Facile Preparation of Binary Salt Hydrates/Carbon Nanotube Composite for Thermal Storage Materials with Enhanced Structural Stability

Abstract

Large-scale distributed thermal storage requires high-energy-density and low-cost thermal storage materials. Here, a concocted composite composed of Al 2 (SO 4 ) 3 •18H 2 O and FeSO 4 •7H 2 O salts, as well as carbon nanotubes (CNTs) as a thermal conductive agent has been proposed for the applications of large-scale distributed thermal storage. The composite was physically mixed but displayed enhanced structural stability due to the use of carbon nanotubes that formed networks in the composite. The use of CNTs could restrain the volume change of the salt mixture in thermal charge/discharge. The detailed thermophysical properties and thermal energy storage performance were studied, including latent heat, thermal conductivity, and thermal cycling stability. A differential scanning calorimeter (DSC) revealed that the largely endothermic temperature and absorbed heat of the composite were 118.43 °C and 422.40 J g −1 , and it also delivered a high stability of ca. almost no capacity fading in exampled 100 cycles. The introduction of the carbon nanotube creates thermal conductivity networks in the composite, endowing the composite material with enhanced thermal conductivities. This can provide rapid thermal storage while retaining the storage density. This study can give insights into the rational design of salt hydrates for thermal storage.

Carbon-Enhanced Hydrated Salt Phase Change Materials for Thermal Management Applications

“…Compared with randomly disordered CNTs (r-CNTs), they reported that these a-CNTs have shown stronger enhancement of the thermophysical properties of organic PCMs. In a recent work [81], they directly blended 5 wt% of a-CNTs with a length of 100 µm and 1 wt% of sodium carboxymethyl cellulose (SCMC) thickening agents to improve the thermal storage performance of binary hydrated salts of Al 2 (SO 4 ) 3 •18H 2 O/FeSO 4 •7H 2 O with a mass ratio of 2:1 (Figure 5d). They found that the a-CNTs established a network within the composites, which achieved a thermal conductivity of 3.23 W/(m•K) at room temperature.…”

“…. 2019, Elsevier Ltd.) (d) Binary hydrated salts of Al2(SO4)3•18H2O/FeSO4•7H2O with a mass ratio of 2:1 enhanced by a−CNTs (Figure5dreprinted/adapted with permission from Ref [81]…”

Surface-Modified Compressed Expanded Graphite for Increased Salt Hydrate Phase Change Material Thermal Conductivity and Stability

“…Shape-stabilized composites, characterized by a PCM incorporated into a highly porous matrix such as EG or nanoscale networks such as carbon nanotubes, show reliable, improved performance due to reduced leakage and the potential for thermal conductivity enhancement. 6,30 EG in particular also features a high specific surface area, a characteristic that can help reduce supercooling and phase separation 31 as well as PCM leakage when modified with TX-100 surfactant. 32−34 EG 35,36 matrixes are well-known for enhancing the thermal conductivity of organic paraffin PCMs 37−45 and organic eutectic PCMs.…”

“…The addition of a material with high thermal conductivity, such as graphite, graphene, carbon nanotubes, metal oxide nanoparticles, metal foams, expanded graphite (EG), and clay minerals, has been studied for thermal conductivity enhancement of PCMs, , although most of these studies were conducted on organic PCMs. Shape-stabilized composites, characterized by a PCM incorporated into a highly porous matrix such as EG or nanoscale networks such as carbon nanotubes, show reliable, improved performance due to reduced leakage and the potential for thermal conductivity enhancement. , EG in particular also features a high specific surface area, a characteristic that can help reduce supercooling and phase separation as well as PCM leakage when modified with TX-100 surfactant. − EG , matrixes are well-known for enhancing the thermal conductivity of organic paraffin PCMs − and organic eutectic PCMs . However, there are few efforts that utilize EG in inorganic salt hydrate PCM composites, largely because of challenges in impregnating nonpolar, hydrophobic EG with polar, hydrophilic salt hydrates.…”