Heat Capacity Of Solid Phase Research Articles

Bio-inspired phase change materials designed for high specific heat of solid phase

Abstract Two lipid blends with molar ratios of 2:1:1 and 1.13:1:1 of ceramide (type IV):cholesterol:palmitic acid, namely blends A and B, are prepared, respectively, based on stratum corneum of human. The phase behaviors and nanostructures of those blends have been fully characterized by low-temperature differential scanning calorimetry and small-angle X-ray scattering. The large-scale thermal properties of them have been measured by temperature-history method as well. The heat capacity of solid phase for blend A of 3.23 ± 0.14 J/g °C is higher than the value for common phase change materials (PCMs), such as lauric acid, stearic acid, polyethylene glycol 900, and paraffin wax. The lipid ratio in blend B is also changed to obtain an even higher heat capacity of solid phase of 3.69 ± 0.17 J/g °C. Therefore, we propose to concoct new lipid blends for the enhancement of heat capacity of solid phase values in the immediate future.

Thermodynamic description of the M2O–SiO2 (M = K, Na) systems

The phase diagrams of the M2O–SiO2 (M=K, Na) binary systems were assessed using the Calculation of Phase Diagram (CALPHAD) technique. The thermochemical and phase equilibrium information taken from the literature for these two binary systems have been evaluated, and a series of thermodynamic parameters was obtained to describe each phase in these systems. The liquid phase was described by the ionic two-sublattice model with the formula (M+1)P(O-2,SiO4-4,SiO20,Va-)Q (M=K, Na). The heat capacities of solid phases were taken into consideration in this optimization process, a brief review of which is given in this work. The calculated phase equilibria were found to be in agreement with available experimental data.

Laser-flash calorimetry IV. Heat capacity of gallium from 80 to 600 K in two solid phases and liquid phase

The heat capacity of gallium has been measured by laser-flash calorimetry at temperatures ranging from 80 to 302 K for Ga-I (α-Ga), 210 to 254 K for β-Ga, and 250 to 600 K for liquid gallium. The results are as follows: C p (Ga-I, 298.15 K) = 26.33 J·K −1·mol −1; C p ( β-Ga, 250 K) = 27.67 J·K −1·mol −1; C p (Ga, 1,302.93 K) = 28.24 J·K −1·mol −1. The peculiarity of gallium has been discussed in terms of anharmonic heat capacity of solid phases and of the configurational entropy of the liquid phase.

Thermal conductivity and heat capacity of solid phases of NH4Cl under pressure

The thermal conductivity, lambda , and the heat capacity per unit volume, rho Cp, have been measured for solid phases I, II and III of NH4Cl using the transient hot-wire method. Results were obtained in the temperature range 140-520K, and at pressures up to 2.0 GPa. At the II-III transition, measurements as a function of temperature, to a reduced temperature of order 10-2, showed that lambda was continuous and non-divergent, but that (d lambda /dT)p changed abruptly. The expected maximum in rho Cp was detected, but reliable values of the critical exponent could not be obtained due to experimental limitations. The II-III transition was first order near zero pressure, and probably up to about 0.2 GPa. No direct evidence for a first-order transition was detectable at higher pressures. For phase I, the temperature dependence of lambda was similar to that of plastic crystal phases in other substances. The general form of lambda for NH4Cl was compared to that of NH4F, and found to show significant similarities.

Thermal conductivity and heat capacity of solid phases of benzene under pressure

Using the transient hot-wire method, simultaneous measurements of the thermal conductivity, λ, and the heat capacity per unit volume, ρc p, were made for solid phases I and II of benzene (C6H6). Data were obtained over the temperature range 105 K to 375 K, and at pressures up to 2·4 GPa. At 300 K, the I → II transition was sluggish, so phase I could be retained over a pressure range where it was metastable with respect to phase II. At about 1·2 GPa and 375 K, λ for phase II is detectably greater than for phase I, but at 300 K the two values are almost equal. The value of c p for phase I was found to decrease by about 10 per cent over the range 0–1 GPa and to remain essentially constant at higher pressures. Values of c p in phases I and II were found to be equal at all temperatures. The temperature and volume dependences of λ are discussed in relation to current theoretical ideas.