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The thermogram associated with the subsequent dehydriding of the alloy<br />
exhibited an endothermic event, ascribed to the loss of hydrogen from the alloy, at an<br />
onset temperature of approximately 230 ºC. The amount of hydrogen released was<br />
limited to 0.15% at 250 ºC, which was not sufficiently hot for complete dehydriding. The<br />
sample was dehydrided again and 3% H was released at about 350 ºC. The thermogram<br />
and the percent hydrogen desorbed plots are given in Figures 11 and 12. In the<br />
thermogram, the endothermic peak is followed by two smaller exotherms. The exotherms<br />
are due to the re-absorption of the released hydrogen. This re-absorption occurs as the<br />
temperature decreases during the cooldown cycle.<br />
DSC 111<br />
Heat Flow/mW<br />
Exo<br />
100<br />
Figure: Experiment:Tonguc Mg2Ni 2nd dehydriding 20040520_3 Crucible:Steel<br />
Atmosphere:H2<br />
20/05/2004 Procedure: hydriding (Zone 1)<br />
Mass (mg): 109.5<br />
Sample temperature/°C<br />
350<br />
50<br />
300<br />
250<br />
0<br />
200<br />
-50<br />
150<br />
-100<br />
100<br />
-150<br />
50<br />
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500<br />
Time/s<br />
Figure 11: Thermogram for dehydriding of Mg 2 Ni.<br />
39
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