No 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...

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 ...

The gold nanostructures find several technological applications in MEMS, optoelectronics, and electronics industries. To enhance the applicability and suitability of the gold nanostructures in these fields, modification of the morphology of the deposited nanostructure is required. In recent years, the electrodeposition method has emerged as a widely known method for the deposition of the nanostructures of different dimensions and morphologies due to its time efficiency, costeffectiveness, and absence of vacuum technology. In this method, the morphology of the deposited gold nanostructure can also be easily controlled by tuning the electrodeposition process parameters such as electrolyte concentration, electrolyte temperature, current density, deposition time, etc. This chapter gives a detailed overview of the crucial electrodeposition parameters affecting the morphology of the gold nanostructures deposits.

Owing to a large difference in atomic sizes and a positive enthalpy of mixing, Ag and Ni form an immiscible system. In the current work, we report on the electrodeposition of Ag-Ni nanoparticles with a solid solution structure. Effect of current on the relative changes in composition and sizes of solid solution nanoparticles is illustrated. It is shown that with increase in the deposition current, size of Ag-Ni nanoparticles decreases due to an increased nucleation rate. With decrease in size the extent of miscibility of Ni in Ag increases due to increased energetic contribution from the particle curvature.