Rheological and stability properties of magnetorheological fluid with superparamagnetic maghemite nanoparticles

This research is focused on the development of a new magnetorheological (MR) fluid which contains maghemite (γ-Fe2O3) nanoparticles so as to improve its performance. The performance of MR fluid is presented in terms of physical and rheological properties and its application in MR device. In this work, the γ-Fe2O3 has been synthesized using co-precipitation method and coated with oleic acid. Two types of MR fluids were prepared, bidisperse MR fluid containing carbonyl iron (CI) microparticles substituted with γ-Fe2O3 and MR fluid utilizing γ-Fe2O3 additive. MR fluid containing γ-Fe2O3 showed great improvement exhibiting reduced sedimentation rate and enhanced re-dispersibility. During the period of 50 hours, the bidisperse MR fluid with 5 wt% of γ-Fe2O3 reduced 15% of sedimentation rate and MR fluid with 1 wt% of γ-Fe2O3 additive reduced 9.6% of sedimentation rate compared to pure CI MR fluid. The rheological properties of the MR fluid were analyzed with respect to the rheological models of Bingham Plastic, Herschel Bulkley and Casson models. The rheological properties of bidisperse MR fluid revealed that the substitution of 5 wt% γ-Fe2O3 increased the yield stress by 8.5% but further substitution of γ-Fe2O3 would slightly decrease the yield stress. On the other hand, the MR fluid added with γ-Fe2O3 additive showed improvement in yield stress over the entire range of magnetic field applied. The results indicated that the addition of 1 wt% of γ-Fe2O3 in MR fluid increased the yield stress by 11.7%. The performance of MR fluid using MR valve equipped with a hydraulic bypass damper resulted in improvement of damping force when γ-Fe2O3 is added. The MR fluid with 1 wt% γ-Fe2O3 additive improved the maximum damping force up to 11.1% compared to the pure MR fluid. Therefore, the substitution and addition of γ-Fe2O3 nanoparticles in the MR fluid improved both its physical and rheological properties, hence it can potentially be used in commercial application as a simple and reliable damping device

Effect of PAO-based γ-Fe2O3 and surfactant concentration on viscosity characteristic

This is a preliminary study on the viscosity characteristics of polyalphaolefin (PAO)- based γ-Fe2O3 under zero magnetic fields. By varying the concentration of magnetic nanoparticles (MNPs), PAO-based γ-Fe2O3 with different concentrations were synthesized by co-precipitation method. The effect of this factor on the viscosity characteristic of γ-Fe2O3 (< 30 nm) was investigated on the basic of a series of rheological measurement. The use of oleic acid (OA) as a coating agent and surfactant was also investigated by varying its concentration. The results show the concentration of MNPs and the amount of OA has obvious effect on viscosity characteristics of PAO-based γ-Fe2O3. In the case of comparison between the concentrations of MNPs, higher concentration of MNPs increased the viscosity of the PAO-based γ-Fe2O3 and exhibit nearly Newtonian behavior. The large amount of OA also exhibits the increment on viscosity characteristic of MNPs. The experimental data were compared with the Bingham and Casson model and the results revealed that the rheology of the polyalphaolefin (PAO)-based γ-Fe2O3 fitted the Casson model better

Natural weathering effects on the mechanical, rheological, and morphological properties of magnetorheological elastomer (MRE) in tropical climate

Magnetorheological elastomer (MRE) materials have the potential to be used in a wide range of applications that require long-term service in hostile environments. These widespread applications will result in the emergence of MRE-specific durability issues, where durability refers to performance under in-service environmental conditions. In response, the outdoor tropical climatic environment, combined with the effects of weathering, will be the primary focus of this paper, specifically the photodegradation of the MRE. In this study, MRE made of silicone rubber (SR) and 70 wt% micron-sized carbonyl iron particles (CIP) were prepared and subjected to mechanical and rheological testing to evaluate the effects under natural weathering. Magnetorheological elastomer samples were exposed to the natural weathering conditions of a tropical climate in Kuala Lumpur, Malaysia, for 30 days. To obtain a comprehensive view of MRE degradation during natural weathering, mechanical testing, rheology, and morphological evaluation were all performed. The mechanical and rheological properties test results revealed that after 30 days of exposure and known meteorological parameters, Young's modulus and storage modulus increased, while elongation at break decreased. The degradation processes of MRE during weathering, which are responsible for their undesirable change, were given special attention. With the help of morphological evidence, the relationship between these phenomena and the viscoelastic properties of MRE was comprehensively defined and discussed.UTM Fundamental Research [22H14]; Professional Development Research University (PDRU) [06E29]; Universitas Sebelas Maret through hibah non APBN 2022 LPPM; Ministry of Education, Youth and Sports of the Czech Republic [RP/CPS/2022/007]06E29; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Universiti Teknologi Malaysia, UTM: 22H14; Universitas Sebelas Maret, UNS; Lembaga Penelitian dan Pengabdian Kepada Masyarakat, LPPM: RP/CPS/2022/00

Synthesis, characterization and magnetorheological properties of carbonyl iron suspension with superparamagnetic nanoparticles as an additive

Magnetorheological (MR) fluids are suspensions of micron-sized particles dispersed in carrier fluid. Due to high density magnetic particles, MR fluids are facing the problem with the instability of the suspension caused by high settling rate. Recently, researches have been conducted on the advantages of using the mixture of magnetic nanoparticles and microparticles, called bidisperse MR fluids. However, even though the sedimentation stability is improved, there is a reduction in dynamic yield stress when the nanoparticle is introduced. In this work, the investigation of magnetic iron nanoparticles (γ-Fe2O3) as an additive to magnetic carbonyl iron (CI) suspension has been proposed so as to improve the sedimentation stability and redispersibility, but at the same time enhance the MR performance. The results indicated that the addition of nanoparticles reduced the sedimentation rate, improved redispersibility and enhanced the rheological performance of MR fluids as the particle fill the voids between the microparticles and strengthened the interparticle chains contributing to well-arranged particle structure

Natural Weathering Effects on the Mechanical, Rheological, and Morphological Properties of Magnetorheological Elastomer (MRE) in Tropical Climate

Magnetorheological elastomer (MRE) materials have the potential to be used in a wide range of applications that require long-term service in hostile environments. These widespread applications will result in the emergence of MRE-specific durability issues, where durability refers to performance under in-service environmental conditions. In response, the outdoor tropical climatic environment, combined with the effects of weathering, will be the primary focus of this paper, specifically the photodegradation of the MRE. In this study, MRE made of silicone rubber (SR) and 70 wt% micron-sized carbonyl iron particles (CIP) were prepared and subjected to mechanical and rheological testing to evaluate the effects under natural weathering. Magnetorheological elastomer samples were exposed to the natural weathering conditions of a tropical climate in Kuala Lumpur, Malaysia, for 30 days. To obtain a comprehensive view of MRE degradation during natural weathering, mechanical testing, rheology, and morphological evaluation were all performed. The mechanical and rheological properties test results revealed that after 30 days of exposure and known meteorological parameters, Young&rsquo;s modulus and storage modulus increased, while elongation at break decreased. The degradation processes of MRE during weathering, which are responsible for their undesirable change, were given special attention. With the help of morphological evidence, the relationship between these phenomena and the viscoelastic properties of MRE was comprehensively defined and discussed