Metal Oxidation from Cu<sub>3</sub>Au and AgAu below their Critical Potentials

Pawlowych, A. R.; Pile, Donald; Pickering, H. W.; Weil, K. G.

doi:10.1524/zpch.1998.207.part_1_2.113

Cited by 4 publications

(17 citation statements)

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“…7,10,11,21,[27][28][29] There are now data suggesting that the product layer at the alloy surface is in a much different ͑lower density͒ state during dissolution than it is during recovery after cessation of the experiment, and that the two processes are associated with two different time scales. 19,25 Scanning tunneling microscopy ͑STM͒ 7,10,21 and transmission electron microscopy ͑TEM͒ 9 measurements by various authors support the long-held view that the alloy surface remains essentially planar during selective dissolution below E c . [1][2][3][4][5][6] The objective of this paper is to characterize the Au-rich product layer that forms during the selective dissolution of Cu from Cu-Au alloys at potentials below the critical potential.…”

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confidence: 72%

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Selective Dissolution below the Critical Potential and Back Alloying in Copper-Gold Alloy

Ateya

Geh

Carim

et al. 2002

J. Electrochem. Soc.

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Below the critical potential, E c , selective dissolution of Cu from Cu-18 atom % Au proceeds via Cu transport through an essentially planar Au-rich product layer, which over time increases to hundreds of atom layers in thickness. Transmission electron micrographs ͑TEM͒ taken after the selective dissolution ͑at E Ͻ E c ͒ and subsequent ͑current-off͒ back alloying processes reveal nearly uniform Moire ´patterns characteristic of the superposition of two layers with similar crystal structures, i.e., the Cu-depleted ͑Au-rich͒ product layer and the parent alloy. The Moire ´fringe spacing decreases with the time of Cu dissolution ͑for ϳ60 s͒, indicating solid-solution Au enrichment in the product layer during dissolution. The Moire ´patterns give no indication of discrete islands of residual Au. The decreasing Cu dissolution rate follows the parabolic law for the first 60 s with an effective diffusivity of Cu in the product layer of ϳ10 Ϫ13 cm 2 s Ϫ1 at 23°C. The TEMs also show a few pits, whose diameter is in the Ͻ10 nm range and whose number increases with time, which may account for the higher rate of Cu dissolution ͑than given by the parabolic law͒ after 1 min.

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confidence: 72%

“…17 On the other hand, the mechanisms that lead to selective dissolution from a planar surface below E c , and dealloying above E c , are the subject of considerable debate. [2][3][4][5][6][7][8][9][10][11][12]15,[18][19][20][21][22][23][24][25][26] The subject has been reviewed before [4][5][6] and is still attracting considerable attention.…”

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confidence: 99%

Selective Dissolution below the Critical Potential and Back Alloying in Copper-Gold Alloy

Ateya

Geh

Carim

et al. 2002

J. Electrochem. Soc.

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“…Thus, the shi can be attributed to the thermodynamic shi of Ag oxidation to more positive values according to eqn (4), due to the decreased activity of Ag in an alloy Ag 1Àx Au x (a ¼ 1 À x; 0 < x < 1) as compared to its activity in pure Ag (a ¼ 1). 18 The oxidative leaching of the Ag from the alloy continuously reduces the Ag content in the alloy, and hence successively increases x and the oxidation potential of Ag to form AgCl. The reduction of AgCl forms monometallic Ag entities on top of the bimetallic sample nanoparticles, as is visible from the increased oxidation peak at 0.15 V in the following cycle.…”

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confidence: 99%

“…), surface reorganization of the remaining B on the partially leached nanoparticle might additionally occur, causing a further broadening of the oxidation peak. 18,19 While electrochemical studies at ensembles of bimetallic nanoparticles enable the characterization of several billions of nanoparticles instantaneously, their individual size cannot be directly determined this way. Hence, electrochemical single entity studies of alloy particles are desirable to derive insights into both the size and the composition of individual bimetallic alloy nanoparticles.…”

Section: Ax(s)mentioning

confidence: 99%

Electrochemistry at single bimetallic nanoparticles – using nano impacts for sizing and compositional analysis of individual AgAu alloy nanoparticles

et al. 2016

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The increasing interest in producing bimetallic nanoparticles and utilizing them in modern technologies sets the demand for fast and affordable characterization of these materials. To date Scanning Transmission Electron Microscopy (STEM) coupled to energy dispersive X-ray spectroscopy is usually used to determine the size and composition of alloy nanoparticles, which is time-consuming and expensive. Here electrochemical single nanoparticle analysis is presented as an alternative approach to infer the particle size and composition of alloy nanoparticles, directly in a dispersion of these particles. As a proof of concept, 14 nm sized AgAu alloy nanoparticles are analyzed using a combination of chronoamperometric single nanoparticle analysis and cyclic voltammetry ensemble studies. It is demonstrated that the size, the alloying and the composition can all be inferred using this approach. Thus, the electrochemical characterization of single bimetallic alloy nanoparticles is suggested here as a powerful and convenient complement or alternative to TEM characterization of alloy nanoparticles.

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“…A time-dependent solid-solution enrichment process of the noble metal in this layer has previously been reported based on Auger spectroscopy of anodically dissolved CuAu (16) and CuPd (17) alloys below E c . During the selective dissolution process, the Au-enriched layer is less dense than the parent material (18,19). Thus the corrosion rate based not only upon the alloying elements but also the percent Au present in the alloy.…”

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confidence: 99%

Environmentally Induced Failure of Gold Jewelry Alloys

2005

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Stress corrosion cracking (SCC) is an established form of environmental attack in low karatage gold jewelry alloys. The cause of failure is often attributed to exposure to chlorinated solutions. At a certain gold content (usually greater than 14K) the alloy is widely believed protected from SCC. In this study, three commercial 18K gold alloys (yellow gold, nickel white gold, and palladium white gold) were tested in combination with three different household solutions to determine relative corrosion rates. These rates were determined using polarization tests. Once the maximum corrosion rate had been established, SCC tests using the constant potential dead weight method were used to determine time to failure. The resultant failure surfaces were examined to determine mode of fracture, which in all cases was predominantly intergranular. It was found that corrosion rates depended upon both the alloy system and the test solution. SCC was clearly demonstrated in 18K gold alloys, although in all cases times to failure were significantly greater than has been reported for lower karatage alloys. Palladium white gold was far more resistant to SCC than the other systems studied.

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Metal Oxidation from Cu₃Au and AgAu below their Critical Potentials

Cited by 4 publications

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Selective Dissolution below the Critical Potential and Back Alloying in Copper-Gold Alloy

Selective Dissolution below the Critical Potential and Back Alloying in Copper-Gold Alloy

Electrochemistry at single bimetallic nanoparticles – using nano impacts for sizing and compositional analysis of individual AgAu alloy nanoparticles

Environmentally Induced Failure of Gold Jewelry Alloys

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Metal Oxidation from Cu3Au and AgAu below their Critical Potentials

Cited by 4 publications

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Selective Dissolution below the Critical Potential and Back Alloying in Copper-Gold Alloy

Selective Dissolution below the Critical Potential and Back Alloying in Copper-Gold Alloy

Electrochemistry at single bimetallic nanoparticles – using nano impacts for sizing and compositional analysis of individual AgAu alloy nanoparticles

Environmentally Induced Failure of Gold Jewelry Alloys

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Metal Oxidation from Cu₃Au and AgAu below their Critical Potentials