Preparation of Mullite Ceramics from Coprecipitated Aluminum Hydroxide and Kaolinite Using Hexamethylenediamine |
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Authors: | José Pascual José Zapatero María C Jiménez de Haro Antonio J Ramírez del Valle José L Pérez-Rodríguez Pedro J Sánchez-Soto |
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Affiliation: | Departamento de Ingeniería Civil, de Materiales y Fabricación, Escuela Técnica Superior de Ingenieros Industriales, Universidad de Málaga, 29013 Málaga, Spain;Instituto de Ciencia de Materiales, Centro Mixto Consejo Superior de Investigaciones Científicas (C.S.I.C.), Universidad de Sevilla, 41092 Sevilla, Spain |
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Abstract: | 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. |
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Keywords: | mullite kaolinite aluminum |
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