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 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
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 complex nature of laser-material interaction causes non-stoichiometric ablation of alloy samples.This is attributed to matrix effect, which reduces analyzing capability. To address this issue, the analytical perfo...The complex nature of laser-material interaction causes non-stoichiometric ablation of alloy samples.This is attributed to matrix effect, which reduces analyzing capability. To address this issue, the analytical performance of three different normalization methods, namely normalization with background, internal normalization and three point smoothing techniques at different parameter settings is studied for quantification of Ag and Zn by Laser induced breakdown spectroscopy(LIBS).The LIBS spectra of five known concentration of silver zinc binary composites have been investigated at various laser irradiances(LIs). Calibration curves for both Ag(I) line(4d^(10)5s^2S_(1/2)→4d^(10)5p^2P_(1/2) at 338.28 nm) and Zn(I) line(4s5s^3S_1→4s4p^3P_2 at 481.053 nm) have been determined at LI of 5.86?×?10^(10)W cm^(-2). Slopes of these calibration curves provide the valuation of matrix effect in the Ag–Zn composites. With careful sample preparation and normalization after smoothing at optimum parameter setting(OPS), the minimization of sample matrix effect has been successfully achieved. A good linearity has been obtained in Ag and Zn calibration curve at OPS when normalized the whole area of spectrum after smoothing and the obtained coefficients of determination values were R^2?=?0.995 and 0.998 closer to 1. The results of matrix effect have been further verified by analysis of plasma parameters. Both plasma parameters showed no change with varying concentration at OPS. However, at high concentration of Ag, the observed significant changes in both plasma parameters at common parameter setting PS-1 and PS-2 were the gesture of matrix effect. In our case, the better analytical results were obtained at smoothing function with optimized parameter setting that indicates it is more efficient than normalization with background and internal normalization method.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
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
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
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
The compression creep deformation of the high volume fraction of SiC particles reinforced AI-Mg-Si composite fabricated by pressure-less infiltration was investigated. The experimental results show that the creep stre...The compression creep deformation of the high volume fraction of SiC particles reinforced AI-Mg-Si composite fabricated by pressure-less infiltration was investigated. The experimental results show that the creep stress exponents are very high at temperatures of 673 K, 723 K and 773 K, and if taking the threshold stress into account, the true stress exponent of minimum creep strain rate is still approximately 5, although the volume fraction of reinforcements is very high. The creep strain rate in the high volume fraction reinforced aluminum alloy matrix composites is controlled by matrix lattice diffusion. It is found that the creep-strengthening effect of high volume fraction of silicon carbide particles is significant, although the particles do not form effective obstacles to dislocation motion.展开更多
The study of sulfur hexafluoride(SF6) discharge is vital for its application in gas-insulated equipment. Direct current partial discharge(PD) may cause SF6 decomposition, and the decomposed products of SF6, such as F ...The study of sulfur hexafluoride(SF6) discharge is vital for its application in gas-insulated equipment. Direct current partial discharge(PD) may cause SF6 decomposition, and the decomposed products of SF6, such as F atoms, play a dominant role in the breakdown of insulation systems. In this study, the PD caused by metal protrusion defects is simulated by a needle-plate electrode using pulsed high voltage in SF6/Ar mixtures. The spatial and temporal characteristics of SF6/Ar plasma are analyzed by measuring the emission spectra of F and Ar atoms, which are important for understanding the characteristics of PD. The spatial resolved results show that both F and Ar atom spectral intensities increase first from the plate anode to the needle and then decrease under the conditions of a background pressure of400 Pa, peak voltage of-1000 V, frequency of 2 kHz, pulse width of 60 μs, and electrode gap of 5-9 mm. However, the distribution characteristics of F and Ar are significantly different. The temporal distribution results show that the spectral intensity of Ar decreasesfirst and then increases slowly, while the spectral intensity of F increases slowly for the duration of the pulsed discharge at the electrode gap of 5 mm and the pulse width of40-80 μs.展开更多
The formation of nanoporous Pd was studied by electro-chemical dealloying a rapidly-quenched Al70Pd17Fe13 quasicrystal alloy in dilute NaCl aqueous solution,and the electro-catalytic activity of the nanoporous Pd towa...The formation of nanoporous Pd was studied by electro-chemical dealloying a rapidly-quenched Al70Pd17Fe13 quasicrystal alloy in dilute NaCl aqueous solution,and the electro-catalytic activity of the nanoporous Pd towards methanol electro-oxidation was evaluated by cyclic voltammetry in 1 mol/L KOH solution.XRD and TEM analyses revealed that nano-decomposition of quasicrystal grains occurred in the initial stage of dealloying,and the fully dealloyed sample was composed of FCC-Pd phase.Scanning electron microscopy observation indicated that a maze-like nanoporous pattern was formed in the dealloyed sample,consisting of percolated pores of 5.20 nm in diameter in a skeleton of randomly-orientated Pd nano-ligaments with a uniform thickness of^5 nm.A retention of^12 at.%Al in the Pd nano-ligments was determined by energy dispersive X-ray spectroscopy(EDS).The nanoporous Pd demonstrated obvious electro-catalytic activity towards methanol electro-oxidation in alkaline environment.展开更多
To improve the wear and corrosion properties of AZ91D magnesium alloys,Cu-based amorphous composite coatings were fabricated on AZ91D magnesium alloy by laser cladding using mixed powders of Cu47Ti34Zr11Ni8 and SiC.Th...To improve the wear and corrosion properties of AZ91D magnesium alloys,Cu-based amorphous composite coatings were fabricated on AZ91D magnesium alloy by laser cladding using mixed powders of Cu47Ti34Zr11Ni8 and SiC.The wear and corrosion behaviours of the coatings were investigated.The wear resistance of the coatings was evaluated under dry sliding wear condition at room temperature.The corrosion resistance of the coatings was tested in 3.5%(mass fraction) NaCl solution.The coatings exhibit excellent wear resistance due to the recombined action of amorphous phase and different intermetallic compounds.The main wear mechanisms of the coatings and the AZ91D sample are different.The former is abrasive wear and the latter is adhesive wear.The coatings compared with AZ91D magnesium alloy also exhibit good corrosion resistance because of the presence of the amorphous phase in the coatings.展开更多
An experimental setup has been designed and realized in order to optimize the characteristics of laser-induced breakdown spectroscopy system working in various pressure environments. An approach combined the normaliza...An experimental setup has been designed and realized in order to optimize the characteristics of laser-induced breakdown spectroscopy system working in various pressure environments. An approach combined the normalization methods with the partial least squares(PLS) method are developed for quantitative analysis of molybdenum(Mo) element in the multi-component alloy,which is the first wall material in the Experimental Advanced Superconducting Tokamak. In this study, the different spectral normalization methods(total spectral area normalization,background normalization, and reference line normalization) are investigated for reducing the uncertainty and improving the accuracy of spectral measurement. The results indicates that the approach of PLS based on inter-element interference is significantly better than the conventional PLS methods as well as the univariate linear methods in the various pressure for molybdenum element analysis.展开更多
Pseudobinary Ti 1 x Al x N films were synthesized on Si (100) wafer by DC magnetron sputtering method using Ti 1 x Al x alloy targets with different Al contents. The composition of the Ti 1 x Al x N films was determin...Pseudobinary Ti 1 x Al x N films were synthesized on Si (100) wafer by DC magnetron sputtering method using Ti 1 x Al x alloy targets with different Al contents. The composition of the Ti 1 x Al x N films was determined by electron probe microanalysis (EPMA). Structural characteristic was performed by X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM). First principles virtual crystal calculations for the Ti 1 x Al x N disordered alloys were used for the XRD simulations. The crystalline structure of the Ti 0.61 Al 0.39 N film was found to be a metastable single phase with NaCl (B1) structure. Its lattice constant, determined by XRD, was less than that of pure TiN. With the increase of Al content, the lattice constant of B1 phase was continually decreased, while würtzite (B4) structure was observed in the Ti 0.40 Al 0.60 N film. When x reached 0.75, the B1 phase disappeared, and only B4 phase was remained. The critical Al content for the phase transition from NaCl to würtzite structure in this paper was about 0.60, which could be explained by both the thermodynamic model and the electron theory. As-deposited Ti 1 x Al x N films exhibited excellent mechanical properties. Hardness measurements of Ti 1 x Al x N films showed a high value of 45GPa for x=0.39 and was decreased to value of 27 GPa with increasing Al at x=0.60.展开更多
Hydrogenated microcrystalline silicon thin films (μc-Si:H) were deposited by plasma assistant magnetron sputtering in Ar-H 2 gas mixture. The effects of growth temperature from 150 to 450 C on properties of deposited...Hydrogenated microcrystalline silicon thin films (μc-Si:H) were deposited by plasma assistant magnetron sputtering in Ar-H 2 gas mixture. The effects of growth temperature from 150 to 450 C on properties of deposited Si films were investigated at two different hydrogen diluted gases with [H 2 ]/([Ar]+[H 2 ]) of 10% and 50% at 3 Pa. The crystallinity of Si films examined by Raman scattering exhibited higher degrada- tion by lowering growth temperature from 250 to 150 C in low hydrogen diluted gas of 10% than that in high hydrogen diluted gas of 50%. The IR absorption band around 845 and 890 cm 1 as well as calculated concentration of bonded hydrogen showed more obvious decrease of samples deposited in low hydrogen diluted gas of 10% than that in high hydrogen diluted gas of 50%. The optical band gasps of both groups of samples measured by ultraviolet-visible optical absorption were decreased with increasing temperature in both gas conditions.展开更多
A nanoporous FePt alloy has been fabricated by dealloying a melt-spun Fe(60)Pt(20)B(20)alloy composed of nanoscale amorphous and face-centered-cubic FePt(fcc-FePt)phases in H2 SO4 aqueous solution.The nanoporous alloy...A nanoporous FePt alloy has been fabricated by dealloying a melt-spun Fe(60)Pt(20)B(20)alloy composed of nanoscale amorphous and face-centered-cubic FePt(fcc-FePt)phases in H2 SO4 aqueous solution.The nanoporous alloy consists of single fcc-FePt phase with an Fe/Pt atomic ratio of about 55.3/44.7,and possesses a uniform interpenetrating ligament-channel structure with average ligament and pore sizes of 27 nm and 12 nm,respectively.The nanoporous fcc-FePt alloy shows soft magnetic characteristics with a saturation magnetization of 37.9 emu/g and better electrocatalytic activity for methanol oxidation than commercial Pt/C in acidic environment.The phase transformation from disordered fcc-Fe Pt into ordered face-centered-tetragonal FePt(L10-FePt)in the nanoporous alloy has been realized after annealing at823-943 K for 600 s.The volume fraction of the L10-FePt phase in the alloy increases with the rise of annealing temperature,which results in the enhancements of coercivity and saturation magnetization from 0.14 kOe and 38.5 emu/g to 8.42 kOe and 51.4 emu/g,respectively.The ligament size of the samples is increased after annealing.展开更多
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
The glow discharge in pure helium at atmospheric pressure, controlled by a dielectric barrier between coaxial electrodes, is investigated based on a one-dimensional self-consistent fluid model. By solving the continui...The glow discharge in pure helium at atmospheric pressure, controlled by a dielectric barrier between coaxial electrodes, is investigated based on a one-dimensional self-consistent fluid model. By solving the continuity equations for electrons, ions, and excited atoms, with the current conservation equation and the electric field profile, the time evolution of the discharge current, gas voltage and the surface density of charged particles on the dielectric barrier are calculated. The simulation results show that the peak values of the discharge current, gas voltage and electric field in the first half period are asymmetric to the second half. When the current reaches its positive or negative maximum, the electric field profile, and the electron and ion densities represent similar properties to the typical glow discharge at low pressures. Obviously there exist a cathode fall, a negative glow region, and a positive column. Effects of the barrier position in between the two coaxial electrodes and the discharge gap width on discharge current characteristics are also analysed. The result indicates that, in the case when the dielectric covering the outer electrode only, the gas is punctured earlier during the former half period and later during the latter half period than other cases, also the current peak value is higher, and the difference of pulse width between the two half periods is more obvious. On reducing the gap width, the multiple current pulse discharge happens.展开更多
As advanced linear plasma sources, cascaded arc plasma devices have been used to generate steady plasma with high electron density, high particle flux and low electron temperature. To measure electron density and elec...As advanced linear plasma sources, cascaded arc plasma devices have been used to generate steady plasma with high electron density, high particle flux and low electron temperature. To measure electron density and electron temperature of the plasma device accurately, a laser Thomson scattering（LTS） system, which is generally recognized as the most precise plasma diagnostic method, has been established in our lab in Dalian University of Technology. The electron density has been measured successfully in the region of 4.5？×10^19m^-3 to7.1？×10^20m^-3 and electron temperature in the region of 0.18 eV to 0.58 eV. For comparison,an optical emission spectroscopy（OES） system was established as well. The results showed that the electron excitation temperature（configuration temperature） measured by OES is significantly higher than the electron temperature（kinetic electron temperature） measured by LTS by up to 40% in the given discharge conditions. The results indicate that the cascaded arc plasma is recombining plasma and it is not in local thermodynamic equilibrium（LTE）. This leads to significant error using OES when characterizing the electron temperature in a non-LTE plasma.展开更多
In current International Thermonuclear Experimental Reactor （ITER） design, the 316LN austenitic stainless steel （316LN SS） is used for first-wall/blanket structures. Thus, it is necessary to study the fundamental ...In current International Thermonuclear Experimental Reactor （ITER） design, the 316LN austenitic stainless steel （316LN SS） is used for first-wall/blanket structures. Thus, it is necessary to study the fundamental mechanical properties and irradiation effect of 316LN SS. A random solid solution model of Fe-Cr-Ni-Mn- Mo-Si alloy is used for describing 310LN S$. Using first-principles approaches, the elastic constants and ideal strength of the alloy were calculated. Such alloy exhibits good ductile behavior according to the theoretical values of Cauchy pressure and ratio of bulk modulus and shear modulus. Within the 256-atom supercell, inclusion of single vacancy defect further enhances the ductility of the alloy, and the existence of interstitial （Fe, H, He） atoms enhances the Young＇s modulus.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.11175035,10875023)+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(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.
基金supported by National Natural Science Foundation of China (Nos. 11475039, 11705020, 11605023)Liaoning Provincial Natural Science Foundation of China (No. 20170540153)
文摘The complex nature of laser-material interaction causes non-stoichiometric ablation of alloy samples.This is attributed to matrix effect, which reduces analyzing capability. To address this issue, the analytical performance of three different normalization methods, namely normalization with background, internal normalization and three point smoothing techniques at different parameter settings is studied for quantification of Ag and Zn by Laser induced breakdown spectroscopy(LIBS).The LIBS spectra of five known concentration of silver zinc binary composites have been investigated at various laser irradiances(LIs). Calibration curves for both Ag(I) line(4d^(10)5s^2S_(1/2)→4d^(10)5p^2P_(1/2) at 338.28 nm) and Zn(I) line(4s5s^3S_1→4s4p^3P_2 at 481.053 nm) have been determined at LI of 5.86?×?10^(10)W cm^(-2). Slopes of these calibration curves provide the valuation of matrix effect in the Ag–Zn composites. With careful sample preparation and normalization after smoothing at optimum parameter setting(OPS), the minimization of sample matrix effect has been successfully achieved. A good linearity has been obtained in Ag and Zn calibration curve at OPS when normalized the whole area of spectrum after smoothing and the obtained coefficients of determination values were R^2?=?0.995 and 0.998 closer to 1. The results of matrix effect have been further verified by analysis of plasma parameters. Both plasma parameters showed no change with varying concentration at OPS. However, at high concentration of Ag, the observed significant changes in both plasma parameters at common parameter setting PS-1 and PS-2 were the gesture of matrix effect. In our case, the better analytical results were obtained at smoothing function with optimized parameter setting that indicates it is more efficient than normalization with background and internal normalization method.
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.
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.
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.
文摘The compression creep deformation of the high volume fraction of SiC particles reinforced AI-Mg-Si composite fabricated by pressure-less infiltration was investigated. The experimental results show that the creep stress exponents are very high at temperatures of 673 K, 723 K and 773 K, and if taking the threshold stress into account, the true stress exponent of minimum creep strain rate is still approximately 5, although the volume fraction of reinforcements is very high. The creep strain rate in the high volume fraction reinforced aluminum alloy matrix composites is controlled by matrix lattice diffusion. It is found that the creep-strengthening effect of high volume fraction of silicon carbide particles is significant, although the particles do not form effective obstacles to dislocation motion.
基金supported by National Natural Science Foundation of China (Nos. 11605023, 11805028, and 11705020)the National Key R&D Program of China (No. 2017YFE0301300)+1 种基金the China Postdoctoral Science Foundation (Nos. 2017T100172 and 2016M591423)the Fundamental Research Funds for the Central Universities (Nos. DUT17RC(4)53 and DUT18LK38)
文摘The study of sulfur hexafluoride(SF6) discharge is vital for its application in gas-insulated equipment. Direct current partial discharge(PD) may cause SF6 decomposition, and the decomposed products of SF6, such as F atoms, play a dominant role in the breakdown of insulation systems. In this study, the PD caused by metal protrusion defects is simulated by a needle-plate electrode using pulsed high voltage in SF6/Ar mixtures. The spatial and temporal characteristics of SF6/Ar plasma are analyzed by measuring the emission spectra of F and Ar atoms, which are important for understanding the characteristics of PD. The spatial resolved results show that both F and Ar atom spectral intensities increase first from the plate anode to the needle and then decrease under the conditions of a background pressure of400 Pa, peak voltage of-1000 V, frequency of 2 kHz, pulse width of 60 μs, and electrode gap of 5-9 mm. However, the distribution characteristics of F and Ar are significantly different. The temporal distribution results show that the spectral intensity of Ar decreasesfirst and then increases slowly, while the spectral intensity of F increases slowly for the duration of the pulsed discharge at the electrode gap of 5 mm and the pulse width of40-80 μs.
基金Foundation item:Project(51671045)supported by the National Natural Science Foundation of ChinaProject(DUT18GF112)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(TZ2016004)supported by the Science Challenge Project,China
文摘The formation of nanoporous Pd was studied by electro-chemical dealloying a rapidly-quenched Al70Pd17Fe13 quasicrystal alloy in dilute NaCl aqueous solution,and the electro-catalytic activity of the nanoporous Pd towards methanol electro-oxidation was evaluated by cyclic voltammetry in 1 mol/L KOH solution.XRD and TEM analyses revealed that nano-decomposition of quasicrystal grains occurred in the initial stage of dealloying,and the fully dealloyed sample was composed of FCC-Pd phase.Scanning electron microscopy observation indicated that a maze-like nanoporous pattern was formed in the dealloyed sample,consisting of percolated pores of 5.20 nm in diameter in a skeleton of randomly-orientated Pd nano-ligaments with a uniform thickness of^5 nm.A retention of^12 at.%Al in the Pd nano-ligments was determined by energy dispersive X-ray spectroscopy(EDS).The nanoporous Pd demonstrated obvious electro-catalytic activity towards methanol electro-oxidation in alkaline environment.
基金Project(AWPT08-10)supported by the Open Fund of the State Key Laboratory of Advanced Welding Production Technology in Harbin Institute of Technology,ChinaProject(mmlab0706)supported by the Open Fund of the State Key Laboratory of Materials Modification by Laser,Ion and Electron Beams in Dalian University of University,ChinaProject(0710908-05-K)supported by the Research Funds of the Guangxi Key Laboratory of Information Materials in Guilin University of Electronic Technology,China
文摘To improve the wear and corrosion properties of AZ91D magnesium alloys,Cu-based amorphous composite coatings were fabricated on AZ91D magnesium alloy by laser cladding using mixed powders of Cu47Ti34Zr11Ni8 and SiC.The wear and corrosion behaviours of the coatings were investigated.The wear resistance of the coatings was evaluated under dry sliding wear condition at room temperature.The corrosion resistance of the coatings was tested in 3.5%(mass fraction) NaCl solution.The coatings exhibit excellent wear resistance due to the recombined action of amorphous phase and different intermetallic compounds.The main wear mechanisms of the coatings and the AZ91D sample are different.The former is abrasive wear and the latter is adhesive wear.The coatings compared with AZ91D magnesium alloy also exhibit good corrosion resistance because of the presence of the amorphous phase in the coatings.
基金supported by the National Magnetic Confinement Fusion Science Program of China (No. 2017YFE0301304)National Natural Science Foundation of China (Nos. 11 475 039, 11 605 023, 11 705 020)+2 种基金China Postdoctoral Science Foundation (Nos. 2016M591423, 2017T100172, 2018M630285)the Fundamental Research Funds for the Central Universities (Nos. DUT15RC(3)072, DUT17RC(4)53, DUT18LK38)Liaoning Provincial Natural Science Foundation of China (No. 20 170 540 153)
文摘An experimental setup has been designed and realized in order to optimize the characteristics of laser-induced breakdown spectroscopy system working in various pressure environments. An approach combined the normalization methods with the partial least squares(PLS) method are developed for quantitative analysis of molybdenum(Mo) element in the multi-component alloy,which is the first wall material in the Experimental Advanced Superconducting Tokamak. In this study, the different spectral normalization methods(total spectral area normalization,background normalization, and reference line normalization) are investigated for reducing the uncertainty and improving the accuracy of spectral measurement. The results indicates that the approach of PLS based on inter-element interference is significantly better than the conventional PLS methods as well as the univariate linear methods in the various pressure for molybdenum element analysis.
基金supported by "University Innovation and Research Training Program (China)" (No. 2009003)the Natural Science Foundation of Jiangsu Province (No.BK2011252)the Industry Science and Technology Supported Plan of Changzhou (No. CE20110012)
文摘Pseudobinary Ti 1 x Al x N films were synthesized on Si (100) wafer by DC magnetron sputtering method using Ti 1 x Al x alloy targets with different Al contents. The composition of the Ti 1 x Al x N films was determined by electron probe microanalysis (EPMA). Structural characteristic was performed by X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM). First principles virtual crystal calculations for the Ti 1 x Al x N disordered alloys were used for the XRD simulations. The crystalline structure of the Ti 0.61 Al 0.39 N film was found to be a metastable single phase with NaCl (B1) structure. Its lattice constant, determined by XRD, was less than that of pure TiN. With the increase of Al content, the lattice constant of B1 phase was continually decreased, while würtzite (B4) structure was observed in the Ti 0.40 Al 0.60 N film. When x reached 0.75, the B1 phase disappeared, and only B4 phase was remained. The critical Al content for the phase transition from NaCl to würtzite structure in this paper was about 0.60, which could be explained by both the thermodynamic model and the electron theory. As-deposited Ti 1 x Al x N films exhibited excellent mechanical properties. Hardness measurements of Ti 1 x Al x N films showed a high value of 45GPa for x=0.39 and was decreased to value of 27 GPa with increasing Al at x=0.60.
基金supported by the Cultivation Fund of the Key Scientific and Technical Innovation Project, Ministry of Education of China (No. 707015)University Innovative Research Team Project of Liaoning Province
文摘Hydrogenated microcrystalline silicon thin films (μc-Si:H) were deposited by plasma assistant magnetron sputtering in Ar-H 2 gas mixture. The effects of growth temperature from 150 to 450 C on properties of deposited Si films were investigated at two different hydrogen diluted gases with [H 2 ]/([Ar]+[H 2 ]) of 10% and 50% at 3 Pa. The crystallinity of Si films examined by Raman scattering exhibited higher degrada- tion by lowering growth temperature from 250 to 150 C in low hydrogen diluted gas of 10% than that in high hydrogen diluted gas of 50%. The IR absorption band around 845 and 890 cm 1 as well as calculated concentration of bonded hydrogen showed more obvious decrease of samples deposited in low hydrogen diluted gas of 10% than that in high hydrogen diluted gas of 50%. The optical band gasps of both groups of samples measured by ultraviolet-visible optical absorption were decreased with increasing temperature in both gas conditions.
基金supported financially by the National Natural Science Foundation of China(Grant Nos.51571047,51171034)the Fundamental Research Funds for the Central Universities(DUT17ZD212)the Global Institute for Materials Research Tohoku Program,Japan。
文摘A nanoporous FePt alloy has been fabricated by dealloying a melt-spun Fe(60)Pt(20)B(20)alloy composed of nanoscale amorphous and face-centered-cubic FePt(fcc-FePt)phases in H2 SO4 aqueous solution.The nanoporous alloy consists of single fcc-FePt phase with an Fe/Pt atomic ratio of about 55.3/44.7,and possesses a uniform interpenetrating ligament-channel structure with average ligament and pore sizes of 27 nm and 12 nm,respectively.The nanoporous fcc-FePt alloy shows soft magnetic characteristics with a saturation magnetization of 37.9 emu/g and better electrocatalytic activity for methanol oxidation than commercial Pt/C in acidic environment.The phase transformation from disordered fcc-Fe Pt into ordered face-centered-tetragonal FePt(L10-FePt)in the nanoporous alloy has been realized after annealing at823-943 K for 600 s.The volume fraction of the L10-FePt phase in the alloy increases with the rise of annealing temperature,which results in the enhancements of coercivity and saturation magnetization from 0.14 kOe and 38.5 emu/g to 8.42 kOe and 51.4 emu/g,respectively.The ligament size of the samples is increased after annealing.
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Project supported by the National Natural Science Foundation of China （Grant Nos 50537020 and 50528707）.
文摘The glow discharge in pure helium at atmospheric pressure, controlled by a dielectric barrier between coaxial electrodes, is investigated based on a one-dimensional self-consistent fluid model. By solving the continuity equations for electrons, ions, and excited atoms, with the current conservation equation and the electric field profile, the time evolution of the discharge current, gas voltage and the surface density of charged particles on the dielectric barrier are calculated. The simulation results show that the peak values of the discharge current, gas voltage and electric field in the first half period are asymmetric to the second half. When the current reaches its positive or negative maximum, the electric field profile, and the electron and ion densities represent similar properties to the typical glow discharge at low pressures. Obviously there exist a cathode fall, a negative glow region, and a positive column. Effects of the barrier position in between the two coaxial electrodes and the discharge gap width on discharge current characteristics are also analysed. The result indicates that, in the case when the dielectric covering the outer electrode only, the gas is punctured earlier during the former half period and later during the latter half period than other cases, also the current peak value is higher, and the difference of pulse width between the two half periods is more obvious. On reducing the gap width, the multiple current pulse discharge happens.
基金supported by the National Magnetic Confinement Fusion Science Program of China(No.2013GB109005)the Fundamental Research Funds for the Central Universities(Nos.DUT15RC(3)072,DUT15TD44,DUT16TD13)
文摘As advanced linear plasma sources, cascaded arc plasma devices have been used to generate steady plasma with high electron density, high particle flux and low electron temperature. To measure electron density and electron temperature of the plasma device accurately, a laser Thomson scattering（LTS） system, which is generally recognized as the most precise plasma diagnostic method, has been established in our lab in Dalian University of Technology. The electron density has been measured successfully in the region of 4.5？×10^19m^-3 to7.1？×10^20m^-3 and electron temperature in the region of 0.18 eV to 0.58 eV. For comparison,an optical emission spectroscopy（OES） system was established as well. The results showed that the electron excitation temperature（configuration temperature） measured by OES is significantly higher than the electron temperature（kinetic electron temperature） measured by LTS by up to 40% in the given discharge conditions. The results indicate that the cascaded arc plasma is recombining plasma and it is not in local thermodynamic equilibrium（LTE）. This leads to significant error using OES when characterizing the electron temperature in a non-LTE plasma.
基金supported by the National Magnetic Confinement Fusion Program (2011GB108007)Fundamental Research Funds for the Central Universities of China (No. DUT10ZD211)
文摘In current International Thermonuclear Experimental Reactor （ITER） design, the 316LN austenitic stainless steel （316LN SS） is used for first-wall/blanket structures. Thus, it is necessary to study the fundamental mechanical properties and irradiation effect of 316LN SS. A random solid solution model of Fe-Cr-Ni-Mn- Mo-Si alloy is used for describing 310LN S$. Using first-principles approaches, the elastic constants and ideal strength of the alloy were calculated. Such alloy exhibits good ductile behavior according to the theoretical values of Cauchy pressure and ratio of bulk modulus and shear modulus. Within the 256-atom supercell, inclusion of single vacancy defect further enhances the ductility of the alloy, and the existence of interstitial （Fe, H, He） atoms enhances the Young＇s modulus.
