(95b) Synthesis of Metal Nanoparticles Via Cryogenic Milling and in Situ Atomic Layer Deposition for Passivation

Metal nanoparticles were produced via the thermal decomposition of metal oxalate powders, with iron as the focus in this study. The particle size of the feed oxalate powders was first reduced using a cryogenic milling technique. The milling effect was studied under different milling conditions, including different milling media size, the mix solution, and the milling time. After the cryomilling process, the metal salts were thermally decomposed in a fluidized bed reactor. The metal nanoparticles were produced with a final particle size of about 50-80 nm. Due to high surface area, the synthesized metal nanoparticles are pyrophoric and violently oxidize when exposed to air. An in situ atomic layer deposition (ALD) method was then applied to protect the synthesized metal nanoparticles from oxidation. Oxygen-free films, such as AlN films, were used as the passivating barrier. The passivation effect was demonstrated by comparing the composition and properties of the metal particles with and without the nitride ALD films.