Actuator Performance of a Hydrogenated Carboxylated Acrylonitrile-Butadiene Rubber/Silica-Coated BaTiO₃Dielectric Elastomer

We synthesized silica-coated barium titanate (BaTiO3) particles with different silica shell thicknesses and evaluated the effect of silica coating on the relative dielectric properties of silica-coated BaTiO3 particles. Furthermore, composite elastomers were prepared using hydrogenated carboxylated acrylonitrile-butadiene rubber (HXNBR) with a high relative dielectric constant (ϵr) and silica-coated BaTiO3 particles, and their performance as an actuator was evaluated. Both ϵr and relative dielectric loss of non-coated BaTiO3 particles increased at low frequencies (<200 Hz) associated with ionic conduction. However, ϵr and relative dielectric loss were reduced for the silica-coated BaTiO3 particles with thick silica shells, indicating that silica coating reduced ion migration. The dielectric breakdown strength increased with the thickness of the silica shell; it increased up to 80 V/μm for HXNBR/silica-coated BaTiO3 particles with 20 nm-thick silica shells. The maximum generated stress, strain, and output energy density of the composite elastomer with HXNBR (with a high relative constant) and silica-coated BaTiO3 were 1.0 MPa, 7.7%, and 19.4 kJ/m3, respectively. In contrast, the values of the same parameters for a reference elastomer (acrylic/BaTiO3; with low ϵr) were 0.4 MPa, 6.7%, and 6.8 kJ/m3 at the dielectric breakdown strength of 70 V/μm. The results indicated that the elastomers composed of HXNBR and silica-coated BaTiO3 exhibited higher generated stress, strain, and output energy density than elastomers for conventional dielectric actuators.