In order to increase the application area of nanofibers,electrospun nanofiber yarns have drawn attention of many researchers around the globe.Once the production method of nanofiber yarn is mature enough to be univers...In order to increase the application area of nanofibers,electrospun nanofiber yarns have drawn attention of many researchers around the globe.Once the production method of nanofiber yarn is mature enough to be universally accepted,many new gates of applications will open to the world.In this review,different electrospinning techniques of electrospun nanofiber yarns are divided into needle electrospinning and needleless electrospinning.Considering yarn twist as an important mechanism,needle electrospinning technique is further categorized into mechanical,electrical and field flow twisting methods.Moreover,parameters influencing the mechanical properties of electrospun nanofiber yarns are investigated.Methods of improving mechanical properties of nanofiber yarns are addressed,including hot-water-bath treatment,addition of carbon nanotubes(CNTs)and introducing regulators.Finally,applications of electrospun nanofiber yarns in different fields of smart textile and bioengineering are summed-up.In summary,challenges encountered in the industrialization of nanofiber yarns and future prospects are anticipated.展开更多
Nanoparticles are extensively introduced to improve the mechanical,physical,and chemical properties of alloys.In the present study,the underlying nano-refinement mechanisms of face-centered cubic Zr(Fe,Cr)_(2)secondar...Nanoparticles are extensively introduced to improve the mechanical,physical,and chemical properties of alloys.In the present study,the underlying nano-refinement mechanisms of face-centered cubic Zr(Fe,Cr)_(2)secondary phase particles(SPPs)that precipitated in Zircaloy-4 alloy under high-temperature compression were investigated in detail by utilizing high-resolution transmission electron microscopy(HRTEM)and conventional TEM techniques.The frequently observed Zr(Fe,Cr)_(2)SPPs were incoherent with the matrix and exhibited brittle fracture behaviors without measurable plasticity.HRTEM observations revealed two mechanisms underlying the nano-refinement of incoherent micro-sized SPPs via localized shear fracture on{11¯2}SPP and nanoprecipitate-assisted bending fracture,respectively.The latter was,for the first time,found to occur when the movements of large SPPs were blocked by nanometer-sized SPP during alloy deformation.Accordingly,two force models were proposed to visualize their potential nano-refinement processes.The knowledge attained from this study sheds new light on the deformation behaviors of Zr(Fe,Cr)_(2)SPPs and their associated size refinement mechanisms under high-temperature compression,and is expected to greatly benefit the process optimization of zirconium alloys to achieve precipitate nano-refinement.展开更多
1.Introduction Zirconium(Zr)and its alloys show great applications in nuclear and chemical industry thanks to their appropriate mechanical properties,low thermal neutron absorption cross-section and excellent corrosio...1.Introduction Zirconium(Zr)and its alloys show great applications in nuclear and chemical industry thanks to their appropriate mechanical properties,low thermal neutron absorption cross-section and excellent corrosion resistance[1–3].Zr displays three different crystal structures on the temperature-pressure phase diagram:the hexagonal close-packed structure(HCP,α-Zr),the body centered cubic structure(BCC,β-Zr)and the simple hexagonal structure(ω-Zr).展开更多
So far,only two orientation relationships(OR)between hexagonal close-packed(HCP)(αphase)and facecentered cubic(FCC)structures in zirconium and titanium alloys have been reported.Here a new type FCC phase(named γ pha...So far,only two orientation relationships(OR)between hexagonal close-packed(HCP)(αphase)and facecentered cubic(FCC)structures in zirconium and titanium alloys have been reported.Here a new type FCC phase(named γ phase)with OR:<11■0>_(α)‖<100>_(γ) and{0001}_(α)‖{002}_(γ) was observed for the first time in annealed pure zirconium by means of transmission electron microscopy(TEM)technique.The α→γ phase transformation can be accomplished via expansion along[1■00]direction and slip of Shockley partial dislocation with 1/3[1■00]on(0001)basal planes.展开更多
基金Priority Academic Program Development of Jiangsu Higher Education Institutions,China(No.11372205)。
文摘In order to increase the application area of nanofibers,electrospun nanofiber yarns have drawn attention of many researchers around the globe.Once the production method of nanofiber yarn is mature enough to be universally accepted,many new gates of applications will open to the world.In this review,different electrospinning techniques of electrospun nanofiber yarns are divided into needle electrospinning and needleless electrospinning.Considering yarn twist as an important mechanism,needle electrospinning technique is further categorized into mechanical,electrical and field flow twisting methods.Moreover,parameters influencing the mechanical properties of electrospun nanofiber yarns are investigated.Methods of improving mechanical properties of nanofiber yarns are addressed,including hot-water-bath treatment,addition of carbon nanotubes(CNTs)and introducing regulators.Finally,applications of electrospun nanofiber yarns in different fields of smart textile and bioengineering are summed-up.In summary,challenges encountered in the industrialization of nanofiber yarns and future prospects are anticipated.
文摘Nanoparticles are extensively introduced to improve the mechanical,physical,and chemical properties of alloys.In the present study,the underlying nano-refinement mechanisms of face-centered cubic Zr(Fe,Cr)_(2)secondary phase particles(SPPs)that precipitated in Zircaloy-4 alloy under high-temperature compression were investigated in detail by utilizing high-resolution transmission electron microscopy(HRTEM)and conventional TEM techniques.The frequently observed Zr(Fe,Cr)_(2)SPPs were incoherent with the matrix and exhibited brittle fracture behaviors without measurable plasticity.HRTEM observations revealed two mechanisms underlying the nano-refinement of incoherent micro-sized SPPs via localized shear fracture on{11¯2}SPP and nanoprecipitate-assisted bending fracture,respectively.The latter was,for the first time,found to occur when the movements of large SPPs were blocked by nanometer-sized SPP during alloy deformation.Accordingly,two force models were proposed to visualize their potential nano-refinement processes.The knowledge attained from this study sheds new light on the deformation behaviors of Zr(Fe,Cr)_(2)SPPs and their associated size refinement mechanisms under high-temperature compression,and is expected to greatly benefit the process optimization of zirconium alloys to achieve precipitate nano-refinement.
文摘1.Introduction Zirconium(Zr)and its alloys show great applications in nuclear and chemical industry thanks to their appropriate mechanical properties,low thermal neutron absorption cross-section and excellent corrosion resistance[1–3].Zr displays three different crystal structures on the temperature-pressure phase diagram:the hexagonal close-packed structure(HCP,α-Zr),the body centered cubic structure(BCC,β-Zr)and the simple hexagonal structure(ω-Zr).
文摘So far,only two orientation relationships(OR)between hexagonal close-packed(HCP)(αphase)and facecentered cubic(FCC)structures in zirconium and titanium alloys have been reported.Here a new type FCC phase(named γ phase)with OR:<11■0>_(α)‖<100>_(γ) and{0001}_(α)‖{002}_(γ) was observed for the first time in annealed pure zirconium by means of transmission electron microscopy(TEM)technique.The α→γ phase transformation can be accomplished via expansion along[1■00]direction and slip of Shockley partial dislocation with 1/3[1■00]on(0001)basal planes.
