Session *BB3.1

8:30 AM *BB3.1
EXTENDING THE RANGE OF PLASMA SPRAYING: LOW PRESSURE FINE PARTICLE SPRAYING. J.V.R. Heberlein, H.C. Chen, N. Rao, S. Girshick, P. McMurry, University of Minnesota, Dept of Mechanical Engineering, Minneapolis, MN.

In the adaptation of the thermal spray process to the generation of coatings with specific materials properties, two new approaches are being investigated which extend the parameter range that is conventionally being used in plasma spraying. In the Low Pressure Central Injection spray process, fine powders (10 to 30$\mu$m diameter) are injected into the plasma formed by three plasma jets from three independently operated torches in an environment of 50 Torr. This process has been demonstrated to yield yttria stabilized zirconia films with a porosity less than 0.5%, which are impermeable at a thickness of 30$\mu$m. The films have been evaluated as dielectric layers in a solid oxide fuel cell. The second process, Hypersonic Plasma Particle Deposition involves the synthesis of nanosize particles in a plasma jet which is subsequently quenched through acceleration in a supersonic nozzle, acceleration of these particles to hypersonic speeds and deposition on a substrate in front of the nozzle. On-line measurement of the particle size distributions show that the distributions peak around 10 nm. Deposition of these particles using this process has shown to yield films with nanosize structures of silicon and silicon carbide. These new processes are compared with conventional plasma spraying and with other emerging plasma coating processes.