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Highly porous mullite ceramics from engineered alkali activated suspensions
Author(s) -
Rincón Romero Acacio,
Elsayed Hamada,
Bernardo Enrico
Publication year - 2018
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.15327
Subject(s) - mullite , materials science , chemical engineering , alkali metal , geopolymer , ceramic , ammonium nitrate , porosity , suspension (topology) , rheology , ion exchange , viscosity , composite material , ion , chemistry , compressive strength , organic chemistry , mathematics , pure mathematics , engineering , homotopy
Air may be easily incorporated by vigorous mechanical stirring, with the help of surfactants, of activated geopolymer‐yielding suspensions. The cellular structure is stabilized by the viscosity increase caused by curing reactions, configuring an “inorganic gel casting”. The present paper is aimed at extending this approach to mullite foams, obtained by the thermal treatment of engineered alkali activated suspensions. “Green” foams were first obtained by gel casting of a suspension for Na‐geopolymer enriched with reactive γ‐Al 2 O 3 powders. Sodium was later extracted by ionic exchange with ammonium salts. In particular, the removal of Na + ions was achieved by immersion in ammonium nitrate solution overnight, with retention of the cellular structure. Finally, the ion‐exchanged foams were successfully converted into pure mullite foams by application of a firing treatment at 1300°C, for 1 hour. Preliminary results concerning the extension of the concept to mullite three‐dimensional scaffolds are presented as well.