Generation and characterization of field-emitting surface dielectric barrier discharges in liquids

Field-emitting surface dielectric barrier discharges (FESDBDs), previously generated in CO₂ from high pressures up to supercritical conditions using 10 kHz ac excitation, were investigated in non-aqueous liquid CO₂ and liquid silicone oil. In both liquids, the maximum amount of negative charge Q_-deposited as a function of the applied voltage amplitude was consistent with the Fowler-Nordheim equation, which demonstrated the presence of field emission. Furthermore, purely continuum optical emission spectra attributable to electron-neutral bremsstrahlung were confirmed. The fact that these characteristics were identical to those in high-pressure CO₂ reported from previous research shows that FESDBDs can be generated independently of the medium type and that they are low-power (on the order of 10 mW) discharges. To investigate the charging function of FESDBDs, the motion of fine particles suspended above the FESDBDs was studied by high-speed imaging. It revealed that the speed of fine particles affected by the FESDBDs depends on the particle size, the FESDBDs' function being to charge fine particles.