Sol-gel infiltration of complex cellular indirect 3D printed alumina

Gelled aqueous solutions containing the soluble precursor aluminum chlorohydrate were developed for the infiltration of porous indirect 3D printed alumina. Viscosity and amplitude sweep tests confirmed the gel formation and sheer thinning behavior beneficial for the subsequent coating and infiltration process. High temperature XRD confirmed the formation of corundum at a temperature of 1000 °C. Complex alumina structures with high surface area and isotropic pore channels were achieved by indirect 3D printing. Coating and infiltration of the pre sintered alumina with a subsequent sintering step transformed the precursor to corundum and partially filled the residual porosity and decreased surface defects after 3D printing. With the gel coating a pronounced improvement up to a maximum value of Δσcompr = 61.9 MPa was observed and with the gel infiltration a maximum improvement of ΔE = 136.2 GPa. The results show the possibility to infiltrate even complex alumina structures with aqueous alumina precursors without the need to disperse ceramic particles.