NiAl-Cr microstructure formation

A paper based on my thesis work was recently accepted to the journal Physical Chemistry Chemical Physics. I helped researchers at the IMDEA Materials Institute in Madrid, Spain apply the phase-field model from my thesis to the NiAl-Cr ternary eutectic superalloy. They connected my model to a database of thermodynamic properties and were able to simulate the growth of the complicated microstructure in this system. Superalloys are a special class of metals that are used to make jet turbine blades because they are very strong and resistant to deformation at high temperatures.

Read Formation mechanism of eutectic microstructures in NiAl-Cr composites

Quantitative phase-field modeling of dendritic electrodeposition

I recently had a Rapid Communication accepted at Physical Review E. This paper represents several years of effort while I was at Samsung to develop a model of the growth of metal dendrites during electrodeposition. In addition to looking pretty, understanding how these dendrites grow is important for making rechargeable batteries with significantly higher energy density than current technologies. The dendrites eventually cause a short-circuit during cycling when a metal electrode is used. In this paper I constructed a phase-field model that accurately captures many of the observed features of electrodeposits. This will be a valuable tool for mitigating dendrite growth, particularly for pulsed charging. The model provides an estimate of the time at which the interface becomes unstable, and could be used to optimize the pulse time while still maintaining a flat interface. The video on the right shows one of the simulations that is presented in the paper. The blue lines are electric field lines, which indicate the direction of migration of ions in the electrolyte (white). The video shows that, after a short period of stable growth, the interface becomes unstable. The electric field concentrates at protruding tips, causing them to grow faster and shield the nearby electrode. When the field at a tip gets too high, the tip splits and the process repeats. Quantitative phase-field modeling of dendritic electrodeposition

Nano Letters paper

This week I had a paper on nucleation phenomena in nanoparticles accepted to the journal Nano Letters. The major conclusions of the work is that nucleation of a second phase is likely to always occur at the surfaces of nanoparticles, and the barrier energy is size dependent as a result of coherency strain, and scales with a particle’s area/volume ratio. The barrier disappears below a critical size. A preprint of the paper is available here. Below is a video of a LiFePO4 nanoparticle being discharged. The lithiated phase forms at the edges of the particle and then moves inward as the particle fills.