Monz S, Tschöpe A, Birringer R
FR 7.3 Technische Physik, Geb. D2 2, Universität des Saarlandes, 66041 Saarbrücken, Germany.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Aug;78(2 Pt 1):021404. doi: 10.1103/PhysRevE.78.021404. Epub 2008 Aug 15.
CoFe2O4-based ferrogels were prepared with both isotropic and anisotropic orientation of the magnetic anisotropy axis of the magnetic particles. In contrast to the superparamagnetic properties of the ferrofluid, the ferrogels exhibit hysteresis, indicating that (i) a significant fraction of magnetic particles has volumes beyond the critical value that allows Néelian relaxation, and (ii) a mechanical interaction between the particles and the polymer network exists, which prevents the particles from Brownian relaxation. The contribution of such particles was investigated by field cooling field warming and zero field cooling field warming measurements as well as temperature-dependent magnetization measurements. By application of an external field during gel polymerization, a magnetic texture was induced as confirmed by the angular dependence of mRmS and HC . The net-magnetic torque, exerted on the magnetic particles in an anisotropic ferrogel in combination with the soft elastic properties of the gel matrix enables the application as torsional soft actuator as demonstrated.
制备了具有磁性颗粒磁各向异性轴各向同性和各向异性取向的基于CoFe₂O₄的铁凝胶。与铁磁流体的超顺磁性特性相反，铁凝胶表现出磁滞现象，这表明：（i）相当一部分磁性颗粒的体积超过了允许奈尔弛豫的临界值；（ii）颗粒与聚合物网络之间存在机械相互作用，这阻止了颗粒的布朗弛豫。通过场冷场热和零场冷场热测量以及与温度相关的磁化测量研究了此类颗粒的贡献。通过在凝胶聚合过程中施加外部磁场，如通过mRmS和HC的角度依赖性所证实的那样，诱导出了磁织构。如所展示的那样，作用在各向异性铁凝胶中磁性颗粒上的净磁转矩与凝胶基质的软弹性特性相结合，使得其能够用作扭转软致动器。
