NSRRC Activity Report 2022

080 NSRRC ACTIVITY REPORT 2022 lower and narrower working temperature range. Many R x M y compounds exhibit considerably lower CTE values and slightly lower and narrower working temperature ranges than those of invar, as shown in Fig. 1(b) . ZTFC exhibits isotropic thermal expansion characteristics that originate from its cubic crystal structure ( Fig. 1(c) ). The high durability and stability of ZTFC are indicated by nearly unchanged ∆ l / l 0 values after cyclic thermal shock and soaking in 3.5 wt% NaCl solution for 14 days ( Figs. 1(d) and 1(e) ). The superior environmental stability of ZTFC compared with that of invar can be immediately identified by soaking ingots in simulated seawater. As shown in Fig. 2(a) , ZTFC remained bright with a metallic luster after soaking in NaCl solution for more than 2 weeks, whereas invar became rusty within several days. The rust dissolved in the NaCl solution is reflected in mass loss. ZTFC lost eight times less mass than invar did due to corrosion. Figures 2(c) and 2(d) show the higher environmental stability indicated by a highly noble OCP, −0.12 V, and a slow dissolution rate during the test. The potentiodynamic polarization (PDP) curve of ZTFC exhibits a broader range of gradual incline (voltage ≈ −0.4 to 0 V), which indicates the existence of a stable passive film on the surface of the ZTFC. The existence of this passive film was further confirmed with various experimental tools and was proposed to be the reason for ZTFC’s high corrosion resistance. Xing and coworkers suggest that Zr/Ta substitution not only modulates thermal expansion behavior through the indirect modification of Fe/Co magnetic moments but also improves corrosion Fig. 2 : Environmental stability of ZTFC and related alloys. (a) Photographs of ZTFC and invar alloys immersed in a 3.5 wt% NaCl solution for different durations. (b) Weight loss of ZTFC, stainless invar, and invar alloys during immersion. Electrochemical tests of samples: (c) open-circuit potential (OCP) curve and (d) potentiodynamic polarization (PDP) curve. [Reproduced from Ref. 4] resistance by causing the spontaneous formation of passive films of their amorphous oxides. (Reported by Chin-Wei Wang) This report features the work of Xianran Xing and his collaborators published in Adv. Mater. 34 , 2109592 (2022). ANSTO WOMBAT – High-intensity Powder Diffractometer • NPD • Materials Science, Condensed-matter Physics References 1. Y. Cao, K. Lin, Z. Liu, J. Hu, C.-W. Wang, X. Liu, E. Tereshi- na-Chitrova, K. Kato, Q. Li, J. Deng, J. Chen, H. Zhang, X. Xing, Inorg. Chem. 59 , 5247 (2020). 2. Y. Cao, K. Lin, Z. Liu, J. Hu, C.-W. Wang, E. Tereshina-Chi- trova, K. Kato, Q. Li, J. Deng, J. Chen, H. Zhang, X. Xing, Inorg. Chem. 59 , 11228 (2020). 3. Y. Cao, K. Lin, S. Khmelevskyi, M. Avdeev, K. M. Taddei, Q. Zhang, Q. Huang, Q. Li, K. Kato, C. C. Tang, A. Gibbs, C.-W. Wang, J. Deng, J. Chen, H. Zhang, X. Xing, Phys. Rev. Lett. 127 , 055501 (2021). 4. W. Li, K. Lin, Y. Yan, C. Yu, Y. Cao, X. Chen, C.-W. Wang, K. Kato, Y. Chen, K. An, Q. Zhang, L. Gu, Q. Li, J. Deng, X. Xing, Adv. Mater. 34 , 2109592 (2022).