Journal of Physics: Conference Series PAPER • OPEN ACCESS Magnetic effect in viscosity of magnetorheological fluids To cite this article: H A Fonseca et al 2016 J. Phys.: Conf. Ser. 687 012102   View the article online for updates and enhancements. Related content Magnetorheological fluids with two- component dispersed phase E V Korobko, Z A Novikova and M A Zhurauski - Using magnetorheological fluids in an innovative hybrid bicycle damper Y J Shiao and T S Nguyen - Review of magnetorheological fluids and nanofluids thermal behaviour M S A Rahim and I Ismail - Recent citations Effects of magnetic field on the spreading dynamics of an impinging ferrofluid droplet Abrar Ahmed et al - One-way sound propagation via spatio- temporal modulation of magnetorheological fluid Aditya Nanda and M. Amin Karami - Active Control of a Small-Scale Wind Turbine Blade Containing Magnetorheological Fluid Fevzi Bolat and Selim Sivrioglu - This content was downloaded from IP address 200.24.16.225 on 20/11/2018 at 15:41 https://doi.org/10.1088/1742-6596/687/1/012102 http://iopscience.iop.org/article/10.1088/1742-6596/602/1/012033 http://iopscience.iop.org/article/10.1088/1742-6596/602/1/012033 http://iopscience.iop.org/article/10.1088/1757-899X/103/1/012043 http://iopscience.iop.org/article/10.1088/1757-899X/103/1/012043 http://iopscience.iop.org/article/10.1088/1757-899X/100/1/012040 http://iopscience.iop.org/article/10.1088/1757-899X/100/1/012040 http://dx.doi.org/10.1016/j.jcis.2018.07.110 http://dx.doi.org/10.1016/j.jcis.2018.07.110 http://dx.doi.org/10.1121/1.5048181 http://dx.doi.org/10.1121/1.5048181 http://dx.doi.org/10.1121/1.5048181 http://dx.doi.org/10.3390/mi9020080 http://dx.doi.org/10.3390/mi9020080 http://dx.doi.org/10.3390/mi9020080 https://oasc-eu1.247realmedia.com/5c/iopscience.iop.org/417970551/Middle/IOPP/IOPs-Mid-JPCS-pdf/IOPs-Mid-JPCS-pdf.jpg/1? Magnetic effect in viscosity of magnetorheological fluids H A Fonseca1, E Gonzalez1, J Restrepo2, C A Parra1 and C Ortiz1 1 Universidad Pedagógica y Tecnológica de Colombia, Tunja, Boyacá, Colombia. 2 Universidad de Antioquia, Medellín, Antioquia, Colombia. E-mail: hugoalexander.fonseca@uptc.edu.co Abstract. In this work the study of viscosity is presented for a magnetorheological fluid made from iron oxides micrometre, under an external magnetic field. The material was characterized by magnetic loops in a vibrating sample magnetometer and its crystal structure by X-ray diffraction. The results show that saturation magnetization and coercive field have dependence with the powder size. The material has different crystal structure which lattice parameters were determined by Rietveld refinement. The viscosity of the magnetorheological fluid was measured by a viscometer with rotational symmetry with and without external field. This result evidence a dependency on the size, percentage iron oxide and the applied magnetic field, it is due to the hydrodynamic volume of iron oxide interacts with the external magnetic field, increasing the flow resistance. 1. Introduction The magnetorheological fluids are non-Newtonian fluids consisting of magnetic particles, example magnetite, dispersed in a liquid carrier that can change its rheological properties under application of an external magnetic field. Moreover, these fluids are characterized by an apparent viscosity, which decreases as spindle speed increase. Some of its applications are in suspension systems, magnetic separation industry and biomedicine [1-3]. In the preparation this class of fluids, particles of size micrometric or nanometre coated with a surfactant. It is necessary to generate a hydrodynamic volume that increase surface interaction between the magnetic particles and the carrier liquid and thus to reduce effects of aggregation and interaction in the presence of external magnetic field. These particles can be achieved chemically (cooprecipitation) or mechanical (milling) processes. 2. Experimental Iron oxide powders were characterized by vibrating sample magnetometer to have an appreciation of behaviour magnetic and X-ray diffraction to quantify your composition and to know the crystalline structure. The magnetorheological fluid was prepared with micrometre-sized powders (T5=15μm y T2=40μm), oleic acid was used as surfactant, and the oxide/oleic acid ratio was kept at 1/1.5 in volume and SAE engine oil as carrier liquid, the samples are labelled T2 (15%), T2 (20%) and T5 (20%), the percentage value corresponds to the amount of oxide in the ferrofluid. The samples were heat treated (45oC up to 60oC in oleic acid and up to 50oC in engine oil SAE) in a mechanical shaker at cycles of 0.5, 1, 1.5, 2 hours to 43rpm. This process an activation chemical surface and suspension stability of magnetite in the liquid carrier is present due to the surfactant. The viscosity measurement was performed for various spindle speed without magnetic field and to different values of magnetic field with constant shearing rate at room temperature. IMRMPT2015 IOP Publishing Journal of Physics: Conference Series 687 (2016) 012102 doi:10.1088/1742-6596/687/1/012102 Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under licence by IOP Publishing Ltd 1 3. Result and discussion In order to detect and quantify the phases, we refined the X-ray pattern of the sample by the Rietveld method. The experimental pattern as shown in Figure 1 was fitted using two phases, 89% magnetite, and 11% hematite, with cubic (Fd3m) and hexagonal (R3c) structures, respectively. With a refined adjustment of χ2=1.905. Figure 1. X-ray diffraction pattern and Rietveld fit of iron oxide sample. In the Rietveld refinement it was necessary to introduce three cubic structures magnetite and a hematite hexagonal structure, which lattice parameters, are listed in Table 1. Table 1. Refined lattice parameter of phases presents in the iron oxide: three of magnetite and one of hematite sample. Phase Structural parameters a b c Magnetite 8.3893(4) 8.3893(4) 8.3893(4) 8.420(3) 8.420(3) 8.420(3) 8.373(3) 8.373(3) 8.373(3) Hematite 5.026(1) 5.026(1) 13.735(3) The hysteresis loops show that the magnetic parameters such as saturation magnetization, coercive force and remanent magnetization are influenced by the magnetic domains state of the samples, which in turn it is a function of grain size [4,5]. That is, as it is increase the size of the oxide, saturation magnetization lowers (Figure 2) which values are within the range of a magnetically soft material as shown in Table 2, which is an important factor in the development of magnetorheological fluids. The magnetic behaviour of the oxide is due to the contribution of the crystal structures present in 89% magnetite and hematite 11%. Hematite presence generates slight changes in the magnetic properties of the sample compared to a pure magnetite [4,5]. IMRMPT2015 IOP Publishing Journal of Physics: Conference Series 687 (2016) 012102 doi:10.1088/1742-6596/687/1/012102 2 Figure 2. Iron oxide Hysteresis loops. Table 2. Characteristic magnetic parameters: saturation magnetization Ms, remanent magnetization Mr, coercive field Hc. T2 T5 Ms (emu/g) 81.59 77.53 Mr (emu/g) 7.02 8.67 Hc (Oe) 132.2 144.62 The behaviour viscosity with spindle speed without applying field is shown in Figure 3(a). The viscosity versus spindle speed evidences a non-Newtonian behaviour. The values increase when the size of the oxide decreases, indicating better stability of oxide-oleic acid-oil [6,7]. The hydrodynamic volume is uniform and stable with the oxide size decrease, increasing flow resistance [8]. Figure 3(a). Viscosity behaviour varying the spindle speed with absence of magnetic field. Figure 3(b). Viscosity behaviour varying the magnetic field with spindle speed to 2rpm. IMRMPT2015 IOP Publishing Journal of Physics: Conference Series 687 (2016) 012102 doi:10.1088/1742-6596/687/1/012102 3 In the Figure 3(b) show the viscosity in function of field applied for the spindle speed in this case was 2rpm. The change appears in several orders of magnitude in viscosity, due to micrometre oxide tends to align the applied field, increasing the torque in the spindle which registers the viscosity of the magnetorheological fluid [8] and it is caused by the formation of a robust chain structure. The behaviour observed in Figure 3(a) can be characterized by a Bingham model with a yield stress, meaning that the suspensions acts as a solid-liked material when exposed to an external shear stress [9,10]. Regarding the oxide volume concentration, the viscosity increases due to the increases the hydrodynamic volume net giving the material a better response to the magnetic field. In the case of size of oxide, the viscosity does not depend on size in the presence of a magnetic field because the powder rotates seeking their preferred orientation. Magnetite, which contributes more in the magnetization, is the one that gives the orientation of the oxide in the fluid due to the external field. 4. Conclusions The magnetorheological fluids prepared have a dependency on spindle speed acting as a plastic fluid conforms to the model Bingham. A clear dependence of the magnetorheological fluid with the magnetic field applied it was found that, because the micrometre oxide easily responds generating a preferred orientation to the applied field, thus increasing the resistance to fluid flow. Oleic acid surfactant satisfactorily fulfils the function of preventing the aggregation of magnetite due to magnetic interactions, thus behaving as a paramagnetic fluid. The crystal structures give an unusual magnetic response of the sample although their values are within those reported in the literature for a pure magnetite. Acknowledgments The authors thank the Centro de Gestión de Investigación y Extensión (CEDEC) of the Faculty of Engineering, call 001 for research groups. 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