Thesis Defense: Allison Yau, Kanan Group

Date
Thu April 12th 2018, 9:30 - 10:30am
Location
Chemistry Gazebo

 Thesis Defense: Allison Yau, Kanan Group

*Refreshments at 9:15am

"3D Imaging of Defect Dynamics in Individual Nanoparticles and Grains in Thin Films (A Bragg Coherent Diffractive Imaging Study)"

Elucidating the effects of defects like grain boundaries and dislocations on the properties of polycrystalline materials is a topic of both scientific and technological importance, relevant to designing strain-tolerant materials, controlling ion intercalation, and designing new catalysts. However, complete understanding at the atomic level of how these defects influence material properties requires the ability to image them during dynamic processes. Bragg coherent diffractive imaging (BCDI) is promising in this regard as it uses x-rays to nondestructively obtain 3D images of the strain and defect network within individual nanocrystals in-situ.

 

The first part of this talk gives an overview of how the BCDI technique works and the process by which we collect and analyze our data. In the second part of the talk I will discuss the extension of the BCDI technique for use in tracking the defect dynamics of grains in polycrystalline thin films. BCDI has previously only been used to track the dynamics of nanoparticle systems. The study I will talk about specifically focuses on the ability of the technique to track grain boundary and dislocation dynamics in individual grains in a polycrystalline gold thin film subjected to heating. The final part of the talk will focus on the palladium hydride phase transformation in both palladium thin films and palladium nanoparticles. I will discuss the mobility of grain boundaries at low concentrations of hydrogen in the case of palladium thin films and the nucleation and self-healing of dislocations in the case of palladium nanoparticles.