Relationships Between Pore Structure, Free Carbon Content, Particle Size Distribution and Deposition Stage of Ni/NiO Nanopowers

Abstract

Ni/NiO nanopowders have been prepared by using thermal decomposition of aqua solutions of nickel acetate ammine complexes in air at the annealing temperature range 300 – 500 ºC, time of decomposition from 30 to 180 min. Particle size of powders has been investigated by and scanning electron microscopy (SEM). Powders pore structure has been determinated by low temperature nitrogen adsorption method. Content of free carbon in powders is determitated by stage of decomposition and annealing temperature. Decomposition of hydroxy-containing precursor at occurred in 3 stages: 1) the primary formation of Ni; 2) decomposition of precursors with formation of NiO; 3) afterreduction of NiO to Ni by residuals of organic compounds and ammonia. The first two stages is characterized by highly endothermic effect that can lead to decreasing of acetic acid evaporation rate and resulted in high free carbon content of powders. Increasing of deposition time permits to remove of acetic acid from particle surface and decrease free carbon content in powder.