A Multiscale Morphological Insight into Graphene Based Coatings for Pool Boiling Applications

ABSTRACT

The application of graphene for pool boiling is an attractive option to facilitate compaction and promote efficient heat removal from high power density devices. In this context, chemical characterization of the depositions achieved through commonly employed coating techniques are an important topic of discussion. A detailed structure-property relationship between the morphologies obtained on the mono and multilayered graphene coatings and their corresponding pool boiling performance quantified by the experimental critical heat fluxes is presented. Three different types of graphene (G) and graphene oxide (GO) substrates are characterized: (i) nanoscale: mono and multilayer samples developed through chemical vapor deposition, (ii) Rochester Institute of Technology (RIT)-G/GO colloid generated through an oxygen embrittlement electrochemical process, and (iii) commercially available chemical vapor deposited (CVD)-G/GO colloid. The morphological features were characterized with scanning electron microscope while X-Ray Diffractometer analysis and Raman spectroscopy were used to examine the ordering and stacking of the sheets that result in the unique structural features. Fourier transform infrared and energy dispersive X-ray spectroscopy were employed to identify the overall compositional characteristics of the coated surfaces. The wettability changes and additional nucleation sites for nanoscale coatings, and multiscale roughness features and ridge microstructures for microscale coatings were identified as enhancement mechanisms.

Acknowledgments

This work was conducted in the Soft Nanomaterials Laboratory, Department of Chemical Engineering and the Thermal Analysis, Microfluidics and Fuel Cell Laboratory in the Mechanical Engineering Department at Rochester Institute of Technology, Rochester, NY. The authors gratefully acknowledge the financial support provided by the National Science Foundation under CBET Award No. 1335927.

Nomenclature

<A>	=	Average scattered amplitude
CHF	=	Critical heat flux
CVD	=	Chemical vapor deposition
DLS	=	Dynamic Light Scattering
Ē	=	Applied electric field
EDS	=	Energy dispersive –X-ray spectroscopy
FTIR	=	Fourier transform infrared spectroscopy
G	=	Graphene
GO	=	Graphene oxide
n	=	Refractive index of the medium
RIT	=	Rochester Institute of Technology
SEM	=	Scanning Electron Microscopy
T	=	time
TGA	=	Thermogravimetric analysis
XRD	=	X-ray diffraction

Greek symbols

μEP	=	Electrophoretic mobility
φ	=	Phase shift of the scattered light
λ	=	Wavelength of the light
θ	=	Scattering angle

Additional information

Notes on contributors

Anju Gupta

Anju Gupta is an Assistant Professor in the Chemical Engineering program and Principal Investigator of the Soft Nanomaterials Laboratory at Rochester Institute of Technology. Her research interests include formation of microemulsions, self-assemblies, nanostructured composites and their characterization using thermal analysis (DSC, TGA) and electron microscopy (cryogenic SEM and TEM) techniques for biomedical and environmental applications.

Arvind Jaikumar

Arvind Jaikumar is a Ph.D. candidate in the microsystems engineering department at Rochester Institute of Technology (RIT). He obtained his Bachelor's degree in mechanical engineering from Visvesvaraya Technological University, India. He received his Master of Science degree in mechanical engineering from RIT with a specialization in thermal and fluids engineering. He is currently engaged in creating multiscale structures for enhanced pool boiling heat transfer.

Satish G. Kandlikar

Satish G. Kandlikar has been at Rochester Institute of Technology since 1980 and is currently the Gleason Professor of Mechanical Engineering. He received his Ph.D. degree from the IIT Bombay in 1975. He has worked extensively in the area of flow boiling and CHF phenomena at microscale, single-phase flow in microchannels, electronics cooling, and water management in PEM fuel cells. He has published over 400 journal and conference papers. He is the recipient of the 2012 ASME Heat Transfer Memorial Award. His recent work on pool and flow boiling has produced exceptionally high heat fluxes along with very high heat transfer coefficients.

Aniket Rishi

Aniket Rishi is currently pursuing his Master's Degree in the Thermal Analysis Microfluidics and Fuel Cell Laboratory at Rochester Institute of Technology. He completed his Bachelor's degree in Mechanical Engineering from MITCOE, Pune, India. He is currently working on enhancing the heat transfer performance using different electrochemical deposition methods.

Andrew Layman

Andrew Layman is currently finishing up his bachelors in Chemistry at Rochester Institute of Technology (RIT). He will continue at RIT to pursue his Master of Science in Materials Science. He is currently engaged in the creation/study of liposomes and their interaction with prescription drugs.