Structural and Chemical Properties of Geopolymer Gels Incorporated with Neodymium and Samarium

The present work was focused on doping of 1% and 5% both of Nd2O3 and Sm2O3 in geopolymer gels. One of the main goals was to determine the influence of the behavior of Nd and Sm as dopants and structural nanoparticles changes of the final geopolymer formed. It is shown that the disorder formed by alkali activation of metakaolin can accommodate the rare earth cations Nd3+ and Sm3+ into their aluminosilicate framework structure. The main geopolymerization product identified in gels is Al-rich (Na)-AS-H gel comprising Al and Si in tetrahedral coordination. Na+ ions were balancing the negative charge resulting from Al3+ in tetrahedral coordination. The changes in the structures of the final product (geopolymer/Nd2O3; Sm2O3), has been characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analysis with energy dispersive spectrometry (EDS). Nucleation at the seed surfaces leads to the formation of phase-separated gels from rare earth phase early in the reaction process. It is confirmed that Nd and Sm have been shown to form unstable hydroxides Nd(OH)(3) and Sm(OH)(3) that are in equilibrium with the corresponding oxides.

Automated summary

This study focused on doping Nd2O3 and Sm2O3 in geopolymer gels to investigate the influence of rare earth elements. It was found that the rare earth cations can be accommodated into the aluminosilicate framework structure, forming Al-rich (Na)-AS-H gel, and the nucleation at the seed surfaces leads to the formation of phase-separated gels. Additionally, unstable hydroxides formed by Nd and Sm were in equilibrium with the corresponding oxides.