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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on NaAlO2 by Materials Project

NaAlO2 is Caswellsilverite structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Na1+ is bonded to six equivalent O2- atoms to form distorted NaO6 octahedra that share corners with six equivalent AlO6 octahedra, edges with six equivalent NaO6 octahedra, and edges with six equivalent AlO6 octahedra. The corner-sharing octahedral tilt angles are 14°. All Na–O bond lengths are 2.36 Å. Al3+ is bonded to six equivalent O2- atoms to form AlO6 octahedra that share corners with six equivalent NaO6 octahedra, edges with six equivalent NaO6 octahedra, and edges with six equivalent AlO6 octahedra. The corner-sharing octahedral tilt angles are 14°. All Al–O bond lengths are 1.96 Å. O2- is bonded to three equivalent Na1+ and three equivalent Al3+ atoms to form a mixture of corner and edge-sharing ONa3Al3 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaAlO2 by Materials Project

NaAlO2 crystallizes in the orthorhombic Pna2_1 space group. The structure is three-dimensional. Na1+ is bonded to four O2- atoms to form distorted NaO4 tetrahedra that share corners with four equivalent NaO4 tetrahedra and corners with eight equivalent AlO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.34–2.39 Å. Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four equivalent AlO4 tetrahedra and corners with eight equivalent NaO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.77–1.79 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+ and two equivalent Al3+ atoms. In the second O2- site, O2- is bonded to two equivalent Na1+ and two equivalent Al3+ atoms to form distorted corner-sharing ONa2Al2 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Combined effect of NaAlO2 and NaOH on the early age hydration of Portland cement with a high concentration of borate solution

The early age hydration of ordinary Portland cement in 5 M borate solution, with or without the addition of NaAlO{sub 2} and/or NaOH, was investigated. Hydration was measured using calorimetry, X-ray diffraction, thermogravimetric analysis, {sup 11}B and {sup 27}Al magic angle spinning NMR analysis, and scanning transmission electron microscopy. The purpose of this study was to reveal the mechanisms behind the retardation caused by a high concentration borate solution and the restoration of hydration through the combined addition of NaOH and NaAlO{sub 2}. Amorphous ulexite, which formed on the surface of the cement particles and prevented the further dissolution of anhydrous phases, was identified as the retardation product. The mechanism of the combined addition of NaAlO{sub 2} and NaOH in overcoming retardation was to transform amorphous ulexite into B-AFt and gowerite (CaB{sub 6}O{sub 10}·5H{sub 2}O). Formation of gowerite is favorable because of the much higher boron immobilization capacity in weight percentage, comparing to usual boron-containing phases reported previously.

36 MATERIALS SCIENCE↗