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Seminarji / Predavanja

 

18. marec 2010 ob 13:00, Kolarjeva predavalnica
 
Characterisation of electrodeposited Ni-Co, Ni-Fe and Ni-Mo powders



Vladimir Jovic

Institut za multidisciplinarne studije, Beograd, Srbija

 

The Ni-Co powders
The electrodeposition of pure Ni, Co and Ni-Co alloy powders from ammonium sulfate and chloride containing electrolytes for different Ni/Co ions concentration ratios at pH 9 was investigated by the polarization measurements. It was shown that polarization curves must be recorded with IR drop compensation in order to obtain correct polarization curves. The morphology, chemical composition and phase composition of the obtained powders were investigated using SEM, EDS and XRD analysis. EDS and chemical analysis of as-deposited alloy powders confirmed anomalous co-deposition of Co and Ni. Different morphologies of pure powders, as well as alloy powders were obtained in different electrolytes. A common characteristic for all as-deposited powder samples was the presence large agglomerates, some of them being characterized with the cavities and nodules on their surfaces. The mechanism of powder particles formation has been developed from the analysis of their morphology.

The Ni-Fe powders
The electrodeposition of the Ni/Fe powders from citrate-ammonium chloride containing electrolytes for different Ni/Fe ions concentration ratios at pH 4.0 was investigated by the polarization measurements. The morphology, chemical composition and phase composition of the obtained powders were investigated using SEM, EDS and XRD analysis. EDS and chemical analysis of as-deposited alloy powders confirmed anomalous co-deposition of Fe and Ni. A common characteristic for all as-deposited powder samples was the presence of cone shaped cavities and nodules on the big agglomerates of the order of 200 - 400
mm. After annealing in air at 400 oC, 600 oC and 700 oC for 3 h all alloy powders oxidized forming NiO, NiFe2O4 and Fe2O3 phases in different proportions depending on the original powder composition. The NiFe2O4 phase was found to be dominant in the sample with the highest percentage of Fe after annealing at 600 oC.

The Ni-Mo-O powders
The Mo-Ni-O powders were electrodeposited from ammonium
sulfate containing electrolytes with different Ni/Mo ion concentration ratios at pH 9. The phase composition of these powders was investigated using TEM, EDS and XRD analysis. The TEM analysis showed that two types of particles were present in the powders: amorphous and crystalline. For crystalline particles it was found that two phases, MoO3 and MoNi4 prevail in all powders, while the NiO phase was detected in the powder electrodeposited at Mo/Ni = 0.3/1. These findings are in good agreement with our previous results where MoO3, MoNi4 and NiMoO4 phases were detected in the recrystallized Mo-Ni-O powders.

 

 

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