Fractal approaches to characterize the structure of capillary suspensions using rheology and confocal microscopy.
Fractal approaches to characterize the structure of capillary suspensions using rheology and confocal microscopy.
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DOI：
10.1122/1.4997889
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发表时间：
2018-01
影响因子：
3.3
通讯作者：
Koos E
中科院分区：
文献类型：
--
作者：
Bossler F;Maurath J;Dyhr K;Willenbacher N;Koos E
通过添加少量与本体相不混溶的辅助流体，可以显着改变颗粒悬浮液的流变特性。这些毛细管悬浮液强度的急剧变化是由于添加液体引起的毛细管力而产生的，导致渗透颗粒网络。使用流变尺度模型，从屈服应力和作为固体体积分数函数的振荡应变振幅扫描数据推导出分形维数。使用基于氧化铝的毛细管悬浮液和优先润湿的二次流体获得的指数表明，颗粒凝胶的分形维数随着颗粒尺寸的增加而增加。这可以通过与其他力相比毛细管力相应相对减小来解释。使用玻璃模型系统的共焦图像显示微观结构由通过稀疏主干互连的致密颗粒絮凝物组成。因此，使用流变模型可以区分两种不同的分形维数——较低的网络主干维数（D = 1.86–2.05）和絮凝内维数（D = 2.57–2.74）。后者较高，因为与稀疏主干相比，絮凝体内部的局部固体体积分数较高。将这两个尺寸与通过分析 3D 共焦显微镜图像的空间颗粒位置获得的值进行比较，其中计算出的尺寸在 2.43 和 2.63 之间，位于从流变学获得的两个尺寸范围之间。通过该方法确定的分形维数证实了结构致密性随着颗粒尺寸的增加而增加。
The rheological properties of a particle suspension can be substantially altered by adding a small amount of a secondary fluid that is immiscible with the bulk phase. The drastic change in the strength of these capillary suspensions arises due to the capillary forces, induced by the added liquid, leading to a percolating particle network. Using rheological scaling models, fractal dimensions are deduced from the yield stress and from oscillatory strain amplitude sweep data as function of the solid volume fraction. Exponents obtained using aluminum-oxide-based capillary suspensions, with a preferentially wetting secondary fluid, indicate an increase in the particle gel’s fractal dimension with increasing particle size. This may be explained by a corresponding relative reduction in the capillary force compared to other forces. Confocal images using a glass model system show the microstructure to consist of compact particle flocs interconnected by a sparse backbone. Thus, using the rheological models two different fractal dimensionalities are distinguished – a lower network backbone dimension (D = 1.86–2.05) and an intrafloc dimension (D = 2.57–2.74). The latter is higher due to the higher local solid volume fraction inside of the flocs compared to the sparse backbone. Both of these dimensions are compared with values obtained by analysis of spatial particle positions from 3D confocal microscopy images, where dimensions between 2.43 and 2.63 are computed, lying between the two dimension ranges obtained from rheology. The fractal dimensions determined via this method corroborate the increase in structural compactness with increasing particle size.
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DOI：
10.1016/j.colsurfa.2017.01.026
发表时间：
2017-04-05
期刊：
Colloids and surfaces. A, Physicochemical and engineering aspects
影响因子：
--
作者：
Bossler F;Weyrauch L;Schmidt R;Koos E
通讯作者：
Koos E
DOI：
10.1039/f19898503359
发表时间：
1989-10-01
期刊：
JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS I
影响因子：
--
作者：
BREMER, LGB;VANVLIET, T;WALSTRA, P
通讯作者：
WALSTRA, P
影响因子：
3.3
作者：
Fuji, M;Fujimori, H;Chikazawa, M
通讯作者：
Chikazawa, M
影响因子：
1.9
作者：
Dinsmore, AD;Weeks, ER;Weitz, DA
通讯作者：
Weitz, DA
影响因子：
9.2
作者：
Bitsch, Boris;Dittmann, Jens;Willenbacher, Norbert
通讯作者：
Willenbacher, Norbert