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Title: Search for liquids electrospraying the smallest possible nanodrops in vacuo

Abstract

Prior work with electrosprays in vacuum of mixtures of ionic liquids (ILs) and the moderately high boiling point (T{sub b}) solvents formamide (FM) and propylene carbonate (PC) (T{sub b} of 210 and 241 °C) has shown that the charged drops produced have reasonably narrow charge/mass distributions, controllable over a wide mass/charge range. This enables their use as propellants in electrical propulsion with specific impulse I{sub sp} varying from a few hundred to a few thousand seconds (10 kV beam energy) and with excellent propulsion efficiency. However, some limitations are imposed by the finite room temperature volatility of FM and PC. Here, we seek improved performance from propellants based on the polar but viscous solvent Sulfolane (SF; ε = 43.2, μ = 10.3 cP) and the low viscosity but less polar solvent tributyl phosphate (TBP; ε = 8.9, μ = 3.4 cP), both with T{sub b} > 280 °C. Neither TBP nor its low viscosity mixtures with SF achieve the electrical conductivities needed to yield high I{sub sp}. Most ILs used in SF/IL mixtures tested were based on the 1-ethyl-3-methylimidazolium (EMI) or 1,3-dimethylimidazolium (DMI) cations, including EMI-BF{sub 4}, EMI-N(CN){sub 2}, and DMI-N(CN){sub 2}. These combinations reach high conductivities, some approaching 3 S/m, but have limited propulsive performance because evaporation of ions directly from the electrifiedmore » meniscus produces undesirable mixed beams of drops and ions. Exceptional characteristics are found in mixtures of SF with ethylammonium nitrate (EAN), where the small EA{sup +} cation is strongly bound to the solvent, greatly delaying ion evaporation from the meniscus. Evidence on the formation of nano-jets with diameters as small as 1 nm is seen. Although unprecedented, this finding agrees with what would be expected if ion evaporation were suppressed. SF/EAN mixtures thus provide the best available sources to produce the smallest possible nanodrops, minimally polluted by ions.« less

Authors:
; ;
Publication Date:
OSTI Identifier:
22402786
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 116; Journal Issue: 22; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BOILING POINTS; CARBONIC ACID ESTERS; ELECTRIC CONDUCTIVITY; FORMAMIDE; MASS DISTRIBUTION; MIXTURES; PERFORMANCE; PROPULSION; TBP; TEMPERATURE RANGE 0273-0400 K

Citation Formats

Alonso-Matilla, R., Fernández-García, J., Congdon, H., and Fernández de la Mora, J., E-mail: juan.delamora@yale.edu. Search for liquids electrospraying the smallest possible nanodrops in vacuo. United States: N. p., 2014. Web. doi:10.1063/1.4901635.
Alonso-Matilla, R., Fernández-García, J., Congdon, H., & Fernández de la Mora, J., E-mail: juan.delamora@yale.edu. Search for liquids electrospraying the smallest possible nanodrops in vacuo. United States. https://doi.org/10.1063/1.4901635
Alonso-Matilla, R., Fernández-García, J., Congdon, H., and Fernández de la Mora, J., E-mail: juan.delamora@yale.edu. 2014. "Search for liquids electrospraying the smallest possible nanodrops in vacuo". United States. https://doi.org/10.1063/1.4901635.
@article{osti_22402786,
title = {Search for liquids electrospraying the smallest possible nanodrops in vacuo},
author = {Alonso-Matilla, R. and Fernández-García, J. and Congdon, H. and Fernández de la Mora, J., E-mail: juan.delamora@yale.edu},
abstractNote = {Prior work with electrosprays in vacuum of mixtures of ionic liquids (ILs) and the moderately high boiling point (T{sub b}) solvents formamide (FM) and propylene carbonate (PC) (T{sub b} of 210 and 241 °C) has shown that the charged drops produced have reasonably narrow charge/mass distributions, controllable over a wide mass/charge range. This enables their use as propellants in electrical propulsion with specific impulse I{sub sp} varying from a few hundred to a few thousand seconds (10 kV beam energy) and with excellent propulsion efficiency. However, some limitations are imposed by the finite room temperature volatility of FM and PC. Here, we seek improved performance from propellants based on the polar but viscous solvent Sulfolane (SF; ε = 43.2, μ = 10.3 cP) and the low viscosity but less polar solvent tributyl phosphate (TBP; ε = 8.9, μ = 3.4 cP), both with T{sub b} > 280 °C. Neither TBP nor its low viscosity mixtures with SF achieve the electrical conductivities needed to yield high I{sub sp}. Most ILs used in SF/IL mixtures tested were based on the 1-ethyl-3-methylimidazolium (EMI) or 1,3-dimethylimidazolium (DMI) cations, including EMI-BF{sub 4}, EMI-N(CN){sub 2}, and DMI-N(CN){sub 2}. These combinations reach high conductivities, some approaching 3 S/m, but have limited propulsive performance because evaporation of ions directly from the electrified meniscus produces undesirable mixed beams of drops and ions. Exceptional characteristics are found in mixtures of SF with ethylammonium nitrate (EAN), where the small EA{sup +} cation is strongly bound to the solvent, greatly delaying ion evaporation from the meniscus. Evidence on the formation of nano-jets with diameters as small as 1 nm is seen. Although unprecedented, this finding agrees with what would be expected if ion evaporation were suppressed. SF/EAN mixtures thus provide the best available sources to produce the smallest possible nanodrops, minimally polluted by ions.},
doi = {10.1063/1.4901635},
url = {https://www.osti.gov/biblio/22402786}, journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 22,
volume = 116,
place = {United States},
year = {Sun Dec 14 00:00:00 EST 2014},
month = {Sun Dec 14 00:00:00 EST 2014}
}