模板辅助sol-gel法制备高比表面积、高磁性能纳米CoFe_2O_4材料

Synthesis and Characterization of Nano-sized Cobalt Ferrite Powders with High Specific Area and Magnetic Properties in Template-assisted Sol-gel Method

以金属硝酸盐和柠檬酸为主要原料,医用脱脂棉为模板,通过简单易行的模板辅助sol-gel法来制备高比表面积、高磁性能纳米CoFe2O4材料.采用XRD,TEM,BET,VSM和Easy heat等方法研究了模板和热处理温度对所得材料组成、微观结构、磁性能和磁加热效率等的影响.结果表明:添加模板有利于获得不含杂质相的尖晶石型纳米磁性CoFe2O4颗粒,随热处理温度的升高,颗粒的平均晶粒尺寸逐渐增加,比表面积减小.未添加模板的纳米颗粒存在较为严重的堆积现象,添加模板后所得CoFe2O4颗粒呈近似椭球形,不同颗粒之间首尾相接,类似线形,团聚程度明显下降.添加模板后800℃热处理所得试样的平均晶粒尺寸约为70.0nm,比表面积为23.7m2/g,饱和磁化强度为79.0emu/g,剩磁强度为37.1emu/g,矫顽力为856.4G,磁加热速率为2.95℃/s,均显著高于相同热处理温度下未加模板所制备的铁氧体颗粒.最后对类线形纳米CoFe2O4的形成过程进行了探讨.

A simple template assisted sol-gel method was used to prepare nano-size CoFe2 O4 powders with high specific surface area and magnetic properties.The influences of template and heat treated tem-peratures on the composition,microstructure,specific area,magnetic properties as well as magnetic heat-ing rate were studied through XRD,TEM,BET,VSM and RF heat tests.The results show that adding template helps to obtain pure spinel CoFe2 O4 nano-magnetic particles,and with the increase of heat treated temperature,the average grain size of the as-prepared nano-particles increases,reducing its surface area. Without template,the as-prepared nano-particles exhibit serious accumulation.After adding the template,CoFe2 O4 particles are the approximate ellipsoid,and connected one by one,similar to a line,and its ag-glomeration decreases significantly.The average grain size of nano-sized particles obtained when adding template and calcined at 800 ℃ is about 70.0 nm,its specific surface area is 23.7 m2 ＆#183;g-1 ,its Ms equals to 79.0 emu＆#183;g-1 ,its Mr equals to 37.1 emu＆#183;g-1 ,its coercive force equals to 856.4 G,and its magnetic heating rate is 2.95 ℃＆#183;s-1 .These values are all significantly higher than that of nano-sized CoFe2 O4 par-ticles obtained without template and calcined at 800 ℃.Finally,the formation process of thread-like nano-sized CoFe2 O4 particles was discussed.