New insights into the thermal evolution of aluminophosphate solutions: A complementary XRD and solid state NMR study

Rationalization of the X-ray photoelectron spectroscopy of aluminium phosphates synthesized from different precursors

“…As the annealing temperature increases, there is a trend towards increasingly negative 31 P chemical shis, attributed to polymerization. 16 For AlP OH (300), a broad set of overlapping peaks is observed between 5 ppm and À40 ppm, possibly suggesting an amorphous structure. The peaks at À21 ppm and À32 ppm (which represent ca.…”

“…The peaks at À21 ppm and À32 ppm (which represent ca. 20% of the total signal) are assigned 16 to aluminium tripolyphosphate (AlH 2 P 3 O 10 $H 2 O). These peaks are also observed for AlP NO 3 (300).…”

Effect of the P/Al Molar Ratio and Heating Rate on the Composi-Tion of Alumino-Phosphate Binders

“…Those binders are generally prepared by heat-treating alumino-phosphate solutions that are obtained by dissolving Al 2 O 3 or Al(OH) 3 in diluted phosphoric acid solutions. Such solutions, characterised by their P/Al molar ratio, their phosphorus concentration [P], and the presence of additives, have also been widely investigated [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. By heating, the alumino-phosphate species of the solutions react to form hydrated alumino-phosphate compounds (Al(H 2 PO 4 ) 3 , × H 2 O and AlH 2 P 3 O 10 , × H 2 O) around 150–350 °C.…”

“…The presence of Al(PO 3 ) 3 [A] is beneficial for the development of binders because this compound is stable and only melts at temperatures higher than 1200 °C. Several studies have been performed on solutions with a P/Al molar ratio of 3 because they present a similar P/Al ratio than the final Al(PO 3 ) 3 [A] phase [ 1 , 2 , 3 , 4 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. Solutions with a P/Al ratio lower than 3 produce binders composed of Al(PO 3 ) 3 but also AlPO 4 compounds [ 3 , 4 ].…”

“…Solutions with a P/Al ratio higher than 3 contain phosphoric acid in excess (not participating in the formation of the Al(PO 3 ) 3 compounds) and have not been widely studied. However, we showed, in a previous investigation, that Al(PO 3 ) 3 [A] appears at lower temperature with a P/Al = 3.5 solution, which can be considered as an advantage compared to the classic formulation [ 10 ]. We also showed that the binders contain residual phosphoric acids (H 3 PO 4 , H 4 P 2 O 7 , or HPO 3 , denoted in the following as HPO n ).…”