Magnetic Phase Transitions in Macro/Mesoporous Bioactive Glass by Ferric Nitrate Addition in Sol-Gel Synthesis

摘要

Multifunctional macro/mesoporous bioactive glasses (MMBG) with magnetic sensitivity are prepared by adding ferric nitrate in a one-pot sol-gel synthesis. Three different magnetic properties are obtained depending on the synthesis composition and calcination atmosphere. The gradual transition from paramagnetism to superparamagnetism is observed when ferric nitrate is increased from 5 up to 20 mol%. In contrast to minimal paramagnetic response to an applied magnetic field, substantial magnetizations are induced in superparamagnetic MMBG owing to the formation of iron oxide nanoparticles, which is signified by the change in color after calcination. The transition from superparamagnetism to ferromagnetism occurs when the MMBG are calcined in an argon instead of an oxygen atmosphere. This ferromagnetic hysteresis coincides with the formation of Fe-rich spheres with diameters larger than 100 nm.