Origin of Batch Hydrothermal Fluid Behavior and Its Influence on Nanomaterial Synthesis

Summary Batch hydrothermal reactor is known as a closed system, and what happens in this “black box” is mysterious. Now, by using the tendency of graphene oxide (GO) to align along the flow and the fixation effect of thermoset resin, the hydrothermal annular convection can be inferred from the axisymmetric poloidal structure and GO-assembled annular distribution. Temperature difference and geometric symmetricity of the reactor account for the annular convection, which is also found to be affected by solution viscosity and reactor parameters. Numerical simulations reproduce the annular convection and are used to investigate the parameter space beyond experiments. Plume flows occur at the bottom of the reactor due to flow instability. Irregular and intensive flow is against the synthesis of high-aspect-ratio nanomaterials and monolithic gels. It is noteworthy that large-scale batch hydrothermal synthesis may not be feasible for some nanowires, nanosheets, and particularly gels due to the non-negligible flow influence.