Abstract
Very low pressure plasma spraying (VLPPS) processes operate at a pressure of approximately 100 Pa, where the interaction of the plasma jet with the surrounding atmosphere is very weak and, as a result, plasma velocity is almost constant over a long distance from the nozzle exit. At these low pressures, the collision frequency is distinctly reduced and the mean free path is strongly increased. As a consequence, the specific enthalpy of the plasma is substantially higher, but at lower density. These particular plasma characteristics offer enhanced possibilities to spray thin and dense ceramics compared to conventional processes which operate in the pressure range between 5 and 20 kPa. This paper presents examples of gas-tight and electrically insulating layers with thicknesses less than 50 μm for solid oxide fuel cell applications. Plasma spraying of oxygen conducting membrane materials like perovskite is also discussed.
