A characteristic CaO-Al2O3-SiO2 based foam ceramic was prepared by melt-foaming with solid wastes as main raw materials.The similarity to sandwich hole wall microstructure of this novel thermal insulating material was...A characteristic CaO-Al2O3-SiO2 based foam ceramic was prepared by melt-foaming with solid wastes as main raw materials.The similarity to sandwich hole wall microstructure of this novel thermal insulating material was presented and the relationships between this unique microstructure and porosity,density,thermal conductivity and strength were discussed.Comparing the measured and theoretical values with that of the traditional foam ceramic,it can be found that,for the matching of fine skeleton with hole wall,this original sandwich structure can reduce thermal conductivity and increase flexural strength effectively.展开更多
In the present study,WB 2（N） films are fabricated on silicon and YG8 substrates at different N 2 pressures by reactive magnetron sputtering.The influence of N 2 partial pressure（P （N2）） on the film microstructur...In the present study,WB 2（N） films are fabricated on silicon and YG8 substrates at different N 2 pressures by reactive magnetron sputtering.The influence of N 2 partial pressure（P （N2）） on the film microstructure and characteristics is studied systematically,including the chemical composition,crystalline structure,residual stress,surface roughness as well as the surface and the cross-section morphology.Meanwhile,nano-indentation and ball-on-disk tribometer are performed to analyze the mechanical and tribological properties of the films.The results show that the addition of nitrogen apparently leads to the change of the structure from（1 0 1） to（0 0 1） orientation then to the amorphous structure with the formation of BN phase.And the addition of nitrogen can greatly refine the grain size and microstructure of the films.Furthermore,the residual stress of the film is also found to change from tensile to compressive stress as a function of P （N2）,and the compressive stress increases with P （N2）,The WB 2（N） films with small nitrogen content,which are deposited at P （N2） of 0.004 and 0.006 Pa,exhibit better mechanical,tribological and corrosion properties than those of other films.Further increase of nitrogen content accelerates the formation of BN phase and fast decreases the film hardness.In addition,the large N 2 partial pressure gives rise to the target poisoning accompanied by the increase of the target voltage and the decrease of the deposition rate.展开更多
The influence of the bilayer number on the microstructure,mechanical properties,adhesion strength and tribological behaviors of the WB_(2)/Cr multilayer films was systematically investigated in the present study.Five ...The influence of the bilayer number on the microstructure,mechanical properties,adhesion strength and tribological behaviors of the WB_(2)/Cr multilayer films was systematically investigated in the present study.Five groups of WB_(2)/Cr films with the same modulation ratio were synthesized by magnetron sputtering technique.The crystalline structure of the films was determined by X-ray diffraction.The morphologies and the microstructure of the films were observed by scanning electron microscopy,atomic force microscopy and transmission electron microscopy.Furthermore,Nano indenter,scratch tester and ball-on-disc tribometer were used to evaluate the mechanical and tribological properties.As bilayer numbers varied from 5 to 40,the hardness increased first and then decreased with the maximum hardness of 33.9 GPa when the bilayer number is 30.The H/E^(*)and H^(3)/E^(*2)values calculated to evaluate the fracture toughness showed the similar changing trend with hardness.The adhesion strength reached the maximum of 67 N when the bilayer number is 30.The surface roughness and friction coefficient decreased with increasing bilayer number.The wear mechanism was also investigated,and the results suggested that the multilayer film with bilayer number of 30 exhibited the best wear resistance(1.78×10^(–7)mm^(3)/Nm),benefiting from the contribution of high hardness,fracture toughness and adhesion strength.展开更多
For deep geological disposal of high-level radioactive waste(HLW)in granite,the temperature on the HLW canisters is commonly designed to be lower than100fiC.This criterion dictates the dimension of the repository.Base...For deep geological disposal of high-level radioactive waste(HLW)in granite,the temperature on the HLW canisters is commonly designed to be lower than100fiC.This criterion dictates the dimension of the repository.Based on the concept of HLW disposal in vertical boreholes,thermal process in the nearfield(host rock and buffer)surrounding HLW canisters has been simulated by using different methods.The results are drawn as follows:(a)the initial heat power of HLW canisters is the most important and sensitive parameter for evolution of temperaturefield;(b)the thermal properties and variations of the host rock,the engineered buffer,and possible gaps between canister and buffer and host rock are the additional key factors governing the heat transformation;(c)the gaps width and thefilling by water or air determine the temperature offsets between them.展开更多
Vacuum brazing was successfully used to join Ti-22Al-25Nb alloy using Ti-Ni-Nb brazing alloys prepared by arc-melting. The influence of Nb content in the Ti-Ni-Nb brazing alloys on the interfacial microstructure and m...Vacuum brazing was successfully used to join Ti-22Al-25Nb alloy using Ti-Ni-Nb brazing alloys prepared by arc-melting. The influence of Nb content in the Ti-Ni-Nb brazing alloys on the interfacial microstructure and mechanical properties of the brazed joints was investigated. The results showed that the interfacial microstructure of brazed joint consisted of B2, O, ？3, and Ti2 Ni phase, while the width of brazing seams varied at different Nb contents. The room temperature shear strength reached359 MPa when the joints were brazed with eutectic Ti40Ni40Nb20 alloy at 1180？C for 20 min, and it was321, 308 and 256 MPa at 500, 650 and 800？C, respectively. Cracks primarily initiated and propagated in ？3compounds, and partially traversed B2＋O region. Moreover, the fracture surface displayed typical ductile dimples when cracks propagated through B2＋O region, which was favorable for the mechanical properties of the brazed joint.展开更多
An Al-12 Si/Al-3.5 Cu-1.5 Mg-1 Si bimetal with a good interface was successfully produced by selective laser melting(SLM).The SLM bimetal exhibits four successive zones along the building direction:an Al-12 Si zone,an...An Al-12 Si/Al-3.5 Cu-1.5 Mg-1 Si bimetal with a good interface was successfully produced by selective laser melting(SLM).The SLM bimetal exhibits four successive zones along the building direction:an Al-12 Si zone,an interfacial zone,a texture-strengthening zone and an Al-Cu-Mg-Si zone.The interfacial zone(<0.2 mm thick)displays an increasing size of the cells composed of eutectic Al-Si and a discontinuous cellular microstructure,resulting in the lowest hardness of the four zones.The texturestrengthening zone(around 0.3 mm thick)shows a remarkable variation of the hardness and<001>fiber texture.Electron backscatter diffraction analysis shows that the grains grow gradually from the interfacial zone to the Al-Cu-Mg-Si zone along the building direction.Additionally,a strong<001>fiber texture develops at the Al-Cu-Mg-Si side of the interfacial zone and disappears gradually along the building direction.The bimetal exhibits a room temperature yield strength of 267±10 MPa and an ultimate tensile strength of 369±15 MPa with elongation of 2.6±0.1%,revealing the potential of selective laser melting in manufacturing dissimilar materials.展开更多
Although different types of powder feedstock are used for additive manufacturing via laser powder bed fusion(L-PBF),limited work has attempted to directly compare the microstructure and mechanical behavior of componen...Although different types of powder feedstock are used for additive manufacturing via laser powder bed fusion(L-PBF),limited work has attempted to directly compare the microstructure and mechanical behavior of components manufactured from those powder feedstock.This work investigated the microstructure,phase composition,melt pool morphology,and mechanical properties of a prealloyed Ti-35Nb alloy manufactured using L-PBF and compared these to their counterparts produced from elemental powder mixture.The samples manufactured from the powder mixture are composed of randomly distributed undissolved Nb in theα/βmatrix,resulting from the unstable melt pool during the melting of the powder mixture.By contrast,parts produced from prealloyed powder display a homogeneous microstructure withβandαphases,owing to the full melting of prealloyed powder,therefore,a more stable melt pool to achieve a homogeneous microstructure.The Ti-35Nb manufactured from prealloyed powder exhibits large tensile ductility(about 10 times that of the counterparts using mixed powder),attributed to the high homogeneity in microstructure and chemical composition,strong interface bonding,relatively low oxygen content,and the existence of a large amount ofβphase.This work sheds insights into understanding the effect of powder feedstock on the melt pool stability therefore the microstructure and mechanical behavior of the resultant parts.展开更多
The insensitivity of semiconductors to visible and infrared light is a key constraint on the utilization of light energy in photocatalytic reactions.Constructing photocatalysts with full-spectrum absorption through su...The insensitivity of semiconductors to visible and infrared light is a key constraint on the utilization of light energy in photocatalytic reactions.Constructing photocatalysts with full-spectrum absorption through surface engineering is an effective approach to fully harnessing light energy in semiconductor materials.Herein,a novel stable Ti_(3)C_(2)T_(x)MXene/CdS heterojunction catalyst is obtained by in-situ epitaxial growth of two-dimensional(2D)CdS nanosheets on 2D MXene interface via a solvothermal method.The exceptional light absorption properties of MXene confer outstanding full-spectrum driven photocat-alytic hydrogen evolution capability upon the heterogeneous catalyst.The unique 2D/2D structure effectively mitigated the recombination of photogenerated carriers,enhancing the photocatalytic performance of the catalyst.Moreover,the composite catalyst exhibits a significantly higher surface temperature of 80.4℃under visible light irradiation at an intensity of 0.1 W/cm^(2),which is 1.84 times higher than that of CdS.Under irradiation of visible and near infrared light,the composite catalyst with photothermal ef-fect demonstrates a remarkable hydrogen evolution rate of 65.4 mmol g^(-1)h^(-1),which is 7.2 times higher than that of CdS catalyst.This study introduces a novel approach for constructing full-spectrum absorption catalysts and expands the application of the photothermal effect in photocatalytic hydrogen evolution research.展开更多
The physics of laser-plasma interaction is studied on the Shenguang III prototype laser facility under conditions relevant to inertial confinement fusion designs.A sub-millimeter-size underdense hot plasma is created ...The physics of laser-plasma interaction is studied on the Shenguang III prototype laser facility under conditions relevant to inertial confinement fusion designs.A sub-millimeter-size underdense hot plasma is created by ionization of a low-density plastic foam by four high-energy(3.2 kJ)laser beams.An interaction beam is fired with a delay permitting evaluation of the excitation of parametric instabilities at different stages of plasma evolution.Multiple diagnostics are used for plasma characterization,scattered radiation,and accelerated electrons.The experimental results are analyzed with radiation hydrodynamic simulations that take account of foam ionization and homogenization.The measured level of stimulated Raman scattering is almost one order of magnitude larger than that measured in experiments with gasbags and hohlraums on the same installation,possibly because of a greater plasma density.Notable amplification is achieved in high-intensity speckles,indicating the importance of implementing laser temporal smoothing techniques with a large bandwidth for controlling laser propagation and absorption.展开更多
AI matrix composite containing high volume fraction silicon has been promising candidate for lightweight and low-thermal-expansion components. Whereas, optimization of its mechanical properties still is an open challe...AI matrix composite containing high volume fraction silicon has been promising candidate for lightweight and low-thermal-expansion components. Whereas, optimization of its mechanical properties still is an open challenge. In this article, a flexile powder metallurgy processing was used to produce a fully dense AI-4.0Cu （wt%） alloy composite reinforced with 65 vol.% Si particles. In this composite, Si particles were homogenously distributed, and the particle size was refined to the range of 3-15 μm. Tensile and flexural strength of the composite were 282 and 455 MPa, respectively, about 100% and 50% higher than the best properties reported in literature. The measured fracture toughness of the composite was 4.90 MPa m1/2. The improved strength of 65%Si/AI was attributed to the optimized particle characteristics and matrix properties. This investigation is expected to provide a primary understanding of the mechanical behaviors of Si/AI composites, and also promote the structural applications of this low-thermal-expansion material.展开更多
Background Each GECAM satellite payload contains 25 gamma-ray detectors(GRDs),which can detect gamma-rays and particles and can roughly localize the Gamma-Ray Bursts(GRBs).GRD was designed using lanthanum bromide(LaBr...Background Each GECAM satellite payload contains 25 gamma-ray detectors(GRDs),which can detect gamma-rays and particles and can roughly localize the Gamma-Ray Bursts(GRBs).GRD was designed using lanthanum bromide(LaBr3)crystal as the sensitive material with the rear end coupled with silicon photomultiplier(SiPM)array for readout.Purpose In aerospace engineering design of GRD,there are many key points to be studied.In this paper,we present the specific design scheme of GRD,the assembly and the performance test results of detectors.Methods Based on Monte Carlo simulation and experimental test results,the specific schematic design and assembling process of GRD were optimized.After being fully assembled,the GRDs were conducted performance tests by using radioactive source and also conducted random vibration tests.Result and conclusion The test results show that all satellite-borne GRDs have energy resolution<16%at 59.5 keV,meeting requirements of satellite in scientific performance.The random vibration test shows that GRD can maintain in a stable performance,which meets the requirement of spatial application.展开更多
Background The Gravitational wave highly energetic Electromagnetic Counterpart All-sky Monitor(GECAM)is dedicated to detecting gravitational wave gamma-ray bursts.It is capable of all-sky monitoring over and discoveri...Background The Gravitational wave highly energetic Electromagnetic Counterpart All-sky Monitor(GECAM)is dedicated to detecting gravitational wave gamma-ray bursts.It is capable of all-sky monitoring over and discovering gamma-ray bursts and new radiation phenomena.GECAM consists of two microsatellites,each equipped with 8 charged particle detectors(CPDs)and 25 gamma-ray detectors(GRDs).Purpose The CPD is used to measure charged particles in the space environment,monitor energy and flow intensity changes,and identify between gamma-ray bursts and space charged particle events in conjunction with GRD.Methods CPD uses plastic scintillator as the sensitive material for detection,silicon photomultiplier array as the optically readable device,and the inlaid Am-241 radioactive source as the onboard calibration means.Conclusion In this paper,we will present the working principle,physical design,functional implementation and preliminary performance test results of the CPD.As a result,the energy range of electron,gamma-ray detection efficiency and dead time are tested to be better than the indexes required through the ground calibration experiment.展开更多
A 2D full cell thermo-electric model of 160kA drained cell was set up using finiteelement code to calculate its freeze profile, then the drained cell model was modifiedaccording to the freeze profile computed and its ...A 2D full cell thermo-electric model of 160kA drained cell was set up using finiteelement code to calculate its freeze profile, then the drained cell model was modifiedaccording to the freeze profile computed and its heat balance was calculated. Comparedwith that of a 160kA conventional Hall-Heroult cell (H-H cell), though the melts vol-ume of the drained cell reduced greatly, the whole heat loss from it didn't drop downapparently, and an analysis was presented in the paper. On the other hand, the anode-cathode distance (ACD) of a drained cell was much less than that of a H-H cell, sothe voltage drop on it and heat produced decreased too, steps should be taken to keepa workable heat balance on a drained cell.展开更多
The characterization of multiple iron-rich phases in high-pressure die-cast AlSi10MnMg alloy was studied.Attention was focused on the formation and fracture behavior of the primary iron-rich phase((P-IMC)_(I))formed i...The characterization of multiple iron-rich phases in high-pressure die-cast AlSi10MnMg alloy was studied.Attention was focused on the formation and fracture behavior of the primary iron-rich phase((P-IMC)_(I))formed in the shot sleeve and plate-shaped eutectic iron-rich phase in high-pressure die cast(HPDC)AlSi10MnMg alloy.Results show that multiple types of iron-rich phases with various morphologies,in-cluding primary iron-rich phases(polyhedral(P-IMC)_(I) and(P-IMC)_(II))and eutectic iron-rich phases(plate-shaped,net shape,and fish-bone shape),were found in HPDC AlSi10MnMg.Coarse(P-IMC)_(I) formed in the shot sleeve were distributed in the interface between primaryα-Al and binary Al-Si eutectic.Small size(P-IMC)_(II) and various eutectic iron-rich phases formed in the die cavity and they were distributed in Al-Si binary eutectic.The primary iron-rich phases belonged to a simple cubic crystal structure with a lattice constant a=1.265 nm and they exhibited a lateral growth characteristic with a termination of{110}surface.βphase was surrounded byδphase and they coexisted in a plate-shaped iron-rich phase.High-density stacking fault inβphase andδ/βinterface provided an excellent nucleation site forδphase.From mechanical behavior,the stress concentration caused by eutectic iron-rich phases was far less than(P-IMC)_(I) and it would not cause crack initiation along the eutectic cluster boundary.In addition,(P-IMC)_(I) showed the worst deformation coordination with primaryα-Al while the plate-shaped eutectic iron-rich phase exhibited similar deformation characteristics with silicon particles.展开更多
Inferior absolute strength and dissolution properties are the main bottlenecks for the widespread application of dissolvable magnesium alloys in complex working environments for unconventional oil and gas resources.He...Inferior absolute strength and dissolution properties are the main bottlenecks for the widespread application of dissolvable magnesium alloys in complex working environments for unconventional oil and gas resources.Here,a novel functional peak-aged Mg-9.5Gd-2.7Y-0.9Zn-0.8Cu-0.4Ni(wt.%) alloy for fracturing tools is reported,and it possesses an ultimate tensile strength of 457.6 MPa,ultimate compressive strength of 620.7 MPa and dissolution rate of ~43.7 mg·cm^(-2)·h^(-1) in 3 wt.% KCl solutions at 93℃.The excellent strength of the agedalloy is primarily attributed to the combination of grain refinement,long-period stacking ordered(LPSO) strengthening,and precipitation strengthening induced by stacking fault and β’ phase,among which the precipitation strengthening is dominant.Further investigations confirm that the corrosion is triggered from the micro-galvanic coupling between the Mg matrix and the cathodic lamellar and block LPSO phases.Strip-shaped corrosion pits along with LPSO phases are subsequently formed,significantly accelerating corrosion.The β’ precipitates can effectively improve the strength without compromising the dissolution rate because of their nanoscale size.This study provides an excellent material selection for dissolvable fracturing tools and presents a strategy by which a synergistic combination of strength and dissolution rate is achieved via peak-aging treatment.展开更多
Introduction The main physical objective of the GECAM satellite is to detect gamma-ray bursts,which is related to gravitational waves of double compact object mergers.The GECAM satellite also detects and investigates ...Introduction The main physical objective of the GECAM satellite is to detect gamma-ray bursts,which is related to gravitational waves of double compact object mergers.The GECAM satellite also detects and investigates various bursts of high-energy celestial bodies.Purposes and methods In this study,we designed,developed and calibrated the payload and launched it into orbit with GECAM satellite.The payload consists of the gamma ray detector(GRD,for detecting 4 keV–4 MeV X/γray),the charged particle detector(CPD,for detecting 150 keV–5 MeV charged particle),and the electronic box(EBOX).The all-sky field coverage is achieved via two 229-degree large-area satellites positioned 180 degrees apart and are on opposite sides of the geo-center.Each satellite is equipped with 25 GRDs and 8 CPDs;thus,the satellite can identify charged particle bursts in space.Gamma-ray detectors adopt lanthanum bromide crystal technology combined with silicon photomultipliers.This is the first time that this technology was used massively in space detectors.Conclusions The GECAM satellite can quickly determine the direction of gamma-ray bursts(positioning)via indexing and fitting method,while the transmit variability,energy spectrum and direction of the gamma-ray bursts guide subsequent observations through the Beidou-3 RDSS in quasi-real time.It will play an important role in the study of high energy celestial bursts.展开更多
Background The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)satellite developed a SiPM-based gamma-ray detector to monitor the gravitational wave-related GRBs and guide subsequent o...Background The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)satellite developed a SiPM-based gamma-ray detector to monitor the gravitational wave-related GRBs and guide subsequent observations in other wavelengths of EM.Purpose As all the available SiPM devices belong to commercial grade,quality assurance tests need to be performed in accordance with the aerospace specifcations.Methods In the SiPM application of GECAM,quality assurance experiments were conducted.The mechanism of the failure of SiPM devices was analyzed during the development process.Result Based on the quality assurance test results,the fnal pass rate of SiPM array was 95%.Based on the failure analysis,it was found that a piece of SiPM had a leakage channel after longtime operation due to device defects.Conclusion According to the accumulated experience,in the reliability test of SiPM,it is necessary to pay special attention to test the impedance of each pin of SiPM to ground and confrm that the power switch state of SiPM is controllable.展开更多
Purpose The discovery of gravitational waves and gamma-ray bursts heralds the era of multi-messenger astronomy.With the adoption of two small satellites to achieve the all-sky monitoring of gamma-ray bursts,the gravit...Purpose The discovery of gravitational waves and gamma-ray bursts heralds the era of multi-messenger astronomy.With the adoption of two small satellites to achieve the all-sky monitoring of gamma-ray bursts,the gravitational wave highenergy electromagnetic counterpart all-sky monitor(GECAM)possesses a quasi-real-time early warning ability and plays an important role in positioning the sources of gravitational waves and in subsequent observations.Each satellite of GECAM was fitted with 253-inch-diameter gamma-ray detectors(GRD),covering an energy range of 8–2 MeV.GRDs have adopted silicon photomultiplier tubes(SiPM)in lieu of photomultiplier tubes(PMT)to adapt to the dimensional limitations of micro-satellites.Methods A unique 3-inch circular SiPM array was designed.In this design,646×6 mm chips were arranged evenly in a circular manner with the seams filled with reflecting films,thus achieving satisfactory uniformity of light collection.The integrated pre-amplifier circuit on the back of the SiPM array adopted two-level grouping and summing;further,it achieved a satisfactory signal-to-noise ratio.Two high-gain and low-gain channels were adopted to achieve a large dynamic range,and two independent power supply units were used,where each unit can be closed separately,thus improving reliability.Results Performance studies show that this SiPM array meets the requirements of GECAM.Conclusion A 3-inch SiPM array have been developed that uses grouped summation,reflective films,a circular arrangement,two groups of independent power supplies,high-and low-gain signals,differential signal output technologies,etc.This solution can be used not only for GECAM,but also as a general solution for SiPM-based scintillation detectors.展开更多
Background The Gravitational Wave High-energy Electromagnetic Counterpart All-sky Monitor(GECAM)consists of 2 microsatellites,each of which contains 25 GRD(LaBr3)detectors and 8 CPD(plastic scintillator)detectors.Meth...Background The Gravitational Wave High-energy Electromagnetic Counterpart All-sky Monitor(GECAM)consists of 2 microsatellites,each of which contains 25 GRD(LaBr3)detectors and 8 CPD(plastic scintillator)detectors.Method silicon photomultiplier(SiPM)array is used to read each detector.The output signal of these detectors with SiPM array is very special and challenging to readout.In this study,a novel data acquisition(DAQ)algorithm for these detectors is designed and implemented,and the content of the output event packet is defined.Result and Conclusion The performances,including the event acquisition efficiency of this DAQ algorithm,are extensively verified through experimental tests.From the on-ground and in-flight tests,this algorithm has excellent performance despite the very limited resources and short development time of GECAM mission.展开更多
In order to improve the oxidation and wear resistance of blades tip of titanium alloys as well as the sealing performance of the gas turbine engine,a Ni/cBN abrasive coating was prepared on titanium alloys through com...In order to improve the oxidation and wear resistance of blades tip of titanium alloys as well as the sealing performance of the gas turbine engine,a Ni/cBN abrasive coating was prepared on titanium alloys through composite electroplating.Oxidation,mechanical and tribological properties of the abrasive coating were investigated.Furthermore,the effect of the oxidation on the mechanical and tribological properties was also evaluated.Oxidation results revealed that the abrasive coating underwent slight oxidation within 700℃.Meanwhile,some intermetallic compounds,Ni3Ti,NiTi and NiTi2,were formed at the coating/substrate interface during oxidation.Due to the pinning effect of cBN particles and the different thermal expansion coefficients of the coating and substrate,the coating/substrate interface was cracked after oxidation at 700℃.Tensile results showed that the presence of coating reduced the strength of the alloy significantly at room temperature,while only marginal variations of the strength of the coated and uncoated specimens at elevated temperatures.Besides,the wear tests indicated that the coating had the excellent cutting ability and wear resistance,which can effectively protect the blades tip of titanium alloys.As the temperature increased,the wear resistance decreased due to the decrease in the mechanical properties of the Ni/cBN coating.展开更多
基金financial support of the project from the National Natural Science Foundation of China(51172016)。
文摘A characteristic CaO-Al2O3-SiO2 based foam ceramic was prepared by melt-foaming with solid wastes as main raw materials.The similarity to sandwich hole wall microstructure of this novel thermal insulating material was presented and the relationships between this unique microstructure and porosity,density,thermal conductivity and strength were discussed.Comparing the measured and theoretical values with that of the traditional foam ceramic,it can be found that,for the matching of fine skeleton with hole wall,this original sandwich structure can reduce thermal conductivity and increase flexural strength effectively.
基金supported by the National Key Basic Research Program of China (973 Program,No.2012CB625100)the Natural Science Foundation of Liaoning Province of China (No.2013020093)
文摘In the present study,WB 2（N） films are fabricated on silicon and YG8 substrates at different N 2 pressures by reactive magnetron sputtering.The influence of N 2 partial pressure（P （N2）） on the film microstructure and characteristics is studied systematically,including the chemical composition,crystalline structure,residual stress,surface roughness as well as the surface and the cross-section morphology.Meanwhile,nano-indentation and ball-on-disk tribometer are performed to analyze the mechanical and tribological properties of the films.The results show that the addition of nitrogen apparently leads to the change of the structure from（1 0 1） to（0 0 1） orientation then to the amorphous structure with the formation of BN phase.And the addition of nitrogen can greatly refine the grain size and microstructure of the films.Furthermore,the residual stress of the film is also found to change from tensile to compressive stress as a function of P （N2）,and the compressive stress increases with P （N2）,The WB 2（N） films with small nitrogen content,which are deposited at P （N2） of 0.004 and 0.006 Pa,exhibit better mechanical,tribological and corrosion properties than those of other films.Further increase of nitrogen content accelerates the formation of BN phase and fast decreases the film hardness.In addition,the large N 2 partial pressure gives rise to the target poisoning accompanied by the increase of the target voltage and the decrease of the deposition rate.
基金supported by the National Natural Science Foundation of China(No.51701157)。
文摘The influence of the bilayer number on the microstructure,mechanical properties,adhesion strength and tribological behaviors of the WB_(2)/Cr multilayer films was systematically investigated in the present study.Five groups of WB_(2)/Cr films with the same modulation ratio were synthesized by magnetron sputtering technique.The crystalline structure of the films was determined by X-ray diffraction.The morphologies and the microstructure of the films were observed by scanning electron microscopy,atomic force microscopy and transmission electron microscopy.Furthermore,Nano indenter,scratch tester and ball-on-disc tribometer were used to evaluate the mechanical and tribological properties.As bilayer numbers varied from 5 to 40,the hardness increased first and then decreased with the maximum hardness of 33.9 GPa when the bilayer number is 30.The H/E^(*)and H^(3)/E^(*2)values calculated to evaluate the fracture toughness showed the similar changing trend with hardness.The adhesion strength reached the maximum of 67 N when the bilayer number is 30.The surface roughness and friction coefficient decreased with increasing bilayer number.The wear mechanism was also investigated,and the results suggested that the multilayer film with bilayer number of 30 exhibited the best wear resistance(1.78×10^(–7)mm^(3)/Nm),benefiting from the contribution of high hardness,fracture toughness and adhesion strength.
文摘For deep geological disposal of high-level radioactive waste(HLW)in granite,the temperature on the HLW canisters is commonly designed to be lower than100fiC.This criterion dictates the dimension of the repository.Based on the concept of HLW disposal in vertical boreholes,thermal process in the nearfield(host rock and buffer)surrounding HLW canisters has been simulated by using different methods.The results are drawn as follows:(a)the initial heat power of HLW canisters is the most important and sensitive parameter for evolution of temperaturefield;(b)the thermal properties and variations of the host rock,the engineered buffer,and possible gaps between canister and buffer and host rock are the additional key factors governing the heat transformation;(c)the gaps width and thefilling by water or air determine the temperature offsets between them.
基金supported by the National Natural Science Foundation of China (Grant No. 51574177)the China Natural Founds for Distinguished Young Scientists (Grant No. 51325401)the National High Technology Research and Development Program of China (“863” Program, Granted No. 2015AA042504)
文摘Vacuum brazing was successfully used to join Ti-22Al-25Nb alloy using Ti-Ni-Nb brazing alloys prepared by arc-melting. The influence of Nb content in the Ti-Ni-Nb brazing alloys on the interfacial microstructure and mechanical properties of the brazed joints was investigated. The results showed that the interfacial microstructure of brazed joint consisted of B2, O, ？3, and Ti2 Ni phase, while the width of brazing seams varied at different Nb contents. The room temperature shear strength reached359 MPa when the joints were brazed with eutectic Ti40Ni40Nb20 alloy at 1180？C for 20 min, and it was321, 308 and 256 MPa at 500, 650 and 800？C, respectively. Cracks primarily initiated and propagated in ？3compounds, and partially traversed B2＋O region. Moreover, the fracture surface displayed typical ductile dimples when cracks propagated through B2＋O region, which was favorable for the mechanical properties of the brazed joint.
基金supported by the Shenzhen Peacock Innovation Project(KQJSCX20170327150948772,KQJSCX20170727101223535,and KQJSCX20170327151307811)the Key Project Fund for Science and Technology Development of Guangdong Province(2017B090911014)+1 种基金support was provided by the European Research Council(ERC)under the ERC Advanced Grant INTELHYB(ERC-2013-ADG-340025)the National Natural Science Foundation of China(51771123)。
文摘An Al-12 Si/Al-3.5 Cu-1.5 Mg-1 Si bimetal with a good interface was successfully produced by selective laser melting(SLM).The SLM bimetal exhibits four successive zones along the building direction:an Al-12 Si zone,an interfacial zone,a texture-strengthening zone and an Al-Cu-Mg-Si zone.The interfacial zone(<0.2 mm thick)displays an increasing size of the cells composed of eutectic Al-Si and a discontinuous cellular microstructure,resulting in the lowest hardness of the four zones.The texturestrengthening zone(around 0.3 mm thick)shows a remarkable variation of the hardness and<001>fiber texture.Electron backscatter diffraction analysis shows that the grains grow gradually from the interfacial zone to the Al-Cu-Mg-Si zone along the building direction.Additionally,a strong<001>fiber texture develops at the Al-Cu-Mg-Si side of the interfacial zone and disappears gradually along the building direction.The bimetal exhibits a room temperature yield strength of 267±10 MPa and an ultimate tensile strength of 369±15 MPa with elongation of 2.6±0.1%,revealing the potential of selective laser melting in manufacturing dissimilar materials.
基金the support of the Australian Government Research Training Program Scholarship and Forrest Research Foundation Ph D scholarshipthe fnancial support provided by the Open Foundation of Guangxi Key Laboratory of Processing for Non-ferrous Metals and Featured Materials(No.2021GXYSOF03)and the facilitiesthe scientifc and technical assistance of the Australian Microscopy&Microanalysis Research Facility at the Centre for Microscopy,Characterisation&Analysis,The University of Western Australia,a facility funded by the University,State and Commonwealth Governments。
文摘Although different types of powder feedstock are used for additive manufacturing via laser powder bed fusion(L-PBF),limited work has attempted to directly compare the microstructure and mechanical behavior of components manufactured from those powder feedstock.This work investigated the microstructure,phase composition,melt pool morphology,and mechanical properties of a prealloyed Ti-35Nb alloy manufactured using L-PBF and compared these to their counterparts produced from elemental powder mixture.The samples manufactured from the powder mixture are composed of randomly distributed undissolved Nb in theα/βmatrix,resulting from the unstable melt pool during the melting of the powder mixture.By contrast,parts produced from prealloyed powder display a homogeneous microstructure withβandαphases,owing to the full melting of prealloyed powder,therefore,a more stable melt pool to achieve a homogeneous microstructure.The Ti-35Nb manufactured from prealloyed powder exhibits large tensile ductility(about 10 times that of the counterparts using mixed powder),attributed to the high homogeneity in microstructure and chemical composition,strong interface bonding,relatively low oxygen content,and the existence of a large amount ofβphase.This work sheds insights into understanding the effect of powder feedstock on the melt pool stability therefore the microstructure and mechanical behavior of the resultant parts.
基金supported by the National Natural Science Foundation of China(Nos.22078118,21972048,22274059)the Guangdong Laboratory of Lingnan Modern Agriculture Project(Nos.NZ2021029,NT2021010)+1 种基金the Guangzhou Science and Technology Planning Project(No.202201010728)the Guangdong Provincial Key Laboratory of Distributed Energy Systems(No.2020B1212060075).
文摘The insensitivity of semiconductors to visible and infrared light is a key constraint on the utilization of light energy in photocatalytic reactions.Constructing photocatalysts with full-spectrum absorption through surface engineering is an effective approach to fully harnessing light energy in semiconductor materials.Herein,a novel stable Ti_(3)C_(2)T_(x)MXene/CdS heterojunction catalyst is obtained by in-situ epitaxial growth of two-dimensional(2D)CdS nanosheets on 2D MXene interface via a solvothermal method.The exceptional light absorption properties of MXene confer outstanding full-spectrum driven photocat-alytic hydrogen evolution capability upon the heterogeneous catalyst.The unique 2D/2D structure effectively mitigated the recombination of photogenerated carriers,enhancing the photocatalytic performance of the catalyst.Moreover,the composite catalyst exhibits a significantly higher surface temperature of 80.4℃under visible light irradiation at an intensity of 0.1 W/cm^(2),which is 1.84 times higher than that of CdS.Under irradiation of visible and near infrared light,the composite catalyst with photothermal ef-fect demonstrates a remarkable hydrogen evolution rate of 65.4 mmol g^(-1)h^(-1),which is 7.2 times higher than that of CdS catalyst.This study introduces a novel approach for constructing full-spectrum absorption catalysts and expands the application of the photothermal effect in photocatalytic hydrogen evolution research.
基金This project was partially supported by the Advanced Research Using High Intensity Laser Produced Photons and Particles(ADONIS)project(Grant No.CZ.02.1.01/0.0/0.0/16_019/0000789)the CAAS project(Grant No.CZ.02.1.01/0.0/0.0/16_019/0000778)+3 种基金both from the European Regional Development FundThe results of the LQ1606 project were partially obtained with the financial support from the Ministry of Education,Youth and Sports as part of targeted support from the National Programme of Sustainability IIThe authors acknowledge support from the National Natural Science Foundation of China(Grant Nos.11775033,11875241,11975215,11905204,12035002)the Laser Fusion Research Center Funds for Young Talents(Grant No.RCFPD3-2019-6).
文摘The physics of laser-plasma interaction is studied on the Shenguang III prototype laser facility under conditions relevant to inertial confinement fusion designs.A sub-millimeter-size underdense hot plasma is created by ionization of a low-density plastic foam by four high-energy(3.2 kJ)laser beams.An interaction beam is fired with a delay permitting evaluation of the excitation of parametric instabilities at different stages of plasma evolution.Multiple diagnostics are used for plasma characterization,scattered radiation,and accelerated electrons.The experimental results are analyzed with radiation hydrodynamic simulations that take account of foam ionization and homogenization.The measured level of stimulated Raman scattering is almost one order of magnitude larger than that measured in experiments with gasbags and hohlraums on the same installation,possibly because of a greater plasma density.Notable amplification is achieved in high-intensity speckles,indicating the importance of implementing laser temporal smoothing techniques with a large bandwidth for controlling laser propagation and absorption.
基金supported by the National Basic Research Program of China(973 Program)(No.2012CB619606)
文摘AI matrix composite containing high volume fraction silicon has been promising candidate for lightweight and low-thermal-expansion components. Whereas, optimization of its mechanical properties still is an open challenge. In this article, a flexile powder metallurgy processing was used to produce a fully dense AI-4.0Cu （wt%） alloy composite reinforced with 65 vol.% Si particles. In this composite, Si particles were homogenously distributed, and the particle size was refined to the range of 3-15 μm. Tensile and flexural strength of the composite were 282 and 455 MPa, respectively, about 100% and 50% higher than the best properties reported in literature. The measured fracture toughness of the composite was 4.90 MPa m1/2. The improved strength of 65%Si/AI was attributed to the optimized particle characteristics and matrix properties. This investigation is expected to provide a primary understanding of the mechanical behaviors of Si/AI composites, and also promote the structural applications of this low-thermal-expansion material.
基金This research was supported by the National Natural Science Foundation of China,Grant No.11775251the strategic leading science and technology program of Chinese Academy of Sciences(Grant No.XDA 15360100,XDA 15360102).
文摘Background Each GECAM satellite payload contains 25 gamma-ray detectors(GRDs),which can detect gamma-rays and particles and can roughly localize the Gamma-Ray Bursts(GRBs).GRD was designed using lanthanum bromide(LaBr3)crystal as the sensitive material with the rear end coupled with silicon photomultiplier(SiPM)array for readout.Purpose In aerospace engineering design of GRD,there are many key points to be studied.In this paper,we present the specific design scheme of GRD,the assembly and the performance test results of detectors.Methods Based on Monte Carlo simulation and experimental test results,the specific schematic design and assembling process of GRD were optimized.After being fully assembled,the GRDs were conducted performance tests by using radioactive source and also conducted random vibration tests.Result and conclusion The test results show that all satellite-borne GRDs have energy resolution<16%at 59.5 keV,meeting requirements of satellite in scientific performance.The random vibration test shows that GRD can maintain in a stable performance,which meets the requirement of spatial application.
基金This research was supported by the“Strategic Priority Research Program”of the Chinese Academy of Sciences,Grant No.XDA 15360102.
文摘Background The Gravitational wave highly energetic Electromagnetic Counterpart All-sky Monitor(GECAM)is dedicated to detecting gravitational wave gamma-ray bursts.It is capable of all-sky monitoring over and discovering gamma-ray bursts and new radiation phenomena.GECAM consists of two microsatellites,each equipped with 8 charged particle detectors(CPDs)and 25 gamma-ray detectors(GRDs).Purpose The CPD is used to measure charged particles in the space environment,monitor energy and flow intensity changes,and identify between gamma-ray bursts and space charged particle events in conjunction with GRD.Methods CPD uses plastic scintillator as the sensitive material for detection,silicon photomultiplier array as the optically readable device,and the inlaid Am-241 radioactive source as the onboard calibration means.Conclusion In this paper,we will present the working principle,physical design,functional implementation and preliminary performance test results of the CPD.As a result,the energy range of electron,gamma-ray detection efficiency and dead time are tested to be better than the indexes required through the ground calibration experiment.
基金supported by the National Key Fundamental Research&Development Project of China(No.G1999064903).
文摘A 2D full cell thermo-electric model of 160kA drained cell was set up using finiteelement code to calculate its freeze profile, then the drained cell model was modifiedaccording to the freeze profile computed and its heat balance was calculated. Comparedwith that of a 160kA conventional Hall-Heroult cell (H-H cell), though the melts vol-ume of the drained cell reduced greatly, the whole heat loss from it didn't drop downapparently, and an analysis was presented in the paper. On the other hand, the anode-cathode distance (ACD) of a drained cell was much less than that of a H-H cell, sothe voltage drop on it and heat produced decreased too, steps should be taken to keepa workable heat balance on a drained cell.
基金supported by the Major Science and Technology Project of Changchun City,Jilin Province(No.20210301024GX)the National Natural Science Foundation of China(No.52175335)The authors also appreciate the help pro-vided by China FAW Foundry Co.,LTD and Germany ALUMINUM RHEINFELDEN Group.
文摘The characterization of multiple iron-rich phases in high-pressure die-cast AlSi10MnMg alloy was studied.Attention was focused on the formation and fracture behavior of the primary iron-rich phase((P-IMC)_(I))formed in the shot sleeve and plate-shaped eutectic iron-rich phase in high-pressure die cast(HPDC)AlSi10MnMg alloy.Results show that multiple types of iron-rich phases with various morphologies,in-cluding primary iron-rich phases(polyhedral(P-IMC)_(I) and(P-IMC)_(II))and eutectic iron-rich phases(plate-shaped,net shape,and fish-bone shape),were found in HPDC AlSi10MnMg.Coarse(P-IMC)_(I) formed in the shot sleeve were distributed in the interface between primaryα-Al and binary Al-Si eutectic.Small size(P-IMC)_(II) and various eutectic iron-rich phases formed in the die cavity and they were distributed in Al-Si binary eutectic.The primary iron-rich phases belonged to a simple cubic crystal structure with a lattice constant a=1.265 nm and they exhibited a lateral growth characteristic with a termination of{110}surface.βphase was surrounded byδphase and they coexisted in a plate-shaped iron-rich phase.High-density stacking fault inβphase andδ/βinterface provided an excellent nucleation site forδphase.From mechanical behavior,the stress concentration caused by eutectic iron-rich phases was far less than(P-IMC)_(I) and it would not cause crack initiation along the eutectic cluster boundary.In addition,(P-IMC)_(I) showed the worst deformation coordination with primaryα-Al while the plate-shaped eutectic iron-rich phase exhibited similar deformation characteristics with silicon particles.
基金The Major State Research and Development Program of China (No. 2021YFB3701100, No. SQ2020YFF0405156)the National Natural Science Foundation of China (No.52171097, No. 51971020)+2 种基金Beijing Laboratory of Metallic Materials and Processing for Modern Transportationthe Fundamental Research Funds for the Central Universities(No. FRF-IC-20–08)“Dingxinbeike” Project(G20200001105) for the international communication。
文摘Inferior absolute strength and dissolution properties are the main bottlenecks for the widespread application of dissolvable magnesium alloys in complex working environments for unconventional oil and gas resources.Here,a novel functional peak-aged Mg-9.5Gd-2.7Y-0.9Zn-0.8Cu-0.4Ni(wt.%) alloy for fracturing tools is reported,and it possesses an ultimate tensile strength of 457.6 MPa,ultimate compressive strength of 620.7 MPa and dissolution rate of ~43.7 mg·cm^(-2)·h^(-1) in 3 wt.% KCl solutions at 93℃.The excellent strength of the agedalloy is primarily attributed to the combination of grain refinement,long-period stacking ordered(LPSO) strengthening,and precipitation strengthening induced by stacking fault and β’ phase,among which the precipitation strengthening is dominant.Further investigations confirm that the corrosion is triggered from the micro-galvanic coupling between the Mg matrix and the cathodic lamellar and block LPSO phases.Strip-shaped corrosion pits along with LPSO phases are subsequently formed,significantly accelerating corrosion.The β’ precipitates can effectively improve the strength without compromising the dissolution rate because of their nanoscale size.This study provides an excellent material selection for dissolvable fracturing tools and presents a strategy by which a synergistic combination of strength and dissolution rate is achieved via peak-aging treatment.
基金This project is supported by National Natural Science Foundation of China(12173038)the strategic leading science and technology program(XDA 15360100,XDA 15360102)of the Chinese Academy of Sciences.
文摘Introduction The main physical objective of the GECAM satellite is to detect gamma-ray bursts,which is related to gravitational waves of double compact object mergers.The GECAM satellite also detects and investigates various bursts of high-energy celestial bodies.Purposes and methods In this study,we designed,developed and calibrated the payload and launched it into orbit with GECAM satellite.The payload consists of the gamma ray detector(GRD,for detecting 4 keV–4 MeV X/γray),the charged particle detector(CPD,for detecting 150 keV–5 MeV charged particle),and the electronic box(EBOX).The all-sky field coverage is achieved via two 229-degree large-area satellites positioned 180 degrees apart and are on opposite sides of the geo-center.Each satellite is equipped with 25 GRDs and 8 CPDs;thus,the satellite can identify charged particle bursts in space.Gamma-ray detectors adopt lanthanum bromide crystal technology combined with silicon photomultipliers.This is the first time that this technology was used massively in space detectors.Conclusions The GECAM satellite can quickly determine the direction of gamma-ray bursts(positioning)via indexing and fitting method,while the transmit variability,energy spectrum and direction of the gamma-ray bursts guide subsequent observations through the Beidou-3 RDSS in quasi-real time.It will play an important role in the study of high energy celestial bursts.
基金This research is supported by the Strategic Priority Research Program of Chinese Academy of Sciences,Grant No.XDA15360102.
文摘Background The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)satellite developed a SiPM-based gamma-ray detector to monitor the gravitational wave-related GRBs and guide subsequent observations in other wavelengths of EM.Purpose As all the available SiPM devices belong to commercial grade,quality assurance tests need to be performed in accordance with the aerospace specifcations.Methods In the SiPM application of GECAM,quality assurance experiments were conducted.The mechanism of the failure of SiPM devices was analyzed during the development process.Result Based on the quality assurance test results,the fnal pass rate of SiPM array was 95%.Based on the failure analysis,it was found that a piece of SiPM had a leakage channel after longtime operation due to device defects.Conclusion According to the accumulated experience,in the reliability test of SiPM,it is necessary to pay special attention to test the impedance of each pin of SiPM to ground and confrm that the power switch state of SiPM is controllable.
基金This research was supported by the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(QYZDBSSW-SLH012)the National Natural Science Foundation of China(11775251,11775252)the strategic leading science and technology program of Chinese Academy of Sciences(XDA 15360100,XDA 15360102).
文摘Purpose The discovery of gravitational waves and gamma-ray bursts heralds the era of multi-messenger astronomy.With the adoption of two small satellites to achieve the all-sky monitoring of gamma-ray bursts,the gravitational wave highenergy electromagnetic counterpart all-sky monitor(GECAM)possesses a quasi-real-time early warning ability and plays an important role in positioning the sources of gravitational waves and in subsequent observations.Each satellite of GECAM was fitted with 253-inch-diameter gamma-ray detectors(GRD),covering an energy range of 8–2 MeV.GRDs have adopted silicon photomultiplier tubes(SiPM)in lieu of photomultiplier tubes(PMT)to adapt to the dimensional limitations of micro-satellites.Methods A unique 3-inch circular SiPM array was designed.In this design,646×6 mm chips were arranged evenly in a circular manner with the seams filled with reflecting films,thus achieving satisfactory uniformity of light collection.The integrated pre-amplifier circuit on the back of the SiPM array adopted two-level grouping and summing;further,it achieved a satisfactory signal-to-noise ratio.Two high-gain and low-gain channels were adopted to achieve a large dynamic range,and two independent power supply units were used,where each unit can be closed separately,thus improving reliability.Results Performance studies show that this SiPM array meets the requirements of GECAM.Conclusion A 3-inch SiPM array have been developed that uses grouped summation,reflective films,a circular arrangement,two groups of independent power supplies,high-and low-gain signals,differential signal output technologies,etc.This solution can be used not only for GECAM,but also as a general solution for SiPM-based scintillation detectors.
基金The authors would like to thank all colleagues for helpful suggestions and comments.This study was supported by the National Natural Science Foundation of China(Grant No.11803039 and 12173038)the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences(Grant No.XDA 15360100 and XDA 15360102).
文摘Background The Gravitational Wave High-energy Electromagnetic Counterpart All-sky Monitor(GECAM)consists of 2 microsatellites,each of which contains 25 GRD(LaBr3)detectors and 8 CPD(plastic scintillator)detectors.Method silicon photomultiplier(SiPM)array is used to read each detector.The output signal of these detectors with SiPM array is very special and challenging to readout.In this study,a novel data acquisition(DAQ)algorithm for these detectors is designed and implemented,and the content of the output event packet is defined.Result and Conclusion The performances,including the event acquisition efficiency of this DAQ algorithm,are extensively verified through experimental tests.From the on-ground and in-flight tests,this algorithm has excellent performance despite the very limited resources and short development time of GECAM mission.
基金supported by the National Science and Technology Major Project(No.2017-Ⅶ-0012-0108)the Natural Science Foundation of China(No.51701157)。
文摘In order to improve the oxidation and wear resistance of blades tip of titanium alloys as well as the sealing performance of the gas turbine engine,a Ni/cBN abrasive coating was prepared on titanium alloys through composite electroplating.Oxidation,mechanical and tribological properties of the abrasive coating were investigated.Furthermore,the effect of the oxidation on the mechanical and tribological properties was also evaluated.Oxidation results revealed that the abrasive coating underwent slight oxidation within 700℃.Meanwhile,some intermetallic compounds,Ni3Ti,NiTi and NiTi2,were formed at the coating/substrate interface during oxidation.Due to the pinning effect of cBN particles and the different thermal expansion coefficients of the coating and substrate,the coating/substrate interface was cracked after oxidation at 700℃.Tensile results showed that the presence of coating reduced the strength of the alloy significantly at room temperature,while only marginal variations of the strength of the coated and uncoated specimens at elevated temperatures.Besides,the wear tests indicated that the coating had the excellent cutting ability and wear resistance,which can effectively protect the blades tip of titanium alloys.As the temperature increased,the wear resistance decreased due to the decrease in the mechanical properties of the Ni/cBN coating.
