Additive manufacturing of novel lightweight insulation refractory with hierarchical pore structures by direct ink writing

Abstract

A direct ink writing process using fly ash foaming slurries was employed for the additive manufacturing of lightweight mullite insulation refractory with hierarchical pore structures. The viscosity, thixotropy, and shear thinning behavior of the inks were analyzed to investigate the effect of the inorganic binder and dispersant of the foaming inks. A slurry exhibiting excellent rheological characteristics was identified, consisting of 45 wt% fly ash floating beads, 55 wt% water, 3.0 wt% additional dispersant, and 6.0 wt% additional binder. Furthermore, through the optimization of printing parameters such as printing pressure and printing speed, notable enhancements were achieved in the pore structure and properties of the final insulation refractory. Upon heating the lightweight insulation refractory to 1300 °C, the bulk density, compressive strength, and thermal conductivity were determined to be 0.61 g/cm3, 1.01 MPa, and 0.13 W/(m·K), respectively. The direct ink writing technique demonstrates substantial potential in manufacturing lightweight refractories that possess superior thermal insulation and reliable usage strength.