Orthorhombic YFeO_3 thin film was prepared on La_(0.67)Sr_(0.33)MnO_3/LaAlO_3 substrate by a sol-gel spin-coating method. The structures of the YFeO_3/La_(0.67)Sr_(0.33)MnO_3/LaAlO_3(YFO/LSMO/LAO) sample were detected...Orthorhombic YFeO_3 thin film was prepared on La_(0.67)Sr_(0.33)MnO_3/LaAlO_3 substrate by a sol-gel spin-coating method. The structures of the YFeO_3/La_(0.67)Sr_(0.33)MnO_3/LaAlO_3(YFO/LSMO/LAO) sample were detected by x-ray diffraction pattern, Raman spectrometer, scanning electron microscopy, and atomic force microscope. The local ferroelectric polarization switching properties of the orthorhombic YFO film were confirmed by piezoresponse force microscopy(PFM) for the first time. The results show that the YFO film deposited on LSMO/LAO possesses orthorhombic structure,with ultra-fine crystal grains and flat surface. The leakage current of the YFO film is 8.39 × 10^(-4) A·cm^(-2) at 2 V,with its leakage mechanism found to be an ohmic behavior. PFM measurements indicate that the YFO film reveals weak ferroelectricity at room temperature and the local switching behavior of ferroelectric domains has been identified. By local poling experiment, polarization reversal in the orthorhombic YFO film at room temperature was further observed.展开更多
An Al-doped ZnO/p-Si heterojunction is fabricated by a laser molecular beam epitaxy technique. The abnormally high ideality factors （n 〉〉 2） of the prepared heterojunction are observed in the interim bias voltage ...An Al-doped ZnO/p-Si heterojunction is fabricated by a laser molecular beam epitaxy technique. The abnormally high ideality factors （n 〉〉 2） of the prepared heterojunction are observed in the interim bias voltage range. A theoretical model is proposed to understand the much higher ideality factor of the special heterojunction diode. The ZnO：Al film shows metal-like conductivity with the electrical resistivity about 6.56 × 10-4 Ω·cm at room temperature. The temperature dependence of the photovoltage indicates that the photovoltaic effect of the Al-doped ZnO based heterojunction can be changed by the intrinsic metal-semiconductor transition at 120 K.展开更多
Light–matter interaction plays an important role in the non-equilibrium physics, especially in strongly correlated electron systems with complex phases. Photoinduced effect can cause the variation in the physical pro...Light–matter interaction plays an important role in the non-equilibrium physics, especially in strongly correlated electron systems with complex phases. Photoinduced effect can cause the variation in the physical properties and produce some emergent phases. As a classical archetype, manganites have received much attention due to their colossal magnetoresistance（CMR） effect and the strong interaction of charge, spin, orbital, and lattice degrees of freedom. In this paper, we give an overview of photoinduced effect in manganites and their heterostructures. In particular, some materials, including ZnO, Si,BiFeO3（BFO）, titanate-based oxides, and 0.7 Pb（Mg（1/3） Nb（2/3））O3-0.3 PbTiO3（PMN-PT） have been integrated with manganites. Heterostructures composed of these materials display some exciting and intriguing properties. We do hope that this review offers a guiding idea and more meaningful physical phenomena will be discovered in active areas of solid state physics and materials science.展开更多
A heterostructure composed of a Bi2Fe4O9 film and an n−type Si substrate is fabricated.The characteristics of leakage current density versus electric field are investigated and the leakage current density is about 6&#...A heterostructure composed of a Bi2Fe4O9 film and an n−type Si substrate is fabricated.The characteristics of leakage current density versus electric field are investigated and the leakage current density is about 6×10^(−6) A/cm^(2) at an electric field of 200 kV/cm at 300 K.A strong photovoltaic effect is observed when the heterostructure is exposed to a laser pulse with a wavelength of 532 nm and a power of 6 mW/mm^(2).It is found that the peak photovoltages initially increase with decreasing temperature,followed by a decrease at T<210 K.These results reveal that the heterostructure is a promising candidate for photovoltaic devices that are compatible with Si integrated circuits.展开更多
Herein,a novel TiO_(2)/CN heterojunction material has been prepared by one-step bubble template-assisted calcination to enhance the hydrogen storage capability of LiAlH_(4).The TEM,XPS and UPS analysis confirm that a ...Herein,a novel TiO_(2)/CN heterojunction material has been prepared by one-step bubble template-assisted calcination to enhance the hydrogen storage capability of LiAlH_(4).The TEM,XPS and UPS analysis confirm that a heterostructure is formed between TiO_(2)and g-C3 N4 successfully.The experimental findings indi-cate that the TiO_(2)/CN significantly enhances the dehydrogenation performance of LiAlH_(4).For instance,the LiAlH_(4)-7 wt%TiO_(2)/CN starts to dehydrogenize at 76℃(94℃ less than pure LiAlH_(4))and releases 6.5 wt%H2 at 200℃.Meanwhile,LiAlH_(4)-7 wt%TiO_(2)/CN releases 4.9 wt%H2 at 120℃ within 50 min.The mech-anism analysis illustrates that AlTi3 N is formed in situ during ball-milling.And density functional theory(DFT)calculation results reveal that the AlTi3 N can weaken the Al-H bonds in LiAlH_(4)through interfacial charge transfer.Furthermore,the TiO_(2)/CN heterostructure creates an internal electric field that generates an electron-rich layer.As a result,the negative electron layer at one end of the TiO_(2)/CN heterojunction has an increased affinity for H,which enhances the dehydrogenation reaction of LiAlH_(4).Clearly,both the TiO_(2)/CN heterostructure and AlTi3 N contribute to the improvement of the dehydrogenation properties of LiAlH_(4).展开更多
The two-dimensional electron gas at SrTiO3-based heterointerfaces has received a great deal of attention in recent years owing to their potential for the exploration of emergent physics and the next generation of elec...The two-dimensional electron gas at SrTiO3-based heterointerfaces has received a great deal of attention in recent years owing to their potential for the exploration of emergent physics and the next generation of electronics. One of the most fascinating aspects in this system is that the light, as a powerful external perturbation, can modify its transport properties. Recent studies have reported that SrTiO3-based heterointerfaces exhibit the persistent photoconductivity and can be tuned by the surface and interface engineering. These researches not only reveal the intrinsic physical mechanisms in the photoresponsive process, but also highlight the ability to be used as a tool for novel all-oxide optical devices. This review mainly contraposes the studies of photoresponse at SrTiO3-based heterointerfaces.展开更多
Based on density functional theory calculations, the electronic and magnetic properties oi Co-duped SnO are investigated. It is found that the spin-polarized state, with a magnetic moment of about 1.0 μB per Co-dopan...Based on density functional theory calculations, the electronic and magnetic properties oi Co-duped SnO are investigated. It is found that the spin-polarized state, with a magnetic moment of about 1.0 μB per Co-dopant, is more favorable in energy than the non-spin-polarized state. Moreover, the origin of the ferromagnetism in Co-doped SnO is found to be the double exchange mechanism. Our results indicate that Co-doped SnO is a possible candidate of the u-type snintronics material.展开更多
In the previous study of longitudinal spin Seebeck effect（LSSE）, the thermal gradient was often generated by inserting the sample between the cool bath and the hot bath. For practical use, this method is too cumbers...In the previous study of longitudinal spin Seebeck effect（LSSE）, the thermal gradient was often generated by inserting the sample between the cool bath and the hot bath. For practical use, this method is too cumbersome to be easily integrated into modern electrical circuits. Since the laser can be easily focused into a small region, it will be more convenient and friendly to the integrated circuit. In this paper, we systematically investigate the LSSE and spin Hall magnetoresistance（SMR） of the Pt/Y_3 Fe_5 O_（12） heterostructure under focused laser-heating. We find that the extremely large voltage of inverse spin Hall effect（VISHE） can be obtained by reducing the diameter of laser or increasing the number of light spots.Meanwhile, even under the illumination of the ultraviolet light which will excite the electron from the valence band to the conduction band in yttrium iron garnet（YIG）, the magnitude of SMR is nearly constant. It indicates that the spin transport behavior of the adjacent Pt is independent of the electron configuration of YIG. The laser-heating method to generate LSSE will be very promising for modern integrated electronic circuits and will promote the application of spin caloritronics in practice.展开更多
The phase-field model for cell migration is used to study the effect of elasticity mismatch on the migration dynamics of multiple cells in a confluent monolayer, where one tagged cell is embedded by a number of normal...The phase-field model for cell migration is used to study the effect of elasticity mismatch on the migration dynamics of multiple cells in a confluent monolayer, where one tagged cell is embedded by a number of normal cells and both types of cells are supposed to have the same properties except elasticity. Our results show that a larger elasticity mismatch leads to a larger difference in shape change between the tagged cell and the normal cells. We find that the bursts of velocity always fall behind the peak of the perimeter, and the shape change of the tagged cell results in the accelerated motion of the tagged cell in the whole process. Moreover, the variation of the averaging cell perimeter ratio ˉLtag/ˉLnormalwith the increase of the elasticity ratio γtag/γnormal for different active velocities |a| is analyzed. We find thatˉLtag/ˉLnormaldecreases with the increase of γtag/γnormal, following a simple power law function. Our results highlight the important role played by the cell elasticity mismatch in cell deformation and migration.展开更多
1.Introduction Microstructures are at the centre of materials science and engineering and play an essential role in determining the in-service mechanical properties of metallic alloys[1–4].Extensive theoretical and e...1.Introduction Microstructures are at the centre of materials science and engineering and play an essential role in determining the in-service mechanical properties of metallic alloys[1–4].Extensive theoretical and experimental investigations have been undertaken to describe and determine solidification microstructures as a function of solidification conditions.The seaweed pattern is one of the most important classes of microstructural patterns[5–7].The characteristic of this pattern is that its extending tips—unlike the behaviour observed in needle-like dendrites—split repeatedly into two or more parts.展开更多
An oxygen-deficient SrTiO3/La0.67Sr0.33MnO3 heterojunction is fabricated on an SrTiO3 （001） substrate by a pulsed laser deposition method. The electrical characteristics of the heterojunction are studied systematica...An oxygen-deficient SrTiO3/La0.67Sr0.33MnO3 heterojunction is fabricated on an SrTiO3 （001） substrate by a pulsed laser deposition method. The electrical characteristics of the heterojunction are studied systematically in a temperature range from 80 K to 300 K. The transport mechanism follows I ∝ exp （eV/nkT） under small forward bias, while it becomes space charge limited and follows I ∝ Vm（T） with 1.49〈 m 〈1.99 under high bias. Such a heterojunction also exhibits magnetoresistance （MR） effect. The absolute value of negative MR monotonically increases with temperature decreasing and reaches 26.7% at 80 K under H=0.7 T. Various factors, such as strain and oxygen deficiency play dominant roles in the characteristics.展开更多
The purpose of the current study is to evaluate the ageing of poly(ethylene-co-propylene) fittings produced by several manufacturers. The fittings were aged for varying times as follows: 0, 2, 13, 23, 45, 106, 225 and...The purpose of the current study is to evaluate the ageing of poly(ethylene-co-propylene) fittings produced by several manufacturers. The fittings were aged for varying times as follows: 0, 2, 13, 23, 45, 106, 225 and 391 days at 100°C. In a previous paper, the oxidation induction time (OItime) and oxidation induction temperature (OItemp) were evaluated with respect to every single step of the ageing process [1]. Here, the Vickers microhardness and wide-angle X-ray line width were used for characterization of the oxidative stability of poly(ethylene-co-propylene) pipes. Both the Vickers microhardness and wide-angle X-ray line width as evaluated from a certain reflex of the diffractogram generally increase with ageing for most samples. The higher microhardness is most likely related to higher fragility of the pipes. The increase of the X-ray line width with ageing indirectly proves that reducing the crystallite size as well as increase of the crystallite defectiveness take place.展开更多
The anisotropic transport property was investigated in a phase separation La（0.67）Ca（0.33）MnO3（LCMO） film grown on（001）-oriented Nd GaO3（NGO） substrate. It was found that the resistivity along the b-axis is ...The anisotropic transport property was investigated in a phase separation La（0.67）Ca（0.33）MnO3（LCMO） film grown on（001）-oriented Nd GaO3（NGO） substrate. It was found that the resistivity along the b-axis is much higher than that along the a-axis. Two resistivity peaks were observed in the temperature dependent measurement along the b-axis, one located at 91 K and the other centered at 165 K. Moreover, we also studied the response of the resistivities along the two axes to various electric currents, magnetic fields, and light illuminations. The resistivities along the two axes are sensitive to the magnetic field. However, the electric current and light illumination can influence the resistivity along the b-axis obviously, but have little effect on the resistivity along the a-axis. Based on these results, we believe that an anisotropicstrain-controlled MnO6 octahedra shear-mode deformation may provide a mechanism of conduction filaments paths along the a-axis, which leads to the anisotropic transport property.展开更多
Numerical simulation based on phase field method is performed to describe solidification process of pure material in a free or forced flow. The evolution of the interface is showed, and the effects of mesh grid and fl...Numerical simulation based on phase field method is performed to describe solidification process of pure material in a free or forced flow. The evolution of the interface is showed, and the effects of mesh grid and flow velocity on succinonitrite shape are studied. These results indicate that crystal grows into an equiaxial dendrite in a free flow and into an asymmetrical dendritic in a forced flow. With increasing flow velocity, the upstream dendritic arm tip grows faster and the downstream arm grows slower. However, the evolution of the perpendicular tip has no significant change. In addition, mesh grid has no influence on dendritic growth shape when mesh grid is above 300×300.展开更多
Numerical simulation based on phase field method was performed to describe the solidification of silicon. The effect of anisotropy, undercooling and coupling parameter on dendrite growth shape was investigated. It is ...Numerical simulation based on phase field method was performed to describe the solidification of silicon. The effect of anisotropy, undercooling and coupling parameter on dendrite growth shape was investigated. It is indicated that the entire facet dendrite shapes are obtained by using regularized phase field model. Steady state tip velocity of dendrite drives to a fixed value when γ≤0.13. With further increasing the anisotropy value, steady state tip velocity decreases and the size is smaller. With the increase in the undercooling and coupling parameter, crystal grows from facet to facet dendrite. In addition, with increasing coupling parameter, the facet part of facet dendrite decreases gradually, which is in good agreement with Wulff theory.展开更多
Degenerate pattern is a seemingly disordered morphology but it exhibits the inherently ordered crystal connected with tip-splitting and limited stability which makes it difficult to observe in the metallic system. Her...Degenerate pattern is a seemingly disordered morphology but it exhibits the inherently ordered crystal connected with tip-splitting and limited stability which makes it difficult to observe in the metallic system. Here we employ(100)[011] orientated planar-front seeds using directional solidification and reveal the fundamental origins of the degenerate pattern growth in an Al-4.5 wt% Cu alloy. We find that the spacing of the tip-splitting(λ) in the degenerate of the alloys followed a power law,λ∝V^-0.5, and the frequency(f) of the splitting was related to the growth velocity(V) by f ∝V^1.5. The dimensionless growth direction(θ/θ0) increased monotonously and approached 0.6 with faster velocity, attributed to its anisotropy in the interface kinetics. Once growth velocity exceeded a threshold, two types of pattern transitions from degenerate to regular dendrites were proposed. One of them exhibited a random and chaotic mode and the other underwent a rotation in growth direction.展开更多
By using the Born-von Kfirmfin theory of lattice dynamics and the modified analytic embedded atom method, we reproduce the experimental results of the phonon dispersion in fcc metal Cu at zero pressure along three hig...By using the Born-von Kfirmfin theory of lattice dynamics and the modified analytic embedded atom method, we reproduce the experimental results of the phonon dispersion in fcc metal Cu at zero pressure along three high symmetry directions and four oft-symmetry directions, and then simulate the phonon dispersion curves of Cu at high pressures of 50, 100, and 150 GPa. The results show that the shapes of dispersion curves at high pressures are very similar to that at zero pressure. All the vibration frequencies of Cu in all vibration branches at high pressures are larger than the results at zero pressure, and increase correspondingly as pressure reaches 50, 100, and 150 GPa sequentially. Moreover, on the basis of phonon dispersion, we calculate the values of specific heat of Cu at different pressures. The prediction of thermodynamic quantities lays a significant foundation for guiding and judging experiments of thermodynamic properties of solids under high pressures.展开更多
Density change is ubiquitous in phase transformation, and it can induce melt convection which strongly influences the crystal growth. Here, an anisotropic lattice Boltzmann-phase-field method was extended to predict t...Density change is ubiquitous in phase transformation, and it can induce melt convection which strongly influences the crystal growth. Here, an anisotropic lattice Boltzmann-phase-field method was extended to predict the dendritic growth under the shrinkage or expansion melt convection by density change induced. A novel LB equation with an anisotropic coefficient was constructed to model the advancement of ordering parameter, coupling with the passive scalar LB equation for convective and diffusive heat transfer during phase transition. We studied dendritic growth and shape selection with melt convection induced by density change in crystal growth. Results show that the melt convection induced by density change affects strongly the dendritic growth. The shrinkage flow results in a higher tip velocity while the expansion flow leads to a slower one. Predicted Péclet number with respect to the relative density change was compared with an analytical solution. Moreover, the modified selection parameter has been verified by numerical simulations.展开更多
The solidification microstructures of Pb-45% Sn hypoeutectic and Pb-85%Sn hypereutectic alloys were studied in rotating magnetic field (RMF). A transition of primary phase from dendrite to spherical growth was caused ...The solidification microstructures of Pb-45% Sn hypoeutectic and Pb-85%Sn hypereutectic alloys were studied in rotating magnetic field (RMF). A transition of primary phase from dendrite to spherical growth was caused by the RMF, which simultaneously fractured and fined grains. The fracture and refinement increased first and then decreased with the increase in RMF intensity. When magnetic intensity exceeded a critical value, the size of the primary phase became bigger on the contrary. Therefore, there existed an optimum value of magnetic intensity in fracture and refinement of grain. Moreover, the rotating frequency determined the skin depth of magnetic field, and further affected the homogenization of temperature and solute. The rotating frequency and magnetic intensity were key factors affect- ing refinement and uniformity of solidification microstructures. The introduction of RMF not only changed the solidification thermodynamics, but also led to a reduction in Gibbs free energy associated with the formation of critical crystal nucleus and atom diffusion activation energy, thus enhancing the rate of nucleation.展开更多
Pattern selection during crystal growth is studied by using the anisotropic lattice Boltzmann-phase field model.In the model,the phase transition,melt flows,and heat transfer are coupled and mathematically described b...Pattern selection during crystal growth is studied by using the anisotropic lattice Boltzmann-phase field model.In the model,the phase transition,melt flows,and heat transfer are coupled and mathematically described by using the lattice Boltzmann(LB)scheme.The anisotropic streaming-relaxation operation fitting into the LB framework is implemented to model interface advancing with various preferred orientations.Crystal pattern evolutions are then numerically investigated in the conditions of with and without melt flows.It is found that melt flows can significantly influence heat transfer,crystal growth behavior,and phase distributions.The crystal morphological transition from dendrite,seaweed to cauliflower-like patterns occurs with the increase of undercoolings.The interface normal angles and curvature distributions are proposed to quantitatively characterize crystal patterns.The results demonstrate that the distributions are corresponding to crystal morphological features,and they can be therefore used to describe the evolution of crystal patterns in a quantitative way.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.61471301)Natural Science Basic Research Program of Shaanxi,China(Grant No.2017JQ5083)PhD Research Startup Foundation of Xi’an University of Science and Technology,China(Grant No.2017QDJ044)
文摘Orthorhombic YFeO_3 thin film was prepared on La_(0.67)Sr_(0.33)MnO_3/LaAlO_3 substrate by a sol-gel spin-coating method. The structures of the YFeO_3/La_(0.67)Sr_(0.33)MnO_3/LaAlO_3(YFO/LSMO/LAO) sample were detected by x-ray diffraction pattern, Raman spectrometer, scanning electron microscopy, and atomic force microscope. The local ferroelectric polarization switching properties of the orthorhombic YFO film were confirmed by piezoresponse force microscopy(PFM) for the first time. The results show that the YFO film deposited on LSMO/LAO possesses orthorhombic structure,with ultra-fine crystal grains and flat surface. The leakage current of the YFO film is 8.39 × 10^(-4) A·cm^(-2) at 2 V,with its leakage mechanism found to be an ohmic behavior. PFM measurements indicate that the YFO film reveals weak ferroelectricity at room temperature and the local switching behavior of ferroelectric domains has been identified. By local poling experiment, polarization reversal in the orthorhombic YFO film at room temperature was further observed.
基金Supported by the NPU Foundation for Fundamental Research under Grant Nos NPU-FFR-JC200821 and JC201048, the National Natural Science Foundation of China under Grant No 50702046, and the NWPU ＂Aoxiang Star＂ project.
文摘An Al-doped ZnO/p-Si heterojunction is fabricated by a laser molecular beam epitaxy technique. The abnormally high ideality factors （n 〉〉 2） of the prepared heterojunction are observed in the interim bias voltage range. A theoretical model is proposed to understand the much higher ideality factor of the special heterojunction diode. The ZnO：Al film shows metal-like conductivity with the electrical resistivity about 6.56 × 10-4 Ω·cm at room temperature. The temperature dependence of the photovoltage indicates that the photovoltaic effect of the Al-doped ZnO based heterojunction can be changed by the intrinsic metal-semiconductor transition at 120 K.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51572222,50702046,51172183,and 11604265)
文摘Light–matter interaction plays an important role in the non-equilibrium physics, especially in strongly correlated electron systems with complex phases. Photoinduced effect can cause the variation in the physical properties and produce some emergent phases. As a classical archetype, manganites have received much attention due to their colossal magnetoresistance（CMR） effect and the strong interaction of charge, spin, orbital, and lattice degrees of freedom. In this paper, we give an overview of photoinduced effect in manganites and their heterostructures. In particular, some materials, including ZnO, Si,BiFeO3（BFO）, titanate-based oxides, and 0.7 Pb（Mg（1/3） Nb（2/3））O3-0.3 PbTiO3（PMN-PT） have been integrated with manganites. Heterostructures composed of these materials display some exciting and intriguing properties. We do hope that this review offers a guiding idea and more meaningful physical phenomena will be discovered in active areas of solid state physics and materials science.
基金by the National Natural Science Foundation of China under Grant Nos 61078057 and 50702046,NPU Foundation for Fundamental Research under Grant Nos NPU-FFR-JC200821 and JC201048,and NWPU Aoxiang Star Project.
文摘A heterostructure composed of a Bi2Fe4O9 film and an n−type Si substrate is fabricated.The characteristics of leakage current density versus electric field are investigated and the leakage current density is about 6×10^(−6) A/cm^(2) at an electric field of 200 kV/cm at 300 K.A strong photovoltaic effect is observed when the heterostructure is exposed to a laser pulse with a wavelength of 532 nm and a power of 6 mW/mm^(2).It is found that the peak photovoltages initially increase with decreasing temperature,followed by a decrease at T<210 K.These results reveal that the heterostructure is a promising candidate for photovoltaic devices that are compatible with Si integrated circuits.
基金supported by National Natural Sci-ence Foundation of China(Nos.52271205,52371218,U20A20237 and 52101245)the Guangxi Key Research and Development Pro-gram(No.2021AB17045)+3 种基金the Science Research and Technology De-velopment project of Guilin(No.20210102-4)the Guangxi Key Laboratory of Sustainable Utilization of Plant Functional Substances(FPRU2022-4)Guangxi Key Laboratory of Information Laboratory Foundation(231006-Z)the Guangxi Bagui Scholar Foundation,the Guilin Lijiang Scholar Foundation,Guangxi Collaborative Innovation Centre of Structure and the Property for New Energy and Materi-als,Chinesisch-Deutsche Kooperationsgruppe(No.GZ1528).
文摘Herein,a novel TiO_(2)/CN heterojunction material has been prepared by one-step bubble template-assisted calcination to enhance the hydrogen storage capability of LiAlH_(4).The TEM,XPS and UPS analysis confirm that a heterostructure is formed between TiO_(2)and g-C3 N4 successfully.The experimental findings indi-cate that the TiO_(2)/CN significantly enhances the dehydrogenation performance of LiAlH_(4).For instance,the LiAlH_(4)-7 wt%TiO_(2)/CN starts to dehydrogenize at 76℃(94℃ less than pure LiAlH_(4))and releases 6.5 wt%H2 at 200℃.Meanwhile,LiAlH_(4)-7 wt%TiO_(2)/CN releases 4.9 wt%H2 at 120℃ within 50 min.The mech-anism analysis illustrates that AlTi3 N is formed in situ during ball-milling.And density functional theory(DFT)calculation results reveal that the AlTi3 N can weaken the Al-H bonds in LiAlH_(4)through interfacial charge transfer.Furthermore,the TiO_(2)/CN heterostructure creates an internal electric field that generates an electron-rich layer.As a result,the negative electron layer at one end of the TiO_(2)/CN heterojunction has an increased affinity for H,which enhances the dehydrogenation reaction of LiAlH_(4).Clearly,both the TiO_(2)/CN heterostructure and AlTi3 N contribute to the improvement of the dehydrogenation properties of LiAlH_(4).
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51572222 and 11604265)Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University,China(Grant No.CX201836)
文摘The two-dimensional electron gas at SrTiO3-based heterointerfaces has received a great deal of attention in recent years owing to their potential for the exploration of emergent physics and the next generation of electronics. One of the most fascinating aspects in this system is that the light, as a powerful external perturbation, can modify its transport properties. Recent studies have reported that SrTiO3-based heterointerfaces exhibit the persistent photoconductivity and can be tuned by the surface and interface engineering. These researches not only reveal the intrinsic physical mechanisms in the photoresponsive process, but also highlight the ability to be used as a tool for novel all-oxide optical devices. This review mainly contraposes the studies of photoresponse at SrTiO3-based heterointerfaces.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61078057 and 50702046)the Northwestern Polytechnical University "Aoxiang Star" Projectthe Northwestern Polytechnical University Foundation for Fundamental Research of China (Grant No. NPU-FFR-JC200821/JC201048)
文摘Based on density functional theory calculations, the electronic and magnetic properties oi Co-duped SnO are investigated. It is found that the spin-polarized state, with a magnetic moment of about 1.0 μB per Co-dopant, is more favorable in energy than the non-spin-polarized state. Moreover, the origin of the ferromagnetism in Co-doped SnO is found to be the double exchange mechanism. Our results indicate that Co-doped SnO is a possible candidate of the u-type snintronics material.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11604265,51471134,51572222,and 11704386)the Fundamental Research Funds for the Central Universities,China(Grant Nos.3102018zy044 and 3102017jc01001)
文摘In the previous study of longitudinal spin Seebeck effect（LSSE）, the thermal gradient was often generated by inserting the sample between the cool bath and the hot bath. For practical use, this method is too cumbersome to be easily integrated into modern electrical circuits. Since the laser can be easily focused into a small region, it will be more convenient and friendly to the integrated circuit. In this paper, we systematically investigate the LSSE and spin Hall magnetoresistance（SMR） of the Pt/Y_3 Fe_5 O_（12） heterostructure under focused laser-heating. We find that the extremely large voltage of inverse spin Hall effect（VISHE） can be obtained by reducing the diameter of laser or increasing the number of light spots.Meanwhile, even under the illumination of the ultraviolet light which will excite the electron from the valence band to the conduction band in yttrium iron garnet（YIG）, the magnitude of SMR is nearly constant. It indicates that the spin transport behavior of the adjacent Pt is independent of the electron configuration of YIG. The laser-heating method to generate LSSE will be very promising for modern integrated electronic circuits and will promote the application of spin caloritronics in practice.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51701160 and U1732129)the Fundamental Research Funds for the Central Universities,China(Grant No.3102018zy046)
文摘The phase-field model for cell migration is used to study the effect of elasticity mismatch on the migration dynamics of multiple cells in a confluent monolayer, where one tagged cell is embedded by a number of normal cells and both types of cells are supposed to have the same properties except elasticity. Our results show that a larger elasticity mismatch leads to a larger difference in shape change between the tagged cell and the normal cells. We find that the bursts of velocity always fall behind the peak of the perimeter, and the shape change of the tagged cell results in the accelerated motion of the tagged cell in the whole process. Moreover, the variation of the averaging cell perimeter ratio ˉLtag/ˉLnormalwith the increase of the elasticity ratio γtag/γnormal for different active velocities |a| is analyzed. We find thatˉLtag/ˉLnormaldecreases with the increase of γtag/γnormal, following a simple power law function. Our results highlight the important role played by the cell elasticity mismatch in cell deformation and migration.
基金supported by the Natural Science Foundation of Shandong Province(No.ZR202103010119)the National Natural Science Foundation of China(No.51974257)the Natural Science Foundation of Shaanxi Province(No.2020JM111).
文摘1.Introduction Microstructures are at the centre of materials science and engineering and play an essential role in determining the in-service mechanical properties of metallic alloys[1–4].Extensive theoretical and experimental investigations have been undertaken to describe and determine solidification microstructures as a function of solidification conditions.The seaweed pattern is one of the most important classes of microstructural patterns[5–7].The characteristic of this pattern is that its extending tips—unlike the behaviour observed in needle-like dendrites—split repeatedly into two or more parts.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61078057,51172183,and 51202195)the Natural Science Foundation of Shaanxi Province,China(Grant No.2012JQ8013)+1 种基金the Aviation Foundation of China(Grant No.2011ZF53065)the Foundation for Fundamental Research of Northwestern Polytechnical University(NPU),China(Grant Nos.JC201155,JC201271,and JC20120246)
文摘An oxygen-deficient SrTiO3/La0.67Sr0.33MnO3 heterojunction is fabricated on an SrTiO3 （001） substrate by a pulsed laser deposition method. The electrical characteristics of the heterojunction are studied systematically in a temperature range from 80 K to 300 K. The transport mechanism follows I ∝ exp （eV/nkT） under small forward bias, while it becomes space charge limited and follows I ∝ Vm（T） with 1.49〈 m 〈1.99 under high bias. Such a heterojunction also exhibits magnetoresistance （MR） effect. The absolute value of negative MR monotonically increases with temperature decreasing and reaches 26.7% at 80 K under H=0.7 T. Various factors, such as strain and oxygen deficiency play dominant roles in the characteristics.
文摘The purpose of the current study is to evaluate the ageing of poly(ethylene-co-propylene) fittings produced by several manufacturers. The fittings were aged for varying times as follows: 0, 2, 13, 23, 45, 106, 225 and 391 days at 100°C. In a previous paper, the oxidation induction time (OItime) and oxidation induction temperature (OItemp) were evaluated with respect to every single step of the ageing process [1]. Here, the Vickers microhardness and wide-angle X-ray line width were used for characterization of the oxidative stability of poly(ethylene-co-propylene) pipes. Both the Vickers microhardness and wide-angle X-ray line width as evaluated from a certain reflex of the diffractogram generally increase with ageing for most samples. The higher microhardness is most likely related to higher fragility of the pipes. The increase of the X-ray line width with ageing indirectly proves that reducing the crystallite size as well as increase of the crystallite defectiveness take place.
基金Project supported by the National Basic Research Program of China(Grant Nos.2011CB921801,2012CB921403,and 2013CB921701)the National Natural Science Foundation of China(Grant Nos.11074285,51372064,and 11134007)
文摘The anisotropic transport property was investigated in a phase separation La（0.67）Ca（0.33）MnO3（LCMO） film grown on（001）-oriented Nd GaO3（NGO） substrate. It was found that the resistivity along the b-axis is much higher than that along the a-axis. Two resistivity peaks were observed in the temperature dependent measurement along the b-axis, one located at 91 K and the other centered at 165 K. Moreover, we also studied the response of the resistivities along the two axes to various electric currents, magnetic fields, and light illuminations. The resistivities along the two axes are sensitive to the magnetic field. However, the electric current and light illumination can influence the resistivity along the b-axis obviously, but have little effect on the resistivity along the a-axis. Based on these results, we believe that an anisotropicstrain-controlled MnO6 octahedra shear-mode deformation may provide a mechanism of conduction filaments paths along the a-axis, which leads to the anisotropic transport property.
基金supported by the Major Program of the National Natural Science Foundation of China (Nos.50331040 and 60171034).
文摘Numerical simulation based on phase field method is performed to describe solidification process of pure material in a free or forced flow. The evolution of the interface is showed, and the effects of mesh grid and flow velocity on succinonitrite shape are studied. These results indicate that crystal grows into an equiaxial dendrite in a free flow and into an asymmetrical dendritic in a forced flow. With increasing flow velocity, the upstream dendritic arm tip grows faster and the downstream arm grows slower. However, the evolution of the perpendicular tip has no significant change. In addition, mesh grid has no influence on dendritic growth shape when mesh grid is above 300×300.
基金Projects(50331040 60171034) supported by the National Natural Science Foundation of China
文摘Numerical simulation based on phase field method was performed to describe the solidification of silicon. The effect of anisotropy, undercooling and coupling parameter on dendrite growth shape was investigated. It is indicated that the entire facet dendrite shapes are obtained by using regularized phase field model. Steady state tip velocity of dendrite drives to a fixed value when γ≤0.13. With further increasing the anisotropy value, steady state tip velocity decreases and the size is smaller. With the increase in the undercooling and coupling parameter, crystal grows from facet to facet dendrite. In addition, with increasing coupling parameter, the facet part of facet dendrite decreases gradually, which is in good agreement with Wulff theory.
基金financially supported by the National Natural Science Foundation of China (No. 51474174)Research Funds of the State Key Laboratory of Solidification Processing in NWPU (No. SKLSP201714)
文摘Degenerate pattern is a seemingly disordered morphology but it exhibits the inherently ordered crystal connected with tip-splitting and limited stability which makes it difficult to observe in the metallic system. Here we employ(100)[011] orientated planar-front seeds using directional solidification and reveal the fundamental origins of the degenerate pattern growth in an Al-4.5 wt% Cu alloy. We find that the spacing of the tip-splitting(λ) in the degenerate of the alloys followed a power law,λ∝V^-0.5, and the frequency(f) of the splitting was related to the growth velocity(V) by f ∝V^1.5. The dimensionless growth direction(θ/θ0) increased monotonously and approached 0.6 with faster velocity, attributed to its anisotropy in the interface kinetics. Once growth velocity exceeded a threshold, two types of pattern transitions from degenerate to regular dendrites were proposed. One of them exhibited a random and chaotic mode and the other underwent a rotation in growth direction.
基金supported by the National Natural Science Foundation of China (Grant Nos. 61078057 and 11204227)the Scientific Research Program of Education Department of Shaanxi Province, China (Grant No. 12JK0958)
文摘By using the Born-von Kfirmfin theory of lattice dynamics and the modified analytic embedded atom method, we reproduce the experimental results of the phonon dispersion in fcc metal Cu at zero pressure along three high symmetry directions and four oft-symmetry directions, and then simulate the phonon dispersion curves of Cu at high pressures of 50, 100, and 150 GPa. The results show that the shapes of dispersion curves at high pressures are very similar to that at zero pressure. All the vibration frequencies of Cu in all vibration branches at high pressures are larger than the results at zero pressure, and increase correspondingly as pressure reaches 50, 100, and 150 GPa sequentially. Moreover, on the basis of phonon dispersion, we calculate the values of specific heat of Cu at different pressures. The prediction of thermodynamic quantities lays a significant foundation for guiding and judging experiments of thermodynamic properties of solids under high pressures.
基金supported by the National Natural Science Foundation of China (Nos. 51701160, 51801186, and U1862117)Fundamental Research Funds for the Central Universities (No. 3102018zy046, and No. 2242019k1G003)the State Key Laboratory of Advanced Special Steel, Shanghai University, China (SKLASS2019-16)。
文摘Density change is ubiquitous in phase transformation, and it can induce melt convection which strongly influences the crystal growth. Here, an anisotropic lattice Boltzmann-phase-field method was extended to predict the dendritic growth under the shrinkage or expansion melt convection by density change induced. A novel LB equation with an anisotropic coefficient was constructed to model the advancement of ordering parameter, coupling with the passive scalar LB equation for convective and diffusive heat transfer during phase transition. We studied dendritic growth and shape selection with melt convection induced by density change in crystal growth. Results show that the melt convection induced by density change affects strongly the dendritic growth. The shrinkage flow results in a higher tip velocity while the expansion flow leads to a slower one. Predicted Péclet number with respect to the relative density change was compared with an analytical solution. Moreover, the modified selection parameter has been verified by numerical simulations.
基金the National Natural Science Foundation of China (Grant Nos. 50331040 and 60171034)
文摘The solidification microstructures of Pb-45% Sn hypoeutectic and Pb-85%Sn hypereutectic alloys were studied in rotating magnetic field (RMF). A transition of primary phase from dendrite to spherical growth was caused by the RMF, which simultaneously fractured and fined grains. The fracture and refinement increased first and then decreased with the increase in RMF intensity. When magnetic intensity exceeded a critical value, the size of the primary phase became bigger on the contrary. Therefore, there existed an optimum value of magnetic intensity in fracture and refinement of grain. Moreover, the rotating frequency determined the skin depth of magnetic field, and further affected the homogenization of temperature and solute. The rotating frequency and magnetic intensity were key factors affect- ing refinement and uniformity of solidification microstructures. The introduction of RMF not only changed the solidification thermodynamics, but also led to a reduction in Gibbs free energy associated with the formation of critical crystal nucleus and atom diffusion activation energy, thus enhancing the rate of nucleation.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51728601 and 51771118)the Fund of the State Key Laboratory of Solidification Processing in NPU(Grant No.SKLSP201901)the Fundamental Research Funds for the Central Universities,China(Grant No.2242019K1G003).
文摘Pattern selection during crystal growth is studied by using the anisotropic lattice Boltzmann-phase field model.In the model,the phase transition,melt flows,and heat transfer are coupled and mathematically described by using the lattice Boltzmann(LB)scheme.The anisotropic streaming-relaxation operation fitting into the LB framework is implemented to model interface advancing with various preferred orientations.Crystal pattern evolutions are then numerically investigated in the conditions of with and without melt flows.It is found that melt flows can significantly influence heat transfer,crystal growth behavior,and phase distributions.The crystal morphological transition from dendrite,seaweed to cauliflower-like patterns occurs with the increase of undercoolings.The interface normal angles and curvature distributions are proposed to quantitatively characterize crystal patterns.The results demonstrate that the distributions are corresponding to crystal morphological features,and they can be therefore used to describe the evolution of crystal patterns in a quantitative way.
