Voltammetric characteristics of the metal-oxide-electrolyte system at electrode polarization with pulse voltage

Effect of positive and negative pulse voltages on surface properties and equivalent circuit of the plasma electrolytic oxidation process

“…Operation at these conditions leads to a generation of plasma microdischarges and vapour gaseous envelope in the vicinity of the treated surface; this makes the system"s behaviour nonlinear and requires careful control of electric and thermal parameters required for the process [3]. In such a system, the majority of voltage drops across a thin oxide layer generally possessing n-type of conductivity; under anodic polarisation this leads to a reversely biased semiconductor barrier [4]. Resulting high field strength promotes a dielectric breakdown which initiates plasma discharge within the oxide layer, facilitating its growth.…”

Towards smart electrolytic plasma technologies: An overview of methodological approaches to process modelling

“…Depending on oxide film conductivity and semiconductor properties, the formed Schottky type metal-oxide-electrolyte two junction system can be forward or reverse biased [32,33]. With the forward biased junction, the EPP features a vapour gaseous envelope (VGE) surrounding the working electrode.…”

“…At the anodic polarisation, the surface layer exhibits low conductivity (the valve effect) and the major voltage drop occurs across it. With the SCR thickness usually being less than a micron, the electric field there at voltages typically applied in EP treatments can reach breakdown values (~ 10 7 V/cm) [33]. PEO treatments can therefore be easily implemented to grow protective coatings on the valve metals [2,58].…”

“…One group of theoretical models focuses on metal-dielectric-electrolyte interfaces [33] and analyses of impedance spectra [82,83]. This group is tightly connected with equivalent circuit models which can be obtained from the impedance spectra and current-voltage characteristics.…”

“…22a, whereas on the outer surface, the thickness distribution is relatively even. Thus, the distribution of current density in the electrolyte can explain variations of surface characteristics within the 33 workpiece and provide estimates of boundary conditions for FR analysis; it should therefore be taken into account during phenomenological modelling.…”