Anomalous Codeposition of Alloy Powders

Anomalous Codeposition of Alloy Powders 8.2.1 Electrodeposited Co-Ni Powders... 

The composition of the electrolyte, i.e., Ni VCo " ions ratio, influences polarization curves for Co-Ni alloy powders electrodeposition, as well as alloy powder composition and morphology. It is also concluded that the shape of the polarization curves in all cases is practically defined by the shape of the polarization curve for hydrogen evolution. In the case of Ni powder cauliflower and spongy-type particles are detected, while Co powder contains only spongy-type particles. Both types of particles are present in the Co-Ni alloy powders obtained at Ni /Co ions ratios 4.00, 1.50, and 0.67, while only spongy-type particles are detected in the Co-Ni alloy powder obtained at Ni VCo " ions ratio 0.25. In all cases of alloy powder electrodeposition anomalous type of codeposition is detected. 

The morphology and composition of electrodeposited Fe-Ni alloy powders depend on the Ni/Fe ions concentration ratio in both electrolytes. Anomalous codeposition of Fe and Ni has been... 

The polarization curves corrected for IR drop for the processes of Fe, Ni, and Fe-Ni alloy powder electrodeposition from ammonium chloride-sodium citrate containing supporting electrolyte in the presence of Fe(ll) and Ni(II) species are shown in Fig. 8.14. In the case of Fe(II) salts, polarization curve for iron electrodeposition (Fe) was placed at more positive potentials than that for nickel (Ni) as it is expected from the values of their reversible potentials. The polarization curves for Fe-Ni alloy powder electrodeposition are placed in between, and all of them were placed at more positive potentials than expected from the Ni/Fe ratio, indicating anomalous codeposition. 

The same dependences as in Fig. 5.5 are presented in Fig. 5.6 for chloride containing supporting electrolyte. In this case anomalous codeposition is obtained for all Co-Ni alloy powders compositions, with the more noble metal electrodeposition (Ni) being suppressed by the presence of the less noble metal (Co) in the solution, i.e., less noble metal is more readily deposited. 

---