Rheology and microstructure of dilute graphene oxide suspension
Graphene and graphene oxide are potential candidates as nanofluids for thermal management applications. Here, we investigate the rheological properties and intrinsic viscosity of aqueous suspension of graphene and use the measured intrinsic viscosity to determine the aspect ratio of graphene oxide. Dilute suspension of graphene oxide (0.05 to 0.5 mg/mL) exhibits a shear thinning behavior at low shear rates followed by a shear-independent region that starts at shear rate between 5 and 100/s depending on the concentration. This shear thinning behavior becomes more pronounced with the increase of particle loading. Moreover, AFM imaging of the dried graphene oxide indicates the evolution of irregular and thin low fractal aggregates of 0.3–1.8 nm thickness at lower concentrations to oblate compact structures of 1–18 nm thickness of nanosheets at higher concentration. These observations elucidate the microstructure growth mechanisms of graphene oxide in multiphase systems, which are important for nanofluids applications and for dispersing graphene and graphene oxide in composite materials. The suspension has a very high intrinsic viscosity of 1661 due to the high graphene oxide aspect ratio. Based on this intrinsic viscosity, we predict graphene oxide aspect ratio of 2445. While the classical Einstein and Batchelor models underestimate the relative viscosity of graphene oxide suspension, Krieger–Dougherty prediction is in a good agreement with the experimental measurement.
KeywordsGraphene oxide Nanofluids Rheology Intrinsic viscosity Suspension Aspect ratio
The authors acknowledge Dr. Tewfik Souier for his assistance with AFM imaging.
- Gupta VK, Suhas (2009) Application of low-cost adsorbents for dye removal—a review. J Environ Manag 90(8):2313–2342. http://www.sciencedirect.com/science/article/pii/S0301479708003290#Google Scholar
- Güven N (1992) Molecular aspects of clay-water interactions. Clay-water interface and its rheological implications 4:2–79Google Scholar
- Iwamoto S, Lee S-H, et al (2013) Relationship between aspect ratio and suspension viscosity of wood cellulose nanofibers. Polym J. doi: 10.1038/pj.2013.64
- Prud’homme RK, Aksay IA, et al (2008) Conductive ink containing thermally exfoliated graphite oxide and method of making a conductive circuit using the same, US patent App. 20,080/302,561Google Scholar