A Study on Phase Transformation of Na3AlH6 Complex Metal Hydride

  • 楊 明峰

Student thesis: Master's Thesis


Abstract Sodium tetrahydro aluminate is the most discovered in complex metal hydride family The advantage in reversibility and dehydrogenation amount exceed 5 5 wt% from that targeted by D O E for on-board light-duty vehicle utilization makes it a popular candidate among all of complex metal hydride In this study as-received NaAlH4 was used and directly heated in thermogravimetric analysis (TGA) to see the quantity of Hydrogen that released from pure NaAlH4 isothermally and how the results relate to the transformation of sodium tetrahydro aluminate into sodium hexahydro aluminate In order to support the observation of this transformation ex-situ XRD was used for structure and composition analysis of the reacted sodium tetrahydro aluminate in TGA This study was also done by the help of in-situ synchrotron X-ray diffraction We found out that the quantity of hydrogen gas generated from sodium tetrahydro aluminate is increased as the holding time and temperature increases The result also showed the difference effect of the tetrahydro aluminate compound for its dehydrogenation amount by the variation of the heating rate Where at lower heating rate the quantity of gases that spill out are much more than the higher one Moreover this study found out ?- Na3AlH6 to ?- Na3AlH6 phase transformation taken place at temperature near the first dehydrogenation stage (210 °C) far lower than the result from literature [31] and also was taken place earlier (220 – 240 oC) than the one which was reported in literatures In the in-situ XRD result the appearance of ?- Na3AlH6 could be found out at 220 230 and 240 °C isothermally However the trace of this phase could only be detected in the middle of cooling process
Date of Award2015 Aug 11
Original languageEnglish
SupervisorWen-Ta Tsai (Supervisor)

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