Study On Deposition Behavior Of Deuterium In Palladium By D-D Nuclear Reaction

Palladium(Pd)is an important hydrogen storage material for its strong ability to absorb hydrogen.Palladium also plays an important role in the separation of hydrogen isotopes,which can be manufactured into membranes to separate hydrogen from impurities to obtain high purity hydrogen.Palladium can also be used as a hydrogenation catalyst to enhance its hydrogen storage properties in hydrogen storage materials.Therefore,it is of great significance to study the hydrogen-palladium interaction,i.e.,the deposition behavior(diffusion,adsorption/desorption and surface recombination behavior)of hydrogen isotopes in palladium.In this work,deuterium(D)ion beam has been implanted into palladium,and the dynamic and static concentration of deuterium has been studied by D-D nuclear reaction analysis.Firstly,the Pd foil has been implanted by 14-20 keV/D D+3 beams with high flux.The dynamic deuterium concentration in Pd can be obtained through the proton yield at saturation state with the proton yield unchanging with the fluence.Then,the 75 keV/D D+ beam with lower flux(~0.6 ?A)has been employed to analyze the static deuterium concentration after each implantation.Furthermore,a model has been established including the implantation,diffusion,adsorption/desorption and surface recombination behavior of deuterium in Pd.In this model,the dynamic deuterium concentration consists of free diffusing deuterium concentration CD,unsteadily trapped deuterium concentration CA,steadily trapped deuterium concentration CT,and the static deuterium concentration is CT.The depth profile and time evolution of deuterium concentration in Pd at different D energy have been analyzed based on the model.The results show:(1)The steadily trapped deuterium concentration CT has a saturation value(2.9±0.2)×1020 /cm3,its atom density ratio nD/nPd is(0.42 + 0.03)at.%.(2)The free diffusing deuterium concentration CD and unsteadily trapped deuterium CA reach dynamic balance state as the fluence is ~1017 /cm2,and the ratio of kA/kD is deduced to be about 1/600.This part of deuterium would decrease rapidly after the beam-injecting stopped.(3)In our experiment,the adsorption coefficient(kA),desorption coefficient(kD)are about 39s-1,6×10-2 s-1,respectively.In this work,the deuterium concentration in the self-absorption palladium target has been analyzed by the real-time D-D nuclear reaction,and the model can explain the experimental results very well.This method can also be used to study the deposition behavior of deuterium in other metal materials.