Thermometry's dependence on chemical metrology: a needs-based assessment

Hill, Kathryn; Rudtsch, Steffen

doi:10.1088/0026-1394/42/1/l01

Cited by 26 publications

(30 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This includes careful investigations by different methods and proof of the homogeneity of each specific batch of a material. This advises the investigation and certification of larger batches of materials which would be made available to all NMIs, as suggested in [10].…”

Section: Quantification Approaches For Gd-msmentioning

confidence: 99%

High-Purity Fixed Points of the ITS-90 with Traceable Analysis of Impurity Contents

et al. 2008

View full text Add to dashboard Cite

The International Temperature Scale of 1990 (ITS-90) is based on thermodynamic equilibrium states of ideally pure substances. The largest contribution to the uncertainty budgets of most metallic fixed points is the influence of impurities on the fixed-point temperature. Therefore, a traceable chemical analysis of the remaining impurities with small uncertainty is the basis of further progress. Further requirements are better knowledge of the phase diagrams at very low impurity contents, impurity segregation, and the quantification and correction of thermal effects during a fixedpoint realization. In this article, current and future activities at PTB and BAM in order to develop improved metallic fixed-point cells of the ITS-90 are reviewed.

show abstract

Section: Quantification Approaches For Gd-msmentioning

confidence: 99%

High-Purity Fixed Points of the ITS-90 with Traceable Analysis of Impurity Contents

et al. 2008

View full text Add to dashboard Cite

show abstract

“…To some extent, these issues are still controversial and the solution is not trivial [1][2][3]. In order to understand and quantify these additional sources of uncertainty, thermal measurements alone are insufficient; it is essential to carry out chemical metrology measurements to quantify the impurity concentrations and isotopic composition [4,5]. In this work, we have characterized the concentrations of metallic impurities and the isotopic compositions of two mercury samples obtained by vacuum distillation of a high-purity mercury sample obtained from the Almaden mine.…”

Section: Introductionmentioning

confidence: 99%

Assembly and Study of Different Mercury Cells with Known Impurity Content and Isotopic Composition

et al. 2008

View full text Add to dashboard Cite

The "Centro Español de Metrología" is carrying out a project to improve the knowledge of the influence of impurities and isotopic composition on the temperature of the mercury triple point. High-purity mercury from the Almaden mine (stated purity of 99.9998%) was further purified by vacuum distillation. Three mercury fractions, the original mercury from Almaden and two distilled fractions, were characterized in terms of both impurities and isotopic composition and used to measure the mercury triple point. The original mercury sample contained silver at 560 ng · g −1 as the main impurity while the impurity levels were much lower (silver < 1 ng · g −1 ) in the two distilled fractions. The isotopic composition of the distilled fractions showed delta values, expressed as 1,000×( 198/202 Hg sample − 198/202 Hg reference )/ 198/202 Hg reference , of 1.37 ± 0.07 (1σ ) for the first distilled sample and −1.55 ± 0.03 (1σ ) for the second distilled sample with reference to the original Almaden mercury. For the measurement of the mercury triple point, an alcohol stirred bath was used that allowed two cells to be compared nearly simultaneously. It was observed that the presence of the silver impurities in the high-purity mercury modified slightly the mercury triple point while the effect of variations in the isotopic composition can be considered negligible.

show abstract

“…Impurities in the material cause the phase-transition temperature to depart from that of the pure material. If the target uncertainty of realization assigned to the aluminum fixed point is 0.5 mK [1], the required purity of the aluminum contained in the thermometric cell has to be better than 99.99993% [1]. Samples of aluminum of sufficient purity are not routinely produced and always contain a certain amount of impurities, even after various stages of intensive refining.…”

Section: Impurity Effectmentioning

confidence: 99%

Influence of Impurities and Filling Protocol on the Aluminum Fixed Point

2008

View full text Add to dashboard Cite

To improve the uncertainty of the aluminum fixed point, a study was launched by LNE-INM/CNAM in the framework of the EUROMET Project 732 "Toward more accurate temperature fixed points" (Coordinating laboratory: LNE-INM/CNAM, 17 partner countries). A new open cell was filled with aluminum of 99.99995% purity. A French laboratory carried out elemental analysis of the sample using glow discharge-mass spectrometry (GD-MS). The values of the equilibrium distribution coefficient k and of the derivative δT l /δc i l of the temperature of the liquidus line with respect to the concentration of impurity i will be obtained through collaboration with a French physical and chemical laboratory. In the past, some aluminum cells were opened after several melts and freezes. The aluminum ingot was sticking to the graphite crucible, indicating that physicochemical reactions had likely occurred between Al and C. To avoid this reaction, an effort was made to draw benefit from the Al 2 O 3 film that appears immediately on the surface of the aluminum ingot when it is exposed to oxygen. The open aluminum cell was tested in different furnaces and with different thermal insulator arrangements inside the fixed-point assembly. The observed drifts of the plateaux were always larger than the expected values. The cell was opened to inspect the aluminum ingot. The ingot was extracted easily, since no sticking to the crucible had occurred. The aluminum showed a very bright surface, but the presence of many "craters" throughout the thickness of the ingot was surprising. In some cases, the thermometer well was even apparent.

show abstract

Thermometry's dependence on chemical metrology: a needs-based assessment

Cited by 26 publications

References 7 publications

High-Purity Fixed Points of the ITS-90 with Traceable Analysis of Impurity Contents

High-Purity Fixed Points of the ITS-90 with Traceable Analysis of Impurity Contents

Assembly and Study of Different Mercury Cells with Known Impurity Content and Isotopic Composition

Influence of Impurities and Filling Protocol on the Aluminum Fixed Point

Contact Info

Product

Resources

About