Ultrasonic cavitation and streaming are widely used in the chemical, food, oil, drag and paint processing industries. The generation of cavitation bubbles though ultrasound (US) is a powerful technique that induces physico-mechanical and physico-chemical effects in multiphase systems contained in liquid media. When imploding, cavitation bubbles produce high-speed liquid jets (300-1000 m/s) accompanied by high pressure (100-1000 MPa) and local temperature spikes (up to 10000 K). Pulsating bubbles impose high-frequency pressure pulses of several MPa in magnitude. These basic phenomena are involved in specific and in many cases poorly understood mechanisms that are used as a working tool, for instance, for manufacturing two-dimensional (2D) nanomaterials, and exploited for various other applications in industry.
Two-dimensional (2D) nanomaterials, such as graphene, MoS2, WS2, h-BN, h-BCN, and other layered materials are being heralded as unique materials that may help overcome current and future societal challenges related to energy generation, thermal management, and storage and in the healthcare sectors. Despite intense research, the successful exploitation and integration of 2D materials in next generation technologies where faster, thinner, and stronger devices are needed is still hampered by the issues associated with the scalability, reproducibility, and sustainability of current manufacturing techniques, aimed at generating uniform and high-quality 2D materials. For example, most current production processes of 2D materials are limited to batch-processing and require large quantities of harmful solvents and surfactants for the shearing or ultrasonication to work, bearing the risk of causing much harm to the environment, whilst the resulting structures are often limited in size and to few layer 2D materials with monolayers only at the edges of the exfoliated structures.
Here, we propose to overturn the current exfoliation technological paradigm by giving the ultrasound-induced mechanisms the leading role in the exfoliation of layered materials. The scientific novelty lies in establishing the precise mechanisms of ultrasonic exfoliation through advanced and bespoke in situ synchrotron X-ray ultrahigh speed imaging techniques (up to million frames per second), small-angle neutron scattering, precise acoustic measurements, advanced ex situ characterisation, and multi-scale modelling methods. The technological step-change advance lies in developing a scalable and environmentally friendly process with focus on using water as the liquid medium (minimising the amount of special, expensive, and harmful additives), and reducing the processing time from tens of hours to minutes whilst increasing yield and size of the 2D sheets.
The processing part of the project will concentrate on the development of an innovative reactor, controlled ultrasonication, optimisation of processing parameters, and the selection of suitable eco-friendly additives in order to achieve the most efficient exfoliation and dispersion in terms of the lateral size, shape, quality, flake thickness, and yield of the nanosheets. The properties of these 2D functional materials will be tested and benchmarked against commercially available 2D materials and employed in batteries and thermal management applications.
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