The mechanical behavior and microstructural evolution of an Fe-30Mn-3Al-3Si twinninginduced plasticity(TWIP)steel processed using warm forging was investigated.It is found that steel processed via warm forging improve...The mechanical behavior and microstructural evolution of an Fe-30Mn-3Al-3Si twinninginduced plasticity(TWIP)steel processed using warm forging was investigated.It is found that steel processed via warm forging improves comprehensive mechanical properties compared to the TWIP steel processed via cold rolling,with a high tensile strength(R_(m))of 793 MPa,a yield strength(R_(P))of 682 MPa,an extremely large R_(P)/R_(m)ratio as high as 0.86 as well as an excellent elongation rate of 46.8%.The microstructure observation demonstrates that steel processed by warm forging consists of large and elongated grains together with fine,equiaxed grains.Complicated micro-defect configurations were also observed within the steel,including dense dislocation networks and a few coarse deformation twins.As the plastic deformation proceeds,the densities of dislocations and deformation twins significantly increase.Moreover,a great number of slip lines could be observed in the elongated grains.These findings reveal that a much more dramatic interaction between microstructural defect and dislocations glide takes place in the forging sample,wherein the fine and equiaxed grains propagated dislocations more rapidly,together with initial defect configurations,are responsible for enhanced strength properties.Meanwhile,larger,elongated grains with more prevalently activated deformation twins result in high plasticity.展开更多
This article reviews recent progresses in growth mechanism,synthesis,and applications of zinc oxide nano- materials(mainly focusing on one-dimensional(1D)nanomaterials).In the first part of this article,we briefly int...This article reviews recent progresses in growth mechanism,synthesis,and applications of zinc oxide nano- materials(mainly focusing on one-dimensional(1D)nanomaterials).In the first part of this article,we briefly introduce the importance,the synthesis methods and growth mechanisms,the properties and applications of ZnO 1D nanomaterials.In the second part of this article,the growth mechanisms of ZnO 1D nanomaterials will be discussed in detail in the framework of vapor-liquid-solid(VLS),vapor-solid(VS),and aqueous solution growth(ASG)approaches.Both qualitative and quantitative information will be provided to show how a controlled synthesis of ZnO 1D nanomaterials can be achieved.In the third part of this article,we present recent progresses in our group for the synthesis of ZnO 1D nanomaterials,and the results from other groups will only be mentioned briefly.Especially,experiment designing according to theories will be elaborated to demonstrate the concept of controlled synthesis.In the fourth part of this article,the properties and potential applications of ZnO 1D nanomaterials will be treated.Finally,a summary part will be presented in the fifth section.The future trend of research for ZnO 1D nanomaterials will be pointed out and key issues to be solved will be proposed.展开更多
Our recent research on the Mn-based antiperovskite functional materials AXMn 3(A:metal or semiconducting elements;X:C or N) is outlined.Antiperovskite carbides(e.g.,AlCMn 3) show large magnetocaloric effect comparable...Our recent research on the Mn-based antiperovskite functional materials AXMn 3(A:metal or semiconducting elements;X:C or N) is outlined.Antiperovskite carbides(e.g.,AlCMn 3) show large magnetocaloric effect comparable to those of typical magnetic refrigerant materials.Enhanced giant magnetoresistance up to 70% at 50 kOe(1 Oe = 79.5775 A.m-1) over a wide temperature span was obtained in Ga1-xZnxCMn3 and GaCMn3-xNix.In Cu0.3Sn0.5NMn3.2,negative thermal expansion(NTE) was achieved in a wide temperature region covering room temperature(α =-6.8 ppm/K,150 K-400 K).Neutron pair distribution function analysis suggests the Cu/Sn-Mn bond fluctuation is the driving force for the NTE in Cu1-xSnxNMn3.In CuN1-xCx Mn3 and CuNMn3-yCoy,the temperature coefficient of resistivity(TCR) decreases monotonically from positive to negative as Co or C content increases.TCR is extremely low when the composition approaches the critical points.For example,TCR is ～ 1.29 ppm/K between 240K and 320K in CuN0.95C0.05Mn3,which is one twentieth of that in the typical low-TCR materials(～ 25 ppm/K).By studying the critical scaling behavior and X deficiency effect,some clues of localized-electron magnetism have been found against the background of electronic itinerant magnetism.展开更多
Amorphous Al_(72)Ni_8Ti_8Zr_6Nb_3Y_3 powders were successfully fabricated by mechanical alloying. The microstructure, glass-forming ability, and crystallization behavior of amorphous Al_(72)Ni_8Ti_8Zr_6Nb_3Y_3 powders...Amorphous Al_(72)Ni_8Ti_8Zr_6Nb_3Y_3 powders were successfully fabricated by mechanical alloying. The microstructure, glass-forming ability, and crystallization behavior of amorphous Al_(72)Ni_8Ti_8Zr_6Nb_3Y_3 powders were investigated by X-ray diffraction(XRD), transmission electron microscopy(TEM), and differential scanning calorimetry(DSC). The isothermal crystallization kinetics was analyzed by the Johnson–Mehl–Avrami equation. In the results, the supercooled liquid region of the amorphous alloy is as high as 81 K, as determined by-non-isothermal DSC curves. The activation energy for crystallization is as high as 312.6 kJ ·mol1 obtained by Kissinger and Ozawa analyses. The values of Avrami exponent(n) imply that the crystallization is dominated by interface-controlled three-dimensional growth in the early stage and the end stage and by diffusion-controlled two- or three-dimensional growth in the middle stage. In addition, the amorphous Al_(72)Ni_8Ti_8Zr_6Nb_3Y_3 powders were sintered under 2 GPa at temperatures of 673 K and 723 K. The results show that the Vickers hardness of the compacted powders is as high as Hv 1215.展开更多
The need for reducing the wear in mechanical parts used in the industry makes self-lubricant films one of the sustainable solutions to achieve long-term protection under different environmental conditions.The purpose ...The need for reducing the wear in mechanical parts used in the industry makes self-lubricant films one of the sustainable solutions to achieve long-term protection under different environmental conditions.The purpose of this work is to study the influence of C additions on the tribological behavior of a magnetron-sputtered TiN film in air,water,and seawater.The results show that the addition of C into the TiN binary film induced a new amorphous phase,and the films exhibited a dual phase of fcc(face-centered cubic)-TiN and amorphous carbon.The antifriction and wear-resistance properties were enhanced in air and water by adding 19.1at%C.However,a further increase in the C concentration improved anti-frictional properties but also led to higher wear rates.Although the amorphous phase induced microbatteries and accelerated the corrosion of TiN phases in seawater,the negative abrasion state was detected for all Ti-C-N films due to the adhesion of the tribocorrosion debris on the wear track.展开更多
The total ionizing dose(TID) effect is a key cause for the degradation/failure of semiconductor device performance under energetic-particle irradiation. We developed a dynamic model of mobile particles and defects by ...The total ionizing dose(TID) effect is a key cause for the degradation/failure of semiconductor device performance under energetic-particle irradiation. We developed a dynamic model of mobile particles and defects by solving the rate equations and Poisson's equation simultaneously, to understand threshold voltage shifts induced by TID in silicon-based metal–oxide–semiconductor(MOS) devices. The calculated charged defect distribution and corresponding electric field under different TIDs are consistent with experiments. TID changes the electric field at the Si/SiO_(2) interface by inducing the accumulation of oxide charged defects nearby, thus shifting the threshold voltage accordingly. With increasing TID, the oxide charged defects increase to saturation, and the electric field increases following the universal 2/3 power law. Through analyzing the influence of TID on the interfacial electric field by different factors, we recommend that the radiation-hardened performance of devices can be improved by choosing a thin oxide layer with high permittivity and under high gate voltages.展开更多
Graphene hosts intriguing photocarrier dynamics such as negative transient terahertz(THz) photoconductivity, high electron temperature, benefiting from the unique linear Dirac dispersion. In this work, the pressure ef...Graphene hosts intriguing photocarrier dynamics such as negative transient terahertz(THz) photoconductivity, high electron temperature, benefiting from the unique linear Dirac dispersion. In this work, the pressure effects of photocarrier dynamics of graphene have been investigated using in situ time-resolved THz spectroscopy in combination with diamond anvil cell exceeding 9 GPa. We find that the negative THz conductivity maintains in our studied pressure range both for monolayer and bilayer graphene. In particular, the amplitude of THz photoconductivity in monolayer graphene manifests an extraordinary dropping with pressure, compared with that from the counterparts such as bulk silicon and bilayer graphene.Concomitantly, the time constant is reduced with increasing pressure, highlighting the pressure-induced hot carrier cooling.The pressure dependence of photocarrier dynamics in monolayer graphene is likely related with the enhancement of the interfacial coupling between diamond surface and sample, allowing for the activity of new electron–phonon scattering. Our work is expected to provide an impetus for the studies of high-pressure THz spectroscopy of two-dimensional materials.展开更多
Ta As,the first experimentally discovered Weyl semimetal material,has attracted a lot of attention due to its high carrier mobility,high anisotropy,nonmagnetic properties and strong interaction with light.These make i...Ta As,the first experimentally discovered Weyl semimetal material,has attracted a lot of attention due to its high carrier mobility,high anisotropy,nonmagnetic properties and strong interaction with light.These make it an ideal candidate for the study of Weyl fermions and applications in quantum computation,thermoelectric devices,and photodetection.For further basic physics studies and potential applications,large-size and high-quality Ta As films are urgently needed.However,it is difficult to grow As-stoichiometry Ta As films due to the volatilization of As during the growth.To solve this problem,we attempted to grow Ta As films on different substrates using targets with different As stoichiometric ratios via pulsed laser deposition(PLD).In this work,we found that partial As ions of the Ga As substrate are likely to diffuse into the Ta As films during growth,which was preliminarily confirmed by structural characterization,surface topography and composition analysis.As a result,the As content in the Ta As film was improved and the Ta As phase was achieved.Our work presents an effective method for the fabrication of Ta As films using PLD,enabling possible use of the Weyl semimetal film for functional devices.展开更多
Recently,near-ambient superconductivity was claimed in nitrogen-doped lutetium hydride(LuH_(3-δ)N_(ε)).Unfortunately,all follow-up research still cannot find superconductivity signs in successfully synthesized lutet...Recently,near-ambient superconductivity was claimed in nitrogen-doped lutetium hydride(LuH_(3-δ)N_(ε)).Unfortunately,all follow-up research still cannot find superconductivity signs in successfully synthesized lutetium dihydride(LuH_(2)) and N-doped LuH_(2±x)N_(y).However,a similar intriguing observation was the pressure-induced color changes(from blue to pink and subsequent red).The physical understanding of its origin and the correlation between the color,crystal structure,and chemical composition of Lu–H–N is still lacking.In this work,we systematically investigated the optical properties of LuH_(2) and LuH_(3),and the effects of hydrogen vacancies and nitrogen doping using the first-principles calculations by considering both interband and intraband contributions.Our results demonstrate that the evolution of reflectivity peaks near blue and red light,which is driven by changes in the band gap and Fermi velocity of free electrons,resulting in the blue-to-red color change under pressure.In contrast,LuH_(3) exhibits gray and no color change up to 50 GPa.Furthermore,we investigated the effects of hydrogen vacancies and nitrogen doping on its optical properties.Hydrogen vacancies can significantly decrease the pressure of blue-to-red color change in LuH_(2) but do not have a noticeable effect on the color of LuH_(3).The N-doped LuH_(2) with the substitution of a hydrogen atom at the tetrahedral position maintains the color change when the N-doping concentration is low.As the doping level increases,this trend becomes less obvious,while other N-doped structures do not show a blue-to-red color change.Our results can clarify the origin of the experimental observed blue-to-red color change in lutetium hydride and also provide a further understanding of the potential N-doped lutetium dihydride.展开更多
The recent report of superconductivity in nitrogen-doped lutetium hydride(Lu-H-N)at 294 K and 1 GPa brought hope for long-sought-after ambient-condition superconductors.However,the failure of scientists worldwide to i...The recent report of superconductivity in nitrogen-doped lutetium hydride(Lu-H-N)at 294 K and 1 GPa brought hope for long-sought-after ambient-condition superconductors.However,the failure of scientists worldwide to independently reproduce these results has cast intense skepticism on this exciting claim.In this work,using a reliable experimental protocol,we synthesized Lu-H-N while minimizing extrinsic influences and reproduced the sudden change in resistance near room temperature.With quantitative comparison of the temperaturedependent resistance between Lu-H-N and the pure lutetium before reaction,we were able to clarify that the drastic resistance change is most likely caused by a metal-to-poor-conductor transition rather than by superconductivity.Herein,we also briefly discuss other issues recently raised in relation to the Lu-H-N system.展开更多
Transition metal oxides are regarded as promising candidates of anode for next-generation lithium-ion batteries(LIBs)due to their ultrahigh theoretical capacity and low cost,but are restricted by their low conductivit...Transition metal oxides are regarded as promising candidates of anode for next-generation lithium-ion batteries(LIBs)due to their ultrahigh theoretical capacity and low cost,but are restricted by their low conductivity and large volume expansion during Li^(+)intercalation.Herein,we designed and constructed a structurally integrated 3D carbon tube(3D-CT)grid film with Mn_(3)O_(4)nanoparticles(Mn_(3)O_(4)-NPs)and carbon nanotubes(CNTs)filled in the inner cavity of CTs(denoted as Mn_(3)O_(4)-NPs/CNTs@3D-CT)as high-performance free-standing anode for LIBs.The Mn_(3)O_(4)-NPs/CNTs@3D-CT grid with Mn_(3)O_(4)-NPs filled in the inner cavity of 3D-CT not only afford sufficient space to overcome the damage caused by the volume expansion of Mn_(3)O_(4)-NPs during charge and discharge processes,but also achieves highly efficient channels for the fast transport of both electrons and Li+during cycling,thus offering outstanding electrochemical performance(865 mAh g^(-1)at 1 A g^(-1)after 300 cycles)and excellent rate capability(418 mAh g^(-1)at 4 A g^(-1))based on the total mass of electrode.The unique 3D-CT framework structure would open up a new route to the highly stable,high-capacity,and excellent cycle and high-rate performance free-standing electrodes for highperformance Li-ion storage.展开更多
The recent report of pressure-induced structural transition and signature of superconductivity with T_(c)≈80 K above 14 GPa in La_(3)Ni_(2)O_(7)crystals has garnered considerable attention.To further elaborate this d...The recent report of pressure-induced structural transition and signature of superconductivity with T_(c)≈80 K above 14 GPa in La_(3)Ni_(2)O_(7)crystals has garnered considerable attention.To further elaborate this discovery,we carried out comprehensive resistance measurements on La_(3)Ni_(2)O_(7)crystals grown in an optical-image floating zone furnace under oxygen pressure(15 bar)using a diamond anvil cell(DAC)and cubic anvil cell(CAC),which employ a solid(KBr)and liquid(glycerol)pressure-transmitting medium,respectively.Sample 1 measured in the DAC exhibits a semiconducting-like behavior with large resistance at low pressures and gradually becomes metallic upon compression.At pressures P 13.7 GPa we observed the appearance of a resistance drop of as much as~50%around 70 K,which evolves into a kink-like anomaly at pressures above 40 GPa and shifts to lower temperatures gradually with increasing magnetic field.These observations are consistent with the recent report mentioned above.On the other hand,sample 2 measured in the CAC retains metallic behavior in the investigated pressure range up to 15 GPa.The hump-like anomaly in resistance around~130 K at ambient pressure disappears at P≥2 GPa.In the pressure range of 11–15 GPa we observed the gradual development of a shoulder-like anomaly in resistance at low temperatures,which evolves into a pronounced drop of resistance of 98%below 62 K at 15 GPa,reaching a temperature-independent resistance of 20μΩbelow 20 K.Similarly,this resistance anomaly can be progressively shifted to lower temperatures by applying external magnetic fields,resembling a typical superconducting transition.Measurements on sample 3 in the CAC reproduce the resistance drop at pressures above 10 GPa and realize zero resistance below 10 K at 15 GPa even though an unusual semiconducting-like behavior is retained in the normal state.Based on these results,we constructed a dome-shaped superconducting phase diagram and discuss some issues regarding the sample-dependent behaviors on pressure-induced hightemperature superconductivity in the La_(3)Ni_(2)O_(7)crystals.展开更多
Arson presents a challenging crime scene for fire investigators worldwide. Key to the investigation of suspected arson cases is the analysis of fire debris for the presence of accelerants or ignitable liquids. This st...Arson presents a challenging crime scene for fire investigators worldwide. Key to the investigation of suspected arson cases is the analysis of fire debris for the presence of accelerants or ignitable liquids. This study has investigated the application and method development of vapor phase mid-Infrared (mid-IR) spectroscopy using a field portable quantum cascade laser (QCL) based system for the detection and identification of accelerant residues such as gasoline, diesel, and ethanol in fire debris. A searchable spectral library of various ignitable fluids and fuel components measured in the vapor phase was constructed that allowed for real-time identification of accelerants present in samples using software developed in-house. Measurement of vapors collected from paper material that had been doused with an accelerant followed by controlled burning and then extinguished with water showed that positive identification could be achieved for gasoline, diesel, and ethanol. This vapor phase mid-IR QCL method is rapid, easy to use, and has the sensitivity and discrimination capability that make it well suited for non-destructive crime scene sample analysis. Sampling and measurement can be performed in minutes with this 7.5 kg instrument. This vibrational spectroscopic method required no time-consuming sample pretreatment or complicated solvent extraction procedure. The results of this initial feasibility study demonstrate that this portable fire debris analyzer would greatly benefit arson investigators performing analysis on-site.展开更多
For the past few years,germanium-based semiconductor spintronics has attracted considerable interest due to its potential for integration into mainstream semiconductor technology.The main challenges in the development...For the past few years,germanium-based semiconductor spintronics has attracted considerable interest due to its potential for integration into mainstream semiconductor technology.The main challenges in the development of modern semiconductor spintronics are the generation,detection,and manipulation of spin currents.Here,the transport characteristics of a spin current generated by spin pumping through a GeBi semiconductor barrier in Y_(3)Fe_(5)O_(12)/GeBi/Pt heterostructures were investigated systematically.The effective spin-mixing conductance and inverse spin Hall voltage to quantitatively describe the spin transport characteristics were extracted.The spin-injection efficiency in the Y_(3)Fe_(5)O_(12)/GeBi/Pt heterostructures is comparable to that of the Y_(3)Fe_(5)O_(12)/Pt bilayer,and the inverse spin Hall voltage exponential decays with the increase in the barrier thickness.Furthermore,the band gap of the GeBi layer was tuned by changing the Bi content.The spin-injection efficiency at the YIG/semiconductor interface and the spin transportation within the semiconductor barrier are related to the band gap of the GeBi layer.Our results may be used as guidelines for the fabrication of efficient spin transmission structures and may lead to further studies on the impacts of different kinds of barrier materials.展开更多
We report a systematic study on layered metal SrCu_(4-x)P_(2) single crystals via transport, magnetization, thermodynamic measurements and structural characterization. We find that the crystals show large linear magne...We report a systematic study on layered metal SrCu_(4-x)P_(2) single crystals via transport, magnetization, thermodynamic measurements and structural characterization. We find that the crystals show large linear magnetoresistance without any sign of saturation with a magnetic field up to 30T. We also observe a phase transition with significant anomalies in resistivity and heat capacity at T_(p)~140 K. Thermal expansion measurement reveals a subtle lattice parameter variation near Tp, i.e.,?L_(c)/L_(c)~0.062%. The structural characterization confines that there is no structure transition below and above T_(p). All these results suggest that the nonmagnetic transition of SrCu_(4-x)P_(2) could be associated with structural distortion.展开更多
W-(0.2,0.5,1.0)wt%ZrC alloys with a relative density above 97.5%were fabricated through the spark plasma sintering(SPS) method.The grain size of W-1.0wt%ZrC is about2.7 μm,smaller than that of pure W and W-(0.2,0.5)w...W-(0.2,0.5,1.0)wt%ZrC alloys with a relative density above 97.5%were fabricated through the spark plasma sintering(SPS) method.The grain size of W-1.0wt%ZrC is about2.7 μm,smaller than that of pure W and W-(0.2,0.5)wt%ZrC.The results indicated that the W-ZrC alloys exhibit higher hardness at room temperature,higher tensile strength at high temperature,and a lower ductile to brittle transition temperature(DBTT) than pure W.The tensile strength and total elongation of W-0.5wt%ZrC alloy at 700 ℃ is 535 MPa and 24.8%,which are respectively 59%and 114%higher than those of pure W(337 MPa,11.6%).The DBTT of W-(0.2,0.5,1.0)wt%ZrC materials is in the range of 500 ℃-600 ℃,which is about 100 ℃ lower than that of pure W.Based on microstructure analysis,the improved mechanical properties of the W-ZrC alloys were suggested to originate from the enhanced grain boundary cohesion by ZrC capturing the impurity oxygen in tungsten and nano-size ZrC dispersion strengthening.展开更多
A series of Al based alloys with low titanium contents (mass fraction) from 0.178% to 0.526% were directly produced in ordinary industrial electrolyzer. The electrolyzing results show that producing Al based alloys wi...A series of Al based alloys with low titanium contents (mass fraction) from 0.178% to 0.526% were directly produced in ordinary industrial electrolyzer. The electrolyzing results show that producing Al based alloys with titanium contents of less than 0.30% without great loss of electrolysis efficiency is possible. The quantitative analysis shows that this method has a great refining effect on transiting the coarse columnar grains in pure Al to equiaxed grains. The grain sizes decrease with the increase of titanium content and tend to a low limit at about 130 μm. During the solidification, the non equilibrium distribution of titanium leads to a great growth restricting effect and a constitutional under cooling zone in front of the growing liquid /solid interface.展开更多
Materials with the formula Yb 2-xAlxMo3O12(x =0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 0.9, 1.0, 1.1, 1.3, 1.5, and 1.8) were synthesized and their structures, phase transitions, and hygroscopicity investigated using X-ray powde...Materials with the formula Yb 2-xAlxMo3O12(x =0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 0.9, 1.0, 1.1, 1.3, 1.5, and 1.8) were synthesized and their structures, phase transitions, and hygroscopicity investigated using X-ray powder diffrac- tion, Raman spectroscopy, and thermal analysis. It is shown that Yb2-xAlxMo3O12 solid solutions crystallize in a single monoclinic phase for 1.7 ≤ x ≤ 2.0 and in a single orthorhombic phase for 0.0 ≤ x ≤ 0.4, and exhibit the characteristics of both monoclinic and orthorhombic structures outside these compositional ranges. The monoclinic to orthorhombic phase transition temperature of Al2Mo3O12 can be reduced by partial substitution of Al 3+ by Yb3+, and the Yb2-x AlxMo3O12 (0.0 < x ≤ 2.0) materials are hydrated at room temperature and contain two kinds of water species. One of these interacts strongly with and hinders the motions of the polyhedra, while the other does not. The partial substitution of Al3+ for Yb3+ in Yb2Mo3O12 decreases its hygroscopicity, and the linear thermal expansion co- efficients after complete removal of water species are measured to be 9.1×10 6 /K, 5.5×10 6 /K, 5.74×10 6 /K, and 9.5 × 10 6 /K for Yb1.8 Al0.2 (MoO4)3 , Yb1.6Al0.4 (MoO4 )3, Yb0.4 Al1.6 (MoO4)3 , and Yb 0.2Al1.8 (MoO4)3 , respectively.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.51701206 and 51671187)the Shanxi Natural Science Foundation(No.2019JQ-833)+2 种基金the Anhui Natural Science Foundation(1808085QE166)the Special Scientific Research Project of Shanxi Education Committee(No.19JQ0974)the Doctoral Research Initiation Project of Yan’an University(No.YDBD2018-21)。
文摘The mechanical behavior and microstructural evolution of an Fe-30Mn-3Al-3Si twinninginduced plasticity(TWIP)steel processed using warm forging was investigated.It is found that steel processed via warm forging improves comprehensive mechanical properties compared to the TWIP steel processed via cold rolling,with a high tensile strength(R_(m))of 793 MPa,a yield strength(R_(P))of 682 MPa,an extremely large R_(P)/R_(m)ratio as high as 0.86 as well as an excellent elongation rate of 46.8%.The microstructure observation demonstrates that steel processed by warm forging consists of large and elongated grains together with fine,equiaxed grains.Complicated micro-defect configurations were also observed within the steel,including dense dislocation networks and a few coarse deformation twins.As the plastic deformation proceeds,the densities of dislocations and deformation twins significantly increase.Moreover,a great number of slip lines could be observed in the elongated grains.These findings reveal that a much more dramatic interaction between microstructural defect and dislocations glide takes place in the forging sample,wherein the fine and equiaxed grains propagated dislocations more rapidly,together with initial defect configurations,are responsible for enhanced strength properties.Meanwhile,larger,elongated grains with more prevalently activated deformation twins result in high plasticity.
基金The authors acknowledge the support from the National Major Project of Fundamental Research:Nanomaterials and Nanostructures(Grant No.2005CB623603)the National Natural Science Foundation of China(Grant No.10304018,10574131)the Special Fund for President Scholarship,Chinese Academy of Sciences.We also thank Dr.Liang LI,Prof.Changhui YE,Dr.Yufeng HA0,Dr.Xinsheng PENG,Dr.Shuhui SUN,Dr.Changhao LIANG,Mr.Peng YAN,Prof.Guowen MENG,and Prof.Guanghui LI for their helps in the preparation of this manuscript.
基金the National Natural Science Foundation of China under grant No.10574131Anhui Provincial Key Laboratory Special Fundthe Presidential Scholarship Special Fund.
文摘This article reviews recent progresses in growth mechanism,synthesis,and applications of zinc oxide nano- materials(mainly focusing on one-dimensional(1D)nanomaterials).In the first part of this article,we briefly introduce the importance,the synthesis methods and growth mechanisms,the properties and applications of ZnO 1D nanomaterials.In the second part of this article,the growth mechanisms of ZnO 1D nanomaterials will be discussed in detail in the framework of vapor-liquid-solid(VLS),vapor-solid(VS),and aqueous solution growth(ASG)approaches.Both qualitative and quantitative information will be provided to show how a controlled synthesis of ZnO 1D nanomaterials can be achieved.In the third part of this article,we present recent progresses in our group for the synthesis of ZnO 1D nanomaterials,and the results from other groups will only be mentioned briefly.Especially,experiment designing according to theories will be elaborated to demonstrate the concept of controlled synthesis.In the fourth part of this article,the properties and potential applications of ZnO 1D nanomaterials will be treated.Finally,a summary part will be presented in the fifth section.The future trend of research for ZnO 1D nanomaterials will be pointed out and key issues to be solved will be proposed.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11174295,51001094,91222109,51171177,and 50701042)the National Key Basic Research of China (Grant No. 2011CBA00111)
文摘Our recent research on the Mn-based antiperovskite functional materials AXMn 3(A:metal or semiconducting elements;X:C or N) is outlined.Antiperovskite carbides(e.g.,AlCMn 3) show large magnetocaloric effect comparable to those of typical magnetic refrigerant materials.Enhanced giant magnetoresistance up to 70% at 50 kOe(1 Oe = 79.5775 A.m-1) over a wide temperature span was obtained in Ga1-xZnxCMn3 and GaCMn3-xNix.In Cu0.3Sn0.5NMn3.2,negative thermal expansion(NTE) was achieved in a wide temperature region covering room temperature(α =-6.8 ppm/K,150 K-400 K).Neutron pair distribution function analysis suggests the Cu/Sn-Mn bond fluctuation is the driving force for the NTE in Cu1-xSnxNMn3.In CuN1-xCx Mn3 and CuNMn3-yCoy,the temperature coefficient of resistivity(TCR) decreases monotonically from positive to negative as Co or C content increases.TCR is extremely low when the composition approaches the critical points.For example,TCR is ～ 1.29 ppm/K between 240K and 320K in CuN0.95C0.05Mn3,which is one twentieth of that in the typical low-TCR materials(～ 25 ppm/K).By studying the critical scaling behavior and X deficiency effect,some clues of localized-electron magnetism have been found against the background of electronic itinerant magnetism.
基金financially supported by the National Natural Science Foundation of China(No.51371167)
文摘Amorphous Al_(72)Ni_8Ti_8Zr_6Nb_3Y_3 powders were successfully fabricated by mechanical alloying. The microstructure, glass-forming ability, and crystallization behavior of amorphous Al_(72)Ni_8Ti_8Zr_6Nb_3Y_3 powders were investigated by X-ray diffraction(XRD), transmission electron microscopy(TEM), and differential scanning calorimetry(DSC). The isothermal crystallization kinetics was analyzed by the Johnson–Mehl–Avrami equation. In the results, the supercooled liquid region of the amorphous alloy is as high as 81 K, as determined by-non-isothermal DSC curves. The activation energy for crystallization is as high as 312.6 kJ ·mol1 obtained by Kissinger and Ozawa analyses. The values of Avrami exponent(n) imply that the crystallization is dominated by interface-controlled three-dimensional growth in the early stage and the end stage and by diffusion-controlled two- or three-dimensional growth in the middle stage. In addition, the amorphous Al_(72)Ni_8Ti_8Zr_6Nb_3Y_3 powders were sintered under 2 GPa at temperatures of 673 K and 723 K. The results show that the Vickers hardness of the compacted powders is as high as Hv 1215.
基金financially supported by the National Natural Science Foundation of China (Nos. 52171071, 52172090, 52071159, and 51801081)Portugal National Funds through FCT project (No. 2021.04115)+4 种基金FEDER National funds FCT under the project CEMMPRE–UIDB/ 00285/2020Outstanding University Young Teachers of “Qing Lan Project” of Jiangsu ProvinceExcellent Talents of “Shenlan Project” of Jiangsu University of Science and Technologyand China Merchants Marine Scientific Research and Innovation FundFilipe Fernandes acknowledges the funding received in the aim of the projects: MCTool21– ref. “POCI-01-0247-FEDER-045940”, CEMMPRE–ref. “UIDB/00285/2020”, and SMARTLUB–ref. “POCI-010145-FEDER-031807”
文摘The need for reducing the wear in mechanical parts used in the industry makes self-lubricant films one of the sustainable solutions to achieve long-term protection under different environmental conditions.The purpose of this work is to study the influence of C additions on the tribological behavior of a magnetron-sputtered TiN film in air,water,and seawater.The results show that the addition of C into the TiN binary film induced a new amorphous phase,and the films exhibited a dual phase of fcc(face-centered cubic)-TiN and amorphous carbon.The antifriction and wear-resistance properties were enhanced in air and water by adding 19.1at%C.However,a further increase in the C concentration improved anti-frictional properties but also led to higher wear rates.Although the amorphous phase induced microbatteries and accelerated the corrosion of TiN phases in seawater,the negative abrasion state was detected for all Ti-C-N films due to the adhesion of the tribocorrosion debris on the wear track.
基金Project supported by the Science Challenge Project of China (Grant No.TZ2018004)the National Natural Science Foundation of China (Grant Nos.11975018 and 11775254)+1 种基金the National MCF Energy R&D Program of China (Grant No.2018YEF0308100)the outstanding member of Youth Innovation Promotion Association CAS (Grant No.Y202087)。
文摘The total ionizing dose(TID) effect is a key cause for the degradation/failure of semiconductor device performance under energetic-particle irradiation. We developed a dynamic model of mobile particles and defects by solving the rate equations and Poisson's equation simultaneously, to understand threshold voltage shifts induced by TID in silicon-based metal–oxide–semiconductor(MOS) devices. The calculated charged defect distribution and corresponding electric field under different TIDs are consistent with experiments. TID changes the electric field at the Si/SiO_(2) interface by inducing the accumulation of oxide charged defects nearby, thus shifting the threshold voltage accordingly. With increasing TID, the oxide charged defects increase to saturation, and the electric field increases following the universal 2/3 power law. Through analyzing the influence of TID on the interfacial electric field by different factors, we recommend that the radiation-hardened performance of devices can be improved by choosing a thin oxide layer with high permittivity and under high gate voltages.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12174398,12004387,51727806,51672279,11874361,and 12204484)the Innovation Program of Chinese Academy of Sciences(Grant No.CXJJ-19B08)+2 种基金the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2021446)the HFIPS Director’s Fund of Chinese Academy of Sciences(Grant Nos.2021YZGH03 and YZJJKX202202)China Postdoctoral Science Foundation(Grant No.2021M703255)。
文摘Graphene hosts intriguing photocarrier dynamics such as negative transient terahertz(THz) photoconductivity, high electron temperature, benefiting from the unique linear Dirac dispersion. In this work, the pressure effects of photocarrier dynamics of graphene have been investigated using in situ time-resolved THz spectroscopy in combination with diamond anvil cell exceeding 9 GPa. We find that the negative THz conductivity maintains in our studied pressure range both for monolayer and bilayer graphene. In particular, the amplitude of THz photoconductivity in monolayer graphene manifests an extraordinary dropping with pressure, compared with that from the counterparts such as bulk silicon and bilayer graphene.Concomitantly, the time constant is reduced with increasing pressure, highlighting the pressure-induced hot carrier cooling.The pressure dependence of photocarrier dynamics in monolayer graphene is likely related with the enhancement of the interfacial coupling between diamond surface and sample, allowing for the activity of new electron–phonon scattering. Our work is expected to provide an impetus for the studies of high-pressure THz spectroscopy of two-dimensional materials.
基金Project supported by the National Key Research and Development Program of China(Grant No.2021YFA0718700)the National Natural Science Foundation of China(Grant No.12174347)+1 种基金the Synergetic Extreme Condition User Facility(SECUF)the Center for Materials Genome。
文摘Ta As,the first experimentally discovered Weyl semimetal material,has attracted a lot of attention due to its high carrier mobility,high anisotropy,nonmagnetic properties and strong interaction with light.These make it an ideal candidate for the study of Weyl fermions and applications in quantum computation,thermoelectric devices,and photodetection.For further basic physics studies and potential applications,large-size and high-quality Ta As films are urgently needed.However,it is difficult to grow As-stoichiometry Ta As films due to the volatilization of As during the growth.To solve this problem,we attempted to grow Ta As films on different substrates using targets with different As stoichiometric ratios via pulsed laser deposition(PLD).In this work,we found that partial As ions of the Ga As substrate are likely to diffuse into the Ta As films during growth,which was preliminarily confirmed by structural characterization,surface topography and composition analysis.As a result,the As content in the Ta As film was improved and the Ta As phase was achieved.Our work presents an effective method for the fabrication of Ta As films using PLD,enabling possible use of the Weyl semimetal film for functional devices.
基金supported by the National Key Research and Development Program of China(Grant Nos.2022YFA1403203 and 2021YFA1600200)the National Natural Science Foundation of China(Grant Nos.U2032215 and 12241405)。
文摘Recently,near-ambient superconductivity was claimed in nitrogen-doped lutetium hydride(LuH_(3-δ)N_(ε)).Unfortunately,all follow-up research still cannot find superconductivity signs in successfully synthesized lutetium dihydride(LuH_(2)) and N-doped LuH_(2±x)N_(y).However,a similar intriguing observation was the pressure-induced color changes(from blue to pink and subsequent red).The physical understanding of its origin and the correlation between the color,crystal structure,and chemical composition of Lu–H–N is still lacking.In this work,we systematically investigated the optical properties of LuH_(2) and LuH_(3),and the effects of hydrogen vacancies and nitrogen doping using the first-principles calculations by considering both interband and intraband contributions.Our results demonstrate that the evolution of reflectivity peaks near blue and red light,which is driven by changes in the band gap and Fermi velocity of free electrons,resulting in the blue-to-red color change under pressure.In contrast,LuH_(3) exhibits gray and no color change up to 50 GPa.Furthermore,we investigated the effects of hydrogen vacancies and nitrogen doping on its optical properties.Hydrogen vacancies can significantly decrease the pressure of blue-to-red color change in LuH_(2) but do not have a noticeable effect on the color of LuH_(3).The N-doped LuH_(2) with the substitution of a hydrogen atom at the tetrahedral position maintains the color change when the N-doping concentration is low.As the doping level increases,this trend becomes less obvious,while other N-doped structures do not show a blue-to-red color change.Our results can clarify the origin of the experimental observed blue-to-red color change in lutetium hydride and also provide a further understanding of the potential N-doped lutetium dihydride.
文摘The recent report of superconductivity in nitrogen-doped lutetium hydride(Lu-H-N)at 294 K and 1 GPa brought hope for long-sought-after ambient-condition superconductors.However,the failure of scientists worldwide to independently reproduce these results has cast intense skepticism on this exciting claim.In this work,using a reliable experimental protocol,we synthesized Lu-H-N while minimizing extrinsic influences and reproduced the sudden change in resistance near room temperature.With quantitative comparison of the temperaturedependent resistance between Lu-H-N and the pure lutetium before reaction,we were able to clarify that the drastic resistance change is most likely caused by a metal-to-poor-conductor transition rather than by superconductivity.Herein,we also briefly discuss other issues recently raised in relation to the Lu-H-N system.
基金supported by the Natural Science Foundation of China(91963202 and 52072372)the Key Research Program of Frontier Sciences(CAS,Grant,QYZDJ-SSW-SLH046)the CAS/SAFEA International Partnership Program for Creative Research Teams,and the Hefei Institutes of Physical Science,Chinese Academy of Sciences Director’s Fund(YZJ ZX202018)
文摘Transition metal oxides are regarded as promising candidates of anode for next-generation lithium-ion batteries(LIBs)due to their ultrahigh theoretical capacity and low cost,but are restricted by their low conductivity and large volume expansion during Li^(+)intercalation.Herein,we designed and constructed a structurally integrated 3D carbon tube(3D-CT)grid film with Mn_(3)O_(4)nanoparticles(Mn_(3)O_(4)-NPs)and carbon nanotubes(CNTs)filled in the inner cavity of CTs(denoted as Mn_(3)O_(4)-NPs/CNTs@3D-CT)as high-performance free-standing anode for LIBs.The Mn_(3)O_(4)-NPs/CNTs@3D-CT grid with Mn_(3)O_(4)-NPs filled in the inner cavity of 3D-CT not only afford sufficient space to overcome the damage caused by the volume expansion of Mn_(3)O_(4)-NPs during charge and discharge processes,but also achieves highly efficient channels for the fast transport of both electrons and Li+during cycling,thus offering outstanding electrochemical performance(865 mAh g^(-1)at 1 A g^(-1)after 300 cycles)and excellent rate capability(418 mAh g^(-1)at 4 A g^(-1))based on the total mass of electrode.The unique 3D-CT framework structure would open up a new route to the highly stable,high-capacity,and excellent cycle and high-rate performance free-standing electrodes for highperformance Li-ion storage.
基金supported by the Beijing Natural Science Foundation(Grant No.Z190008)the National Key Research and Development Program of China(Grant Nos.2018YFA0305700 and 2021YFA1400200)+6 种基金the National Natural Science Foundation of China(Grant Nos.12025408,11921004,11834016,and 11888101)supported by the National Natural Science Foundation of China(Grant No.12174454)the Strategic Priority Research Program of CAS(Grant No.XDB33000000)CAS Project for Young Scientists in Basic Research(Grant Nos.2022YSBR-047 and 2022YSBR-048)the Users with Excellence Program of Hefei Science Center CAS(Grant No.2021HSCUE008)Guangdong Basic and Applied Basic Research Funds(Grant No.2021B1515120015)Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices(Grant No.2022B1212010008)。
文摘The recent report of pressure-induced structural transition and signature of superconductivity with T_(c)≈80 K above 14 GPa in La_(3)Ni_(2)O_(7)crystals has garnered considerable attention.To further elaborate this discovery,we carried out comprehensive resistance measurements on La_(3)Ni_(2)O_(7)crystals grown in an optical-image floating zone furnace under oxygen pressure(15 bar)using a diamond anvil cell(DAC)and cubic anvil cell(CAC),which employ a solid(KBr)and liquid(glycerol)pressure-transmitting medium,respectively.Sample 1 measured in the DAC exhibits a semiconducting-like behavior with large resistance at low pressures and gradually becomes metallic upon compression.At pressures P 13.7 GPa we observed the appearance of a resistance drop of as much as~50%around 70 K,which evolves into a kink-like anomaly at pressures above 40 GPa and shifts to lower temperatures gradually with increasing magnetic field.These observations are consistent with the recent report mentioned above.On the other hand,sample 2 measured in the CAC retains metallic behavior in the investigated pressure range up to 15 GPa.The hump-like anomaly in resistance around~130 K at ambient pressure disappears at P≥2 GPa.In the pressure range of 11–15 GPa we observed the gradual development of a shoulder-like anomaly in resistance at low temperatures,which evolves into a pronounced drop of resistance of 98%below 62 K at 15 GPa,reaching a temperature-independent resistance of 20μΩbelow 20 K.Similarly,this resistance anomaly can be progressively shifted to lower temperatures by applying external magnetic fields,resembling a typical superconducting transition.Measurements on sample 3 in the CAC reproduce the resistance drop at pressures above 10 GPa and realize zero resistance below 10 K at 15 GPa even though an unusual semiconducting-like behavior is retained in the normal state.Based on these results,we constructed a dome-shaped superconducting phase diagram and discuss some issues regarding the sample-dependent behaviors on pressure-induced hightemperature superconductivity in the La_(3)Ni_(2)O_(7)crystals.
文摘Arson presents a challenging crime scene for fire investigators worldwide. Key to the investigation of suspected arson cases is the analysis of fire debris for the presence of accelerants or ignitable liquids. This study has investigated the application and method development of vapor phase mid-Infrared (mid-IR) spectroscopy using a field portable quantum cascade laser (QCL) based system for the detection and identification of accelerant residues such as gasoline, diesel, and ethanol in fire debris. A searchable spectral library of various ignitable fluids and fuel components measured in the vapor phase was constructed that allowed for real-time identification of accelerants present in samples using software developed in-house. Measurement of vapors collected from paper material that had been doused with an accelerant followed by controlled burning and then extinguished with water showed that positive identification could be achieved for gasoline, diesel, and ethanol. This vapor phase mid-IR QCL method is rapid, easy to use, and has the sensitivity and discrimination capability that make it well suited for non-destructive crime scene sample analysis. Sampling and measurement can be performed in minutes with this 7.5 kg instrument. This vibrational spectroscopic method required no time-consuming sample pretreatment or complicated solvent extraction procedure. The results of this initial feasibility study demonstrate that this portable fire debris analyzer would greatly benefit arson investigators performing analysis on-site.
基金Project supported by the National Key Research and Development Program of China(Grant No.2021YFA0718701)the China Postdoctoral Science Foundation(Grant No.2022M722888)the National Natural Science Foundation of China(Grant Nos.12174347 and 12004340).
文摘For the past few years,germanium-based semiconductor spintronics has attracted considerable interest due to its potential for integration into mainstream semiconductor technology.The main challenges in the development of modern semiconductor spintronics are the generation,detection,and manipulation of spin currents.Here,the transport characteristics of a spin current generated by spin pumping through a GeBi semiconductor barrier in Y_(3)Fe_(5)O_(12)/GeBi/Pt heterostructures were investigated systematically.The effective spin-mixing conductance and inverse spin Hall voltage to quantitatively describe the spin transport characteristics were extracted.The spin-injection efficiency in the Y_(3)Fe_(5)O_(12)/GeBi/Pt heterostructures is comparable to that of the Y_(3)Fe_(5)O_(12)/Pt bilayer,and the inverse spin Hall voltage exponential decays with the increase in the barrier thickness.Furthermore,the band gap of the GeBi layer was tuned by changing the Bi content.The spin-injection efficiency at the YIG/semiconductor interface and the spin transportation within the semiconductor barrier are related to the band gap of the GeBi layer.Our results may be used as guidelines for the fabrication of efficient spin transmission structures and may lead to further studies on the impacts of different kinds of barrier materials.
基金Project supported by the National Key Research and Development Program of China (Grant Nos.2023YFA1607403,2021YFA1600201,and 2022YFA1602603)the Natural Science Foundation of China (Grant Nos.U19A2093,U2032214,and U2032163)+5 种基金the Collaborative Innovation Program of Hefei Science Center,CAS (Grant No.2019HSC-CIP 001)the Youth Innovation Promotion Association of CAS (Grant No.2021117)the Natural Science Foundation of Anhui Province (No.1908085QA15)the HFIPS Director’s Fund (Grant No.YZJJQY202304)the CASHIPS Director’s Fund (Grant No.YZJJ2022QN36)supported by the High Magnetic Field Laboratory of Anhui Province。
文摘We report a systematic study on layered metal SrCu_(4-x)P_(2) single crystals via transport, magnetization, thermodynamic measurements and structural characterization. We find that the crystals show large linear magnetoresistance without any sign of saturation with a magnetic field up to 30T. We also observe a phase transition with significant anomalies in resistivity and heat capacity at T_(p)~140 K. Thermal expansion measurement reveals a subtle lattice parameter variation near Tp, i.e.,?L_(c)/L_(c)~0.062%. The structural characterization confines that there is no structure transition below and above T_(p). All these results suggest that the nonmagnetic transition of SrCu_(4-x)P_(2) could be associated with structural distortion.
基金supported by the Innovation Program of Chinese Academy of Sciences(No.KJCX2-YW-N35)the National Magnetic Confinement Fusion Science Program of China(No.2011GB108004)+1 种基金National Natural Science Foundation of China(Nos.51301164,11075177,11274305)Anhui Provincial Natural Science Foundation of China(No.1408085QE77)
文摘W-(0.2,0.5,1.0)wt%ZrC alloys with a relative density above 97.5%were fabricated through the spark plasma sintering(SPS) method.The grain size of W-1.0wt%ZrC is about2.7 μm,smaller than that of pure W and W-(0.2,0.5)wt%ZrC.The results indicated that the W-ZrC alloys exhibit higher hardness at room temperature,higher tensile strength at high temperature,and a lower ductile to brittle transition temperature(DBTT) than pure W.The tensile strength and total elongation of W-0.5wt%ZrC alloy at 700 ℃ is 535 MPa and 24.8%,which are respectively 59%and 114%higher than those of pure W(337 MPa,11.6%).The DBTT of W-(0.2,0.5,1.0)wt%ZrC materials is in the range of 500 ℃-600 ℃,which is about 100 ℃ lower than that of pure W.Based on microstructure analysis,the improved mechanical properties of the W-ZrC alloys were suggested to originate from the enhanced grain boundary cohesion by ZrC capturing the impurity oxygen in tungsten and nano-size ZrC dispersion strengthening.
文摘A series of Al based alloys with low titanium contents (mass fraction) from 0.178% to 0.526% were directly produced in ordinary industrial electrolyzer. The electrolyzing results show that producing Al based alloys with titanium contents of less than 0.30% without great loss of electrolysis efficiency is possible. The quantitative analysis shows that this method has a great refining effect on transiting the coarse columnar grains in pure Al to equiaxed grains. The grain sizes decrease with the increase of titanium content and tend to a low limit at about 130 μm. During the solidification, the non equilibrium distribution of titanium leads to a great growth restricting effect and a constitutional under cooling zone in front of the growing liquid /solid interface.
基金supported by the National Natural Science Foundation of China (Grant No. 10974183)
文摘Materials with the formula Yb 2-xAlxMo3O12(x =0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 0.9, 1.0, 1.1, 1.3, 1.5, and 1.8) were synthesized and their structures, phase transitions, and hygroscopicity investigated using X-ray powder diffrac- tion, Raman spectroscopy, and thermal analysis. It is shown that Yb2-xAlxMo3O12 solid solutions crystallize in a single monoclinic phase for 1.7 ≤ x ≤ 2.0 and in a single orthorhombic phase for 0.0 ≤ x ≤ 0.4, and exhibit the characteristics of both monoclinic and orthorhombic structures outside these compositional ranges. The monoclinic to orthorhombic phase transition temperature of Al2Mo3O12 can be reduced by partial substitution of Al 3+ by Yb3+, and the Yb2-x AlxMo3O12 (0.0 < x ≤ 2.0) materials are hydrated at room temperature and contain two kinds of water species. One of these interacts strongly with and hinders the motions of the polyhedra, while the other does not. The partial substitution of Al3+ for Yb3+ in Yb2Mo3O12 decreases its hygroscopicity, and the linear thermal expansion co- efficients after complete removal of water species are measured to be 9.1×10 6 /K, 5.5×10 6 /K, 5.74×10 6 /K, and 9.5 × 10 6 /K for Yb1.8 Al0.2 (MoO4)3 , Yb1.6Al0.4 (MoO4 )3, Yb0.4 Al1.6 (MoO4)3 , and Yb 0.2Al1.8 (MoO4)3 , respectively.
基金Supported by the National Natural Science Foundation of China under Grant No 51301150the Special Program of Science and Technology New Star of Shaanxi Province under Grant No 2013KJXX-11the High-level University Construction Special Program of Shaanxi Province under Grant No Physics-2012SXTS05
