Amorphization and thermal stability of aluminum-based nanoparticles prepared from the rapid cooling of nanodroplets: effect of iron addition

Abstract

Despite an intensive investigation on bimetallic nanoparticles, little attention has been paid to their amorphization in the past few decades. The study of amorphization on a nanoscale is of considerable significance for the preparation of amorphous nanoparticles and bulk metallic glass. Herein, we pursue the amorphization process of Al-based nanoparticles with classic molecular dynamics simulations and local structural analysis techniques. By a comparative study of the amorphization of pure Al and Fe-doped Al-based nanodroplets in the course of rapid cooling, we find that Fe addition plays a very important role in the vitrification of Al-based nanodroplets. Owing to the subsurface segregated Fe atoms with their nearest neighbors tending to form relatively stable icosahedral (ICO) clusters, the Fe-centred cluster network near the surface effectively suppresses the crystallization of droplets from surface nucleation and growth as the concentration of Fe attains a certain value. The glass formation ability of nanodroplets is suggested to be enhanced by the high intrinsic inner pressure as a result of small size and surface tension, combined with the dopant-inhibited surface nucleation. In addition, the effect of the size and the added concentration of nanoparticles on amorphization and the thermal stability of the amorphous nanoparticles are discussed. Our findings reveal the amorphization mechanism in Fe-doped Al-based nanoparticles and provide a theoretical guidance for the design of amorphous materials.

Chemical Ordering and Surface Segregation in Cu–Pt Nanoalloys: The Synergetic Roles in the Formation of Multishell Structures

“…In the present work, MAEAM potential was adopted to describe atomic bonding in Cu–Pt NAs because of their underpinnings in quantum mechanics, mathematic simplicity, and extendibility to alloy materials. The original EAM potential, , the modified one (MEAM), ,, and our MAEAM one − have already been successfully applied for the study of bulk, surface, and nanoparticles of metals and alloys through incorporating many-body interactions. In short, for a monometallic system, the original EAM represents the energy per atom as a sum of the pair interaction energy and the embedding energy .…”

“…In this perspective, we performed MC simulations with the modified analytical embedded atom method (MAEAM) potential − to unravel the roles of surface segregation and chemical ordering in determining the thermodynamically stable structure of Cu–Pt NAs. Parameters such as alloy composition, particle shape and size, and system temperature were correlated with surface Cu composition and the chemical ordering.…”

Isotropy‐Induced Stress Relaxation and Strong‐Tolerance for High‐Rate and Long‐Duration Sodium Storage by Amorphous Structure Engineering

“…Notably, the amorphous structure could be only obtained by the fast-cooling process, otherwise crystalline phase during the common-cooling procedure. Generally, crystalline energy can be suddenly dropped caused by a rapid cooling process, which inhibits the rearrangement of the atoms and results in the formation of a noncrystalline structure inherited from the molten state, [38,39] thus manifesting that this amorphization approach is controllable and facile. Furthermore, during the high-temperature sulfidation, the MOF would transform into the coating carbon and in situ wrap on the surface of GeS 2 , which could improve the conductivity of the entire electrode.…”

Synthesis of plasmonic Fe/Al nanoparticles in ionic liquids

“…33 In the case of iron aluminide NPs an additional fundamental problem of such a synthetic approach is the formation of stable iron-centered clusters even at low Fe concentration, which suppresses the nucleation process and thus, the growth of crystalline particles. 34 Therefore, even larger concentrations of Fe led to amorphous nanomaterials, which may be interesting in terms of catalysis but are much more difficult to analyze. 34 Dutta et al and Pithawalla et al, who described the wet-chemical synthesis of FeAl or Fe 3 AlC 0.5 nanoparticles by reducing anhydrous iron(II) chloride with lithium aluminum hydride, showed that a subsequent thermal treatment at temperatures of over 500 C is required for the crystallization of the initial amorphous material.…”

“…34 Therefore, even larger concentrations of Fe led to amorphous nanomaterials, which may be interesting in terms of catalysis but are much more difficult to analyze. 34 Dutta et al and Pithawalla et al, who described the wet-chemical synthesis of FeAl or Fe 3 AlC 0.5 nanoparticles by reducing anhydrous iron(II) chloride with lithium aluminum hydride, showed that a subsequent thermal treatment at temperatures of over 500 C is required for the crystallization of the initial amorphous material. 35,36 Therefore, ball-milling, as a top-down process, is the most reported way for the preparation of Fe/Al NPs.…”