Abstract
Organic phase change materials (PCMs) have great potential in thermal protection applications but they suffer from high volumetric change and easy leakage, which require “leak-proof” packaging materials with low thermal conductivity. Herein, we successfully modify SiO2 through a simple 2-step method consisting of n-hexane activation followed by short-chain alkane silanization. The modified SiO2 (M-SiO2) exhibits superior hydrophobic property while maintaining the intrinsic high porosity of SiO2. The surface modification significantly improves the absorption rate of RT60 in SiO2 by 38%. The M-SiO2/RT60 composite shows high latent heat of 180 J·g−1, low thermal conductivity of 0.178 W·m−1·K−1, and great heat capacity behavior in a high-power thermal circuit with low penetrated heating flow. Our results provide a simple approach for preparing hydrophobic SiO2 with high absorption of organic PCM for thermal protection applications.
Highlights
Phase change materials (PCMs), a kind of materials with significant amounts of enthalpy through their phase transformations from liquid to solid [1,2], have attracted attention for their application in the thermal protection [3,4], energy storage [5,6,7], thermoregulation [8,9] and energy saving [10]
PCMs, In this work, hydrophobic SiO2 aerogel was obtained by short chain alkyl modification through ahysdimroppleho2bsitcepMm-SeitOh2o.dI.nTchoenNtr-ahsetxtaonecoancvtievnaqttiio=onnaλfloTllol∆−onxwTg0-ecdhabiynsmhoordt-icfhicaaitnioanlkoafneSisOil2a,ntihzeatsiohnorytieclhdae(i2dn) modification did not result in significant shrinking of the pore size
RT60/modified SiO2 (M-SiO2) composite was able to rectify of cooling thermal energy of 245 W·m−2, and could be used where q is the apparent rectified heat flow (W·m−2), λ is the thermal conductivity(W·m−1·K−1), T is the temperature of PCMs side, T0 is the ambient temperature, ∆x is the thickness of the PCMs
Summary
Phase change materials (PCMs), a kind of materials with significant amounts of enthalpy through their phase transformations from liquid to solid [1,2], have attracted attention for their application in the thermal protection [3,4], energy storage [5,6,7], thermoregulation [8,9] and energy saving [10]. Carbon materials like graphene form, carbon nanotube sponge are currently too expansive for industrial application Porous oxide materials such as bentonite [29], diatomite [30], and expanded perlite [31] can absorb PCMs to form phase change composite with low thermal conductivity, but these phase change composites are seriously restricted by their poor absorption of organic PCMs. Silica (SiO2) aerogel, a scaffold ultralight material with high pore volume, large surface area, low thermal conductivity and high thermal stability, is a promising material for encapsulating organic PCMs [32,33] for thermal protection applications. The M-SiO2 aerogel-based phase change composite could rectify the large ambient heat flow and exhibits great potential for thermal protection applications
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