Morphology Dependence of Ag-Ni Solid Solubility

Abstract

Electrodeposition produced features with a dendritic morphology and features with a branched wire like morphology made up of about 20 nm sized particles. Both the features contained Ag and Ni atoms in a solid solution arrangement. However, the feature made up of nanoparticles contained a greater concentration of Ni as compared to the Ni content in the dendritic feature. The greater Ni content in the Ag-Ni solid solution for the features with nanoparticles when compared to the dendritic morphology features strongly indicated the effect of curvature in increasing the extent of miscibility between bulk immiscible atoms.Within the nano-size regimen, attributes related to the thermodynamic stability of phase(s) contained in a single component or multi-component isolated nano-sized particle change significantly with changes in both the size and the morphology of the particle. 1, 2 Stability of a phase(s) making up the volume of a nano-sized particle exposed to a certain temperature or pressure environment depends synergetically both on the size and the morphology of the particle. [3][4][5] The size-morphology interdependence is because of the fact that a change either in the nanoparticle's size or its morphology significantly modifies the nature of atomic coordination and chemistry of surfaces which consequently substantially changes the extent of energetic contribution from the system's surface towards its total free energy. As the minimization of the total free energy is the only criterion for phase stability, a change in the value of the total free energy decides the relative stability of the present phase(s) with respect to its continued existence or its transformation into any other possible phase(s) which provides for a lesser total free energy value. Therefore both the change in morphology and change in size are important variables to be considered in a comprehensive study designed towards investigating the stability of phases contained in a single component or multi-component nano-sized system. Consequently, both particle size and particle morphology provide the knobs to tune the functionalities that a nano-sized system can offer.One interesting effect of the system size-induced alteration in the bulk phase stability is the formation of novel alloys in the multicomponent nano-sized systems. These novel alloys are solid solutions consisting of component atoms that are immiscible in the bulk scale systems. [6][7][8][9] The bulk immiscibility of these component atoms stems from a large difference between their atomic sizes and a very high positive enthalpy of mixing into a solid solution structure. 10 Realization of miscibility leading to the formation of a solid solution structure is extremely relevant as these novel solid solution alloys can be technologically exploited. There are reports in the literature on the attainment of miscibility leading to the formation of solid solutions between bulk immiscible atoms coexisting in a nano-sized volume. Most of the published work however, emphasize only on the attainmen...

First principles study of bimetallic Ni13−nAgn nano-clusters (n = 0–13): Structural, mixing, electronic, and magnetic properties

“…[19,[36][37][38] The situation for the Ni-Ag nanoclusters is unfortunately confusing both from the point of view of experimental as well as theoretical studies, with some reports supporting core-shell like configuration following the general trend of M-NM binary clusters, [39][40][41][42] while others report formation of homogeneous alloy structure. [43][44][45][46][47]For example, global optimization of the NiAg nano clusters using some semi-empirical potentials with the tight-binding second moment approximation indicated poly-icosahedral structure of core-shell type for cluster sizes of 34 and 38 atoms. [48,49] On the other hand, the appearance of solid solution structured Ni-Ag nanoparticles, has also been discussed recently.…”

Compositionally Graded Microstructure for Ag-Fe Nanoparticles

“…For spherical nanoparticles, particle size provides thermodynamic stability to the solid solution phase due to the energetic contribution from the curvature [9,10]. Increase in the curvature enhances solid solubility in accordance with the Gibbs Thompson effect [9,10].…”

“…For spherical nanoparticles, particle size provides thermodynamic stability to the solid solution phase due to the energetic contribution from the curvature [9,10]. Increase in the curvature enhances solid solubility in accordance with the Gibbs Thompson effect [9,10]. Compositional dependence stems from the fact that energetic contribution from the positive enthalpy of mixing increases with composition achieving maximum value for the equi-atomic composition [11].…”

Ag-Ni Nanoparticles: Synthesis and Phase Stability

“…19 Additionally, it has been reported in the literature that electrodeposition route enables formation of highly supersaturated solid solutions leading to the formation of metastable alloys. [19][20][21] …”

“…There are several reports in the literature on the achievement of miscibility leading to the formation of a single phase solid solution alloy between bulk immiscible component atoms co-existing in an isolated nano-sized particle. [2][3][4][5][6] The diminished bulk immiscibility observed in nano-sized particles can be attributed to the (a) effect of high surface curvature which enhances the solid solubility through the Gibbs-Thompson effect 7,8 and (b) decrease in the driving force for the nucleation and growth of second phase within a nanosized particle. A second phase nucleation in a nano-sized particle can create an energetically unfavorable, highly strained, high specific surface area heterophase interface between bulk type equilibrium phases.…”