M.Sc Thesis


M.Sc StudentDavid Fuks
SubjectHighly Porous Ceramics Based on Foamed Suspensions
DepartmentDepartment of Chemical Engineering
Supervisor Full Professors Grader Gideon
Full Thesis textFull thesis text - English Version


Abstract

Porous ceramics foams are being used in an increasing number of industrial applications such as high temperature thermal insulation, hot gas particulate filters, hot metal filters, catalyst support and cores in high temperature structural panels. This growing usage stems from the foam’s favorable properties such as low density, low thermal conductivity, thermal stability and high resistance to chemical attack. There are different routes to produce ceramic foams. Recently Ludwig Gauckler and his team developed a new method for producing of the ceramic foams. This method based on preparation of highly concentrated colloidal suspensions, where the particles surface is modified by adsorption of short organic acids. The final step of producing the stable wet foams is done by mechanical high speed stirring of the suspension. Afterwards the wet green foams undergo different thermal treatments such as drying and sintering. This research is focused on finding the appropriate working conditions at the earlier stage and exposing of different problems at each of the procedural steps, understanding the sources for those problems and trying to find appropriate solutions at the latter stage. Cracks formation during the drying, was found to be a biggest problem of this technique. Understanding of the reasons for cracks formation during the drying stage (during the liquid evaporation) might provide possible solutions to this problem.  In this study, we suggest a different procedure for successful drying of the wet foams. Our solution is based on the addition of miscible low volatile liquids to the aqueous phase. This method may allow the execution of the drying process much faster and cheaper than several standard routes. Another aspect of the research involves the development of a different foaming technique by using a Chemical Foaming Agent (CFA) instead of mechanical foaming. The significance of this development is the ability to produce materials with fewer internal imperfections.