Nanoparticle behaviour

Some materials behave very differently when they are made very small, compared to 'normal size'. At the scale of nanometers (1/1 000 000 000), interfaces between phases have a much larger effect the material behaviour. Simulations and advanced experiments can help explain and predict these effects which are often a combination of chemistry, elasticity and interfacial effects.

LiFePO4 is a much better electrode material when nano-sized

This work deals with a potential electrode materials which shows remarkable performance improvement as nanoparticles compared to large samples. The model shows anisotropic composition dependent elasticity, facet-dependent surface wetting, and suppression of the phase decomposition depending on particle size .

The image here shows the microstructure of the two phases with increasing size (down) and lithiation (right).

Miscibility Gap Closure, Interface Morphology, and Phase Microstructure of 3D LixFePO4 Nanoparticles from Surface Wetting and Coherency Strain, ACS Nano, 2015, 9 (10), pp 9757–9771

Watching Palladium nanocubes transform into palladium hydride

An important aspect of using Hydrogen industrially and as a fuel is the ability to store and purify it. Palladium reacts with hydrogen but needs a push to get it to react, since forming palladium hydride requires a new interface and associated strain effects. In this work we combine simulation with experiments on single nanoparticles to show the strain effects, defects at the interface and how they might be avoided.

This image shows the observed and simulated strains for increasing hydration (down). Interestingly, the cube originally wants to become more star-shape, and later switches to become more spherical.

Avalanching strain dynamics during the hydriding phase transformation in individual palladium nanoparticles, Nature Communications 6 (2015) 10092

Three-dimensional imaging of dislocation dynamics during the hydriding phase transformation, Nature Materials 16 (2017) 565–571

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