Accommodating Volume Change and Imparting Thermal Conductivity by Encapsulation of PCMs
Researchers at The Case Western Reserve University recently published an application paper on Accommodating Volume Change and Imparting Thermal Conductivity by Encapsulation of Phase Change Materials in Carbon Nanoparticles. The paper highlights a typical application of C-Therm TCi Thermal Conductivity Analyzer which offers unique capabilities to test both liquid and solid formats of PCMs.
In this study, a Pickering-type emulsion is used as a template to encapsulate the phase change material stearic acid (SA) using graphene oxide nanosheets stitched together. GO-coated SA particles are solid at room temperature and can be used for latent heat storage during the phase change of the SA core. The carbon shell prevents leakage of SA during phase transition from solid to liquid, and significantly improves the thermal conductivity. Additionally, integrity of the GO/PCM particles is maintained upon heating and cooling, even when the particles were composed of up to 85% PCM, maximizing the energy storage capabilities of the material. The “stitched” graphene oxide shells encapsulate, contain, and improve thermal conductivity of PCMs, and thus provide a new materials construct for thermal energy management and storage.
Figure 1. Schematic illustration of the preparation of stearic acid encapsulated by a reduced graphene oxide shell using Pickering-type emulsion.
Figure 2. SEM images of 2.0-rGO-SA at varying magnification.
Thermal conductivity was measured using a TCi Thermal Conductivity Analyzer (C-Therm Technologies). To examine the overall hypothesis that encapsulation of SA in a shell of rGO would improve heat transfer, the thermal conductivities of 2.5-rGO-SA and SA were measured under ambient conditions. The present polymer algorithm was used, employing a modified transient plane source sensor. The average thermal conductivity of 2.5-rGO-SA was ~50% greater than the average value measured for SA (0.57 W/mK and 0.39 W/mK, respectively). Moreover, with only ~5% rGO, the thermal conductivity improvement was similar with previous reports using 50 wt% rGO.17 Of note, many methods have been reported for the reduction of GO nanosheets (chemical and thermal), and future work will focus on optimization of thermal conductivity without detriment to encapsulation of different PCMs.
Figure 3. Thermal conductivity results of 2.5-rGO-SA and SA
Information source: P. Advincula, et al., Accommodating Volume Change and Imparting Thermal Conductivity by Encapsulation of Phase Change Materials in Carbon Nanoparticles (2018)
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