Neville Frances, Moreno-Atanasio Roberto
School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW, Australia.
School of Engineering, University of Newcastle, Callaghan, NSW, Australia.
Front Chem. 2018 Jun 5;6:201. doi: 10.3389/fchem.2018.00201. eCollection 2018.
We present a Discrete Element study of the behavior of magnetic core-shell particles in which the properties of the core and the shell are explicitly defined. Particle cores were considered to be made of pure iron and thus possessed ferromagnetic properties, while particle shells were considered to be made of silica. Core sizes ranged between 0.5 and 4.0 μm with the actual particle size of the core-shell particles in the range between 0.6 and 21 μm. The magnetic cores were considered to have a magnetization of one tenth of the saturation magnetization of iron. This study aimed to understand how the thickness of the shell hinders the formation of particle chains. Chain formation was studied with different shell thicknesses and particle sizes in the presence and absence of an electrical double layer force in order to investigate the effect of surface charge density on the magnetic core-shell particle interactions. For core sizes of 0.5 and 4.0 μm the relative shell thicknesses needed to hinder the aggregation process were approximately 0.4 and 0.6 respectively, indicating that larger core sizes are detrimental to be used in applications in which no flocculation is needed. In addition, the presence of an electrical double layer, for values of surface charge density of less than 20 mC/m, could stop the contact between particles without hindering their vertical alignment. Only when the shell thickness was considerably larger, was the electrical double layer able to contribute to the full disruption of the magnetic flocculation process.
我们展示了一项关于磁性核壳颗粒行为的离散元研究，其中明确界定了核与壳的属性。颗粒核被认为由纯铁制成，因此具有铁磁特性，而颗粒壳被认为由二氧化硅制成。核尺寸在0.5至4.0μm之间，核壳颗粒的实际粒径在0.6至21μm范围内。磁性核的磁化强度被认为是铁饱和磁化强度的十分之一。本研究旨在了解壳的厚度如何阻碍颗粒链的形成。在存在和不存在电双层力的情况下，研究了不同壳厚度和粒径下的链形成，以研究表面电荷密度对磁性核壳颗粒相互作用的影响。对于0.5和4.0μm的核尺寸，阻碍聚集过程所需的相对壳厚度分别约为0.4和0.6，这表明较大的核尺寸不利于用于不需要絮凝的应用中。此外，对于表面电荷密度小于20mC/m的值，电双层的存在可以阻止颗粒之间的接触，而不会阻碍它们的垂直排列。只有当壳厚度相当大时，电双层才能导致磁性絮凝过程的完全破坏。
