H2O2氧化法制备Fe3O4纳米颗粒及与共沉淀法制备该样品的比较

在近中性条件下，利用H₂Ｏ₂氧化Fe(OH)2胶体成功制备了Fe₃ Ｏ₄纳米颗粒.分别利用透射电镜(TEM)，x射线衍射仪(XRD)，振动样品磁强计(VSM)和超导量子干涉仪（SQUI D）对样品的形貌，结构，宏观磁性进行了表征和测量.TEM图像表明样品为球形颗粒，直径 大小约18nm，且分布较均匀.XRD结果表明样品为立方尖晶石结构.穆斯堡尔谱测量表明样品 室温下对应两套六线谱，样品的晶体结构存在缺陷，内磁场略小于块体Fe₃Ｏ4的值. 宏观磁测量表明样品的饱和磁化强度可达67×10^-3A·m²/g，在20 K出现了Verw ey转变.选择该法制备的Fe₃Ｏ₄纳米颗粒与共沉淀法得到的样品作 了磁性比较.宏观磁 测量表明共沉淀法制备的样品在外磁场为1T时仍未饱和，磁化强度仅为46×10^-3A·m²/g，在178K出现了超顺磁转变温度，且在测量温度范围内没有发现Verwe y转变. 关键词： 亚铁磁 超顺磁 穆斯堡尔谱

Method for fabricating Fe3O4 nanoparticles using H2O2 and its comparison with coprecipitation method

Fe₃Ｏ₄ nanoparticles were successfully synthesized from an aqueous Fe (OH)2 colloid under nearly neutral condition by oxidizing it with H₂Ｏ2. The m orphology, structure, and magnetic properties were characterized and measured by transmission electron microscopy (TEM), x-ray diffraction (XRD), vibrating sam ple magnetometer, and superconducting quantum interference devices (SQUID). The TEM image shows that the sample consists of well-dispersed spherical particles with diameter about 18nm, and has a cubic spinel structure according to XRD. The mssbauer spectrum at room temperature is fitted using two sextet spectrum cor responding to Fe ions at A site and B site, and the results show that th e hyperfine field of the sample is a little smaller than that of bulk value, and crystalline defects exist in the sample. The saturation magnetization of the sa mple fabricated by using H₂Ｏ₂ is 67×10^-3A·m ²/g, and the Ver wey transition was observed at 20K, but the magnetization of the sample fabricat ed by coprecipitation is only 46×10^-3A·m²/g when the app lied field is 1 Tesla, and the Verwey transition was not observed in our temperature range of measurement. In addition, the superparamagnetic blocking temperature of the s ample fabricated by coprecipitation was observed at 178K.