Enhanced thermal conductivity of form-stable phase change composite with single-walled carbon nanotubes for thermal energy storage

Abstract

A striking contrast in the thermal conductivities of polyethylene glycol (PEG)/diatomite form-stable phase change composite (fs-PCC) with single-walled carbon nanotubes (SWCNs) as nano-additive has been reported in our present study. Compared to the pure PEG, the thermal conductivity of the prepared fs-PCC has increased from 0.24 W/mK to 0.87 W/Mk with a small SWCNs loading of 2 wt%. SWCNs are decorated on the inner surface of diatomite pores whilst retaining its porous structure. Compared to PEG/diatomite fs-PCC, the melting and solidification time of the PEG/diatomite/SWCNs fs-PCC are respectively decreased by 54.7% and 51.1%, and its thermal conductivity is 2.8 times higher. The composite can contain PEG as high as 60 wt% and maintain its original shape perfectly without any PEG leakage after subjected to 200 melt-freeze cycles. DSC results indicates that the melting point of the PEG/diatomite/SWCNs fs-PCC shifts to a lower temperature while the solidification point shifts to a higher temperature due to the presence of SWCNs. Importantly, the use of SWCNs is found to have clear beneficial effects for enhancing the thermal conductivity and thermal storage/release rates, without affecting thermal properties, chemical compatibility and thermal stability. The prepared PEG/diatomite/SWCNs fs-PCC exhibits excellent chemical and thermal durability and has potential application in solar thermal energy storage and solar heating.

Facile preparation of aqueous-soluble fluorescent polyethylene glycol functionalized carbon dots from palm waste by one-pot hydrothermal carbonization for colon cancer nanotheranostics

“…Figures 6 a,b show the thermal degradation of CDs and CDs-PEG synthesized by hydrothermal carbonization at the same condition at 220 °C for 6 h. It was observed that CDs-220C-6h showed the slow decomposition according to the heating time, however CDs-PEG showed the rapid degradation at temperature 400 °C regarding the breakdown of PEG molecules passivated on CDs. From the previous report, PEG (Mw = 6000) was thermally decomposed starting from 250 to 400 °C for complete decomposition of PEG 50 . With narrow DTG peak from CDs-PEG illustrated in Fig.…”

Effects of carbon nanotubes additive on thermal conductivity and thermal energy storage properties of a novel composite phase change material

“…In Table 6, the increment ratios in thermal conductivities of the composite PCMs with CNT doping were compared to different clay-based composite PCMs doped with carbon-based additives. 37,67–73 As obviously seen, especially in case of 5 wt% CNTs adding, the increase percentage in thermal conductivity was higher than that of most of the CPCMs. This evaluation exhibits that the improvement in thermal conductivity of the CPCMs can be changed considerably depending on the thermal conductivity of main supporting matrix, additive material and their mass fractions.…”

Carbonized waste hazelnut wood‐based shape‐stable composite phase change materials for thermal management implementations

“…This can be explained by two cases: First, since the CA is held in the porous structure of both carbon materials by the capillary and surface tension forces, its movement which causes the delay of its crystallization is restricted, thereby become more quickly solidified 40 . The second case might be that the supporting CHW and ACHW materials provide heat conduction paths, thereby accelerating the phase transition speed of the CA 20 …”

“…During the melting and solidification phase transformations, PCMs perform LHTES function, while the supporter materials prevents PCM seepage in liquid state and ensures the solid shape to be fully preserved 12‐16 . Some of the porous materials commonly used in the production of shape stable composites are attapulgite, 17 expanded perlite, 18 sepiolite, 11 vermiculite, 19 diatomite 14,20 and silica fume 8,21 . However, many of these materials themselves have low thermal conductivity and hence it is obvious that they cannot help increase the thermal conductivity of PCMs.…”