Carbonyl iron particles (CIPs) is one of the key components in magnetic rubber, known as magnetorheological elastomer (MRE). Apart from the influence of their sizes and concentrations, the role of the particle’ shape is pronounced worthy of the attention for the MRE performance. However, the usage of CIPs in MRE during long-term applications may lead to corrosion effects on the embedded CIPs, which significantly affects the performance of devices or systems utilizing MRE. Hence, the distinctions between the two types of MRE embedded in different shapes of spherical and plate-like CIPs, at both conditions of non-corroded and corroded CIPs were investigated in terms of the field-dependent rheological properties of MRE. The plate-like shape was produced from spherical CIPs through a milling process using a rotary ball mill. Then, both shapes of CIPs individually subjected to an accelerated corrosion test in diluted hydrochloric (HCl) at different concentrations, particularly at 0.5, 1.0, and 1.5 vol.% for 30 min of immersion time. Eight samples of CIPs, including non-corroded for both CIPs shapes, were characterized in terms of a morphological study by field emission scanning electron microscope (FESEM) and magnetic properties via vibrating sample magnetometer (VSM). The field-dependent rheological properties of MREs were analyzed the change in the dynamic modulus behavior of MREs via rheometer. From the application perspective, this finding may be useful for the system to be considered that provide an idea to prolong the performance MRE by utilizing the different shapes of CIPs even when the material is fading.
Carbonyl iron particles (CIPs) embedded in magnetorheological elastomers (MREs) as magnetic filler play a dominant candidate that can affect resultant properties of MREs including the field-dependent viscoelasticity. In this work, the effects of corrosion rate on the rheological properties of MREs are experimentally investigated. The CIPs undergo an accelerated corrosion test in diluted hydrochloric (HCl) acid at various concentrations, particularly at 0.5, 1.0 and 1.5 vol.% for 30 min immersion time, individually. Four samples of CIPs, including the non-corroded one are prepared, and their morphological characterization are observed via field emission scanning electron microscope (FESEM), that equipped with energy dispersive x-ray spectroscopy (EDS) for elemental compositions. In addition, x-ray diffraction (XRD) is used to identify the crystalline phase structure of the samples. In order to examine the corrosion rate of each sample, weight-loss method is used by pressing the CIPs into pellet shape and being immersed in the respective concentrations of HCl. It is shown that the corrosion rate of CIPs is increased with the increasing of HCl concentration in which higher weight loss of the measured pallet CIPs is observed. Meanwhile, the field-dependent rheological properties of MREs are investigated via rheometer to analyze the change in dynamic modulus of MREs such as storage modulus, loss factor and absolute MR effect. These experimental results indicate that MRE samples with higher corrosion rate of CIP exhibit lower storage modulus, loss factor and MR effect, as this subsequently would deteriorate the performance of MRE. Therefore, it is identified that the purity of CIP plays the most important contribution towards the field-dependent viscoelastic properties of MRE for a long period use of the material.
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