Mg-Nd/Ni储氢合金微观组织及吸放氢动力学

Microstructure and de-/absorption kinetics of Mg-Nd/Ni alloys

采用熔剂保护法制备了不同Nd含量的Mg-Nd二元及Mg-Nd-Ni三元储氢合金,通过高能球磨对铸态合金进行组织细化,制备镁基纳米复合储氢颗粒,采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、自动Sievert设备(PCT)及差示扫描量热仪(DSC)等系统研究了Ni、Nd添加及活化过程中氢压对合金微观组织及吸放氢动力学的影响。结果表明:Ni、Nd含量会影响球磨后合金的颗粒尺寸,Mg12Nd与H反应生成的NdH3会稳定存在,NdH3明显促进Mg的吸氢,而Mg2Ni明显改善MgH2的放氢。活化过程中超高的氢压可明显细化第二相颗粒,在3 MPa氢压下活化后,合金中NdH3相的颗粒尺寸在50~200 nm之间,而在8 MPa氢压下活化后,NdH3的颗粒尺寸在10 nm左右。相较于在3 MPa氢压下活化的合金颗粒,在8 MPa氢压下活化后样品的吸放氢速率得到明显改善。

Mg-Nd binary and Mg-Nd-Ni ternary alloys with different Nd contents were prepared in graphite crucible under the protection of covering agent.High energy ball-milling was performed to obtain Mg-based nanocomposite hydrogen storage materials.The phase components,microstructure and hydrogen storage properties were systematically investigated by XRD,SEM,TEM,PCT and DSC.The results show that the contents of Ni and Nd influence the particle size of ball milled samples.Mg2Ni significantly favors desorption process,while NdH3 is more conducive to absorption.Ultrahigh hydrogen pressure during activation process can refine the microstructure of Mg alloys.The particle size of NdH3 is in the range of 50−200 nm for Mg-15Nd alloy activated under 3 MPa hydrogen pressure,while it is about 10 nm for Mg-15Nd alloy activated under 8 MPa hydrogen pressure.The sample activated under 8 MPa hydrogen pressure shows superior absorption and desorption kinetics than that activated under 3 MPa hydrogen pressure.