COLL 512 |
| Michael J. Tarlov1, O. C. Thomas1, K. M. Balss1, and Richard Cavicchi2. (1) Chemical Science & Technology Laboratory, National Institute of Standards and Technology, NIST, Gaithersburg, MD 20899, (2) Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD |
| This talk will describe studies of micro-boiling phenomena on the surfaces of rapidly heated thin film heaters. Alkanethiol monolayers are self-assembled on heater surfaces to investigate the effect of surface wettability on micro-boiling behavior. The heaters are thin films of platinum or gold-plated platinum with dimensions of approximately 5 x 200 microns. The micro-heaters are immersed in solutions where they are rapidly heated to high temperature with short (5ms – 40ms), square voltage pulses. The temperature-time responses of the micro-heaters are obtained by measuring their resistance during the application of the heating pulse. The bubble nucleation event associated with boiling is signaled in the temperature-time transient by an inflection point that results from a change in heat transfer when a vapor bubble forms on the heater. Because of the extremely high heating rates, superheating is observed where nucleation temperatures near 300°C have been measured in water. We will demonstrate that temperature-time transients of hydrophobic SAMs are distinct from those of hydrophilic SAMs and that information on SAM stability and interfacial hydration can be gleaned from the transients. |
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Adamson Award Symposium Honoring Dave Allara and Ralph Nuzzo
Division of Colloid and Surface Chemistry |