Tuning grain size, morphology, hardness and magnetic property of electrodeposited nickel with a single multifunctional additive

Highlights: • Multifunctional Ni films with controlled grain size and roughness are electroplated. • PEOX serves as a multipurpose additive in Watts bath without incorporating into Ni. • Nanocrystalline Ni shows preferred crystalline orientation towards (220) plane. • PEOX concentration controls hardness and tunes magnetic properties of Ni layers. • The nickel films exhibit high affinity in forming passive oxide layer. The room temperature electrodeposition of high purity, nanocrystalline Ni films prepared in the presence of poly-(2-ethyl-2-oxazoline) (PEOX) as a new multipurpose polymeric additive in Watts bath is presented. The grain size, morphology, hardness and magnetic property of the nickel films were simply tuned by adjusting the concentration of PEOX. Increasing PEOX concentration contributed to grain refinement down to 12.5 nm grain size and crystalline orientation towards (220) planes. The control over the crystalline grain size and the orientation by PEOX concentration allows the preparation of tailor made nickel layers with adjustable physical and chemical properties. The effect of PEOX on the structure is attributed to the high affinity of tertiary amide groups in PEOX for metal surfaces, whereas the incorporation of the macromolecular additive into the nickel layers was prevented. These findings are especially important in emerging applications where smooth, high purity nanocrystalline layers are required. PEOX as a multifunctional additive eliminates the need to use multiple electrolyte additives to obtain a set of desirable properties.