Ag-Ni Nanoparticles: Synthesis and Phase Stability

Abstract

The present study provides an electrodeposition based synthesis method for producing solid solution structured Ag-Ni nanoparticles. It was also observed that the room temperature stable solid solution configuration for the electrodeposited Ag-Ni nanoparticle was a kinetically frozen atomic arrangement and not a thermodynamically stable structure as upon annealing of the Ag-Ni nanoparticles in the ambient atmosphere the solid solution structure decomposed producing phases that were oxides of Ag and Ni.In the case of bulk there exists a limitation with respect to the formation of a system with microstructure made up of a single phase solid solution alloy between two component element atoms with a large difference in atomic sizes and a positive enthalpy of mixing. This phenomenon is commonly referred as the 'miscibility gap'. 1 A miscibility gap can occur only if the component metals are chemically similar and crystallize in the same lattice form. Microstructure of a bi-metallic system with nominal compositions lying inside the miscibility gap region of the equilibrium phase diagram for that particular binary system is commonly composed of two distinct structurally similar but compositionally different phases. 1 In these phases, alternately one of the component element atoms forms the solute and the other forms the solvent. 1 Miscibility gap thus restricts the realization of many potentially technologically useful single phase alloys with a particular composition that can be formed from the combination of component element atoms with a large difference in atomic sizes. Interestingly, in the recent years it has been shown by several researches that the bulk miscibility gap can be diminished in nano-sized systems. 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. 2-6 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. Realization of solid solubility between bulk immiscible atoms confined in a nano-sized volume has the potential of producing various novel alloy materials. Such a phenomenon would initiate several scientific and technological research endeavors focused on the structural and functional investigation of these novel alloy materials as a function of the size and composition of nanosized systems that houses these single phase alloys.In bulk, silver-nickel system shows negligible miscibility upto very high temperatures. 9 This immiscibility is primarily due to a 14 % difference in ...

Electrodeposition Approaches to Deposit the Single-Phase Solid Solution of Ag-Ni Alloy

“…As it is obvious from the phase diagram that Ag and Ni are mutually insoluble, even at 400°C, the solubility of Ni in Ag is only ~0.0219 at% [12]. The reasons of the high immiscibility of Ag and Ni alloying elements are (a) the large difference in their atomic sizes (~14%) and (b) a positive enthalpy of mixing (∆H mix for solid solution equiatomic Ag-Ni alloy is 23 kJ/mol) [13,14]. However, an enhancement of miscibility between Ag and Ni atoms in nano-size level to form a nano-size system has been achieved by researchers [8][9][10][11].…”

“…However, an enhancement of miscibility between Ag and Ni atoms in nano-size level to form a nano-size system has been achieved by researchers [8][9][10][11]. Enhancement of miscibility of atoms of nanoparticles of Ag and Ni can be attributed to (a) the effect of increase of particles curvatures with the reduction of their sizes that facilitate miscibility in accordance with the Gibbs-Thomson effect and (b) the decrease of the driving force for the nucleation and growth of the second phase within a nano-sized particle [13].…”

“…The electrodeposition method has established itself as a most suitable method for synthesis of single-phase Ag-Ni alloy films due to its time efficiency, cost-effectiveness, and ability to mass production of single-phase solid solutions [13,[20][21][22][23][24][25][26]. In the electrodeposition process, the apparatus used for the deposition of the film is less complicated than the vacuum-based methods such as molecular beam epitaxy or sputtering.…”

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

“…[48,49] On the other hand, the appearance of solid solution structured Ni-Ag nanoparticles, has also been discussed recently. [50] In the present work, we aim on shedding light to this confusing situation through DFT based electronic structure calculations. In particular, we have studied the equilibrium structures, energetics, alloying versus segregation behavior and magnetic properties of the Ni 13−n Ag n clusters, with n = 0−13.…”

3D computer model of the Ag-Cu-Ni <i>T-x-y</i> diagram: verification of sections in the atlas of phase diagrams for lead-free soldering

“…[27] были зафиксированы кластеры со структурой «ядро-оболочка» (ядро и оболочка обогащены соответственно атомами никеля и серебра), а в 2012 г. [28][29] наличие структур «ядро-оболочка» ставится под сомнение, но во всем концентрационном интервале зафиксированы непрерывные ряды твердых растворов (в отличие от двухфазной области в традиционной диаграмме (см. рис.…”