Funding period: Feb 2017 to Apr 2021

Researcher: Kathleen Dammler

Wrap-up

Keywords: replica technique, ice templating, freeze casting, alumina foams, hierarchial porosity, zeolites

Background:
Ceramic foams produced by the replica technique have many advantages due to their structure and material properties, but have a comparatively small surface area (compared to, e. g., fixed-bed reactor fillings). Furthermore, the potential of the production-related hollow strut was found to be expandable.

Objective:
Increase of the actively usable surface of replica ceramic foams while maintaining the mechanical strength

Methods:
Replica technique, sacrificial materials, Sol-gel-alumina powder, demixing, freeze casting

Results:
Through a combination of replica process and freeze processing, ceramic foams with at least doubled proportion of open strut porosity and a compressive strength around 1 MPa were produced.

The prepared specimens (total porosity ~ 90%), were extensively characterized in terms of strut porosity, width of pore and material lamellae, pore volume, object-surface to object-volume ratio and compressive strength. The most important process parameters for achieving stable and highly porous foams were identified as freezing temperature, solid content and amount of thickening agent.

In addition, it was shown that the foam supports, which contained additional pores, can be coated with a high load of zeolite MFI.

Conclusions:
The newly developed process has expanded the application range of replica ceramic foams, as the disadvantage of a comparatively small surface area was eliminated while maintaining sufficient mechanical strength.

Originality:
To the best of my knowledge, this approach has not been performed or studied in detail by anyone else in the way presented here.
The contribution of the work is seen as very profitable in terms of the use of replica ceramics as supports for active materials, for example, in catalysis applications.