Synthesis of a family of aluminium phosphonates

A family of four aluminium benzylphosphonate phases has been synthesised using hydrothermal methods. The effect of changing the synthetic conditions (starting pH, starting Al : P ratio, aluminium source etc.) has been studied and full structural characterisation of two of the phases by NMR, TGA and X-ray diffraction methods has been completed; Al(OH)(O3PCH2C6H5). H2O, monoclinic P2(1)/c, a = 14.985(9), b = 7.066(5), c = 9.613(9) Angstrom, beta = 113.9(3)degrees, and Al3H(PO3CH2C6H5)(5). H2O, monoclinic P2(1)/c, a = 17.2497(13), b = 25.7851(18), c = 9.4339(7) Angstrom, beta = 103.567(1)degrees.</p

Synthesis of a family of aluminium benzylphosphonates

A family of four aluminium benzylphosphonate phases has been synthesised using hydrothermal methods. The effect of changing the synthetic conditions (starting pH, starting Al : P ratio, aluminium source etc.) has been studied and full structural characterisation of two of the phases by NMR, TGA and X-ray diffraction methods has been completed; Al(OH)(O3PCH2C6H5). H2O, monoclinic P2(1)/c, a = 14.985(9), b = 7.066(5), c = 9.613(9) Angstrom, beta = 113.9(3)degrees, and Al3H(PO3CH2C6H5)(5). H2O, monoclinic P2(1)/c, a = 17.2497(13), b = 25.7851(18), c = 9.4339(7) Angstrom, beta = 103.567(1)degrees.</p

Elaboration of CO2 tolerance limits of BaCe0.9Y0.1O3-delta electrolytes for fuel cells and other applications

The carbonation and decarbonation behaviour of BaCe0.9Y0.1O2.95 (BCY 10) powder has been investigated as a function of gas composition and temperature by thermogravimetric analysis and X-ray powder diffraction. The results obtained have been used to establish stability limits, which seem to indicate long-term stability for BCY10 under certain conditions.BCY10 powder is stable in pure CO2 above 1150 degrees C. In atmospheres containing up to 9% CO2 in argon, BCY10 is stable above 750 degrees C. Carbonated powders loose CO2 above 700 degrees C when heated in air, or oxygen and at 620 degrees C in 5% hydrogen. BCY 10 partly decomposes on ageing in pure CO2 at 500 degrees C. The onset of the reverse water-gas shift reaction changes to lower temperatures in the presence of BCY10 powder.These results were obtained for powder samples and should be viewed as air accelerated ageing test. Overall these results imply that under fuel cell conditions BCY10 should be resistant to carbonation even in a hydrocarbon fuelled fuel cell at temperatures above 750 degrees C. In the worst case scenario with 100% hydrocarbon oxidation, no added water and assuming no localised benefit from the gas shift reaction carbonation could occur up to 925 degrees C. Fully densified electrolytes, especially with an electrode coating, should be much more resistant to carbonation, at least when there is no exolved alkaline earth rich phases at the grain boundary, something that can occur with unoptimised sintering or inappropriate choice of stoichiometry. (c) 2005 Elsevier B.V. All rights reserved.</p

Elaboration of CO2 tolerance limits of BaCe0.9Y0.1O3-delta electrolytes for fuel cells and other applications

The carbonation and decarbonation behaviour of BaCe0.9Y0.1O2.95 (BCY 10) powder has been investigated as a function of gas composition and temperature by thermogravimetric analysis and X-ray powder diffraction. The results obtained have been used to establish stability limits, which seem to indicate long-term stability for BCY10 under certain conditions.BCY10 powder is stable in pure CO2 above 1150 degrees C. In atmospheres containing up to 9% CO2 in argon, BCY10 is stable above 750 degrees C. Carbonated powders loose CO2 above 700 degrees C when heated in air, or oxygen and at 620 degrees C in 5% hydrogen. BCY 10 partly decomposes on ageing in pure CO2 at 500 degrees C. The onset of the reverse water-gas shift reaction changes to lower temperatures in the presence of BCY10 powder.These results were obtained for powder samples and should be viewed as air accelerated ageing test. Overall these results imply that under fuel cell conditions BCY10 should be resistant to carbonation even in a hydrocarbon fuelled fuel cell at temperatures above 750 degrees C. In the worst case scenario with 100% hydrocarbon oxidation, no added water and assuming no localised benefit from the gas shift reaction carbonation could occur up to 925 degrees C. Fully densified electrolytes, especially with an electrode coating, should be much more resistant to carbonation, at least when there is no exolved alkaline earth rich phases at the grain boundary, something that can occur with unoptimised sintering or inappropriate choice of stoichiometry. (c) 2005 Elsevier B.V. All rights reserved.</p

Synthesis and structure of an aluminium 3-aminopropylphosphonate sulfate hydrate

A new aluminium 3-aminopropylphosphonate sulfate hydrate has been prepared using hydrothermal methods, and its structure solved using microcrystal X-ray diffraction at a synchrotron source. The structure consists of one-dimensional chains of aluminium 3-aminopropylphosphonate with sulfate anions occluded between the chains. It is unusual in compounds of this type to have anionic groups between positively charged aluminium phosphonate units. Further characterisation of the compound has been carried out using magic angle spinning NMR.</p