Avdeev M V, Aksenov V L, Balasoiu M, Garamus V M, Schreyer A, Török Gy, Rosta L, Bica D, Vékás L
Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna, Russia.
J Colloid Interface Sci. 2006 Mar 1;295(1):100-7. doi: 10.1016/j.jcis.2005.07.048. Epub 2005 Aug 15.
Results of experiments on small-angle neutron scattering from ferrofluids on polar carriers (pentanol, water, methyl-ethyl-ketone), with double-layer sterical stabilization of magnetic nanoparticles, are reported. Several types of spatial structural organization are observed. The structure of highly stable pentanol-based samples is similar to that of stable ferrofluids based on organic non-polar carriers (e.g., benzene) with mono-layer covered magnetic nanoparticles. At the same time, the effect of the interparticle interaction on the scattering is stronger in polar ferrofluids because of the structural difference in the surfactant shell. The structure of the studied methyl-ethyl-ketone- and water-based ferrofluids essentially different from the previous case. The formation of large (>100 nm in size) elongated or fractal aggregates, respectively, is detected even in the absence of external magnetic field, which corresponds to weaker stability of these types of ferrofluids. The structure of the fractal aggregates in water-based ferrofluids does not depend on the particle concentration, but it is sensitive to temperature. A temperature increase results in a decrease in their fractal dimension reflecting destruction of the aggregates. In addition, in water-based ferrofluids these aggregates consist of small (radius approximately 10 nm) and temperature-stable primary aggregates.
报道了在具有磁性纳米颗粒双层空间稳定作用的极性载体（戊醇、水、甲基乙基酮）上对铁磁流体进行小角中子散射的实验结果。观察到了几种类型的空间结构组织。基于戊醇的高度稳定样品的结构类似于基于有机非极性载体（如苯）且磁性纳米颗粒覆盖有单层的稳定铁磁流体的结构。同时，由于表面活性剂壳层的结构差异，极性铁磁流体中粒子间相互作用对散射的影响更强。所研究的基于甲基乙基酮和水的铁磁流体的结构与前一种情况有本质不同。即使在没有外部磁场的情况下，也分别检测到形成了大尺寸（大于100纳米）的细长或分形聚集体，这对应于这些类型铁磁流体较弱的稳定性。水基铁磁流体中分形聚集体的结构不依赖于颗粒浓度，但对温度敏感。温度升高会导致其分形维数降低，反映出聚集体的破坏。此外，在水基铁磁流体中，这些聚集体由小尺寸（半径约10纳米）且温度稳定的初级聚集体组成。
