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Published online by Cambridge University Press: 01 February 2011
Ordered-mesoporous-Al2O3 was synthesized by the sol-gel route using neutral copolymer surfactants as templates. The pore size was controlled over the range of 3∼22 nm by using different surfactant copolymers under different synthetic conditions. Protonic conductivity of hydrated mesoporous alumina was examined for CIP treated mesoporous alumina pellet. The highest protonic conductivity was obtained as 0.004 S· cm−1 at 25 °C under 80% RH for the pellet with 15 nm averaged pores. The conductivity increased monotonically with increasing pore size under constant humidity. Quantitative determination of the concentration and the mobility of protons in hydrated mesoporous alumina was performed by 1H NMR, quasi-elastic neutron scattering (QENS) and TG/DTA measurements. Both the mobility and the concentration increased with increasing pore size. On the other hand, composites composed of synthesized mesoporous-Al2O3 and lithium iodide (LiI) was prepared. Dc electrical conductivity of 50LiI.50(mesoporous-Al2O3) was 2.6×10−4 S cm−1 at room temperature, which was considerably higher than the previously reported LiI-alumina composites. A systematic dependence of conductivity upon pore size was observed, in which the conductivity increased with decreasing the pore size except for pore size=3 nm. The 7Li diffusion constant of the composite was investigated by QENS as well as pulsed field gradient nuclear magnetic resonance (PFG-NMR). The dc conductivities showed reasonable agreement with an Einstein equation using measured diffusion constants.