Hierarchically Structured Fe₃O₄ Nanoparticles for High-Performance Magnetorheological Fluids with Long-Term Stability

Abstract

The magnetic Fe3O4 nanoparticles were produced by chemical precipitation from ferric chloride (FeCl3) and ferrous chloride (FeCl2) in an alkaline medium (ammonia hydroxide). The magnetic particle suspension was stabilized with citric acid. Hierarchically structured Fe3O4 (HS-Fe3O4) particles of submicrometer size were successfully produced from citric acid-capped Fe3O4 solution by using a simple electrospray (ES) process and applied for magnetorheolgical (MR) fluids. Submicrometer-sized spherical HS-Fe3O4 particles were formed by evaporation of the solvent and agglomeration of capped Fe3O4 particles during the ES process. With formation of hierarchically structured particles, the density of HS-Fe3O4 particles (ρ = 3.32 g/cm3) was noticeably decreased from that of the capped Fe3O4 (ρ = 4.29 g/cm3) without use of light materials, while the saturation magnetization was comparable to primary capped Fe3O4 (M s = 73 emu/g). The MR fluid based on the submicrometer HS-Fe3O4 particles showed better MR performance with a large static yield stress (337 Pa), which was 300% greater than that of the hollow polymer/Fe3O4 suspension. Reduced density mismatch between the particles and the silicon oil medium significantly improved the stability of the HS-Fe3O4 suspension compared to the pure Fe3O4 suspension. The high MR performance and the improved sedimentation stability showed a possibility of the practical application of the submicrometer HS-Fe3O4 particle suspensions to microfluidic devices.

Synergistic Effects of Nonmagnetic Carbon Nanotubes on the Performance and Stability of Magnetorheological Fluids Containing Carbon Nanotube-Co0.4Fe0.4Ni0.2 Nanocomposite Particles

“…Because of the very high M s value of Co 0.4 Fe 0.4 Ni 0.2 , the CNT-Co 0.4 Fe 0.4 Ni 0.2 composite also shows a high M s value of 108 emu/g, which is even greater than that of bare Fe 3 O 4 particles. This is substantially greater than the previously reported values for Fe 3 O 4 -based composite particles. ,, …”

“…Unlike Fe 3 O 4 and its composites, which are paramagnetic and exhibit a very narrow hysteresis curve and a small coercive field, the Co 0.4 Fe 0.4 Ni 0.2 and the CNT-Co 0.4 Fe 0.4 Ni 0.2 composite showed ferromagnetic character with a weak coercive field and low remanent magnetization . The saturation magnetization ( M s ) value for Co 0.4 Fe 0.4 Ni 0.2 was 165 emu/g, which is more than two times greater than that of Fe 3 O 4 , approximately 70–80 emu/g. , This value is even greater than that reported by Reddy et al for Co 0.4 Fe 0.4 Ni 0.2 . This improvement in M s is attributed to the use of flowing N 2 in the early stage of the synthesis, which can prevent the oxidation of intermediates formed upon injection of the NaOH solution.…”

“…For example, carbon nanotube-Fe 3 O 4 (CNT-Fe 3 O 4 ) composites have been fabricated and used in MR fluids. , The resultant MR fluids exhibit remarkable stability compared with that of the pure Fe 3 O 4 and other Fe 3 O 4 -based composite MR fluids because of the formation of self-supporting three-dimenstional network structures. , Although CNT-Fe 3 O 4 composites have led to better long-term stability of MR fluids, they have been found to adversely affect MR properties in a trade-off relationship. − Since the addition of nonmagnetic CNTs reduces the amount of magnetic Fe 3 O 4 in an MR fluid, the MR performance of the resultant CNT-Fe 3 O 4 composite-based fluids is inferior to that of bare Fe 3 O 4 -based fluids. As a solution to this problem, we used a simple electrospray process to fabricate hierarchically structured Fe 3 O 4 (HS-Fe 3 O 4 ) nanoparticles that do not contain nonmagnetic polymers . The secondary HS-Fe 3 O 4 showed a saturation magnetization value comparable to its primary Fe 3 O 4 nanoparticles while having a lower density because of pores in the secondary particles.…”

Dynamic and creep and recovery performance of Fe3O4 nanoparticle and carbonyl iron microparticle water-based magnetorheological fluid

“…The MR fluid comprises magnetic particles of micron-sized carbonyl iron (CI) and metal oxides dispersed into a nonmagnetic carrier medium. Under the applied external magnetic field, the magnetic particles are aggregated alongside the direction of a magnetic field to form a chain structure because of the magnetic dipole-dipole interaction among the magnetic particles (Choi et al, 2020;Li et al, 2004). The formed chain structure increases the viscosity of the fluid, and thus MR fluid changes rapidly from a liquid-like to a solid-like state in milliseconds (Biao et al, 2014;Ghaffari et al, 2014;Maurya and Sarkar, 2020a).…”

“…Therefore, the dynamic mechanical performance and creep and recovery properties measurements are very useful for some engineering applications. Some engineering applications of MR fluids in such conditions are car suspension, shock absorbers in buses and motorcycles, seismic vibration control which will operate under the resonance frequency of the building and bridges by absorbing external impacts, shock waves, and oscillations that can cause harm, within the structure (Choi et al, 2020;Dyke et al, 1996), the MR dampers can be used in a prosthetic knee to give fast shock absorbing and make the user feel more natural feet under axial force (Ravishankar and Mahale, 2015). However, the advancement in MR fluids and MR devices is essential to the understanding of MR fluids response under such working modes and conditions.…”