Anhydrous sol-gel condensation of triethyl phosphate [(CH3CH2O)3PO] with boron trichloride (BCL3 ) or triethyl aluminum [(CH3CH2 ) 3A1] in organic solvents, led to formation of metallophosphate gels. The pore fluid of the gels was removed under supercritical conditions in a pressurized vessel to form aerogels. The aerogels were then calcined at progressively higher temperatures to produce high surface area phosphates. Since the initial gel reagent mixtures contained several NMR active nuclei, the condensation chemistry prior to the gel point was monitored by solution nB NMR. The surface areas, distribution of pore sizes, and total pore volumes of the aerogel products were determined using nitrogen gas physisorption methods.
Lindquist, David A.; Poindexter, Steven M.; Rooke, Sterling S.; Stockdale, D. Ritchie; Babb, Kirk B.; Smoot, Alison L.; and Young, William E.
"Boron Phosphate and Aluminum Phosphate Aerogels,"
Journal of the Arkansas Academy of Science: Vol. 48
, Article 21.
Available at: http://scholarworks.uark.edu/jaas/vol48/iss1/21