Thermal Interface Engineering Using Layer-By-Layer Carbon Nanotube-Polyethylenimine Functional Nanostructures between Phase Change Materials and Aluminum Heat Sinks

Phase change materials (PCMs) and heat sinks (HSs) can be integrated rationally to complement the inherent constraints of both technologies. However, adding PCMs to HSs frequently causes additional thermal resistances and unstable contact interfaces during solid-liquid phase transitions. In this study, we present the utilization of layer-by-layer (LbL) assembly to enhance functional interfaces between a multiwalled carbon nanotube (MWCNT) and polyethyleneimine (PEI) on the surfaces of PCMs and HSs to enhance thermal management capabilities. The MWCNT-PEI percolation networks on an aluminum HS are effectively created by the LbL approach reported in this study, which involves the direct synthesis of electrostatically attached nanocoatings using a solution-based process. The HS channels are filled with a phase change substance (n-eicosane) to complete the PCM-HS assembly. The PCM and HS interface is stabilized over repeated solid-liquid phase transitions owing to the functional interface's optimization of the porous structures and a large increase in the active surface area enabling effective thermal transport. A comparison between the developed specimens (bare and PCM-filled HSs without LbL interfaces) highlights the improved thermal performance, particularly in transient and static operating conditions. The LbL functional interfaces show lower temperatures than the PCM-HS without MWCNT-PEI bilayers under different thermal loads (30, 40, and 50 W). The set point temperatures (SPTs) are chosen to be 40°C, 50°C, and 60°C for an objective and precise comparison. The LbL-assembled MWCNT–PEI coatings considerably increase the times to reach all SPTs. Using the LbL interface improves the effectiveness by more than 10%, according to experimental assessments of real-time temperature responses under different heating power levels and the time required to reach target temperatures. Furthermore, the LbL interfaces effectively mitigate thermal shock and overload issues during intermittent thermal loads. The developed LbL interface presents a versatile and scalable approach for creating PCM-filled HSs with advanced thermal properties that surpass the capabilities of traditional heat sinks.