Papers by Author: Cullen R. Buie

Abstract: The present research endeavors to demonstrate the applicability of electrophoretic deposition (EPD) for the infiltration and coating of porous materials to create advanced composites. Motivated by improved materials requirements of tokamak fusion reactors, the composites are created by depositing ceramic nanoparticles in porous metallic matrices using both constant voltage and pulsed DC EPD. Silicon dioxide particles with a nominal diameter of 20 nm are used as inexpensive surrogates for more application-appropriate boron carbide due to their similar surface chemistry. Fabricated materials are characterized using scanning electron microscopy (SEM) and energetic dispersive x-ray spectrometry (EDX) to visualize coating quality and penetration of the material into the substrate. At low voltage, the deposited mass in constant voltage EPD increases linearly with time while at high voltage it asymptotically approaches a maximum yield of 1.988 grams. Pulsed EPD experiments demonstrate a reduction in deposition yield but also elimination of macro-pore generation in the low voltage case. A non-dimensional parameter, ξ*, relating electrokinetics and diffusion is derived which improves process design for pulsed EPD systems.

Abstract: Superhydrophilic surfaces with hydrophobic layers were successfully produced in order to enhance critical heat flux (CHF) and reduce boiling inception temperatures (BIT). The novel surfaces were fabricated by a hybrid electrophoretic deposition (EPD) method coupled with a break down anodization (BDA) process. With the BDA process, microporous superhydrophilic surfaces were created on titanium substrates. Subsequently, nanoporous hydrophobic layers were deposited with EPD on the superhydrophilic surfaces. The hydrophobic layers provide numerous nucleation sites, lowering BIT while the superhydrophilic layers prevent film boiling, resulting in increased CHF. The resulting surfaces exhibit higher CHF with lower BIT than untreated titanium surfaces .