Features of Ni / NiO Nanopowder Synthesis by Thermal Decomposition of Nickel Acetate Amines: Effect of Annealing Temperature and Duration and Ammonia Content on Powder Composition and Particle Size

Abstract

Ni/NiO nanopowders with different metal and oxide phase ratio have been prepared by using thermal decomposition of nickel acetate ammine complexes which contain various ammonia concentrations at the temperature range 300 – 500 ºC in air. Obtained powders have been characterized by IR-spectroscopy, XRD and TG, DTA, DTG, TEM, laser granulometry, adsorption-structural method and layer-by-layer Auger analysis. Thermal decomposition of nickel ammine complexes occurred with formation of crystalline hydroxide containing and amorphous carbonate containing precursors. Changing of precursors composition with different NH3 content and annealing duration and temperature leads to different pore structure, agglomerate size of powders and determinates free and fixed carbon concentrations. Mean crystallite size of nickel depended on temperature only. In the temperature range from 350 to 500 °С the crystallite size of nickel has grown from 50 to 55 nm. Mean crystallite size of nickel oxide depended on temperature and ammonia content. In the temperature range from 350 to 500 °С the crystallite size of NiO has grown from 5 to 25 nm. Increasing ammonia content from 3.6 to 14.4 mol/mol Ni led to decreasing NiO crystallite size from 8–10 to 5 nm.