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(a) The high energy x-ray penetrated through the whole sample to reveal the overall structural information. (b) Through-thickness measurements were conducted with a step size of from the surface to the center region with an incident x-ray beam parallel to the charging surface.
Vickers hardness of as a function of the charging time. The hardness significantly increased after hydrogen charging for the first 12 h and gradually saturated at HV335.
XRD pattern of the (a) as-cast and (b) hydrogen-charged specimen with the measuring geometry shown in Fig. 1(a). The (c) was obtained by integrating over all azimuthal angles of the 2D diffraction image in (a) and (b).
The diffraction intensity that originated from the crystalline phases was extracted by subtracting the pattern at the surface area from the pattern in the center area of the charged sample. The curve was compared to the ICDD database to identify possible hydride phases, and the results showed that these sharp diffraction peaks most likely belonged to a tetragonal cerium/lanthanum hydride (, Ln denotes for La and Ce).
Through-thickness XRD pattern of the 36 h charged . E denotes the edge (charging surface area), and CEN denotes the center of the specimen. The diffraction geometry is showed in Fig. 1(c).
A comparison of the reduced pair-distribution functions, G(r), of as-cast specimen, hydrogen-charged specimen, the difference and the theoretical PDF of the crystalline cerium/lanthanum hydride, . The changes in G(r) after hydrogenation are similar to the G(r) of crystalline . Due to the similarity of La and Ce, the resulting hydride phase is believed to be a tetragonal Ln-based hydride (LnHx, where , and Ln denotes for La and Ce).
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