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We report on TES (thermal energy storage) in new CT (continuous phase transitions) in multicomponent tetrahederally configured (orientationally disordered) crystals of NPG-neopentylglycol-C 5 H 12 O 2 , PG-pentaglycerine-C 5 H 12 O 3 , and PE-pentaerythritol-C 5 H 12 O 4 . This discovery is applicable in thermal energy storage in many systems which do not require conventional isothermal first-order phase transition energy storage. The above compounds exhibit polymorphs of orientationally disordered phases in which O–H…O bond rotation around the C–C bond stores significant amount of energy; for example, in PE 41.26 kJ/mol are absorbed isothermally during solid–solid transitions. In this paper we show, anisothermal continuous phase transitions (CT), due to compositional changes with changes in temperature, associated with a measurable amount of energy, not reported earlier. The correlation of phase stability regions in pseudo-binaries, calculated from ternary NPG–PG–PE phase diagrams, is validated by experimental ternary DSC (differential scanning calorimetry) and in-situ x-ray diffraction data. We established equations for determining the CT in a temperature range, and their respective enthalpies of transitions for any composition of the ternaries. Thermodynamic calculations of the Gibbs energies of the solution phases are modeled as substitutional solid solutions, in which the excess Gibbs energies are expressed by the Redlich–Kister–Muggianu polynomial. There is excellent agreement between the experimental and CALPHAD calculated data. [ABSTRACT FROM AUTHOR]

Abstract: The pentaerythritol (PE)–pentaglycerine (PG)–neopentylglycol (NPG) ternary system has been thermodynamically assessed using the CALPHAD method and Thermo-Calc software. The PE–PG, PG–NPG, PE–NPG binary systems have also been calculated using CALPHAD on the basis of reported binary experimental data. The solution phases are modeled as substitutional solutions, in which the excess Gibbs energies are expressed by the Redlich–Kister–Muggianu polynomial. The PE–NPG binary phase diagram was modeled using Henrian solution model, and the liquid phase was assumed ideal. The PG–NPG system was optimized using regular and sub-regular solution models and show invariant equilibria at 298K. The PE–NPG binary system was calculated from room temperature to the liquid phase temperatures. The modeled phase diagrams and the experimental data are in good agreement. A set of self consistent thermodynamic parameters formulating the Gibbs energies of various phases in the PE–PG–NPG ternary system are obtained in the present work. Thermodynamic properties, several vertical and isopleth sections have been calculated and are in good agreement with experimental data. [Copyright &y& Elsevier]

Abstract: High proton conductivity has been achieved in the high temperature plastic crystal phase of pentaglycerine when doped with strong acids, including trifluoromethanesulfonic acid (triflic acid) and methanesulfonic acid. The solid–solid phase transition from the ordered to plastic phase in this material occurs at 86 °C and conductivities of 10−3 S/cm were measured in the high temperature plastic phase on the addition of 1 mol% triflic acid. In the case of methanesulfonic acid, the conductivities showed a greater dependence on acid concentration and were lower than for triflic acid, as expected on the basis of acid strengths. Electrochemical characterisation shows a clear hydrogen reduction process indicating that the proton is the mobile species in the plastic phase. [Copyright &y& Elsevier]

In this work, a novel solid–solid phase change material (SS‐PCM), pentaglycerine/expanded graphite (PG/ExG) is developed. ExG is introduced into PG to enhance its thermophysical properties. The results of SEM, FT‐IR, and XRD indicate that PG and ExG are physically well combined in the composites. DSC results show that the phase change temperature of the PG/ExGs are not significantly different from those of PG. The melting latent heat of PG/ExG containing 1, 2, and 4 wt% ExG are 163.8, 161.6, and 160.1 J g−1, respectively. Although the latent heat of PG/ExG decreases with the addition of ExG, the total heat storage capacity of PG/ExG increases due to the increase in specific heat of composite PCMs. The thermal conductivities of PG/ExG containing 1, 2, and 4 wt% ExG are 0.647 W/(m · K), 0.863 W/(m · K), and 0.944 W/(m · K), respectively, while that of PG is just 0.232 W/(m · K). Thermal performance tests further verify the enhancement to heat transfer performance of PG with ExG. The results of thermal cycling tests substantially indicate that the PG‐based SS‐PCMs have noticeable thermal reliabilities after 100 cycles. In conclusion, the PG/ExG composite PCMs with comprehensive properties will have potential for usage in energy storage and thermal management systems. A series of SS‐PCMs are prepared by introducing expanded graphite (ExG) into pentaglycerine (PG). PG and ExG are physically combined with each other. The total heat storage density (sensible and latent heat) of PG/ExG composites are not decreased by adding ExG. Thermal conductivity of PG/ExG composites are increased with the increasing of ExG. PG/ExG composites show the excellent thermal properties. [ABSTRACT FROM AUTHOR]