Diverting phase transition of high-melting-point stearic acid to room temperature by microencapsulation in boehmite

Abstract

Organic phase change materials (OPCMs) have long been recognized as potentially reversible thermal energy storage candidates due to their ability to reversibly store or release large amounts of latent heat when changing from one physical state to another. For application of which in solar heat storage, reducing their relatively high phase transition temperature (T C ) to room temperature is still challenging. Herein, a microemulsion with metastable interface is adopted for in situ synthesis of sphere-like structure stearic acid (SA)@boehmite (g-AlOOH) microcapsules. Interestingly, when the high-melting-point SA crystals (T C ¼ 70.8 C) were capsulated into boehmite nanoshells, their phase transition could be diverted to room temperature ($21 C), which means about 50 C decrease of their phase change temperature has been achieved. This dramatic change could be due to a confinement effect on the interface between SA cores and the boehmite nanoshells, which leads to a change of geometric factors and enhancement of shell-SA interactions. Furthermore, the heat energy storage density ($140 kJ kg À1 ) of the obtained SA@g-AlOOH microcapsules is higher than that of most common room temperature PCMs, suggesting an efficient heat storage ability. This kind of shape-stabilized microcapsule can be considered as candidate room temperature PCMs for thermal energy storage.

Stearic-acid/carbon-nanotube composites with tailored shape-stabilized phase transitions and light–heat conversion for thermal energy storage

“…The change in phase change temperatures of PCMs in the confined space is related to not only the pore radius but also hostguest interactions, which has been demonstrated by some previous reports [25,32,33]. Therefore, in the present case, the strong interaction between SA molecules and a-CNTs by functional groups enable SA molecules to be confined geometries, which will make the SA molecule conformation abnormal and therefore strongly affect their thermodynamic responses, leading to drastic changes in their phase transitions.…”

“…(4) to be 99.9% (Composite-1), 103.4% (Composite-2), and 99.8% (Composite-3), respectively. The thermal storage capacities of our composite PCMs are much higher than those of the encapsulated composite PCMs reported previously [32,33]. The results suggest that most of SA confined in the composites can act as efficient PCM for thermal storage.…”

“…The broad band around 3450 cm À1 belongs to the OAH stretching vibration. The interaction between SA and a-CNTs is verified by the shift of C@O stretching band of SA from original $1700 cm À1 to a lower frequency of $1640 cm À1 , which means that the interface bonding between the COOH groups of SA and a-CNTs occurs [32]. The peaks around 2922 cm À1 and 2850 cm À1 are assigned to the stretching vibrations of ACH 3 and ACH 2 groups in SA molecules, respectively.…”

Nanoconfinement of phase change materials within carbon aerogels: phase transition behaviours and photo-to-thermal energy storage

“…1,3-6 Phase change materials can store a large amount of energy at a constant temperature. 8,[15][16][17][18][19][20][21][22][23][24][25][26][27] Furthermore, the volume changes of organic PCMs are subtle when the phase change occurs, which causes less fracture to the container. 5,7,[10][11][12][13][14] Among the large number of phase change materials, organic PCMs have been thoroughly investigated for their large range of practical melting points and a moderate thermal storage density.…”

Facile Preparation of Calcium Stearoyl Lactylate as Solid–Liquid Phase Change Materials with Improved Form Stability and Adjustable Phase Transition Temperature for Thermal Comfort

“…However, compared with PCMs working at 18°C–30°C, SA with relatively high phase transition temperature about 70.8°C is at a disadvantage for thermal comfort applications . In order to tailor SA with specific phase transition temperature, Feldman et al .…”