Expanded Vermiculite: A Promising Natural Encapsulation Material of LiNO₃, NaNO₃, and KNO₃ Phase Change Materials for Medium‐Temperature Thermal Energy Storage

Abstract

In the study, with LiNO 3 , NaNO 3 , and KNO 3 as medium-temperature phase change materials (PCMs) and expanded vermiculite (EVM) as the encapsulation material, form-stable composite PCMs (fs-CPCMs) are prepared. The experimental value of maximum encapsulation mass fractions of LiNO 3 -EVM, NaNO 3 -EVM, and KNO 3 -EVM is, respectively, 84.6, 85.7, and 87.0 wt%, which is lower than the theoretical value since the pore structures of EVM are not fully filled by PCMs. SEM results indicate that the PCMs are uniformly distributed and embedded into the pores or on the surfaces of EVM. The excellent chemical compatibility of PCMs with EVM is confirmed by XRD and FT-IR results. DSC tests indicate the phase change temperatures of three fs-CPCMs are between 243.1 and 325.1 C and that latent heats are between 83.1 and 295.4 J g À1 . After 100 melting/solidification cycles, the decrease in latent heats of fs-CPCMs are below 1.91%, exhibiting desirable thermal reliability. The thermal conductivity of LiNO 3 -EVM, NaNO 3 -EVM, and KNO 3 -EVM is, respectively, 0.51, 0.44, and 0.33 W/(m K), indicating acceptable thermal energy charging/discharging rate. TGA analysis reveal that fs-CPCMs show good thermal stability within the designed working temperature range. Therefore, EVM is a promising natural encapsulation material for medium-temperature heat storage.

Recent advances in energy storage and applications of form‐stable phase change materials with recyclable skeleton

“…In addition, both of the thermal conductivities for the two form-stable PCMs were slightly decreased compared to NaNO 3 (approximately 0.5 W/m•K). [103] The difference between the thermal conductivity of recyclable skeleton materials and PCMs used during the preparation of the form-stable PCMs is the main reason for the change in the thermal conductivity of the recyclable form-stable PCMs. Therefore, to make the maximum use of the thermal storage properties of the form-stable PCMs, the materials with suitable thermal conductivity should be selected as supporting skeleton according to the uses and functions of the form-stable PCMs in specific applications.…”

“…In addition, both of the thermal conductivities for the two form‐stable PCMs were slightly decreased compared to NaNO 3 (approximately 0.5 W/m·K). [ 103 ]…”

Biotechnological development of Trichoderma-based formulations for biological control

“…2 A summary of vermiculite and biochar mineral-based dry formulations. A SEM image showing the plate-like structure of solid vermiculite particles; adapted with permission (Deng et al 2018 ), copyright Wiley 2018. B Viability of T. harzianum population after 4 weeks of storage either non-formulated ( NF ) or mixed with a vermiculite-based carrier ( F ); adapted with permission (Martínez-Medina et al 2009 ), copyright American Society for Horticultural Science 2009.…”

Li4(OH)3Br-Based Shape Stabilized Composites for High-Temperature TES Applications: Selection of the Most Convenient Supporting Material

“…The ss-composites using expanded graphite are usually prepared by the uniaxial or isostatic cold-compression route, whereas the vacuum-assisted melting infiltration method is used in the preparation of graphite foam-based composites. Clay mineral supporting materials such as expanded perlite, expanded vermiculite and diatomite [ 9 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ]. They demonstrate chemical compatibility with nitrites, chlorides and sulfates as well as high salt absorption capacity (>85 wt.% for expanded perlite and vermiculite; 55–70 wt.% for diatomite).…”