2, University of Arizona, Tucson, Arizona, United States
3, University of Arizona, Tucson, Arizona, United States
4, University of Arizona, Tucson, Arizona, United States
Alkali alumino-silicate glasses are important technological materials due to their high heat resistance, thermal stability and dielectric properties. Further, porous alkali alumino-silicate structures have been used as thermal insulation barriers as well in catalysis. In this context, capabilities to print porous alkali alumino-silicate structures using a specialized 3-D paste-printing technique have been developed. Specifically, using silica and alumina powders in conjunction with NaOH, as well as appropriate surfactants and blowing agents, the ability to print sodium aluminum silicate (NAS) foams of controllable macro- and meso-porosity is demonstrated. In addition, we also incorporate certain fillers to produce composite foams with improved mechanical strength. The effects of key variables such as feed ink formulations and their rheology, print rates as well as cure temperatures on final microstructure, density and pore sizes are reported. SEM, FTIR and NMR studies were also carried out to examine the structural and bonding characteristics of the 3-D printed foams. Comparisons with analogous structures obtained by other conventional techniques such as direct curing and sol-gel process provide a basis to assess the relative advantages of using 3-D paste printing techniques for fabricating mechanically robust porous NAS foams.