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

Abstract

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 μm 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 μm, the average deposition thickness was measured to be 2.49 μm, whereas the average deposition thickness was 300 nm for SoD being 500 μm. Therefore, Ni powder deposition at a SoD of 300 μm was successful compared to a SoD of 500 μm 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 μm was substantially lower than that of the film deposited at a SoD of 500 μm, confirming the successful deposition at a SoD of 300 μm. Finally, heated treatment of the deposited Ni powders to 150 °C improved the electrical conductivity significantly by lowering its resistivity to 4.4 × 10⁻⁷ Ωm.