Increasing the magnetisation of electrolessly deposited Ni-B nanotubes

Magnetic nanotubes have a wide variety of potential applications in modern technologies in areas such as energy conversion, electronic devices and high density memory storage [1]. Recently using electroless deposition, we have established a method to prepare continuous nanotubes 20 μm in length with external diameter of 400 nm and uniform wall thickness of 100 nm [2]. The electroless process requires the use of a reducing agent, which favors the incorporation of an alloying element. In this study, we use dimethylamineborane (DMAB) as a reducing agent, resulting in the co-deposition of Ni and B, thereby forming Ni-B alloys [3]. As the deposits contain boron, the specific magnetization is lower compared to pure Ni. Here, we investigate the dependence of magnetic properties of Ni-B nanotubes on deposition bath pH and annealing temperature. We show that the specific magnetization of Ni-B nanotubes increases after annealing due to crystallization of amorphous nanotubes, while the nanotube structure is still preserved at high temperatures. Our results are analyzed in comparison to bulk Ni metal with specific magnetization of 55.4 JT^-1Kg^-1.