球形尖晶石型钴铁氧体:合成方法及其影响因素

Spherical Co-Spinel Ferrites: Synthesis and Control Factors

实现了在低温、常压条件下由含铁水滑石微晶到球形尖晶石型铁氧体的合成。结果表明,所合成的铁氧体系平均粒径为1.0μm的规整球。进一步研究发现,铁氧体微球的成型过程受到很多因素影响,例如,球型铁氧体磁性粒子的大小随着晶化过程中溶液的酸碱度的升高而变大;同时外加磁场的存在不但会使球型铁氧体磁性粒子的粒径变大,而且也会使晶化产物的粒子形貌更加趋于规整。另外,还对不同组成的尖晶石型铁氧体微球的形成进行横向比较时发现,合成初期的化合物投料组成对终产物形貌的影响是巨大的,随着投料组成中Fe2+含量的增加,转化过程变得容易,且在投料金属离子组成nCo2+∶nFe2+∶nFe3+为1∶1∶1时,所得的球型铁氧体磁性粒子的粒径最大。相同条件下不同组成的铁氧体微球粒径差异明显,MgFe2O4不能形成球形颗粒,NiFe2O4和CoFe2O4可以形成球形颗粒,其中CoFe2O4形成的颗粒粒径最大。

pherical Co-spinel ferrites were prepared by aging Co2 ＋/Fe2 ＋/Fe3 ＋-LDH （layered double hydroxides） suspension at temperature below 100 ℃. The products were characterized by XRD,FTIR, SEM and Vibration sample magnetometer（VSM）. SEM results show that the products of Co-spinel ferrite are spherical particles with an average diameter of 1.0 μm. The size of spherical particles increases with the pH value of reactive solution and the existence of external magnetic field also has much influence on the size of spinel ferrites and the morphology of the products. Formation of the products is favored when charging with a higher molar ratio of Fe2＋ to Co2＋and Fe3＋, and the largest size of spherical product is obtained when the charge is with an 1∶1∶1 molar ratio of Co2＋∶Fe2＋∶Fe3＋. Compared with Mgspinel ferrites and Ni-spinel ferrites, spherical diameter of Co-spinel ferrites are the largest.