Effect of Heat-Treatment Temperatures on Magnetite Oxidation in ۲۰SiO۲.۵۰FeO.۳۰CaO Glass Ceramic Prepared by the Sol-Gel Method

Abstract The effect of different heat-treatment temperatures on the magnetic, crystallization, and structural properties of ۲۰SiO۲.۵۰FeO.۳۰CaO (mol%) glass ceramics was studied. The initial glass was synthesized by the sol-gel method at ۲۵℃  with a precursors to solvent ratio of ۱/۵. After aging the resulted gel for ۲۴ h at room temperature, it was dried in an electric dryer at ۱۱۰ ℃ . By heat treatment at different temperatures, different phases such as magnetite, maghemite, and hematite were crystallized in the glass. The maximum stability temperature of magnetite and maghemite were ۳۶۰℃  and ۴۴۰℃  respectively. By increasing the heat treatment temperature to higher than ۴۴۰℃ , the oxidation of maghemite to hematite was occureds. The highest magnetization amount (۱.۹ emu/g) belonged to sample heat treated at ۶۸۰℃ . By increasing the heat treatment temperature to ۸۴۰℃ , the magnetization decreased to ۰.۸ emu/g, due to the oxidation of maghemite. By increasing the heat treatment temperature from ۴۴۰℃  to ۶۸۰℃ , crystalline size of maghemite was increased from ۴۰ to ۲۰۰ nm. By forther increment of temperature to ۸۴۰℃ , the size of maghemite crystals decreased to ۱۷nm, due to the oxidation of maghemite to hematite. Abstract The effect of different heat-treatment temperatures on the magnetic, crystallization, and structural properties of ۲۰SiO۲.۵۰FeO.۳۰CaO (mol%) glass ceramics was studied. The initial glass was synthesized by the sol-gel method at ۲۵℃  with a precursors to solvent ratio of ۱/۵. After aging the resulted gel for ۲۴ h at room temperature, it was dried in an electric dryer at ۱۱۰ ℃ . By heat treatment at different temperatures, different phases such as magnetite, maghemite, and hematite were crystallized in the glass. The maximum stability temperature of magnetite and maghemite were ۳۶۰℃  and ۴۴۰℃  respectively. By increasing the heat treatment temperature to higher than ۴۴۰℃ , the oxidation of maghemite to hematite was occureds. The highest magnetization amount (۱.۹ emu/g) belonged to sample heat treated at ۶۸۰℃ . By increasing the heat treatment temperature to ۸۴۰℃ , the magnetization decreased to ۰.۸ emu/g, due to the oxidation of maghemite. By increasing the heat treatment temperature from ۴۴۰℃  to ۶۸۰℃ , crystalline size of maghemite was increased from ۴۰ to ۲۰۰ nm. By forther increment of temperature to ۸۴۰℃ , the size of maghemite crystals decreased to ۱۷nm, due to the oxidation of maghemite to hematite.

کلیدواژه ها:

Bioactive Glass-Ceramic ، Magnetic properties ، Sol-Gel ، Hyperthermia ، Maghemite