Browsing by Author "Yang, F"

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    Composition and temperature dependent structural investigation of perovskite-type sodium-ion solid electrolyte series Na1/2-xLa1/2-xSr2xZrO3
    (Australian Institute of Nuclear Science and Engineering (AINSE), 2020-11-11) Yang, F; Schmid, S; Peterson, VK
    The development of new solid electrolytes is becoming increasingly important, e.g. in rechargeable batteries for electric vehicles, where current organic electrolytes cause major safety concerns. The ABO3 perovskite metal oxides have shown excellent lithium and sodium ion conductivity owing to their stability and structural flexibility. This has led to the development of several perovskite-type solid electrolytes such as Li3xLa2/3- xTiO3 and Na1/2-xLa1/2-xSr2xZrO3, which have shown high ionic conductivity. The Na1/2-xLa1/2-xSr2xZrO3 perovskite-type sodium-ion solid electrolyte system was recently published by Zhao et al. [1] with the x=1/6 member, i.e. Na1/3La1/3Sr1/3ZrO3, found to have the highest ionic conductivity. The structure was reported to adopt a cubic crystal system with the space group P213. However, this is highly unlikely as both theoretical end members of the series, Na1/2La1/2ZrO3 and SrZrO3, have orthorhombic symmetry[2, 3]. Given the high ionic conductivity reported for the system, it is important to determine its structure reliable and with the best available data. Using neutron and X-ray powder diffraction data we have been able to confirm that the symmetry across the series is lowered to orthorhombic indeed. Variable temperature neutron powder diffraction data collected for the x=1/6 member of the system from room temperature to 1100 ◦C helped to identify a structural phase transition from orthorhombic to tetragonal symmetry at 800◦C. © The Authors.
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    Fracture and fatigue behaviour of a laser additive manufactured Zr-based bulk metallic glass
    (Elsevier, 2020-12) Best, JP; Ostergaard, HE; Li, BS; Stolpe, M; Yang, F; Nomoto, K; Hasib, MT; Muránsky, O; Busch, R; Li, XP; Kruzic, JJ
    Laser additive manufacturing of bulk metallic glass (BMG) provides an effective bypassing of the critical casting thickness constraints that limit the size of components that can be produced; however, open questions remain regarding the resulting mechanical properties. In this work, a Zr-based BMG known as AMZ4 with composition Zr59.3Cu28.8Nb1.5Al10.4 was printed using a laser powder bed fusion (LPBF) technique. Micro X-ray computed tomography results together with electron microscopy imaging revealed porous processing defects in LPBF produced AMZ4 that led to a loss in tensile strength. Fatigue crack growth studies revealed a fatigue threshold, ΔKth., of ∼1.33 MPa√m and a Paris law exponent of m = 1.14, which are relatively low values for metallic materials. A KIC fracture toughness of 24−29 MPa√m was found for the LPBF BMG samples, which is much lower than the KQ of 97−138 MPa√m and KJIC of 158−253 MPa√m measured for the cast alloy with the same composition. The lower fracture toughness of the laser processed AMZ4 was attributed to ∼7.5× higher dissolved oxygen in the structure when compared to the cast AMZ4. Despite the higher level of oxygen, the formation of oxide nanocrystals was not observed by transmission electron microscopy. Oxygen induced toughness loss was confirmed by dissolving elevated concentrations of oxygen into cast AMZ4 rods, which led to a reduction in bending ductility and changes in the short-range order of the glass structure, as revealed by synchrotron X-ray diffraction. © 2020 Elsevier B.V.