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Microstructural Control of Mg_2Ni Hydrogen Absorbing Alloys by Rapid Solidification and Mechanical Grinding

快速凝固和机械研磨对Mg_2Ni吸氢合金的显微组织控制

基本信息

批准号：
09650757
负责人：
KAMADO Shigeharu
金额：
$ 1.79万
依托单位：
NAGAOKA UNIVERSIYT OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

In this study, for improvement in performance of batteries used in electric vehicles, we paid attention to Mg_2Ni protium absorbing alloy that has high protium absorption capacity, lightweight and low price as compared with the existing protium absorbing alloys. But Mg_2Ni alloy has high protium absorption and desorption temperature and slow hydriding kinetics that must be improved for practical purposes.Therefore, for the purpose of decreasing protium absorption and desorption temperature and improving protium absorption rate, we did a partial substitution of Mg_2Ni by third alloying elements. Mn, Fe, Co, Cu, Al, Zn and Ag which are expected to decrease the absolute value of hydride formation enthalpy of Mg_2Ni alloy were selected as third substitutional elements. The ternary alloys were also rapidly solidified, and mechanically ground in order to homogenize their microstructure. The microstructures of specimens obtained by these processes were observed and their protium absorbing and … More desorbing characteristics were investigated. Obtained results are summarized as followed ; (1) All activated specimens absorb protium at room temperature and their protium contents are higher than those of specimens before activation that causes new surface formation and an increase in reaction area. (2) Hydriding kinetics curves measurements show that rapidly solidified specimens of Mg_2Ni_<0.9>Co_<0.1> and Mg2Ni_<0.9>Fe_<0.1> alloys have the highest reaction rate. It is considered that Fe and Co substitution accelerated the diffusion of protium in these two alloys and rapid solidification cause the fine microstructure. (3) As the elapsed time after taking specimens out from hydrogen atmosphere increases, the protium desorption temperature decreases and desorbed protium contents increases. Microstmctural changes of the hydride from high temperature phase to low temperature phase probably causes this phenomenon. Similar results can be obtained when manually hydride of manually ground specimens after activation shows the same microstructural change, resulting in improvement of the desorption characteristics. (4) By addition of third alloying elements and Ni substitution, both activation energy and enthalpy for dehydriding decreases.From the above results, rapid solidification, mechanical grinding and substitution by 3d transition metals for Ni site in Mg_2Ni crystal structure are effective for improving the protium absorbing and desorbing characteristics of Mg_2Ni alloy. Less

本研究以提高电动汽车用蓄电池的性能为目标，重点研究了Mg_2Ni型吸质子合金，该合金具有吸质子容量高、重量轻、价格低廉等优点。但Mg_2Ni合金的吸、放氢温度高，吸、放氢动力学慢，在实际应用中还有待改进，因此，为了降低吸、放氢温度，提高吸、放氢速率，我们采用第三种合金元素对Mg_2Ni合金进行了部分替代。选择Mn、Fe、Co、Cu、Al、Zn和Ag作为第三代位元素，这些元素有望降低Mg_2Ni合金的氢化物生成焓绝对值。三元合金也快速凝固，并机械研磨，以均匀化其微观结构。观察了这些工艺制备的样品的显微结构，并对其吸氚和吸氚性能进行了分析。 ...更多信息研究了解吸特性。结果表明：（1）活化后的样品在室温下均能吸收氚，且其氚含量高于活化前，导致新表面的形成和反应面积的增加。(2)快速凝固Mg_2Ni_Co_3和Mg_2Ni_Fe_3合金的吸氢动力学曲线表明<0.9><0.1><0.9><0.1>，其吸氢速率最高。认为Fe和Co的替代促进了Pr在两种合金中的扩散，快速凝固导致了合金组织的细化。(3)随着试样从氢气氛中取出后时间的增加，脱附温度降低，脱附的氚含量增加。氢化物由高温相向低温相的微观结构变化可能是造成这种现象的原因。当手工研磨的样品在活化后的手工氢化物显示出相同的微观结构变化时，可以获得类似的结果，导致解吸特性的改善。(4)结果表明，快速凝固、机械研磨和用3d过渡金属取代Mg_2Ni晶体结构中的Ni位是改善Mg_2Ni合金吸放氢性能的有效措施。少