Synthesis of Copper, Silver, and Copper–Silver Powders via Ultrasonic Spray Pyrolysis and Hydrogen Reduction

Abstract

This thesis investigates the synthesis of copper (Cu), silver (Ag), and copper–silver (Cu-Ag) powders via ultrasonic spray pyrolysis (USP) and hydrogen reduction, focusing on how gas atmosphere, reduction temperature, and precursor ratio affect their morphology, particle size, purity, and stability. Understanding these parameters is important because they control how nanoparticles form, which affects their conductivity, catalytic activity, and resistance to oxidation. These properties are very important for many uses, such as making conductive inks and printed circuits for electronics, catalysts for chemical and energy processes, and protective coatings that stop corrosion or kill germs. In this work, four solutions were made using copper nitrate trihydrate and silver nitrate, then sprayed in a USP reactor and reduced under hydrogen and argon at temperatures between 500 °C and 700 °C. The powders made were studied with SEM and ImageJ to see their size and shape, and EDS to check their composition. The results show that the gas atmosphere had a strong effect on the particle size and shape. Hydrogen made particles more pure but also bigger and less uniform for silver, while argon gave more and smaller particles that looked more similar. For copper, using 600 °C and 650 °C made even smaller ones but with more clumping, which could help in catalytic use. For the Cu-Ag powders, the ratio of the two metals affected how stable the powders were: a 1:1 ratio gave small, uniform, core-shell particles without oxidation, while a 1:3 ratio caused clumping and surface oxidation. This work shows that gas type, temperature, and metal ratio are key to controlling the final powders with tunable surfaces and better stability.