Paper Number
PO121
Session
Poster Session
Title
Yielding behavior of graphene oxide colloids in oscillatory shear
Presentation Date and Time
October 12, 2022 (Wednesday) 6:30
Track / Room
Poster Session / Riverwalk A
Authors
- Shim, Yul Hui (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)
- Rogers, Simon A. (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)
Author and Affiliation Lines
Yul Hui Shim and Simon A. Rogers
Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801
Speaker / Presenter
Shim, Yul Hui
Keywords
experimental methods; colloids
Text of Abstract
Graphene oxide (GO) has been widely exploited in material science and engineering due to its ability to form a liquid crystal phase and large-area alignments. Graphene oxide colloids can be applied to direct ink writing (DIW) printing to realize the fabrication of 3D structure, suggesting potential applications in various fields such as robotics, batteries, sensors, and fillers. In DIW printing with yield stress fluids, the key properties are the rheological transition called yielding, where the material changes from acting as a solid to acting as fluid, during the printing process. This transition is typically thought of as depending on the applied shear force and allows the material to be extruded as a fluid. To characterize the transition between solid-like and fluid-like responses, oscillatory shear rheology has commonly been used, obtaining storage and loss moduli which are traditionally related to the solid-like and fluid-like behavior, respectively. However, the traditional experiment obtains one storage modulus (G’) and only one loss modulus (G’’) and thus, provides partial information about the rheological transitions. This study decomposes the G’’ into two part using recovery rheology, which decomposes the strain into two parts in terms of recoverable and unrecoverable responses. We compare the yielding of a GO suspension and gel, considering that two samples show different trends in their loss modulus. Using the recoverable G’’ and the unrecoverable G’’, we interpret that the GO suspension and GO gel have yielding behavior due to particle rearrangement and breakdown into small structures, respectively. The difference in yielding behavior between the GO suspension and GO gel is indistinguishable by the traditional method. Thus, we show that we can move away from understanding yielding behavior in part due to the G’’, often composed of mixed contributions, to a clearer and deeper understanding of decomposed contributions by including the extra information provided by recovery rheology.