Ionic liquid ion sources: suppression of electrochemical reactions using voltage alternation

Lozano, Paulo; Martı́nez-Sánchez, Manuel

doi:10.1016/j.jcis.2004.07.037

Cited by 134 publications

(76 citation statements)

References 16 publications

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“…This result is in keeping with previous studies where voltage alternation alone, without other means to ensure balanced charge, was shown to suppress electrochemical reactions with EMI-BF 4 [44].…”

Section: Potential Alternation Schemesupporting

confidence: 92%

“…Emissions from ILIS are known to decay over time [44], particulary at constant emitter polarity. These reductions can, in part, be attributed to electrochemical breakdown of IL at the liquid-conductor interface [45].…”

Section: Potential Alternation Schemementioning

confidence: 99%

“…These reductions can, in part, be attributed to electrochemical breakdown of IL at the liquid-conductor interface [45]. To suppress these reactions the potential is typically alternated to prevent sufficient charge accumulation at the interface for charge transfer to occur [33,44]. Further work has indicated the efficacy of this method may be augmented when using a distal electrode [46], a scheme intrinsically implemented when using porous glass emitters as done here.…”

Section: Potential Alternation Schemementioning

confidence: 99%

“…Figure 18 provides an example of the decrease in emitted current before and after direct thrust measurements at ESTEC and subsequently after ToF measurements at EPFL. It is tempting to broadly attribute this behavior to degradation due to electrochemical reactions at the ionic liquid to guard ring contact interface [2,44]. We have followed the most recent recommendations in the literature whenever possible: use of a the glass emitter substrate enforces a distal electrical contact [46] and attempts were made to balance positive and negative emission charge transfer over each period of potential alternation during thrust measurements [33,50].…”

Section: Emission Decay and Longevitymentioning

confidence: 99%

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Comparing Direct and Indirect Thrust Measurements from Passively Fed Ionic Electrospray Thrusters

Courtney

Dandavino

Shea

2016

Journal of Propulsion and Power

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Highly ionic beams of several hundred μA per cm 2 have been measured from porous glass ionic liquid electrospray sources fabricated using a conventional mill. The thrust output from three prototype devices, two emitting the ionic liquid EMI-Im and one emitting EMI-BF 4, was measured directly using a precise balance. Thrusts up to 50 μN were measured when emitting EMI-Im in a bipolar, alternating potential configuration at less than 0.8 W input power and with propellant supplied from an internal reservoir. Measurements of mass spectra via Time of Flight spectrometry, angle resolved current distributions, ion fragmentation and energy deficits have been applied to accurately calculate thrust and mass flow rates indirectly from the same devices. For two of three cases, calculated and directly measured thrusts were in agreement to within a few μN at input powers from 0.1 W to 0.8 W . Emissions of EMI-BF4 are shown to yield nearly purely ionic beams supporting high propulsive efficiencies and specific impulses, ∼ 65 % and > 3200 s respectively at 0.5 W . Conversely, greater polydispersity was observed in EMI-Im emissions, contributing to reduced specific performance, ∼ 50 % propulsive efficiency and ∼ 1500 s specific impulse at 0.5 W .

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Section: Potential Alternation Schemesupporting

confidence: 92%

Section: Potential Alternation Schemementioning

confidence: 99%

Section: Potential Alternation Schemementioning

confidence: 99%

Section: Emission Decay and Longevitymentioning

confidence: 99%

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Comparing Direct and Indirect Thrust Measurements from Passively Fed Ionic Electrospray Thrusters

Courtney

Dandavino

Shea

2016

Journal of Propulsion and Power

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“…22 Electrospray of the stable IL emim + /BF 4 -has been proposed for use as a highly controllable microthruster. [23][24][25] Room temperature ionic liquids are normally considered chemically and thermally stable, because they are often based on the imidazolium or other stable cations, and may also contain nearly inert perfluoro anions. However, it is of interest to consider chemically unstable ionic liquids, 26 which may have interesting applications.…”

Section: Introductionmentioning

confidence: 99%

Triazolium-Based Energetic Ionic Liquids

2005

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The energetic ionic liquids formed by the 1,2,4-triazolium cation family and dinitramide anion are investigated by ab initio quantum chemistry calculations, to address the following questions: How does substitution at the triazolium ring's nitrogen atoms affect its heat of formation, and its charge delocalization? What kind of ion dimer structures might exist? And, do deprotonation reactions occur, as a possible first step in the decomposition of these materials? The energetic ionic liquids formed by the 1,2,4-triazolium cation family and dinitramide anion are investigated by ab initio quantum chemistry calculations, to address the following questions: How does substitution at the triazolium ring's nitrogen atoms affect its heat of formation, and its charge delocalization? What kind of ion dimer structures might exist? And, do deprotonation reactions occur, as a possible first step in the decomposition of these materials? Disciplines

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Electrospray Propulsion

Lozano¹,

Martı́nez-Sánchez²,

Hruby³

2010

Encyclopedia of Aerospace Engineering

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Micro-propulsion has been studied for many years due to its applications in small-tomedium sized spacecraft for precise satellite attitude control. Electrospray thrusters are promising thrusters built upon the state of the art in micro-technology and with flexible performance in terms of their high efficiency and high specific impulse. One challenge is to investigate in detail the mechanism for ion emission to complement experimental results and understand better how emission occurs in the micro to nano scale. Thus, atomistic modeling is used to understand properties of emitted charged particles which determine how the thrusters perform.As a preliminary study of ion emission from Taylor cones, ion evaporation from 3 -5 nm droplets was observed in molecular dynamics (MD) simulations to validate the atomistic modeling and to investigate activation energies. Ion emission was examined in terms of internal and external electric fields and the activation energies of each case were obtained using Schottky's model and direct energy calculation to compare with experimental values. Ion emission was mainly observed with electric field strengths between 1.2 -2.0 V/nm and the emitted species include both solvated and non-solvated ions. Propulsive properties from Taylor cones are examined using results from the analysis of electric current from ion emission.In addition to an observation of ion emission from liquid droplets, numerical simulations for interactions between a solid plate and liquid droplets were conducted with MD simulation. It was concluded that another selection of force field needs to be considered to pursue further details, such as electrochemical effects.

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Ionic liquid ion sources: suppression of electrochemical reactions using voltage alternation

Cited by 134 publications

References 16 publications

Comparing Direct and Indirect Thrust Measurements from Passively Fed Ionic Electrospray Thrusters

Comparing Direct and Indirect Thrust Measurements from Passively Fed Ionic Electrospray Thrusters

Triazolium-Based Energetic Ionic Liquids

Electrospray Propulsion

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