The mechanism of anti-disproportionation for Ti-doped ZrCo alloys

Abstract

For the disproportionation mechanism of ZrCo alloy, the unstable occupation of H atoms to 8e sites was considered to be the driving force of hydrogen-induced disproportionation reaction in ZrCo alloys. Titanium metal (Ti) is employed as one of the candidates for improving ZrCo alloys by element substitution. In this paper, the anti-disproportionation mechanism of Ti-doped ZrCo alloys with a large-scale proportional element doping, has been studied in detail by combining experimental results and calculations. The thermodynamic properties and anti-disproportionation properties of Zr1-xTixCo (X = 0–0.5) alloys were investigated by sievert methods. Taking in view the known Case 1 which states that H(4c2) atoms diffuse into the 8e sites and Case 2 based on a new assumption involving the extra occupation of H(8e) atoms, the occupying effect of H(8e) atoms of different Zr1-xTixCoH3 (X = 0–0.5) and the property of 4c2 sites as the source of H(8e) atoms were analyzed by Density functional theory. The results indicated that the occupancy of H(8e) atoms and the bond length of Zr-H(8e) are decisive factors affecting the anti-disproportionation performance of ZrCo alloys, and the influence of Ti substitution on the H(8e) occupancy mainly originates from the (8e-4c2) barrier.