Stable Magnetorheological Fluids Containing Bidisperse Fillers with Compact/Mesoporous Silica Coatings

Area of Science:

• Materials Science
• Nanotechnology
• Fluid Dynamics

Background:

• Magnetorheological (MR) fluids exhibit poor kinetic stability due to particle sedimentation.
• This instability limits their practical applications in various engineering fields.

Purpose of the Study:

• To suppress sedimentation in MR fluids using a novel coating technique.
• To enhance the kinetic stability and overall performance of MR fluids.

Main Methods:

• Fabrication of magnetic sub-micro additives coated sequentially with compact and mesoporous silica.
• Characterization using transmission electron microscopy, SEM/EDX, and FTIR spectroscopy.
• Evaluation of magnetorheological performance using a modified Cross model and sedimentation analysis with a novel S-model.

Main Results:

• Coating significantly increased specific surface area from 47 to 312 m²/g.
• Improved sedimentation profile with up to a six-fold reduction in sedimentation rate.
• Magnetization slightly decreased, but magnetorheological performance remained acceptable.

Conclusions:

• The bidispersal and silica coating technique effectively enhances the kinetic stability of MR fluids.
• The developed sub-micro additives prevent particle aggregation and improve sedimentation behavior.
• The novel S-model provides robust fitting for sedimentation curves in magnetorheology.