Investigation of Boiling Performance of Graphene-coated Surfaces

In this Capstone Project, I sought to investigate the boiling performance of graphene-coated surfaces. Boiling was accomplished in a pool boiling chamber, with samples of graphene-coating SiO2 wafers. I developed a procedure for graphene transfer for sample fabrication. Samples were prepared with graphene grown on copper substrates by chemical vapor deposition (CVD). Graphene was transferred from copper substrates to SiO­2 wafers by a thermal release transfer tape. Copper was etched away from the tape-graphene combination by ferric chloride, and the tape was peeled away after heating, leaving graphene on the SiO2 substrate. Contact angles were measured to verify the beneficial hydrophobic properties of the surface, thereby indicating a successful transfer. Raman spectra were taken of the samples at discrete spots to analyze sample quality and uniformity, before and after boiling. Boiling was controlled by a resistance heater on the back of the SiO2 samples, composed of Indium Titanium Oxide (ITO) and two copper electrodes. Samples were epoxied onto a platform in the boiling chamber, and soldered to a power supply. Heat flux was incrementally increased until critical heat flux (CHF) was reached. Experiments found that the boiling process destroyed the bulk of the graphene on the samples, the resulting curves of which reflected both hydrophobic and hydrophilic behavior from the samples. Heat transfer coefficient and CHF of samples were both found to be superior to a blank SiO2 sample, but graphene destruction in the process proves problematic. Furthermore, leakage of water from the tank may have caused an artificially high CHF for one sample. Further investigation of different transfer methods that prevent graphene from leaving the surface is a primary focus of future research