In-flight coating of nanoparticles in atmospheric-pressure DBD torch plasmas

Two DBD torch designs were used to investigate coating and surface functionalization of small particles. One had an annular discharge gap between coaxial quartz tubes, the second, suited for high throughput, used external shell electrodes on opposite sides of a quartz tube. Several discharge sections could be used in flow direction, with intermediate ports for particle and/or monomer injection. Both torches were operated by a sinusoidal high voltage (13 kV, 20 kHz). The coaxial torch always showed a filamentary discharge, while the shell-electrode design in He also produced diffuse glow discharges. A variety of different precursors and dielectric as well as metallic particles of nanometer or micrometer diameter were used.