Ionic Heat Research Articles

Mean-field potential calculations of high-pressure equation of state for BeO

A systematic study of the Hugoniot equation of state, phase transition, and the other thermodynamic properties including the Hugoniot temperature, the electronic and ionic heat capacities, and the Grüneisen parameter for shock-compressed BeO, has been carried out by calculating the total free energy. The method of calculations combines first-principles treatment for 0 K and finite-T electronic contribution and the mean-field-potential approach for the vibrational contribution of the lattice ion to the total energy. Our calculated Hugoniot is in good agreement with the experimental data.

Classical Transport in a Plasma

An ideal plasma of electrons and a single species of ions in the low collisionality limit subject to an almost straight magnetic field is considered. In such conditions, the linear theory of transport determines the 3 × 1 matrix of dissipative fluxes [hat]Jr namely, the electric current, the electronic heat flux and the ionic heat flux, in terms of a 3 × 1 matrix of thermodynamic forces [hat]X combining the electric field with the gradients of the densities and of the temperatures. The classical transport coefficients are the components of the 3 × 3 matrix of tensors [hat]Lrs of the linear flux-force relations [hat]Jr = [summation]s=19 [hat]Lrs[hat]X. The theory is developed in the framework of the statistical mechanics of charged particles starting from the Landau kinetic equation.

Thermal Radiation and Effects on Transport Processes in Solid Oxide Fuel Cells

The major processes significant for solid oxide fuel cell (SOFC) characteristics are species transport, electrochemical reactions, electronic and ionic transport, heat transfer, and temperature distribution. Of particular significance is an accurate determination of the temperature distribution because material properties, chemical kinetics, and transport properties depend heavily on the temperature. Thermal radiation may play an important role because of the high operating temperature. The present work concerns a review of thermal radiation and effects on heat transfer and gas flow modeling developments in the SOFCs. The different models are compared in terms of cell designs, flow regimes, thermal sources considered, boundary conditions used, and whether the participating gases were concerned in the models. Some useful remarks and conclusions are drawn.

Three-dimensional, single-phase, non-isothermal CFD model of a PEM fuel cell

A comprehensive, three-dimensional analysis of a polymer electrolyte membrane (PEM) fuel cell has been developed to study the performance of this device under different operational conditions. This steady-state analysis is single-phase and non-isothermal. A commercial computational fluid dynamics (CFD) program provided a numerical platform for solving the conservation equations for species, energy, charge, mass and momentum. Different boundary conditions were added to a computational domain to simulate single channel PEM fuel cell. The electrochemistry involved in this model was added by a set of user-defined subroutines that feature: electrochemical reactions, electric and ionic charge and heat generation. The calculations were then solved by an iterative method following an adapted computational procedure. The results were validated with other computational models and experimental data. These show a noticeable non-uniform distribution of the current density across the catalyst layer (CL) at different operational conditions. The results emphasize on the differences of anodic and cathodic activation overpotentials, the oxygen transport limitations and the ohmic losses distributions of both proton and electric overpotentials.

The ionic Seebeck effect and heat of cation transfer in Cu2−δSe superionic conductors

The ionic Seebeck coefficients of Cu2−δSe superionic conductors are measured in the temperature range 340–380°C. The data obtained are used to determine the heat of transfer Q i of copper ions as a function of the degree of nonstoichiometry and the temperature. The heat of transfer of copper cations increases from 0.19 to 0.22 eV as the degree of nonstoichiometry δ increases from 0.015 to 0.050. It is noted that the heat of transfer Q i tends to increase with an increase in the temperature. Assumptions regarding the specific features of the cation diffusion in the Cu2−δSe superionic conductors are made from the observed closeness of the heat of transfer and the activation energy for ionic conduction.

Transport processes in magnetically confined plasmas in the nonlinear regime

A field theory approach to transport phenomena in magnetically confined plasmas is presented. The thermodynamic field theory (TFT), previously developed for treating the generic thermodynamic system out of equilibrium, is applied to plasmas physics. Transport phenomena are treated here as the effect of the field linking the thermodynamic forces with their conjugate flows combined with statistical mechanics. In particular, the Classical and the Pfirsch-Schluter regimes are analyzed by solving the thermodynamic field equations of the TFT in the weak-field approximation. We found that, the TFT does not correct the expressions of the ionic heat fluxes evaluated by the neoclassical theory in these two regimes. On the other hand, the fluxes of matter and electronic energy (heat flow) is further enhanced in the nonlinear Classical and Pfirsch-Schluter regimes. These results seem to be in line with the experimental observations. The complete set of the electronic and ionic transport equations in the nonlinear Banana regime, is also reported. A paper showing the comparison between our theoretic results and the experimental observations in the JET machine is currently in preparation.

Two-photon excitation of low-lying electronic quadrupole states in atomic clusters

A simple scheme of population and detection of low-lying electronic quadrupole modes in free small deformed metal clusters is proposed. The scheme is analyzed in terms of the time-dependent local density approximation calculations. As a test case, the deformed cluster $\mathrm{Na}_{11}{}^{+}$ is considered. Long-living quadrupole oscillations are generated via resonant two-photon (two-dipole) excitation and then detected through the appearance of satellites in the photoelectron spectra generated by a probe pulse. Femtosecond pump and probe pulses with intensities $I=2\ifmmode\times\else\texttimes\fi{}{10}^{10}--2\ifmmode\times\else\texttimes\fi{}{10}^{11}\phantom{\rule{0.3em}{0ex}}\mathrm{W}∕{\mathrm{cm}}^{2}$ and pulse duration $T=200--500\phantom{\rule{0.3em}{0ex}}\mathrm{fs}$ are found to be optimal. The modes of interest are dominated by a single electron-hole pair and so their energies, being combined with the photoelectron data for hole states, allow us to gather full mean-field spectra of valence electrons near the Fermi energy. Besides, the scheme allows us to estimate the lifetime of electron-hole pairs and hence the relaxation time of electronic energy into ionic heat.

Hermitian Moment Approach to the Classical Transport Properties of a Weakly Coupled Magnetized Plasma

A complete description of a system in equilibrium is provided by the Grand Canonical Distribution. But, systems are generally not in statistical equilibrium. We shall consider the case of an ideal gaz of charged particles. The linear theory of transport determines the 3 × 1 matrix of dissipative fluxes [hat]Jr namely, the electric current and the electronic and ionic heat fluxes, in terms of a 3 × 1 matrix of thermodynamic forces [hat]X defined by the electric field and the gradient of the densities and temperatures. The components of the 3 × 3 matrix of tensors [hat]Lrs of the linear flux-force relations [hat]Jr = [summation]s=19[hat]Lrs[hat]X define the set of transport coefficients. They are evaluated for an ion-electron magnetized plasma in the framework of the statistical mechanics of charged particles starting from the Landau kinetic equation.

The Fouling Behaviour of Sodium Aluminosilicate Polytypes in High Ionic Strength Caustic Media Heat Exchangers

AbstractSodium aluminosilicate (SAS) scale formation, simulating high ionic strength caustic media process heat exchanger fouling, has been investigated for a temperature range of 30–240°C. Findings from several studies performed with a variety of liquor, substrate‐type and agitation conditions show that SAS polytypes; i.e. amorphous, zeolite A, sodalite and cancrinite phases, differing in thermodynamic stability and kinetic behaviour may deposit. The polytypes formed and subsequent transformations to more thermodynamically stable phases are strongly dependent on liquor composition, temperature and time. The scale deposition process is substrate‐ mediated heterogeneous nucleation and particle growth (precipitation foulin&, which may be accompanied by bulk liquor‐nucleated solids adsorption (particulate fouling) at suficiently high supersaturations. Liquor seeding with stable SAS solid phases is found to be efective in mitigating fouling. The precipitation fouling behaviour is principally determined by the clystallo‐chemical nature of the SAS polytype and the solution conditions. The substrate (mild steel, 316 stainless steel, nickel and tef2on) surface physico‐chemical structure has a signlficant impact on the scale particle morphology and layer structure, particularly at high temperatures.

A new ionic liquid: 2-hydroxy ethylammonium formate

A new ionic liquid (2-hydroxyethylammonium formate), with extremely low melting temperature (−82 °C), is presented. This ionic liquid of equimolar mixture of formic acid and 2-hydroxyethylamine shows reasonably high at ionic conductivity (3.3 mS cm −1) room temperature and heat stability up to 150 °C. Both 1H-NMR and FT-IR spectra establish its simple salt structure. Due to its high polarity, the ionic liquid is able to dissolve many inorganic salts. Also some insoluble polymers such as polyaniline and polypyrrole are highly soluble in the ionic liquid. In the study, the physical characteristics of the ionic liquid, such as conductivity, viscosity and solvation abilities have been investigated.

Hermitian Moment Approach to the Classical Transport Properties of a Weakly Coupled Magnetized Plasma

A complete description of a system in equilibrium is provided by the Grand Canonical Distribution. But, systems are generally not in statistical equilibrium. We shall consider the case of an ideal gaz of charged particles. The linear theory of transport determines the 3 × 1 matrix of dissipative fluxes [circumflex]Jr namely, the electric current and the electronic and ionic heat fluxes, in terms of a 3 × 1 matrix of thermodynamic forces [circumflex]X defined by the electric field and the gradient of the densities and temperatures. The components of the 3 × 3 matrix of tensors [circumflex]Lrs of the linear flux-force relations [circumflex]Jr = [summation]s=19[circumflex]Lrs[circumflex]X define the set of transport coefficients. They are evaluated for an ion-electron magnetized plasma in the framework of the statistical mechanics of charged particles starting from the Landau kinetic equation.

Thermodynamics of tin clusters

We report the results of detailed thermodynamic investigations of the Sn$_{20}$ cluster using density-functional molecular dynamics. These simulations have been performed over a temperature range of 150 to 3000 K, with a total simulation time of order 1 ns. The prolate ground state and low-lying isomers consist of two tricapped trigonal prism (TTP) units stacked end to end. The ionic specific heat, calculated via a multihistogram fit, shows a small peak around 500 K and a shoulder around 850 K. The main peak occurs around 1200 K, about 700 K higher than the bulk melting temperature, but significantly lower than that for Sn$_{10}$. The main peak is accompanied by a sharp change in the prolate shape of the cluster due to the fusion of the two TTP units to form a compact, near spherical structure with a diffusive liquidlike ionic motion. The small peak at 500 K is associated with rearrangement processes within the TTP units, while the shoulder at 850 K corresponds to distortion of at least one TTP unit, preserving the overall prolate shape of the cluster. At all temperatures observed, the bonding remains covalent.

Abnormally high melting temperature of theSn10cluster

We study the melting of the ${\mathrm{Sn}}_{10}$ cluster with ab initio isokinetic molecular dynamics. The electron localization function is used to probe the bonding character, which is found to be covalent. We use the multiple-histogram technique to calculate the ionic entropy and specific heat, from a total simulation time of more than 2 ns. The specific heat shows a shoulder around 500 K due to a permutational rearrangement of atoms that preserves the trigonal prism core of the ground state. Only at much higher temperatures $T\ensuremath{\gtrsim}1500\mathrm{K}$ does this core distort and break up, yielding a peak in the specific heat around 2300 K. These findings suggest a natural explanation for the recently observed high melting temperatures of small Sn clusters [A. A. Shvartsburg and M. F. Jarrold, Phys. Rev. Lett. 85, 2530 (2000)].

The magnetic fluid for heat transfer applications

Real-time visual observation of boiling water-based and ionic magnetic fluids (MFs) and heat transfer characteristics in heat pipe using ionic MF stabilized by citrate ions (JC-1) as working liquid are reported. Irrespective of the presence or absence of magnetic field water-based MF degraded during boiling. However, the degradation of JC-1 was avoided by heating the fluid in magnetic field. Furthermore, the heat transfer capacity of JC-1 heat pipe under applied magnetic field was enhanced over the no field case.

Hermitian Moment Approach to the Classical Transport Properties of a Weakly Coupled Magnetized Plasma

A complete description of a system in equilibrium is provided by the Grand Canonical Distribution. But, systems are generally not in statistical equilibrium. We shall consider the case of an ideal gaz of charged particles. The linear theory of transport determines the 3 × 1 matrix of dissipative fluxes Jˆr namely, the electric current and the electronic and ionic heat fluxes, in terms of a 3 × 1 matrix of thermodynamic forces Xˆ defined by the electric field and the gradient of the densities and temperatures. The components of the 3 × 3 matrix of tensors Lˆrs of the linear flux-force relations define the set of transport coefficients. They are evaluated for an ion-electron magnetized plasma in the framework of the statistical mechanics of charged particles starting from the Landau kinetic equation.

Apparent molar heat capacities and apparent molar volumes ofY2(SO4)3(aq),La2(SO4)3(aq),Pr2(SO4)3(aq),Nd2(SO4)3(aq),Eu2(SO4)3(aq),Dy2(SO4)3(aq),Ho2(SO4)3(aq), andLu2(SO4)3(aq)atT = 298.15 K andp = 0.1 MPa

The apparent molar heat capacities Cp, φ∘and apparent molar volumes Vφ∘of Y2(SO4)3(aq), La2(SO4)3(aq), Pr2(SO4)3(aq), Nd2(SO4)3(aq), Eu2(SO4)3(aq), Dy2(SO4)3(aq), Ho2(SO4)3(aq), and Lu2(SO4)3(aq) were measured at T= 298.15 K and p= 0.1 MPa with a Sodev (Picker) flow microcalorimeter and a Sodev vibrating-tube densimeter, respectively. These measurements extend from lower molalities of m= (0.005 to 0.018) mol ·kg−1to m= (0.025 to 0.434) mol ·kg−1, where the upper molality limits are slightly below those of the saturated solutions. There are no previously published apparent molar heat capacities for these systems, and only limited apparent molar volume information. Considerable amounts of the R SO4+(aq) and R(SO4)2−(aq) complexes are present, where R denotes a rare-earth, which complicates the interpretation of these thermodynamic quantities. Values of the ionic molar heat capacities and ionic molar volumes of these complexes at infinite dilution are derived from the experimental information, but the calculations are necessarily quite approximate because of the need to estimate ionic activity coefficients and other thermodynamic quantities. Nevertheless, the derived standard ionic molar properties for the various R SO4+(aq) and R(SO4)2−(aq) complexes are probably realistic approximations to the actual values. Comparisons indicate that Vφ∘{RSO4+, aq, 298.15K} =−(6 ± 4)cm3· mol−1and Vφ∘{R(SO4)2−, aq, 298.15K} = (35 ± 3)cm3· mol−1, with no significant variation with rare-earth. In contrast, values of Cp, φ∘{ RSO4+, aq, 298.15K } generally increase with the atomic number of the rare-earth, whereas Cp, φ∘{ R(SO4)2−, aq, 298.15K } shows a less regular trend, although its values are always positive and tend to be larger for the heavier than for the light rare earths.

Global gene expression during short-term ethanol stress in Saccharomyces cerevisiae

DNA microarrays were used to investigate the expression profile of yeast genes in response to ethanol. Up to 3.1% of the genes encoded in the yeast genome were up-regulated by at least a factor of three after 30 min ethanol stress (7% v/v). Concomitantly, 3.2% of the genes were down-regulated by a factor of three. Of the genes up-regulated in response to ethanol 49.4% belong to the environmental stress response and 14.2% belong to the stress gene family. Our data show that in addition to the previously identified ethanol-induced genes, a very large number of genes involved in ionic homeostasis, heat protection, trehalose synthesis and antioxidant defence also respond to ethanol stress. It appears that a large number of the up-regulated genes are involved in energy metabolism. Thus, ‘management’ of the energy pool (especially ATP) seems to constitute an ethanol stress response and to involve different mechanisms.

Magnetized cylindrical targets for heavy ion fusion

Ignition conditions for magnetized cylindrical fusion targets are investigated by means of one-dimensional hydrodynamic calculations. Of particular interest is the effect of a tamper surrounding the fuel at the time of stagnation. The key assumption in this paper is that the targets are magnetically insulated, i.e. electronic and ionic heat conduction as well as the diffusion of 3.5 MeV alpha particles are suppressed. It is found that magnetically insulated targets can be ignited at significantly reduced values of the fuel ρR, but, in contrast to conventional fusion targets, the value of the fuel ρR at ignition depends on the fuel mass as well as on the tamper entropy.

Charge carrier interactions in ionic conductors: A classical molecular-dynamics and Monte Carlo study on AgI

The equilibrium concentration of ionic and electronic charge carriers in ionic crystals as a function of temperature, concentration of dopants, and chemical environment is phenomenologically well understood as long as these point defects can be considered sufficiently dilute. However, there are cases, usually at temperatures close to the melting point, where the defects appear in higher concentrations. In these cases interactions come into play and cause anomalous increases in the conductivity or even phase transitions. Recently Hainovsky and Maier showed that for various Frenkel disordered materials this anomalous conductivity increase at high temperature can be described by a cube root term in the chemical potential of the defects. This quasi-Madelung approach does not only allow ionic conductivities and heat capacities to be computed, it also leads to a phenomenological understanding of the solid–liquid or superionic transition temperatures. In the present study we analyze this approach on the atomistic level for AgI: The defect concentrations as well as defect energies, including excess energies, are computed as a function of temperature by molecular-dynamics and Monte Carlo simulations based on a classical semiempirical potential. The simulations support the cube-root model, yield approximately the same interaction constants and show that the corrections in the chemical potential are of an energetic nature. In agreement with structural expectations, the simulations reveal that two different kinds of interstitials are present: Octahedral interstitials, which essentially determine the ionic transport at higher temperature, and tetrahedral ones, which remain substantially associated with the vacancies. It is shown how these refinements have to be introduced into the cube root.

Classical Transport in Weakly Coupled Magnetized Plasmas

The linear theory of transport determines the 3 × 1 matrix of dissipative fluxes Ĵr namely, the electric current and the electronic and ionic heat fluxes, in terms of a 3 × 1 matrix of thermodynamic forces Xˆ defined by the electric field and the gradient of the densities and temperatures. The components of the 3 × 3 matrix of tensors Lˆrs of the linear flux-force relations Ĵr = Σ9s=1 LˆrsXˆ define the set of transport coefficients. They are evaluated for an ion-electron magnetized plasma in the framework of the statistical mechanics of charged particles starting from the Landau kinetic equation.