Electrospray atomization of liquids in the cone-jet mode generates narrow droplet distributions with average diameters as small as a few nanometers. These droplets are highly charged, and with the help of electrostatic fields can be accelerated to hypervelocities in a vacuum. The resulting energetic beams are useful for spacecraft propulsion (electrospray thrusters) and ion beam-like applications. Electrospray thrusters is a promising electric micropropulsion technology characterized by its ability to produce low thrust levels (as low as a fraction of a microNewton) at high specific impulse and efficiency unrivaled by plasma-discharge thrusters. The speaker will introduce this technology, and describe his own research on the structure and shaping of electrospray thruster beams. The second part of the seminar will introduce the phenomenology of nanodroplet impact on hard crystalline materials such as Si and SiC. Compared to ions, nanodroplets are massive particles of neutral molecules (e.g. ~153,000 molecules) with several elementary charges. Acceleration voltages below 20 kV produce kinetic energies of tens of eV per molecule. When such massive projectiles impact on a target they sputter atoms at high rate and, depending on the impact velocity, will amorphatize thin substrate layers.
Energetic Beams of Electrosprayed Nanodroplets: Applications in Spacecraft Propulsion and Surface Engineering
Monday, April 29, 2013
Manuel Gamero (UC Irvine, USA)
EBUII, ROOM 479
3:00 to 4:00