Gold, Gold Alloys, and Gold Compounds

Renner, H.; Schlamp, Günther; Hollmann, Dieter; Lüschow, H. M.; Tews, Peter; Rothaut, J.; Dermann, K; Knödler, Alfons; Hecht, Christian; Schlott, M.; Drieselmann, Ralf; Peter, C. John; Schiele, R.

doi:10.1002/14356007.a12_499

Cited by 20 publications

(31 citation statements)

References 62 publications

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“…2 This has been a common industrial practice for jewelry applications for nearly half a century. [19][20][21] In this case, a configuration of 9 MT-nn fcc grains reproducing the six fivefold symmetry axes of the icosahedron was found.…”

Section: Introductionmentioning

confidence: 73%

Thermodynamic Aspects of Homogeneous Nucleation Enhanced by Icosahedral Short Range Order in Liquid Fcc-Type Alloys

Rappaz

Kurtuldu

2015

JOM

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We have recently shown that minute solute element additions to liquid metallic alloys can strongly influence the nucleation of the fcc phase and act as a grain refinement method. Electron back-scattered diffraction observations revealed a concomitant increase in the percentage of nearest neighbor (nn) grains that are in a twin relationship. Furthermore, multiple-twinned (MT) nn grain configurations with a fivefold symmetry around a common h110i direction have been identified, an occurrence that can be explained when the symmetry of the icosahedron is accounted for. It was then conjectured that a new nucleation mechanism occurs in two steps: first, the formation of small icosahedral quasicrystals in the melt, followed by heteroepitaxy of the fcc phase on facets of these quasicrystals. In the present contribution, based on thermodynamics arguments, it is proposed that the first step occurs by spinodal decomposition of the liquid, in a manner similar to Guinier-Preston zones formation in solid state precipitation, while the second step is a transformation of these quasicrystal precursors into MT-fcc nanocrystals once the driving force for this transformation is sufficient to overcome the fcc-liquid interfacial energy and the elastic strains associated with MT-fcc nanoparticles. This explanation sets up guidelines for finding solute elements and composition ranges that favor this grain refinement mechanism.

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Section: Introductionmentioning

confidence: 73%

Thermodynamic Aspects of Homogeneous Nucleation Enhanced by Icosahedral Short Range Order in Liquid Fcc-Type Alloys

Rappaz

Kurtuldu

2015

JOM

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“…The electrodeposition of gold is a very broad subject because, being the final layer, many variations are required to optimize both the appearance and the composition [88,89]. The gold finishing is employed in a large number of fields due both to its electrical and anti-corrosion properties, as well as its aesthetical properties.…”

Section: Goldmentioning

confidence: 99%

Electroplating for Decorative Applications: Recent Trends in Research and Development

et al. 2018

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Electroplating processes are widely employed in industrial environments for a large variety of metallic coatings, ranging from technological to decorative applications. Even if the galvanic electrodeposition is certainly a mature technology, new concepts, novel applications, environmental legislation and the new material requirements for next-generation devices make the scientific research in this field still very active. This review focuses mostly at the decorative and wearable applications, and aims to create a bridge between the past knowledge and the future direction that this process, i.e., electrodeposition, is taking. Both the theoretical fundamentals as well as some of the most widespread practical applications-limited to metallic and alloy coatings-are explored. As an integral part of the industrial process, we take a look at the main techniques thought which the quality control of deposits and surfaces is carried out. Finally, global industrial performance and research directions towards sustainable solutions are highlighted.

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“…It might be assumed, with some confidence, that no high‐purity copper or silver was used for the gold alloys; hence, the trace element patterns of the gold deposits may be affected by the impurities of the copper or silver used for alloying (for the composition of contemporary copper, see Klein and von Kaenel 2000). An additional problem may result from the surface enrichment of the precious metals due to corrosion, etching or cleaning as often reported (Leuser 1949; Schatz 1957; North 1987; Renner and Johns 1989 and references therein). Condamin and Picon (1965) observed those problems for Roman denarii.…”

Section: Introductionmentioning

confidence: 96%

An Assessment of Osmium Isotope Ratios as a New Tool to Determine the Provenance of Gold with Platinum‐Group Metal Inclusions*

Junk

Pernicka

2003

Archaeometry

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The sudden increase in the amount of Celtic gold coins circulating in central Europe during the second century BC coincides with the appearance of platinum-group mineral (PGM) inclusions in the Celtic gold. It has been proposed that large amounts of gold were introduced from the eastern Mediterranean by mercenaries following the conquest by Alexander the Great, but another hypothesis might be the discovery of entirely new gold sources in central Europe during this time. The presence of PGM inclusions in gold objects is usually taken as an indication for an origin from placer deposits (Hartmann 1970; Park 1986). Initially, it was hoped that those inclusions could be characteristic for a certain deposit, but Meeks and Tite (1980) have shown that the compositional variation within a single gold object can be as large as the total variation observed in all investigated gold artefacts. Therefore, the elemental composition of the PGMs in gold artefacts does not provide any reliable information on the provenance of the gold.An alternative to chemical analysis of the inclusions is the determination of their osmium isotope ratios. Similarly to lead, osmium exhibits a variable isotopic composition due to the radioactive decay of 187 Re and 190 Pt. In order to investigate the potential of this new geochemical tool to determine the provenance of ancient gold, a quasi-non-destructive method for the determination of Os isotope ratios with LA-MC-ICP-MS has been developed.The results show that different types of deposits can be distinguished by Os isotope patterns and their distributions when applying a simple descriptive statistical method. In contrast to lead isotope ratios, the variations of Os isotope abundances are rather large in many ore deposits. But, also contrary to lead, the heterogeneity of the Os isotope ratios of the deposits is preserved in the artefacts, because the analysed PGMs are not dissolved during melting of the gold. Therefore, it is feasible to distinguish between different types of gold sources and to define specific deposits provided that the artefact contains several PGMs. The application of this new technique to Celtic gold coins from southern Germany and coins from western Anatolia has been demonstrated in this study.

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Gold, Gold Alloys, and Gold Compounds

Abstract: The article contains sections titled: 1. History 1.1. Centers of Gold Production … Show more

Cited by 20 publications

References 62 publications

Thermodynamic Aspects of Homogeneous Nucleation Enhanced by Icosahedral Short Range Order in Liquid Fcc-Type Alloys

Thermodynamic Aspects of Homogeneous Nucleation Enhanced by Icosahedral Short Range Order in Liquid Fcc-Type Alloys

Electroplating for Decorative Applications: Recent Trends in Research and Development

An Assessment of Osmium Isotope Ratios as a New Tool to Determine the Provenance of Gold with Platinum‐Group Metal Inclusions*

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