Microscopic analysis for water stressed by high electric fields in the prebreakdown regime

Abstract

Analysis of the electrical double layer at the electrode-water interface for voltages close to the breakdown point has been carried out based on a static, Monte Carlo approach. It is shown that strong dipole realignment, ion-ion correlation, and finite-size effects can greatly modify the electric fields and local permittivity (hence, leading to optical structure) at the electrode interface. Dramatic enhancements of Schottky injection, providing a source for electronic controlled breakdown, are possible. It is also shown that large pressures associated with the Maxwell stress tensor would be created at the electrode boundaries. Our results depend on the ionic density, and are in keeping with recent observations. A simple, perturbative analysis shows that high field regions with a sharp variation in permittivity can potentially be critical spots for instability initiation. This suggests that the use of polished electrodes, or composite materials, or alternative nonpolar liquids might help enhance high-voltage operation.

Microbubble-based model analysis of liquid breakdown initiation by a submicrosecond pulse

“…35 This effectively leads to electric-field enhancements arising from a positive feedback mechanism, since permittivity decreases with increasing electric field. The cross sections were assumed to be rectangular, with a 200-m distance between the point and plane electrodes, in keeping with the experimental setup within our group.…”

“…Exact analysis of streamer growth based on such thermal conversion of electron energy requires Monte Carlo calculations as performed elsewhere for water by our group. 35 ͑iii͒ Continuous field-assisted electron emission from the streamer tip contributes to filamentary growth and propagation. This process would mainly be operative for anode-side streamers.…”

“…35 The MC scheme is used here to furnish the relevant transport parameters for a continuum model based on the drift-diffusion scheme. Basically, electrons in liquid water undergo energy-dependent scattering that can be either elastic, inelastic ionization, or inelastic excitation.…”

“…In our analysis, the energy-dependent cross sections were parametrized based on a recent data report, 36 and discussed in detail previously. 35 Monte Carlo simulations were carried out by injecting a swarm of 8000 particles into the microbubble at the gasliquid interface for a given electric field. As a result, characteristics of the electron dynamics through the gas bubble, followed by their traversal in water, were obtained.…”

The influence of excluded volume and excess ion polarisability on the capacitance of the electric double layer

“…With regards the large Stern layer width required for the fit, we note that it is not the width, but the ratio h/ε S , that determines the effect of the Stern layer. Solvent molecules at an interface may be strongly aligned with the surface [38,39], reducing the permittivity in the Stern layer, and accounting for this would lead to a smaller March 15, 2016 Molecular Physics planar-submit2 width necessary to fit the data. Regarding the deviation of the model from the measurement at high concentrations, we recall that this form of the polarizability interaction model, in which the permittivity varies linearly with concentration, is valid only for c 2 M. At higher concentrations the permittivity decreases more slowly, which would shift the high concentration region of the model curves towards the experimental data, improving the fit.…”