Microstructural improvement of solar salt based MgO composites through surface tension/wettability modification with SiO2 nanoparticles
Microstructural improvement of solar salt based MgO composites through surface tension/wettability modification with SiO2 nanoparticles
复制标题
DOI：
10.1016/j.solmat.2022.111577
复制
发表时间：
2022-05
影响因子：
6.9
通讯作者：
A. Anagnostopoulos;M. Navarro;Yulong Ding
中科院分区：
文献类型：
--
作者：
A. Anagnostopoulos;M. Navarro;Yulong Ding
复合相变材料（CPMC）在高温热能储存和废热利用应用中特别令人感兴趣。为了进一步增强其导热性，CPCM通常掺杂有纳米尺寸的颗粒（NP）。然而，NP的影响的PCM的粘度和润湿性，显着贡献的CPCM的微观结构。它们对PCM粘度的影响已被广泛记录，但对其润湿性的影响却鲜有报道。为此，我们调查，使用定制的最大气泡压力张力计，太阳能盐的表面张力，以及其在MgO {1 0 0}表面上的接触角与不同浓度的α-SiO2纳米粒子。在0.5重量%时，观察到表面张力增加2.45%，在2.5重量%时按比例增加至11.8%。与纯盐相反，在SiO2的存在下，表面张力增加到400 °C，然后快速衰减，这被发现与NP团聚和随后的沉降有关。在接触角方面，NP的加入导致熔点增加，但在390 °C下达到完全润湿条件，与α-SiO2含量无关。为了利用这种效应，将不具有和具有1.0重量% SiO2的MgO-太阳能盐CPCM在390 °C下保持5小时。二氧化硅的添加导致更小的泄漏（质量损失）、改进的密度（8.9%）、改进的孔隙率（18.9%）、平均孔径减小（100%）和增强的热扩散率（6.5%）。这被认为是间接相关的表面张力/润湿性的修改，通过掺杂与极性纳米粒子。
Composite phase change materials (CPMCs) are of particular interest in high-temperature thermal energy storage and waste heat utilization applications. To further enhance their thermal conductivity, CPCMs are often doped with nanosized particles (NPs). However, NP's influence the PCM's viscosity and wettability, significantly contributing to the CPCM's microstructure. Their effects on the PCM's viscosity have been extensively documented, but little has been done on its effect on wettability. To this end, we investigated, using a custom maximum bubble pressure tensiometer, the surface tension of the solar salt, as well as its contact angle on an MgO {1 0 0} surface with various concentrations of α-SiO2NPs. At 0.5 wt%, an increase of 2.45% on the surface tension is observed, scaling up to 11.8% at 2.5 wt%. Contrary to the pure salt, in the presence of SiO2the surface tension increases up to 400 °C followed by rapid decay, which is found to be related to NP agglomeration and subsequent sedimentation. In terms of contact angle NP addition leads to an increase at the melting point, but fully wetting conditions are attained at 390 °C independent of α-SiO2content. To capitalize on this effect, MgO-Solar salt CPCMs without and with 1.0 wt % SiO2are kept at 390 °C for 5 h. Silica addition leads to smaller leakage (mass loss), improved density (by 8.9%), improved porosity (by 18.9%), mean pore size reduction (by 100%) and enhanced thermal diffusivity (by 6.5%). This is suggested to be indirectly related to the surface tension/wettability modification through doping with polar NPs.