Clot-forming: the use of proteins as binders for producing ceramic foams

This project uses the change of functional properties of proteins for ceramic and powder metallurgical shaping. Albumin (Bovine Serum Albumin, BSA) as a major constituent of blood was added as a model binder to an aqueous powder suspension, which then showed a sufficiently low viscosity for mould filling. The flow behaviour showed a structural viscosity being best described by a Herschel-Bulkley model. Temperatures higher than 66 degreesC lead to a significant increase of viscosity caused by irreversible changes in the spatial-structure of the protein molecule. Albumin, however, had a second effect in this process. Since albumin has amphiphilic properties its solutions are prone to foaming. A fine cellular foam structure of approximately 50-300 mum cell diameter was formed, probably due to a stable arrangement at the liquid gas interface. The combination of foaming and increase of stiffness lead to a stable protein-ceramic foam structure. After burn out and sintering final densities in the range from 8 to 20% t.d. were achieved. Fine cellular structures have more isolated pores while larger cells are typically interconnected. Typical applications would be high temperature insulation, catalyst carriers or scaffolds for cell technology. (C) 2003 Published by Elsevier Ltd.