Hydroxyapatite-imidazole-polymer composite films as a proton conductor under no humidified condition
H. Tsutsumi and Y. Hisha
Yamaguchi University, JP
proton conductor, dry condition, polymer electrolyte membrane fuel cell
We prepared the proton conduction system, hydroxyapatite (HAp)-imidazole (Im)-polymer composite films and investigated their structure, conduction behavior and mechanical properties. HAp particles used in our investigation were prepared with two different ways, a-HAp and n-HAp. Both kinds of hydroxyapatite particles, a-HAp and n-HAp, are partially amorphous and calcium ion-deficient HAp. Average particle size of a-HAp was 1.25 um and n-HAp was 0.61 um in diameter. An HAp-Im-polymer composite film was prepared by casting the HAp-dispersed solution which contains Im and polymer on a plate and then removing the solvent (indirect method). Another preparation procedure (direct method) of the HAp-Im-PVdF composite film, d-HAp-Im-PVdF, was also investigated. The d-HAp-Im-PVdF composite films were prepared by mixing the aqueous solution for HAp preparation and the DMF solution which contains PVdF and Im. Conductivity at 120°C was 0.0084 mS cm-1 for a-HAp-Im-PVdF (1: 2: 5), 2.98 mS cm-1 for n-HAp-Im-PVdF (1: 2: 5), 7.33 mS cm-1 for d-HAp-Im-PVdF (2:2:5). Conductivity for HAp-Im-PVdF composite film depends on the particle size and dispersibility of HAp in the matrix. Microscopic observation of the composite films suggests that smaller HAp particles were well dispersed in the PVdF matrix. Addition of HAp in the composite films improves the mechanical properties of PVdF film at 100°C.
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