Repetitive Pool Boiling Runs: A Controlled Process to Form Reduced Graphene Oxide Surfaces from Graphene Oxide with Tunable Surface Chemistry and Morphology

Abstract

Wettability and wickability of a surface are the key properties that govern a variety of industrial applications. Understanding the effect of aging on the durability of these surfaces and subsequent changes occurring in their molecular structure is vital to maintain functionality. In this work, we used repetitive pool boiling to test the durability of graphene oxide-copper (GO-Cu) coated surfaces and studied subsequent changes in surface chemistry and morphology. We observed the transformation of GO-Cu to reduced GO-copper (rGO-Cu) coating that led to improved boiling performance. This improvement is attributed to (a) transition of hydrophilic GO to hydrophobic rGO due to the repetitive pool boiling, (b) increased surface roughness as a result of hydrophobic surfaces , and c) increased surface inhomogeneity due to the presence of three elements-carbon, oxygen and copper. The durability of the GO-Cu coatings was found to be higher than pristine-copper and just-copper coated surfaces. A higher performance demonstrated by GO-Cu coatings indicates its increased sustainability and practicability in numerous engineering applications.

Salt templated and graphene nanoplatelets draped copper (GNP-draped-Cu) composites for dramatic improvements in pool boiling heat transfer

“…The change in wetting behavior was observed for the coating after 3 repetitive boiling tests. A similar change in wetting properties was also observed for our previous work 28 involving graphene-based coatings and is attributed to the removal of oxygen groups from graphene due to repetitive boiling. Despite small reduction in the pool boiling performance, strong adhesion between the coating and the substrate was observed.…”

“…Additionally, static wettability and dynamic wicking of sintered surfaces were measured for the surfaces using a VCA Optima Goniometer contact angle measurement instrument. For dynamic wicking, a distilled water droplet of 2 µL was steadily brought into contact with the coated surfaces using a static sessile drop method and liquid propagation was recorded using a high-speed camera 28 .…”

“…We demonstrated this through electrodeposited graphene/copper based composite coatings possessing hierarchical porous network and highly wickable structures that yielded remarkable improvement in pool boiling 24 . Some of the noteworthy work performed in this field that have resulted in very high CHFs includes the use of micro/nanoscale coatings 25 – 27 , altering the heater surface wettability and wickability 28 – 30 , self-assembled structures with nanofluids as working fluids 31 , 32 .…”

Investigation of Structure-Property-Boiling Enhancement Mechanisms of Copper/Graphene Nanoplatelets Coatings

“…We further confirmed the long-term sustainability on microscale coatings by conducting multiple boiling tests that drastically improved heat transfer coefficient. This resulted from the transition of superhydrophilic to superhydrophobic coatings supported by Fourier transform infrared, (FTIR) studies that confirmed the removal of hydroxyl-based functional groups from the surfaces (Rishi et al, 2019a;Rishi et al, 2019b).…”

Effect of Ball Milled and Sintered Graphene Nanoplatelets–Copper Composite Coatings on Bubble Dynamics and Pool Boiling Heat Transfer

“…The distinctive structure of a single layered sp 2 -hybridized carbon atoms endows the thinnest material known as graphene, which has gained an enormous attention in various industrial applications such as surface coatings [1][2][3][4] , electronics [5,6] , energy storage [7,8] , lithium-ion batteries [9][10][11][12] , automotive [13,14] , and aerospace sector [15][16][17] due to its exceptional electrical, thermal, and mechanical properties [18] . Owing to very high thermal conductivity, graphene has also been implemented in thermal interface materials [19,20] , nanofluids [21] , and composite coatings [22][23][24] for heat transfer applications that require high heat flux dissipation [25][26][27][28][29] .…”