Thesis - Oztek_Muzaffer_T_200508_MA

In this study, the addition of Al to the LaNi 5 system was performed by
mechanically alloying the LaNi 5 with Al using a flat bottom tungsten carbide vial in a
Spex 8000 Mixer Mill. The mole percent of Al in LaNi 5 was varied from 0.87% to
48.57% corresponding to LaNi 5 Al 0.05 → 5.67 .
LaNi 5 itself has been previously verified to be potentially used at the Kennedy
Space Center for recovery of boil-off hydrogen [61]. The main objective of the study
described in this thesis was the evaluation of LaNi 5 and LaNi 5 Al x for the separation of H 2
from its mixtures with He. First, hydrogen uptake capacity and rates of the materials from
pure H 2 were determined and compared to the published results. Then behavior of the
materials when exposed to a mixture of H 2 and He at different pressures was determined
using the same experimental setup and presented. The amount and state of Al in the
samples were correlated to the H 2 uptake capacity and rates, for both pure H 2 and H 2 -He
mixtures.
To improve the behavior of LaNi 5 and LaNi 5 Al x with H 2 -He mixtures, the
samples were coated with AuPd, which is known to be very permeable to hydrogen.
These sampes were analyzed with the same procedure and the results are described in
section 3.2.2.4.
The materials were characterized using X-ray diffractometry, which gave
information about crystal structure and formation of new compounds by ball milling. Due
to the possibility of segregation of elements during ball milling and sticking permanently
on the milling media, the elemental composition of the samples was not expected to be
the same before and after ball milling. Therefore, it was crucial to determine the exact
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