Role of TiO2 nanoparticles in the dry deposition of NiO micro-sized particles at room temperature

A room-temperature dry-deposition method with TiO2 powder was used to deposit NiO particles onto a fluorine-doped tin oxide (FTO) substrate. Initially, in the absence of TiO2 powder, we observed that the NiO particles did not adhere to the substrate; however, the addition of TiO2 particles facilitated NiO deposition. The volume percentage (vol%) deposition of NiO particles increased with the TiO2 particle concentration. The inability of the NiO particles to adhere to the FTO substrate was attributed to the absence of deformation and fragmentation in the substrate. This is related to the lower hardness of the FTO substrate, compared with that of the NiO particles. However, the addition of the TiO2 particles at different vol% during NiO deposition induced deposition, possibly due to the lower hardness of the TiO2 particles compared with the FTO substrate. The minimum TiO2 fraction that enabled NiO powder deposition was ~4.8 vol%. Microstructural analysis revealed that TiO2 powder agglomerates tended to break up as the NiO particles impacted the substrate surface, creating a “deposition complement” from the excess kinetic energy. The deposition mechanism was investigated using microstructural analysis, electron probe microanalysis, and Brunauer–Emmett–Teller (BET) measurements; the results confirmed the influence of the TiO2 powders on NiO powder deposition, specifically, an improvement in the adhesion and density of the NiO powder and a decrease in the surface roughness of the coating. Therefore, we demonstrated NiO deposition with TiO2 particles at room temperature, providing potential applications to the supercapacitor and battery industries.