Ammonia Desorption Property and Structural Changes of LiAl(NH2)4 on Thermal Decomposition

详细信息    查看全文

• 作者：Taisuke Ono ; Keiji Shimoda ; Masami Tsubota ; Shinji Kohara ; Takayuki Ichikawa ; Ken-ichi Kojima ; Masataka Tansho ; Tadashi Shimizu ; Yoshitsugu Kojima
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：May 26, 2011
• 年：2011
• 卷：115
• 期：20
• 页码：10284-10291
• 全文大小：969K
• 年卷期：v.115,no.20(May 26, 2011)
• ISSN：1932-7455

文摘

A composite material of LiAl(NH₂)₄ and LiH irreversibly releases H₂ gas by 6.1 mass% below 130 掳C. The H₂ desorption mechanism of the composite has been proposed, but it is still controversial because the decomposition mechanism of LiAl(NH₂)₄ is not well-known. We here examined the gas desorption property of LiAl(NH₂)₄ by using thermogravimetry and mass spectroscopy. On heating to 160 掳C, a large amount of NH₃ release was observed, which was followed by mild gas emission until 500 掳C. We investigated the detailed structural changes on the NH₃ gas desorption by using synchrotron X-ray total scattering, infrared spectroscopy, and nuclear magnetic resonance spectroscopy. On the basis of these structural analyses, we obtained strong evidence that the amorphous intermediate product described as LiAl(NH₂)_x(NH)_yN_z was formed during the thermal decomposition process, where the AlN₄ network polymerization proceeds and the ratio of [NH₂]^{鈭?/sup>, [NH]2鈥?/sup>, and [N]3鈥?/sup> units gradually changes with releasing NH₃ gas. Finally, the crystalline Li₃AlN₂ and the amorphous residue, which will become AlN with longer annealing, were formed because of the complete exhaustion of hydrogen atoms by NH₃ desorption.}