Coating of Ni powders through micronozzle in a nano particle deposition system

Nano particle deposition system (NPDS) is a novel method to deposit ceramic and metal powders at room temperature. Nickel powders with a size of 3 mu m in diameter were sprayed through the fabricated micro nozzle, varying stand-off distance (SoD), which is a gap between the end of the nozzle and the substrate. Injection time for Ni powders was set to 1 min and the flow rate of air-powder was kept to 10 l/min. When SoD was 300 mu m, the average deposition thickness was measured to be 2.49 mu m, whereas the average deposition thickness was 300 nm for SoD being 500 mu m. Therefore, Ni powder deposition at a SoD of 300 mu m was successful compared to a SoD of 500 mu m with minimal deposition. Moreover, electrical resistance of the deposited film was measured to study its characteristics. Resistivity of the film deposited at a SOD of 300 mu m was substantially lower than that of the film deposited at a SoD of 500 mu m, confirming the successful deposition at a SoD of 300 mu m. Finally, heated treatment of the deposited Ni powders to 150 A degrees C improved the electrical conductivity significantly by lowering its resistivity to 4.4 x 10(-7) Omega m.