Mathematical Modelling and Design for the Scale-up of an AACVD Process - PhDData

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Mathematical Modelling and Design for the Scale-up of an AACVD Process

The thesis was published by de Oliveira Filho, Pedro Ivo, in June 2022, UCL (University College London).

Abstract:

The manufacturing process of photovoltaic devices, such as solar cells, relies on the production of Transparent and Conductive Oxide (TCO) films. One of the techniques for creating these films is based on Aerosol-Assisted Chemical Vapour Deposition (AACVD). The AACVD process comprises the atomisation of a precursor solution into aerosol droplets, which are transported to a heated chamber for the synthesis of films such as the TCOs, as well as coatings, powders, composites and nanotubes. At present, AACVD has not been used as an industrial deposition technique. However, it has the potential to be scaled-up due to its versatility and the ease through which effective functional coatings can be deposited at a laboratory-scale. Computational simulations are pivotal to study the feasibility of such a scale-up. This thesis presents, therefore, an integrated model to support the AACVD process scale-up. The model is comprised of four stages: aerosol generation, transport, delivery and chemical deposition. The generation of aerosol is described by a distribution of droplet sizes, which is the input to a transport model that incorporates the impact of aerosol losses. The output distribution provides sufficient information to predict the amount and sizing of aerosol reaching the deposition site. Experimental validation has shown the model to be effective at predicting transport losses and droplet sizes. The delivery stage includes the solvent evaporation, accounting for uncertainties in the temperature profile of the deposition site. This is a key factor for the solvent evaporation, setting the precursors free to react and form the desired products. For the chemical deposition stage, reactions in the solid and gas phases were studied. The model presented is suitable for application on the scale of industrial processes and is also suitable for processes that rely on atomisation and transport of particles, for example, spray drying or cooling and fuel combustion. Lessons learned in modelling uncertainties and their impact on process scale-up motivated the research into formulation, modelling and solution methods for such applications. Therefore, as an additional contribution, this thesis introduces Uncertainty.jl, a modelling framework focused on the treatment of uncertainty.



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