I recently had a paper accepted at the Journal of Computational Physics on removing timestep restrictions in the numerical solution of two-phase flow problems in porous media. The paper can be downloaded for free from the journal until August 23rd by following this link. The idea is to add some carefully constructed phase-field terms that guarantee Newton’s method will converge. This changes the physics a little bit, but a solution to the original equations can be found by reducing the magnitude of these terms to zero over a few Newton updates.
Paper published in Science
Last week a paper that I co-authored was published in Science! Here is a link to the paper, Origin and hysteresis of lithium compositional spatiodynamics within battery primary particles, and here are several press releases related to the research:
- A nanoview of battery operation
- Stanford-led team reveals nanoscale secrets of rechargeable batteries
- New X-Ray Microscopy Technique Images Nanoscale Workings of Rechargeable Batteries
Although the major findings in this work were accomplished by experimental collaborators at Stanford and LBNL, the motivation for the experiments came in part from my postdoc work, where we simulated the heterogeneity of lithium in battery nanoparticles and made several controversial predictions. We calculated that the properties of individual nanoparticles should be significantly different from the measured properties of battery electrodes, which are comprised of billions of particles. Thus the challenge was to build a battery out of a single nanoparticle and measure its properties.
It took several years, but this paper conclusively verifies the prediction of a heterogeneous reaction rate in LiFePO4 with a beautiful set of experiments. Our colleagues at Stanford made a rechargeable battery out of a few nanoparticles, and invented a way to image the chemical composition of the particles as they were cycled in a liquid electrolyte (inside a synchrotron). Below is the first ever video of LiFePO4 nanoparticles being charged and discharged.
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