In a recent study, scientists operate a nanoscale satellite ion rocket under a microscope and observe how the tiny rocket works. The finding is published in Nanotechnology.
Researchers from Michigan Technological University, University of Maryland, and Northwestern University conducted the study.
They applied an extreme electric field on the order of 1010 V m−1 to the free surface of an ionic liquid to cause electric-field-induced evaporation of molecular ions from the liquid.
After that, they observed the point of ion emission in situ using a transmission electron microscopy (TEM). TEM is a microscopy technique in which a beam of electrons is transmitted through an ultra-thin specimen, interacting with the specimen as it passes through it.
The resulting electrospray emission process was observed to create nanoscale high-aspect-ratio dendritic features that were aligned with the direction of the electric field.
After the stressing field was removed, the features were seen to remain, which suggested that the ionic liquid residue was solidified or gelled.
Researchers then performed similar electrospray experiments in a field-emission scanning electron microscope, and found that the features were created when the high-energy electron beam damaged the molecular structure of the ionic liquid.
While the electric field did not play a direct role in the fluid modification, the electric stress was critical in detecting the liquid property change.
It is only because the electric stress mechanically elongated the fluid during the electrospray process, and these obviously non-liquid structures persisted when the field was removed.
Researchers suggest that this evidence of ionic liquid radiation damage may have significant bearing on electrospray devices.
It is possible to produce high-energy secondary electrons through surface impacts of emitted ions downstream of the emitter.
Any such impacts that are in close proximity could see reflected secondary electrons impact the emitter causing gelling of the ionic liquid.
Citation: Terhune KJ, et al. (2016). Radiation-induced solidification of ionic liquid under extreme electric field. Nanotechnology, 27: 375701. DOI: 10.1088/0957-4484/27/37/375701.
Figure legend: This Knowridge.com image is credited to Terhune KJ et al.