الفهرس 
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Abstract
Different approaches for storing hydrogen are investigated as compressed hydrogen tanks, liquefied hydrogen and more recently solid state hydrogen storage materials, the later has gained more attention ion the last few years.
One of the most interesting candidates as a solid state hydrogen storage material lithium alanate (LiAlH4). Due to its high hydrogen content 10.5 wt% LiAlH4 gained more attention.
Dry reaction applied to LiAlH4 by ball-mill technique in order to be dehydrogenated has been focused and widely used.
Ball-milling lithium alanate even by low or high energy ball-mill results in hydrogenation of the tetrahedral form of lithium alanate (LiAlH4) into octahedral form (Li3AlH6) releasing significant amount of hydrogen.
Throughout this work it was found that:
Ball-milling LiAlH4 in the presence of LiH and Ti-metal as a catalyst using low energy ball-mill in an inert atmosphere results in
1- Decreasing in the crystal size as time of ball-milling increased in case of Ti-metal, while in case of LiH after 120 hours of milling agglomeration occurred and the crystal size increased after observed decreasing after 72 hours of milling.
2- Ti-metal reveals good diffusion on the surface of as-received LiAlH4 as well as good catalytic activity.
3- Transformation from tetrahedral form into octahedral form with significant amount of hydrogen released is achieved in all cases and proved by several techniques.
4- Thermal stability of all samples is investigated, clearly two hydrogenation steps are observed upon heating indicating releasing of hydrogen occurs in two separated reactions. Long time ball-milling mainly deteriorates thermal stability of the samples.
5- The presence of Ti-metal as a catalyst along with ball-milling enhances the kinetics of as-received LiAlH4, all thermochemical events are shifted to lower temperatures.
6- The activation energy of as-received LiAlH4 is calculated to be 102 kj/mol for the decomposition of LiAlH4 into Li3AlH6, Al and H2 (first decomposition step), and 110 kj/mol for decomposition of Li3AlH6 into LiH, Al and H2 (second decomposition step). After ball-milling with LiH these values are shifted to lower values since the activation energy of the first step of dehydrogenation is found to be 92.11 kj/mol, while that for second step is 104 kj/mol.
7- After ball-milling with Ti-metal the activation energy of the first decomposition step is calculated to be 92.12 kj/mol, while that of second decomposition step 105 kj/mol.
8- Pressure-composition-temperature isotherm illustrates the dehydrogenation as a function of temperature for as-received LiAlH4 and after milling with Ti-metal and LiH. The as-received LiAlH4 starts decomposition at 1270C releasing about 2 wt% of hydrogen corresponding to LiAlH4 decomposition.
9- Addition of Ti-metal as a catalyst and ball-milling the reaction mixture for 5 hours results in more enhancement to the reaction kinetics since the first decomposition step starts at nearly 110 0C releasing 3 wt% of hydrogen, further milling up to 35 hours lowers the first decomposition step to 100 0C.
10- Reacting LiAlH4 with LiH and milling for 72 hours the first dehydrogenation step starts at 117 0C releasing 2.3 wt%, while further milling up to 120 hours results in more desorped hydrogen ( 4.2 wt%) and less kinetics since the first dehydrogenation step starts at 1050C.
11- At hydrogen pressure less than 5 bar there is considerable hydrogenation kinetics in all cases these kinetics well-enhanced by the presence of Ti-metal and also by long time ball-milling in all cases.
12- Finally, the LiH and Ti-doped LiAlH4 reveals measured enthalpy of 70.5 kj/mol of H2 and this value is lower than the value recorded for pure LiAlH4 85.2 kj/mol of H2.