Sintering study of digital light process printed zeolite by positron, thermogravimetric and x-ray techniques

Abstract

This study examined the sintering of digital light process (DLP)-printed zeolite 13X with two different phyllosilicate binders—bentonite and kaolin. DLP printing offers the potential for developing a robust additively manufactured zeolite structure that can improve upon typical adsorption column configurations by employing additively manufactured triply periodic minimal surface (TPMS) structures. Zeolite 13X is a crystalline alumina silicate material with applications in pressure swing adsorption (PSA) for CO2 and N2 gas refinement and for adsorption cooling systems. The present study developed a process to fabricate zeolite parts by DLP printing where the TPMS structures were found to hold together much better than the printed discs. Thermogravimetric analysis was used to develop debinding and sintering curves and x-ray diffraction was performed to confirm the crystalline structure of the zeolite was preserved. The micropore structure and distribution were characterized with positron annihilation lifetime spectroscopy (PALS) to investigate the effects of sintering on pore size and density. From the PALS analysis, it is concluded that DLP printing produces samples with a high surface area; however, the sintering process destroys a regular nanostructure into less regular, less crystalline, and more amorphous structure pores, which is visible by more trapping and less positronium formation with sintering in the PALS parameters.