing energy resources, natural hazards, atmospheric composition, climate, and planetary habitability. Human activities after the industrial revolution have played an impactful, secondary role, and the resulting risk of add-on effects that could lead to irreversible runaway catastrophes has greatly increased.展开更多
Low-noise terahertz(THz)radiation over 100 MV/cm generation by a linearly-polarized relativistic laser pulse interacting with a near-critical-density(NCD)plasma slab is studied by theory and particle-in-cell(PIC)simul...Low-noise terahertz(THz)radiation over 100 MV/cm generation by a linearly-polarized relativistic laser pulse interacting with a near-critical-density(NCD)plasma slab is studied by theory and particle-in-cell(PIC)simulations.A theoretical model is established to examine the dipole-like radiation emission.The THz radiation is attributed to the singlecycle low-frequency surface current,which is longitudinally constrained by the quasi-equilibrium established by the laser ponderomotive force and the ponderomotively induced electrostatic force.Through theoretical analysis,the spatiotemporal characteristics,polarization property of the THz radiation,and the relation between the radiation strength with the initial parameters of driving laser and plasma are obtained,which are in good consistence with the PIC simulation results.Furthermore,it is found by PIC simulations that the generation of thermal electrons can be suppressed within the appropriate parameter regime,resulting in a clear THz radiation waveform.The appropriate parameter region is given for generating a low-noise intense THz radiation with peak strength reaching 100 MV/cm,which could find potential applications in nonlinear THz physics.展开更多
Smoothed particle hydrodynamics （SPH） is a Lagrangian, meshfree particle method and has been widely applied to diffe- rent areas in engineering and science. Since its original extension to modeling free surface flow...Smoothed particle hydrodynamics （SPH） is a Lagrangian, meshfree particle method and has been widely applied to diffe- rent areas in engineering and science. Since its original extension to modeling free surface flows by Monaghan in 1994, SPH has been gradually developed into an attractive approach for modeling viscous incompressible fluid flows. This paper presents an overview on the recent progresses of SPH in modeling viscous incompressible flows in four major aspects which are closely related to the computational accuracy of SPH simulations. The advantages and disadvantages of different SPH particle approximation sche- mes, pressure field solution approaches, solid boundary treatment algorithms and particle adapting algorithms are described and analyzed. Some new perspectives and fuRtre trends in SPH modeling of viscous incompressible flows are discussed.展开更多
Our scanning tunneling microscopy (STM) study observes, for the first time, twin domain boundary (TDB) formations on the surface of WTe2 single crystal, which is glued by solidifying indium to Si substrate. In these T...Our scanning tunneling microscopy (STM) study observes, for the first time, twin domain boundary (TDB) formations on the surface of WTe2 single crystal, which is glued by solidifying indium to Si substrate. In these TDB regions, a large inhomogeneous strain field, especially a critical shear strain of about 7%, is observed by geometric phase analysis. This observation does not obey the old believe that a small mechanical stress is sufficient to drive thermally-induced TDB formations in two-dimensional materials. To resolve the contradiction, we perform density functional theory calculations combined with elasticity theory analysis, which show that TDBs on WTe2 are entirely displacement-induced, for which a critical strain is necessary to overcome the onset barrier.展开更多
The effects of gamma ray(γ-ray)radiation and electron beam(e-beam)radiation on Rayleigh scattering coefficient in single-mode fiber are experimentally investigated.Utilizing an optical time domain reflectometry(OTDR)...The effects of gamma ray(γ-ray)radiation and electron beam(e-beam)radiation on Rayleigh scattering coefficient in single-mode fiber are experimentally investigated.Utilizing an optical time domain reflectometry(OTDR),the power distribution curves of the irradiated fibers are obtained to retrieve the corresponding radiation-induced attenuation(RIA).Based on the backscattering power levels and the measured RIAs,the Rayleigh scattering coefficients can be characterized quantitatively for each fiber sample.Under the given radiation conditions,Rayleigh scattering coefficients have been changed very little while RIAs have been changed significantly.Furthermore,simulations have been implemented to verify the validity of the measured Rayleigh scattering coefficient,including the splicing points.展开更多
Over the past decades,there has been an intensive quest for theoretical studies and experimental detection of polynitrogen species (e.g.,N4,N5^+,N8,cyclo-N5^-,and polymeric nitrogen,etc.)that are potentiaUy stable in ...Over the past decades,there has been an intensive quest for theoretical studies and experimental detection of polynitrogen species (e.g.,N4,N5^+,N8,cyclo-N5^-,and polymeric nitrogen,etc.)that are potentiaUy stable in the condensed phase [1-4].As a class of representative polynitrogen species,cyclo-pentazolate (cyclo-N5^-)com- pounds have received significant interest from synthetic chemists.Despite traditional arylpentazole compounds were discovered in 1956 [5],the experimental synthesis of stable cyclo-N;species has encountered great difficulties for subsequent decades.展开更多
The exploration of low-cost and metal-free nanozymes with oxidase-mimicking activity is highly desired due to their attractive properties and potential applications.However,it is still challenging and remains unexploi...The exploration of low-cost and metal-free nanozymes with oxidase-mimicking activity is highly desired due to their attractive properties and potential applications.However,it is still challenging and remains unexploited to fully realize oxidase-like nanozyme in the emerging covalent organic frameworks(COFs)due to their polymeric nature and weak photoelectric activity.We herein report the first example of the preparation and oxidase-mimicking activity of novel ultrathin two-dimensional(2D)COF(termed as TTPA-COF)nanosheets.The ultrathin TTPA-COF nanosheets with hexagonal layered structure are constructed from two flexible photoactive(diarylamino)benzene-based linkers,and exhibit remarkable catalytic activity toward the oxidation of 3,3',5,5'-tetramethylbenzidine(TMB)in the presence of O_(2) due to their large specific surface areas and abundant active sites.Moreover,it is worth noting that the nanozyme activity could be regulated by external light irradiation.Based on the oxidasemimicking activity of TTPA-COF nanosheets,a green colorimetric sensor is proposed for the sensitive and selective determination of glutathione(GSH)in a wide linear range of 0.5–40μM with a detection limit of 0.5μM.This work reported here would open new avenues for the exploration of low-cost and high-efficiency nanozymes,as well as extend the application of 2D COF nanosheets in the fields of catalysis and sensing.展开更多
基金the China National Nature Science Foundation(Grant No.12102404)。
文摘A new robust bio-inspired route by using lysozyme aqueous solution for surface modification on 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX)was described in this paper.HMX crystals were coated by in situ phase transition of lysozyme(PTL)molecules.The HMX decorated by PTL was characterized by SEM,XRD,FTIR and XPS,demonstrating a dense core-shell coating layer.The coverage of lysozyme on HMX crystal was calculated by the ratio of sulfur content.The surface coverage increased from 60.5% to 93.5% when the content of PTL was changed from 0.5 wt% to 2.0 wt%,indicating efficient coating.The thermal stability of HMX was investigated by in situ XRD and DSC.The thermal phase transition temperature of HMX(β to δ phase)was delayed by 42℃ with 2.0 wt% PTL coating,which prevented HMX from thermal damage and sensitivity by the effect of PTL coating.After heating at 215℃,large cracks appeared in the naked HMX crystal,while the PTL coated HMX still maintained intact,with the impact energy of HMX dropped dramatically from 5 J to 2 J.However,the impact energy of HMX with 1.0 wt% and 2.0 wt% coating content(HMX@PTL-1.0 and HMX@PTL-2.0)was unchanged(5 J).Present results potentially enable large-scale fabrication of polymorphic energetic materials with outstanding thermal stability by novel lysozyme coating.
基金support by the National Natural Science Foundation of China(NSFC,Grant Nos.12002324,12372341,12172342)。
文摘Improving the energy conversion efficiency in metallic fuel(e.g.,Al)combustion is always desirable but challenging,which often involves redox reactions of aluminum(Al)with various mixed oxidizing environments.For instance,Al-O reaction is the most common pathway to release limited energy while Al-F reaction has received much attentions to enhance Al combustion efficiency.However,microscopic understanding of the Al-O/Al-F reaction dynamics remains unsolved,which is fundamentally necessary to further improve Al combustion efficiency.In this work,for the first time,Al-O/Al-F reaction dynamic effects on the combustion of aluminum nanoparticles(n-Al)in oxygen/fluorine containing environments have been revealed via reactive molecular dynamics(RMD)simulations meshing together combustion experiments.Three RMD simulation systems of Al core/O_(2)/HF,n-Al/O_(2)/HF,and n-Al/O_(2)/CF4 with oxygen percentage ranging from 0%to 100%have been performed.The n-Al combustion in mixed O_(2)/CF_4 environments have been conducted by constant volume combustion experiments.RMD results show that Al-O reaction exhibits kinetic benefits while Al-F reaction owns thermodynamic benefits for n-Al combustion.In n-Al/O_(2)/HF,Al-O reaction gives faster energy release rate than Al-F reaction(1.1 times).The optimal energy release efficiency can be achieved with suitable oxygen percentage of 10%and 50%for n-Al/O_(2)/HF and n-Al/O_(2)/CF_4,respectively.In combustion experiments,90%of oxygen percentage can optimally enhance the peak pressure,pressurization rate and combustion heat.Importantly,Al-O reaction prefers to occur on the surface regions while Al-F reaction prefers to proceed in the interior regions of n-Al,confirming the kinetic/thermodynamic benefits of Al-O/Al-F reactions.The synergistic effect of Al-O/Al-F reaction for greatly enhancing n-Al combustion efficiency is demonstrated at atomicscale,which is beneficial for optimizing the combustion performance of metallic fuel.
基金supported by the National Natural Science Foundation of China(12104249,11804313 and 11847135)the Youth Innovation Team Project of Shandong Provincial Education Department(2021KJ013,2020KJN015)by State Key Laboratory of Bio-Fibers and Eco-Textiles(Qingdao University)(GZRC202011&ZKT46)。
文摘In recent years,nanogenerators(NGs)have attracted wide attention in the energy field,among which triboelectric nanogenerators(TENGs)have shown superior performance.Multiple reports of electrospinning(ES)-based TENGs have been reported,but there is a lack of deep analysis of the designing method from microstructure,limiting the creative of new ES-based TENGs.Most TENGs use polymer materials to achieve corresponding design,which requires structural design of polymer materials.The existing polymer molding design methods include macroscopic molding methods,such as injection,compression,extrusion,calendering,etc.,combined with liquid-solid changes such as soluting and melting;it also includes micro-nano molding technology,such as melt-blown method,coagulation bath method,ES method,and nanoimprint method.In fact,ES technology has good controllability of thickness dimension and rich means of nanoscale structure regulation.At present,these characteristics have not been reviewed.Therefore,in this paper,we combine recent reports with some microstructure regulation functions of ES to establish a more general TENGs design method.Based on the rich microstructure research results in the field of ES,much more new types of TENGs can be designed in the future.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11474257 and 61605183
文摘By employing three reflecting volume Bragg gratings, a near-infrared 4-channel spectral-beam-combining system is demonstrated to present 720 W combined power with a combining efficiency of 94.7%. The combined laser beam is near-diffraction-limited with a beam factor M^2-1.54. During this 4-channel beam-combining process, no special active cooling measures are used to evaluate the volume Bragg gratings as combining elements are under the higher power laser operation. Thermal expansion and period distortion are verified in a 2 k W 2-channel beam-combining process, and the heat issue in the transmission case is found to be more remarkable than that in the diffraction e-se. Transmitted and diffracted beams experience wave-front aberrations with different degrees, thus leading to distinct beam deterioration.
文摘The Cu2O and Au-doped Cu2O films are prepared on MgO （001） substrates by pulsed laser deposition. The X-ray photoelectron spectroscopy proves that the films are of Au-doped Cu2O. The optical absorption edge decreases by 1.6% after Au doping. The electronic and optical properties of pure and Au-doped cuprite Cu2O films are investigated by the first principles. The calculated results indicate that Cu2O is a direct band-gap semiconductor. The scissors operation of 1.64 eV has been carried out. After correcting, the band gaps for pure and Au doped Cu2O are about 2.17 eV and 2.02 eV, respectively, decreasing by 6.9%. All of the optical spectra are closely related to the dielectric function. The optical spectrum red shift corresponding to the decreasing of the band gap, and the additional absorption, are observed in the visible region for Au doped Cu2O film. The experimental results are generally in agreement with the calculated results. These results indicate that Au doping could become one of the more important factors influencing the photovoltaic activity of Cu2O film.
基金National Key RD Program of China Grant(2018YFB1801504)the President Funding of China Academy of Engineering Physics with No.YZJJLX2018009.
文摘In terahertz communication,the direct frequency conversion structure in which orthogonal mixer is the main frequency conversion unit,makes engineers get into trouble of in-phase(I)branch and quadrature(Q)branch imbalance,carrier wave leakage,etc.These damages result in system performance tremendous degrades.We proposed a semiblind method to estimate the I/Q imbalance of THz orthogonal modulator,based on predefined preamble and pilot symbols for quadrature amplitude modulation(QAM).In this paper,a transmitter with Y band quadrature mixer and 20Gbps base-band signal has been tested.The bandwidth of the baseband signal was 7GHz,and the modulation type was 16QAM.By this method,7dB improvement of the system’s symbol Mean Square Error(MSE)has been got.That means the proposed method can be used to eliminate the I/Q imbalance effectively.
基金supported by the National Basic Research Program of China(Grant No.2013CBA01501)the National Nature Science Foundation of China(Grant Nos.11135012,11520101003 and 11375262)the National High Technology Research and Development Program of China.
文摘Recently generation of strong magnetic(B)fields has been demonstrated in capacitor coils heated by high power laser pulses[S.Fujioka et al.,Sci.Rep.3,1170(2013)].This paper will present a direct measurement of B field generated with an open-ended coil target driven by a nanosecond laser pulse using ultrafast proton radiography.The radiographs are analyzed with particle-tracing simulations.The B field at the coil center is inferred to be ~50 T at an irradiance of ~5×10^(14) W·cm^(-2).The B field generation is attributed to the background cold electron flow pointing to the laser focal spot,where a target potential is induced due to the escape of energetic electrons.
基金supported by the National Natural Science Foundation of China(Grant Nos.11975037 and 11921006)the National Grand Instrument Project of China(Grant Nos.2019YFF01014400 and 2019YFF01014404)。
文摘Electromagnetic pulses(EMPs)produced by the interaction of a TW femtosecond laser with solid targets at the Compact Laser Plasma Accelerator(CLAPA)are measured and interpreted.The statistical results confirm that the intensities of the EMPs are closely related to both target material and thickness.The signal of the titanium target is more abundant than that of the copper target with the same thickness,and the intensity of EMP is positively correlated with the target thickness for aluminium foil.With the boosted EMP radiations,the energy of accelerated protons is also simultaneously enhanced.In addition,EMPs emitted from the front of the target exceed those from the rear,which are also pertinent to the specific target position.The resonant waveforms in the target chamber are analyzed using the fast Fourier transform,and the local resonance and the attenuation lead to changes of the frequency spectra of EMPs with variation of detecting positions,which is well supported by the modeling results.The findings are beneficial to gaining insight into the mechanism of EMP propagation in a typical target chamber and providing more information for EMP shielding design.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11904299,U1930124,and 11804312)China Academy of Engineering Physics(CAEP)Foundation(Grant No.2018AB02)。
文摘Size and morphology are critical factors in determining the electrochemical performance of the supercapacitor materials,due to the manifestation of the nanosize effect.Herein,different nanostructures of the CrN material are prepared by the combination of a thermal-nitridation process and a template technique.High-temperature nitridation could not only transform the hexagonal Cr_(2)O_(3)into cubic CrN,but also keep the template morphology barely unchanged.The obtained CrN nanostructures,including(i)hierarchical microspheres assembled by nanoparticles,(ii)microlayers,and(iii)nanoparticles,are studied for the electrochemical supercapacitor.The CrN microspheres show the best specific capacitance(213.2 F/g),cyclic stability(capacitance retention rate of 96%after 5000 cycles in 1-mol/L KOH solution),high energy density(28.9 Wh/kg),and power density(443.4 W/kg),comparing with the other two nanostructures.Based on the impedance spectroscopy and nitrogen adsorption analysis,it is revealed that the enhancement arised mainly from a high-conductance and specific surface area of CrN microspheres.This work presents a general strategy of fabricating controllable CrN nanostructures to achieve the enhanced supercapacitor performance.
基金Supported by the National Basic Research Program of China under Grant No 2010CB731600the Specialized Research Project for the Protection against Space Debris of China under Grant Nos kjsp06209 and kjsp06210.
文摘Shock compression experiments on a new kind of 47Zr45Ti5Al3V alloys at pressures between 28 and 200 GPa are performed using a two-stage light gas gun.The Hugoniot data are obtained by combining the impedance-match method and the electrical probe technique.The relationship between the shock wave velocity Us and particle velocity up can be described linearly by U_(s)=4.324(±0.035)+1.177(±0.012)up.No obvious evidence of phase transition is found in the shock compression pressure range.The calculated U_(s)-up relationship obtained from the additive principle is different from the experimental data,indicating that theα→βphase transition occurs below 28 GPa.The Grüneisen parameterγobtained from the experimental data can be expressed byγ=1.277(ρ0/ρ).The zero-pressure bulk modulus B0s=97.96 GPa and its pressure derivative B_(0s)=3.68.The P–V–T equation of state for 47Zr45Ti5Al3V is given using the Vinet equation of state to describe the cold curve and the Debye model for the thermal contributions.
基金the financial support from National Natural Science Foundation of China(Grant Nos.11872119,12172051,and 11972329)Natural Science Foundation of Hubei Province(Grant No.2021CFB120)。
文摘Chemical inclusions significantly alter shock responses of crystalline explosives in macroscale gap experiments but their microscale dynamics origin remains unclear.Herein shock-induced energy localization,overall physical responses,and reactions in a-1,3,5-trinitro-1,3,5-triazinane(a-RDX)crystal entrained various chemical inclusions were investigated by the multi-scale shock technique implemented in the reactive molecular dynamics method.Results indicated that energy localization and shock reaction were affected by the intrinsic factors within chemical inclusions,i.e.,phase states,chemical compositions,and concentrations.The atomic origin of chemical-inclusions effects on energy localization is dependent on the dynamics mechanism of interfacial molecules with free space volume,which includes homogeneous intermolecular compression,interfacial impact and shear,and void collapse and jet.As introducing various chemical inclusions,the initiation of those dynamics mechanisms triggers diverse decay rates of bulk RDX molecules and hereby impacts on growth speeds of final reactions.Adding chemical inclusions can reduce the effectiveness of the void during the shock impacting.Under the shockwave velocity of 9 km/s,the parent RDX decay rate in RDX entrained amorphous carbon decreases the most and is about one fourth of that in RDX with a vacuum void,and solid HMX and TATB inclusions are more reactive than amorphous carbon but less reactive than dry air or acetone inclusions.The lessdense shocking system denotes the greater increases in local temperature and stress,the faster energy liberation,and the earlier final reaction into equilibrium,revealing more pronounced responses to the present intense shockwave.The quantitative models associated with the relative system density(RD_(sys))were proposed for indicating energy-localization mechanisms and evaluating initiation safety in the shocked crystalline explosive.RD_(sys)is defined by the density ratio of defective RDX to perfect crystal after dynamics relaxation and reveals the global density characteristic in shocked systems filled with chemical inclusions.When RD_(sys)is below 0.9,local hydrodynamic jet initiated by void collapse dominates upon energy localization instead of interfacial impact.This study sheds light on novel insights for understanding the shock chemistry and physical-based atomic origin in crystalline explosives considering chemical-inclusions effects.
基金supported by the Institute of Chemical Materials Foundation of CAEP(No.626010937)
文摘Alumina supports modified by lanthanum （La） and barium （Ba） were prepared by peptization. Catalysts with different KOH contents supported on modified alumina were prepared by impregnation method. Various techniques, including N2 adsorption-desorption （Brunauer-Emmet-Teller method, BET）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and fourier transform infrared absorption spectroscopy （FT-IR）. Catalytic activity for microalgae oil conversion to methyl ester via transesterification was evaluated and analyzed by GC-MS and GC. BET results showed that the support possessed high specific surface area, suitable pore volume and pore size distribution. Activity results indicated that the catalyst with 25 wt% KOH showed the best activity for microalgae oil conversion. XRD and SEM results revealed that Al-O-K compound was the active phase for microalgae oil conversion. The agglomeration and changing of pore structure should be the main reasons for the catalyst deactivation when KOH content was higher than 30 wt%.
基金supports by the National Natural Science Foundation of China(Nos.U20A2072,52072352,and 21875226)the Foundation for the Youth S&T Innovation Team of Sichuan Province(No.2020JDTD0035)Tianfu Rencai Plan.
文摘In the context of the gradual popularity of electric vehicles(EVs),the development of lithium battery systems with high energy density and power density is regarded as the foremost way to improve the range of EVs.LiNi_(1-x-y)Co_(x)Mn_(y)O_(2)(NCM)cathodes have been the focus of researchers due to their high energy density,excellent power performance,and low-temperature resistance.However,the elaboration of the decay mechanism of NCM cathode based on lithium metal batteries(LMBs)is still being restricted to the primary level.In the past decades,the development and application of advanced in-situ characterization tools have facilitated researchers'understanding of the internal operation mechanism of batteries during charging and discharging.In this minireview,the latest progress of in-situ observation of the NCM cathode by X-ray diffraction(XRD),fourier transform infrared(FT-IR)spectroscopy,Raman spectroscopy,atomic force microscopy(AFM),transmission electron microscope(TEM),optical microscope,and other characterization tools is summarized.The mechanisms of structural degradation,cathode-electrolyte interfaces(CEIs)composition,and dynamic changes of NCM,electrolyte breakdown,and gas production are elaborated.Finally,based on the existing research progress,the opportunities and challenges for future in-situ characterization technology in the study of the mechanism of LMBs are discussed in depth.Therefore,the purpose of this minireview is to summarize recent work that focuses on the outstanding application of in-situ characterization techniques in the mechanistic study of LMBs,and pointing the way to the future development of high energy density and power density LMBs systems.
文摘Volatile elements—such as carbon, hydrogen, sulfur, nitrogen, and halogens—are minor constituents of Earth’s deep interior. Despite their low abundances, deep volatiles mediate major Earth processes, including magma generation, volcanism, mantle convection, and plate tectonics, which control the exchange of volatiles between Earth’s deep interior and its surface. Over geological time, deep volatiles play critical, primary roles in governing energy resources, natural hazards, atmospheric composition, climate, and planetary habitability. Human activities after the industrial revolution have played an impactful, secondary role, and the resulting risk of add-on effects that could lead to irreversible runaway catastrophes has greatly increased.
基金the National Natural Science Foundation of China(Grant Nos.11774430,12075157,11775202,and 12175310)the Scientific Research Foundation of Hunan Provincial Education Department(Grant No.20A042).
文摘Low-noise terahertz(THz)radiation over 100 MV/cm generation by a linearly-polarized relativistic laser pulse interacting with a near-critical-density(NCD)plasma slab is studied by theory and particle-in-cell(PIC)simulations.A theoretical model is established to examine the dipole-like radiation emission.The THz radiation is attributed to the singlecycle low-frequency surface current,which is longitudinally constrained by the quasi-equilibrium established by the laser ponderomotive force and the ponderomotively induced electrostatic force.Through theoretical analysis,the spatiotemporal characteristics,polarization property of the THz radiation,and the relation between the radiation strength with the initial parameters of driving laser and plasma are obtained,which are in good consistence with the PIC simulation results.Furthermore,it is found by PIC simulations that the generation of thermal electrons can be suppressed within the appropriate parameter regime,resulting in a clear THz radiation waveform.The appropriate parameter region is given for generating a low-noise intense THz radiation with peak strength reaching 100 MV/cm,which could find potential applications in nonlinear THz physics.
基金Project supported by the National Natural Science Foun-dation of China(Grant Nos.11172306,U1530110)the Institu-te of Systems Engineering,China Academy of Engineering Physics(Grant No.2013KJZ01)
文摘Smoothed particle hydrodynamics （SPH） is a Lagrangian, meshfree particle method and has been widely applied to diffe- rent areas in engineering and science. Since its original extension to modeling free surface flows by Monaghan in 1994, SPH has been gradually developed into an attractive approach for modeling viscous incompressible fluid flows. This paper presents an overview on the recent progresses of SPH in modeling viscous incompressible flows in four major aspects which are closely related to the computational accuracy of SPH simulations. The advantages and disadvantages of different SPH particle approximation sche- mes, pressure field solution approaches, solid boundary treatment algorithms and particle adapting algorithms are described and analyzed. Some new perspectives and fuRtre trends in SPH modeling of viscous incompressible flows are discussed.
基金We thank the Ministry of Science and Technology of China (Nos. 2016YFA0301003 and 2016YFA0300403)the National Natural Science Foundation of China (Nos. 11521404, 11634009, U1632102, 11504230, 11674222, 11574202, 11674226, 11574201, 11655002, and U1632272) for partial support+4 种基金W Y. X. was supported by the National Science Foundation Award (No. DMR-1305293)S. B.乙 was supported by the US Department of Energy (DOE)(No. DESC0002623)The supercomputer time sponsored by National Energy aesearch Scientific Computing Center (NERSC) under DOE contract (No. DE-AC02-05CH11231)the Center for Computational Innovations (CCI) at Rensselaer Polytechnic Institute (RPI) are also acknowledgedThis project has been supported by a grant &om Science and Technology Commission of Shanghai Municipality (No. 16DZ2260200) and the Strategic Priority Research Program of Chinese Academy of Sciences (No. XDB28000000).
文摘Our scanning tunneling microscopy (STM) study observes, for the first time, twin domain boundary (TDB) formations on the surface of WTe2 single crystal, which is glued by solidifying indium to Si substrate. In these TDB regions, a large inhomogeneous strain field, especially a critical shear strain of about 7%, is observed by geometric phase analysis. This observation does not obey the old believe that a small mechanical stress is sufficient to drive thermally-induced TDB formations in two-dimensional materials. To resolve the contradiction, we perform density functional theory calculations combined with elasticity theory analysis, which show that TDBs on WTe2 are entirely displacement-induced, for which a critical strain is necessary to overcome the onset barrier.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.41527805 and 61635005)Sichuan Youth Science and Technology Foundation(Grant No.2016JQ0034)+3 种基金the 111 Project(Grant No.B14039)The Romanian authors acknowledge the support of the Romanian Executive Agency for Higher Education,Research,Development and Innovation Funding(Grant No.UEFISCDI),under the contract“Sensor Systems for Secure Operation of Critical Installations”.G.Peng acknowledges the support by Science and Technology Commission of Shanghai Municipality,China(Grant Nos.SKLSFO2015-01 and 15220721500)by the Hisilicon Innovation Research Program(HIRP)(Grant No.HO2017050001CZ).
文摘The effects of gamma ray(γ-ray)radiation and electron beam(e-beam)radiation on Rayleigh scattering coefficient in single-mode fiber are experimentally investigated.Utilizing an optical time domain reflectometry(OTDR),the power distribution curves of the irradiated fibers are obtained to retrieve the corresponding radiation-induced attenuation(RIA).Based on the backscattering power levels and the measured RIAs,the Rayleigh scattering coefficients can be characterized quantitatively for each fiber sample.Under the given radiation conditions,Rayleigh scattering coefficients have been changed very little while RIAs have been changed significantly.Furthermore,simulations have been implemented to verify the validity of the measured Rayleigh scattering coefficient,including the splicing points.
基金supported by the National Natural Science Foundation of China (21602211 and 11472251)the Thousand Talents Plan (Youth)+1 种基金Dvelopment Foundation of CAEP (2015B0302057 and 2015B0302056)the Science Challenge Project (TZ2018004)
文摘Over the past decades,there has been an intensive quest for theoretical studies and experimental detection of polynitrogen species (e.g.,N4,N5^+,N8,cyclo-N5^-,and polymeric nitrogen,etc.)that are potentiaUy stable in the condensed phase [1-4].As a class of representative polynitrogen species,cyclo-pentazolate (cyclo-N5^-)com- pounds have received significant interest from synthetic chemists.Despite traditional arylpentazole compounds were discovered in 1956 [5],the experimental synthesis of stable cyclo-N;species has encountered great difficulties for subsequent decades.
基金supported by the financial support from the National Natural Science Foundation of China(NSFC)(Nos.21976166,22006122,and 21405144)the research funding of“Leading Innovative and Entrepreneur Team Introduction Program of Zhejiang”(No.2020R01002)+4 种基金the Class D of Qianjiang Talent Program(No.ZD20011250001)the Science Challenge Project(No.TZ2016004)he Project of State Key Laboratory of Environment-friendly Energy Materials(No.18zd320303)the Scientific Research Starting Foundation for Returned Overseas Chinese Scholars of Sichuan Province(No.19zd3200)support from the Opening Project of Jiangsu Province Engineering Research Center of Agricultural Breeding Pollution Control and Resource(No.2021ABPCR004).
文摘The exploration of low-cost and metal-free nanozymes with oxidase-mimicking activity is highly desired due to their attractive properties and potential applications.However,it is still challenging and remains unexploited to fully realize oxidase-like nanozyme in the emerging covalent organic frameworks(COFs)due to their polymeric nature and weak photoelectric activity.We herein report the first example of the preparation and oxidase-mimicking activity of novel ultrathin two-dimensional(2D)COF(termed as TTPA-COF)nanosheets.The ultrathin TTPA-COF nanosheets with hexagonal layered structure are constructed from two flexible photoactive(diarylamino)benzene-based linkers,and exhibit remarkable catalytic activity toward the oxidation of 3,3',5,5'-tetramethylbenzidine(TMB)in the presence of O_(2) due to their large specific surface areas and abundant active sites.Moreover,it is worth noting that the nanozyme activity could be regulated by external light irradiation.Based on the oxidasemimicking activity of TTPA-COF nanosheets,a green colorimetric sensor is proposed for the sensitive and selective determination of glutathione(GSH)in a wide linear range of 0.5–40μM with a detection limit of 0.5μM.This work reported here would open new avenues for the exploration of low-cost and high-efficiency nanozymes,as well as extend the application of 2D COF nanosheets in the fields of catalysis and sensing.
