Y掺杂Ti膜的吸放氢行为

Behavior of Hydrogen Absorption and Desorption in Y-doped Ti Films

合金化方法通常被用于改善储氢金属的力学性能,然而这往往会影响材料的储氢性能。为了研究Y掺杂对金属Ti吸放氢的影响,本工作从实验和模拟2方面研究了Ni/Ti-Y合金薄膜的吸放氢特性。采用直流磁控溅射方法制备不同Y掺杂含量的Ti-Y薄膜,并在表面镀一层Ni膜以减少表面污染。吸氘实验发现,Ti薄膜中氘(D)含量随着Y浓度的增加而增大,这是因为替位Y能够结合更多的D,且Y易与O结合可降低Ti被毒化的程度,有利于Ti吸D。密度泛函理论计算表明Y增强了与其相邻的Ti—H键能,同时产生了较强的Y—H键,导致紧邻Y的H结合能和扩散势垒增大,Ti-Y对H的束缚力增强;氘热释放实验结果显示Ni/Ti-Y体系的D解吸表观活化能高于纯Ni/Ti,说明Y对Ni/Ti-Y体系的氘脱附动力学产生了重要影响。结果表明Y掺杂对Ti薄膜体系的吸放氢性能都产生了一定程度的影响。

Alloying is often used to improve resistance to hydrogen-induced pulverization and cracking of hydrogen storage materials such as titanium and zirconium.However,it often affects the hydrogen storage performance of the material itself.Ti-Y alloys exhibit good mechanical properties,and they can effectively suppress hydrogen embrittlement.The properties of hydrogen absorption and desorption were investigated experimentally and theoretically in the present work.Y was uniformly doped into Ti films as a substitution atom using direct current magnetron sputtering.In addition,a Ni film of about 5 nm was subsequently deposited onto all sample surfaces to reduce surface contamination.Deuterium gas(D2)was used for hydrogen absorption experiment.Hydrogen absorption results show that the deuterium concentration in Ti-Y films increases with the increase of Y concentration.Combined with the density functional theory(DFT)calculation,the effects of Y doping on the hydrogen absorption properties of Ti could be summarized as follows:(1)the binding energy of Y to H calculated by DFT is stronger than that of Ti,thereby increasing the concentration of D absorbed;(2)Y has a strong affinity for O to form Y_(2)O_(3),which reduces O impurity concentration in Ti film and facilitates more D atoms to enter the Ti lattice to increase the amount of D absorption;(3)Y substitutes for the Ti atom to increase the binding energy of Ti—H adjacent to Y,making the D atom less likely to escape,and to reduce the diffusion barrier of D around Ti,which is distant from Y,making it easy for D to diffuse deeper into the sample.Therefore,the concentration of D absorbed in Ti samples increases with the increase of Y concentration.With regard to the properties of D desorbed in Ti-Y samples,the results show that the D desorption activation energy of the deuteride Ti-Y film could be increased by doping Y.The D desorption temperature is determined by the D thermal desorption kinetics of the Ni/Ti-Y film system,and Y doping may increase the apparent binding energy and diffusion activation energy for D of the overall Ti lattice.The surface potential barrier has an important effect on D desorbed from Ti.Furthermore,Y doping has a certain degree of influence on the hydrogen absorption and desorption performance of Ti thin films.