We show that a suspension of non-Brownian calcite particles in glycerol-water mixtures can be tuned continuously from being a yield-stress suspension to a shear-thickening suspension—without a measurable yield stress—by the addition of various surfactants. We interpret our results within a recent theoretical framework that models the rheological effects of stress-dependent constraints on inter-particle motion. Bare calcite particle suspensions are found to have finite yield stresses. In these suspensions, frictional contacts that constrain inter-particle sliding form at an infinitesimal applied stress and remain thereafter, while adhesive bonds that constrain inter-particle rotation are broken as the applied stress increases. Adding surfactants reduces the yield stress of such suspensions. We show that, contrary to the case of surfactant added to colloidal suspensions, this effect in non-Brownian suspensions is attributable to the emergence of a finite onset stress for the formation of frictional contacts. Our data suggest that the magnitude of this onset stress is set by the strength of surfactant adsorption to the particle surfaces, which therefore constitutes a new design principle for using surfactants to tune the rheology of formulations consisting of suspensions of adhesive non-Brownian particles. Graphical Abstract Impact of surfactants on the rheology of concentrated calcite suspensions. Black, schematic flow curve for bare particles. Low stress: adhesive contact, rolling and sliding between particles prevented (red). High stress: frictional contact, rolling allowed (green), constraints broken → shear thinning. Blue, with surfactant. Low stress: repulsion prevents contact, rolling and sliding allowed, removing yield stress entirely. High stress: surfactant displaced (see inset), particles bare and sliding prevented; constraints formed → shear thickening Impact of surfactants on the rheology of concentrated calcite suspensions. Black, schematic flow curve for bare particles. Low stress: adhesive contact, rolling and sliding between particles prevented (red). High stress: frictional contact, rolling allowed (green), constraints broken → shear thinning. Blue, with surfactant. Low stress: repulsion prevents contact, rolling and sliding allowed, removing yield stress entirely. High stress: surfactant displaced (see inset), particles bare and sliding prevented; constraints formed → shear thickening

中文翻译：

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通过调整颗粒间摩擦将屈服应力方解石悬浮液变成剪切增稠的悬浮液

我们表明，通过添加各种表面活性剂，非布朗方解石颗粒在甘油-水混合物中的悬浮液可以从屈服应力悬浮液连续调整为剪切增稠悬浮液，没有可测量的屈服应力。我们在最近的理论框架内解释了我们的结果，该框架模拟了应力依赖约束对粒子间运动的流变效应。发现裸方解石颗粒悬浮液具有有限屈服应力。在这些悬浮液中，限制粒子间滑动的摩擦接触在极小的施加应力下形成并在此后保持，而限制粒子间旋转的粘合剂随着施加应力的增加而断裂。添加表面活性剂可降低此类悬浮液的屈服应力。我们表明，与将表面活性剂添加到胶体悬浮液的情况相反，非布朗悬浮液中的这种效果归因于摩擦接触形成的有限起始应力的出现。我们的数据表明，这种起始应力的大小由表面活性剂吸附到颗粒表面的强度决定，因此构成了使用表面活性剂调节由粘性非布朗颗粒悬浮液组成的制剂流变性的新设计原则。图解 表面活性剂对浓缩方解石悬浮液流变学的影响。黑色，裸颗粒的示意流动曲线。低应力：防止颗粒之间的粘附接触、滚动和滑动（红色）。高应力：摩擦接触，允许滚动（绿色），破坏约束 → 剪切变薄。蓝色，含表面活性剂。低应力：排斥防止接触，允许滚动和滑动，完全消除屈服应力。高应力：表面活性剂移位（见插图），颗粒裸露并防止滑动；约束形成 → 剪切增稠 表面活性剂对浓缩方解石悬浮液流变学的影响。黑色，裸颗粒的示意流动曲线。低应力：防止颗粒之间的粘附接触、滚动和滑动（红色）。高应力：摩擦接触，允许滚动（绿色），破坏约束 → 剪切变薄。蓝色，含表面活性剂。低应力：排斥防止接触，允许滚动和滑动，完全消除屈服应力。高应力：表面活性剂移位（见插图），颗粒裸露并防止滑动；约束形成→剪切增稠 完全消除屈服应力。高应力：表面活性剂移位（见插图），颗粒裸露并防止滑动；约束形成 → 剪切增稠 表面活性剂对浓缩方解石悬浮液流变学的影响。黑色，裸颗粒的示意流动曲线。低应力：防止颗粒之间的粘附接触、滚动和滑动（红色）。高应力：摩擦接触，允许滚动（绿色），破坏约束 → 剪切变薄。蓝色，含表面活性剂。低应力：排斥防止接触，允许滚动和滑动，完全消除屈服应力。高应力：表面活性剂移位（见插图），颗粒裸露并防止滑动；约束形成→剪切增稠 完全消除屈服应力。高应力：表面活性剂移位（见插图），颗粒裸露并防止滑动；约束形成 → 剪切增稠 表面活性剂对浓缩方解石悬浮液流变学的影响。黑色，裸颗粒的示意流动曲线。低应力：防止颗粒之间的粘附接触、滚动和滑动（红色）。高应力：摩擦接触，允许滚动（绿色），破坏约束 → 剪切变薄。蓝色，含表面活性剂。低应力：排斥防止接触，允许滚动和滑动，完全消除屈服应力。高应力：表面活性剂移位（见插图），颗粒裸露并防止滑动；约束形成→剪切增稠 约束形成 → 剪切增稠 表面活性剂对浓缩方解石悬浮液流变学的影响。黑色，裸颗粒的示意流动曲线。低应力：防止颗粒之间的粘附接触、滚动和滑动（红色）。高应力：摩擦接触，允许滚动（绿色），破坏约束 → 剪切变薄。蓝色，含表面活性剂。低应力：排斥防止接触，允许滚动和滑动，完全消除屈服应力。高应力：表面活性剂移位（见插图），颗粒裸露并防止滑动；约束形成→剪切增稠 约束形成 → 剪切增稠 表面活性剂对浓缩方解石悬浮液流变学的影响。黑色，裸颗粒的示意流动曲线。低应力：防止颗粒之间的粘附接触、滚动和滑动（红色）。高应力：摩擦接触，允许滚动（绿色），破坏约束 → 剪切变薄。蓝色，含表面活性剂。低应力：排斥防止接触，允许滚动和滑动，完全消除屈服应力。高应力：表面活性剂移位（见插图），颗粒裸露并防止滑动；约束形成→剪切增稠 约束破坏→剪切稀化。蓝色，含表面活性剂。低应力：排斥防止接触，允许滚动和滑动，完全消除屈服应力。高应力：表面活性剂移位（见插图），颗粒裸露并防止滑动；约束形成→剪切增稠 约束破坏→剪切稀化。蓝色，含表面活性剂。低应力：排斥防止接触，允许滚动和滑动，完全消除屈服应力。高应力：表面活性剂移位（见插图），颗粒裸露并防止滑动；约束形成→剪切增稠