Rheological behavior of dilute imogolite suspensions
Rheological behavior of dilute imogolite suspensions
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稀伊毛缟石悬浮液的流变行为
DOI：
10.1016/j.colsurfa.2012.12.041
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Yasuhisa Adachi
中科院分区：
文献类型：
--
作者：
Yoko Tstujimoto;Asuka Yoshida;Motoyoshi Kobayashi;Yasuhisa Adachi
伊毛戈兰是火山灰土中最重要的粘土矿物之一。伊毛戈兰的形态是非常独特的，包括内径和外径分别约为1和2 nm的细纤维管。伊毛沸石的化学结构特征为沿管内壁沿着的SiOH基团和在管外表面上的AlOH基团。作为这种形态和化学结构的结果，在高pH值下，伊毛戈兰凝聚。在本研究中，我们专注于稀释的伊毛戈兰悬浮液在分散和凝聚状态下的非牛顿行为的详细差异。使用同心圆柱形粘度计进行粘度作为体积分数的函数的实验。施加的剪切速率从6.45增加到258 s-1，然后降低到初始值;该过程重复三次。分散的伊毛戈兰悬浮液的流动曲线显示出轻微的滞后。此外，剪切稀化，这是随着剪切速率的增加而降低的粘度，出现;这被认为是由于伊毛戈兰颗粒的取向分布的变化。对于凝结的悬浮液，滞后回线的面积随着体积分数的增加而增加。随着剪切次数的增加，流变曲线有上移的趋势，并趋于稳定。此外，在高pH值下的剪切稀化比在低pH值下的剪切稀化更显著。从流动曲线的截距确定凝固状态的屈服应力。我们建议，在高pH值的伊毛戈兰形成絮体，反复进行破碎和重新凝聚由给定的剪切应力，因此，形成更强的结构。
Imogolite is one of the most important clay minerals contained in volcanic ash soil. The morphology of imogolite is very unique and comprises thin fibrous tubes with inside and outside diameters of approximately 1 and 2 nm, respectively. The chemical structure of imogolite features SiOH groups along the inner walls of the tubes and AlOH groups on the outer surfaces of the tubes. As a result of this morphology and the chemical structure, imogolite coagulates at high pH. In the present study, we focus on the detailed differences of the non-Newtonian behavior of the dilute imogolite suspension in the dispersed and coagulated states. Experiments on the viscosity as a function of volume fraction were performed using a concentric cylindrical viscometer. The applied shear rate was increased from 6.45 to 258 s−1and then decreased to the initial value; this procedure was repeated three times. The flow curves for the dispersed imogolite suspensions showed slight hysteresis. Additionally, shear thinning, which is a decrease of the viscosity with increasing shear rate, emerged; this is thought to be due to the change of the orientation distribution of the imogolite particles. For the coagulated suspensions, the area of the hysteresis loop increased with increasing volume fraction. The flow curves tended to shift upwards and became constant as the shearing cycles increased. Moreover, shear thinning at high pH was more significant than that at low pH. The yield stress of the coagulated state was determined from the intercept of the flow curve. We propose that imogolite at high pH forms flocs that are repeatedly subjected to breakup and re-coagulation by the given shear stress; thus, a stronger structure is formed.