In my fourth year of undergraduate I attended pottery classes in the SU, where, among many hand formation techniques, the tutor briefly went into some scientific detail into how clay and the firing process works. I found that random mini-science lesson really interesting, especially seeing how unexpectedly it happened! What luck that ceramics would once again cross my path! Yesterday Prof. Özge Akbulut, a materials engineer and Associate Professor at Sabanci University, Turkey, came to Imperial College to give a talk on her recent work looking at creating "green body" ceramics that can be easily machined without the addition of a large amount of additives.
In ceramics, clay is a suspension of clay particles surrounded by water, and is mouldable because the clay particles can slide around. This is known as the "green" state. When clay is placed into the kiln and fired, the water evaporates and the clay particles fuse together, making the material go hard and brittle. This is known as the "sintered" state. Machining (e.g. drilling, cutting) sintered ceramics requires expensive, hardy, diamond-tipped tools to prevent tools wearing down too fast, and all the material that is removed is simply lost. Machining a green requires less expensive tools, wears down tools a lot slower, and any removed material can be recovered and reused. However, green bodies are too soft to machine and will not hold their shape enough. Green bodies can be made more viscous by adding extra chemical components, but often these components can be toxic and are sometimes present in very large amounts (up to 15%!). Having too much additive can lead to cracks and breakages in the sintering process - not good! Other techniques can also be used to create dough-like green bodies, but these often require expensive equipment, limiting the widespread use of such techniques.
Prof. Akbulut and colleagues have been looking at polymers (chemicals formed of long chains) that can be added in smaller amounts (~1%) to create green bodies that can be easily formed, laser-cut and drilled. This means that complex shapes or structures can be formed before sintering rather than just afterwards, all while keeping additive content low (preventing cracks forming) and reducing costs (due to no specialist equipment required, less additive needed, and less wastage of ceramic materials).
They have also invited companies to collaborate using this novel process in an open call, hoping to further innovate and eventually make a commercial impact. I wish them every success and hope to see this material used widely in the near future!
Images ©Philip Coatsworth (top 2), ©Özge Akbulut
Lyn Zemberekci, Gizem Demir, Can Akaoglu, Wael Ali Aldulaimi, Aleyna Beste Ozhan, Mehmet Ali Gulgun, Omid Akhlaghi, and Ozge Akbulut (2021) Polymer Bridging Induced by a Single Additive Imparts Easy-To-Implement Green Machinability to Yttria-Stabilized Zirconia. ACS Applied Polymer Materials 20213 (11), 5397-5404 https://doi.org/10.1021/acsapm.1c00605