Sink property of metallic glass free surfaces

Abstract

When heated to a temperature close to glass transition temperature, metallic glasses (MGs) begin to crystallize. Under deformation or particle irradiation, crystallization occurs at even lower temperatures. Hence, phase instability represents an application limit for MGs. Here, we report that MG membranes of a few nanometers thickness exhibit properties different from their bulk MG counterparts. The study uses in situ transmission electron microscopy with concurrent heavy ion irradiation and annealing to observe crystallization behaviors of MGs. For relatively thick membranes, ion irradiations introduce excessive free volumes and thus induce nanocrystal formation at a temperature linearly decreasing with increasing ion fluences. For ultra-thin membranes, however, the critical temperature to initiate crystallization is about 100 K higher than the bulk glass transition temperature. Molecular dynamics simulations indicate that this effect is due to the sink property of the surfaces which can effectively remove excessive free volumes. These findings suggest that nanostructured MGs having a higher surface to volume ratio are expected to have higher crystallization resistance, which could pave new paths for materials applications in harsh environments requiring higher stabilities.

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

“…Post-irradiation bright-field TEM images and diffraction patterns show that the MG shell remains amorphous (Figure E,F). Irradiation-induced nanocrystal formation has been observed in various bulk MGs. − Enhanced atomic mobility due to the increase in free volume during irradiation is thought to drive crystallization. , For thin, <15 nm, MG films, it has previously been observed that the excess free volume formed by irradiation is rapidly annihilated at the free surface, which prevents changes in atomic mobility and nanocrystal formation . This may also occur in the Au@NiB nanocubes inhibiting crystallization.…”

“…41,42 For thin, <15 nm, MG films, it has previously been observed that the excess free volume formed by irradiation is rapidly annihilated at the free surface, which prevents changes in atomic mobility and nanocrystal formation. 45 This may also occur in the Au@NiB nanocubes inhibiting crystallization.…”

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

“…), as described above. In addition, the change of the contrast in the TEM images could be caused by the rearrangement of the lattice defects by thermal activation 29,30 . In actuality, the polygonal-shaped contrast in the α-phase NaYF 4 :Yb,Er UCNPs is not explained by the pure electron-beam effect.…”

Anisotropic Lattice Distortions in Biogenic Minerals Originated from Strong Atomic Interactions at Organic/Inorganic Interfaces

“…[79,80] The latter are rather stiff, but even proteins being natively soft in a free state become much more rigid under deformation in confinement. [81,82] In any case, the organic/inorganic interactions in biocomposites will lead to much larger deformation of the more compliant organic substance than that of a mineral.…”