Phase Transition Properties Research Articles

Rotational effect on shock-induced phase transitions of the condensed fluid in the hard-sphere model

The properties of fluid phase transition can be distinctly induced by shock-waves in the hard-sphere model. Typical thermal and dynamic characteristics of the fluid have been described by conditions in the Rankine–Hugoniot (RH) theory based on Euler equations. Due to the strong impact from shock-waves, states of excitation or even phase transition can be detected. However, various factors can influence the jump in the fluid, such as degrees of freedom in molecules. The simple hard-sphere model typically assumes three degrees, neglecting internal freedoms of particles. However, the effect of molecular rotation often plays a significant role under general conditions, influencing fluid phase transition. So, the rotational freedom of molecules has been taken into the thermal equations in this work. The excited state or phase transition of the fluid has been substantiated by using the RH theory, and we have found that internal freedoms of the fluid can have a dramatic effect on the physical properties during phase transition processes.

Phase transition, antiferroelectric and pulse discharge properties of (1-x)NaNbO3–xBi2/3ZrO3 ceramics

In present work, a novel ceramic composition of (1-x)NaNbO3-xBi1/3ZrO3 was designed to break through the bottleneck that high energy density (Wd) and power density (PD) are difficult to coexist for pulse discharge applications. The modified ceramics exhibited well-defined double P-E loops, a high PD of ∼22.5 MW/cm3 and a high Wd of ∼0.22 J/cm3 simultaneously, superior to other published works. The structural analysis showed that the unstable antiferroelectric P phase gradually transforms into the stable R phase after Bi1/3ZrO3 modification, mainly due to the great decrease of P-R transition temperature to 175 oC. In addition, P-E and I-E results under large signals further demonstrated the phase transition from P to R phase. Our work provides a significant way to regulate the phase transition of sodium niobate.

Correlation between the symmetry energy slope and the deconfinement phase transition

We study how the nuclear symmetry energy slope (L) can affect the hadron-quark phase transition and neutron star properties. We show that the main physical quantities as the critical chemical potential and pressure are strongly influenced by the symmetry energy slope. In extreme cases, the total amount of deconfined quarks can reach up to 99% of the hybrid star mass. Published by the American Physical Society 2024

Vaporization Phase Transition in Cryogenic Liquid Oxygen Sealing Film on Spiral Groove Faces.

The property of vaporization phase transition in liquid oxygen face seals is a key factor affecting the stability of mechanical face seals in many fields, especially under cryogenic conditions. Here, a numerical model based on the saturated vapor pressure is established to investigate the vaporization phase transition property of liquid oxygen sealing film. The novelty of this model is to take the influence of heat transfer and face distortions into consideration at the same time. The pressure and temperature distributions as well as face distortions are calculated, and then the property of vaporization phase transition and sealing performance are analyzed. It is found that spiral grooves may lead to the complex film temperature distributions and irregular vaporization distributions. With the increase in seal temperature and decrease in seal pressure, the vaporization area extends from the low-pressure side to the grooves area, and the vaporization rate increases rapidly. The more important thing is that the vaporization often brings a drastic fluctuation and non-monotonic change in opening force. Specifically, with the increase inin seal temperature from 55 K to 140 K, the opening force fluctuates violently, and the fluctuation range is more than 50%, showing an obvious instability. Finally, this study provides a design range of pressure and temperature values for liquid oxygen face seals. In these ranges, this kind of face seals can have a stable operation, which is beneficial to the practice engineering related to the complex properties of sealing fluid.

Investigation on the phase transition, geometric and electronic properties of Bi-doped CsPbBr3 perovskites

Given the ongoing debate regarding the potential impact of Bi dopant on the phase transition of CsPbBr3, our study aims to provide a comprehensive understanding of this phenomenon. Through a multifaceted examination encompassing energetic states, geometric configurations, bonding interactions, and electronic structures, we find that the inclusion of Bi dopants alone does not directly induce the orthorhombic/tetragonal phase transition in CsPbBr3. However, we observe a obvious reduction in the energetic discrepancy between these two phases, indicating an indirect stimulation of the phase transition by Bi dopants. This accelerates the stimulations originating from external environment, which may be responsible for the experimentally observed phase transition. Moreover, our investigation confirms that Bi dopants selectively weakens the bonding interaction within the Pb/Bi octahedra of the CsPbBr3 lattice in an anisotropic manner. Specifically, we identify that the weakening of the out-of-plane Bi–Br bond strength arises from the diminished bonding interaction between the p orbital of Bi and the s orbital of Br. This phenomenon results in the elongation of the metal-halide octahedra, consequently relaxing lattice distortions and twists in undoped CsPbBr3 systems, particularly pronounced in orthorhombic phases. Consequently, both orthorhombic and tetragonal CsPbBr3 lattices tend to evolve towards similar geometric configurations. Our findings reveal the significant influence of Bi dopants on the phase dynamics of CsPbBr3, a factor often overlooked in previous investigations.

Thermal and photo/electro-thermal conversion characteristics of high energy storage density expanded graphite/polyethylene glycol shaped composite phase change materials

Compared with other energy storage materials, phase change materials (PCMs) are drawing widespread attention because of their high enthalpy and low temperature change. However, its low thermal conductivity, low photo/electro-thermal conversion characteristics, phase separation and easy leakage are still urgent problems. In this work, expanded graphite/polyethylene glycol (EG/PEG) composites were prepared based on physical adsorption method, the relationship between the mass percentage of EG and the microstructure, phase transition properties (phase change enthalpy, supercooling degree) and energy conversion properties was studied. The composite PCM exhibits exceptional thermal conductivity (2.48 W·m−1·K−1, 7 folds greater than that of PEG) and outstanding melting enthalpy (161.4 J/g). The thermal conductivity of the EG/PEG composites is almost constant versus temperature over measured temperature range (26 ℃∼60 ℃). The energy conversion capacities (photo/electro-thermal conversion) increase as the expanded graphite mass fraction increases. The prepared composite PCM obviously overcomes the shortcomings of the pure polyethylene glycol, and highlights enormous application in the domains of multi-physical energy conversion and premium quality power absorption.

Ultra-broadband tunable terahertz metasurface absorber with multi-mode regulation based on artificial neural network

The multi-window tunable absorption of terahertz (THz) waves faces challenges such as a small tunable bandwidth, discontinuous tuning windows, and a complex design process. This study addresses these issues by employing inverse design based on artificial neural networks (ANN) to achieve an ultra-broadband tunable THz metasurface absorber (UTTMA). Leveraging the electrically tunable property of graphene and the phase transition property of vanadium dioxide (VO2), the UTTMA achieves multi-domain dynamic operation across a large frequency band. The design allows for arbitrary switching between multiple windows by transforming between graphene surface-localized plasmon resonance (LSPR), fundamental order surface plasmon polaritons (SPP) resonance, and graphene surface plasmon resonance (SPR), and second order SPP resonance. The tunable windows cover the range between 1.90 and 10.00 THz, encompassing four-fifths of the entire THz band, surpassing previously reported absorbers. The accuracy of the ANN inverse design is verified, and a systematic analysis of the optical performance of the UTTMA is conducted. These findings offer a viable and effective method for expanding the tunable bandwidth and simplifying the design process for THz metasurfaces.

(Benzimidazolium)2GeI4: A layered two-dimensional perovskite with dielectric switching and broadband near-infrared photoluminescence

Two-dimensional (2D) lead halide perovskites have attracted tremendous attention due to their outstanding physical properties. However, the presence of toxic lead is a major problem for large-scale applications. Here, we report the synthesis, phase transition, dielectric and photoluminescence (PL) properties of a lead-free 2D Ge-based perovskite (BIM)2GeI4 (BIM = benzimidazolium) which experiences a phase transition at 405 K accompanied by an order-disorder change of organic spacer. Moreover, the step-like dielectric transition near the phase transition temperature makes it suitable for dielectric switching. Meanwhile, (BIM)2GeI4 has a direct bandgap of 2.23 eV and broadband emission from 550 to 1000 nm, implying its unique optical property for potential near-infrared lighting and displaying. This work provides a fresh example for the development of lead-free 2D Ge-based perovskite with potential applications in the fields of optoelectronics and high temperature dielectric switching.

Focal length switchable metalens based on vanadium dioxide.

A metalens is a flat lens that can control the phase of light so that dispersed light can be reconcentrated. This study devised a tunable metalens with a switchable focal length based on the phase transition properties of vanadium dioxide (V O 2). The unit structure comprises three layers from bottom to top: gold, polyimide, and two square resonant rings. The metalens can not only transform incident x-polarized waves into y-polarized waves but also achieve beam focusing simultaneously. The designed metalens achieves polarization conversion efficiency at an operating frequency of 0.8THz. In the insulating state of V O 2, the beam focal point is at L=1914µm; in the metallic state, the wave converges at L=982µm, closely aligning with the predetermined focal length. By controlling external temperature, focal point switching can be achieved, making it highly versatile in practical applications.

Pressure-induced magnetic phase transition and related physical properties in Z1-Fe3Pd alloy

A Z1-type Fe3Pd alloy with negative enthalpy of formation at ambient pressure has been discovered recently, however, its physical properties under high pressures remain unclear. In this work, the effect of pressure on the magnetic, electronic, lattice dynamic, mechanical and thermal properties of the Z1-Fe3Pd are investigated thoroughly by the first-principles methods. Under high pressures, the Z1-Fe3Pd are energetically favorable compared to other types Fe3Pd structures. A pressure-induced magnetic phase transition from ferromagnetic (FM) to ferrimagnetic (FIM) state are found, and the FM and FIM states are dynamically and mechanically stable under high pressures. The electronic density of states for both the FM and FIM states are analyzed to understand their magnetism. These two magnetic configurations are ductile, but their elastic properties and anisotropy are quite different. Additionally, the FM and FIM states have high uniaxial magnetocrystalline anisotropy, the FM state is a semi-hard magnet, and the FIM state undergoes a transition from hard magnet to semi-hard magnet with pressure. Finally, the volume and linear thermal expansion coefficients under high pressure are calculated, and the anisotropy of thermal expansion is also discussed in detail.

Dynamic responses of steady-state transition structures under impact loading

Advancements in materials science and mechanical system have spurred widespread investigation into non-traditional structures. In particular, engineers have shown interest in steady-state transition structures with phase transition properties. In this paper, a three-dimensional steady-state transition structure was established using the genetic algorithm and three-dimensional expansion, on which the low-velocity impact tests were carried out. Force response and energy absorption of the steady-state transition structures under impact were studied. From the force response and energy absorption curves, it can be seen that the steady-state transition structures absorb and store portion of impact energy temporarily, gradually releasing it after impact peak. This unique energy behavior results in a steady state transition structure with a long impact response time and a low peak impact force under impact. In addition, investigation into energy transfer within these structures reveals that energy oscillations occur among multilayered bistable surfaces during steady-state transitions, further improving the energy dissipation. Further, the dynamic response and damage modes of the honeycomb structure and the steady state transition structure were compared, showing that the damage mode of the steady state transition structure under the impact is an overall damage, in contrast to the penetration damage of the honeycomb structure. Notably, the steady-state transition structures showcase a higher proportion of elastic strain energy during impacts, effectively delaying structural damage onset, and dispersing impact energy, thus enhancing impact resistance. In light of these findings, the demonstrated behavior of steady-state transition structures in absorbing and dissipating impact energy showcases their potential as promising avenues for the development of more effective impact protection strategies.

Resolving Phase Transition Properties of Dense Matter through Tidal-excited g-mode from Inspiralling Neutron Stars

The investigation of the phase state of dense matter is hindered by complications of first-principle nonperturbative quantum chromodynamics. By performing the first consistent general-relativistic calculations of tidal-excited g-mode of neutron stars with a first-order strong interaction phase transition in the high-density core, we demonstrate that the gravitational-wave signal during binary neutron star inspiral probes their innermost hadron-quark transition and provides potent constraints from present and future gravitational-wave detectors.

4D printed multifunctional wearable strain sensors with programmable sensing characteristics

Combining 4D-printed bilayer actuators with the slit structure and sensing capabilities unique to the process further promotes the use of 4D printing in biomedical devices, human-computer interaction, intelligent self-protection devices, and humanoid robots. In this study, we propose an adaptive multifunctional strain sensor (AMSS) 4D printing strategy based on the shape memory properties of polylactic acid (PLA), a bioslit structural sensing unit, and a bi-directional deformation design of a bilayer structure. The obtained AMSS was shown to have excellence sensitivity to strain, mechanical, and temperature stimuli. In particular, thanks to the 3D printed slit structure and phase transition properties of the PLA printing layer, the AMSS macro-microstructure can be precisely tuned, and its sensing performance is shown to be intelligently programmable. The built-in structural design-induced macro-deformation enables AMSS to adaptively fit human joint surfaces for full-range human motion recognition. In addition, the close correlation of strain-sensing during AMSS shape transformation enables position self-sensing and strain self-sensing of AMSS. Further, through the integration and separation of resistive signals, we are able to recognize temperature and mechanical stimuli. Finally, we integrate the wireless sensing module into the AMSS to improve the portability and wearability of the sensor.

Principle of multi-critical-points in the ALP-Higgs model and the corresponding phase transition

The principle of multi-critical-points (PMCP) may be a convincing approach to determine the emerging parameter values in different kinds of beyond-standard-model (BSM) models. This could certainly be applied to solve the problem of undetermined new parameters in the ALP-Higgs interaction models. In this paper, we apply this principle to such model and investigate whether there are suitable solutions. Then, using the 1-loop effective potential, we study the phase transition property of this model under the PMCP requirement. It is gratifying to find that under the requirement of PMCP, the phase transition can be not only first-order, but also strong enough to serve as a solution for electroweak baryongenesis (EWBG). Finally, we show the parameter space of ALP and provide the parameter range that leads to the first-order phase transition.

Dynamic switching: vanadium dioxide and graphene-based terahertz perfect absorber for tunable broadband absorption and tri-band absorption

In this paper, a dual-function switchable perfect absorber in the terahertz band is simulated and proposed. The design leverages the phase transition properties of vanadium dioxide (VO2) and the dynamically tunable properties of graphene. The absorber exhibits broadband absorption when VO2 is operated in the insulating state alone, with a bandwidth of 7.09 THz and a high modulation depth of 99.45% resulting in absorption levels above 90%. Additionally, by operating the graphene square ring and the graphene round ring at the Fermi levels of 0.72 eV and 0.75 eV, respectively, the absorber demonstrates tri-band absorption, making it suitable for refractive index sensing applications. The absorber’s operating frequency can be easily tuned by adjusting the conductivity of VO2 and the Fermi levels of graphene, enabling dynamic tunability. The feasibility of our work positions it as a promising candidate for designing switchable broadband and multi-band absorbers. Consequently, our research holds significant potential for applications in terahertz devices.

Ionic liquids based on carboxylate anions: Auto and hetero assembly with methylcellulose in diluted and semi-diluted regime

This study explores the impact of carboxylate ionic liquids (ILs) on the phase transition properties of methylcellulose (MC) in the diluted and semi-diluted regime. Conductivity measurements were used to examine the aggregation of ILs 1-decyl-3-methylimidazolium butanoate ([C10MIM][BUT]), 1-decyl-3-methylimidazolium crotonate ([C10MIM][CRO]), and 1-decyl-3-methylimidazolium pentanoate ([C10MIM][PEN]) in the presence and absence of MC. The interaction between ILs and MC was confirmed using 1H NMR spectroscopy. The effect of ILs on the phase transition of MC was investigated through UV–vis spectroscopy and oscillatory rheometry. Results indicated that the carboxylate ILs studied tend to interact with MC, reducing polymer-polymer interactions and the apparent viscosity of MC solutions. Furthermore, carboxylate ILs were observed to modulate the sol-gel transition temperature of MC to higher temperatures, while weakening the resulting gel compared to pure MC gels.

Growth and phase transition properties of Ta-doped VO2 single crystal microtubes

Ta-doped VO2 single crystal microtubes with rectangular cross-sections were grown by a thermal oxidation process from V–Ta alloy foils in air. Characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy revealed their morphology as hollow, rod-like single crystals. Phase transition examinations used differential scanning calorimetry demonstrated that Ta doping can effectively decrease the metal-insulator transition temperatures of VO2 by approximately 9.8 °C/at. % Ta. The phase transition behavior and growth mechanism of Ta-doped VO2 single crystal microtubes are also elucidated.

Structural phase transition and resistive switching properties of Cu x O films during post-thermal annealing

We studied the phase change and resistive switching characteristics of copper oxide (Cu x O) films through post-thermal annealing. This investigation aimed to assess the material’s potential for a variety of electrical devices, exploring its versatility in electronic applications. The Cu x O films deposited by RF magnetron sputtering were annealed at 300, 500, and 700 °C in ambient air for 4 min by rapid thermal annealing (RTA) method, and then it was confirmed that the structural phase change from Cu2O to CuO occurred with increasing annealing temperature. Resistive random-access memory (ReRAM) devices with Au/Cu x O/p+-Si structures were fabricated, and the ReRAM properties appeared in CuO-based devices, while Cu2O ReRAM devices did not exhibit resistive switching behavior. The CuO ReRAM device annealed at 500 °C showed the best properties, with a on/off ratio of 8 × 102, good switching endurance of ∼100 cycles, data retention for 104 s, and stable uniformity in the cumulative probability distribution. This characteristic change could be explained by the difference in the grain size and density of defects between the Cu2O and CuO films. These results demonstrate that superior and stable resistive switching properties of RF-sputtered Cu x O films can be obtained by low-temperature RTA.

The effect of f-electrons on the structural phase transition, mechanical and electronic properties in light rare-earth bismuthides

ABSTRACT The electronic structure, phase transition pressure and mechanical properties of light rare-earth bismuthides (PrBi, NdBi, PmBi and SmBi) have been investigated by full geometry optimization using Vienna Ab-Initio Simulation Package (VASP) which has been used in combination with the projector augmented wave (PAW) method and the generalized gradient approximation (GGA) over the local density approximation (LDA) for exchange-correlation functional. We focus our attention on the lattice constants and elastic constants of these compounds. These compounds undergo a phase transition from the NaCl (B1) structure to the body-centered tetragonal (BCT) structure. We also report the density of states (DOS) of these rare earth bismuthides. In the case of PrBi and NdBi, the 4f states are treated as valence states. The effects of on-site Coulomb repulsion and the spin-orbit coupling (SOC) on the electronic structure are also studied.

Design and demonstration of high-power density infrared nonlinear filtering window with EM shielding.

Directional energy weapons such as high-power microwaves and high-energy lasers pose a huge threat to optoelectronic detection systems. With that in mind, we designed an infrared optical window that has a nonlinear optical response to high-energy lasers and electromagnetic shielding to microwaves. By constructing a periodic metal circular hole array structure at the subwavelength scale, surface plasmons resonance is excited and its local field enhanced characteristics are utilized to form information transmission compatibility in the infrared band. At the same time, after laser etching off the subwavelength structure, the remaining metal forms a continuous conductive structure, forming an ultra-wideband shielding layer to achieve ultra-high and wide protection in the microwave band. Moreover, a layer of Ge2Sb2Te5 thin film was deposited between the transparent substrate and the metal film. Utilizing its nonlinear optical properties of high-temperature phase transition to reduce damage of directed energy weapons to the photoelectric detection system and equipment. Thus, when the photoelectric detection system or device is damaged or interfered by signals of different frequency bands or energies, the filtering window can achieve multi-mode shielding function.