High-pressure synthesis of amorphous MgNi(1.02)H(2.2).
High-pressure synthesis of amorphous MgNi(1.02)H(2.2).
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DOI：
10.1021/ja010170r
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发表时间：
2001-06
影响因子：
15
通讯作者：
J. Chen;T. Sakai;N. Kitamura;H. Takeshita;N. Kuriyama
中科院分区：
文献类型：
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作者：
J. Chen;T. Sakai;N. Kitamura;H. Takeshita;N. Kuriyama
储氢材料的使用对于清洁电动汽车系统的应用是一个有吸引力的主张。这一领域最重要的成就之一将是创造具有高容量和低解吸-吸收温度的轻质储氢材料。2、3在不同的储氢材料中，镁镍基金属氧化物由于其高容量和相对较低的成本而成为可逆储氢的有希望的候选者。4已知在Mg-Ni系的相图中，形成两种金属间化合物：Mg 2Ni和MgNi 2。5在最高温度350 ℃和最高压力4 MPa的范围内，Mg 2Ni容易与氢反应生成Mg 2NiH 4，而MgNi 2不与氢反应。6这些条件限制了它们的实际应用，因为在前一种情况下解吸温度高，而在后一种情况下氢含量低。近年来，人们一直致力于通过元素替代、7、8球磨、9-11和高压处理等技术来改善Mg-Ni基合金的吸放氢性能。12，13这些结果表明，氢化行为发生了很大变化，主要是由于形成了无定形相或/和纳米晶。然而，由于Mg-Ni系统仍然不成熟，需要开发不太稳定的合金。目前，通过使用可达到吉帕（GPa）的高压技术，可以成功合成新的石墨烯。更重要的是，高氢压技术在许多金属氢系统中的应用已经给出了进一步吸收氢的明确证据，可以预期氢的各种新特性。16在这里，我们报告了一个有趣的发现，均匀的氢化物相MgNi 1。02H2在充有氩气的手套箱中，将摩尔比为1：1的MgH_2和Ni的混合粉末（e30 μm）在6 GPa的压力下加热，1压制成颗粒，并与内部氢源LiAlH 4一起放入氯化钠坩埚中，所述内部氢源在热分解后提供氢。样品和LiAlH 4通过氮化硼盘分离，该氮化硼盘仅允许氢自由扩散，因此保护样品免受污染。17将NaCl容器用石墨加热器包围并置于八面体叶蜡石中，八面体叶蜡石是边缘尺寸为20 mm的压力传递介质。通过使用具有多砧装置的UHP-2000油机进行热处理18加热后，将样品在液氮中淬火，产生作为深灰色粉末的新相。
The use of hydrogen storage materials is an attractive proposition for applications in clean electric vehicle systems. 1 One of the most important achievements in this area would be the creation of lightweight hydrogen storage materials with high capacity and low desorption-absorption temperatures. 2, 3 Among the different hydrogen storage materials, magnesium-nickel-based metal hydrides are promising candidates for reversible hydrogen storage because of their high capacity and relatively low cost. 4 It is known that in the phase diagram of the Mg-Ni system, two intermetallic compounds are formed: Mg2Ni and MgNi2. 5 Within the limits of a maximum temperature of 350 C and a maximum pressure of 4 MPa, Mg2Ni reacts readily with hydrogen to form Mg2NiH4, whereas MgNi2 does not react with hydrogen. 6 These conditions limit their practical utilization in view of the high desorption temperature in the former case, and the small content of hydrogen in the latter. Recent effort has been devoted to improving the hydriding and dehydriding properties of Mg-Ni based alloys using techniques such as element substitution, 7, 8 ball-milling, 9-11 and high-pressure treatment. 12, 13 These results showed that the hydrogenation behavior was greatly changed, mainly due to the formation of amorphous phases or/and nanocrystallines. However, since the Mg-Ni system is still premature, less stable hydrides need to be developed. At present, new hydrides can be successfully synthesized by using high-pressure technology that can reach gigapascals (GPa). 14, 15 More importantly, the application of the high hydrogen pressure techniques to a number of metalhydrogen systems has given clear evidence of further absorption of hydrogen, of which various novel properties can be expected. 16 Here we report an interesting finding that the homogeneous hydride phase MgNi1. 02H2. 2, which was synthesized by heating a stoichiometric mixture of 2MgH2+ Ni at a pressure of 6 GPa, can desorb-absorb hydrogen reversibly in the temperature range 80-200 C.In a glovebox filled with pure argon gas, a powder mixture (e30 μm) of MgH2 and Ni having a molar ratio of 1: 1 was pressed into pellets and put into a sodium chloride crucible together with the internal hydrogen source LiAlH4, which supplied hydrogen after heat-decomposition. The sample and LiAlH4 were separated by a boron nitride disk, which only allowed hydrogen to diffuse freely and therefore protected the sample from pollution. 17 The NaCl container was surrounded by a graphite heater and placed in an octahedral pyrophyllite, a pressure transmitting medium with an edge size of 20 mm. Heat treatments were carried out by using an UHP-2000 oil machine with a multi-anvil device (tungsten carbide) at 6 GPa and 600 C for 90 min. 18 After heating, the sample was quenched in liquid nitrogen, yielding the new phase as a dark-gray powder.