Аннотация:Smart magnetorheological materials are widely explored. Deformational properties of magnetorheological elastomers (MREs), viscous properties of magnetorheological fluids (MRFs), damping properties of magnetorheological foams attract great attention due to their wide range of application. Magneto-deformation and magneto-dielectric effects, which have already been observed in MREs, allow to classify these materials to multiferroic materials. Additive ferroelectric particles in polymer medium allow us to investigate the influence of electric fields to magnetic properties.
It was prepared and investigated 9 samples, based on polymer Wacker Silicone (WaSi) and SIEL. The volume ratio between WaSi and SIEL was 2:1 and was selected so that polymerization process occurred at the temperature 100 C during 1 hour. The total volume concentrations of filling powder varied from 20% to 40%. The types of filling particles were magnetic hard NdFeB particles (sizes varied from 5 to 30 μm) and ferroelectric particles PZT-26 (size was about 5 μm). The amount of each type of powder was calculated from mass concentrations and densities of each material. The volume ratios between NdFeB and PZT particles were 1:1, 2:1, 1:3 and 1:6, respectively. Also the elastomer with 40 vol% of NdFeB particles (this volume concentration corresponds to 82% mass concentration) and the elastomer with 20 vol% of PZT particles were prepared. Separately the two-layer sample consisted of two elastomers was prepared: firstly the elastomer with 20vol% of PZT particles was prepared and it was used as a substrate to polymerization of the next elastomer with 20 vol% of NdFeB particles.
Magnetic properties of prepared composite samples were investigated by Vibration Sample Magnetometer (VSM) Lake Shore 7400 in the field range ±16 kOe in the temperature range from 100 K to 300 K. To carry out the measurements, the flat square shape (3*3 mm2) sample with thickness about 1 mm was cut from elastomer material. To investigate the influence of electric fields to the magnetic properties, the sample was previously placed between conducting plates (the sizes of plates were 4*4 mm2), connected to the high voltage source. The plane of the sample was parallel or perpendicular to the direction of external magnetic field. So the mutual orientation between magnetic and electric fields was parallel or perpendicular. It was found that in the external electric field (up to 5 kV) the magnetic properties of the samples with both ferroelectric and ferromagnetic particles changed compared with those in the absence of electric field.
This magnetoelectric effect was also detected by researching of the electric properties of the composites in the external magnetic fields. The electrical properties were investigated with immitance meter Aktakom 3016 (electrical capacitances were investigated). Also electric hysteresis loops of the samples were researched by Sawyer-Tower method.
The influence of PZT particles to the Young’s modulus of elastomers and the influence of external magnetic fields to the elastic properties of composited were investigated with rheometer Anton Paar model MCR 301.