Analysis and Optimization of Thermophysical Properties and Phase Change Behavior of Expanded Vermiculite-Based Organic Composite Phase Change Materials

Abstract

In this study, the optimized expanded vermiculite (EVM) was used as the matrix and a series of novel form-stable composite phase change materials (fs-CPCMs) were prepared by the physical impregnation method. The results showed that acid leaching and organic intercalation EVM had a better package effect (≥74.9 wt %) and heat storage capacity (≥139.2 J/g) compared with EVM, which showed a good optimization effect, revealing that proper modification treatment was beneficial to the improvement of the thermophysical properties of composite PCMs. Nonisothermal crystallization kinetics demonstrated that the EVM matrix was beneficial to reduce the nucleation activation energy (ΔE a) of PEG, and the optimized EVM could further reduce the ΔE a, which effectively improved the crystal nucleation process of PEG. However, the matrix would restrict the crystal growth process of PEG, which had certain adverse effects. Moreover, XRD, TGA, and cycle tests showed that the prepared novel fs-CPCMs had excellent chemical stability, thermal stability, and cycle reliability. This research provided a certain theoretical reference and technical support for the preparation of mineral-based organic composite phase change materials with high heat storage capacity and excellent phase change behavior.

Effects of Dopamine-Modified and Organic Intercalation on the Thermophysical Properties of Octadecane/Expanded Vermiculite Composite Phase Change Materials

“…The relationship between the relative crystallinity ( X T ) and time ( t ) or temperature ( T ) could better illustrate the nonisothermal crystallization behavior of octadecane in the EVMs and modified EVMs pores, 17 and their values could be derived from the eqs 2 and 3 . where X T represents relative crystallinity of PCMs, the d H C /d T is the heat flow of crystallization, T B and φ are the temperature at which crystallization begins and cooling rate in the cooling process.…”

“…The relationship between the relative crystallinity ( X T ) and time ( t ) or temperature ( T ) could better illustrate the nonisothermal crystallization behavior of octadecane in the EVMs and modified EVMs pores, and their values could be derived from the eqs and . where X T represents relative crystallinity of PCMs, the d H C /d T is the heat flow of crystallization, T B and φ are the temperature at which crystallization begins and cooling rate in the cooling process. T and t represent any temperature and the cooling time in the crystallization process, the half crystallization time ( t 1/2 ) of octadecane and EVM-based fs-CPCMs could be obtained from Figure and Figure , respectively, and the data are summaried in Table .…”

“…The relationship between the relative crystallinity (X T ) and time (t) or temperature (T) could better illustrate the nonisothermal crystallization behavior of octadecane in the EVMs and modified EVMs pores, 17 and their values could be derived from the eqs 2 and 3.…”

Investigating the Phase Transition Kinetics of 1-Octadecanol/Sorbitol Derivative/Expanded Graphite Composite Phase Change Material with Isoconversional and Multivariate Non-Linear Regression Methods

“…The phase transition process of the composite PCM was investigated using crystallization kinetics, and the results showed that the aerogel skeleton had a heterogeneous nucleation effect on the crystallization of LA, which increased the crystallization rate of LA under non-isothermal and isothermal conditions. Song et al [27] prepared a new shape-stable composite phase change material using the optimized expanded vermiculite (EVM) as a support material. The nonisothermal crystallization kinetics showed that the optimized EVM could effectively reduce the activation energy of nucleation and improve the crystallization and nucleation process of PEG.…”