Considering both the effects of the interfacial normal velocity dependence of solute segregation and the local nonequilibrium solute diffusion,an extended free dendritic growth model was analyzed.Compared with the pre...Considering both the effects of the interfacial normal velocity dependence of solute segregation and the local nonequilibrium solute diffusion,an extended free dendritic growth model was analyzed.Compared with the predictions from the dendritic model with isosolutal interface assumption,the transition from solutal dendrite to thermal dendrite moves to higher undercoolings,i.e.,the region of undercoolings with solute controlled growth is extended.At high undercoolings,the transition from the mainly thermal-controlled growth to the purely thermal-controlled growth is not sharp as predicted by the isosolute model,but occurs in a range of undercooling,due to both the effects of the interfacial normal velocity dependence of solute segregation and the local nonequilibrium solute diffusion.Model test indicates that the present model can give a satisfactory agreement with the available experimental data for the Ni-0.7% B（mole fraction） alloy.展开更多
The crystallographic properties and R aman spectra of the title compound ZnCd(SCN) 4, which is a new nonlinear optica l crystal(NLO), are reported for the first time. This crystal is orthorhombic and its space group i...The crystallographic properties and R aman spectra of the title compound ZnCd(SCN) 4, which is a new nonlinear optica l crystal(NLO), are reported for the first time. This crystal is orthorhombic and its space group is I - 4 with unit cell parameters a =1.113 5(0.2) nm, c =0.437 60(1) nm. There are two formulas per unit cell. Raman spectra of zinc cadmium thiocyanatec (ZCTC) are given and the electron activities in the crystal are shown.展开更多
Nanocrystalline and amorphous Mg-Nd-Ni-Cu quaternary alloys with a composition of(Mg_(24)Ni_(10)Cu_2)_(100-x)Nd_x(x=0, 5, 10, 15, 20) were prepared by melt spinning technology and their structures as well as gaseous h...Nanocrystalline and amorphous Mg-Nd-Ni-Cu quaternary alloys with a composition of(Mg_(24)Ni_(10)Cu_2)_(100-x)Nd_x(x=0, 5, 10, 15, 20) were prepared by melt spinning technology and their structures as well as gaseous hydrogen storage characteristics were investigated. The XRD, TEM and SEM linked with EDS detections reveal that the as-spun Nd-free alloy holds an entire nanocrystalline structure but a nanocrystalline and amorphous structure for the as-spun Nd-added alloy, implying that the addition of Nd facilitates the glass forming in the Mg_2Ni-type alloy. Furthermore, the degree of amorphization of the as-spun Nd-added alloy and thermal stability of the amorphous structure clearly increase with the spinning rate rising. The melt spinning ameliorates the hydriding and dehydriding kinetics of the alloys dramatically. Specially, the rising of the spinning rate from 0(the as-cast was defined as the spinning rate of 0 m/s) to 40 m/s brings on the hydrogen absorption saturation ratio(R_5~a)(a ratio of the hydrogen absorption quantity in 5 min to the saturated hydrogen absorption capacity) increasing from 36.9% to 91.5% and the hydrogen desorption ratio(R_(1 0)~d)(a ratio of the hydrogen desorption quantity in 10 min to the saturated hydrogen absorption capacity) rising from 16.4% to 47.7% for the(x=10) alloy, respectively.展开更多
The a-Si∶H films with different thickness smaller than 1 μm were deposited by plasma enhanced chemical vapor deposition (PECVD) under the optimum deposition conditions. The effect of different thickness on film prop...The a-Si∶H films with different thickness smaller than 1 μm were deposited by plasma enhanced chemical vapor deposition (PECVD) under the optimum deposition conditions. The effect of different thickness on film properties is analyzed.The results show that,with the increase of the film thickness,the dark conductivity, photoconductivity and threshold voltage increase, the optical gap and peak ratio of TA to TO in the Raman spectra decrease, the refractive index keeps almost constant, and the optical absorption coefficient and current ratio of on/off state first maximize and then reduce.展开更多
Ferroelectric polymers are the mainstay of advanced flexible electronic devices.How to tailor the ferroelectric polymer films for various applications via simple processing approaches is challenging.Here we demonstrat...Ferroelectric polymers are the mainstay of advanced flexible electronic devices.How to tailor the ferroelectric polymer films for various applications via simple processing approaches is challenging.Here we demonstrate the tuning of ferroelectric responses can be achieved in polymer blends of poly(vinylidene fluoride-trifluoroethylene)(P(VDF-TrFE))and polymethyl methacrylate(PMMA)prepared via a simple two-step process.The proposed two-step process endows the polymer blends with a random distribution of P(VDF-TrFE)crystalline phase,hence decoupling the coherent ferroelectric domain interactions between continuous ordered crystalline phases that ubiquitously existed in common P(VDF-TrFE)film.The incorporation of the miscible non-crystalline PMMA chains with low-polarity results in reversal dipoles and a transition from ferroelectric to antiferroelectric-like behavior,overcoming the trade-off between the polarization and depolarization fields.In particular,resultant excellent mechanical and electrical properties of the polymer blend films give rise to remarkably improved breakdown strength and energy storage performance,surpassing P(VDF-TrFE)and commercial biaxial-oriented polypropylene films.This work provides a simple and effective strategy to tailor the ferroelectric response of polymeric materials with great potential for flexible electrical energy storage applications.展开更多
Herein,a novel photonic coordination polymer material was constructed by aggregation-induced emission luminogen(AIEgen)containing a tripyridyl moiety used as the linking ligand.It displayed a spontaneous direct centro...Herein,a novel photonic coordination polymer material was constructed by aggregation-induced emission luminogen(AIEgen)containing a tripyridyl moiety used as the linking ligand.It displayed a spontaneous direct centrosymmetric to noncentrosymmetric phase transition in a single crystal.The two crystals,before and after the phase transition,were both controllably synthesized and characterized by single-crystal X-ray diffraction.After being exposed to air,the centrosymmetric metastable phase(1-α)transitioned to a new stable phase with a noncentrosymmetric structure(1-β).Interestingly,the 1-βstructure exhibited a strong phasematching second-harmonic generation(SHG)response,about4.5 times higher than that of KH2PO4(KDP).In order to better understand the relationship between the structure and the nonlinear optical properties,the dipole moments were calculated and discussed.Remarkably,the noncentrosymmetric phase with high thermal stability for 1-βretained and improved the initial photoluminescent properties of the AIEgen ligand after the structural phase transition from 1-α,and simultaneously produced the excellent SHG property,which are beneficial for the design and construction of excellent optical materials.展开更多
基金Project(51101046)supported by the National Natural Science Foundation of ChinaProject(E201446)supported by the Natural Science Foundation of Heilongjiang Province of China+1 种基金Projects(2012M510985,2014T70361)supported by China Postdoctoral Science FoundationProject(LBH-Z12142)supported by the Heilongjiang Postdoctoral Fund,China
文摘Considering both the effects of the interfacial normal velocity dependence of solute segregation and the local nonequilibrium solute diffusion,an extended free dendritic growth model was analyzed.Compared with the predictions from the dendritic model with isosolutal interface assumption,the transition from solutal dendrite to thermal dendrite moves to higher undercoolings,i.e.,the region of undercoolings with solute controlled growth is extended.At high undercoolings,the transition from the mainly thermal-controlled growth to the purely thermal-controlled growth is not sharp as predicted by the isosolute model,but occurs in a range of undercooling,due to both the effects of the interfacial normal velocity dependence of solute segregation and the local nonequilibrium solute diffusion.Model test indicates that the present model can give a satisfactory agreement with the available experimental data for the Ni-0.7% B（mole fraction） alloy.
文摘The crystallographic properties and R aman spectra of the title compound ZnCd(SCN) 4, which is a new nonlinear optica l crystal(NLO), are reported for the first time. This crystal is orthorhombic and its space group is I - 4 with unit cell parameters a =1.113 5(0.2) nm, c =0.437 60(1) nm. There are two formulas per unit cell. Raman spectra of zinc cadmium thiocyanatec (ZCTC) are given and the electron activities in the crystal are shown.
基金Projects(51161015,51371094)supported by the National Natural Science Foundation of China
文摘Nanocrystalline and amorphous Mg-Nd-Ni-Cu quaternary alloys with a composition of(Mg_(24)Ni_(10)Cu_2)_(100-x)Nd_x(x=0, 5, 10, 15, 20) were prepared by melt spinning technology and their structures as well as gaseous hydrogen storage characteristics were investigated. The XRD, TEM and SEM linked with EDS detections reveal that the as-spun Nd-free alloy holds an entire nanocrystalline structure but a nanocrystalline and amorphous structure for the as-spun Nd-added alloy, implying that the addition of Nd facilitates the glass forming in the Mg_2Ni-type alloy. Furthermore, the degree of amorphization of the as-spun Nd-added alloy and thermal stability of the amorphous structure clearly increase with the spinning rate rising. The melt spinning ameliorates the hydriding and dehydriding kinetics of the alloys dramatically. Specially, the rising of the spinning rate from 0(the as-cast was defined as the spinning rate of 0 m/s) to 40 m/s brings on the hydrogen absorption saturation ratio(R_5~a)(a ratio of the hydrogen absorption quantity in 5 min to the saturated hydrogen absorption capacity) increasing from 36.9% to 91.5% and the hydrogen desorption ratio(R_(1 0)~d)(a ratio of the hydrogen desorption quantity in 10 min to the saturated hydrogen absorption capacity) rising from 16.4% to 47.7% for the(x=10) alloy, respectively.
文摘The a-Si∶H films with different thickness smaller than 1 μm were deposited by plasma enhanced chemical vapor deposition (PECVD) under the optimum deposition conditions. The effect of different thickness on film properties is analyzed.The results show that,with the increase of the film thickness,the dark conductivity, photoconductivity and threshold voltage increase, the optical gap and peak ratio of TA to TO in the Raman spectra decrease, the refractive index keeps almost constant, and the optical absorption coefficient and current ratio of on/off state first maximize and then reduce.
基金supported by the Basic Science Center Program of the National Natural Science Foundation of China(51788104)the National Natural Science Foundation of China(51802237,52072280,51872214 and 51872079)+2 种基金the Young Elite Scientists Sponsorship Program by CAST(2018QNRC001)the Open Fund of Hubei Key Laboratory of Ferro&Piezoelectric Materials and Devices(K201807)the Fundamental Research Funds for the Central Universities(193201002,183101005 and 182401004)。
文摘Ferroelectric polymers are the mainstay of advanced flexible electronic devices.How to tailor the ferroelectric polymer films for various applications via simple processing approaches is challenging.Here we demonstrate the tuning of ferroelectric responses can be achieved in polymer blends of poly(vinylidene fluoride-trifluoroethylene)(P(VDF-TrFE))and polymethyl methacrylate(PMMA)prepared via a simple two-step process.The proposed two-step process endows the polymer blends with a random distribution of P(VDF-TrFE)crystalline phase,hence decoupling the coherent ferroelectric domain interactions between continuous ordered crystalline phases that ubiquitously existed in common P(VDF-TrFE)film.The incorporation of the miscible non-crystalline PMMA chains with low-polarity results in reversal dipoles and a transition from ferroelectric to antiferroelectric-like behavior,overcoming the trade-off between the polarization and depolarization fields.In particular,resultant excellent mechanical and electrical properties of the polymer blend films give rise to remarkably improved breakdown strength and energy storage performance,surpassing P(VDF-TrFE)and commercial biaxial-oriented polypropylene films.This work provides a simple and effective strategy to tailor the ferroelectric response of polymeric materials with great potential for flexible electrical energy storage applications.
基金supported by the Natural Science Foundation of Xinjiang Uygur Autonomous Region of China(2019D01C059)the National Natural Science Foundation of China(21671003 and 21201005)+4 种基金the High Performance Computing Center of Henan Normal University and the 111 Project(D17007)Xinjiang Program of Cultivation of Young Innovative Technical Talents(2018Q061)the“2018 Tianchi Doctoral Plan”of Xinjiang Uygur Autonomous Region of Chinathe Doctoral Scientific Research Foundation of Anhui Jianzhu University(2017QD15)Xinjiang University.We thank LetPub(www.letpub.com)for its linguistic assistance during the preparation of this manuscript。
文摘Herein,a novel photonic coordination polymer material was constructed by aggregation-induced emission luminogen(AIEgen)containing a tripyridyl moiety used as the linking ligand.It displayed a spontaneous direct centrosymmetric to noncentrosymmetric phase transition in a single crystal.The two crystals,before and after the phase transition,were both controllably synthesized and characterized by single-crystal X-ray diffraction.After being exposed to air,the centrosymmetric metastable phase(1-α)transitioned to a new stable phase with a noncentrosymmetric structure(1-β).Interestingly,the 1-βstructure exhibited a strong phasematching second-harmonic generation(SHG)response,about4.5 times higher than that of KH2PO4(KDP).In order to better understand the relationship between the structure and the nonlinear optical properties,the dipole moments were calculated and discussed.Remarkably,the noncentrosymmetric phase with high thermal stability for 1-βretained and improved the initial photoluminescent properties of the AIEgen ligand after the structural phase transition from 1-α,and simultaneously produced the excellent SHG property,which are beneficial for the design and construction of excellent optical materials.
