Compressive Modulus of Ferrite Containing Polymer Gels

Abstract

The mechanical properties of magnetic gel have been investigated. Magnetic gels, which consist of finely dispersed powder of barium ferrite ( BaFe 12 O 19) and poly vinyl alcohol (PVA), have been synthesized. The diameter of barium ferrite is less than 45 μm. The magnetic gels varying with ferrite concentration, crosslinking densities were prepared by mixing 10 wt.% PVA aqueous solution and barium ferrite using glutaraldehyde as a crosslinking agent in the presence of HCl. The diameter of barium ferrite is large enough to have a permanent magnetic moment. We applied a 10 kOe magnetic field in order to saturate the magnetic moment of barium ferrite. After magnetization, the compressive modulus was estimated with an ultrasonic method in order to find the influence of magnetization. Ultrasonic measurements were carried out using burst waves at 10 MHz and 295.5 K. The modulus of magnetized gel was found to depend on the concentration of magnetic substance, the crosslinking density, and the degree of swelling. It was clear that the modulus of magnetized gel was higher than the gel without magnetization for all samples. The change in modulus to the initial modulus ΔM′/M′o for 10 wt.% and 15 wt.% of ferrite concentration was about 0.28% and 0.4% in a lower density region, respectively. Moreover, the change in modulus ΔM′/M′o was constant in a lower density region however it strongly depends on the density in a higher density region. When the stress direction is perpendicular to the magnetization, the change in modulus increased. On the contrary, the change in modulus decreased when the stress direction is parallel to the magnetization. As increasing the density, the distance between magnetic substances become short and therefore the magnetic interaction is more significant in a higher density region.

Giant Complex Modulus Reduction of κ‐Carrageenan Magnetic Gels

“…We have investigated the longitudinal modulus of the magnetic gel, containing magnetic particles with the mean diameter of 15 mm, using 10 MHz ultrasonic waves. [3][4][5] The longitudinal modulus M 0 after magnetization was higher than that before magnetization analyzed by the classical relation M 0 ¼ rV 2 , where r and Vare the density and the sound velocity of gels, respectively. This result was consistent with one of the magnetic gel containing magnetic fluids.…”

Enhancement in Magnetorheological Effect of Magnetorheological Elastomers by Surface Modification of Iron Particles

“…Lokander and Stenberg have showed that the relative MR effect is higher in the softer elastomers [18]. However, MR elastomers based on those soft elastomer matrices, like silicone rubbers [20], gels [21,22], or poly (vinyl alcohol) [11] are usually ill-suited for most load-bearing applications due to their low strength and reduced fatigue life [3]. Further, the addition of plasticizer to MR elastomers has also been proved effective in decreasing the zero-field shear modulus and enhancement of the relative MR effect of materials [14].…”

Electro- and Magneto-Rheological Materials: Stimuli-Induced Rheological Functions

“…Network polymer gels are also used as the ER/MR materials that have the field-responsive changes in their elastic properties similarly to the elastomers [101][102][103][104][105][106][107][108][109][110]. The gels generally contain considerable amount of solvent, which swells the polymer network and soften the material.…”

“…Their characteristic behaviors such as abrupt elongation and contraction under nonuniform magnetic field have attracted much attention [105,106]. The longitudinal modulus of magnetic gels consisting of magnetized barium ferrite and poly(vinyl alcohol) has been studied with ultrasonic waves [107,108]. The gels were prepared by mixing 10 wt% poly(vinyl alcohol) aqueous solution and magnetic particle of barium ferrite (BaFe 12 O 19 ).…”