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Chemical Kinetics

Chemical kinetics is the study of how and why chemical reactions occur at different rates, exploring the factors that influence the speed of reactions and reaction pathways that occur. Within solid-state reactions, there is added complexity in systems. Notably, each reaction is affected by both diffusion and reaction considerations. What this means, in practice, is that the effective reactions kinetics of an A+B -> C reaction can be controlled by the microstructure:

Where R denotes reaction and D diffusion. From this, it is possible to see how Eef can be a function of the surface area, even if it is assumed that only the pre-exponential factor can change, and diffusion and reaction activation energies remain constant. This gives us a large degree of control over how reactions occur. In order to better understand these systems though, it is vital to quantitatively understand what the microstructure of reactants actually is. 

By characterizing this, it then becomes possible to model the reaction, and control exactly how the kinetics proceed. By doing this with more complex systems, it then becomes possible to rationally choose reaction pathways in a way that cannot be done with other means. These types of projects require interest in thermodynamics and kinetics, along with a mathematical background. These kinds of studies can be applied to quasi-equilibrium (typical solid-state reactions) or highly nonequilibrium reactions.

Example projects:

  1. In ternary systems, there is a global thermodynamic minimum at a given temperature. However, reactions can proceed through metastable phases in quasi-equilibrium systems. By controlling the reaction kinetics, is it possible to instead target these phases?
  2. How much control over the final phase formation do we have? If you consider a diffusion experiment, there will be a host of different phases as you go from one extreme to the other. Can we bypass these intermediate phases entirely kinetically? In systems that are deeply thermodynamically favorable, such as typical cubic carbides, will we get stuck in these systems or can we modify the kinetics enough that we can transit beyond these systems?
  3. Within solid-state reactions, we assume that there is little pressure dependence. However, if we have high-rate nonequilibrium reactions there can be plastic flow conditions (in shockwaves for example). Within quasi-static high-pressure systems, can we target phases that have only been observed in shockwave conditions?