首页|Deep insight of unique phase transition behaviors and mechanism in Zr2Co-H isotope system with ultra-low equilibrium pressure
Deep insight of unique phase transition behaviors and mechanism in Zr2Co-H isotope system with ultra-low equilibrium pressure
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Efficient capture,safe storage and release of tri-tium from the international thermonuclear experimental reactor(ITER)reaction exhaust gas is a perplexing problem,and the development of an efficient tritium-getter material with ultra-low hydrogenation equilibrium pressure is con-sidered as a reliable way.In this work,Zr2Co alloy was selected as a tritium-getter material and prepared through induction levitation melting.Fundamental performance test results show that Zr2Co exhibits an ultra-low hydrogenation equilibrium pressure of 3.22 × 10-6 Pa at 25 ℃ and excellent hydriding kinetics under a low hydrogen pressure of 0.005 MPa.Interestingly,unique phase transition behaviors were presented in Zr2Co-H system.Specifically,Zr2CoH5 formed by Zr2Co hydrogenated at room tempera-ture is initially decomposed into ZrH2 and ZrCoH3 at 200 ℃.With the temperature increasing to 350 ℃,ZrCoH3 is dehydrogenated to ZrCo,and then ZrCo further reacts with ZrH2 at 650 ℃ to reform Zr2Co and hydrogen.Among the staged phase transition pathways during dehydrogenation,the decomposition of Zr2CoH5 occurs preferentially,which is well accordance with both the smallest reaction energy barrier and the maximum reaction spontaneity that are determined respectively from kinetics activation energy and thermodynamics Gibbs free energy.Furthermore,first principles calculation results indicate that the stronger binding of hydrogen in interstitial environments of ZrCoH3 and ZrH2 triggers the hydrogen-stabilized phase transfor-mation of Zr2CoH5.The unique phase transition mecha-nisms in Zr2Co-H system can shed light on the further exploration and regulation of analogous staged phase tran-sition of hydrogen storage materials.
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