Vasilyev Gleb, Koifman Naama, Shuster Michael, Gishvoliner Michael, Cohen Yachin, Zussman Eyal
Faculty of Mechanical Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel.
Faculty of Chemical Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel.
ACS Omega. 2022 Mar 29;7(14):11887-11902. doi: 10.1021/acsomega.1c07376. eCollection 2022 Apr 12.
Blending two gelators with different chemistries (12-hydroxystearic acid and a bis-urea derivative, Millithix MT-800) was used to impart shape stability to CrodaTherm 29, a bio-based phase change material (PCM), melting/crystallizing at near-ambient temperature. The gelators immobilized the PCM by forming an interpenetrating fibrillar network. 15 wt % concentration of the gelators was found to be effective in preventing liquid PCM leakage. In order to improve the mechanical properties and thermal conductivity (TC) of the PCM, gelation of suspensions of multiwalled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GnPs) in a molten material was done at concentrations exceeding their percolation thresholds. Compared to pristine PCM, the gelled PCM containing 3.0 wt % of GnPs demonstrated a shorter crystallization time, ∼1.5-fold increase in strength, improved stability, and ∼65% increase in TC. At the same time, PCM filled with up to 0.6 wt % of MWCNTs had diminished strength and increased leakage with a slight TC improvement. Gelation of PCM did not significantly alter its thermal behavior, but it did change its crystalline morphology. The developed shape-stable PCMs may have a wide range of applications in ambient temperature solar-thermal installations, for example, temperature-controlled greenhouses, net zero-energy buildings, and water heaters.
将两种具有不同化学组成的胶凝剂（12-羟基硬脂酸和双脲衍生物Millithix MT-800）混合，用于赋予CrodaTherm 29形状稳定性，CrodaTherm 29是一种生物基相变材料（PCM），在接近环境温度下熔化/结晶。胶凝剂通过形成互穿的纤维状网络来固定PCM。发现15 wt%浓度的胶凝剂可有效防止液态PCM泄漏。为了改善PCM的机械性能和热导率（TC），在多壁碳纳米管（MWCNT）和石墨烯纳米片（GnP）的悬浮液在熔融材料中的浓度超过其渗流阈值时进行凝胶化。与原始PCM相比，含有3.0 wt% GnP的凝胶化PCM表现出更短的结晶时间、强度提高约1.5倍、稳定性提高以及TC提高约65%。同时，填充高达0.6 wt% MWCNT的PCM强度降低且泄漏增加，TC略有改善。PCM的凝胶化并未显著改变其热行为，但确实改变了其晶体形态。所开发的形状稳定PCM在环境温度太阳能热装置中可能有广泛应用，例如，温控温室、净零能耗建筑和热水器。
