This week we feature another SEM image of the etched, fired ceramic surface we’ve been examining the past few weeks.  This view looks into a small pit/cavity with an overgrowth of plate-like crystals jumbled together with needle-like (acicular) crystals.  The needles are most likely composed of mullite, also known as porcelainite, an aluminosilicate material found commonly in fired ceramics.  A scale bar of one micron (one thousandth of a millimeter) is shown in the full image below; these are some small crystals in this image!

K-12 STEAM Connections:  What is the melting temperature of mullite, and how does that compare with the melting temperatures of glass, aluminum and steel?  How do mullite crystals contribute to the mechanical properties of porcelain?

Acknowledgments:  Part of this work was performed at the Stanford Nano Shared Facilities (SNSF) of Stanford University.