Kim Jong-Hee, Kim Sang-Mun, Kim Yong-Il
J Nanosci Nanotechnol. 2014 Nov;14(11):8739-44. doi: 10.1166/jnn.2014.9993.
Magnetic nanoparticles were synthesized by the addition of ammonium hydroxide to an iron chloride solution by chemical co-precipitation. In order to examine systematically the crystal phase, average size, and magnetic properties of the magnetic nanoparticles, the following were used as experimental parameters: molar ratio of Fe2+/Fe3+, composition of the iron chloride solution, amount of ammonium hydroxide, reaction temperature, and oxidation time of reaction precipitate. In the processing conditions of Fe2+/Fe3+ ratios of 0.5 and 1.0, iron chloride solutions of 0.1-0.8 m, NH4OH molar ratios of 6-14R, reaction temperatures of 25-80 degrees C, and oxidation times of 5-90 min, the co-precipitated nanoparticles were observed to exist as a single phase of Fe3O4. The average size of the particles was approximately 20 nm, and their magnetization was saturated at about 60 emu/g with superparamagnetism. When the iron chloride solution comprised only Fe2+ ions, the oxidation of the reaction precipitates also developed a Fe3O4 phase. However, the particle size reached 78 nm with increasing oxidation times, and the saturation magnetization increased significantly to 82 emu/g while its coercive force was 150 Oe, which indicated that the nanoparticles were paramagnetic.
通过化学共沉淀法向氯化铁溶液中加入氢氧化铵来合成磁性纳米颗粒。为了系统地研究磁性纳米颗粒的晶相、平均尺寸和磁性，将以下参数用作实验参数：Fe2+/Fe3+的摩尔比、氯化铁溶液的组成、氢氧化铵的用量、反应温度以及反应沉淀物的氧化时间。在Fe2+/Fe3+比例为0.5和1.0、氯化铁溶液浓度为0.1 - 0.8 m、NH4OH摩尔比为6 - 14R、反应温度为25 - 80℃以及氧化时间为5 - 90分钟的处理条件下，观察到共沉淀的纳米颗粒以Fe3O4单相形式存在。颗粒的平均尺寸约为20 nm，其磁化强度在约60 emu/g时达到饱和，具有超顺磁性。当氯化铁溶液仅包含Fe2+离子时，反应沉淀物的氧化也会形成Fe3O4相。然而，随着氧化时间的增加，颗粒尺寸达到78 nm时，饱和磁化强度显著增加至82 emu/g，同时其矫顽力为150 Oe，这表明纳米颗粒是顺磁性的。
