Zhiqiang Luo, Hongzan Song, Xiaorui Feng, Mingtao Run, Huanhuan Cui, Licun Wu, Jungang Gao, and Zhigang Wang
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摘要: 利用偏光显微镜（POM）, 宏观观察，流变仪，小角X-射线散射，扫描电镜以及透射电镜观察了埃洛石纳米管水分散体系的液晶相行为和溶液-凝胶相转变。 通过POM和宏观观察发现在1%HNT浓度时液晶相开始形成，到25%HNT浓度时全部液晶相形成。流变学测试说明当HNT浓度高于20%时，该分散体系呈现典型的剪切流动行为，并进一步证明溶液-凝胶相转变发生在HNT浓度为37%时。而且，当盐酸（HCl）加入到HNT水分散体系中，会发生pH诱导的凝胶化现象并伴随着更强的双折射。上述发现可望阐明各种拓扑结构的HNT体系的相行为，从而为制备长程有序纳米物质奠定基础。
Abstract: The liquid crystalline phase behavior and sol–gel transition in halloysite nanotubes (HNTs) aqueous dispersions have been investigated by applying polarized optical microscopy (POM), macroscopic observation, rheometer, small-angle X-ray scattering, scanning electron microscopy, and transmission electron microscopy. The liquid crystalline phase starts to form at the HNT concentration of 1 wt %, and a full liquid crystalline phase forms at the HNT concentration of 25 wt % as observed by POM and macroscopic observation. Rheological measurements indicate a typical shear flow behavior for the HNT aqueous dispersions with concentrations above 20 wt % and further confirm that the sol–gel transition occurs at the HNT concentration of 37 wt %. Furthermore, the HNT aqueous dispersions exhibit pH-induced gelation with more intense birefringence when hydrochloric acid (HCl) is added. The above findings shed light on the phase behaviors of diversely topological HNTs and lay the foundation for fabrication of the long-range ordered nano-objects.