Partial Entropy Change Research Articles

Microcalorimetry electrothermal impedance spectroscopy (ETIS) informs entropy evolution at individual electrodes of PNb9O25 or TiNb2O7 battery cells

This study proposes a novel and fast microcalorimetry electrothermal impedance spectroscopy (ETIS) method based on heat generation rate measurements at each electrode of a lithium-ion battery cell. This new method is capable of retrieving the open-circuit voltage, the entropic potential, and the partial entropy changes at each electrode from measurements at a single temperature. It also shortens the measurement duration to a few hours compared to several days using the galvanostatic intermittent titration technique (GITT). The method consists of imposing a sinusoidal current on the cell assembled in an operando isothermal calorimeter. The induced sinusoidal potential response is used to calculate the open-circuit voltage of the cell as a function of the state of charge. The measured heat generation rates are analyzed by fast Fourier transform to determine not only the entropic potential of the cell but also the partial entropy changes at each electrode. This novel microcalorimetry ETIS method was first validated with numerical simulations. Then, it was experimentally demonstrated on battery cells consisting of PNb9O25 or TiNb2O7 working electrodes and metallic lithium counter electrodes in 1 M LiPF6 in EC:DMC 1:1 v/v electrolyte. The results of the open-circuit voltage and the normalized entropic potential matched those previously determined by potentiometric entropy measurements based on GITT measurements at different temperatures. Furthermore, while the normalized partial entropy changes exhibited notable features at the PNb9O25 or TiNb2O7 working electrodes, they varied little at the metallic lithium counter electrodes.

Proton Electroinsertion in Self-Assembled Materials for Neutralization Pseudocapacitors

We propose novel pseudocapacitors that can store energy related to the partial entropy change associated with proton concentration variations following neutralization reactions. In this situation, it is possible to obtain electrochemical energy after the complete charge/discharge cycle conducted in electrolytic solutions with different proton concentrations. To this end, we prepared modified electrodes from phosphomolybdic acid (PMA), poly(3,4-ethylenedioxythiophene/poly(styrenesulfonate) (PEDOT-PSS), and polyallylamine (PAH) by the layer-by-layer (LbL) method and investigated their electrochemical behavior, aiming to use them in these neutralization pseudocapacitors. We analyzed the potentiodynamic profile of the current density at several scan rates, to evaluate the reversibility of the proton electroinsertion process, which is crucial to maximum energy storage efficiency. On the basis of the proposed reaction mechanism and by using frequency-domain measurements and models, we determined rate constants at different potentials. Our results demonstrated that the conducting polymer affects the self-assembled matrixes, ensuring that energy storage is high (22.5 kJ mol(-1)). The process involved neutralization of a hydrochloric acid solution from pH = 1 to pH = 6, which corresponds to 40% of the neutralization enthalpy.

The Dynamics of Entropy Exchange between Field and Atom

This paper investigate the partial entropy changes of the field and the atom in a system of an atom interacting with a single quantized cavity field including acceptable kinds of nonlinearities of both the field and the intensity-dependent atom-field coupling. The work shows that the substantial entropy exchange can occur when the mixed state parameters of the atom and the average number of photons in the cavity are respectively bounded within certain parameter regimes, and the substantial entropy exchange is independent of the parameters of the non-linear medium, the intensity of non-linear coupling and detuning. It is also explored that the detuning leads to collapse-revival of the field and atomic partial entropy changes occurring.

Partial entropy creation of a two-level atom with intrinsic decoherence

By using an algebraic dynamical approach, the atom–field bipartite system in mixed state is employed to investigate the influence of intrinsic decoherence and Stark shift on the partial entropy change and the entanglement. It is shown that, quality of the partial entropy is improved significantly by introducing the intrinsic decoherence and(or)Stark shift. In addition, by the concept of the lower bound of the concurrence, the entanglement between the atom and the field under the influences of intrinsic decoherence and Stark shift is also presented.

Partial entropy change and entanglement in the mixed state for a Jaynes–Cummings model with Kerr medium

By using the algebraic dynamical approach, an atom-field bipartite system in mixed state is employed to investigate the partial entropy change and the entanglement in a cavity filled with Kerr medium. The effects of different nonlinear intensities are studied. One can find that the Kerr nonlinearity can reduce the fluctuation amplitudes of the partial entropy changes and the entanglement of the two subsystems, and also influence their periodic evolution. Meanwhile, increasing the Kerr nonlinear strength can convert the anti-correlated behaviour of the partial entropy change to the positively correlated behaviour. Furthermore, the entanglement greatly depends on the temperature. When the temperature or the nonlinear intensity increases to a certain value, the entanglement can be suppressed greatly.

Correlation between the temperature coefficient of the surface tension and the partial entropy

The author’s correlation equation relating the temperature coefficient of the surface tension to the partial entropy and the adsorption value is supported by measurements of the surface tension in alkali solutions. The oscillatory character of partial entropy changes is explained by the formation of crystalline hydrates.

Some Thermodynamic Properties of Soil Water

AbstractThe partial specific Gibbs free energy or moisture potential of soil water has been measured by methods that are widely accepted. There are several other thermodynamic properties that are of significance in soil moisture relationships that are not so readily measured and are not well understood. The partial specific entropy and enthaply (heat content) of soil water are two such properties of interest. They have been calculated from the temperature dependence of the moisture potential.The moisture content, solute content and pressure of soil samples were held constant. The temperature of the system ranged between 2° and 45° C. It was changed periodically and controlled at well‐defined intervals. After each change in temperature, the system was allowed to come to equilibrium and the moisture potential, as measured by tensiometers, was determined. From the temperature dependence of the moisture potential, the partial entropy change of soil water was found to be more negative than that of free water. Significant entropy differences were found in soils that contained water at a moisture potential of 0.008 joules per g. (0.08 bars suction) at about 20° C. The partial specific entropy and enthalpy of soil water were found to be dependent upon moisture content and temperature.