Titanate nanotubes and their magnetic properties: Effect of ion exchange and calcination temperature

Transition magnetic metals (Fe, Ni, Co) were inserted into sodium titanate nanotubes subjected to calcination. In the calcination process at 400 degrees C, the nanotubular structure of the samples with magnetic species breaks down, while at 800 degrees C the formation of TiO2 nanoparticles occurs mainly in the anatase and rutile phases. Optical studies revealed that the Fe3+, Ni2+ and Co2+ ions insertion promoted red shift in UV-Vis and the samples, showed smaller energy gap than NaTiNT. In addition, the samples calcined at 400 degrees C showed higher conductivity due to the greater number of oxygen defects. All samples exhibited ferromagnetic behavior at room temperature in low magnetic fields. The ferromagnetic behavior for these materials may originate from the interaction between the ions intercalated in the titanate lattice from the defects of oxygen incorporated in the nanotubes by the calcination process and from the transition from Ti4+ to Ti3+ in some sites of the nanotube structure.

Automated summary

Transition magnetic metals (Fe, Ni, Co) were inserted into sodium titanate nanotubes and subjected to calcination. The calcination process caused breakdown of the nanotubular structure at 400 degrees C and formation of TiO2 nanoparticles, mainly in the anatase and rutile phases, at 800 degrees C. The insertion of Fe3+, Ni2+ and Co2+ ions promoted red shift in UV-Vis and smaller energy gap compared to NaTiNT. Additionally, the samples calcined at 400 degrees C exhibited higher conductivity and all samples showed ferromagnetic behavior at room temperature.