Layer-by-layer self-assembled functional coatings of carbon nanotube-polyethylenimine for enhanced heat transfer of heat sinks

Abstract

Multi-functional porous coatings are promising candidates to improve overall heat transfer performances of heat sinks that are essential for thermal management of various electronic devices and mobility platforms. However, owing to the intrinsic limitations of the heat sinks comprising of the high-aspect-ratio fin-like structures, fabricating functional coatings involves complex process which incurs high-cost and long-time process. Herein, we report tunable and scalable layer-by-layer (LbL) self-assembly of multi walled carbon nanotube (MWCNT)-polyethyleneimine (PEI) coatings on aluminum heat sinks for enhanced transient and static heat transfer performances. The repetitive immersing and rinsing of the negatively and positively charged solutions with carboxylic group-functionalized MWCNTs and PEI led to the electrostatic deposition of the LbL self-assembled MWCNT-PEI coatings on the aluminum heat sinks. All LbL coatings (50-250 nm in thickness) employing the fiber-like percolation networks of MWCNTPEI could induce the morphological transition like the increased surface roughness while the black-like surface from carbon elements might provide the increased emissivity for the aluminum heat sinks. The multifunctional characteristics of the MWCNT-PEI coatings reinforced active surface area, fluid mixing and surface emissivity of the bare heat sink, thereby achieving the enhanced heat transfer coefficient ( similar to 19%) and thermal resistance (16%). The optimal design of the porous coatings according to variation in applied thermal energy was elucidated by the comparable analysis between 10, 20, and 30 bilayers of the LbL MWCNT-PEI coatings. The developed LbL coatings can pave the way for effectively mitigating thermal shock or overload in transient and static operating conditions for a wide range of applications involving thermal energy dissipation. (c) 2021 Elsevier Ltd. All rights reserved.