Synthesis of novel hydrogen-storage materials, low-Z ternary hydrides, using supercritical fluid hydrogen

本研究已完成用于临时光元素（低Z）氢化物，最近已经支付了作为新的氢存储材料的注意。我们已经探索了一种新的高密度低Z氢在高压（HP）和高温（HT）条件下的合成和观察反应过程使用外热的钻石-砧-细胞。特别是，我们针对一种新型的低氢氢化物的合成是一种类似LiBeH_3的新型低氢的合成，它是非常难生产的，使用超临界流体。作为对LiBeH_3的合成进行了标记， HP Raman散射在反应产品中提出了一种新的氢化物的合成，在LiH和Be之间进行了处理，其中在7 GPa和300·C的氢中进行了处理。没有差异峰值是从使用HP X射线差异（XRD）的产品中观察到的。更高的压力/温度条件可以保证LiH + Be的反应，并使产品在晶体中得到改善。作为相关研究， HP非典型BeH_2、LiBH_4、LiALH_4和NaAlH_4使用HP XRD、拉曼散射、红外吸收和Brillouin散射测量方法进行了测试。正如表示相似的BeH_2，BeH_2分子的聚合物被建议约50 GPa。LiBH_4在1、16和30 GPa的某些HP相位上被转化为HP XRD的结构。30 GPa以上的结构与NaBH_4在环境压力下的结构相同，并揭示了HP下的铝合金-金属borohydrides的结构序列。在两个花生、LiALH_4和NaAlH_4的情况下，一些HP转换被观察到，但由于他们展示了广泛的XRD模式，这是很难分析结构的。However，值得注意的是，NaAlH_4的新HP/HT阶段的生产低于13 GPa和280的条件。It suggests that HP/HT conditions even below 300·C have the potential to produce various kinds of novel interesting phases in the low-Z hydrides already known。

This study has been accomplished for ternary light-element (low-Z) hydrides, which have been paid attention to as new hydrogen-storage materials recently. We have explored synthesis of a new high-density low-Z hydride under high-pressure (HP) and high-temperature (HT) conditions and observation of the reaction process using an outer-heated diamond-anvil- cell. Especially, we aimed at the synthesis a novel low-Z hydride like LiBeH_3, which is quite difficult to be produced, using with supercritical fluid of hydrogen.As regarding the synthesis of LiBeH_3, HP Raman scattering suggested a synthesis of a new hydride in a reaction product between LiH and Be, which has been treated in hydrogen of 7 GPa and 300・C. However, no diffraction peak was observed from the product using HP x-ray diffraction (XRD). Higher pressure/temperature conditions may promote the reaction of LiH + Be and to make the product improved in crystallinity.As related studies, HP behaviors of amorphous BeH_2, LiBH_4, LiALH_4, and NaAlH_4 have been examined using HP XRD, Raman scattering, infrared absorption and Brillouin scattering measurements. As regards amorphous BeH_2, the polymerization of BeH_2 molecules was suggested at about 50 GPa. LiBH_4 was transformed to some HP phases at 1, 16 and 30 GPa and the structures of the HP phases were analyzed by means of HP XRD. The structure above 30GPa was the same with the structure of NaBH_4 at ambient pressure, which revealed the structural sequence of alkali-metal borohydrides under HP. In the case of the two alanates, LiALH_4 and NaAlH_4, some HP transformations were observed but it was difficult to analyze the structures because they showed broad XRD patterns. However, it is worthy to note that a new HP/HT phase of NaAlH_4 was produced under the conditions of 13 GPa and 280・C. It suggests that HP/HT conditions even below 300・C have the potential to produce various kinds of novel interesting phases in the low-Z hydrides already known.