Thermal and Electrical Properties of Liquid Metal Gallium During Phase Transition

Liquid metal gallium has been widely used in numerous fields, from nuclear engineering, catalysts, and energy storage to electronics owing to its remarkable thermal and electrical properties along with low viscosity and nontoxicity. Compared with high-temperature liquid metals, room-temperature liquid metals, such as gallium(Ga), are emerging as promising alternatives for fabricating advanced energy storage devices, such as phase change materials, by harvesting the advantageous properties of their liquid state maintained without external energy input. However, the thermal and electrical properties of liquid metals at the phase transition are rather poorly studied, limiting their practical applications. In this study, we reported on the physical properties of the solid–liquid phase transition of Ga using a custom-designed, solid–liquid electrical and thermal measurement system. We observed that the electrical conductivity of Ga progressively decreases with an increase in temperature. However, the Seebeck coefficient of Ga increases from 0.2 to 2.1 μV/K, and thermal conductivity from 7.6 to 33 W/(K·m). These electrical and thermal properties of Ga at solid–liquid phase transition would be useful for practical applications.

Mechanism of Phase Transition from Liquid to Gas Under Dielectric Barrier Discharge Plasma

Liquid gasification phenomenon was observable in liquid-solid dielectric barrier discharge （DBD） experiments. Starting from classical thermodynamics, this study aimed at finding the reason of liquid gasification in the DBD experiments. Fluid statics and electrohydrodynamics were adopted to analyze the mechanism of phase transition from liquid to gas. The Sumoto effect was also employed to visually explain the change in the pressure of fluid due to the electric field. It was concluded from both theoretical analysis and experiment that the change in liquid pressure was a key factor causing liquid to gasify in DBD conditions.Furthermore, it was stressed that the liquid pressure was affected by many parameters including liquid permittivity, voltage, electric intensity, size of the discharge space and uniformity of the electric field distribution, etc. All of them affected DBD liquid gasification. The related results would provide useful theoretical evidence for multi-phase DBD applications.

Electrical Neutrality and Symmetry Restoring Phase Transitions at High Density in a Two-Flavor Nambu-Jona-Lasinio Model

A general research on chiral symmetry restoring phase transitions at zero temperature and finite chemical potentials under electrical neutrality condition has been conducted in a Nambu-Jona-Lasinio model to describe twoflavor normal quark matter. Depending on whether mo/A, the ratio of dynamical quark mass in vacuum and the 3D momentum cutoff in the loop integrals, is less or greater than 0.413, the phase transition will be of the second or first order. A complete phase diagram of u quark chemical potential versus mo is given. With the electrical neutrality constraint, the region where the second order phase transition happens will be wider than the one without electrical neutrality limitation. The results also show that, for the value ofmo/A from QCD phenomenology, the phase transition must be of the first order.

High Electrical Conductivity and Conspicuous Phase Transitions in Single Crystals of K-TCNQ

This paper is to report the temperature dependent electrical conductivity of single crystals of radical ion salt (RIS) potassium-TCNQ (K-tetracyanoquino- dimethane) in a wide range of temperatures from 30 to 500 K. This RIS is quasi-one-dimensional in nature. These single crystals of K-TCNQ are grown by different methods like electrochemical, solution growth and diffusion method. Activation energy is determined for the sample in different temperature regions and found different values. More than one semiconductor to metal phase transition is observed in the studied samples during electrical measurements below and above room temperature. All the features observed in the studied samples are analyzed in the framework of their molecular structure as well as under different effects like disorder, impurity, Coulomb interaction, charge density wave (CDW), scattering and 3-D effects etc.

Stability of the Liquid-Vapor Interface under the Combined Influence of Normal Vibrations and an Electric Field

The regime of horizontal subcooled film boiling is characterized by the formation of a thin layer of vapor coveringthe surface of a flat horizontal heater. Based on the equations of motion of a viscous incompressible fluid and theequation of heat transfer, the stability of such a vapor film is investigated. The influence of the modulation of thegravity field caused by vertical vibrations of the heater of finite frequency, as well as a constant electric fieldapplied normal to the surface of the heater, is taken into account. It is shown that in the case of a thick vaporfilm, the phase transition has a little effect on the thresholds for the occurrence of parametric instability in thesystem and its transformation into the most dangerous one. At the same time, the electric field contributes toan increase in these thresholds. It was found that the effect of vibrations on the stabilization of non-parametricinstability in the system is possible only in a narrow region of the parameter space where long-wave damped disturbances exist and consists of reducing the critical heat flux of stabilization. A vapor film stabilized in this waycan be destroyed due to the development of parametric instability. In contrast to the case of a thick vapor layer,the threshold for the onset of parametric instability for thin films largely depends on the value of subcooling in thesystem. In addition, this threshold decreases with increasing electric field strength. For a vapor film ten micronsthick, the instability threshold can be reduced by a factor of three or more by applying an electric field of aboutthree million volts per meter.

Study on theoretical model for electrical explosion resistivity of Al/Ni reactive multilayer foil

Al/Ni reactive multilayer foil(RMF)possesses excellent comprehensive properties as a promising substitute for traditional Cu bridge.A theoretical resistivity model of Al/Ni RMF was developed to guide the optimization of EFIs.Al/Ni RMF with different bilayer thicknesses and bridge dimensions were prepared by MEMS technology and electrical explosion tests were carried out.According to physical and chemical reactions in bridge,the electrical explosion process was divided into 5 stages:heating of condensed bridge,vaporization and diffusion of Al layers,intermetallic combination reaction,intrinsic explosion,ionization of metal gases,which are obviously shown in measured voltage curve.Effects of interface and grain boundary scattering on the resistivity of film metal were considered.Focusing on variations of substance and state,the resistivity was developed as a function of temperature at each stage.Electrical explosion curves were calculated by this model at different bilayer thicknesses,bridge dimensions and capacitor voltages,which showed an excellent agreement with experimental ones.

Electricity resonance-induced phase transition of water confined in nanochannels

The phase transition of water molecules in nanochannels under varying external electric fields is studied by molecular dynamics simulations.It is found that the phase transition of water molecules in nanochannels occurs by changing the frequency of the varying electric field.Water molecules maintain the ice phase when the frequency of the varying electric field is less than 16 THz or greater than 30 THz,and they completely melt when the frequency of the varying electric field is 24 THz.This phenomenon is attributed to the breaking of hydrogen bonds when the frequency of the varying electric field is close to their inherent resonant frequency.Moreover,the study demonstrates that the critical frequency varies with the confinement situation.The new mechanism of regulating the phase transition of water molecules in nanochannels revealed in this study provides a perspective for further understanding of the phase transition of water molecules in nanochannels,and has great application potential in preventing icing and deicing.

High-pressure investigations on the isostructural phase transition and metallization in realgar with diamond anvil cells

The high-pressure structural,vibrational and electrical properties for realgar were investigated by in-situ Raman scattering and electrical conductivity experiments combined with first-principle calculations up to~30.8 GPa.It was verified that realgar underwent an isostructural phase transition at~6.3 GPa and a metallization at a higher pressure of~23.5 GPa.The isostructural phase transition was well evidenced by the obvious variations of Raman peaks,electrical conductivity,crystal parameters and the As–S bond length.The phase transition of metallization was in closely associated with the closure of bandgap rather than caused by the structural phase transition.And furthermore,the metallic realgar exhibited a relatively low compressibility with the unit cell volume V_(0)=718.1.4Å^(3)and bulk modulus B_(0)=36.1 GPa.

Field-induced anisotropic magnetic phase transitions and tricritical phenomena in GdCr_(6)Ge_(6)

The interaction between complex magnetic structures and non-trivial band structures in ternary rare-earth GdCr_(6)Ge_(6) induces exotic and abundant electro-magnetic phenomena.In this work,we perform a systematical investigation on critical behaviors and magnetic properties of the single-crystal GdCr_(6)Ge_(6).The temperature,field,and angle dependence of magnetization unveils strong magnetic anisotropy along the c-axis and isotropic characteristic in the ab-plane.Critical exponentsβ=0.252(1),γ=0.905(9),δ=4.606(3)for H//ab,andβ=0.281(3),γ=0.991(8),δ=4.541(5)for H//c are obtained by the modified Arrott plot method(MAP)and critical isotherm(CI)analysis.The determined exponents for both directions are consistent with the theoretical prediction of a tricritical mean-field model.Based on detailed magnetization measurements and universality scaling,comprehensive magnetic phase diagrams of GdCr6Ge6for H//ab and H//c are constructed,which reveal that the external field induces a ferromagnetic(FM)transition for H//ab while a ferrimagnetic(FIM)one for H//c.Two tricritical points are determined for H//ab(11.2 K,266.3 Oe)and H//c(11.3 K,3.3 kOe)on the phase diagrams,respectively.The field-induced anisotropic magnetic configurations and multiple phases are clarified,where the moments of Gd and Cr form FM coupling for H//ab while FIM one for H//c via the interaction between Gd and Cr sublattices.

Phenomenon of multiple field-induced phase transition in PLZST antiferroelectric ceramics

The multiple field-induced phase transition in 4 at.% La modified Pb(Zr,Sn,Ti)O 3 family with temperature from -40℃ to 45℃ in reported. Two electric field-induced transitions from a metastable antiferroelectric phase to two ferroelectric phases are observed is polarization at the applied field of 4 MV/m. The critical field of phase transition between two ferroelectric phases is not larger than 2.5 MV/m, about ten to twenty percent of that ever found in PZT based ceramics. Lattice structure is shown to be orthorhombic by X-ray diffraction. Dielectric investigation reveals a relaxor-like ferroelectric behavior. Temperature-electric field phase diagram is also presented. An appreciate kind of materials is provided to investigate multiple field-induced phase transition with PZT-based ceramics.

Sol-gel auto-combustion synthesis of K_xNa_(1-x)NbO_3 nanopowders and ceramics: Dielectric and piezoelectric properties

The KxNa1-xNbO3 nanopowders with cubic-like morphology and an average size of about 50 nm were synthesized by sol-gel auto-combustion method.And then,the ceramics were prepared and the phase transition,microstructure and electrical properties of the KxNa1-xNbO3 ceramics were investigated.Pure perovskite phases of the KxNa1-xNbO3 ceramics were confirmed by XRD patterns and the K0.50Na0.50NbO3 ceramics show the coexistence of orthorhombic and monoclinic structures.SEM micrographs show that all samples have bimodal grain size distributions and the number of the small grains decrease with increasing K+content in the bimodal grain size distribution system.The K0.50Na0.50NbO3 ceramics with the uniform grain size and the maximum density show excellent electrical properties withεr=467.40,tanδ=0.020,d33=128 pC/N and kp=0.32 at the room temperature,demonstrating that the properties of the K0.50Na0.50NbO3 powers prepared by sol-gel auto-combustion are excellent and the ceramics are promising lead-free piezoelectric materials.

The electric and magnetic properties of epitaxially grown A0.5-xLaxSr0.5MnO3 （A=Pr, Nd） thin film

The epitaxial （single crystal-like） Pr0.4La0.1Sr0.5MnO3 （PLSMO） and Nd0.35La0.15Sr0.5MnO3 （NLSMO） thin films are prepared and characterized, and the electric and magnetic properties are examined. We find that both PLSMO and NLSMO have their own optimum deposition temperature （To） in their growing into epitaxial thin films. When the deposition temperature is higher than To, a c-axis oriented but polycrystalline thin film grows; when the deposition temperature is lower than To, the thin film tends to be a-axis oriented and also polycrystalline. The most important point is that for the epitaxial PLSMO and NLSMO thin films the electronic phase transitions are closely consistent with the magnetic phase transitions, i.e. an antiferromagnetic phase corresponds to an insulating state, a ferromagnetic phase corresponds to a metallic state and a paramagnetic phase corresponds to a semiconducting state, while for the polycrystalline thin films the electronic phase transitions are always not consistent with the magnetic transitions.

High pressure electrical transport behavior in SrF_2 nanoplates

The charge transport behavior of strontium fluoride nanocrystals has been investigated by in situ impedance measurement up to 35 GPa.It was found that the parameters changed discontinuously at each phase transition.The charge carriers in SrF2nanocrystals include both F~-ions and electrons.In the Fm3 m phase,pressure makes the electronic transport easier,while makes it more difficult in the Pnma phase.The defects at grain boundaries dominate the electronic transport process.Pressure could make the charge-discharge processes in the Fm3 m phase much easier,but make it more difficult in the Pnma phase.

The Effects of Magnetic Dopant on the Structural and Electrical Properties in Superconducting YBaCu₃O_7-δCeramic

The work reported in this paper aims at a better understanding of the magnetic doping effects on the structural and electrical properties for a series of YBa2(Cu1-xCox)3O7-δ ceramics. The Co doped YBa2Cu3O7-δ are (YBCO) prepared by conventional solid state reaction method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), differential thermal analysis (DTA) and resistivity measurements. The crystal lattice parameters are found to change due to the cobalt doping and tendency to a structure phase transition from orthorhombic to tetragonal, which is confirmed by the decrease of the degree of orthorhombicity. The morphology examination with SEM revealed gradual increases of grain size with x = 0.02 Co, a high porosity is observed in the doped samples compared to the pure one. The decomposition temperature of YBCO is pushed from temperatures above 975°C to lower temperatures of 945°C. The resistivity measurements of doped samples with x = 0.04 and 0.06;shows a deviation in from T-linear behavior due to the opening of a pseudogap.

Structural phase transition, optical and pyroelectric properties of lead-free single crystals

0.14 at%Mn-doped 0.95(Na1/2Bi1/2)TiO3-0.05BaTiO3(0.95NBT-0.05BT)lead-free single crystals were grown by a top-seeded solution growth method(TSSG).X-ray powder diffraction measurement showed that the as-grown single crystals exhibit rhombohedral perovskite structure with apparent distortion.With the increase of temperature,successive structural phase transitions occur in the Mn-doped 0.95NBT-0.05BT single crystals.After poling,apparent dielectric anomaly is induced accompanied by the increase of the character of diffuse phase transition and the decrease of the value of dielectric constant.The Mn-doped0.95NBT-0.05BT single crystals exhibit complex domain structure,in which micro and macro domains coexist with statistically 4mm symmetry.The Mn-doped 0.95NBT-0.05BT lead-free single crystals exhibit excellent piezoelectric and pyroelectric properties,which will lead to promising advance in piezoelectric and pyroelectric applications.The infrared-absorption band occurred around 630.6 cm 1can be assigned to the"stretching"normal vibration of[Na1/2Bi1/2]/Ti-O group.The three diffused Raman bands centered around 300,560 and 800 cm 1can be attributed to F2g[TiO6]bending vibration,A1g[TiO6]stretching vibration and"soft mode"mixed by bending and stretching vibrations.

Electrical conductivity and vibrational studies induced phase transition in[N(C_(3)H_(7))_(4)]_(2)ZnBr_(4)compound

Bis-Tetrapropylammonium tetrabromozincate was synthesized and characterized by X-ray powder diffraction,as well as vibrational and impedance spectroscopy.Rietveld’s refinement of X-ray diffractogram confirmed the crystallization of the compound through the monoclinic system(space group C_(2/c)).A temperature study of Raman scattering revealed two phase transitions at approximately T_(1)=340 K and T_(2)=393 K.The wavenumber and the line width’s evolution as a function of temperature showed some peculiarities associated with these transitions,which suggests that they are governed by the reorientation of the organic part[N(C_(3)H_(7))_(4)]+.The complex impedance plotted as a double semicircular arc in the studied temperature range and the centers of these semicircles lie below the real axis,which indicates that the material is an on-Debye type.These semicircular arcs are related to the bulk and the grain boundary effects.Furthermore,the alternating current conductivity of[N(C_(3)H_(7))_(4)]_(2)ZnBr_(4)obeyed Jonscher’s law:σ_(AC)(ω)=σ_(dc)+Aω^(s) and the conduction could be attributed to the correlated barrier hopping(CBH)model in both region(I)and(II)and the Non-overlapping Small Polaron Tunneling(NSPT)in region(III).

Dielectric behavior and phase transition in [111]-oriented PIN–PMN–PT single crystals under dc bias

Temperature and electric field dependences of the dielectric behavior and phase transition for[111]-oriented 0.23PIN–0.52PMN–0.25PT(PIN-PMN–0.25PT)and 0.24PIN–0.43PMN–0.33PT(PIN–PMN–0.33PT)single crystals were investigated over a temperature range from
100℃ to 250℃ using field-heating(FH)dielectric measurements.The transition phenomenon from ferroelectric microdomain to macrodomain was found in rhombohedra(R)phase region in the single crystals under dc bias.This transition temperature T_(f) of micro-to-macrodomain is sensitive to dc bias and move quickly to lower temperature with increasing dc bias.The phase transition temperatures in the two single crystals shift toward high temperature and the dielectric permittivities at the phase transition temperature decrease with increasing dc bias.Especially,the phase transition peaks are gradually broad in PIN–PMN–0.33PT single crystal with the increasing dc bias.Effects of dc bias on the dielectric behavior and phase transition in PIN–PMN–PT single crystals are discussed.

有机阳离子插层调控二维反铁磁MPX_(3)磁性能

电控磁效应调控二维(2D)反铁磁(AFM)材料的研究结合了电控磁效应与半导体工艺兼容且低能耗的优势,2D材料范德瓦耳斯界面便于异质集成以及AFM材料无杂散场、抗外磁场干扰、内禀频率高的优势,成为领域内研究的重点.载流子浓度调控是电控磁效应的主要机制,已被证明是调控材料磁性能的有效途径.层内AFM材料的净磁矩为零,磁性调控测量存在挑战,故其电控磁效应研究尚少且潜在的机制尚不清楚.基于有机阳离子的多样性,本文利用有机阳离子插层系统地调控了2D层内AFM材料MPX_(3)(M=Mn,Fe,Ni;X=S,Se)的载流子浓度,并研究了电子掺杂对其磁性能的影响.笔者在MPX_(3)家族材料中发现了依赖载流子浓度变化的AFM-亚铁磁(FIM)/铁磁(FM)的转变,并结合理论计算揭示了其调控机制.本研究为2D磁性材料的载流子调控磁相变提供了新的见解,并为研究2D磁体的电子结构与磁性之间的强相关性以及设计新型自旋电子器件开辟了一条途径.

Exploring dielectric phenomena in sulflower-like nanostructures via Monte Carlo technique

This research focuses on the electric behavior of a mixed ferrielectric sulflower-like nanostructure.The structure includes a core with spin S_(i)^(Z)-1 atoms and a shell with spin σ_(j)^(Z)-5/2 atoms.The Blume–Capel model and the Monte Carlo technique(MCt)with the Metropolis algorithm are employed.Diagrams are established for absolute zero,investigating stable spin configurations correlated with various physical parameters.The MCt method explores phase transition behavior and electric hysteresis cycles under different physical parameters.