Effect of a homogeneous magnetic field on the electrospraying characteristics of sulfolane ferrofluids

Abstract

We explore the effect of an applied homogeneous magnetic field on the electrospraying characteristics of a ferrofluid in the cone-jet mode. A sulfolane-based ferrofluid mixed with the ionic liquid ethyl ammonium nitrate has been synthesized. These mixtures have negligible volatility under ambient conditions and remain stable under a very wide range of electrical conductivities $K$. Magnetized Taylor cones spray with the same current emission characteristics as their non-magnetized counterparts in the shared voltage and flow rate parameter space. However, the magnetized Taylor cones studied remained stable at voltages 23 % lower than the non-magnetized spray; they also access flow rates 30 % and 40 % lower in ferrofluids with $K=0.3$ and $0.01~\text{S}~\text{m}^{-1}$. In the lower voltage ranges available only to magnetized tips, unusually long stable cones are observed. The magnetic stabilization mechanism responsible for these two effects remains unclear. It is noteworthy that these strong effects arise even when the tip curvature of the strictly magnetized liquid is orders of magnitude smaller than that for the strictly electrified liquid.

The effects of magnetic surface stress on electrospray of an ionic liquid ferrofluid

“…The percentage of flowrate reduction was dependent on the amount of nanoparticles in the solution with a maximum of 43 percent reduction compared to the zero-magnetic-fieldminimum flowrate, when using a solution with 14.15 wt% nanoparticles. The reduction of the minimum flowrate aligns with studies on low-conductivity Sulfolane ferrofluids, 31 and should be further investigated to realize the interaction mechanism between the magnetic field and the high-conductivity ferrofluids.…”

“…Two forms of ILFF electrosprays have been studiedelectrospray from a "needle-free" ILFF peak formed by the Rosensweig instability, and electrospray from a capillary needle with and without an applied magnetic field. 31 Electrosprays from the Rosensweig instability have been produced from a single peak, 22,23,32 and an array of five peaks. [20][21][22] In each of these electrospray studies, dark residue on the extraction electrode revealed evidence of the magnetic nanoparticles.…”

“…Madden et al also observed that the addition of a magnetic field extends the stability range of flowrates, currents, and voltages for ILFF electrosprays which theoretically enables the production of smaller droplets. 31 American Institute of Aeronautics and Astronautics 4…”

“…Madden et al observed similar effects in their work with low-conductivity ferrofluids. 31 In their work two sulfolane ferrofluid solutions were used, one with 15% (v/v) ethyl ammonium nitrate (EAN), and the other with 0.1% (v/v) EAN. With the application of a 300-Gauss magnetic field they saw a significant expansion of the operational range of the electrospray.…”

Species measurements in the beam of an ionic liquid ferrofluid capillary electrospray source under magnetic stress

“…Two forms of ILFF electrosprays have been studied -electrospray from a "needle-free" ILFF peak formed by the Rosensweig instability, and electrospray from a capillary needle with and without an applied magnetic field. 21 Electrosprays from the Rosensweig instability have been produced from a single peak, 13,20,22 and arrays of five, 10,11,20 seven, 23 and eight 23 peaks. In each of these electrospray studies, visual inspection of the residue from electrospray emission onto the extraction electrode revealed evidence of the magnetic nanoparticles.…”