Atomic Structure and Structural Stability of Sc₇₅Fe₂₅ Nanoglasses

Abstract

Nanoglasses are solids consisting of nanometer-sized glassy regions connected by interfaces having a reduced density. We studied the structure of Sc(75)Fe(25) nanoglasses by electron microscopy, positron annihilation spectroscopy, and small-/wide-angle X-ray scattering. The positron annihilation spectroscopy measurements showed that the as-prepared nanoglasses consisted of 65 vol% glassy and 35 vol% interfacial regions. By applying temperature annealing to the nanoglasses and measuring in situ small-angle X-ray scattering, we observed that the width of the interfacial regions increased exponentially as a function of the annealing temperature. A quantitative fit to the small-angle X-ray scattering data using a Debye-Bueche random phase model gave a correlation length that is related to the sizes of the interfacial regions in the nanoglass. The correlation length was found to increase exponentially from 1.3 to 1.7 nm when the sample temperature was increased from 25 to 230 °C. Using simple approximations, we correlate this to an increase in the width of interfacial regions from 0.8 to 1.2 nm, while the volume fraction of interfacial regions increased from 31 to 44%. Using micro-compression measurements, we investigated the deformation behavior of ribbon glass and the corresponding nanoglass. While the nanoglass exhibited a remarkable plasticity even in the annealed state owing to the glass-glass interfaces, the corresponding ribbon glass was brittle. As this difference seems not limited to Sc(75)Fe(25) glasses, the reported result suggest that nanoglasses open the way to glasses with high ductility resulting from the nanometer sized microstructure.

Influence of grain size and composition, topology and excess free volume on the deformation behavior of Cu–Zr nanoglasses

“…Consequently, the NG exhibits a more homogeneous plastic deformation carried by a pattern of multiple shear bands [12] as compared to the bulk metallic glass (BMG), where plastic deformation is well localized in a few dominant shear bands. The influence of interfaces on the deformation behavior of nanoglasses has been shown both in computer simulation [11,13,14] and experiment [9,15], where also an enhanced plasticity under compression was observed indicating that not critical shear bands occur. Recent experiments on sputtered nanograined Au-based glasses also showed high hardness and a low elastic modulus as compared to their bulk counterparts [8].…”

“…The recent work of Chen et al [8], supports Gleiter's results on the structural model of a NG. The microstructure of a metallic nanoglass consisting of glassy grains and glass-glass interfaces has been experimentally revealed by electron microscopy, small-angle X-ray scattering and positron annihilation spectroscopy [9], while molecular dynamics studies showed that glass-glass interfaces exhibit an excess free volume and a modified local order [10,11].…”

Radial distribution function imaging by STEM diffraction: Phase mapping and analysis of heterogeneous nanostructured glasses

“…as in nanoglasses. The desire to explain their unusual structures and properties [15][16] [17] requires improved characterization methods.…”

Classical molecular dynamics and quantum ab-initio studies on lithium-intercalation in interconnected hollow spherical nano-spheres of amorphous silicon

“…The phenomenon of reduction in atomic density of amorphous materials when the particle size is reduced to nano-range was first discovered by Gleiter [23]. Classical molecular dynamics simulations on Cu-Ti [23] and CuZr [24] amorphous systems and experimental measurements in other systems like Sc-Fe [25] have revealed that the lowering in atomic density is due to diffusion of free volume from interfaces formed between glassy nano-particles.…”