Distribution Coefficients of Impurities in Metals

Pearce, J. V.

doi:10.1007/s10765-014-1585-5

Cited by 28 publications

(17 citation statements)

References 27 publications

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“…The International Temperature Scale of 1990 (ITS-90) is based upon a number of "fixed point" temperatures, mostly corresponding to the defined melting temperatures of pure metallic elements. One difficulty encountered in the practical realisation of these fixed points, and in standard platinum resistance thermometer calibrations [16] , arises from the fact that impurities dissolved in each pure metal, at the level of parts per million, often cause an elevation or depression of the melting temperature of the order of millikelvin.…”

Section: Realising the International Temperature Scale Of 1990mentioning

confidence: 99%

“…MTDATA has been used, along with thermodynamic databases for alloys including SGTE solution database, NPL Aluminium database and the SOLDERS database (created through the COST531 project), to calculate k values for more than 170 binary systems, covering the fixed point metals Hg, Ga, In, Sn, Zn, Al, Au, Ag and Cu with likely impurities [16] . The results have been compared with experimental measurements.…”

Section: Realising the International Temperature Scale Of 1990mentioning

confidence: 99%

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MTDATA and the Prediction of Phase Equilibria in Oxide Systems: 30 Years of Industrial Collaboration

Gisby

Taskinen

Pihlasalo

et al. 2016

Metall Mater Trans B

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Section: Realising the International Temperature Scale Of 1990mentioning

confidence: 99%

Section: Realising the International Temperature Scale Of 1990mentioning

confidence: 99%

MTDATA and the Prediction of Phase Equilibria in Oxide Systems: 30 Years of Industrial Collaboration

Gisby

Taskinen

Pihlasalo

et al. 2016

Metall Mater Trans B

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“…In the previous study at the silver freezing temperature [15], a similar negative melting slope was reported and attributed to the dissolved oxygen in the sample. Thus, similarly to the case of silver, during melting of the oxidized sample, it was suspected that the oxygen trapped at the grain boundaries or in small cavities in the solid sample (oxygen is insoluble in solid tin [16]) was progressively released and decreased the melting temperature. However, the mechanism for how the increasing oxygen concentration in a molten sample affected the melting temperature, which is determined by the local impurity concentration of the solid phase, is uncertain and necessitates further study on the effect of oxidation on the melting behavior of tin using a sample which is intentionally oxidized in a controlled manner.…”

Section: Resultsmentioning

confidence: 99%

Carbothermal reduction of oxidized tin and recovery of deep supercool

2018

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Deep supercooling of tin is a characteristic sign of a high-purity sample having fewer nucleation sites. However, due to the risk of oxidation during the cell fabrication (especially during the initial sample filling process), oxidized tin can be present in the sample, which manifests itself as a nucleation agent and significantly affects the realization of the freezing temperature of tin. In this work, the effect of the oxidation of high-purity tin (nominally 99.9999% pure) and an effective means of reducing the oxidized sample were investigated. We fabricated an open-type tin freezing point cell using 1.15 kg of high purity tin shot, which was poured into the crucible in air, giving rise to a high risk of oxidation. The oxidized tin sample showed abnormally small supercools of about 0.1 °C which were caused by additional nucleation sites introduced by the oxidation. The oxidized sample also exhibited a melting temperature inversion over the entire range of the melting with a temperature depression of about 1.9 mK. The oxidized sample was carbothermally reduced by melting the sample in its graphite crucible and holding at a temperature of 750 °C for a total duration of 365 h. The carbothermal reduction of the oxidized sample caused the satisfactory recovery of the deep supercool, and the recovered supercool was about 10.6 °C after about 100 h of reduction, and 10.7 °C after 365 h of reduction. At the end of the reduction process, the melting curve inversion was significantly alleviated, having 0.1 mK temperature depression over less than 10% of the melting range. Importantly, the carbothermal reduction at 750 °C was found to be an effective means of removing the oxide nucleation sites and of recovering the characteristic deep supercool of tin.

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“…This software can calculate the equilibrium state at a fixed temperature and pressure. The most stable state has the lowest Gibbs free energy [9].…”

Section: Methodsmentioning

confidence: 99%

“…The SIE method is recommended by the Consultative Committee for Thermometry to correct the effect of impurities on the realisation of fixed points [4]. Recently, great progress has been made in characterising the liquidus slopes for a wide range of binary alloys relevant to ITS-90 fixed points [1,9]. However, two distinct challenges remain: the first is the accuracy and traceability of sufficiently sensitive chemical assays capable of detecting the very small concentration of impurities; and the second is the limited knowledge of the effect of impurity oxides formed [4].…”

Section: Introductionmentioning

confidence: 99%

Effect of oxygen on trace impurities in extremely pure metal ingots used for realising ITS-90 fixed point temperatures

Chowdhury

Pearce

2023

J. Phys.: Conf. Ser.

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The International Temperature Scale of 1990 (ITS-90) provides a scheme for calibrating thermometers which is largely based on the freezing points of pure metals such as indium, tin, zinc, aluminium and silver. The existence of trace impurities in pure metals results in uncertainties in the realization of these freezing points. Several methods such as the sum of individual estimates (SIE) and overall maximum estimate (OME) are used to assess the uncertainties due to the presence of impurities. However, it is becoming evident that the oxidation of impurities results in their precipitation, which means that these insoluble oxides no longer play a significant role in the elevation or depression of the freezing temperature. Hence the conventional correction techniques may overestimate the magnitude of the effect. In this study, the thermodynamic modelling software MTDATA was used to evaluate the effect of oxygen on selected impurities in In, Sn, Zn, Al and Ag by calculating the binary impurity-metal phase diagram in the presence of specific amounts of oxygen. It was found that oxygen has a significant effect on many of the systems studied. The most significant effect was observed in the Ag system, and then, in decreasing order of significance, In, Sn, Zn and Al.

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Distribution Coefficients of Impurities in Metals

Cited by 28 publications

References 27 publications

MTDATA and the Prediction of Phase Equilibria in Oxide Systems: 30 Years of Industrial Collaboration

MTDATA and the Prediction of Phase Equilibria in Oxide Systems: 30 Years of Industrial Collaboration

Carbothermal reduction of oxidized tin and recovery of deep supercool

Effect of oxygen on trace impurities in extremely pure metal ingots used for realising ITS-90 fixed point temperatures

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