The single-phase high-entropy alloy film is difficult to meet severe friction conditions due to its low hardness and high friction coefficient.Nano-composite structure film is composed of at least two separated phases...The single-phase high-entropy alloy film is difficult to meet severe friction conditions due to its low hardness and high friction coefficient.Nano-composite structure film is composed of at least two separated phases,showing the properties of strength and toughness integration and excellent wear resistance.The design of nanocomposite structures can effectively improve the mechanical properties and tribological properties of high-entropy alloy films.In this study,the(CuNiTiNbCr)C_(x) nanocomposite high-entropy films(HEFs)integrated with high hardness,high toughness,and self-lubrication were synthesized by the double-target co-sputtering method.The effect of carbon content on microstructure,mechanical properties,and tribological properties of(CuNiTiNbCr)C_(x) films was studied.With the increase of carbon content in the HEFs,the carbon atoms preferentially react with Ti,Nb,and Cr to form a(TiNbCr)C ceramic-reinforced phase,and then the excess carbon atoms precipitate in the form of amorphous carbon(a-C)lubricating phase in the HEFs.The structure of the HEFs changes from an amorphous structure to a nanocomposite structure of amorphous(amorphous CuNiTiNbCr phase+a-C phase)/nanocrystalline(TiN-bCr)C phase.When the carbon content is about 21.2 at.%,the carbide phase in the film reaches saturation and the hardness and modulus of the films are highest,which are 18 GPa and 228 GPa,respectively.The HEFs with a carbon content of 44.0 at.%show the best toughness and tribological properties with a friction coefficient of 0.16 and a wear rate of 2.4×10^(-6) mm^(3)/(N m),which is mainly attributed to the excellent resistance to fatigue crack growth and the interfacial lubricating layer formed in the friction process.The nanocomposite(CuNiTiNbCr)C_(x) HEFs show very promising application prospect in the field of friction protection.展开更多
In contrast to ion beams produced by conventional accelerators,ion beams accelerated by ultrashort intense laser pulses have advantages of ultrashort bunch duration and ultrahigh density,which are achieved in compact ...In contrast to ion beams produced by conventional accelerators,ion beams accelerated by ultrashort intense laser pulses have advantages of ultrashort bunch duration and ultrahigh density,which are achieved in compact size.However,it is still challenging to simultaneously enhance their quality and yield for practical applications such as fast ion ignition of inertial confinement fusion.Compared with other mechanisms of laser-driven ion acceleration,the hole-boring radiation pressure acceleration has a special advantage in generating high-fluence ion beams suitable for the creation of high energy density state of matters.In this paper,we present a review on some theoretical and numerical studies of the hole-boring radiation pressure acceleration.First we discuss the typical field structure associated with this mechanism,its intrinsic feature of oscillations,and the underling physics.Then we will review some recently proposed schemes to enhance the beam quality and the efficiency in the hole-boring radiation pressure acceleration,such as matching laser intensity profile with target density profile,and using two-ion-species targets.Based on this,we propose an integrated scheme for efficient high-quality hole-boring radiation pressure acceleration,in which the longitudinal density profile of a composite target as well as the laser transverse intensity profile are tailored according to the matching condition.展开更多
Nanostructured silver was obtained by potentiostatic electrolysis.The effects of ionized surfactant(sodium dodecanesulphonate)and the substrate(Cu and Ti)on the morphology of depositions were investigated.It is found ...Nanostructured silver was obtained by potentiostatic electrolysis.The effects of ionized surfactant(sodium dodecanesulphonate)and the substrate(Cu and Ti)on the morphology of depositions were investigated.It is found that morphologies of silver nanostructures can be simply controlled via change of the substrate.Spherical Ag nanoparticles with narrow size distribution were obtained by electrodeposition in Ag NO3-SDS aqueous solution on copper substrate.In the case of titanium substrate,silver dendrite structures were obtained.Despite of different morphologies,XRD and TEM results showed that the as-prepared samples belong to face-centered cubic silver structure with good crystallinity.The formation mechanism of different silver nanostructures was discussed.展开更多
The assistance of alloying elements provides enormous opportunities for the discovery of high-performance face-centered cubic(FCC)medium-entropy alloys(MEAs).In this work,the influence of al-loying element Mo on the p...The assistance of alloying elements provides enormous opportunities for the discovery of high-performance face-centered cubic(FCC)medium-entropy alloys(MEAs).In this work,the influence of al-loying element Mo on the phase stability,stacking fault energy(SFE),deformation mechanisms,lattice distortion,and mechanical properties of(CoCrNi)100-x Mox(0≤x≤10)MEAs was synthetically explored with the first-principles calculations.It indicates that the FCC phase remains metastable at 0 K,and its stability degenerates with increasing Mo content.The monotonous decrease of SFE is revealed with the rise of Mo content,which promotes the activation of stacking faults,deformation twinning,or martensitic transformation.Raising Mo content also causes the aggravation of lattice distortion and thus triggers in-tense solid solution strengthening.Significantly,the essential criterion for the composition design of FCC(CoCrNi)100-x Mo MEAs with superior strength-ductility combination was established based on the syner-gistic effects between multiple deformation mechanisms and solid solution strengthening.According to the criterion,the optimal composition is predetermined as(CoCrNi)93 Mo7 MEA.The criterion is proved to be effective,and it can provide valuable inspiration for the development of alloying-element reinforced FCC multi-principal element alloys.展开更多
Environment friendly ferroelectric relaxor Ba(Zr_(0.2)Ti_(0.8))O_(3)thin fims with the addition of 2%Mn dopant were grown on(001)MgO substrates by pulsed laser deposition.Microstructure studies with X-ray di®ract...Environment friendly ferroelectric relaxor Ba(Zr_(0.2)Ti_(0.8))O_(3)thin fims with the addition of 2%Mn dopant were grown on(001)MgO substrates by pulsed laser deposition.Microstructure studies with X-ray di®raction and transmission electron microscopy reveal that the as-grown Ba(Zr_(0.2)Ti_(0.8))O_(3) thin films are c-axis oriented with an atomic sharp interface.The films have good single crystallinity and good epitaxial quality.The interface relationship was determined to be[100]Mn.BZT//[100]MgO and(001)Mn.BZT//(001)MgO.Nanoscale order/disorder relaxor structures were found with nano-columnar structures.The microwave dielectric measurements(15-18GHz)indicate that the¯lms have excellent dielectric properties with large dielectric constant value,high tunability,and low dielectric loss,promising the development of room temperature tunable microwave elements.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51975564)the Sichuan Science and Technology Project(Grant No.2021YFSY0050)+1 种基金the State Key Laboratory of Acoustics,Chinese Academy of Sciences(SKLA202214)the Fundamental Research Funds for the Central Universities(2682021CX103).
文摘The single-phase high-entropy alloy film is difficult to meet severe friction conditions due to its low hardness and high friction coefficient.Nano-composite structure film is composed of at least two separated phases,showing the properties of strength and toughness integration and excellent wear resistance.The design of nanocomposite structures can effectively improve the mechanical properties and tribological properties of high-entropy alloy films.In this study,the(CuNiTiNbCr)C_(x) nanocomposite high-entropy films(HEFs)integrated with high hardness,high toughness,and self-lubrication were synthesized by the double-target co-sputtering method.The effect of carbon content on microstructure,mechanical properties,and tribological properties of(CuNiTiNbCr)C_(x) films was studied.With the increase of carbon content in the HEFs,the carbon atoms preferentially react with Ti,Nb,and Cr to form a(TiNbCr)C ceramic-reinforced phase,and then the excess carbon atoms precipitate in the form of amorphous carbon(a-C)lubricating phase in the HEFs.The structure of the HEFs changes from an amorphous structure to a nanocomposite structure of amorphous(amorphous CuNiTiNbCr phase+a-C phase)/nanocrystalline(TiN-bCr)C phase.When the carbon content is about 21.2 at.%,the carbide phase in the film reaches saturation and the hardness and modulus of the films are highest,which are 18 GPa and 228 GPa,respectively.The HEFs with a carbon content of 44.0 at.%show the best toughness and tribological properties with a friction coefficient of 0.16 and a wear rate of 2.4×10^(-6) mm^(3)/(N m),which is mainly attributed to the excellent resistance to fatigue crack growth and the interfacial lubricating layer formed in the friction process.The nanocomposite(CuNiTiNbCr)C_(x) HEFs show very promising application prospect in the field of friction protection.
基金This work was supported in part by the National Basic Research Program of China(Grant No.2013CBA01504)the National Natural Science Foundation of China(Grant Nos.11675108,11421064,11405108 and 11374210).
文摘In contrast to ion beams produced by conventional accelerators,ion beams accelerated by ultrashort intense laser pulses have advantages of ultrashort bunch duration and ultrahigh density,which are achieved in compact size.However,it is still challenging to simultaneously enhance their quality and yield for practical applications such as fast ion ignition of inertial confinement fusion.Compared with other mechanisms of laser-driven ion acceleration,the hole-boring radiation pressure acceleration has a special advantage in generating high-fluence ion beams suitable for the creation of high energy density state of matters.In this paper,we present a review on some theoretical and numerical studies of the hole-boring radiation pressure acceleration.First we discuss the typical field structure associated with this mechanism,its intrinsic feature of oscillations,and the underling physics.Then we will review some recently proposed schemes to enhance the beam quality and the efficiency in the hole-boring radiation pressure acceleration,such as matching laser intensity profile with target density profile,and using two-ion-species targets.Based on this,we propose an integrated scheme for efficient high-quality hole-boring radiation pressure acceleration,in which the longitudinal density profile of a composite target as well as the laser transverse intensity profile are tailored according to the matching condition.
基金supported by the National Foundations of China-Australia Special Fund for Scientific and Technological Cooperation(grant No.20711120186)the Natural Science Foundations of China(grant No.20873184)+2 种基金the Natural Science Foundations of Guangdong Province(grant No.8151027501000095)the Science and Technology plan Projects of Guangdong Province(grant No.2008B010600040)the Instrumental Technique Research Foundation of Instrumental Analysis and Research Center,Sun Yat-sen University(grant No.2009006)
文摘Nanostructured silver was obtained by potentiostatic electrolysis.The effects of ionized surfactant(sodium dodecanesulphonate)and the substrate(Cu and Ti)on the morphology of depositions were investigated.It is found that morphologies of silver nanostructures can be simply controlled via change of the substrate.Spherical Ag nanoparticles with narrow size distribution were obtained by electrodeposition in Ag NO3-SDS aqueous solution on copper substrate.In the case of titanium substrate,silver dendrite structures were obtained.Despite of different morphologies,XRD and TEM results showed that the as-prepared samples belong to face-centered cubic silver structure with good crystallinity.The formation mechanism of different silver nanostructures was discussed.
基金the funding support for the work by the National Natural Science Foundation of China(NSFC)under Grant No.52071316the Youth Project of Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJQN202300755)+1 种基金the Natural Science Foundation of Chongqing(Grant No.cstc2021jcyj-msxmX0697)the Project of Science Foundation in Chongqing Jiaotong University(Grant No.F1210023).
文摘The assistance of alloying elements provides enormous opportunities for the discovery of high-performance face-centered cubic(FCC)medium-entropy alloys(MEAs).In this work,the influence of al-loying element Mo on the phase stability,stacking fault energy(SFE),deformation mechanisms,lattice distortion,and mechanical properties of(CoCrNi)100-x Mox(0≤x≤10)MEAs was synthetically explored with the first-principles calculations.It indicates that the FCC phase remains metastable at 0 K,and its stability degenerates with increasing Mo content.The monotonous decrease of SFE is revealed with the rise of Mo content,which promotes the activation of stacking faults,deformation twinning,or martensitic transformation.Raising Mo content also causes the aggravation of lattice distortion and thus triggers in-tense solid solution strengthening.Significantly,the essential criterion for the composition design of FCC(CoCrNi)100-x Mo MEAs with superior strength-ductility combination was established based on the syner-gistic effects between multiple deformation mechanisms and solid solution strengthening.According to the criterion,the optimal composition is predetermined as(CoCrNi)93 Mo7 MEA.The criterion is proved to be effective,and it can provide valuable inspiration for the development of alloying-element reinforced FCC multi-principal element alloys.
基金supported by the National Science Foundation under NSF-NIRT-0709293 and NSF-DMR-0934218the State of Texas through the ARP Program under 003656-0103-2007the Texas Center for Superconductivity at the University of Houston.
文摘Environment friendly ferroelectric relaxor Ba(Zr_(0.2)Ti_(0.8))O_(3)thin fims with the addition of 2%Mn dopant were grown on(001)MgO substrates by pulsed laser deposition.Microstructure studies with X-ray di®raction and transmission electron microscopy reveal that the as-grown Ba(Zr_(0.2)Ti_(0.8))O_(3) thin films are c-axis oriented with an atomic sharp interface.The films have good single crystallinity and good epitaxial quality.The interface relationship was determined to be[100]Mn.BZT//[100]MgO and(001)Mn.BZT//(001)MgO.Nanoscale order/disorder relaxor structures were found with nano-columnar structures.The microwave dielectric measurements(15-18GHz)indicate that the¯lms have excellent dielectric properties with large dielectric constant value,high tunability,and low dielectric loss,promising the development of room temperature tunable microwave elements.
