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Preparation of Mullite Ceramics from Coprecipitated Aluminum Hydroxide and Kaolinite Using Hexamethylenediamine
Author(s) -
Pascual José,
Zapatero José,
Haro María C. Jiménez,
Valle Antonio J. Ramírez,
PérezRodríguez José L.,
SánchezSoto Pedro J.
Publication year - 2000
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/j.1151-2916.2000.tb01614.x
Subject(s) - mullite , ammonium hydroxide , materials science , kaolinite , hydroxide , aluminium hydroxide , ceramic , aluminium silicate , aluminium , inorganic chemistry , chemical engineering , chemistry , metallurgy , engineering
Mullite ceramics have been prepared from an aqueous suspension of kaolinite (raw or ground) and aluminum hydroxide. The precursor was coprecipitated in the mixture using hexamethylenediamine (HMDA) or ammonium hydroxide, and a solution of aluminum chloride from acid dissolution of wastes of aluminum metal. The precursor and the resulting materials were characterized and studied by X‐ray diffraction, thermal methods, and mechanical strength and porosity measurements. The feasibility of the proposed chemical processing route for mullite preparation was demonstrated, in particular using HMDA as a precipitating agent for aluminum hydroxide instead of ammonium hydroxide, which adversely affects the system reactivity. The use of HMDA, as compared with ammonium hydroxide, and ground kaolinite produces single‐phase mullite and enhances the flexural strength (maximum of 49 MPa) of the resultant ceramic porous bodies (porosity ca. 52–45 vol%) fired at 1550–1600°C for 30 min.