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Ion evaporation from Taylor cones of propylene carbonate mixed with ionic liquids

Published online by Cambridge University Press:  30 October 2007

I. GUERRERO ,
R. BOCANEGRA ,
F. J. HIGUERA  and
J. FERNANDEZ DE LA MORA
I. GUERRERO
Affiliation:
Yale University, Mechanical Engineering, New Haven, CT 06520-8286, USA
R. BOCANEGRA
Affiliation:
Yale University, Mechanical Engineering, New Haven, CT 06520-8286, USA
F. J. HIGUERA
Affiliation:
E. T. S. Ingenieros Aeronáuticos, UPM, Pza. Cardenal Cisneros 3, 28040 Madrid, Spain
J. FERNANDEZ DE LA MORA
Affiliation:
Yale University, Mechanical Engineering, New Haven, CT 06520-8286, USA
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Abstract

A combined experimental and numerical approach is used to extract information on the kinetics of ion evaporation from the region of high electric field around the tip of a Taylor cone of the neutral solvent propylene carbonate (PC) mixed with two ionic liquids. On the numerical side, the electric field on the surface of the liquid is computed in the absence of evaporation by solving the electrohydrodynamic problem in this region within the framework of the leaky dielectric model. These computations justify the approximate (2% max error) scaling Emax = β Ek for the maximum electric field on the surface, with Ek = γ1/2 ϵ0−2/3 (K/Q)1/6 for 0.111 < K < 0.888 S m−1 and a numerical value of β ≈ 0.76. Here γ is the surface tension of PC, ϵ0 is the electrical permittivity of vacuum, and K and Q are the liquid electrical conductivity and flow rate. On the experimental side, 16 different propylene carbonate solutions with either of the ionic liquids 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF4) or EMI-bis(trifluoro-methylsulfonyl)imide (EMI-Im) are electrosprayed in a vacuum from a single Taylor cone, and their emissions of charged drops and ions are analysed by time-of-flight mass spectrometry at varying liquid flow rates Q. The sprays contain exclusively drops at large Q, both for small and for large electrical conductivities K, but enter a mixed ion–drop regime at sufficiently large K and small Q. Interestingly, the mixtures containing 10% and 15% (vol) EMI-Im exhibit no measurable ion currents at high Q, but approach a purely ionic regime (almost no drops) at small Q. The charge/mass ratio for the drops produced in these two mixtures increases continuously with decreasing Q, and gets very close to ionic values. Measured ion currents are represented versus computed maximum electric fields Emax on the liquid surface to infer ion evaporation kinetics. Comparison of measured ion currents with predictions from ion evaporation theory yields an anomalously low activation energy (~1.1 eV). This paradox appears to be due to alteration of the pure conj–eet electric field in the scaling laws used for the pure cone–jet regime, due to the substantial ion current density arising even when the ion current is relatively small. Elimination of this interference would require future ion current measurements in the 10–100 pA level. The electrical propulsion characteristics of the emissions from these liquids are determined and found to be excellent, particularly for 10% and 15% (vol) EMI-Im.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 591 , 25 November 2007 , pp. 437 - 459
Copyright
Copyright © Cambridge University Press 2007

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References

REFERENCES

Barrero, A., Gañán-Calvo, A. M., Dávila, J., Palacios, A. & Gómez-González, E. 1999 The role of the electrical conductivity and viscosity on the motions inside Taylor cones. J. Electrostatics 47, 13–26.CrossRefGoogle Scholar
Barrero, A., Lopez-Herrera, J. M., Boucard, A., Loscertales, I. G. & Marquez, M. 2004 Steady cone–jet electrosprays in liquid insulator baths. J. Colloid Interface Sci. 272, 104–108.CrossRefGoogle ScholarPubMed
Bocanegra, R., Fernandez de la Mora, J. & Gamero-Castaño, M. 2004 Ammonium electrolytes quench ion evaporation in colloidal propulsion. J. Propulsion Power 20, 728–735.CrossRefGoogle Scholar
Carretero, J. A. 2005 Numerical simulation of a single emitter colloid thruster in pure droplet cone–jet mode. PhD Thesis, MIT.Google Scholar
Chen, D.-R. & Pui, D. Y. H. 1997 Experimental investigation of scaling laws for electrospraying: dielectric constant effect. Aerosol Sci. Technol. 27, 367–380.CrossRefGoogle Scholar
Cherney, L. T. 1999 Structure of Taylor cone–jets: limit of low flow rates. J. Fluid Mech. 378, 167–196.CrossRefGoogle Scholar
Cloupeau, M. & Prunet-Foch, B. 1989 Electrostatic spraying of liquids in cone–jet mode. J. Electrostatics 22, 135–159.CrossRefGoogle Scholar
Cloupeau, M. & Prunet-Foch, B. 1990 Electrostatic spraying of liquids. Main functioning modes. J. Electrostatics 23, 165–184.CrossRefGoogle Scholar
Cloupeau, M. & Prunet-Foch, B. 1994 Electrohydrodynamic spraying functioning modes: a critical review. J. Aerosol Sci. 25, 1021–1036.CrossRefGoogle Scholar
Cook, K. D. 1986 Electrohydrodynamic mass-spectrometry. Mass Spectrometry Rev. 5, 467–519.CrossRefGoogle Scholar
Espina-Trigo, M. A. 2004 Proyecto de Fin de Carrera (Senior Thesis). Polytechnical University, Madrid (Escuela Tecnica Superior de Ingenieros Aeronáuticos).Google Scholar
Fenn, J. B., Mann, M., Meng, C. K., Wong, S. K. & Whitehouse, C. 1989 Electrospray ionization for mass spectrometry of large biomolecules. Science 246, 64–71.CrossRefGoogle ScholarPubMed
Fernandezde la Mora, J. de la Mora, J. 2007 The fluid dynamics of Taylor cones. Annu. Rev. Fluid Mech. 39, 217–243.CrossRefGoogle Scholar
Fernandezde la Mora, J. de la Mora, J. & Loscertales, I. G. 1994 The current emitted by highly conducting Taylor cones. J. Fluid Mech. 260, 155–184.Google Scholar
Fernandezde la Mora, J. de la Mora, J., Navascués, J., Fernández, F. & Rosell-Llompart, J. 1990 Generation of submicron monodisperse aerosols in electrosprays. J. Aerosol Sci. 21, S673–S676.CrossRefGoogle Scholar
Fernandezde la Mora, J. de la Mora, J., Thomson, B. & Gamero-Castaño, M. 2005 Tandem mobility mass spectrometry study of electrosprayed Heptyl4N+Br− clusters. J. Am. Soc. Mass Spectrom., 16, 717–732.CrossRefGoogle Scholar
Gamero-Castaño, M. & Fernandezde la Mora, J. de la Mora, J. 2000 a Direct measurement of ion evaporation kinetics from electrified liquid surfaces. J. Chem. Phys. 113, 815–832.CrossRefGoogle Scholar
Gamero-Castaño, M. & Fernandezde la Mora, J. de la Mora, J. 2000 b Kinetics of small ion evaporation from the charge and size distributions of multiply charged electrospray clusters. J. Mass Spectrometry 35, 790–803.3.0.CO;2-7>CrossRefGoogle Scholar
Gamero-Castaño, M. & Hruby, V. 2001 Electrospray as a source of nanoparticles for efficient colloid thrusters. J. Propulsion Power 17, 977–987.CrossRefGoogle Scholar
Gamero-Castaño, M. & Hruby, V. 2002 Electric measurements of charged sprays emitted by cone–jets. J. Fluid Mech. 459, 245–276.CrossRefGoogle Scholar
Gañán-Calvo, A. 1997 cone–jet analytical extension of Taylor's electrostatic solution and the asymptotic universal scaling laws in electrospraying. Phys. Rev. Lett. 79, 217–220.CrossRefGoogle Scholar
Gañán-Calvo, A. M. 1999 The surface charge in electrostatic spraying: its nature and its universal scaling laws. J. Aerosol Sci. 30, 863–872.CrossRefGoogle Scholar
Gañán-Calvo, A. M. 2004 On the general scaling theory for electrospraying. J. Fluid Mech. 507, 203–212.CrossRefGoogle Scholar
Gañán-Calvo, A. M., Dávila, J. & Barrero, A. 1997 Current and droplet size in the electrospraying of liquids. Scaling laws. J. Aerosol Sci. 28, 249–275.CrossRefGoogle Scholar
Higuera, F. J. 2003 a Flow rate and electric current emitted by a Taylor cone. J. Fluid Mech. 484, 303–327.CrossRefGoogle Scholar
Higuera, F. J. 2003 b Ion evaporation from the surface of a Taylor cone. Phys. Rev. E 68, 016304.Google ScholarPubMed
Higuera, F. J. 2004 Liquid flow induced by ion evaporation in an electrified meniscus. Phys. Rev. E 69, 066301.CrossRefGoogle Scholar
Huberman, M. N. 1970 Measurement of the energy dissipated in the electrostatic spraying process. J. Appl. Phys. 41, 578–584.CrossRefGoogle Scholar
Huberman, M. N. & Rosen, S. G. 1974 Advanced high-thrust colloid sources. J. Spacecraft 11, 475–480.CrossRefGoogle Scholar
Iribarne, J. V. & Thomson, B. A. 1976 On the evaporation of small ions from charged droplets. J. Chem. Phys. 64, 2287–2294.CrossRefGoogle Scholar
Ku, B. K. & Fernandez de la Mora, J. 2004 Ion evaporation kinetics of tetra-alkylammonium salts in formamide solution. J. Phys. Chem. B 108, 14915–14923.CrossRefGoogle Scholar
Landau, L. D. & Lifshitz, E. M. 1960 Electrodynamics of Continuous Media, Chap. 2. Pergamon.Google Scholar
Loscertales, I. G. & Fernandez de la Mora, J. 1995 Experiments on the kinetics of field-evaporation of small ions from droplets. J. Chem. Phys. 103, 5041–5060.CrossRefGoogle Scholar
Lozano, P. 2003 Studies on the ion-droplet mixed regime in colloid thrusters. PhD Thesis, MIT.Google Scholar
Lozano, P. & Martinez-Sanchez, M. 2005 Ionic liquid ion sources: characterization of externally wetted emitters. J. Colloid Interface Sci. 282, 415–421.CrossRefGoogle ScholarPubMed
Martinez-Sanchez, M., Fernandez de la Mora, J., Hruby, V, Gamero-Castaño, M. & Khayms, V. 1999 Research on colloid thrusters. 26th Intl Electric Propulsion Conference, Kitakyushu, Japan, pp. 93–100. Electric Rocket Propulsion Society.Google Scholar
McEwen, A. B., Ngo, H. L., LeCompte, K. & Goldman, J. L. 1999 Nonaqueous electrolytes for electrochemical capacitors: Imidazolium cations and inorganic fluorides with organic carbonates. J. Electrochem. Soc. 146, 1687–1995.CrossRefGoogle Scholar
Notz, P. K. & Basaran, O. A. 1999 Dynamics of drop formation in an electric field. J. Colloid Interface Sci. 213, 218–237.CrossRefGoogle ScholarPubMed
Perel, J., Mahoney, J. F., Moore, R. D. & Yahiku, A. Y. 1969 Research and development of a charged-particle bipolar thruster. AIAA J. 7, 507–511.CrossRefGoogle Scholar
Prewett, P. D. & Mair, G. L. R. 1991 Focused Ion Beams from LMIS. Wiley.Google Scholar
Reznik, S. N., Yarin, A. L., Theron, A. & Zussman, E. 2004 Transient and steady shapes of droplets attached to a surface in a strong electric field. J. Fluid Mech. 516, 349–377.CrossRefGoogle Scholar
Riddick, J. A., Bunger, W. B. & Sakano, T. K. 1986 Organic Solvents, Vol. 11, 4th Edn, Wiley.Google Scholar
Romero-Sanz, I., Aguirre-de-Carcer, I. & Fernandezde la Mora, J. de la Mora, J. 2005 Ionic propulsion based on heated Taylor cones of ionic liquids. J. Prop. Power 21, 239–242.CrossRefGoogle Scholar
Romero-Sanz, I., Bocanegra, R., Fernandezde la Mora, J. de la Mora, J. & Gamero-Castaño, M. 2003 Source of heavy molecular ions based on Taylor cones of ionic liquids operating in the pure ion evaporation regime. J. Appl. Phys. 94, 3599–3605.CrossRefGoogle Scholar
Romero-Sanz, I. & Fernandez, de la Mora. J. 2004 Spatial structure and energy distribution of electrosprays of ionic liquids in vacuo. J. Appl. Phys. 95, 2123–2129.CrossRefGoogle Scholar
Rosell-Llompart, J. & Fernandezde la Mora, J. de la Mora, J. 1994 Generation of monodisperse droplets 0.3 to 4 μm in diameter from electrified cone–jets of highly conducting and viscous liquids. J. Aerosol Sci. 25, 1093–1119.CrossRefGoogle Scholar
Saville, D. A. 1997 Electrohydrodynamics: The Taylor-Melcher leaky dielectric model. Annu. Rev. Fluid Mech. 29, 27–64.CrossRefGoogle Scholar
Taylor, G. I. 1964 Disintegration of water drops in an electric field. Proc. R. Soc. Lond. A 280, 383–397.Google Scholar
Zeleny, J. 1917 Instability of electrified liquid surfaces. Phys. Rev. 10, 1–6.CrossRefGoogle Scholar