Equilibrium Thermodynamic Approach Research Articles

Thermodynamic Analysis of Anomalous Shape of Stress-Strain Curves for Shape Memory Alloys.

In some shape-memory single crystals the stress-strain (σ~ε) curves, belonging to stress induced martensitic transformations from austenite to martensite at fixed temperature, instead of being the usual slightly increasing function or horizontal, have an overall negative slope with sudden stress drops in it. We discuss this phenomenon by using a local equilibrium thermodynamic approach and analysing the sign of the second derivative of the difference of the Gibbs free energy. We show that, considering also the possible nucleation and growth of two martensite structural modifications/variants, the stress-strain loops can be unstable. This means that the overall slope of the uploading branch of the stress-strain curve can be negative for smooth transformation if the second martensite, which is more stable with larger transformation strain, is the final product. We also show that local stress-drops on the stress-strain curve can appear if the nucleation of the second martensite is difficult, and the presence of such local stress-drops alone can also result in an overall negative slope of the stress-strain curves. It is illustrated that the increase of the temperature of the thermal recovery during burst-like transition is a measure of the change of the nucleation energy: the more stable martensite has larger nucleation energy.

Why does thermomagnetic resonance affect cancer growth? A non-equilibrium thermophysical approach

Recently, the low frequency thermomagnetic effects on cancer cells have been analysed, both theoretically and experimentally. They have been explained by introducing an equilibrium thermodynamic approach. But, in this context, two related open problems have been highlighted: (1) Does there exist a magnetic interaction or do there exist any other processes? (2) Do there exist also thermal effects? Here, we introduce a non-equilibrium thermodynamic approach in order to address an answer to these questions. The results obtained point out that: (a) the effect produced by the electromagnetic wave is just a consequence of the interaction of the magnetic component of the electromagnetic wave with the biological matter; (b) the interaction of the electromagnetic wave causes also thermal effects, but related to heat transfer, even if there have been applied low frequency electromagnetic waves; (c) the presence of the magnetic field generates a symmetry breaking in the Onsager’s coefficients, with a related perturbation of the cancer stationary state.

Comments on equilibrium thermodynamic approach to ferroic hysteresis

The equilibrium thermodynamic approach to ferroic hysteresis was recalled firstly, especially according to the ferroelectric case. Then based on the uniqueness of equilibrium state, it was showed that a ferroic hysteresis loop is composed of stationary states but not equilibrium ones, especially according to the ferromagnetic case. So, it was concluded that the equilibrium thermodynamic approach to ferroic hysteresis is not reliable. Life-force should be bestowed on the domain structure dynamic approach and the non-equilibrium thermodynamic approach.

On evaluation of electric conductivity by mean of non equilibrium thermodynamic approach with internal variables. An application to human erythrocyte suspension for metabolic characterizations

In this paper we will approach a new method to obtain electrical conductivity by means of dielectric measurements. After a remark on non-equilibrium thermodynamics with internal variables formulated by Kluitenberg, we introduce complex conductivity and the relationship with the complex dielectric constant. Taking into account the dielectric model by us introduced we determine the real and imaginary part of conductivity as function of the frequency of perturbation. Also we determine phenomenological and state coefficients that lead to the determination of the two components in which is splitted the polarization, and to the entropy production due to electrical conductivity. These results are applied to an human erythrocyte suspension for metabolic deductions.

Entropy change and phase transitions in an expanding Universe

AbstractThe work compiles a correlated study of a gravitational quasi equilibrium thermodynamic approach for establishing and signifying a unique behavior of the cosmological entropy and phase transitions in an expanding Universe. On the basis of prescribed boundary conditions for the cluster temperature a relation for the intra‐cluster medium (ICM) of galaxy clusters has been derived. A more productive and signifying approach of the correlation functions used for galaxy clustering phenomena shows a unique behavior of the entropy change where a phenomenon known as the gravitational phase transition occurs. This unique behavior occurs with a symmetry breaking from mild clustering to low clustering and from mild clustering to high clustering which differs from a normal symmetry breaking in material sciences. We also derive results for the specific latent heat associated with the phase transitions of 3.20 Tc and 0.55 Tc for the mildly clustered phase to the low clustered phase and from the mildly clustered phase to the highly clustered phase, respectively. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Computer reconstruction of the physicochemical conditions of sulfide formation for the Krasnov and Ashadze hydrothermal systems (Mid-Atlantic Ridge)

Computer-based reconstruction of the physicochemical conditions of formation of the Krasnov (16° N) and Ashadze (13° N) submarine systems in the Mid-Atlantic Ridge (MAR) has been performed using the equilibrium-thermodynamic approach to study samples from these sites. In the first case, a sphalerite-pyrite-barite association was considered, and in the second case, a sphalerite-pyrite association. In the modeling conducted, the composition of the sphalerite solid solution corresponding to the nonideal mixing of ZnS and FeS was used as a correlation parameter with the total composition of the Fe-Zn-Ba-S-H2O-NaCl-HCl hydrothermal system depending on temperature (200-300°C) and a given pressure of 100bar. The calculation results predict that at an iron content of 0.17-0.36wt.% in sphalerite, the minimum formation temperatures of the equilibrium sphalerite-pyrite-barite association should correspond to the interval of 280-300°C (Krasnov site). As the iron content in sphalerite increases to 4.15-13.28wt.%, the occurrence of barite in the systems studied becomes impossible and the formation temperatures of the sphalerite-pyrite association become equal to or higher than 300°C (Ashadze site).

Prediction and Control of Steam Accumulation

Steam accumulators are applied as buffers between steam generators and consumers in cases of different steam production and consumption rates. The application of the steam accumulator saves energy, reduces pressure fluctuations, and prevents aging of tubes and pressurized vessels in steam generators. In this paper, modes of the steam accumulator operation are analyzed and the general design of the steam accumulator control system is defined. Equilibrium and nonequilibrium thermodynamic models of the steam accumulator are presented with the aim of predicting the steam accumulator capacity and as support to the design of the control system. The equilibrium model is based on the mass and energy balance equations of the total water and steam content in the accumulator, while the nonequilibrium model is based on the mass and energy balance equations for each phase and closure laws of nonequilibrium evaporation and condensation rates. The steam accumulator pressure transients are simulated for constant steam charging and discharging flow rates, and the influence of the nonequilibrium condensation and evaporation rates on the steam accumulator capacity is shown. It is concluded that the commonly used equilibrium thermodynamic approach to the steam accumulator design does not provide accurate results in cases of rapid charging and discharging transients; therefore, there is a need for the application of the nonequilibrium approach.

Nanosizing as a way to enhanced solubility of transition metals in ZnO

The solubility of nickel and cobalt oxides in ZnO nanoparticles was explored using the equilibrium thermodynamic approach. The equilibrium conditions were derived for the binary system ZnO–TMO (TM = Ni or Co) consists of two different spherical nanoparticles, one comprising the wurtzite (Zn1−x TM x )O(wz) solid solution and the second the rocksalt (TM1−x Zn x )O(rs) solid solutions. Thermodynamic parameters for both phases were evaluated from bulk phase diagrams and the surface energy terms were included. Calculations of phase boundaries between the wurtzite and the rocksalt solid solutions reveal significant rise of the TM content in wurtzite phase. At the same time, the solubility of ZnO in rocksalt phase decreases. This behavior is more obvious for nanoparticles less than 5 nm in diameter and becomes more evident with increasing temperature. These results are in qualitative agreement with published experimental data.

Thermodynamics of quantum jump trajectories in systems driven by classical fluctuations

The large-deviation method can be used to study the measurement trajectories of open quantum systems. For optical arrangements this formalism allows to describe the long time properties of the (nonequilibrium) photon counting statistics in the context of a (equilibrium) thermodynamic approach defined in terms of dynamical phases and transitions between them in the trajectory space [J. P. Garrahan and I. Lesanovsky, Phys. Rev. Lett. 104, 160601 (2010)]. In this paper, we study the thermodynamic approach for fluorescent systems coupled to complex reservoirs that induce stochastic fluctuations in their dynamical parameters. In a fast modulation limit the thermodynamics corresponds to that of a Markovian two-level system. In a slow modulation limit, the thermodynamic properties are equivalent to those of a finite system that in an infinite-size limit is characterized by a first-order transition. The dynamical phases correspond to different intensity regimes, while the size of the system is measured by the transition rate of the bath fluctuations. As a function of a dimensionless intensive variable, the first and second derivatives of the thermodynamic potential develop an abrupt change and a narrow peak, respectively. Their scaling properties are consistent with a double-Gaussian probability distribution of the associated extensive variable.

Thermodynamic analysis of adsorption process at a non-equilibrium steady state

By using the non-equilibrium thermodynamic approach, the possibility of the existence of a steady state for non-equilibrium adsorption with a temperature difference between body gas and adsorbed gas was confirmed and the steady state was determined. The chemical potential difference between body gas and adsorbed gas was obtained and equations for evaluating the adsorption entropy and the isosteric heat of adsorption were derived. The changes of the adsorption entropy and the isosteric heat of adsorption at the non-equilibrium steady state relative to those at the equilibrium state were calculated and the results were compared with those obtained using the traditional equilibrium thermodynamic method. The comparison suggests that the changes of the adsorption entropy and the isosteric heat of adsorption obtained using the non-equilibrium thermodynamic approach are related with not only temperature but also adsorptive state, while those obtained using the equilibrium thermodynamic method are only a function of temperature. The main reason is that the present study treats the adsorption and gas temperature change as an integrated process and considers their interaction, whereas the equilibrium thermodynamic approach separates the adsorption and gas temperature change as two independent processes and neglects their interaction.

Ice slurry crystallization based on kinetic phase-change modeling

Most crystallization models for ice slurries are based on the equilibrium thermodynamic approach, an assumption that is not made a priori here. We present results of simulations grounded on classical nucleation theory and crystal growth included in global Nakamura-type kinetics coupled with the one-dimensional nonlinear heat equation, another way to model the phase change. The work focuses on ice slurry crystallization using kinetic tools integrating the temperature glide for mixtures (i.e., the solid–liquid equilibrium temperature Tf depends on the residual fluid’s solute concentration) without any equilibrium assumption. The heat-transfer phenomena in the experimental device are first determined, and then the parameters of kinetic function of crystallization are identified for pure water samples and then for 15 wt% monopropylene glycol (MPG) – water mixtures. An inverse method is implemented with a genetic algorithm to determine the kinetic parameters.

Effects of cholesterol on thermal stability of discoidal high density lipoproteins

Reverse cholesterol transport in plasma involves variations in HDL cholesterol concentration. To understand physicochemical and functional implications of such variations, we analyzed stability of reconstituted HDL containing human apolipoproteins (apoA-I, apoA-II, or apoC-I), phosphatidylcholines varying in chain length (12-18 carbons) and unsaturation (0 or 1), and 0-35 mol% cholesterol. Lipoprotein heat denaturation was monitored by circular dichroism for protein unfolding/dissociation and by light scattering for particle fusion. We found that cholesterol stabilizes relatively unstable complexes; for example, incorporation of 10-30 mol% cholesterol in apoC-I:dimyristoyl phosphatidylcholine complexes increased their kinetic stability by deltaDeltaG* congruent with 1 kcal/mol. In more stable complexes containing larger proteins and/or longer-chain lipids, incorporation of 10% cholesterol did not significantly alter the disk stability; however, 15% or more cholesterol destabilized the apoA-I-containing complexes and led to vesicle formation. Thus, cholesterol tends to stabilize less stable lipoproteins, apparently by enhancing favorable packing interactions, but in more stable lipoproteins, where such interactions are already highly optimized, the stabilizing effect of cholesterol decreases and, eventually, becomes destabilizing. These results help uncouple the functional roles of particle stability and chain fluidity and suggest that structural disorder in HDL surface, rather than chain fluidity, is an important physicochemical determinant of HDL function.

Reactive Transport Modeling of Radionuclide Source-Terms in an Underground Spent Fuel Disposal

ABSTRACTThe reactive transport model HYTEC was used to simulate the migration over 100,000 years of cesium, americium and uranium released from spent fuel packages in the near-field components of an underground stiff clay disposal site. A global equilibrium thermodynamic approach including kinetic control of the spent fuel pellets was used with instantaneous release fractions and congruent dissolutions of the rim and the core zones. A failure scenario of the waste package after 10,000 years was considered with magnetite as the main corrosion product. The retention properties of magnetite and the different effects of bentonite and cementitious backfill materials were specifically analysed.

A THERMODYNAMIC APPROACH TO FIELD-INDUCED STRESSES IN ELECTRO- AND MAGNETOACTIVE COMPOSITES

An equilibrium thermodynamic approach is employed to derive a continuum-level expression for the field-induced stress in uniaxial anisotropic materials, such as electro- and magnetorheological suspensions. This model introduces new electro- and magnetostriction coefficients, which are material parameters that describe the strain dependence of the dielectric and permeability tensors as well as the field-induced stresses. An idealized microscopic model illustrates the relationships between microscopic parameters and the macroscopic magnetostriction coefficients. The model is used to determine the stresses in common applications; predictions from the continuum approach agree with direct calculations of the normal stress and static shear modulus of magnetorheological suspensions.

A continuum approach to electrorheology

An equilibrium thermodynamic approach is employed to derive a continuum-level expression for the electric field-induced stress in uniaxial anisotropic materials. Although this model is developed specifically to describe electrorheological and electrostrictive behavior of suspensions, it also applies to other uniaxial materials such as nonpolar nematic liquid crystals, biaxially oriented polymer films, and paper. This model introduces new electrostriction coefficients, which are material parameters that describe the strain dependence of the dielectric tensor as well as the field-induced stresses. An experimental technique for measuring the electrostriction parameters is outlined. An idealized microscopic model is presented to illustrate the relationships between microscopic parameters and the macroscopic electrostriction coefficients. The model is used to determine the stresses in common applications; predictions from the continuum approach agree with direct calculations from a microscopic approach of the normal stress and static shear modulus of electrorheological suspensions.

Aluminium speciation variations in an acidic upland stream draining the Hafren spruce forest, Plynlimon, Mid-Wales

The speciation of aluminium in an acidic stream, draining a spruce plantation-forest in Mid-Wales, is examined using an established model based on an equilibrium thermodynamic approach. Trivalent aluminium and aluminium complexes with fluoride, with dissolved organic matter and with silica were abundant: aluminium hydroxy-fluorides and sulphates were much less so. There is a large scatter in the results, primarily due to variations in stream water chemistry at a given pH, rather than to an effect of temperature. It is concluded that aluminium silica complexes can be an important part of the total dissolved aluminium concentration: at pHs > 5, they comprise typically 20% of the total dissolved aluminium in the stream water.

Conversion dependent morphology predictions for composite emulsion polymers: 1. Synthetic latices

Phase structure develops within composite latex particles during the polymerization process and is potentially dependent upon both the latex recipe and the polymerization process characteristics. An equilibrium thermodynamic approach is presented to predict the particle morphology as a function of the extent of conversion of a seed latex polymerization reaction. The discussion highlights the role of the monomer as it influences the phase compositions and interfacial tensions throughout the polymerization. It is found that a number of different particle morphologies possess nearly the same total interfacial energy throughout a significant portion of the polymerization reaction and that it is quite likely that occluded structures will form in addition to the more fully phase-separated structures, such as core-shell and hemispheres. Detailed methods to predict the probabilities of forming a variety of different morphologies are presented.

Solidification of Highly Undercooled Silicon: Bulk Nucleation and Amorphous Phase Formation

ABSTRACTRecent experimental and theoretical work suggests that bulk nucleation occurs in highly undercooled liquid silicon formed by the pulsed laser melting of amorphous layers. In this paper we discuss the dynamics of solidification of undercooled liquid silicon in terms of results from melting model calculations and from the theory of homogeneous bulk nucleation. The relationship between the occurrence of bulk nucleation and the ability to induce a liquid-to-amorphous phase transition by large undercoolings of the liquid is considered. It is concluded that the observed liquid-toamorphous transition in silicon cannot be explained by an equilibrium thermodynamic approach.

Temperature dependence of the magnetization for a random-uniaxial-anisotropy amorphous ferromagnetic material

An equilibrium thermodynamic approach is used to calculate the temperature dependence of the magnetization for a random-anisotropy amorphous ferromagnetic material. The model assumes a single "lattice" and a classical mean-field theory calculation is done using the method of steepest descents. Several anisotropy distributions are considered in addition to a completely isotropic one. It is shown that the inclusion of texture causes a marked change in the magnetization versus temperature curve and that the magnetization is also sharply dependent on the angle between the applied magnetic field and the texture direction. The several resultant curves and a modified curve for a two-"sublattice" model are compared with each other and with experimental data for Tb${\mathrm{Fe}}_{2}$.