摘要
采用熔体快淬法制备了(Mg70.6Ni29.4)90Nd10的非晶贮氢合金带,用X射线衍射仪和高分辨电镜对该合金在充放电循环过程中的组织结构演变进行了动态跟踪。结果表明:非晶(Mg70.6Ni29.4)90Nd10贮氢合金在充放电循环过程中经过4个循环以后开始晶化,首先生成平均颗粒尺寸为5 nm左右的NdMg2Ni9相,经过6个循环以后开始出现Mg2Ni相,到第20个循环后,生成了稳定的Mg2Ni,α-Mg和Nd2H5相。这表明初生相NdMg2Ni9在充放电循环过程中逐渐转化为Mg2Ni,α-Mg和Nd2H5相。经过热力学计算进一步验证表明,非晶(Mg70.6Ni29.4)90Nd10合金在晶化过程中首先形成NdMg2Ni9相,因为它的自由能(ΔG=-15.2789 kJ.mol-1,T=300 K)与Mg-Ni相(ΔG=-8.2694 kJ.mol-1,T=300 K)和Mg-Nd相(ΔG=-13.29503 kJ.mol-1,T=300 K)相比是最低的。
Amorphous Mg-based hydrogen-storage alloy（Mg70.6Ni29.4）90Nd10 was prepared by melt-spinning.The phase structures of the ribbons before and after charge/discharge cycling were characterized by high-resolution transmission electron microscopy（HRTEM） and X-ray diffraction（XRD） analysis,respectively.It was found that the amorphous structure began to crystallize after four cycles of hydrogenation/ dehydrogenation and a new nano-crystallized phase NdMg2Ni9 was detected with average grain size in the range 5 nm.The nano-size Mg2Ni phases appeared after 6-10 cycles,and the stable Mg2Ni,α-Mg and Nd2H5 phases were present after 20 cycles of charging/discharging.That indicated that the NdMg2Ni9 phase formed at the beginning,also gradually decomposed into Mg2Ni,α-Mg and Nd2H5 phases as hydrogenation/dehydrogenation proceeded.The following results of thermodynamics calculation verified that the nano-crystallized phase NdMg2Ni9 was present firstly during the process of crystallization,because its free-energy（ΔG=-15.2789 kJ·mol-1,T=300 K） was the lowest among Mg-Ni phase（ΔG=-8.2694 kJ·mol-1,T=300 K） and Mg-Nd phase（ΔG=-13.29503 kJ·mol-1,T=300 K）.
出处
《中国稀土学报》
CAS
CSCD
北大核心
2010年第5期575-581,共7页
Journal of the Chinese Society of Rare Earths
基金
国家973前期专项重点项目(2007CCA04800)
山东省博士基金(BS2009CL039)资助
关键词
Mg-Ni-Nd系贮氢合金
微观结构
热力学
非晶
稀土
Mg-Ni-Nd hydrogen-storage alloy
microstructure
thermodynamics
amorphous alloy
rare earths
