Al2O3–CaO macroporous ceramics containing hydrocalumite-like phases. Issue 5 (1st April 2020)

• Record Type: Journal Article
• Authors: Borges, O.H.; Santos, T.; Salvini, V.R.; Pandolfelli, V.C.
• Is Part Of: Ceramics international. Volume 46:Issue 5(2020)
• Page Start: 5929
• Page End: 5936
• Publication Date: 2020-04-01
• Subjects: Macroporous insulators -- Hydrocalumite -- Mayenite -- Sintering; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2019.11.046
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: A mechanism to explain the lower onset strengthening temperature induced by CaCO3 in alumina-based macroporous ceramics is proposed, which relies on hydrocalumite-like phase formation during processing. Close to 600 °C, such phases are decomposed to lime and mayenite (12CaO·7Al2 O3 ), where the latter, due to its intrinsic nanoporosity and high thermal reactivity, generates bonds between the ceramic particles at ∼700 °C, resulting in microstructure strengthening. Based on this premise, the authors concluded that other Ca 2+ sources could act similarly. Indeed, compositions containing Ca(OH)2 or CaO showed the same effect on the onset strengthening temperature, which reinforces the proposed mechanism. The results attained indicated that macroporous insulators could be thermally treated at lower temperatures, just to acquire enough mechanical strength for installation, finishing in-situ their firing process. Besides that, lower sintering temperatures could be used to produce macroporous ceramics that would be applied in low thermal demand environments, e.g. aluminum industries.