AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Synthesis of Nanostructured Metal Oxide Films by Electrospray Deposition of Nanoparticles
JUSTIN TANG, Alessandro Gomez, Yale University
Abstract Number: 352 Working Group: Nanoparticles and Materials Synthesis
Abstract We present here the use of the electrospray (ES) to create high surface area, metal oxide nanoparticle-based films for applications in energy conversion and energy storage. Although the particle can be synthesized directly by spray pyrolysis, the technique implemented in the present approach involves electrospraying a colloidal suspension with a conductive and volatile solvent and depositing nanoparticles onto a selected substrate in a continuous and controlled manner, after solvent evaporation. The suspension is sufficiently dilute so that one nanoparticle is present, on average, per droplet generated by the electrospray. The deposition of the nanoparticle is governed by the relative importance of the charged particle drift imposed by the external electric field and the thermal velocity due to Brownian motion. The deposition mechanics can be expressed in terms of a single parameter: the ratio of the terminal velocity to the thermal velocity. While the thermal velocity is a function of the nanoparticle size, the external field can be independently manipulated. Zinc oxide and titania films of several microns thick were synthesized by this ES route, and cross sectional SEM images revealed morphological differences between low and high speed ratio deposition conditions. We found that low-speed ratio deposits have dendritic structures and high-speed ratios have columnar structures. Ellipsometry measurements show that the films are highly porous. Importantly, the small throughput for a single electrospray can be scaled up through multiplexing. As a result, the technique can meet the deposition rates that are needed in applications. This approach to thin film synthesis provides control over thickness and morphology and does not necessitate a clean room facility.