Characterization and production of slip casts mullite–zirconia composites

Abstract

In this study, mullite-zirconia composites were prepared by reaction sintering of alumina, kaolinite zircon and colemanite powder. Slip casting method was also employed for production of these composites. Two different compositions were prepared with and without colemanite additive. The main purpose of this work was to determine the optimum conditions for mullite-zirconia synthesis in addition to the effects of starting composition, solid concentration of aqueous suspensions and sintering temperature. The resulting sintered materials were characterized in terms of bulk and relative density, firing shrinkage, XRD and SEM. XRD peaks suggested fully developed mullite and zirconia phases by reaction sintering of zircon, kaolinite, alumina and colemanite phases. Zircon usually dissociates at a temperature higher than 1650 °C. However, it has been shown in this study that zircon dissociates at about 1450 °C due to the presence of colemanite. The results of the study indicate that 90% of relative density was achieved as the solid concentration is increased up to 55% in case for slip-casted specimens with colemanite additive (MZC55 with 55% solid concentration). The microstructure of all composites is composed of irregularly shaped mullite grains and round-shaped zirconia grains which are distributed intragranularly and intergranularly.

Crystallite growth limits in amorphous oxides

“…Conversely, the novel 4th order term is strongly affected by the value of Y, and the density ratio ρ c /ρ a (equation ( 9)). The densities ρ c of the crystalline phase for each material have well known values from literature and were kept fixed (Ottermann et al 1996, Alderman et al 2018, Aydin and Tokatas 2019.…”

Toughening Mechanism of Mullite Matrix Composites: A Review

“…Reinforced mullite ceramics are often used as industrial refractories because of their high refractory, good thermal shock resistance, chemical erosion resistance, creep resistance, etc. As shown in Figure 4d, a zirconia mullite refractory is used in the glass industry [38]. Alumina-mullite ceramics with low glass phase content have good hardness and strength, and have high armor and wear resistance application potential [39].…”

Digital light processing additive manufacturing of in situ mullite-zirconia composites

“…Several forming methods (extrusion [13], pressing [3,14], slip casting [15,16], and gel casting [8]) have been studied in the manufacture of mullite-zirconia parts. However, the fabrication of such material by additive manufacturing (AM) has still been little explored and, to the best of our knowledge, has never been reported.…”