The present study highlights the effect of metal precursor types (SO₄²¯, Cl¯, and NO₃¯), their concentration, and the influence of ionic strength of reaction environment on the morphology, surface, and magnetic properties of CoFe₂O₄ particles. The magnetic nanoparticles were obtained by chemical coprecipitation in alkaline medium at increasing metal concentration in the range of 0.0425 mol·dm^-3 to 0.17 mol·dm^-3 and calcination temperature from 400°C to 800°C. It was found that the chemistry of precursors can be directly correlated with magnetic properties. The CoFe₂O₄ particles from metal sulphate precursors showed the highest saturation magnetization and the lowest coercivity. The adjustment of ionic strength in the range of 1.25–5 M was achieved by adding an appropriate quantity of metal sulphates into aqueous solutions at a constant pH or by adding an appropriate quantity of NaClO₅ under similar conditions. The average hydrodynamic size of CoFe₂O₄ increased from 46 nm to 54 nm with increasing metal concentration and ionic strength. An explanation of magnetic properties, caused by ionic strength and metal concentration, is given based mainly on the reduction in repulsive forces at the particle interface and compensation of the double electric layer in the presence of anions. The observed coercivity was lower for the particles obtained in solutions with the highest ionic strength, whereas the concentration of metals and calcination temperature affected the saturation magnetization and morphology of the obtained cobalt ferrite particles.

中文翻译：

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CoFe2O4纳米颗粒的合成：离子强度，浓度和前驱体类型对形貌和磁性的影响

本研究着重介绍了金属前驱体类型（SO ₄ ²，Cl和NO ₃）的影响，它们的浓度以及反应环境的离子强度对CoFe ₂ O的形态，表面和磁性的影响。_4个粒子。通过在0.0425 mol·dm ^-3至0.17 mol·dm ^-3的范围内增加金属浓度和在400℃至800℃的煅烧温度下在碱性介质中化学共沉淀来获得磁性纳米颗粒。已经发现，前体的化学性质可以与磁性能直接相关。CoFe ₂ O ₄来自金属硫酸盐前体的颗粒显示出最高的饱和磁化强度和最低的矫顽力。通过在恒定pH值下向水溶液中添加适量的金属硫酸盐或在类似条件下添加适量的NaClO ₅，可将离子强度调节至1.25-5M 。CoFe ₂ O ₄的平均流体动力学尺寸随着金属浓度和离子强度的增加，从46 nm增加到54 nm。由离子强度和金属浓度引起的磁性能的解释主要是基于颗粒界面排斥力的降低和阴离子存在下双电层的补偿。在具有最高离子强度的溶液中获得的颗粒，观察到的矫顽力较低，而金属的浓度和煅烧温度会影响所获得的钴铁氧体颗粒的饱和磁化强度和形貌。