Synthesis of the oxide and metal-oxide nanoparticles by the ultrasonic spray pyrolysis

This thesis presents the results of the investigation of the nanoparticle formation mechanism and the controlled synthesis of the spherical Al2O3 and TiO2 and complex Ag/Al2O3, Ag/TiO2 and Au/TiO2 nanoparticles by Ultrasonic Spray Pyrolysis (USP). The motivation for the synthesis of those nanoparticles is a novel method for the improvement of the tribological and the electrical properties and the life-time of the galvanic gold layers by the incorporation of the nanoparticles. Ultrasonic Spray Pyrolysis was chosen as the synthesis method due to its high flexibility to produce nanoparticles with various chemical and morphological characteristics. Special attention was paid to the characterization of the microstructure of the produced nanoparticles. The morphology and semi-quantitative analysis of the chemical composition of synthesised nanoparticles were investigated. The further investigation of the obtained micrographs was done with the image analyses software ImageJ in order to determine the particle size and the particle size distribution. The chosen samples were also analysed by Focused Ion Beam (FIB), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy, TEM (STEM) with Bright-Field (BF) and Dark-Field (DF). Based on the obtain results, the classical theoretical model of the droplet-to-particle mechanism was upgraded in order to fit the oxide nanoparticles synthesized on the lab-scale and the technical-scale one-step USP equipment. A new model is proposed for the formation of the complex Ag/TiO2 and Au/TiO2 nanoparticles in the one-step USP. The alternative, two-steps USP synthesis method is proposed and tested for the synthesis of the Au/TiO2 nanoparticles, and the model is proposed for the nanoparticles` formation in this equipment.