Hydrodynamic cavitation for scalable exfoliation of few-layered graphene nanosheets

A scalable manufacturing method for the production of biocompatible fewlayered graphene nanosheets is developed using hydrodynamic cavitation. Scalable exfoliation is induced by employing hydrodynamic cavitation and a serum albumin protein. Unlike acoustic cavitation, the primary means of bubble collapse in hydrodynamic cavitation is caused laterally, thereby separating two adjacent flakes through a shear effect. In this process, bovine serum albumin, a known protein, was employed to act as an effective exfoliation agent and provide desired stability by preventing restacking of the graphene layers. This method was used to study the effect of time of graphene exfoliation in a novel hydrodynamic cavitation system. The fabricated products were characterized using Raman spectroscopy, Transmission electron microscopy, Fourier transform infrared spectroscopy and differential scanning calorimetry. The results showed that with increasing the time of exfoliation, the number of graphene layers decreased based on the I (2D)/I (G) ratio but disorder increased based on the I (D)/I (G) ratio. At 3 h, the I (2D)/I (G) ratio was at 0.39 and the I (D)/I (G) ratio was 0.25, while at 6 h the I (2D)/I (G) ratio was 0.35 and I (D)/I (G) ratio was 0.29. The results of the theoretical and computational analysis this research outlines are needed to obtain an effective cavitation model that can be used to potentially improve graphene synthesis and quality. The captured images of bubble propagation in the solution imply that this fluidic phenomenon could assist the graphene exfoliation. To prove this, a simple cavitation model using a needle valve was designed. The needle valve cavitation setup was able to identify that cavitation assists in graphene exfoliation and this was proved using the graphene characterization data. Based on these findings, the simulation models were designed in ANSYS and COMSOL. Specifically, through the ANSYS simulation, we were able to calculate cavitation numbers for specific flow rates and fluid temperatures.