Investigation on properties of Al2O3-SiO2 complex shaped refractory fabricated by layered extrusion forming

As one of the 3D printing methods, layered extrusion forming (LEF) has distinct advantages to form complex configuration ceramics directly. The feasibility of using LEF to make refractory products with complex shapes was explored by this work, using water-based Al2O3-SiO2 ceramic slurry and specially equipped device. By measuring rheological parameters, the effects of binder addition, dispersant addition and volume proportion of the solid portion composed of alpha-Al2O3 ultrafine powder (92 wt%) and silica fume (8 wt%) on rheological behavior of the slurry were investigated. The green body specimens prepared by the LEF were fired at 1400 degrees C-1600 degrees C for 3h. The influence of firing temperature on phase composition, microstructure, sintering degree and comprehensive properties of the specimens was investigated. At 2.5 wt% addition of aluminum dihydrogen phosphate as binder, 0.2 wt% addition of sodium hexametaphosphate as dispersant and with solid portion between 56 vol% and 58 vol%, required pseudoplastic behavior of the slurry can be achieved, suitable for the LEF. With the increase of heating temperature, mullitization by the reaction between the alpha-Al2O3 ultrafine powder and silica fume becomes stronger and sintering gets enhanced, leading to improved comprehensive properties of the specimens. Fired at 1600 degrees C, properties in terms of bulk density 3.03g/cm(3), cold compressive strength 190.5 MPa and refractoriness under load 1598 degrees C are achieved. Crucible slag test shows a good resistance to the glass melt corrosion. Good feasibility of fabricating some complex shaped refractory products by LEF as a novel forming approach has been confirmed by the present work.