This research will deliver a theoretical framework and computational models, paired with relevant experimental validation, to understand the fundamental mechanisms driving plasma-metal interactions operated in non-equilibrium regimes at atmospheric pressure. This understanding will inevitably lead to technological opportunities for advanced manufacturing and to strategies for the establishment of a circular economy for metal resources.

In non-equilibrium plasma processes, the energy required for the material/phase transformation is not supplied indiscriminately to the whole system but to specific species, with some species conveying most of the energy and other that are thermodynamically unaffected but subjected to localized transformations i.e. ‘non-equilibrium’. Based on this principle, low-pressure plasma technology has enabled the microelectronic industry and electronic products, from mobile phones to data centres, which have become essential in our societal, economic and technological progress in finance, healthcare, energy, artificial intelligence etc. The study of non-equilibrium plasmas has further evolved in multiple directions, including that of the fast-growing field of non-equilibrium atmospheric pressure plasmas (NAPPs).

The understanding of NAPP-metal interactions is therefore a fundamental step to deliver highly innovative manufacturing and sustainable technologies. However much of the theory and understanding developed for instance for low-pressure plasmas is not applicable when NAPP regimes take over and where fundamental mechanisms, that were considered negligible, become important. Some modelling and simulation work has been carried out to differentiate low-pressure from higher pressure regimes, however these are still far too limited to understand and satisfactorily describe metal-plasma interactions at atmospheric pressure.

The proposed work will develop theoretical models, that describe important relevant mechanisms, to understand metal interactions with atmospheric pressure plasmas, representing innovative manufacturing as relevant to a range of industrial sectors including aerospace/automotive, energy and environmental sectors. A theoretical framework for describing energy and mass transfer of metal-plasma systems will be developed. It will rely on existing theory applicable to low-pressure processes where new important mechanisms relevant to NAPPs are introduced. The implications of these changes are substantial both in terms of the outcomes, as experiments confirm, as well as in terms of the simulation implementation.

Part of the research program can also involve validation through a set of experiments designed to probe metal transformation under different conditions. These will involve NAPP interactions with metal surfaces as well as metal nanoparticles aerosolised within a plasma environment. Plasma diagnostics and materials characterization can be used to describe relevant plasma parameters and solid transformations.
The overall aim of the project is to produce theoretical models that describe metal interactions with atmospheric pressure plasmas that are currently unavailable and that can form the basis for a validated NAPP theoretical framework. The specific objectives are the following:

• produce a theoretical model describing metal interactions with atmospheric pressure plasmas applicable to both
  
  • planar geometries as well as
  • distributed systems (i.e. floating particles within a gas-phase plasma)
• carry out relevant simulations and validate against selected existing literature and against a set of experiments that can be carried out in the lab