Colloidal processing of alumina-monazite composites

María T. Colomer 1Evelyn Rodriguez 1Antonio F. Fuentes 2Rodrigo Moreno 1

1. Institute of Ceramics and Glass (ICV-CSIC), Kelsen 5, Madrid 28049, Spain
2. Instituto de Ciencias de Materiales,CSIC-Universidad de Zaragoza de Aragón (ICMA), Zaragoza 50009, Spain

Abstract

Rare earth phosphates are known to possess very high melting points in the range 1900–2000 °C and have excellent thermal phase stability. Hence, they are considered excellent candidates to produce high refractory materials. Alumina-LaPO4 composites are thermally stable and LaPO4 successfully controls the grain growth of alumina, thus leading to enhanced thermomechanical properties.

This work deals with the shape forming of alumina-LaPO4 composites by a colloidal filtration route. A LaPO4 powder was synthesised by mechanochemical milling from lanthanum nitrate and di-hydrogen ammonium phosphate precursors. A commercial coarse alumina was used to obtain mixtures with 20, 30, and 40 wt.% of monazite phase (A80, A70, and A60, respectively). The starting powders and the mixtures were attrition milled and its effect on the physicochemical properties was studied, focusing on the particle size and shape, as well as the colloidal behaviour as a function of pH and adsorbed polyelectrolytes. The optimisation of the dispersing conditions was studied by measuring the rheological behaviour of concentrated suspensions of the mixtures. Suspensions of alumina and alumina-monazite prepared to a solids loading of 40 vol.% were slip cast in plaster moulds. Green cast bodies were characterized through densities determination and microstructural observations. Sintering treatments were studied in order to obtain dense materials.

 

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Presentation: Poster at E-MRS Fall Meeting 2009, Symposium I, by María T. Colomer
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-26 13:23
Revised:   2009-06-07 00:48