Mechanical, Thermal, and Electrical Energy Storage in a Single Working Body: Electrification and Thermal Effects upon Pressure-Induced Water Intrusion-Extrusion in Nanoporous Solids.

This paper presents the first experimental evidence of pronounced electrification effects upon reversible cycle of forced water intrusion-extrusion in nanoporous hydrophobic materials. Recorded generation of electricity combined with high-pressure calorimetric measurements improves the energy balance of {nanoporous solid + nonwetting liquid} systems by compensating mechanical and thermal energy hysteresis in the cycle. Revealed phenomena provide a novel way of "mechanical to electrical" and/or "thermal to electrical" energy transformation with unprecedented efficiency and additionally open a perspective to increase the efficiency of numerous energy applications based on such systems taking advantage of electricity generation during operational cycle.

Evolution of the energetic characteristics of {silicalite-1 + water} repulsive clathrates in a wide temperature range.

Recently {lyophobic porous powders + liquid} systems were proposed to be used for nontraditional energy storage and conversion purposes. This article reports the experimental study of the mechanical behavior, within the pressure-volume (PV) diagram, of the {hydrophobic silicalite-1 + water} system in the temperature range 10-80 °C. Repeated recordings of PV-isotherms and thermal effects of the repulsive clathrate during successive compression-decompression runs were performed using scanning transitiometry. An unexpected steady decline in the intrusion-extrusion pressure and volume of embedded water was found during the forced (repeated) intrusion of water into the pores of silicalite-1 and its spontaneous extrusion at constant temperature. A discussion of possible reasons of unconventional behavior of these heterogeneous systems as well as a thermodynamic analysis is presented.

On the physical meaning of the isothermal titration calorimetry measurements in calorimeters with full cells.

We have performed a detailed study of the thermodynamics of the titration process in an isothermal titration calorimeter with full cells. We show that the relationship between the enthalpy and the heat measured is better described in terms of the equation Delta H = W(inj) + Q (where W(inj) is the work necessary to carry out the titration) than in terms of DeltaH = Q. Moreover, we show that the heat of interaction between two components is related to the partial enthalpy of interaction at infinite dilution of the titrant component, as well as to its partial volume of interaction at infinite dilution.

Diffusion in mesoporous materials and polymers swelling: a transient calorimetric approach.

The diffusion of water and benzene has been followed by DSC using the thermoporosimetry (TPM) approach. The diffusion of water has been observed during the drying of a water impregnated mesoporous silica gel at 40 degrees C under dry air. It was found that the confinement affects the evaporation rate of water. The diffusion of benzene has been observed during the drying and the swelling of a cross linked PDMS sample. The mesh size distributions (MSD) of the elastomer, during swelling and drying, have been calculated at various times using the TPM formalism. Extrapolating the mean mesh size of the polymeric network, it was found that the dry polymer has an average mesh of about 2.5 nm.

Study of the binding between lysozyme and C10-TAB: determination and interpretation of the partial properties of protein and surfactant at infinite dilution.

This work examines the binding in aqueous solution, through the experimental determination of specific volumes and specific adiabatic compressibility coefficients, of decyltrimethylammonium bromide to lysozyme and to non-charged polymeric particles (which have been specially synthesized by emulsion polymerization). A method was developed to calculate the specific partial properties at infinite dilution and it was shown that a Gibbs-Duhem type equation holds at this limit for two solutes. With this equation, it is possible to relate the behavior of the partial properties along different binding types at a constant temperature. It was found that the first binding type, specific with high affinity, is related to a significant reduction of surfactant compressibility. The second binding type is accompanied by the unfolding of the protein and the third one is qualitatively identical to the binding of the surfactant to non-charged polymeric particles.

Crystallization of carbon tetrachloride in confined geometries.

The thermal behaviour of carbon tetrachloride confined in silica gels of different porosities was studied by differential scanning calorimetry. Both the melting point and the low temperature phase transition were measured and found to be inextricably dependant on the degree of confinement. The amount of solvent was varied through two sets of experiments, sequential addition and original progressive evaporation allowing the measurement of DSC signals for the various transitions as a function of the amount of CCl4. These experiments allowed the determination of the transition enthalpies in the confined state, which in turn allowed the determination of the exact quantities of solvent undergoing these transitions. A clear correlation was found between the amounts of solvent (both free and confined) undergoing the two transitions, demonstrating that the formation of the adsorbed layer t does not interfere with the second transition. The thickness of this layer and the porous volumes of the two silica samples were measured and found to be in very close agreement with the values determined by gas sorption.

Isothermal crystallization kinetics of in situ photo and thermo aged poly(ethylene oxide) using photoDSC.

Isothermal crystallization of a high molecular weight PEO (Mw=4,000,000) has been investigated using photoDSC. Combining light irradiation, heating and DSC analysis, photoDSC demonstrates good capability to follow the in situ photo- and thermo-ageing of semi-crystalline polymers. Isothermal crystallization of PEO was performed at 55 degrees C. After ageing at different temperatures ranging from 0 to 90 degrees C and for various periods of time, the kinetics of this crystallization was found following the Avrami theory. Avrami exponent, n, was found between 0.9 and 1.4 evidencing a one-dimension growth process. It was also found that the isothermal crystallization rate (i.e. reciprocal crystallization half-time) was exposure time, ageing temperature and light intensity dependent which makes this kinetic parameter a good indicator of following and comparing the degradation of the semi-crystalline polymers.

Effect of n-alkanes on asphaltene structuring in petroleum oils.

The interactions between asphaltenes and short- to medium-chain n-alkanes were studied using titration microcalorimetry and inverse chromatography. The exothermic heat effects observed upon mixing of asphaltenes and n-alkanes were interpreted in terms of assembling of the two types of compounds into mixed structures. We show that the energy of the interactions between n-alkanes and the asphaltene hydrocarbon chains is close to the energy of the interactions between the asphaltene chains. We propose that the latter interactions are responsible for the formation of the asphaltene aggregates and are the driving force of the aggregate assembly into higher structures.

Influence of fiber on the phase transformations in the starch-water system.

High-sensitivity, temperature-controlled DSC measurements at a low heating rate and creation of differential DSC traces scaled with respect to the reference material (completely dehydrated starch or completely dehydrated fiber, or their respective blends) permitted investigation of the influence of fiber on phase transformations in the wheat-starch-water system in the course of thermal gelatinization. Thermal effects associated with water interactions over the temperature range from 283 to 384 K under atmospheric pressure were determined. These thermal effects and previous structural studies permit us to make the following observations: (1) The main endothermic transition associated with melting of the crystalline part of the starch granule followed by a helix-coil transition in amylopectin occurs over the temperature range 319-333 K independent of the water and fiber contents. Adding fiber causes that transition to disappear both in the native blends and in water suspensions at low water contents. After adding more water and heating, recrystallization is observed and the transition reappears. (2) The fiber content has practically no influence on the slow exothermic transformation, which follows melting and helix-coil transition in amylopectin, proving that the slow transformation has a specific chemical character. In this reaction, the free ends of the unwound helices of amylopectin reassociate with parts of amylopectin molecules other than their original helix duplex partner, forming physical junctions and creating more general amorphous hydrogen bonded associations. (3) The high-temperature transition and small, but reproducible, distortions on the peaks of the main endothermic transition for water contents near 70-80 wt % are associated with smectic and nematic transitions, respectively. These are significantly influenced by the fiber content; higher fiber content causes an almost complete disappearance of these transitions. (4) The slow exothermic effect appearing almost from the very beginning of the heating in the starch-water system, associated with softening and uptake of water in the amorphous growth rings of the starch granule, is significantly hindered by added fiber.