Posted by Hideo Mabuchi
Today’s featured image is a “small” image in that it is only 256×256 pixels, but it conveys a lot of information! Last week we discussed how the EDS (Energy-Dispersive Spectroscopy) tool on an electron microscope can provide information on not only the topography but the elemental composition of microscopic features on a ceramic surface, but we noted that the spatial resolution of this technique is insufficient to provide strong evidence in support of the idea that red iron oxide (hematite) crystals decorate the edges of larger alumina hexagonal platelets. Today’s featured image was acquired using a very sophisticated instrument called a nanoSIMS (nano Secondary Ion Mass Spectrometer). The featured image is a false-color image of one of our familiar hexagons, in which green indicates the presence of silicon, blue indicates the presence of alumina, and red indicates the presence of iron. Here we more clearly see that iron is localized to the exposed edges of the hexagonal platelet, which itself is clearly an alumina crystal. In the original work by Y. Kusano and co-workers on alumina, hematite and flashing colors, a rather different technical approach was utilized that required removal of the hexagonal platelets from the ceramic surface so that they could be studied in isolation using a TEM (Transmission Electron Microscope) instrument. That body of research provides quite detailed and conclusive identification of the hematite and alumina crystals. Here in this series of NCECA blog posts however we will stick to analysis techniques that allow us to study microstructures on fired ceramic surfaces in situ.
K-12 STEAM Connections: Some of your students may not be familiar with, or fully understand, the concept of a false-color image. More common examples of false-color images include weather maps, thermal images, and red/blue/purple election maps of the USA. As noted in the brief Wikipedia article on false color, “false color” representations can be used to artistic effect as in the work of Andy Warhol…
Acknowledgments: Part of this work was performed at the Stanford Nano Shared Facilities (SNSF) of Stanford University.