How to resolve the trade-off between performance and long-term stability of magnetorheological fluids

Choi, Junsok; Lim, Junyoung; Han, Seonggyun; Kim, Hoyeon; Choi, Hyoung Jin; Seo, Yongsok

doi:10.1007/s13367-022-00036-9

Cited by 8 publications

(20 citation statements)

References 114 publications

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“…Sintered Cu chips require robustness and electrical properties. UTM is a powerful tool for various mechanical properties. ,, Figure shows the shear strength of the sintered Cu chip samples with different activators and solvents. The PA-incorporated sintered Cu samples exhibited the highest mechanical properties regardless of the solvent type, similar to the electrical conductivity results.…”

Section: Resultsmentioning

confidence: 99%

Copper Sintering Pastes with Various Polar Solvents and Acidic Activators

Lee,

Han,

Kim

et al. 2023

ACS Omega

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Devices in the developing semiconductor market require high density, high integration, and detailed processing. Conventional wire bonding is inappropriate for fine-sized devices, and connected wires can be damaged by heat generation and external physical impact. Soldering is also used in advanced packaging technologies. However, disturbances and overhead joints can occur during bonding. Thus, sintering has been extensively utilized to overcome these drawbacks. Sintering pastes are pressurized and bonded, resulting in stable bonding during sintering. In this study, the composition of the Cu sintering material was examined using diverse additives and solvents. We manufactured sintering materials comprising Cu (1 μm), a solvent [methanol (MeOH), ethanol (EtOH), or ethylene glycol (EG)] and an acidic additive (benzoic acid, phthalic acid, or hexanoic acid). After the sintering process, the mechanical and electrical characteristics were compared to determine the optimal composition and bonding conditions. The optimum ratios between the acid and solvent were 4:6 (MeOH and EtOH) and 2:8 (EG) due to the high viscosity and effective long-term storage. All samples using EtOH as the solvent exhibited the highest sintering performances. The aromatic and carboxylic groups substantially improved the sintering performance and increased the electrical conductivity. Based on the O1s/Cu2p ratio (2.23%), the best sintering composition was EtOH/PA, which showed the highest electrical conductivity (ca. 104 S/m) and strength (34.0 MPa). The sintering process using various additives and solvents can be helpful to determine the sintering conditions while maintaining the electrical properties.

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Section: Resultsmentioning

confidence: 99%

Copper Sintering Pastes with Various Polar Solvents and Acidic Activators

Lee,

Han,

Kim

et al. 2023

ACS Omega

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“…The static yield strength values are determined at the point where viscosity exhibits a sudden change, indicating a significant breakdown of the original chain‐like structure. [ 43 ] Conversely, no sudden change in shear stress is observed under low shear stress conditions. The static yield strength of MN‐MRFs‐10 is measured as 6.1 kPa, 17.1 kPa, and 45.8 kPa, respectively, when subjected to magnetic fields of 92 kA m −1 , 187 kA m −1 , and 365 kA m −1 .…”

Section: Resultsmentioning

confidence: 99%

Balanced Devil Triangle: A Satisfactory Comprehensive Performance Magnetorheological Fluids with Cross‐Scale Particles

Du,

Zhao,

Liu

et al. 2023

Adv Funct Materials

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Magnetorheological (MR) fluids are magnetic responsive smart materials that are widely used in real‐time damping adjustment devices. However, a major challenge for MR fluids is balancing the constraints relationship among various key performances. This study demonstrates that by utilizing home‐made high saturation magnetization (208.0 emu g−1) nanoparticles as the second component in the preparation of cross‐scale bidisperse MR fluids, the shortcomings of monodisperse micron particles performance can be compensated, effectively balancing the relationship between various performances. This is attributed to the fact that the addition of nanoparticles enhances the density of chain structures under an applied magnetic field, while reducing the overall particle density without a magnetic field. By replacing part of micron particles with nanoparticles, the phenomenon of significant increase in zero‐field viscosity caused by the direct introduction of nanoparticles is avoided. The optimal content of nanoparticles in MR fluids is preliminarily explored, and the results indicate that Micro‐Nano bidisperse MR fluids exhibit a high dynamic yield strength (58.3 kPa when 436 kA m−1), excellent sedimentation stability (82.6% when 7 days), suitable zero‐field viscosity (1.25 Pa s when 100 s−1), and ideal reversibility. Most importantly, the simple preparation method adds significant engineering application value to these MR fluids.

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“…[ 17–38 ] However, the use of composite particles to reduce the density mismatch inevitably degrades the MR performance of composite particle‐based fluids because non‐magnetic materials are added. [ 1,2 ] As an alternative, researchers have tried to solve the sedimentation problem by using surfactants. [ 6 ] Although surfactants are useful for prolonging the settling velocity of MR fluids, they also prove detrimental to the fluid's magnetic properties (particularly magnetic saturation), which is usually the parameter the user wants to maximize to increase the maximum apparent yield stress.…”

Section: Introductionmentioning

confidence: 99%

“…[ 1–6 ] Thus, a trade‐off relationship always exists between MR performance and stability. [ 1,4 ] If the strength and stability of MR fluids can be dramatically improved at the same time, MR fluids can revolutionize certain industries. [ 8–17 ]…”

Section: Introductionmentioning

confidence: 99%

“…Magnetorheological (MR) fluids are classified as smart materials because of their unique response to external magnetic fields. [1][2][3][4][5] Under an external magnetic field, magnetic dipole-dipole interactions align the magnetic particles in the direction of the magnetic field to form a chain-like structure. [2,3] This structure transforms the MR fluid from a liquid-like state to a solid-like state, which inhibits the flow of the MR fluid and increases the viscosity by several orders of magnitude within a few milliseconds.…”

Section: Introductionmentioning

confidence: 99%

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Non‐Settling Super‐Strong Magnetorheological Fluids

Seo

2023

Small

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A magnetorheological (MR) fluid is generally called a suspension in which magnetic particles are dispersed in a non‐magnetic medium. When an external magnetic field is applied, a pseudo‐phase transition occurs within a short time to generate yield stress, and when the magnetic field is released, it returns to the suspended state. Due to these unique characteristics, it is classified as a smart material to be widely applied in various industries. High performance MR fluids require high yield stress and stability for long‐term use. However, it is very difficult to improve performance and stability simultaneously due to the limited amount of magnetic particles in the suspension and particle sedimentation caused by the density mismatch between the suspending particles and the liquid phase. In this study, an MR slurry is developed that is completely different from the MR suspension, starting from the opposite concept. An innovative non‐settling (i.e., permanently stable) magnetorheological slurry is successfully created that exhibits unprecedented ultra‐high yield stress. This result is expected to be a turning point for applying MR fluids to more diverse industries. In addition, a simple fitting equation expressing the yield stress as a function of the particle volume fraction is proposed.

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How to resolve the trade-off between performance and long-term stability of magnetorheological fluids

Cited by 8 publications

References 114 publications

Copper Sintering Pastes with Various Polar Solvents and Acidic Activators

Copper Sintering Pastes with Various Polar Solvents and Acidic Activators

Balanced Devil Triangle: A Satisfactory Comprehensive Performance Magnetorheological Fluids with Cross‐Scale Particles

Non‐Settling Super‐Strong Magnetorheological Fluids

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