Material characterization of magnetorheological elastomers with corroded carbonyl iron particles: morphological images and field-dependent viscoelastic properties

High temperatures and humidity could alter the field-dependent rheological properties of MR materials. These environmental phenomena may accelerate the deterioration processes that will affect the long-term rheological reliability of MR materials such as MR elastomer (MRE). This study therefore attempts to investigate the field-dependent rheological characteristics of MRE with corroded carbonyl iron particles (CIPs). The corroded CIPs were treated with hydrochloric acid (HCl) as a way of providing realistic environments in gauging the CIPs reaction towards the ambient conditions. The corroded CIPs along with silicone rubber as a matrix material were used in the fabrication of the MRE samples. To observe the effect of HCl treatment on the CIPs, the morphological observations of MREs with non-corroded and corroded CIPs were investigated via field emission scanning electron microscopy (FESEM), energy-dispersive x-ray spectroscopy (EDX) and x-ray diffractometer (XRD). In addition, the magnetic properties were examined through the vibrating sample magnetometer (VSM), while the field-dependent rheological characteristics such as the storage modulus of MRE with the corroded CIPs were also tested and compared with the non-corroded CIPs. The results showed that the corroded CIPs possessed hydrangea-like structures. In the meantime, it was identified that a sudden reduction of up to 114% of the field-dependent MR effect of MRE with the corroded CIPs was observed as a result of the weakened interfacial bonding between the CIPs and the silicon in the outer layers of the CIPs structure

Effect of high sintering temperature on the cobalt ferrite synthesized via co-precipitation method

Magnetic particle is one of the main elements used in magnetorheological (MR) materials. In this study, the magnetic cobalt ferrite nanoparticles are successfully synthesized via co-precipitation method at different sintering temperatures. The nanoparticles are prepared in neutral condition (pH 7) at different temperatures of 900, 1000 °C for 8 h, individually. The properties of cobalt ferrite related to phase analysis, microstructure and magnetic properties were characterized by particle size analyzer (PSA), field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). The result showed that the size of cobalt ferrite powders are 16.72, 17.76 and 37.29 nm correspond to different temperatures of 900, 1000 and 1100 °C, respectively. This indicated that the higher sintering temperature induced to the synthesized cobalt ferrite, greater size of the nanoparticles will be obtained. Meanwhile, the micrograph of cobalt ferrite powders poses a polygonal shape with all exhibit the face centered cubic (FCC) structure. In the meantime, the magnetic saturation, Ms increased with the size of nanoparticles increased from 28.95 to 38.85 emu/g, simultaneously correspond to increasing in the sintering temperatures. The results underlined that the sintering temperature did affect and alter the size of CoFe2O4 nanoparticles that resulted in magnetic properties enhancement