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Metallic glasses (MGs) are known to exhibit a nanoscale heterogeneous structure that consists of a weakly bonded region (WBR) and a strongly bonded region (SBR), but its characterization is not yet fully understood. This study investigates the structural heterogeneity of Zr- and Pd-based MGs using a dynamic viscoelastic model. Volume fraction (V) and elastic modulus (Ec) are independently derived from the model to characterize each region. In addition, the structural heterogeneity is evaluated using χ = VEc,WBR/VEc,total. As a result, the strong Zr-based MG is estimated to own approximately 28% of VWBR, approximately 87% of Ec,WBR/Ec,SBR, and χ ∼ 0.241. On the other hand, the fragile Pd-based MG is estimated to own approximately 26% of VWBR, approximately 70% of Ec,WBR/Ec,SBR, and χ ∼ 0.208. Furthermore, a comparison of χ, fragility, and Poisson's ratio shows that as χ increases, fragility decreases and Poisson's ratio increases. Notably, the diversification of constituent elements is inversely related to χ, fragility, and Poisson's ratio in the Zr- and Pd-based MGs. Thus, the existing understanding of the structural heterogeneity inherent in MGs is updated using the constructed dynamic viscoelastic model in this study. [ABSTRACT FROM AUTHOR]

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In this paper, a thin calcium phosphate layer was prepared on the surface of TiZrCuPd bulk metallic glasses (BMGs). All samples were dipped in HNO aqueous solution and boiled in 1.2 mol·L NaOH aqueous solution. After the two preliminary treatment steps, they were soaked in simulated body fluid (SBF) to form an apatite layer on the surface. After immersion for 12 days, a coating composed mainly of Ca-P particles was rapidly deposited on the surface of TiZrCuPd bulk metallic glasses. The surfaces of chemically treated samples and the samples after immersion in SBF were characterized by X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and energy dispersive spectroscopy (EDS). Analysis results indicate that this apatite coating consists of Ca-P particles with different diameters. In addition, the Ca/P ratio of the apatite coatings immersed for 14 days is 1.62, which is close to that of hydroxyapatite (HA). [ABSTRACT FROM AUTHOR]

Abstract: A carbonate hydroxyapatite (HA)–collagen (Col) composite coating on NiTi shape memory alloy (SMA) was synthesized by biomimetic growth in modified simulated body fluid (MSBF), which containing high Ca and P ions concentrations. The morphology of composite coating was uniform and porous. The major phase of coating, identified by Infrared Spectroscopy (IR) and X-ray diffraction (XRD), was HA with B-type carbonate substitution. It was also proved by IR results that the collagen was present in the coating. Transmission Electron Microscopy (TEM) and high resolution TEM analysis showed that the c-axis of HA crystals aligned parallel to the longitudinal direction of the collagen fibrils. The relative orientation maintained in the composite coating may benefit the NiTi SMA to achieve better properties in hard tissue replacement. [Copyright &y& Elsevier]