Compressible Flow Exfoliation of Two‐Dimensional Nanomaterials: Insights Into Layer Separation Informed by Gas Dynamics

As the technological implications of 2D nanomaterials like graphene, hexagonal boron nitride (h‐BN), and molybdenum disulfide (MoS ₂ ) continue to expand, a critical need arises for the streamlined production of these materials. Their characteristics such as high mechanical robustness, exceptional electrical and thermal conductivities, and substantial surface area effects underscore this urgency. This study delves into an innovative technique, the compressible flow exfoliation (CFE) method, for the aim of achieving scalable production of 2D h‐BN nanosheets. The CFE technique capitalizes on the properties of high‐pressure gas, laden with 2D nanomaterials, as it traverses an orifice, acting as a converging–divergent (CD) nozzle. In such situations, the supersonic flow results in the formation of shock waves, exerting a sudden drag force on the nanomaterials. However, it is revealed that such shock events alone are not sufficient for separating the 2D layers in nanomaterials. Through detailed particle laden‐flow analysis and experiments, we reveal that the key to initiating exfoliation lies in the presence of a thrust force, which is critical for effectively separating these layers. The ensuing flow structure understanding is validated using a CD nozzle and a shock tube experiment, yielding the insight that a thrust force, originating from acceleration at the nozzle throat, is essential for material exfoliation. The rapid and continuous nature of the CFE process signifies its superiority over conventional 2D material exfoliation methods, attributing to environmentally friendly processing, decreased defect emergence, and adaptability to a wide variety of 2D layered materials utilizing a gaseous medium.