Recently, a laser-induced breakdown spectroscopic （LIBS） system has been developed for in situ measurements of the chemical compositions of plasma facing materials （PFMs） in the Experimental Advanced Superconducti...Recently, a laser-induced breakdown spectroscopic （LIBS） system has been developed for in situ measurements of the chemical compositions of plasma facing materials （PFMs） in the Experimental Advanced Superconducting Tokamak （EAST）. In this study, a LIBS system, which was used in a similar optical configuration to the in situ LIBS system in EAST, has been developed to investigate the spatial distribution of PFM elements at 10-4 Pa. The aim of this study was to understand the nature of the spatial distribution of atoms or ions of different elements in the plasma plume and optimize the signal to background ratio for the in situ LIBS diagnosis in EAST. The spatial profiles of the LIBS signals of C, Si, Mo and the continuous background were measured. Moreover, the influence of laser spot size and laser energy density on the LIBS signals of C, Si, Mo and H was also investigated. The results show that the distribution of the C, Si and Mo peaks＇ intensities first increased and then decreased from the center to the edge of the plasma plume. There was a maximum value at R ≈ 1.5 mm from the center of the plasma plume. This work aims to improve the understanding of ablating plasma dynamics in very low pressure environments and give guidance to optimize the LIBS system in the EAST device.展开更多
Silicene, a monolayer of silicon atoms arranged in a honeycomb lattice, has been undergoing rapid development in recent years due to its superior electronic properties and its compatibility with mature silicon-based s...Silicene, a monolayer of silicon atoms arranged in a honeycomb lattice, has been undergoing rapid development in recent years due to its superior electronic properties and its compatibility with mature silicon-based semiconductor technology. The successful synthesis of silicene on several substrates provides a solid foundation for the use of silicene in future microelectronic devices. In this review, we discuss the growth mechanism of silicene on an Ag(111) surface, which is crucial for achieving high quality silicene. Several critical issues related to the electronic properties of silicene are also summarized, including the point defect effect, substrate effect, intercalation of alkali metal, and alloying with transition metals.展开更多
Functionally graded materials （FGM） have been widely used in many industries such as aerospace, energy and electronics. In this experimental study of fabricating FGM, an approach was developed to prepare AI/Si FGM u...Functionally graded materials （FGM） have been widely used in many industries such as aerospace, energy and electronics. In this experimental study of fabricating FGM, an approach was developed to prepare AI/Si FGM using power ultrasonic separation method. Material sample with continuously changing composition and performance/properties was successfully produced. Results showed that the microstructure of the FGM sample transited, from its top to bottom, from the hypereutectic structure with a large quantity of primary Si gradually to the eutectic, and finally to the hypoeutectic with numerous primary AI dendrites. The distribution of primary Si and microhardness of the FGM sample also presented graded characteristics, resulting that the wear resistance of the FGM sample decreased from top to bottom. Preliminary discussion was made on the mechanism of the formation of AI/Si FGM.展开更多
Laser-induced breakdown spectroscopy （LIBS） is a powerful analytical tool for real- time diagnostics and detection of multiple elements deposited at the first wall of magnetically confined plasma ft^sion devices. Re...Laser-induced breakdown spectroscopy （LIBS） is a powerful analytical tool for real- time diagnostics and detection of multiple elements deposited at the first wall of magnetically confined plasma ft^sion devices. Recently, we have tested LIBS in our laboratory for application to in situ real-time diagnostics in the fusion device EAST. In this study, we applied polarization- resolved LIBS （PR-LIBS） to reduce the background continuum and enhance the resolution and sensitivity of LIBS. We used aluminium （A1） （as a substitute for Be） and the first wall materials tungsten （W） and molybdenum （Mo） to investigate polarized continuum emission and signal-to- background ratio （SBR）. A Nd：YAG laser with first, second and third harmonics was used to produce plasma. The effects of the laser polarization plane, environmental pressure and polarizer detection angle were investigated. The spectra obtained without using a polarizer （i.e. LIBS） were compared with those obtained with a polarizer （PR-LIBS）. Distribution of emission spectral intensity was observed to follow Malus＇ law with respect to variation in the angle of detection of the polarizer. The spectra obtained by PR-LIBS had a higher SBR and greater stability than those obtained by LIBS, thereby enhancing the reliability of LIBS for quantitative analyses. A comparison of A1, Mo and W showed that W exhibited a higher continuum with stronger polarization than the low-Z elements.展开更多
The unreacted equation of state（EOS） of energetic materials is an important thermodynamic relationship to characterize their high pressure behaviors and has practical importance. The previous experimental and theore...The unreacted equation of state（EOS） of energetic materials is an important thermodynamic relationship to characterize their high pressure behaviors and has practical importance. The previous experimental and theoretical works on the equation of state of several energetic materials including nitromethane, 1,3,5-trinitrohexahydro-1,3,5-triazine（RDX）,1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane（HMX）, hexanitrostilbene（HNS）, hexanitrohexaazaisowurtzitane（HNIW or CL-20）, pentaerythritol tetranitrate（PETN）, 2,6-diamino-3,5-dinitropyrazine-1-oxide（LLM-105）, triamino-trinitrobenzene（TATB）, 1,1-diamino-2,2-dinitroethene（DADNE or FOX-7）, and trinitrotoluene（TNT） are reviewed in this paper. The EOS determined from hydrostatic and non-hydrostatic compressions are discussed and compared. The theoretical results based on ab initio calculations are summarized and compared with the experimental data.展开更多
We study the near-field response of a shell nanocylinder pair, with its core filled by gain materials, using a two- dimensional finite-difference time-domain method. It is shown that the gain materials in the core of ...We study the near-field response of a shell nanocylinder pair, with its core filled by gain materials, using a two- dimensional finite-difference time-domain method. It is shown that the gain materials in the core of the cylinder can compensate for the intrinsic absorption of the metal shell, leading to local-field enhancement in the gap of the active pair. A linear dependence is found between the field enhancement and the gain coefficient at resonance. The detailed physics is studied by calculating the electrical-field distribution of the shell pair filled with different gain materials. The influence of the gap width and the shell thickness on the interaction of two adjacent active shell cylinders is also investigated.展开更多
Laser-induced breakdown spectroscopy （LIBS） has been developed to in situ diagnose the chemical compositions of the first wall in the EAST tokamak. However, the dynamics of optical emission of the key plasma-facing ...Laser-induced breakdown spectroscopy （LIBS） has been developed to in situ diagnose the chemical compositions of the first wall in the EAST tokamak. However, the dynamics of optical emission of the key plasma-facing materials, such as tungsten, molybdenum and graphite have not been investigated in a laser produced plasma （LPP） under vacuum. In this work, the temporal and spatial dynamics of optical emission were investigated using the spectrometer with ICCD. Plasma was produced by an Nd：YAG laser （1064 nm） with pulse duration of 6 ns. The results showed that the typical lifetime of LPP is less than 1.4 #s, and the lifetime of ions is shorter than atoms at ~10-6mbar. Temporal features of optical emission showed that the optimized delay times for collecting spectra are from 100 to 400 ns which depended on the corresponding species. For spatial distribution, the maximum LIBS spectral intensity in plasma plume is obtained in the region from 1.5 to 3.0 mm above the sample surface. Moreover, the plasma expansion velocity involving the different species in a multicomponent system was measured for obtaining the proper timing （gate delay time and gate width） of the maximum emission intensity and for understanding the plasma expansion mechanism. The order of expansion velocities for various species is Vc＋ 〉 VH 〉 Vsi＋ 〉 VLi 〉 VMo 〉 Vw. These results could be attributed to the plasma sheath acceleration and mass effect. In addition, an optimum signal-to-background ratio was investigated by varying both delay time and detecting position.展开更多
Radio frequency capacitively coupled plasmas(RF CCPs)operated in Ar/O_(2)gas mixtures which are widely adopted in microelectronics,display,and photovoltaic industry,are investigated based on an equivalent circuit mode...Radio frequency capacitively coupled plasmas(RF CCPs)operated in Ar/O_(2)gas mixtures which are widely adopted in microelectronics,display,and photovoltaic industry,are investigated based on an equivalent circuit model coupled with a global model.This study focuses on the effects of singlet metastable molecule O_(2)(b^(1)∑_(8)^(+)),highly excited Herzberg states O_(2)(A^(3)∑_(u)^(+),A^(3)△_(u),c^(1)∑_(u)^(-)),and the negative ion O_(2)^(-),which are usually neglected in simulation studies.Specifically,their impact on particle densities,electronegativity,electron temperature,voltage drop across the sheath,and absorbed power in the discharge is analyzed.The results indicate that O_(2)(b^(1)∑_(8)^(+))and O_(2)^(-)exhibit relatively high densities in argon-oxygen discharges.While O_(2)(A^(3)∑_(u)^(+),A^(3)△_(u),c^(1)∑_(u)^(-))play a critical role in O_(2)b1S+g production,especially at higher pressure.The inclusion of these particles reduces the electronegativity,electron temperature,and key species densities,especially the O^(-)and O^(*)densities.Moreover,the sheath voltage drop,as well as the inductance and resistance of the plasma bulk are enhanced,while the sheath dissipation power and total absorbed power decrease slightly.With the increasing pressure,the influence of these particles on the discharge properties becomes more significant.The study also explores the generation and loss of main neutral species and charged particles within the pressure range of 20 mTorr-100 mTorr(1 Torr=1.33322×10^(2)Pa),offering insights into essential and non-essential reactions for future low-pressure O_(2)and Ar/O_(2)CCP discharge modeling.展开更多
This study investigates the impact of Zn alloying on the dispersion of the reinforcing particle in Mg_(2)Sn/Mg composites.In the composite,Zn manifests in three distinct forms:Zn segregation layer between Mg–Mg_(2)Sn...This study investigates the impact of Zn alloying on the dispersion of the reinforcing particle in Mg_(2)Sn/Mg composites.In the composite,Zn manifests in three distinct forms:Zn segregation layer between Mg–Mg_(2)Sn,the solid solution and the MgZn_(2)phase.First-principles calculations confirm that the formation of Zn segregation layer decreases the interfacial energy of the Mg–Mg_(2)Sn.Importantly,this segregation layer significantly enhances the comigration capability of Mg_(2)Sn particles with Mg matrix during sintering flow,effectively hindering the agglomeration and coarsening of the nano-sized reinforcing phase.The dense and uniformly distributed nano-sized Mg_(2)Sn significantly increases the activity of non-basal slip,ensuring good elongation of the composite while enhancing strength.It can be concluded that enhancing the comigration-ability of reinforcing particles with the matrix is an effective strategy for achieving controlled dispersion of high-volume reinforcing particles and an excellent combination of strength and ductility in magnesium matrix composites.展开更多
Pt-rare-earth(PtRE)alloys are considered to be highly promising catalysts for oxygen reduction reaction(ORR)in acidic electrolytes.However,the wet-chemical synthesis of PtRE nanoalloys still faces significant challeng...Pt-rare-earth(PtRE)alloys are considered to be highly promising catalysts for oxygen reduction reaction(ORR)in acidic electrolytes.However,the wet-chemical synthesis of PtRE nanoalloys still faces significant challenges.The precise reaction mechanism for ORR of these catalysts is still unclear on significant aspects involving the rate-determining step and the nature of the ligand effect.Herein,we report a class of solvothermal synthesis of PtRE(RE is Dy or La)nanoalloys.Such PtRE nanoalloys here are active and stable in acidic media,with both high mass activities enhanced by 2-5 times relative to commercial Pt/C catalyst and high stabilities indicative of the little activity decay and negligible structure change after 10,000 cycles.Density functional theory calculations firmly confirm that the ligand effect of RE elements accelerates an O-O bond scission and steers the rate-determining steps from OH^(*)+H^(+)+e-→H_(2)O(on pure Pt surface)to HOOH^(*)+H^(+)+e-→OH^(*)+H_(2)O(on the PtRE nanoalloy surface)for the fast reaction kinetics,which could be fine-tuned by regulating the RE electronic structures and consequently endows the maximal rate of ORR catalysis with PtDy alloy catalysts.展开更多
Histidine(His),as the most chemically active and versatile member among the 20 natural amino acids,plays a key role in the coordination of copper(Ⅱ)(Cu(Ⅱ))in biological systems.Cu(II)-His species are ubiquitous in m...Histidine(His),as the most chemically active and versatile member among the 20 natural amino acids,plays a key role in the coordination of copper(Ⅱ)(Cu(Ⅱ))in biological systems.Cu(II)-His species are ubiquitous in metalloenzymes and proteins associated with various neurodegenerative diseases,where they regulate catalytic activity and mediate intracellular copper transport.While the steric influence of His is known to dictate donor group selection in Cu(Ⅱ)coordination,the extent of these constraints on peptide complexes remains unclear.In this study,we employed a multi-spectroscopic approach(FTIR,2D IR,UV-Vis,EPR,and NMR)to systematically investigate pH-dependent Cu(Ⅱ)coordination in three tripeptides.Our results demonstrate that Cu(Ⅱ)coordination geometries are cooperatively determined by both the protonation state of the N-terminus and the steric constraints imposed by the His residue.展开更多
Historically seen as a limitation,grain boundaries(GBs)within polycrystalline metal halide perovskite(MHP)films are thought to impede charge transport,adversely impacting the efficiency of perovskite solar cells(PSCs)...Historically seen as a limitation,grain boundaries(GBs)within polycrystalline metal halide perovskite(MHP)films are thought to impede charge transport,adversely impacting the efficiency of perovskite solar cells(PSCs).In this study,we employ home-built confo-cal photoluminescence microscopy,combined with photocurrent detec-tion modules,to directly visualize the carrier dynamics in the MHP film of PSCs under real operating conditions.Our findings suggest that GBs in high-efficiency PSCs function as carrier transport channels,where a notable enhancement in photocurrent is observed.Femtosecond transient absorption and Kelvin probe force microscopy measurements further validate the existence of a built-in electric field in the vicinity of GBs,offering additional driving force for charge separation and establishing channels for swift carrier transport along the GBs,thereby expediting subsequent charge collection processes.This study elucidates the pivotal role of GBs in operational PSCs and provides valuable insights for the fabrication of high-efficiency PSCs.展开更多
Transition metal borides(TMBs)are a new class of promising electrocatalysts for hydrogen generation by water splitting.However,the synthesis of robust all-in-one electrodes is challenging for practical applications.He...Transition metal borides(TMBs)are a new class of promising electrocatalysts for hydrogen generation by water splitting.However,the synthesis of robust all-in-one electrodes is challenging for practical applications.Herein,a facile solid-state boronization strategy is reported to synthesize a series of self-supported TMBs thin films(TMB-TFs)with large area and high catalytic activity.Among them,MoB thin film(MoB-TF)exhibits the highest activity toward electrocatalytic hydrogen evolution reaction(HER),displaying a low overpotential(η10=191 and 219 mV at 10 mA cm^(−2))and a small Tafel slope(60.25 and 61.91 mV dec^(−1))in 0.5M H_(2)SO_(4)and 1.0M KOH,respectively.Moreover,it outperforms the commercial Pt/C at the high current density region,demonstrating potential applications in industrially electrochemical water splitting.Theoretical study reveals that both surfaces terminated by TM and B atoms can serve as the active sites and the H*binding strength of TMBs is correlated with the p band center of B atoms.This work provides a new pathway for the potential application of TMBs in largescale hydrogen production.展开更多
We present a comprehensive investigation of the vibrational spectra and conformational distribution of neutral and cationic monoethanolamine(MEA)in the gas phase.Using infrared-vacuum ultraviolet non-resonant ionizati...We present a comprehensive investigation of the vibrational spectra and conformational distribution of neutral and cationic monoethanolamine(MEA)in the gas phase.Using infrared-vacuum ultraviolet non-resonant ionization fragmentation detected IR spectroscopy(NRIFD-IR),we obtained vibrational spectra in the 2500-3800 cm^(−1)range for both neutral and cationic MEA.Density functional theory(DFT)calculations at the B3LYPD3(BJ)/def2-TZVPP level were employed to elucidate the molecular structures and vibrational modes.Our analysis revealed twelve distinct conformers for neutral MEA,with N1gʹGgʹbeing the most stable,while cationic MEA exhibited four conformers,among which C1gʹGt conformer was found to be the primary contributor to the observed spectra.The experimental spectra were interpreted through comparison with anharmonic calculations,allowing for detailed assignment of vibrational modes.Notably,we observed significant differences in the OH stretch region between neutral and cationic species,reflecting changes in intramolecular hydrogen bonding upon ionization.Furthermore,our study highlights the necessity for distinct scaling factors when calculating harmonic frequencies for neutral and cationic substances.展开更多
The EHL-2 spherical torus is designed to demonstrate proton-boron(p-11B)fusion within a compact spherical tokamak.Its planned heating system includes a negative ion-based neutral beam injection(N-NBI),two positive ion...The EHL-2 spherical torus is designed to demonstrate proton-boron(p-11B)fusion within a compact spherical tokamak.Its planned heating system includes a negative ion-based neutral beam injection(N-NBI),two positive ion-based NBI systems(P-NBI),electron cyclotron resonance heating(ECRH),ion cyclotron resonance heating(ICRH),and high harmonic fast wave(HHFW),with a total power output of 31 MW.According to scaling law estimates,the device is capable of achieving H-mode operation.The plasma density,,n_(e,min)at the minimum L-H power threshold,P_(lh),is estimated to be 4.4×10^(19)m^(-3).The pedestal parameters were calculated using the REPED model.Assuming B as the primary impurity ion,the predicted pedestal width and height are lower compared to the typical case with carbon impurities.The pedestal collisionality for EHL-2 is estimated to range between 0.06 and 0.17,indicating the potential for significant energy loss due to edge localized modes(ELMs).The heat flux on the divertor plate has been calculated using the JOREK code.The peak heat fluxes during ELM bursts are approximately 31.0 MW/m^(2)at the lower inboard target and 39.5 MW/m^(2)at the lower outboard target.A preliminary design of the resonant magnetic perturbation(RMP)coils has been completed to both control type-I ELMs and correct error fields.The system comprises 16 coils arranged into 24 pairs.In ELM control mode,a 14/2 component is generated at 1.7 G/kAt,with a current of 4.9 kA required to achieveσChirikow=1 at the resonant surface,where the normalized poloidal magnetic flux is 0.85.In error field(EF)modulation mode,2/1 and 3/1 components are generated at 3.5 G/kAt and 2.8 G/kAt,respectively.展开更多
The next generation fusion device listed on ENN’s fusion roadmap,named as(ENN He-Long)EHL-2,is under both physics and engineering designs.The instabilities of ideal magnetohydrodynamics(MHD)mode and neoclassical tear...The next generation fusion device listed on ENN’s fusion roadmap,named as(ENN He-Long)EHL-2,is under both physics and engineering designs.The instabilities of ideal magnetohydrodynamics(MHD)mode and neoclassical tearing mode(NTM)stabilized by electron cyclotron current drive(ECCD)for EHL-2’s two typical operation scenarios are analyzed.For high-ion-temperature operating(HITO)scenario,the vertical displacement event(VDE)could be a big challenge to the device safety.For the steady-state operating(SSO)scenario,the limitation may rise from the ideal MHD mode,NTM,etc.This suggests that the MHD analysis of both operation scenarios should be done with different focusing.Preliminary analysis based on the current physics and engineering design of both two scenarios is given in this paper.Based on the analysis result of above,the future assessments might target at active control method and the effect of boron on MHD activities.展开更多
The γ-TiAl based Ti.Al.Mn.Nb alloys with different Nb additions were fabricated by selective laser melting (SLM) on the TC4 substrate. The effects of Nb content on microstructure and properties of the alloys were inv...The γ-TiAl based Ti.Al.Mn.Nb alloys with different Nb additions were fabricated by selective laser melting (SLM) on the TC4 substrate. The effects of Nb content on microstructure and properties of the alloys were investigated. The results reveal that the alloys consist of γ-TiAl phase with tetragonal lattice structure and α2-Ti3Al phase with hcp lattice structure, and show a sequential structure change from near full dendrite to near lamellar structure with the increase of Nb addition. Owing to the higher Nb content in γ-TiAl phase and the formation of near lamellar structure, the alloy with 7.0 at.% Nb addition has the best combination of properties among the studied alloys, namely, not only a high hardness of HV 2000, a high strength of 1390 MPa and a plastic deformation of about 24.5%, but also good tribological properties and high-temperature oxidation resistance.展开更多
The effects of the particle size of ground metallurgical grade silicon （MG-Si）, the sort of acids, and the type of stirring on the purified efficiency of MG-Si were investigated. It was found that a particle size le...The effects of the particle size of ground metallurgical grade silicon （MG-Si）, the sort of acids, and the type of stirring on the purified efficiency of MG-Si were investigated. It was found that a particle size less than 0.1 mm was most effective for acid leaching; the extraction yield of impurities was increased by 9% with HF leaching compared with HCl leaching and HNO3 leaching, and increased by 7% with ultrasonic stirring compared with mechanical stirring. The principle of hydrometallurgical purification of metallurgical grade silicon under ultrasonic fields was also discussed.展开更多
From the perspective of biomechanics and forming technology,Ti−Fe−Zr−Sn−Y eutectic alloy was designed using a“cluster-plus-glue-atom”model,and then the alloy was prepared by laser additive manufacturing(LAM)on pure ...From the perspective of biomechanics and forming technology,Ti−Fe−Zr−Sn−Y eutectic alloy was designed using a“cluster-plus-glue-atom”model,and then the alloy was prepared by laser additive manufacturing(LAM)on pure titanium substrate.The mechanical properties of the alloy were evaluated using micro-hardness and compression tester,and the elastic modulus was measured by nanoindenter.The results show that the alloy exhibits a high hardness of HV(788±10),a high strength of 2229 MPa,a failure strain of 14%,and a low elastic modulus of 87.5 GPa.The alloy also has good tribological,chemical,forming,and biological properties.The comprehensive performances of the Ti64.51Fe26.40Zr5.86Sn2.93Y0.30 alloy are superior to those of the Ti70.5Fe29.5 eutectic alloy and commercial Ti−6Al−4V alloy.All the above-mentioned qualities make the alloy a promising candidate as LAM biomaterial.展开更多
The purpose of this paper is to study large-sized copper billets refined with 5N ultrahigh purity after vacuum melting and directional solidifi-cation （VMDS）. The precise impurity analysis of copper billets was carr...The purpose of this paper is to study large-sized copper billets refined with 5N ultrahigh purity after vacuum melting and directional solidifi-cation （VMDS）. The precise impurity analysis of copper billets was carried out with a glow discharge mass spectrometer （GDMS）. The re-sults demonstrate that the total concentration of twenty-two impurities is decreased by 63.1wt.%-66.5 wt.%. Ag, P, S, Na, Mg, Se, Zn, In and Bi are easy to be removed due to lgPimp - lgPCu 1.5, and they can be removed effectively under the vacuum condition of 1650-1700 K for 30 min. The electrical conductivity of 5N copper is higher than that of the raw material as the impurity concentrations decrease. The segrega-tion effect in directional solidification can be remarkable when the equilibrium distribution coefficient （k0） value is less than 0.65 due to the strong affinity of Cu for some metallic and non-metallic impurities.展开更多
基金supported by the National Magnetic Confinement Fusion Science Program of China(No.2013GB109005)National Natural Science Foundation of China(Nos.11175035,11475039)+1 种基金Chinesisch-Deutsches Forschungs Project(GZ768)the Fundamental Research Funds for the Central Universities of China(Nos.DUT12ZD(G)01,DUT14ZD(G)04)
文摘Recently, a laser-induced breakdown spectroscopic （LIBS） system has been developed for in situ measurements of the chemical compositions of plasma facing materials （PFMs） in the Experimental Advanced Superconducting Tokamak （EAST）. In this study, a LIBS system, which was used in a similar optical configuration to the in situ LIBS system in EAST, has been developed to investigate the spatial distribution of PFM elements at 10-4 Pa. The aim of this study was to understand the nature of the spatial distribution of atoms or ions of different elements in the plasma plume and optimize the signal to background ratio for the in situ LIBS diagnosis in EAST. The spatial profiles of the LIBS signals of C, Si, Mo and the continuous background were measured. Moreover, the influence of laser spot size and laser energy density on the LIBS signals of C, Si, Mo and H was also investigated. The results show that the distribution of the C, Si and Mo peaks＇ intensities first increased and then decreased from the center to the edge of the plasma plume. There was a maximum value at R ≈ 1.5 mm from the center of the plasma plume. This work aims to improve the understanding of ablating plasma dynamics in very low pressure environments and give guidance to optimize the LIBS system in the EAST device.
基金supported by the National Natural Science Foundation of China(Grant No.11134005)
文摘Silicene, a monolayer of silicon atoms arranged in a honeycomb lattice, has been undergoing rapid development in recent years due to its superior electronic properties and its compatibility with mature silicon-based semiconductor technology. The successful synthesis of silicene on several substrates provides a solid foundation for the use of silicene in future microelectronic devices. In this review, we discuss the growth mechanism of silicene on an Ag(111) surface, which is crucial for achieving high quality silicene. Several critical issues related to the electronic properties of silicene are also summarized, including the point defect effect, substrate effect, intercalation of alkali metal, and alloying with transition metals.
基金the National Natural Science Foundation of China(No.50474055)
文摘Functionally graded materials （FGM） have been widely used in many industries such as aerospace, energy and electronics. In this experimental study of fabricating FGM, an approach was developed to prepare AI/Si FGM using power ultrasonic separation method. Material sample with continuously changing composition and performance/properties was successfully produced. Results showed that the microstructure of the FGM sample transited, from its top to bottom, from the hypereutectic structure with a large quantity of primary Si gradually to the eutectic, and finally to the hypoeutectic with numerous primary AI dendrites. The distribution of primary Si and microhardness of the FGM sample also presented graded characteristics, resulting that the wear resistance of the FGM sample decreased from top to bottom. Preliminary discussion was made on the mechanism of the formation of AI/Si FGM.
基金supported by the National Magnetic Confinement Fusion Science Program of China(No.2013GB109005)National Natural Science Foundation of China(Nos.11175035,10875023)+1 种基金Chinesisch-Deutsches Forschungs Project(GZ768)the Fundamental Research Funds for the Central Universities(DUT12ZD(G)01)
文摘Laser-induced breakdown spectroscopy （LIBS） is a powerful analytical tool for real- time diagnostics and detection of multiple elements deposited at the first wall of magnetically confined plasma ft^sion devices. Recently, we have tested LIBS in our laboratory for application to in situ real-time diagnostics in the fusion device EAST. In this study, we applied polarization- resolved LIBS （PR-LIBS） to reduce the background continuum and enhance the resolution and sensitivity of LIBS. We used aluminium （A1） （as a substitute for Be） and the first wall materials tungsten （W） and molybdenum （Mo） to investigate polarized continuum emission and signal-to- background ratio （SBR）. A Nd：YAG laser with first, second and third harmonics was used to produce plasma. The effects of the laser polarization plane, environmental pressure and polarizer detection angle were investigated. The spectra obtained without using a polarizer （i.e. LIBS） were compared with those obtained with a polarizer （PR-LIBS）. Distribution of emission spectral intensity was observed to follow Malus＇ law with respect to variation in the angle of detection of the polarizer. The spectra obtained by PR-LIBS had a higher SBR and greater stability than those obtained by LIBS, thereby enhancing the reliability of LIBS for quantitative analyses. A comparison of A1, Mo and W showed that W exhibited a higher continuum with stronger polarization than the low-Z elements.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11174045 and 11404050)
文摘The unreacted equation of state（EOS） of energetic materials is an important thermodynamic relationship to characterize their high pressure behaviors and has practical importance. The previous experimental and theoretical works on the equation of state of several energetic materials including nitromethane, 1,3,5-trinitrohexahydro-1,3,5-triazine（RDX）,1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane（HMX）, hexanitrostilbene（HNS）, hexanitrohexaazaisowurtzitane（HNIW or CL-20）, pentaerythritol tetranitrate（PETN）, 2,6-diamino-3,5-dinitropyrazine-1-oxide（LLM-105）, triamino-trinitrobenzene（TATB）, 1,1-diamino-2,2-dinitroethene（DADNE or FOX-7）, and trinitrotoluene（TNT） are reviewed in this paper. The EOS determined from hydrostatic and non-hydrostatic compressions are discussed and compared. The theoretical results based on ab initio calculations are summarized and compared with the experimental data.
基金Project support by the National Natural Science Foundation of China (Grant Nos. 10975012 and 11074029)
文摘We study the near-field response of a shell nanocylinder pair, with its core filled by gain materials, using a two- dimensional finite-difference time-domain method. It is shown that the gain materials in the core of the cylinder can compensate for the intrinsic absorption of the metal shell, leading to local-field enhancement in the gap of the active pair. A linear dependence is found between the field enhancement and the gain coefficient at resonance. The detailed physics is studied by calculating the electrical-field distribution of the shell pair filled with different gain materials. The influence of the gap width and the shell thickness on the interaction of two adjacent active shell cylinders is also investigated.
基金supported by the National Magnetic Confinement Fusion Science Program of China (No. 2013GB109005)National Natural Science Foundation of China (Nos. 11475039, 11605023, 11705020 and 11605238)+2 种基金Chinesisch-Deutsches Forschungsprojekt (No. GZ768)China Postdoctoral Science Foundation (Nos. 2016M591423, 2017T100172)the Fundamental Research Funds for the Central Universities (Nos. DUT15RC(3)072, DUT16TD13, DUT17RC(3)030, DUT17RC (4)53)
文摘Laser-induced breakdown spectroscopy （LIBS） has been developed to in situ diagnose the chemical compositions of the first wall in the EAST tokamak. However, the dynamics of optical emission of the key plasma-facing materials, such as tungsten, molybdenum and graphite have not been investigated in a laser produced plasma （LPP） under vacuum. In this work, the temporal and spatial dynamics of optical emission were investigated using the spectrometer with ICCD. Plasma was produced by an Nd：YAG laser （1064 nm） with pulse duration of 6 ns. The results showed that the typical lifetime of LPP is less than 1.4 #s, and the lifetime of ions is shorter than atoms at ~10-6mbar. Temporal features of optical emission showed that the optimized delay times for collecting spectra are from 100 to 400 ns which depended on the corresponding species. For spatial distribution, the maximum LIBS spectral intensity in plasma plume is obtained in the region from 1.5 to 3.0 mm above the sample surface. Moreover, the plasma expansion velocity involving the different species in a multicomponent system was measured for obtaining the proper timing （gate delay time and gate width） of the maximum emission intensity and for understanding the plasma expansion mechanism. The order of expansion velocities for various species is Vc＋ 〉 VH 〉 Vsi＋ 〉 VLi 〉 VMo 〉 Vw. These results could be attributed to the plasma sheath acceleration and mass effect. In addition, an optimum signal-to-background ratio was investigated by varying both delay time and detecting position.
基金supported by the National Natural Science Foundation of China(Grant Nos.12020101005,12475202,12347131,and 12405289).
文摘Radio frequency capacitively coupled plasmas(RF CCPs)operated in Ar/O_(2)gas mixtures which are widely adopted in microelectronics,display,and photovoltaic industry,are investigated based on an equivalent circuit model coupled with a global model.This study focuses on the effects of singlet metastable molecule O_(2)(b^(1)∑_(8)^(+)),highly excited Herzberg states O_(2)(A^(3)∑_(u)^(+),A^(3)△_(u),c^(1)∑_(u)^(-)),and the negative ion O_(2)^(-),which are usually neglected in simulation studies.Specifically,their impact on particle densities,electronegativity,electron temperature,voltage drop across the sheath,and absorbed power in the discharge is analyzed.The results indicate that O_(2)(b^(1)∑_(8)^(+))and O_(2)^(-)exhibit relatively high densities in argon-oxygen discharges.While O_(2)(A^(3)∑_(u)^(+),A^(3)△_(u),c^(1)∑_(u)^(-))play a critical role in O_(2)b1S+g production,especially at higher pressure.The inclusion of these particles reduces the electronegativity,electron temperature,and key species densities,especially the O^(-)and O^(*)densities.Moreover,the sheath voltage drop,as well as the inductance and resistance of the plasma bulk are enhanced,while the sheath dissipation power and total absorbed power decrease slightly.With the increasing pressure,the influence of these particles on the discharge properties becomes more significant.The study also explores the generation and loss of main neutral species and charged particles within the pressure range of 20 mTorr-100 mTorr(1 Torr=1.33322×10^(2)Pa),offering insights into essential and non-essential reactions for future low-pressure O_(2)and Ar/O_(2)CCP discharge modeling.
基金support provided by the National Natural Science Foundation of China(No.52174357)Fundamental Research Funds for the Central Universities(No.DUT21LAB132)The Basic and Applied Basic Research Major Programme of Guangdong Province,China(No.2021B0301030003)。
文摘This study investigates the impact of Zn alloying on the dispersion of the reinforcing particle in Mg_(2)Sn/Mg composites.In the composite,Zn manifests in three distinct forms:Zn segregation layer between Mg–Mg_(2)Sn,the solid solution and the MgZn_(2)phase.First-principles calculations confirm that the formation of Zn segregation layer decreases the interfacial energy of the Mg–Mg_(2)Sn.Importantly,this segregation layer significantly enhances the comigration capability of Mg_(2)Sn particles with Mg matrix during sintering flow,effectively hindering the agglomeration and coarsening of the nano-sized reinforcing phase.The dense and uniformly distributed nano-sized Mg_(2)Sn significantly increases the activity of non-basal slip,ensuring good elongation of the composite while enhancing strength.It can be concluded that enhancing the comigration-ability of reinforcing particles with the matrix is an effective strategy for achieving controlled dispersion of high-volume reinforcing particles and an excellent combination of strength and ductility in magnesium matrix composites.
基金supported by the National Natural Science Foundation of China(No.21975151)China Postdoctoral Science Foundation(No.2023M733452).
文摘Pt-rare-earth(PtRE)alloys are considered to be highly promising catalysts for oxygen reduction reaction(ORR)in acidic electrolytes.However,the wet-chemical synthesis of PtRE nanoalloys still faces significant challenges.The precise reaction mechanism for ORR of these catalysts is still unclear on significant aspects involving the rate-determining step and the nature of the ligand effect.Herein,we report a class of solvothermal synthesis of PtRE(RE is Dy or La)nanoalloys.Such PtRE nanoalloys here are active and stable in acidic media,with both high mass activities enhanced by 2-5 times relative to commercial Pt/C catalyst and high stabilities indicative of the little activity decay and negligible structure change after 10,000 cycles.Density functional theory calculations firmly confirm that the ligand effect of RE elements accelerates an O-O bond scission and steers the rate-determining steps from OH^(*)+H^(+)+e-→H_(2)O(on pure Pt surface)to HOOH^(*)+H^(+)+e-→OH^(*)+H_(2)O(on the PtRE nanoalloy surface)for the fast reaction kinetics,which could be fine-tuned by regulating the RE electronic structures and consequently endows the maximal rate of ORR catalysis with PtDy alloy catalysts.
基金supported by the National Natural Science Foundation of China(No.22403012 to Chunyang Wang,Wenzhe Zhou,and Xin-Xing Zhang,Nos.22241304 and 22225303 to Kaijun Yuan)the Strategic Priority Research Program of the Chinese Academy of Sciences(Nos.XDB0970000 and XDB0970200).
文摘Histidine(His),as the most chemically active and versatile member among the 20 natural amino acids,plays a key role in the coordination of copper(Ⅱ)(Cu(Ⅱ))in biological systems.Cu(II)-His species are ubiquitous in metalloenzymes and proteins associated with various neurodegenerative diseases,where they regulate catalytic activity and mediate intracellular copper transport.While the steric influence of His is known to dictate donor group selection in Cu(Ⅱ)coordination,the extent of these constraints on peptide complexes remains unclear.In this study,we employed a multi-spectroscopic approach(FTIR,2D IR,UV-Vis,EPR,and NMR)to systematically investigate pH-dependent Cu(Ⅱ)coordination in three tripeptides.Our results demonstrate that Cu(Ⅱ)coordination geometries are cooperatively determined by both the protonation state of the N-terminus and the steric constraints imposed by the His residue.
基金supported by the CAS Projects for Young Scientists in Basic Research(YSBR-007)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0970302)+4 种基金the National Natural Science Foundation of China(22233005,52272193)the DICP funding(I202315),the Natural Science Foundation of Liaoning(2024JH3/50100010)the LiaoNing Revitalization Talents Program(XLYC2203043)the Dalian Science and Technology Innovation Fund(2024RJ006)the Fundamental Research Funds for the Central Universities(DUT-22LAB602).
文摘Historically seen as a limitation,grain boundaries(GBs)within polycrystalline metal halide perovskite(MHP)films are thought to impede charge transport,adversely impacting the efficiency of perovskite solar cells(PSCs).In this study,we employ home-built confo-cal photoluminescence microscopy,combined with photocurrent detec-tion modules,to directly visualize the carrier dynamics in the MHP film of PSCs under real operating conditions.Our findings suggest that GBs in high-efficiency PSCs function as carrier transport channels,where a notable enhancement in photocurrent is observed.Femtosecond transient absorption and Kelvin probe force microscopy measurements further validate the existence of a built-in electric field in the vicinity of GBs,offering additional driving force for charge separation and establishing channels for swift carrier transport along the GBs,thereby expediting subsequent charge collection processes.This study elucidates the pivotal role of GBs in operational PSCs and provides valuable insights for the fabrication of high-efficiency PSCs.
基金National Natural Science Foundation of China,Grant/Award Number:52172058Outstanding Youth Fund of Natural Science Foundation of Inner Mongolia Autonomous Region,Grant/Award Number:2023JQ15+4 种基金Fundamental Research Funds for the Inner Mongolia Normal University,Grant/Award Numbers:2022JBBJ010,2022JBTD008Major Project Cultivation Fund for the Inner Mongolia Normal University,Grant/Award Number:2020ZD01Funds for Reform and Development of Local Universities Supported by The Central Government(Cultivation of First-Class Disciplines in Physics)Postdoctoral Fellowship Program of CPSF,Grant/Award Number:GZB20240101China Postdoctoral Science Foundation,Grant/Award Number:2024M750304.
文摘Transition metal borides(TMBs)are a new class of promising electrocatalysts for hydrogen generation by water splitting.However,the synthesis of robust all-in-one electrodes is challenging for practical applications.Herein,a facile solid-state boronization strategy is reported to synthesize a series of self-supported TMBs thin films(TMB-TFs)with large area and high catalytic activity.Among them,MoB thin film(MoB-TF)exhibits the highest activity toward electrocatalytic hydrogen evolution reaction(HER),displaying a low overpotential(η10=191 and 219 mV at 10 mA cm^(−2))and a small Tafel slope(60.25 and 61.91 mV dec^(−1))in 0.5M H_(2)SO_(4)and 1.0M KOH,respectively.Moreover,it outperforms the commercial Pt/C at the high current density region,demonstrating potential applications in industrially electrochemical water splitting.Theoretical study reveals that both surfaces terminated by TM and B atoms can serve as the active sites and the H*binding strength of TMBs is correlated with the p band center of B atoms.This work provides a new pathway for the potential application of TMBs in largescale hydrogen production.
基金the Dalian Coherent Light Source (DCLS) for support and assistancesurported by the National Natural Science Foundation of China (No.22288201)+1 种基金the Chinese Academy of Sciences (GJJSTD20220001)the Innovation Program for Quantum Science and Technology (No.2021ZD0303305)。
文摘We present a comprehensive investigation of the vibrational spectra and conformational distribution of neutral and cationic monoethanolamine(MEA)in the gas phase.Using infrared-vacuum ultraviolet non-resonant ionization fragmentation detected IR spectroscopy(NRIFD-IR),we obtained vibrational spectra in the 2500-3800 cm^(−1)range for both neutral and cationic MEA.Density functional theory(DFT)calculations at the B3LYPD3(BJ)/def2-TZVPP level were employed to elucidate the molecular structures and vibrational modes.Our analysis revealed twelve distinct conformers for neutral MEA,with N1gʹGgʹbeing the most stable,while cationic MEA exhibited four conformers,among which C1gʹGt conformer was found to be the primary contributor to the observed spectra.The experimental spectra were interpreted through comparison with anharmonic calculations,allowing for detailed assignment of vibrational modes.Notably,we observed significant differences in the OH stretch region between neutral and cationic species,reflecting changes in intramolecular hydrogen bonding upon ionization.Furthermore,our study highlights the necessity for distinct scaling factors when calculating harmonic frequencies for neutral and cationic substances.
基金the auspices of National Natural Science Foundations of China(Nos.12075284 and 12205157)supported by the High-End Talents Program of Hebei Province,Innovative Approaches towards Development of Carbon-Free Clean Fusion Energy(No.2021HBQZYCSB006).
文摘The EHL-2 spherical torus is designed to demonstrate proton-boron(p-11B)fusion within a compact spherical tokamak.Its planned heating system includes a negative ion-based neutral beam injection(N-NBI),two positive ion-based NBI systems(P-NBI),electron cyclotron resonance heating(ECRH),ion cyclotron resonance heating(ICRH),and high harmonic fast wave(HHFW),with a total power output of 31 MW.According to scaling law estimates,the device is capable of achieving H-mode operation.The plasma density,,n_(e,min)at the minimum L-H power threshold,P_(lh),is estimated to be 4.4×10^(19)m^(-3).The pedestal parameters were calculated using the REPED model.Assuming B as the primary impurity ion,the predicted pedestal width and height are lower compared to the typical case with carbon impurities.The pedestal collisionality for EHL-2 is estimated to range between 0.06 and 0.17,indicating the potential for significant energy loss due to edge localized modes(ELMs).The heat flux on the divertor plate has been calculated using the JOREK code.The peak heat fluxes during ELM bursts are approximately 31.0 MW/m^(2)at the lower inboard target and 39.5 MW/m^(2)at the lower outboard target.A preliminary design of the resonant magnetic perturbation(RMP)coils has been completed to both control type-I ELMs and correct error fields.The system comprises 16 coils arranged into 24 pairs.In ELM control mode,a 14/2 component is generated at 1.7 G/kAt,with a current of 4.9 kA required to achieveσChirikow=1 at the resonant surface,where the normalized poloidal magnetic flux is 0.85.In error field(EF)modulation mode,2/1 and 3/1 components are generated at 3.5 G/kAt and 2.8 G/kAt,respectively.
文摘The next generation fusion device listed on ENN’s fusion roadmap,named as(ENN He-Long)EHL-2,is under both physics and engineering designs.The instabilities of ideal magnetohydrodynamics(MHD)mode and neoclassical tearing mode(NTM)stabilized by electron cyclotron current drive(ECCD)for EHL-2’s two typical operation scenarios are analyzed.For high-ion-temperature operating(HITO)scenario,the vertical displacement event(VDE)could be a big challenge to the device safety.For the steady-state operating(SSO)scenario,the limitation may rise from the ideal MHD mode,NTM,etc.This suggests that the MHD analysis of both operation scenarios should be done with different focusing.Preliminary analysis based on the current physics and engineering design of both two scenarios is given in this paper.Based on the analysis result of above,the future assessments might target at active control method and the effect of boron on MHD activities.
基金Project(51371041) supported by Chinese Scholarship Council and the National Natural Science Foundation of China
文摘The γ-TiAl based Ti.Al.Mn.Nb alloys with different Nb additions were fabricated by selective laser melting (SLM) on the TC4 substrate. The effects of Nb content on microstructure and properties of the alloys were investigated. The results reveal that the alloys consist of γ-TiAl phase with tetragonal lattice structure and α2-Ti3Al phase with hcp lattice structure, and show a sequential structure change from near full dendrite to near lamellar structure with the increase of Nb addition. Owing to the higher Nb content in γ-TiAl phase and the formation of near lamellar structure, the alloy with 7.0 at.% Nb addition has the best combination of properties among the studied alloys, namely, not only a high hardness of HV 2000, a high strength of 1390 MPa and a plastic deformation of about 24.5%, but also good tribological properties and high-temperature oxidation resistance.
基金supported by the National Natural Science Foundation of China (No. 50674018)
文摘The effects of the particle size of ground metallurgical grade silicon （MG-Si）, the sort of acids, and the type of stirring on the purified efficiency of MG-Si were investigated. It was found that a particle size less than 0.1 mm was most effective for acid leaching; the extraction yield of impurities was increased by 9% with HF leaching compared with HCl leaching and HNO3 leaching, and increased by 7% with ultrasonic stirring compared with mechanical stirring. The principle of hydrometallurgical purification of metallurgical grade silicon under ultrasonic fields was also discussed.
基金Project(51371041)supported by the National Natural Science Foundation of China。
文摘From the perspective of biomechanics and forming technology,Ti−Fe−Zr−Sn−Y eutectic alloy was designed using a“cluster-plus-glue-atom”model,and then the alloy was prepared by laser additive manufacturing(LAM)on pure titanium substrate.The mechanical properties of the alloy were evaluated using micro-hardness and compression tester,and the elastic modulus was measured by nanoindenter.The results show that the alloy exhibits a high hardness of HV(788±10),a high strength of 2229 MPa,a failure strain of 14%,and a low elastic modulus of 87.5 GPa.The alloy also has good tribological,chemical,forming,and biological properties.The comprehensive performances of the Ti64.51Fe26.40Zr5.86Sn2.93Y0.30 alloy are superior to those of the Ti70.5Fe29.5 eutectic alloy and commercial Ti−6Al−4V alloy.All the above-mentioned qualities make the alloy a promising candidate as LAM biomaterial.
文摘The purpose of this paper is to study large-sized copper billets refined with 5N ultrahigh purity after vacuum melting and directional solidifi-cation （VMDS）. The precise impurity analysis of copper billets was carried out with a glow discharge mass spectrometer （GDMS）. The re-sults demonstrate that the total concentration of twenty-two impurities is decreased by 63.1wt.%-66.5 wt.%. Ag, P, S, Na, Mg, Se, Zn, In and Bi are easy to be removed due to lgPimp - lgPCu 1.5, and they can be removed effectively under the vacuum condition of 1650-1700 K for 30 min. The electrical conductivity of 5N copper is higher than that of the raw material as the impurity concentrations decrease. The segrega-tion effect in directional solidification can be remarkable when the equilibrium distribution coefficient （k0） value is less than 0.65 due to the strong affinity of Cu for some metallic and non-metallic impurities.
