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Coarsening dynamics of ferromagnetic granular networks—experimental results and simulations†
Soft Matter ( IF 2.9 ) Pub Date : 2017-12-11 00:00:00 , DOI: 10.1039/c7sm00796e
Armin Kögel 1, 2, 3, 4 , Pedro A. Sánchez 5, 6, 7 , Robin Maretzki 1, 2, 3, 4 , Tom Dumont 1, 2, 3, 4 , Elena S. Pyanzina 8, 9, 10 , Sofia S. Kantorovich 5, 6, 7, 8, 9 , Reinhard Richter 1, 2, 3, 4
Affiliation  

We investigate the phase separation of a shaken mixture of glass and magnetised steel spheres after a sudden quench of the shaker amplitude. After quenching, transient networks of steel spheres emerge in the experiment. For the developing network clusters we estimate the number of spheres in them, and the characteristic path lengths. We find that both quantities follow a log-normal distribution function. Moreover, we study the temporal evolution of the networks. In the sequence of snapshots we observe an initial regime, where the network incubates, followed by a temporal regime where network structures are elongated and broken, and finally a regime where the structures have relaxed to compact clusters of rounded shapes. This phaenomenology resembles the initial, elastic and hydrodynamic regimes observed by H. Tanaka [J. Phys.: Condens. Matter, 2000, 12, R207] during the viscoelastic phase separation for dynamically asymmetric mixtures of polymers. In order to discriminate the three regimes we investigate in the experiment order parameters like the mean number of neighbors and the efficiency of the networks. In order to capture the origin for a viscoelastic phase separation in our granular mixture, we use a simple simulation approach. Not aiming at a quantitative description of the experimental results, we rather use the simulations to define the key interactions in the experimental system. This way, we discover that along with dipolar and steric interactions, there is an effective central attraction between the magnetised spheres that is responsible for the coarsening dynamics. Our simulations show as well three regimes in the evolution of characteristic order parameters.

中文翻译:

铁磁颗粒网络的粗化动力学—实验结果和模拟

我们研究了振动器振幅突然猝灭后玻璃和磁化钢球的振动混合物的相分离。淬火后,实验中出现了钢球的瞬态网络。对于发展中的网络集群,我们估计其中的球体数量以及特征路径长度。我们发现两个量都遵循对数正态分布函数。此外,我们研究了网络的时间演变。在快照序列中,我们观察到最初的状态(网络在其中孵化),然后观察到时间状态(在该状态中网络结构被拉长和破坏),最后观察到一个状态,在该状态中结构已松弛到紧凑的圆形簇。这种现象学类似于H. Tanaka [观察到的初始,弹性和流体动力状态。J.物理:凝结。事,2000年,12,R207]在粘弹性相分离过程中动态不对称的聚合物混合物。为了区分这三种情况,我们在实验中研究了阶数参数,例如邻居的平均数和网络效率。为了捕获颗粒混合物中粘弹性相分离的起源,我们使用了一种简单的模拟方法。我们的目标不是定量描述实验结果,而是使用模拟来定义实验系统中的关键相互作用。这样,我们发现,除了偶极和空间相互作用外,磁化球体之间还存在有效的中心吸引力,这是造成粗化动力学的原因。我们的仿真还显示了特征阶参数的演变中的三种状态。
更新日期:2017-12-11
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