Interaction of Cobalt Salt Solutions and Nickel Hydrosilicate Nanotubes

Synthetic nanotubes of nickel hydrosilicate (pecoraite) are treated with aqueous solutions of cobalt chloride, sulfate, and nitrate at various temperatures and salt concentrations under hydrothermal conditions. It is shown that under hydrothermal conditions, when nanotubes interact with a 0.1 M solution of cobalt nitrate for more than 4 h at a temperature ≥180°С the formation of the cobalt oxide phase Co₃O₄ is observed in the form of crystals of lamellar morphology. This phase actively crystallizes with the concentration of the Co(NO₃)₂ solution increasing up to 0.5 M. At the same time, the nanotubular structure of pecoraite is preserved. In the case of treating nanotubes with solutions of cobalt sulfate and chloride, significant amorphization of the hydrosilicate structure is observed, most likely leading to the complete destruction of the tubular morphology at a temperature of 220°C.