Probing Anisotropic Surface Properties and Interaction Forces of Chrysotile Rods by Atomic Force Microscopy and Rheology
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- 作者：Dingzheng Yang ; Lei Xie ; Erin Bobicki ; Zhenghe Xu ; Qingxia Liu ; Hongbo Zeng
- 刊名：Langmuir
- 出版年：2014
- 出版时间：September 16, 2014
- 年：2014
- 卷：30
- 期：36
- 页码：10809-10817
- 全文大小：485K
- ISSN：1520-5827
文摘
Understanding the surface properties and interactions of nonspherical particles is of both fundamental and practical importance in the rheology of complex fluids in various engineering applications. In this work, natural chrysotile, a phyllosilicate composed of 1:1 stacked silica and brucite layers which coil into cylindrical structure, was chosen as a model rod-shaped particle. The interactions of chrysotile brucite-like basal or bilayered edge planes and a silicon nitride tip were measured using an atomic force microscope (AFM). The force鈥揹istance profiles were fitted using the classical Derjaguin鈥揕andau鈥揤erwey鈥揙verbeek (DLVO) theory, which demonstrates anisotropic and pH-dependent surface charge properties of brucite-like basal plane and bilayered edge surface. The points of zero charge (PZC) of the basal and edge planes were estimated to be around pH 10鈥?1 and 6鈥?, respectively. Rheology measurements of 7 vol % chrysotile (with an aspect ratio of 14.5) in 10 mM NaCl solution showed pH-dependent yield stress with a local maximum around pH 7鈥?, which falls between the two PZC values of the edge and basal planes of the rod particles. On the basis of the surface potentials of the edge and basal planes obtained from AFM measurements, theoretical analysis of the surface interactions of edge鈥揺dge, basal鈥揺dge, and basal鈥揵asal planes of the chrysotile rods suggests the yield stress maximum observed could be mainly attributed to the basal鈥揺dge attractions. Our results indicate that the anisotropic surface properties (e.g., charges) of chrysotile rods play an important role in the particle鈥損article interaction and rheological behavior, which also provides insight into the basic understanding of the colloidal interactions and rheology of nonspherical particles.