Nonequilibrium Thermodynamic State Research Articles

Theoretical Analysis of Self-Shrinkage Spheroidization of Irregular Degradable Polymer Powder under Thermodynamic Nonequilibrium State

Laser three-dimensional (3D) printing offers significant advantages in integrating the shape and function of regenerative tissues through biomimetic manufacturing. However, its effectiveness is limited by the lack of specialized biopolymer powders—while solvent methods that use residual solvents produce powders with poor biocompatibility, mechanical methods result in irregularly shaped crystals. In this study, a biopolymer powder spheroidization and shaping technology, which utilizes the evolution of irregular powders into spheres with minimal surface free energy in the molten state, is proposed based on the thermodynamic principle of minimum energy. Initially, the motion trajectory and temperature field of the poly(L-lactic acid) (PLLA) powder during spheroidization were quantitatively assessed and optimized using Stokes’ law and Fourier's principle. Subsequently, the cohesive forces and aggregation kinetics of the polymer chains were calculated using molecular dynamics. Finally, based on these calculations, a phase-field model was constructed to simulate the evolution of the spheroidization rate and deduce the optimal parameters for the process. This precise approach enhances PLLA spheroidization control for laser 3D printing, improves part densification and surface quality, and offers a clean and efficient path for preparing high-quality PLLA spheroidized powder for laser 3D printing.

Influence of Solid-Phase and Melt-Quenching Na3Fe2(PO4)3 Polycrystal Production Technology on Their Structure and Ionic Conductivity

This article studies the influence of solid-phase (type 1 samples) and melt-quenching (type 2 samples) technological modes of obtaining Na3Fe2(PO4)3 polycrystals on their structures and ion-conducting properties. α-Na3Fe2(PO4)3 polycrystals of the 1st type are formed predominantly under an isothermal firing regime, and the synthesis of the 2nd type is carried out under sharp temperature gradient conditions, contributing to the formation of glassy precursors possessing a reactive and deformed structure, in which the crystallization of crystallites occurs faster than in precursors obtained under isothermal firing. The elemental composition of α-Na3Fe2(PO4)3 type 2 polycrystals is maintained within the normal range despite the sharp non-equilibrium thermodynamic conditions of synthesis. The microstructure of the type 1 Na3Fe2(PO4)3 polycrystals is dominated by chaotically arranged crystallites of medium (7–10 μm) and large (15–35 μm) sizes, while the polycrystals of type 2 are characterized by the preferential formation of small (3–4 μm) and medium (7–10 μm) crystallites, causing uniaxial deformations in their structure, which contribute to a partial increase in their symmetry. The advantage of type 2 polycrystals is that they have higher density and conductivity and are synthesized faster than type 1 samples by a factor of 4. The article also considers the issues of crystallization in a solid-phase precursor from the classical point of view, i.e., the process of the formation of small solid-phase nuclei in the metastable phase and their growth to large particles due to association with small crystallites using phase transitions. Possible variants and models of crystallite growth in Na3Fe2(PO4)3 polycrystals, as well as distinctive features of crystallization between two types of samples, are discussed.

Rheology of Ti-6Al-4V alloy under non equilibrium conditions during β forging

During the “β-forging” of Ti-6Al-4V structural aircraft components that follows pre-heating above the β-transus, the skin zone of the blank actually cools down to below the β-transus whilst being deformed, as a result of heat losses towards the atmosphere or the dies. The core areas of the bulkiest sections of the blank, however, can be deformed above the β-transus during the whole processing time. This paper focuses on the development of an innovative rheological model to support the numerical modelling of the forging process, suitable for both the equilibrium conditions above the β-transus and the non-equilibrium conditions below. For that purpose, small-scale hot compression tests were performed with the thermomechanical simulator Gleeble 3500, after pre-heating in the β-field of Ti-6Al-4V at 1100 °C and rapid cooling to the compression temperature under the β-transus, which was varied between 750 °C and 950 °C. In some cases, a lag time -or stabilization time- at constant temperature was introduced between the cooling step and the deformation step. Effects of lag time and deformation temperature on microstructural evolutions and rheological properties of Ti-6Al-4V were investigated. Results show that the lack of stabilization time leads to a significant reduction of the flow stress at low strain. Such a behavior is associated with non-equilibrium thermodynamic conditions at the beginning of deformation and the progress of phase transformation during deformation. Based on that observation, an analytical formulation for the targeted rheological model is proposed. It includes a sub-model for the kinetics of phase transformation derived from the literature.

(Invited) On Non-equilibrium Thermodynamics in Electrochemical Systems

Much of our understanding of physical behavior of materials is based on the concept of equilibrium, which lies at the heart of classical thermodynamics, condensed matter physics, and modern reaction kinetics. If a thermodynamic system is in equilibrium conditions, which is the situation when an energy system (e.g., a fuel cell or a battery) is under open circuit voltage, the surface and bulk of the electrode are only subject to fluctuation of thermodynamic qualities. For the cases that are not at equilibrium, but are close to it, Onsager established linear reciprocal relationships between flux and thermodynamic force for a thermodynamic system in nonequilibrium states. These linear relationships are manifested in transport phenomena, which are non-equilibrium processes, such as ion diffusion and heat conduction.When an electrochemical reaction takes place at an electrode of a fuel cell, electrolyzer, or battery, the thermodynamic system is far away from equilibrium. Therefore, the thermodynamic states of the surface and bulk of an electrode are subject to external thermodynamic forces. As a result, in an active electrode, the electrochemical reaction on the surface causes all thermodynamic variables to change in both the surface and the bulk. In this talk, I will use solid oxide cells and lithium-ion batteries as an example to address three questions related to materials in non-equilibrium thermodynamic states: (i) how do fast kinetics and high current in an operating electrochemical cell affect the thermodynamic states of its material constituents, (ii) whether or not the state of non-equilibrium can remain stable with constant flow of matter and energy, and (iii) what is the origin that governs activity and stability in solid oxide cells?

Features of Structures and Ionic Conductivity of Na3Fe2(PO4)3 Polycrystals Obtained by Solid Phase and Melt Methods

This article investigates the structures and conductive properties of polycrystals of Na3Fe2(PO4)3 obtained by solid-state and melt synthesis methods using concentrated optical radiation. It has been established that in the melt synthesis method, the material is synthesized under significantly non-equilibrium thermodynamic conditions, leading to the creation of deformations in the sample, which contribute to the enhancement of ionic conductivity. Additionally, the synthesis duration is reduced by half. Through a comparative assessment of the structural parameters and conductive properties of these materials, it is demonstrated that polycrystals obtained by the melt method exhibit better texture and higher ionic conductivity. The occurrence of deformations during the synthesis of α-Na3Fe2(PO4)3 under high temperature-gradient conditions indicates the elasticity of the crystalline framework {[Fe2(PO4)]3−}3∞. It is concluded that the non-equilibrium thermodynamic conditions of α-Na3Fe2(PO4)3 synthesis promote the formation of deformations in the crystalline structure of polycrystals, leading to a partial increase in symmetry and ionic conductivity.

Analysis of Low-Frequency Communication of Hypersonic Vehicles in Thermodynamic and Chemical Non-Equilibrium State

A plasma sheath will be developed surrounding a hypersonic vehicle in flight, which can reflect, absorb, and scatter electromagnetic (EM) waves of lower frequencies than its own, resulting in a communication blackout. This paper focuses on knowing how to limit the absorption and reflection of low-frequency EM waves by plasma sheath in a thermodynamic and chemical non-equilibrium state. According to the temperature increment model, the energy of high-power microwave (HPM) irradiation is translated into the temperature increment of heavy particles in plasma. As a result of this modification process, the transmittance of low-frequency EM waves going through the plasma sheath in a certain time frame rises, potentially easing the communication blackout problem.

Emergence of cosmic space with Barrow entropy, in non-equilibrium thermodynamic conditions

Recently, Barrow proposed a modified area–entropy relation S=(A/A0)1+Δ/2, where the exponent Δ, ranges 0≤Δ≤1, by taking account of the quantum gravitational deformation effects to the black hole’s surface. In recent literature, this horizon entropy has been adopted to the cosmological context. Following this, we obtained the law of emergence, which describes the dynamics of the universe, with Barrow entropy in the context of equilibrium thermodynamics (unified first law and Clausius relation). However, when considering Barrow entropy (a non-Bekenstein entropy), an additional entropy generation arises owing to the non-equilibrium thermodynamics. The corresponding field equation bears an effective coupling strength, which connects the geometry with an effective energy–momentum tensor. We derived the law of emergence by using the non-equilibrium description of the thermodynamic principle, which accounts for the addition entropy production term. We compared it with that of the equilibrium description. In addition, we checked the consistency of the modified law in the context of entropy maximization. Interestingly, we found that the non-equilibrium entropy generation rate decreases gradually, and the universe evolves to an equilibrium state of maximum entropy corresponding to the de Sitter epoch.

Biased Symmetry Breaking in the Formation of Intercalated Layered Double Hydroxides: toward Control of Homochiral Supramolecular Assembly.

Homochiral supramolecular assembly (HSA) based on achiral molecules has provided important clues to understand the origin of biological homochirality from the aspect of symmetry breaking. However, planar achiral molecules still face the challenge of forming HSA due to the lack of driving force for twisted stacking, which is a prerequisite for homochirality. Here, with the benefit of the formation of 2D intercalated layered double hydroxide (LDH, host-guest nanomaterials) in vortex motion, planar achiral guest molecules can form the chiral units with spatially asymmetrical structure in the confinement space of LDH. Once the LDH is removed, these chiral units are in a thermodynamic non-equilibrium state, which can be amplified to HSA by self-replicating. Especially, the homochiral bias can be predicted in advance by controlling the vortex direction. Therefore, this study breaks the bottleneck of complicated molecular design and provides a new technology to achieve HSA made of planar achiral molecules with definite handedness.

The Thermo-field Dynamics Method for Electron with Two-mode Electromagnetic Field

The quick progress in quantum entanglement research allows us not one to study quantum systems down to N-bodies but also to take a new look at these systems in different branches of physics; particularly the statistical thermodynamics where the application of the thermo-field dynamics (<I>TFD</I>) method to the investigation of entanglement is fruitful. Because the traditional methods based on the identification of a specific parameter show their limit. The process using (<I>TFD</I>) facilitates the understanding of entanglement because it focuses directly on the eigenstate of the system and it is useful in the equilibrium and the non-equilibrium states also. In this context, the (<I>TFD</I>) method is used in this paper to analyze entanglement of an electron interacting with a two-mode electromagnetic field assimilated to an electron with two harmonic oscillators. Entanglement entropies are derived between concerned, not concerned harmonic oscillator and electron compute when the system is in a thermodynamic equilibrium and non-equilibrium state. For the equilibrium case, an increase in the number of particles per unit volume increases the quantum entanglement consequently entanglement appears more important for the couple oscillator-electron than the one electron, this trend is reversed for the non-equilibrium case. By respecting the entanglement parameters, such results allow us to know the relative equilibrium state of the overall system.

Explosive Processes in Permafrost as a Result of the Development of Local Gas-Saturated Fluid-Dynamic Geosystems

The relevance of studying explosive processes in permafrost lies in the prospect of gas production from small gas-saturated zones in the subsurface; the influx of significant amounts of greenhouse gases from frozen soils creates a threat to infrastructure. The purpose of this article is to reveal the general patterns of frozen soils’ transformation in local zones of natural explosions. The greatest volume of information about the processes preceding the formation of gas-emission craters can be obtained by studying the deformations of the cryogenic structure of soil. The typification of the elements of the cryogenic structures of frozen soils that form the walls of various gas-emission craters was carried out. Structural and morphological analyses were used as a methodological basis for studying gas-emission craters. This method involves a set of operations that establishes links between the cryogenic structure of the crater walls and the morphologies of their surfaces. In this study, it is concluded that gas-emission craters are the result of the self-development of local gas-dynamic geosystems that are in a non-equilibrium thermodynamic state with respect to the enclosing permafrost.

Determining depletion interactions by contracting forces.

Depletion forces are fundamental for determining the phase behavior of a vast number of materials and colloidal dispersions and have been used for the manipulation of in- and out-of-equilibrium thermodynamic states. The entropic nature of depletion forces is well understood; however, most theoretical approaches, and also molecular simulations, work quantitatively at moderate size ratios in much diluted systems since large size asymmetries and high particle concentrations are difficult to deal with. The existing approaches for integrating out the degrees of freedom of the depletant species may fail under these extreme physical conditions. Thus, the main goal of this contribution is to introduce a general physical formulation for obtaining the depletion forces even in those cases where the concentration of all species is relevant. We show that the contraction of the bare forces uniquely determines depletion interactions. Our formulation is tested by studying depletion forces in binary and ternary colloidal mixtures. We report here results for dense systems with total packing fractions of 45% and 55%. Our results open up the possibility of finding an efficient route to determine effective interactions at a finite concentration, even under non-equilibrium thermodynamic conditions.

On the Possibility of the Effective Isotope-Selective Infrared Dissociation of 235UF6 Molecules Vibrationally Excited by Bichromatic Laser Radiation

Using the spectroscopic data on the 235UF6 and 238UF6 molecules and on the lasing frequencies of CF4 and para-H2 lasers and recent results, a method has been proposed to increase the efficiency of the isotope-selective infrared laser dissociation of 235UF6 molecules under nonequilibrium thermodynamic shock conditions. The method involves two processes: (i) the resonant multiphoton excitation of 235UF6 molecules to the 3ν3 or 2ν3 vibrational states by the bichromatic infrared radiation of two CF4 or para-H2 lasers and (ii) the irradiation of 235UF6 molecules with SF6 molecules serving as sensitizers resonantly absorbing the radiation of these lasers. The essence of the method has been described. Schemes and parameters for isotope-selective dissociation of 235UF6 molecules using this method has been presented.

Vibrational excitation cross sections for non-equilibrium nitric oxide-containing plasma

A full set of vibrationally-resolved cross sections for electron impact excitation of NO(X2Π, v) molecules is calculated from ab initio molecular dynamics, in the framework of the local-complex-potential approach. Electron–vibration energy exchanges in non-equilibrium thermodynamic conditions are studied from a state-to-state model accounting for all electron impact excitation and de-excitation processes of the nitric oxide vibration manifold, and it is shown that the calculated vibration relaxation times are in good agreement with the experimental data. The new vibrational excitation cross sections are used in a complete electron impact cross section set in order to obtain non-equilibrium electron energy distributions functions and to calculate electron transport parameters in NO. It is verified that the new cross sections bring a significant improvement between simulations and experimental swarm data, providing an additional validation of the calculations, when used within the complete set of cross sections investigated in this work.

Thermal Shear Waves Induced in Mesoscopic Liquids at Low Frequency Mechanical Deformation

Abstract We show that a confined viscous liquid emits a dynamic thermal response upon applying a low frequency (∼1 Hz) shear excitation. Hot and cold thermal waves are observed in situ at atmospheric pressure and room temperature, in a viscous liquid (polypropylene glycol) at various thicknesses ranging from 100 µm up to 340 µm, upon applying a mechanical oscillatory shear strain. The observed thermal effects, synchronous with the mechanical excitation, are inconsistent with a viscous behaviour. It indicates that mesoscopic liquids are able to (partly) convert mechanical shear energy in non-equilibrium thermodynamic states. This effect called thermo-elasticity is well known in solid materials. The observation of a thermal coupling to the mechanical shear deformation reinforces the assumption of elastically correlated liquid molecules. The amplitude of the thermo-elastic waves increases linearly by increasing the shear strain amplitude up to a transition to a non-linear thermal behavior, similar to a transition from an elastic to plastic regime. The thermo-elastic effects do not give rise to any change in stress measurements and thus the dynamic thermal analysis provides unique information about dynamic liquid properties.

Host‐Fueled Transient Supramolecular Hydrogels

AbstractInspired by the dissipative assembly in biological systems, transient hydrogels based on supramolecular interactions have been developed that are under thermodynamic nonequilibrium states. Host–guest interactions possess excellent properties including high selectivity and adjustable association constants, which are beneficial for controlling the properties and behaviors of transient colloidal materials. In this work, a host‐fueled transient supramolecular hydrogel system is reported. The hydrogels based on host–guest interactions are formed by addition of a chemical fuel, α‐cyclodextrin (α‐CD), to the aqueous solutions containing Pluronic F127 and α‐amylase. Meanwhile, as the host molecule of α‐CD consumes, the hydrogel networks start to collapse. The lifetime of the transient supramolecular hydrogels can be precisely controlled by adjusting the temperature and hydrogel composition, and repeated sol‐to‐gel‐to‐sol transitions can be realized by refueling the system with α‐CD. This study provides a new approach to regulate the nonequilibrium host–guest inclusion system by fueling it with host molecules.

Analyses of Multiphysical Model of Electromagnetic and Fluid in Thermodynamic Equilibrium and Chemical Nonequilibrium State

During the flight of a hypersonic vehicle, a plasma sheath will be produced around the vehicle due to the effect of the shock layer. Because the plasma sheath will absorb, reflect, and scatter electromagnetic waves, which causes the communication signal to be attenuated or even interrupted, forming a communication “blackout.” In this article, the plasma sheath is illuminated by a high-power microwave (HPM) when the hypersonic vehicle is in the state of thermodynamic equilibrium and chemical nonequilibrium. Thus, the parameters of the plasma sheath change because of absorbing the energy of the HPM and then affect the electromagnetic characteristics of the plasma sheath. Aiming at the interaction between the HPM and the plasma sheath, we propose a multiphysics coupling model of fluid field and electromagnetic field, which provides a way of thinking for the interaction of electromagnetic and fluid coupling. Furthermore, through this multiphysics coupling method, it is found that the HPM illuminates into the plasma sheath, the ability of low-frequency electromagnetic waves to pass through the plasma sheath will be improved within a specific time window, which provides a possibility to enhance the communication blackout problem. Since the primary purpose of this article is to reveal the multiphysics field method and its related phenomena, both theoretical derivations and numerical examples are only presented in the 2-D space.

A self-consistent method for solving ion diffusion and mobility coefficients

A self-consistent method for computation and testing of transport coefficients in low pressure radio frequency plasma discharges is detailed by comparing the experimental fitting formula and previous results gained from the Langevin expression. In this paper, for the first time, we apply the Chapman–Enskog method for calculating transport coefficients of ions to a weakly ionized plasma which is laid in a thermodynamic non-equilibrium and chemical non-equilibrium state. The ion diffusion coefficient is obtained by using the Chapman–Enskog method expanded to the second order approximation. The corresponding ion mobility coefficient is deduced from Einstein's relation. A two-dimensional axisymmetric fluid model of capacitively coupled plasmas is employed to determine the plasma composition. Moreover, the comparison of plasma physical characteristics using ion transport coefficients calculated by the Chapman–Enskog method with those derived from theoretical and experimental methods is also investigated. The results show that the ion transport coefficients obtained by the Chapman–Enskog method and their effect on plasma physical quantities are in good agreement with the experimental measurement and theoretical expression. Furthermore, the results indicate that the set of exponential and Morse potentials is more reasonable for the ion–neutral particles' interaction.

Ultra-low temperature reactive flash sintering synthesis of high-enthalpy and high-entropy Ca0.2Co0.2Ni0.2Cu0.2Zn0.2O oxide ceramics

High-enthalpy and high-entropy Ca0.2Co0.2Ni0.2Cu0.2Zn0.2O oxides was synthesized via reactive flash sintering (RFS) at room temperature with electric field of 60 V/cm and current density of 300 mA/mm2. The estimated average temperature of the sample at the steady stage was 1060 °C during RFS, which was much lower than the previous prediction. It speculated that the applied electric field may cause a non-equilibrium thermodynamic state and the fast phase transition was occurred at lower temperature with applied electric field.

Improving sintering kinetics and compositional homogeneity of Inconel 625 superalloy open-cell foams made by suspension impregnation method

Open-cell Inconel 625 superalloy foams were prepared by suspension impregnation method which involves replication of pure nickel foam ligaments with a mixed powder suspension and subsequent heat treatments. The objective of the present study is to find a suitable method ensuring complete densification of the superalloy foam ligaments without using low-melting additives and achieving uniform chemical composition at moderate sintering temperatures. Foams prepared using the above methodology were evaluated for the microstructure and compositional variation across the foam ligaments by scanning electron microscopy (SEM) coupled with electron dispersive spectroscopy (EDS). Quasi-static compressive properties of the foams were evaluated. It is shown that if elemental powders of Cr, Mo and Ni are used as additives to the superalloy powder suspension, high ligament density with uniform chemical composition conforming to the Inconel 625 specification is achieved at moderate sintering temperatures. These results are attributed to the formation of low melting eutectics and to acceleration of the diffusion kinetics due to the non-equilibrium thermodynamic conditions created by large compositional gradients in the presence of elemental powders.

A mathematical model of a vibrator with an axial striker mechanism

To be operated effectively by the production and injection wells, the nature of oil reservoir production is largely determined. The efficient operation of wells depends on geological and technological factors. This refers to their exploitation with oil output equal to the potential capabilities of the reservoir when it is fully served by the filtration process. The bottom-hole zone (BHZ) is in a non-equilibrium thermodynamic state of energy and mass exchange with the well and the reservoir. The contamination of the bottom-hole zone has a significant impact on the effectiveness of wells.