The University of Southampton
Engineering and the Environment

Research project: Modelling and analysis of solid state reaction kinetics

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At Southampton, Professor Marco J Starink has developed a range of analysis methods for thermally activated reactions. They include a widely used method for activation energy determination and models for diffusion controlled-reactions.

Project Overview

Thermally activated reactions and particularly diffusion-controlled reactions are important as they determine the main mechanical and functional properties of a diverse range of materials, components and devises. These include components as diverse as welds of medium to high strength alloys, turbine engine components, bio-cements, flat-panel displays and X-ray imaging systems. The work by Prof Marco Starink in this field has stretched over 2 decades. It includes the derivation of models and analysis methods that have found a wide application in engineering and science.

The method for derivation of activation energy from experiments at constant heating rate known as the Starink or Type B-1.92 method is the most accurate method that can be performed through a single graphical representation. The key equation relates the heating rate, β, the characteristic temperature, Τ, and the activation energy, Ε, through:

Formula

The method is recognized by the ICTAC kinetics committee as the most accurate in its group, and is widely used to analyse reactions as diverse as curing of thermosets, epoxies and resins, pyrolysis of biomass and coal, ketonization reactions for biorenewable fuels, crystallization, and a range of important exothermic reactions in light alloys, aerospace materials, explosives, quantum dots, minerals, chemical looping air separation.

Recent work on reactions kinetics produced a new model for diffusion controlled reactions. The model incorporates elements of the extended volume concept and combines this with a new treatment of soft impingement of diffusion fields. The model has been compared to a range of new and old data on diffusion-controlled reactions including precipitation reactions and exsolution reactions, showing a very good performance, outperforming classical and recent models. The model allows new interpretation of existing data which, for the first time, show a consistent analysis, in which reaction exponents are always consistent with transformation theory.

The models have been incorporated as part of integrated models for welds and quench sensitivity of alloys. Various applications of the models are investigated with international collaborators in France, Germany, Spain and the USA.

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Schematic illustration

Schematic illustration of the model showing impingement for 2 dimensional growth of a fixed number of nuclei. There are 4 nuclei in this section (yellow) with a partially depleted matrix around them. Each grey scale represents an interval of the depletion fraction. More details here.

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