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Preparation and characterization of silica-coated Fe3O4 nanoparticles used as precursor of ferrofluids |
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| Authors: | Ruo-Yu Hong Jian-Hua Li Hong-Zhong Li Jian-min Ding |
| Affiliation: | a College of Chemistry, Chemical Engineering and Materials Science & Key Lab. of Organic Synthesis of Jiangsu Prov., Soochow Univ., SIP, Suzhou 215123, China b State Key Lab. of Multiphase Reaction, Inst. of Proc. Eng., Chinese Academy of Sciences, Beijing 100080, China c State Key Lab. of Coal Conversion, Inst. of Coal Chem., CAS, Taiyuan 030001, China d Chem. Eng. Dept., Univ. of New Brunswick, Fredericton, N.B., E3B 5A3 Canada e MSC Software, 2 MacArthur Place, Santa Ana, CA 92707, USA f Center for Nanoscale Sys., School of Eng. & Appl. Sci., Harvard Univ., 11 Oxford St., Cambridge, MA 02139, USA |
| Abstract: | Fe3O4 magnetic nanoparticles (MNPs) were synthesized by the co-precipitation of Fe3+ and Fe2+ with ammonium hydroxide. The sodium citrate-modified Fe3O4 MNPs were prepared under Ar protection and were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and vibrating sample magnetometer (VSM). To improve the oxidation resistance of Fe3O4 MNPs, a silica layer was coated onto the modified and unmodified MNPs by the hydrolysis of tetraethoxysilane (TEOS) at 50 °C and pH 9. Afterwards, the silica-coated Fe3O4 core/shell MNPs were modified by oleic acid (OA) and were tested by IR and VSM. IR results revealed that the OA was successfully grafted onto the silica shell. The Fe3O4/SiO2 core/shell MNPs modified by OA were used to prepare water-based ferrofluids (FFs) using PEG as the second layer of surfactants. The properties of FFs were characterized using a UV-vis spectrophotometer, a Gouy magnetic balance, a laser particle size analyzer and a Brookfield LVDV-III+ rheometer. |
| Keywords: | 81.07.&minus b 74.25.Bt 74.25.Ha 75.50.Mm |
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