Diffusion Coefficients and Phase Equilibria of the Cu-Zn Binary System Studied Using Diffusion Couples

Abstract

The diffusion behavior and phase equilibria in the Cu-Zn binary system were investigated using solidsolid and solid-liquid diffusion couples. Heat treatments at temperatures ranging from 100 to 750°C were performed and the samples were examined using optical microscopy, energy dispersive x-ray spectroscopy, and electron probe microanalysis to identify the phases and to obtain composition profiles. Solubility limits of both solid solution and intermetallic phases were then evaluated, and a forwardsimulation analysis (FSA) was applied to extract interdiffusion coefficients. The composition profiles from Hoxha et al. were also re-analyzed using FSA to obtain more reliable diffusion coefficient data without the assumption of constant diffusion coefficients for the intermetallic phases. A comprehensive assessment of the interdiffusion coefficients in three intermetallic phases of the Cu-Zn system was performed based on the results from the current study as well as those in the literature. Activation energies and Arrhenius pre-factors were evaluated for each phase as a function of composition. The fitted equations based on the comprehensive assessment have the capabilities of computing the interdiffusion coefficients of each of the phases at a given composition and temperature. Suggested modifications to the Cu-Zn binary phase diagram were presented based on the new experimental information gathered from the present study. A clear explanation is provided for the puzzling low Zn concentrations often observed in the Cu-rich fcc phase of Cu-Zn diffusion couples in comparison with the expected high solubility values based on the equilibrium Cu-Zn phase diagram.

Construction of Dynamic Alloy Interface for Uniform Li Deposition in Li-Metal Batteries

“…The alloy diffusion theory can be explained with Darken equation in a binary A-B alloy: [45] [46,47] Where A and B refer to Li and M (Ag, Au, Zn and Hg), respectively.D Li and D M are intrinsic diffusion coefficient of Li and M, and x Li andx M are concentration of Li and M in this study. For the Li-rich solid solution phase, it hasx Li -100% andx M -0, thus the above equation can be simplified as D =D M (M=Ag, Au, Zn or Hg).D M can be calculated according to the diffusion equation: [48,49] In which, R is the ideal gas constant (R =8.314 J mol -1 K -1 ), T is the room temperature (T =298 K), D 0 is the frequency factor of the atom and Q sd is the diffusion activation energy, respectively. D o andQ sd of Ag, Au, Zn and Hg atoms are shown inTable 1 , respectively.…”

Homogenizing Zn Deposition in Hierarchical Nanoporous Cu for a High‐Current, High Areal‐Capacity Zn Flow Battery

“…We selected open‐cell Cu foam as the substrate to start the fabrication of electrodes for two main reasons: i) unlike carbon, Cu is highly miscible with Zn in the bulk state, so these metals should wet each other at the interface; [ 49 ] and ii) Cu foam is a mature commercial product that is uniform, conductive, robust, and inexpensive, making it ideal for generalizing the synthesis method developed here to a broad scope of applications. The pristine Cu foam contains abundant open pores of hundred microns in size, which facilitate a rapid flow of electrolyte but limit the specific surface area necessary for high current and power.…”

“…Dt , where D is the diffusion coefficient (10 −15 -10 −16 m 2 s −1 ), [49] and t is the annealing time (10800 s). It is estimated to be 1.0-3.2 μm, slightly higher than that (≈600 nm) observed from the crosssectional microscopy on samples prepared by focused ion beams (FIBs) (Figure 1E), likely because the complex phase evolution between Cu and Zn can hardly be described with a single value of D and because the dealloying process usually leads to volume shrinkage.…”

Study of Reactive Diffusion in Cu/Zn Diffusion Couple

“…This suggests that the γ phase layer growth is dominantly due to diffusion of Cu atoms from Cu layer towards Zn layer. Cu and Zn composition profiles obtained from a Cu/Zn diffusion couple annealed at 300 • C for 28 hours have been given, indicating the positions of the different interfaces relative to the Matano plane (16) ; it shows that the displacement of the ε/γ interface relative to the Matano plane is larger than that of the γ/Cu interface. This phenomenon is clearly shown in Figure 2.…”

“…To identify the formed layers, EDX analysis was carried out in the SEM on the layers surface, at different points. According to a recent equilibrium phase diagram of the Cu-Zn system (16) , three inter metallic phases are stable at the studied temperature (250 • C): β , ε and γ. According to that equilibrium phase diagram, the ε and γ phases are stable for several chemical compositions around the stoichiometric ones (83,33 at % Zn) for ε and ( 61,53 at.% Zn) for γ.…”