POROUS ALUMINA AND MULLITE-BASED CERAMICS PREPARED WITH STARCH OR WHEAT FLOUR: PROCESSING AND CHARACTERIZATION

W. PABST; E. GREGOROVA; T. UHLIROVA; M. VESELY; M. A. CAMERUCCI; M. TALOU

Conferencia; 12th International Conference on Ceramic Processing Science; 2013

Porous oxide and silicate ceramics, like alumina and mullite-based ceramics, are widely used as furnace linings and kiln furniture. Apart from light weight and material savings, the main advantage in these refractory applications is their low thermal mass. This work is concerned with the preparation of porous alumina and mullite-based ceramics using starch or wheat flour as pore formers, with the objective to prepare porous refractories with porosities exceeding 45 %. Starch consolidation casting (SCC) into metal molds is used for shaping, i.e. when using starch it acts as a fugitive pore former and as a stiffening agent, while in the case of wheat flour the SCC process is additionally accompanied by foaming. Porosities of more than 45 % can easily be achieved with starch and more than 60 % with wheat flour. A hierarchical microstructure with the largest pores of order 100-300 microns results in the case of processing with wheat flour. The work includes rheological studies (rotational viscometry), processing optimalization issues and microscopic investigation results concerning dry-green and as-fired samples. Quantitative image analysis of the pore space is performed using reliable microstructural descriptors such as the mean intercept length (surface density) and the mean curvature integral as well as Saltykov-transformed pore size distributions.