Sink property of metallic glass free surfaces

In Situ TEM Study of Radiation Resistance of Metallic Glass-Metal Core-Shell Nanocubes

Radiation damage can cause significantly more surface damage in metallic nanostructures than bulk materials. Structural changes from displacement damage compromise the performance of nanostructures in radiation environments such as nuclear reactors and outer space, or used in radiation therapy for biomedical treatments. As such, it is important to develop strategies to prevent this from occurring if nanostructures are to be incorporated into these applications. Here, in situ transmission electron microscope ion irradiation was used to investigate whether a metallic glass (MG) coating mitigates sputtering and morphological changes in metallic nanostructures. Dislocation-free Au nanocubes and Au nanocubes coated with a Ni-B MG were bombarded with 2.8 MeV Au⁴⁺ ions. The formation of internal defects in bare Au nanocubes was observed at a fluence of 7.5 × 10¹¹ ions/cm² (0.008 dpa), and morphological changes such as surface roughening, rounding of corners, and formation of nanofilaments began at 4 × 10¹² ions/cm² (0.04 dpa). In contrast, the Ni-B MG-coated Au nanocubes (Au@NiB) showed minimal morphological changes at a fluence of 1.9 × 10¹³ ions/cm² (0.2 dpa). The MG coating maintains its amorphous nature under all irradiation conditions investigated.

Atomistic evolution during the phase transition on a metastable single NaYF4:Yb,Er upconversion nanoparticle

The phase evolution of as-prepared NaYF4:Yb,Er upconversion nanoparticles (UCNPs) with a metastable cubic structure is studied based on in situ heating experiments via transmission electron microscopy (TEM). The atomistic behavior on the single NaYF4:Yb,Er UCNP is observed during the phase transition. The formation and evolution of voids on the NaYF4:Yb,Er UCNP appear at a temperature below 420 °C. Small circular voids are transformed at the initial stage to a large, hexagonal-pillar shaped single void. Two different routes to reach the stable α-phase from the metastable cubic structure are identified on a single NaYF4:Yb,Er UCNP. The first is via a stable β-phase and the second is a direct change via a liquid-like phase. The specific orientation relationships, [110]cubic//[11[Formula: see text]0]hexagonal and {002}cubic//{2[Formula: see text]00}hexagonal, between the cubic and hexagonal structures are confirmed. Additionally, a few extra-half planes terminated in the cubic structures are also observed at the cubic/hexagonal interface.