Thesis - Oztek_Muzaffer_T_200508_MA

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DSC 111 Heat Flow/mW 40 Exo Figure: Experiment:MTO LaNi5l 2nd dehydriding 20050318_5 Crucible:Steel Atmosphere:H2 19/03/2005 Procedure: dehydriding (Zone 1) Mass (mg): 271.9 Sample temperature/°C 140 20 0 120 -20 100 -40 80 -60 -80 60 -100 40 -120 -140 20 0 250 500 750 1000 1250 1500 1750 2000 2250 Time/s Figure 21: Thermogram for dehydriding of LaNi 5 starting with 1 atm. H 2 . 1.2 1.0 0.8 Wt. % H desorbed 0.6 0.4 0.2 0.0 0 200 400 600 800 1000 1200 1400 1600 1800 corrected time (s) Figure 22: Percent hydrogen desorbed plot for dehydriding of LaNi 5 . 54
Due to the fast kinetics observed at ambient temperatures, LaNi 5 was subjected to further analysis as a candidate material for hydrogen recovery from H 2 :He mixtures. The effects of the addition of aluminum by ball milling, as well as varying the preparation parameters, have been investigated and the results are presented in the following sections. 3.2. Aluminum in LaNi 5 3.2.1. Interaction With Pure Hydrogen The effect of partial substitution of nickel by aluminum in LaNi 5 for the purpose of altering the hydriding properties has been subject of many previous studies. From the macro perspective, lower H 2 pressure was needed to achieve the same H/M ratio as LaNi 5 alone. This observation is explained from the effect of Al on the crystal lattice expansion upon hydriding, which is a limiting factor to the process. Aluminum addition is reported to decrease the extent of expansion by decreasing the dislocation density and vacancy concentration upon hydriding. It also increases the lattice constants, resulting in more hydrogen being absorbed [58]. In the previous studies, LaNi 5-x Al x samples were reported to be prepared by arc melting the stoichiometric amounts of the components followed by size reduction by ball milling. In this study, aluminum was added to LaNi 5 via ball milling. Therefore, the Al content is presented as mole percentages, varying between approximately 0.9 and 33.3 % of the total number of atoms in LaNi 5 Al x . 55
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RECOVERY OF HYDROGEN AND HELIUM FRO
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ABSTRACT Waste streams of hydrogen
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I dedicate this work to my family m
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I also would like to cheer for my f
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2.2.2.1. Hydriding and Dehydriding
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LIST OF FIGURES Figure 1. Pressure-
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Figure 34. Pressure profiles under
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1. INTRODUCTION The focus of this s
Page 17 and 18: ecause of the difference in partial
Page 19 and 20: hydrides by dissolving large amount
Page 21 and 22: hydrogen storage alloy has a specif
Page 23 and 24: • Insensitivity to poisoning by i
Page 25 and 26: hydrogen capacity was not reproduci
Page 27 and 28: showed the lowest plateau pressure
Page 29 and 30: grain boundaries increases the tota
Page 31 and 32: These parameters are generally inte
Page 33 and 34: Figure 4. CaCu5-type P6/mmm structu
Page 35 and 36: In this study, the addition of Al t
Page 37 and 38: 2. EXPERIMENTAL 2.1.Chemicals and R
Page 39 and 40: Figure 5. The high energy Spex 8000
Page 41 and 42: 2.2.1.1. Hydriding and Dehydriding
Page 43 and 44: approximately 5 atm, and heating th
Page 45 and 46: determined by the start and end of
Page 47 and 48: 450 400 coating thickness (Å) 350
Page 49 and 50: 3. RESULTS AND DISCUSSIONS 3.1. Hyd
Page 51 and 52: DSC 111 heat flow/mW Exo 300 Figure
Page 53 and 54: The thermogram associated with the
Page 55 and 56: total time was broken into three 30
Page 57 and 58: The VTiNi sample was subjected to d
Page 59 and 60: solid solution of hydrogen rather t
Page 61 and 62: DSC 111 Heat Flow/mW 180 Exo Figure
Page 63 and 64: 100 rpm setting, the milling vial w
Page 65 and 66: BPR, 400 rpm, 5 minutes) did not re
Page 67: Table 1: Effects of various milling
Page 71 and 72: The mole % Al after milling was les
Page 73 and 74: Figure 24: Percent hydrogen capacit
Page 75 and 76: the start of the heating period, wh
Page 77 and 78: However, it was noted that the part
Page 79 and 80: percent hydrogen was decreased. The
Page 81 and 82: 3.2.2.4. AuPd and Pt Coating on LaN
Page 83 and 84: 1.0 0.8 (a) (b) Wt. % H absorbed 0.
Page 85 and 86: After dehydriding by the sample, th
Page 87 and 88: 19 18 P (atm) 17 16 15 14 0.74 %Al
Page 89 and 90: GC output, arbitrary units 0 5 10 1
Page 91 and 92: sample was LaNi 5 . This may indica
Page 93 and 94: 30 min. 15 min. Intensity (arb. uni
Page 95 and 96: After milling the percentages of Al
Page 97 and 98: 4. CONCLUSIONS This study has been
Page 99 and 100: 16. Van-Vucht, J.H.N., Kuijpers, F.
Page 101 and 102: 47. Suryanarayana, C., Progress in
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Thesis - Oztek_Muzaffer_T_200508_MA

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