Lee Penn works with synthetic and naturally-occurring nanocrystalline materials. She is particularly interested in how these materials grow, dissolve, assemble, and transform. The following images are high resolution images taken using the new Philips CM300 Transmission Electron Microscope located in Earth and Planetary Sciences.
Click on the images for high resolution view:
High resolution TEM micrograph showing a single crystal of synthetic anatase (TiO2). This unique morphology is the result of crystal growth by topotactic assembly. This material was synthesized by Gerko Oskam from Materials Science and Engineering at JHU:
High resolution TEM micrograph showing misoriented attachment between primary crystallites in synthetic heterogenite (CoOOH). This image shows only a small portion of the micron-sized plates (aspect ratio ~ 25 30) that form during synthesis:
Post-dissolution: synthetic heterogenite (CoOOH) particle constructed of ~3nm oriented primary particles. This image shows that the material to either side of the dissolution pathway is not perfectly oriented:
TEM micrograph showing oriented attachment in naturally-occurring heterogenite (CoOOH) from Nevada:
TEM micrograph showing misoriented attachment between primary crystallites in naturally-occurring heterogenite (CoOOH) from Nevada: