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- 저자 : Hongchao Cui (검색결과 2 건)
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Hongchao Cui,Jiahao Xu,Jiajia Zhang,Jingjing Lu,Zhenkun li 한국자기학회 2023 Journal of Magnetics Vol.28 No.1
Ferrofluids as a new kind of nano-functional material, possessing both magnetism of solid material and fluidity of liquid material, thus, they have extensive scientific research and engineering application value. To avoid the defects of conventional non- or single silane coupling agent in silicone oil-based ferrofluid preparation, TEOS and KH-792 were introduced as surfactants to modify Fe3O4 magnetic nanoparticles (MNPs). Silicone oil modified by carboxylic acid was used as based liquid because of improved compatibility with surfactants. Silicone oil-based ferrofluid was prepared by high-energy ball milling method, and its rheological properties were studied. The saturated magnetization of the silicon oil based ferrofluid was 142.71 Gs. When external magnetic field was applied, the MNPs formed a chain structure in the microscope. The viscosity of ferrofluid increased with magnetic field and the shear stress rose with shear rate. The viscosity decreased steeply with increasing temperature and shear rate. The viscosity of silicone oil-based ferrofluid was 950 mPa·s at 25 °C and can vary from 2044 mPa·s at 5 °C to 465 mPa·s at 40 °C. The ferrofluid transformed from a Newtonian fluid at zero magnetic field to a shear-thinning pseudoplastic Bingham fluid when an external magnetic field was applied. The viscosity varied from 1.37 to 2.38 × 105 mPa·s at zero shear rate. While, when magnetic field varied from 0 kA/ rose to 160 kA/m, the viscosity increased obviously and this phenomenon became more pronounced as the shear rate decreased. When magnetic field intensity was higher than 64 kA/m, the viscosity increased slowly with increasing shear rates and viscosity curve was close to a straight line at 100 s-1. This study expands the idea of exploring the synthesis of ferrofluids with mixed surfactants. Silicone oil-based ferrofluid is expected to have unique application prospects in the aerospace field, especially in space damping, sealing and biomedicine.
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Research on the rheological properties of a silicone oil-based ferrofluid
Zhang Jiajia,Cui Hongchao,Han Shida,Li Zhenkun,Lu Jingjing 한국유변학회 2023 Korea-Australia rheology journal Vol.35 No.3
To study the overall rheological characteristics of the silicone oil-based ferrofluid, a chemical co-precipitation method was adopted for preparation, and transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) were used for characterization. The average size of Fe3O4 magnetic particles was 10.4 nm and the saturation magnetization of the ferrofluid was 5.98 emu/g. Then, the fluidity, magnetoviscous effect and viscoelasticity of the ferrofluid were studied using a rotational rheometer. The results showed obvious shear thinning of the silicone oil-based ferrofluid under an external magnetic field, and the yield stress of the ferrofluid could not be accurately obtained by fitting the flow curve with an H–B model at a continuous shear rate. A strong magnetoviscous effect could be observed at different shear rates and temperatures. The magnetoviscous parameter R increased with the increase of temperature and its variation decreased with the increase of shear rate. Moreover, based on the magnetic particle chain model and the viscosity–temperature characteristics of the base carrier liquid, different mechanisms of temperature influence on the magnetoviscous effect were analyzed. Finally, a discussion of the microstructure evolution mechanism of the ferrofluid in the modulus changing with frequency was presented through the viscoelastic analysis of the silicone oil-based ferrofluid.
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