Doctoral dissertation on chemical processes and material modelling

14/12/2016

VTT Senior Scientist Risto Pajarre will defend his dissertation at Aalto University on 15 December 2016. The dissertation focuses on computational chemical thermodynamics, which is applied in a number of areas of chemistry and the related fields. The theory and computational methods developed for the thesis have been widely applied in R&D within the Finnish process industry.

Chemical thermodynamics methods can be used to describe possible processes and end states in chemically reactive systems. Computer programs, based on so-called Gibbs free energy minimisation, have been used for decades to define equilibrium compositions, particularly in sectors involving metallurgy, combustion processes and aqueous solutions. A significant amount of work has been done to make these programs as efficient and reliable as possible, and to measure and evaluate the data they need.

However, an energy minimisation method has not been generally applied to cases where the process should be modelled as reactions occur, or that involve conditions which cannot be directly connected to the material balances, temperature or pressure of the system.   

The dissertation extends the traditional scope of application of equilibrium solvers, by including new energy terms in the solution. Such terms are associated with e.g. surface energy, membrane equilibrium and ion exchange in fibre suspensions, or external electric and magnetic fields. The same technique can be used to model the development of systems over time, while observing the stages reached in internal reactions. Extending the application of equilibrium solvers enables the examination of new kinds of systems, using existing thermodynamic software and, as far as possible, established data. 

The theory and computational methods developed in the dissertation have been widely applied in R&D within the Finnish processing industry, where realistic chemical descriptions have been formed for the pulp and paper industries, as well as reaction kinetics controlled combustion and solution chemistry processes. The general, chemical thermodynamic basis of the model's extension has also enabled a range computational applications for materials technology, such as defining the surface energy of alloys, and evaluating the effect of diffusion speed and particle size during phase changes in metal micro and nano structures. The theory has also been applied in two dissertations published earlier this year.

The dissertation can be found online at: http://www.vtt.fi/inf/pdf/science/2016/S141.pdf

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