Abstract
Nickel and nickel oxide nanoparticles, as model materials, prepared from different types of precursors (aqueous Ni (NO3)2.6H2O, NiCl2, and Ni (HCO2)2.2H2O) by using a low pressure spray pyrolysis (LPSP) is reported in this paper. Effects of type of precursor, temperature, pressure, carrier gas flow rate, concentration of precursor and type of reducing agents on the production of nickel and nickel oxide nanoparticles were investigated. It is found that different types of precursors and temperatures from 400 to 900 °C have great influences on controlling the size and morphology of final particles in low pressure environment. Higher solubility of precursor and higher temperature are in favor of the formation of nanoparticles.
The results also showed that pressure and carrier gas flow rate play crucial roles in the reduction of NiO to nickel in LPSP process. Relative higher solution concentration is suitable for the generation of nanoparticles. Cosolvents such as formic acid and ethanol as well as H2 were treated as the reductives in the synthesis of nickel (nanoparticles) from nickel metal salts. Weak NiO peaks together with strong nickel peaks in powder XRD patterns indicated that nickel nanoparticles are easier to be oxidated compared with the submicron sized one investigated in the conventional spray pyrolysis due to their higher surface potential. Another possible reason may come from the incomplete reduction in very short residence time because of the decrease of H2 amount in some cases. Possible mechanism of nickel and NiO nanoparticles formation in LPSP is suggested as well.
