Synthesis of silica-coated ferromagnetic fine powder by heterocoagulation
Synthesis of silica-coated ferromagnetic fine powder by heterocoagulation
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DOI：
10.1088/0953-8984/20/20/204105
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发表时间：
2008-05
期刊：
影响因子：
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通讯作者：
H. S. Park;Gjergj Dodbiba;L. Cao;T. Fujita
中科院分区：
文献类型：
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作者：
H. S. Park;Gjergj Dodbiba;L. Cao;T. Fujita
本文研究了核壳粒子（即覆盖二氧化硅的温度敏感铁氧体（TSF））的合成。首先，用共沉淀法在碱性溶液中制备平均直径为10 nm的TSF；然后，通过正硅酸四乙酯（TEOS）的可控水解缩聚，在TSF表面进行了二氧化硅涂层。以TSF纳米颗粒为核心材料，通过表面沉淀形成核壳颗粒。二氧化硅颗粒形成，然后这些颗粒被TSF纳米颗粒吸收。根据Derjarguin-Landau-Verwey-Overbeck （DLVO）理论，通过计算TSF和SiO2纳米颗粒之间相互作用的势能来描述和解释涂层过程。涂层过程受TEOS前驱体的pH和浓度的影响。用透射电镜（TEM）观察了TSF芯上二氧化硅层的厚度。结果表明：当pH为7.5时，TSF芯颗粒上SiO2层厚度最佳，TEOS浓度为9 mM；
In this paper, the synthesis of core–shell particles (i.e. temperature-sensitive ferrite (TSF) covered with silica) has been investigated. At first, TSF (mean diameter of 10 nm) was prepared by the coprecipitation method in an alkaline solution. Then, silica coating on the TSF surface was carried out by the controlled hydrolysis and condensation of tetraethyl orthosilicate (TEOS). The core–shell particles were formed by a surface precipitation procedure using TSF nanoparticles as a core material. The particles of silica were formed and these particles were then absorbed on the TSF nanoparticles. The coating procedure was described and explained by calculating the potential energies of interaction between the TSF and SiO2 nanoparticles, according to the Derjarguin–Landau–Verwey–Overbeck (DLVO) theory. The coating process was found to be influenced by the pH and concentration of the TEOS precursor. The thickness of the silica layer on TSF cores was observed by means of transmission electron microscopy (TEM). The results showed that the optimum thickness of the SiO2 layer on TSF core particles was obtained at pH 7.5, while the TEOS concentration was kept at 9 mM.