A new method, hydrothermal method, to synthesize Ni doped rutile TiO2 nanotube (TNT) powders is introduced. This method is more scalable than ones used before. Interestingly, our Ni doped TNTs' structures show different characteristics and properties than ones fabricated by other methods. We report these resulting structural and magnetic properties here. Ni doped nanotubes contained H2Ti2O5H2O doped with trivalent Ni. The layered structures had six nm inner and ten nm outer diameters, aspect ratios of seven, and exhibited ferromagnetism at room temperature (undoped nanotubes were diamagnetic). Contrary to earlier versions of Ni doped TNTs, we found that trivalent Ni atoms substituted H+ in the nanotubes and thus interacted with titanate's 3d electrons to produce ferromagnetic activity. This opens the possibility to achieve ferromagnetic activity in TNTs in a new way.

Keywords: TNTs, Magnetic properties, Ni doping, Hydrothermal method.