Department of Polymer Science and Engineering, Graduate School of Engineering, Yamagata University, Yonezawa 992-8510, Japan.
J Phys Chem B. 2012 Oct 11;116(40):12341-8. doi: 10.1021/jp3049372. Epub 2012 Sep 26.
A new class of magnetoelastic gel that demonstrates drastic and reversible changes in storage modulus without using strong magnetic fields was obtained. The magnetic gel consists of carrageenan and carbonyl iron particles. The magnetic gel with a volume fraction of magnetic particles of 0.30 exhibited a reversible increase by a factor of 1400 of the storage modulus upon a magnetic field of 500 mT, which is the highest value in the past for magnetorheological soft materials. It is considered that the giant magnetoelastic behavior is caused by both high dispersibility and high mobility of magnetic particles in the carrageenan gel. The off-field storage modulus of the magnetic gel at volume fractions below 0.30 obeyed the Krieger-Dougherty equation, indicating random dispersion of magnetic particles. At 500 mT, the storage modulus was higher than 4.0 MPa, which is equal to that of magnetic fluids, indicating that the magnetic particles move and form a chain structure by magnetic fields. Morphological study revealed the evidence that the magnetic particles embedded in the gel were aligned in the direction of magnetic fields, accompanied by stretching of the gel network. We conclude that the giant magnetoelastic phenomenon originates from the chain structure consisting of magnetic particles similar to magnetic fluids.
一种新的磁弹性凝胶，无需使用强磁场即可表现出存储模量的剧烈和可逆变化。该磁凝胶由卡拉胶和羰基铁颗粒组成。当磁场为 500mT 时，具有 0.30 体积分数的磁性颗粒的磁凝胶的储能模量可发生可逆增加 1400 倍，这是过去磁流变软材料的最高值。认为巨磁弹性行为是由卡拉胶凝胶中磁性颗粒的高分散性和高迁移率引起的。体积分数低于 0.30 的磁凝胶的场外储能模量符合 Krieger-Dougherty 方程，表明磁性颗粒呈随机分布。在 500mT 时，储能模量高于 4.0MPa，与磁流体相当，表明磁性颗粒在磁场的作用下移动并形成链状结构。形态学研究表明，嵌入凝胶中的磁性颗粒沿磁场方向排列的证据，伴随着凝胶网络的拉伸。我们得出结论，巨磁弹性现象源自类似于磁流体的由磁性颗粒组成的链状结构。
