Supersonic jet deposition of laser ablated silver nanoparticles for mesoscale structures
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The Laser Ablation of Microparticle Aerosols (LAMA) technique was used to generate silver nanoparticles and they were supersonically impacted on different substrates to form mesoscale functional structures in this study. The electrical signal of the plume generated by the laser ablation of microparticle aerosol in 1 atm was diagnosed with a series of Faraday cups and the related recombination process was studied to understand the properties of the charged silver nanoparticles in this high pressure dusty plasma. The experimental results shows that the silver NPs carries positive charge and the charge decays approximately exponentially with respect to the traveling time and the 1/e decay time increases about 60% when an anode layer is added near the ablation zone. Supersonically deposited silver nanostructured films were deposited using He and Ar gas through a flat plate and conical nozzles. The films were characterized to vii determine their morphologies, strains, and their conductivity changes with respect to the different annealing processes. It was found that the as deposited films tended to retain the internal feature dimension and crystallite grain size of the deposited nanoparticles. Increased impaction energy increased the film density and promoted sintering and neck formation without significant grain growth for deposition at room temperature. The silver films deposited in helium showed a higher density than in Ar. The annealing of the silver films produced in helium and Ar by using a flat plate nozzle showed a trend of conductivity increase as the annealing temperature increased. And the conductivity of the silver films deposited in helium was relatively higher than that of the film deposited in Ar. After heat treatment at 400ºC for 90 minutes, the silver film deposited in helium has a conductivity of 47% of the bulk silver conductivity. Modeling results shows density of the film deposited through flat plate nozzle in He has relatively higher density than the film deposited in Ar through flat plate nozzle. Annealing did not change the density of the films deposited in the same condition.