발간논문

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The hydrogen storage properties of (CFM)Ni_5 were investigated by varying the amount of excess CFM, where CFM denotes Ce-free misch metal. The results showed that, within 10% of excess CFM, the unit cell volume, the standard enthalpy change for hydrogen desorption and the effective hydrogen storage capacity increased while the plateau pressure decreased. When the amount of excess CFM was higher than 10%, the effective hydrogen storage capacity decreased whereas the other properties remained nearly constant. It was suggested that about 10% of the excess rare earth metal should be added during the melting process in order to fabricate the best hydrogen storage alloy in rare earth-nickel system.

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The ultrasonic attenuation of low temperature peaks in the PdD_(.67) has been studied. The peak is seen only for longitudinal waves, not for transverse ones, and it is observed only in the deuterides, not in the hydrides. The low temperature peak is correlated with relaxation phenomenon due to redistribution of LO phonons by ultrasonic waves. Ultrasonic attenuation of the PdD_(.67)H_(.02) sample was measured to see the influence of hydrogen in the PdD_(.67); the low temperature peaks of the PdD_(.67)H_(.02) and the PdD_(.67) do not show significant, difference within the limit of experimental error. Ultrasonic attenuations of the PdD_x(x=0.64-0.72) are decreased as the deutrium concentration increased.

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