Metal Phase Transition Research Articles

Spinning Liquid Metal Droplets on Ice.

The non-contact and non-wetting droplet motion isolated from the solid surface has a high degree of freedom and thus can exhibit many peculiar interfacial phenomena. Here, an experimental phenomenon of spinning liquid metal droplets on an ice block is discovered, which adopts the dual solid-liquid phase transition of the liquid metal and the ice. The whole system is somewhat a variant of the classic Leidenfrost effect, which directly uses the latent heat released by the spontaneous solidification of the liquid metal droplet as a heat source to melt the ice and create an intervening lubricant water film. Interestingly, it is found that the droplets on ice become very mobile and undergo rapid spin as the solidification process proceeds. A series of comparative experiments clarify that the circumferential driving force comes from the escaping bubbles as the ice melts. Furthermore, by comparing the motion characteristics of different kinds of liquid metal droplets and solid balls on ice and investigating their physical properties and heat transfer, it is disclosed that the spin effect can be universal for objects of different materials, as long as the two necessary elements of rapid liquid film establishment and gas bubble release can be satisfied simultaneously.

Kinetically-decoupled electrical and structural phase transitions in VO2

Vanadium dioxide (VO2) has drawn significant attention for its near room temperature insulator to metal transition and associated structural phase transition. The underlying Physics behind the temperature induced insulator to metal and concomitant structural phase transition in VO2 is yet to be fully understood. We have investigated the kinetics of the above phase transition behaviors of VO2 with the help of resistivity measurements and Raman spectroscopy. Resistance thermal hysteresis scaling and relaxation measurements across the temperature induced insulator to metal transition reveal the unusual behaviour of this first-order phase transition, whereas Raman relaxation measurements show that the temperature induced structural phase transition in VO2 follows usual behaviour and is consistent with mean field prediction. At higher temperature sweeping rates decoupling of insulator to metal transition and structural phase transition have been confirmed. The observed anomalous first order phase transition behavior in VO2 is attributed to the unconventional quasi particle dynamics, i.e. significantly lowered electronic thermal conductivity across insulator to metal transition, which is confirmed by ultrafast optical pump-probe time domain thermoreflectance measurements.

Study on the influence of metal phase transition on transport coefficient calculation of gas–metal plasma mixtures

In most industrial applications, plasma has an important feature that the erosion products produced by plasma will undergo a phase transition and affect the properties of plasma mixtures. Calculating the transport coefficients of the plasma mixtures, usually, gas–metal mixtures, is an important approach to study this feature. However, most transport coefficient calculation methods have some difficulties in dealing with the solid and liquid components of gas–metal plasma mixtures. In this study, a modified method for calculating transport coefficients of gas–metal plasma mixtures containing solid and liquid status is proposed, considering that the liquid and solid components are usually in the form of clusters. Based on this modified method, the influence of the metal phase transition on the transport coefficients of gas–metal plasma mixture is explored with the example of H2–Cu plasma mixture. The findings revealed in this study are as follows: (1) The modified calculation method is applicable for not only gas–metal plasma mixtures but also other plasma mixtures containing solid and liquid status. (2) Ignoring the metal phase transition in the calculation of transport coefficients of gas–metal plasma mixtures will inevitably produce considerable variances. (3) The variances, caused by ignoring the metal phase transition, are tightly associated with the pressure, the proportion of metal, and the unbalanced degree of gas–metal plasma mixtures. In summary, the variances caused by ignoring the metal phase transition might be ignorable only when the pressure, proportion of metal, and unbalanced degree of gas–metal plasma mixture are all in extremely small values.

Origin of superconductivity in hole doped SrBiO3 bismuth oxide perovskite from parameter-free first-principles simulations

The recent discovery of nickel oxide superconductors have highlighted the importance of first-principles simulations for understanding the formation of the bound electrons at the core of superconductivity. Nevertheless, superconductivity in oxides is often ascribed to strong electronic correlation effects that density functional theory (DFT) cannot properly take into account, thereby disqualifying this technique. Being isostructural to nickel oxides, Sr1-xKxBiO3 superconductors form an ideal testbed for unveiling the lowest theory level needed to model complex superconductors and the underlying pairing mechanism yielding superconductivity. Here I show that parameter-free DFT simulations capture all the experimental features and related quantities of Sr1-xKxBiO3 superconductors, encompassing the prediction of an insulating to metal phase transition upon increasing the K doping content and of an electron-phonon coupling constant of 1.22 in sharp agreement with the experimental value of 1.3 ± 0.2. The proximity of a disproportionated phase is further demonstrated to be a prerequisite for superconductivity in bismuthates.

Tunable bi-direction terahertz vortex beam generator based on Dirac semimetals

We proposed a tunable bi-direction terahertz vortex beam generator based on Dirac semimetals (DSMs) and Vanadium dioxide (VO2). The insulator–metal phase transition of VO2 occurs by changing the external temperature, thus realizing a switch between the transmissive vortex beam and the reflective vortex beam. We design a vortex beam generator with topological charges −1, −2, ＋3 in transmission mode and achieve tunable terahertz vortex beam from 0.89 THz to 1.13 THz by changing the Fermi energy level of the DSMs. In addition, the proposed metasurface generates a broadband terahertz vortex beam with topological charges −1, −2, ＋3 from 1.0 THz to 1.8 THz when VO2 is in the metal state.

3D-strain-induced multiple semiconductor–metallic phase transition in monolayer SrTiO3

The recent discovery of monolayer perovskite has attracted much attention due to its abundant physical properties and extreme flexible properties. However, multiple strain effects on its physical properties are not clear. Herein, by means of first-principles calculations, we show that under 3D-multiple strains, the monolayer SrTiO3 (STO) can be tuned from the semiconductor into metallic phases via the in-plane strain engineering. The bandgap of the monolayer STO increases with increasing positive biaxial strain and reduces to zero when a negative biaxial strain is applied. In addition, we found that the metallic phase of the monolayer STO under the in-plane biaxial strain will drop back into the semiconductor phase when an out-of-plane compressive strain is added. By analyzing the electronic band structure, density of states, and orbital-projected band structures, we found that the p-orbitals of Sr and O atoms as well as the d-orbitals of Sr atoms make significant effects on the multiple semiconductor–metallic phase transition. In summary, the abundant semiconductor–metallic phase transition of the monolayer STO under 3D-strain conditions opens up an opportunity for its application in modulating the electronic properties of 2D materials.

Fundamental limits for transmission modulation in VO2 metasurfaces

The interest in dynamic modulation of light by ultra-thin materials exhibiting insulator–metal phase transition, such as VO 2 , has rapidly grown due to the myriad industrial applications, including smart windows and optical limiters. However, for applications in the telecommunication spectral band, the light modulation through a thin VO 2 film is low due to the presence of strong material loss. Here, we demonstrate tailored nanostructuring of VO 2 to dramatically enhance its transmission modulation, reaching a value as high as 0.73, which is 2 times larger than the previous modulation achieved. The resulting designs, including free-topology optimization, demonstrate the fundamental limit in acquiring the desired optical performance, including achieving positive or negative transmission contrast. Our results on nanophotonic management of lossy nanostructured films open new opportunities for applications of VO 2 metasurfaces.

A triple point of water cell-based fixed-point blackbody for radiation thermometry

The radiation temperature metrology above 150 °C relies heavily on the use of physical interpolation equations and known reference temperature (provided by solid–liquid phase transition of high-purity metals and metal-carbon eutectic alloys) fixed-point blackbodies. Recent achievements in thermal infrared detector technologies triggered the extension of the scale interpolation below this temperature down to 0 °C by using the reference temperatures provided by Sn, In, Ga fixed-points and ice-point, where the reference temperature of the later is dependent on external parameters. In this work, we demonstrate that the triple-point of water (TPW) based fixed-point blackbody is the metrologically grounded alternative to the ice-point. For this purpose, a fixed-point blackbody, incorporating only a cavity and large area TPW (LATPW) cell was designed, constructed, and validated for the precise calibration of radiation thermometers (RTs) and thermal cameras at the thermodynamic temperature of TPW. The conceptual design of the LATPW cells is similar to the ones used in contact thermometry, where a thermometer well of the cell is employed as a borehole for a cavity, where the cavity is easily detachable. Four different cavities (two different designs with aperture sizes of 40 mm and 50 mm) and three LATPW cells with two distinct well geometries were comparatively studied in several combinations. The largest absolute temperature difference observed between the primary level reference TPW cell (used in contact thermometry) and the LATPW cells is measured to be only 0.37 mK. Radiometric measurements demonstrate that all radiators maximally reflect the blackbody condition including emissivity close to unity, high uniformity across the aperture and high temporal stability. The simplicity of maintenance and easy in-field usage (only distilled water and dry ice are required) make the TPW blackbodies very versatile for the in-situ calibrations of RTs and thermal cameras, allowing its application in many areas including clinical environments.

Recent Progress in Phase Stability and Elastic Anomalies of Group VB Transition Metals

Recently discovered phase transition and elastic anomaly of compression-induced softening and heating-induced hardening (CISHIH) in group VB transition metals at high-pressure and high-temperature (HPHT) conditions are unique and interesting among typical metals. This article reviews recent progress in the understanding of the structural and elastic properties of these important metals under HPHT conditions. Previous investigations unveiled the close connection of the remarkable structural stability and elastic anomalies to the Fermi surface nesting (FSN), Jahn–Teller effect, and electronic topological transition (ETT) in vanadium, niobium, and tantalum. We elaborate that two competing scenarios are emerging from these advancements. The first one focuses on phase transition and phase diagram, in which a soft-mode driven structural transformation of BCC→RH1→RH2→BCC under compression and an RH→BCC reverse transition under heating in vanadium were established by experiments and theories. Similar phase transitions in niobium and tantalum were also proposed. The concomitant elastic anomalies were considered to be due to the phase transition. However, we also showed that there exist some experimental and theoretical facts that are incompatible with this scenario. A second scenario is required to accomplish a physically consistent interpretation. In this alternative scenario, the electronic structure and associated elastic anomaly are fundamental, whereas phase transition is just an outcome of the mechanical instability. We note that this second scenario is promising to reconcile all known discrepancies but caution that the phase transition in group VB metals is elusive and is still an open question. A general consensus on the relationship between the possible phase transitions and the mechanical elasticity (especially the resultant CISHIH dual anomaly, which has a much wider impact), is still unreached.

Adsorption of Metals on (100) Metallic Surfaces: Monte Carlo Simulations and Geometrical Phase Transitions.

Adsorption and continuous phase transitions (percolation) of metals on (100) metallic surfaces are studied by means of Monte Carlo simulations and the finite-size scaling theory. The studied systems are Ag/Au(100), Au/Ag(100), Ag/Pt(100), and Pt/Ag(100), and the embedded atom method (EAM) is employed for energy calculations. Pairwise interactions are also considered for comparative purposes. The study of critical exponents reveals that these systems belong to the same universality as random sequential adsorption (RSA). For the four systems studied, and the two kinds of interactions considered, phase diagrams of percolation threshold, θc, as a function of temperature are presented. In all cases, and for all temperatures, θc is always below the value corresponding to RSA, as expected for attractive interactions, and it tends to that value as T → ∞. At intermediate temperatures, a particular behavior is found for EAM interactions.

Electrospun perovskite nano-network for flexible, near-room temperature, environmentally friendly and ultrastable light regulation

• Perovskite-sodium alginate network is proposed for fast and stable light regulation • Lead leakage of perovskite is inhibited to the drinking standard by sodium alginate • The “egg-box” structure of sodium alginate is proved to be valid for lead caging • Cycling stability of over 1200 cycles is successfully demonstrated • For the application of smart window, energy of over 55.5 J m -3 min -1 is saved Light regulation devices are essential for signal modulation, information encryption and energy-saving smart windows. Recently, due to their excellent stimuli-responsive properties, lead halide perovskites have shown great potential. However, the high transition temperature, irreversibility of the phase transition and toxicity of heavy metals make perovskite materials unsuitable for devices related to human activity. Herein, for the first time, a flexible perovskite nano-network is proposed and its application as a smart window is demonstrated. The perovskite-sodium alginate (SA) nano-network showed a 31.6 °C (20% RH) transition temperature and stability over 1200 cycles. The hydrophobic surface and the “egg-box” structure formed by SA make that the lead leakage is only 2.569 ppb, which is much higher than the drinking water standard. This work provides a successful demonstration for energy-efficient buildings and inspires future nontoxic perovskite-based devices through heavy metal control. A flexible hybrid SA-perovskite nano-network for automatic light regulation. Pb leakage has been reduced to as low as 2.569 ppb by a strong SA-Pb bond, which meets the drinking water standard (US Federal 40 CFR 141 regulation). Under AM1.5G solar illumination, an energy saving rate of over 55.5 J m-3 min-1 was observed. Thanks to the framework that balanced the volume change, a stable color shift was achieved over 1200 cycles without weakening.

Analytical Investigation of Lightning Strike-Induced Damage of OPGWs Based on a Coupled Arc-Electrical-Thermal Simulation

This study investigated lightning-induced damage of optical fiber overhead ground wires (OPGWs) through damage measurements, numerical simulations and influencing factor analysis. A high-precision damage measurement method was proposed to calculate the lightning damage volume based on laser profile scanning and a developed data processing program. The time-and-space-varying current and heat flows obtained from an arc magnetohydrodynamic model were loaded on OPGWs by stepwise segmental injection to establish a coupled arc-thermal-electric model and simulate the heating and damage behavior of OPGWs. The comparisons indicated that the simulated metal phase transition region agreed well with the actual damage distribution, and the area surrounded by the aluminum melting point isotherm provided a good prediction of the arc sweep damage. The hysteresis of the temperature rise suggested that lightning damage was dominated by heat flow conduction rather than the Joule heating effect. Furthermore, the continuing current was the main cause of severe damage. The damage volume increased linearly with increasing charge transfer. As the discharge gap increases, the arc loading intensity decreases, but the damage volume undergoes a non-monotonic change, which is due to the complex variations in the arc attachment area regulated by the discharge gap and current intensity.

Theoretical investigation of the structural properties of SnSe[formula omitted]S[formula omitted]: A density functional study

Pressure and doping tuning provide an important gateway to the discovery of materials with improved characteristics by modifying the interaction parameters and material structural characteristics and other properties. The enhancement of the thermoelectric properties of the multivalley systems like SnSe has emerged as a key aspect for new technologies. In order to understand the evolution of the characteristics, we study SnSe1−xSx for x=0, 0.25, 0.5, 0.75 and 1. The elastic constants of SnSe1−xSx were calculated to analyze the mechanical stability of the structures. Moreover, the Voigt–Reuss–Hill method was used to determine the elastic moduli. Furthermore, the evolution of SnSe1−xSx under high pressure was also analyzed. The pressure induced semiconductor–metal phase transition was monitored. Dependencies of the energy-gap values on doping and pressure demonstrate a substantial increase with the increase in the S content. Band-structures, density of states and Fermi level shift corroborate the above characteristics. Pressure and doping dependencies of the Raman spectra have also been considered. Our comprehensive study on the effects of pressure and doping on this system should lead to tuning of the materials properties for advanced technological applications.

Gifts from anomalies: Exact results for Landau phase transitions in metals

Non-Fermi liquid phenomena arise naturally near critical points of Landau ordering transitions in metallic systems, where strong fluctuations of a bosonic order parameter destroy coherent quasiparticles. Despite progress in developing controlled perturbative techniques, much of the low energy physics of such metallic quantum critical points remains poorly understood. We demonstrate that exact, non-perburbative results can be obtained for both optical transport and static susceptibilities in “Hertz-Millis” theories of Fermi surfaces coupled to critical bosons. Such models possess a large emergent symmetry and anomaly structure, which we leverage to fix these quantities. In particular, we show that in the infrared limit, the boson self energy at zero wave vector, \mathbf{q}=0𝐪=0, is a constant independent of frequency, and the real part of the optical conductivity, \sigma(\omega)σ(ω), is purely a delta function Drude peak with no other corrections. Therefore, further frequency dependence in the boson self energy or optical conductivity can only come from irrelevant operators in a clean system. Exact relations between Fermi liquid parameters as the critical point is approached from the disordered phase are also obtained. The absence of a universal, power law frequency dependence in the boson self energy contrasts with previous perturbative calculations, and we explain the origin of this difference.

Pressure-induced structural phase transitions of zirconium: an ab initio study based on statistical ensemble theory

Recently, we put forward a direct integral approach to solve the partition function with ultrahigh efficiency and precision, which enables the rigorous ensemble theory to investigate phase behaviors of realistic condensed matters and has been successfully applied to the phase transition of vanadium metal (Ning et al 2022 J. Phys.: Condens. Matter 34 425404). In this work, the approach is applied to the structural phase transitions of zirconium metal under compressions up to 160 GPa and ultrahigh calculation precision is achieved. For the obtained equation of state with pressure over 40 GPa, the deviations from latest experiments are within and the computed transition pressure of is 6.93 GPa, which is about five times larger than previous theoretical predictions and in excellent agreement with the measured range of 5–15 GPa. Our results support the argument that there is no existence of the isostructural phase transition of Zr metal that was asserted by recent experimental observations.

AC/DC Thermal Nano-Analyzer Compatible with Bulk Liquid Measurements

Nanocalorimetry, or thermal nano-analysis, is a powerful tool for fast thermal processing and thermodynamic analysis of materials at the nanoscale. Despite multiple reports of successful applications in the material sciences to study phase transitions in metals and polymers, thermodynamic analysis of biological systems in their natural microenvironment has not been achieved yet. Simply scaling down traditional calorimetric techniques, although beneficial for material sciences, is not always appropriate for biological objects, which cannot be removed out of their native biological environment or be miniaturized to suit instrument limitations. Thermal analysis at micro- or nano-scale immersed in bulk liquid media has not yet been possible. Here, we report an AC/DC modulated thermal nano-analyzer capable of detecting nanogram quantities of material in bulk liquids. The detection principle used in our custom-build instrument utilizes localized heat waves, which under certain conditions confine the measurement area to the surface layer of the sample in the close vicinity of the sensing element. To illustrate the sensitivity and quantitative capabilities of the instrument we used model materials with detectable phase transitions. Here, we report ca. 106 improvement in the thermal analysis sensitivity over a traditional DSC instrument. Interestingly, fundamental thermal properties of the material can be determined independently from heat flow in DC (direct current) mode, by using the AC (alternating current) component of the modulated heat in AC/DC mode. The thermal high-frequency AC modulation mode might be especially useful for investigating thermal transitions on the surface of material, because of the ability to control the depth of penetration of AC-modulated heat and hence the depth of thermal sensing. The high-frequency AC mode might potentially expand the range of applications to the surface analysis of bulk materials or liquid-solid interfaces.

First-principle calculations of the structural, vibrational, mechanical, electronic, and optical properties of ε-O8 under pressure.

The vibrational, mechanical, electronic, and optical properties of the ε-O8 phase in the pressure range of 11.4-70 GPa were studied by the first-principle calculation method. The phonon dispersion curves have a tiny virtual frequency at 60 GPa, which indicates that ε-O8 is dynamically unstable at 60 GPa. However, the 3-BM EOS demonstrates that the unit cell is stable up to 70 GPa. It has been shown that ε-O8 remains ductile within the whole applied pressure range. Concurrently, we calculated the variation of the band gap of ε-O8 in the pressure range of 11.4-70 GPa. The results show that the band gap of ε-O8 decreases with increasing pressure. Notably, the band gap disappears within the range of 50-60 GPa, which reveals that the metallic phase transition occurs within this pressure range.

Soft shape-programmable surfaces by fast electromagnetic actuation of liquid metal networks

Low modulus materials that can shape-morph into different three-dimensional (3D) configurations in response to external stimuli have wide-ranging applications in flexible/stretchable electronics, surgical instruments, soft machines and soft robotics. This paper reports a shape-programmable system that exploits liquid metal microfluidic networks embedded in an elastomer matrix, with electromagnetic forms of actuation, to achieve a unique set of properties. Specifically, this materials structure is capable of fast, continuous morphing into a diverse set of continuous, complex 3D surfaces starting from a two-dimensional (2D) planar configuration, with fully reversible operation. Computational, multi-physics modeling methods and advanced 3D imaging techniques enable rapid, real-time transformations between target shapes. The liquid-solid phase transition of the liquid metal allows for shape fixation and reprogramming on demand. An unusual vibration insensitive, dynamic 3D display screen serves as an application example of this type of morphable surface.

Iron-Poor Ferrites for Low-Temperature CO2 Conversion via Reverse Water–Gas Shift Thermochemical Looping

CO2 utilization via the reverse water–gas-shift (RWGS) reaction for the production of CO and then long-chain hydrocarbons is a potentially scalable method to mitigate rising global CO2 emissions, if appreciable CO yields can be achieved at low reaction temperatures. Here, we report that Fe0.35Ni0.65Ox achieves, to the best of our knowledge, a record high experimentally measured CO yield of 80 mL CO/gMOx/cycle at low reaction temperatures (500 °C for both oxidation and reduction steps) in a chemical looping (CL) process. This reported yield is substantially higher than previously reported RWGS-CL metal oxides at 500 °C. We identified the composition of the metal oxide Fe0.35Ni0.65Ox using the Calculation of Phase Diagrams (CALPHAD) methodology to screen and filter through many combinations of metal oxides. We then experimentally tested this Fe0.35Ni0.65Ox metal oxide for chemical looping RWGS and utilized X-ray characterization techniques and CALPHAD to find that a spinel to metallic phase transition gives Fe0.35Ni0.65Ox its noteworthy CO yield and oxygen capacity. We emphasize the importance of thermodynamics calculations and CALPHAD screening to quickly search through the vast design space of metal oxides to greatly reduce the amount of necessary experimentation.

Multi spectral switchable infra-red reflectance resonances in highly subwavelength partially oxidized vanadium thin films

Phase transition materials are promising for realization of switchable optics. In this work, we show reflectance resonances in the near-infrared and long-wave infrared wavelengths in highly subwavelength partially oxidized Vanadium thin films. These partially oxidized films consist of a multilayer of Vanadium dioxide and Vanadium as shown using Raman spectroscopy and four-probe measurements. As Vanadium dioxide is a phase transition material that shows insulator to metal phase transition at 68 °C, the observed infra-red resonances can be switched with temperature into a high-reflectance state. The wavelength of these resonances are passively tunable as a function of the oxidation duration. The obtained reflectance resonance at near-infrared wavelength red shifts from 1.78 μm to 2.68 μm with increasing oxidation duration while the long-wavelength infrared resonance blue shifts from 12.68 μm to 9.96 μm. To find the origin of the reflectance resonances, we model the reflectance spectra as a function of the oxidation duration using the transfer matrix method. The presented model captures the dual reflectance resonances reasonably well. These passive wavelength-tunable and switchable resonances with easy to fabricate lithography-free multilayer structure will be useful for multispectral applications such as camouflage, spectral selective microbolometer, and thermal management.