First MnO2-based electrorheological fluids: high response at low filler concentration
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Nanoparticles of MnO2 with different shapes (needle-like α-MnO2 and spherical δ-MnO2) were proposed as promising fillers for electrorheological fluids (ERFs). A thorough study of the dielectric properties of α-MnO2 and δ-MnO2 suspensions in silicone oil enabled estimation of the values of their dielectric permittivity and dielectric relaxation times. The study of MnO2-filled materials with various filler contents, and under various electric field strengths, in shear and uniaxial tensile and compressive stress regimes, revealed that needle-like α-MnO2 nanoparticles, in comparison with spherical δ-MnO2 particles, lead to better mechanical properties of the fluids. The most intriguing property of MnO2-based electrorheological fluids is their high electrorheological response at low filler content: ERF containing only 4.5 vol.% of α-MnO2 in silicone oil demonstrated a 18 kPa tensile strength in a 5 kV electric field.
KeywordsElectrorheologic materials MnO2 polymorphs Dielectric permittivity Dielectric relaxation time Shear stress Tensile stress Compressive stress Filler content
The X-ray diffraction and electron microscopy measurements were performed using shared experimental facilities supported by the IGIC RAS state assignment.
The work was supported by the Russian Science Foundation (grant no. 16-13-10399).
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