Highly-closed/-Open Porous Ceramics with Micro-Beads by Direct Foaming

Abstract

This study reports on wet-foam stability with respect to porous ceramics from a particle-stabilized colloidal suspension that is achieved through the addition of polymethyl methacrylate (PMMA) using a wet process. To stabilize the wet foam, an initial colloidal suspension of Al 2 O 3 was partially hydrophobized by the surfactant propyl gallate (2 wt.%) and SiO 2 was added as a stabilizer. The influence of the PMMA content on the bubble size, pore size, and pore distribution in terms of the contact angle, surface tension, adsorption free energy, and Laplace pressure are described in this paper. The results show a wet-foam stability of more than 83%, which corresponds to a particle free energy of 2.7 × 10 −12 J and a pressure difference of 61.1 mPa for colloidal particles with 20 wt.% of PMMA beads. It was possible to control the uniform distribution of the open/closed pores by increasing the PMMA content and by adding thick struts, leading to the achievement of a higher-stability wet foam for use in porous ceramics.

Wet Foam Stability from Colloidal Suspension to Porous Ceramics: A Review

“…The average contact angle of the d 50 -3.5 µm SiO 2 suspension increased with the increase in SiO 2 content. 157) In Fig. 13(b)-(d), the suspensions with content between 25 and 30 vol.% of SiO 2 were found to be highly stable with a higher level of surface tension, resulting in highly stable foams to sintered porous ceramics.…”