This work investigates the rheology of graphene oxide (GO) suspension on a yield stress model fluid. The effects caused by the variation of the GO concentration in the suspension and by the amount of oxygenated groups pendant present on the nanosheets surface, on the rheology of the suspensions were evaluated. The dispersant used was an aqueous solution of Carbopol® Ultrez 10. This is a transparent, nontoxic elastic yield stress fluid. GO nanosheets were produced from synthesis of graphite oxide (GrO) by modified Hummers method, and the nanosheets were characterized by XRD, Raman, FTIR, TEM and AFM techniques. The rheological behavior of these suspensions was characterized by oscillatory and steady-state flow experiments. The GO structure characterization shows that oxygenated functional groups were incorporated in its graphite surface in different levels after using two distinct times of oxidation. GO oxidized for 96 h (GO 96 h) showed greater interplanar distance and also presented few layers when compared with GO oxidized for 2 h (GO 2 h). The GO exfoliation process directly into the aqueous dispersion of Carbopol® showed to be an effective method. As for the pure Carbopol solutions, the GO suspensions were well modeled by the Hershel-Bulkley equation. The increase of GO concentration in the suspensions impairs the level of fluid structure and leads to a decrease in viscosity, yield stress, and elasticity. When compared, the GO 96 h promoted a lower decrease in viscosity, yield stress and elasticity than the GO 2 h suspension. For the suspension with a higher concentration of GO 96 h, it was observed the appearance of hysteresis at low shear rates. These results show that small changes in the GO nanosheets surface can significantly influence the rheological responses of a non-Newtonian fluid.

这项工作研究了屈服应力模型流体上氧化石墨烯（GO）悬浮液的流变学。评估了悬浮液中GO浓度的变化和纳米片表面上存在的侧基氧化基团的数量对悬浮液流变性的影响。所使用的分散剂是Ultrez 10的水溶液。这是一种透明，无毒的弹性屈服应力流体。用改良的Hummers法由氧化石墨（GrO）合成制备GO纳米片，并通过XRD，拉曼，FTIR，TEM和AFM技术对其进行表征。这些悬浮液的流变行为通过振荡和稳态流动实验来表征。GO结构表征表明，在使用两次不同的氧化时间后，氧化官能团以不同的水平并入其石墨表面。与GO氧化2 h（GO 2 h）相比，GO氧化96 h（GO 96 h）表现出更大的晶面间距，并且出现的层很少。将GO剥落工艺直接添加到Carbopol®的水分散体中是一种有效的方法。至于纯Carbopol溶液，GO悬浮液通过Hershel-Bulkley方程进行了很好的建模。悬浮液中GO浓度的增加会损害流体结构的水平，并导致粘度，屈服应力和弹性降低。与之相比，GO 96 h的粘度，屈服应力和弹性降低的幅度低于GO 2 h悬浮液。对于GO 96 h浓度较高的悬浮液，观察到在低剪切速率下出现滞后现象。这些结果表明，GO纳米片表面的微小变化会显着影响非牛顿流体的流变响应。