Comparison of reversible and irreversible dipolar assemblies in a ferrofluid
Comparison of reversible and irreversible dipolar assemblies in a ferrofluid
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DOI：
10.1016/j.jmmm.2006.02.251
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发表时间：
2006-11-01
影响因子：
2.7
通讯作者：
Erne, B. H.
中科院分区：
文献类型：
--
作者：
Klokkenburg, M.;Erne, B. H.
磁性纳米粒子在磁流体中的零场聚集既可以是不可逆的，也可以是动态平衡的结果；这两种情况可以通过复磁化率的测量和低温透射电子显微镜(Cryo-TEM)来区分。我们通过比较两个在零场中显示偶极结构形成的胶体系统来证明这一点。磁性铁纳米粒子的分散性逐渐被氧化以降低磁矩，尽管偶极引力消失，但热运动并不会将偶极结构分解为单一粒子。相反，偶极结构在氧化过程中变得化学固定，这是一个不可逆聚集的例子。相反，在化学稳定的磁铁矿分散体中，零场偶极结构被发现在稀释后解体，表明这种结构是可逆的，是动态平衡的结果。(C)2006爱思唯尔B.V.保留所有权利。
Zero-field aggregation of magnetic nanoparticles in a ferrofluid can either be irreversible or result from a dynamic equilibrium; the two cases can be distinguished by measurements of the complex magnetic susceptibility and by cryogenic transmission electron microscopy (cryo-TEM). We demonstrate this by comparing two colloidal systems that show dipolar structure formation in zero field. A dispersion of magnetic iron nanoparticles is gradually oxidized to decrease the magnetic moments, and despite the vanishing dipolar attractions, thermal motion does not break up the dipolar structures into single particles. Instead, the dipolar structures become chemically fixed during the oxidation process, an example of irreversible aggregation. In contrast, the zero-field dipolar structures in a chemically stable magnetite dispersion are found to disintegrate upon dilution, indicating that the structures are reversible and result from a dynamic equilibrium. (C) 2006 Elsevier B.V. All rights reserved.