Abstract
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.
Highlights
Published: 3 November 2021A geopolymers are well-known alkali aluminosilicate cement materials that can have superior mechanical, chemical and thermal properties when compared to other Portlandbased cements, showing significantly lower levels of CO2 production [1]
NaOH are the most common subjects, so the aim of this study is to examine the effect of Nd and Sm in the form of oxide incorporation in the first phase of gelation of the geopolymer Gels 2021, 7, x FOR PEER REVIEW
The incorporation of neodymium and samarium ions into the geopolymer matrix was the aim of this research
Summary
Published: 3 November 2021A geopolymers are well-known alkali aluminosilicate cement materials that can have superior mechanical, chemical and thermal properties when compared to other Portlandbased cements, showing significantly lower levels of CO2 production [1]. Rare earth elements (REEs) have become increasingly important metals used in modern technology and potential applications. Their increasing use in the industrial sector, medicine and agriculture over the last few decades has provided them with the title of “new pollutants” [13]. XRD measurements were conducted at room temperature using Ultima IV Rigaku diffractometer, equipped with CuKα1,2 radiation, using a generator voltage (40.0 kV). Samples were crushed in the in a porcelain mortar to the fineness of a fine powder. The PDXL2 (Ver. 2.8.4.0) software was used to evaluate the phase identification and microstructure properties of material [62,63]. All obtained powders were identified using the ICDD data base [64]. For phase identification, selected PDF card numbers were used: Quartz (SiO2 ; 01-079-6237), Albite (Na(AlSi3 O8 ); 01-0840982), Muscovite (KAl2 (Si,Al) O10 (OH)2 ; 00-058-2036), Samarium Oxide (Sm2 O3 ; 00-042-1464), Neodymium Hydroxide Nd (OH)3 , 01-070-0214) and Neodymium oxide (Nd2 O3 , 00-006-0408)
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