Silver Point Research Articles

Characterization of High-Temperature Platinum Resistance Thermometers at Silver Point

Thermal cycling tests have been conducted on various types of high-temperature standard platinum resistance thermometers (HTSPRTs) that are commercially available at present. The investigated HTSPRTs have nominal resistance values at the triple point of water (TPW) of 0.25 \(\Omega \), 0.6 \(\Omega \), 2.5 \(\Omega \), and 3 \(\Omega \). They vary in terms of the platinum wiring on their sensor supports (frames) and the support materials, their protective sheaths and their sealing materials. Ten HTSPRTs were evaluated with regard to their stability during use at silver-point temperature or above. This evaluation included a thermal cycling test following various setup patterns, which indicated that each HTSPRT has its own preferred pattern. The stability test results for eight of ten HTSPRTs during four silver-point realizations, based on this pattern, yielded a maximum discrepancy in the resistance ratio of within \(\pm 6\,\hbox {mK}\). The maximum resistance discrepancy at TPW was \(\pm 2.7\,\hbox {mK}\).

Calculation of thermodynamic functions of saturated solid solution of AgIn2Te3I compound in the Ag–In–Te–I system

Triangulation of Ag–In–Te–I system in the vicinity of AgIn 2 Te 3 I compound was investigated by X-ray diffraction and differential thermal analysis methods. The spatial position of the phase region AgIn 2 Te 3 I–InTe–Ag 2 Te–AgI regarding the figurative point of silver was used in order to write the equation of virtual potential-forming reaction. Potential-forming reaction was performed in electrochemical cell (ECC) of the type (–) C | Ag | Ag 3 GeS 3 I(Br) glass | D | C (+) where C are inert (graphite) electrodes; Ag and D are the electrodes of the ECC; D represents the alloy of four-phase region; Ag 3 GeS 3 I glass is a membrane with purely ionic Ag + conductivity). Linear dependence of the EMF of cell on temperature in the range of 440−480 К was used to calculate the standard thermodynamic functions of saturated solid solution of AgIn 2 Te 3 I compound in Ag–In–Te–I system.

Thermodynamic properties of saturated solid solutions of Ag7SnSe5Br and Ag8SnSe6 compounds in the Ag–Sn–Se–Br system measured by the EMF method

Triangulation of the Ag–Sn–Se–Br system in the part of Ag2Se–SnSe–SnSe2–AgBr was carried out using the X-ray diffraction and differential thermal analysis methods. The spatial position of the established four-phase regions regarding figurative point of silver was used in order to write the equations of virtual potential-forming chemical reactions. Potential-forming processes were performed in electrochemical cells (ECCs) of the type (−) C |Ag| Ag3GeS3Br glass |D| C (+) where C are the inert (graphite) electrodes; Ag and D are the electrodes of the ECCs; D represents the equilibrium four-phase alloys, and Ag3GeS3Br glass is a membrane with purely ionic Ag+ conductivity. The linear dependencies of the EMF of cells on temperature in the range of 480–520К have been used in order to calculate the standard thermodynamic values of saturated solid solutions of Ag7SnSe5Br and Ag8SnSe6 compounds in the four-element part of the Ag–Sn–Se–Br system.

Analysis of SPRT Calibration Data Obtained at NPL Since the Introduction of the ITS-90

Since the International Temperature Scale of 1990, ITS-90, was introduced, NPL has carried out a large number of calibrations of standard platinum resistance thermometers (SPRTs). Here we present an analysis of 876 calibrations of 435 SPRTs from 12 manufacturers in the various sub-ranges provided for in the ITS-90 between the triple point of argon (or, more usually, at the boiling point of nitrogen) to the freezing point of silver. Over 170 SPRTs have been calibrated more than once, in one case 10 times in 12 years. The calibration records have now been collated into a spreadsheet detailing source and identification data, calibration date, final value of \(R(0.01~{^{\circ }}\hbox {C})\), the measured values of resistance ratio \(W=R(t/{^{\circ }}\hbox {C})/R(0.01~{^{\circ }}\hbox {C})\) at the fixed points, and the coefficients of the deviation equations, a, b, c, and d. These data will permit investigations of the consistency over 23 years of the manufacture and quality of SPRTs including, inter alia, medium-to-long-term stability, ranges of W-values at each fixed point, correlations between W-values at different points and between the a and b coefficients, and the consistency between interpolations in different ITS-90 sub-ranges. A start has been made on these investigations, and this paper is a first report on the results.

Electrochemical determination of thermodynamic properties of saturated solid solutions of Hg2GeSe3, Hg2GeSe4, Ag2Hg3GeSe6, and Ag1.4Hg1.3GeSe6 compounds in the Ag–Hg–Ge–Se system

Triangulation of the Ag–Hg–Ge–Se system in the vicinity of GeSe2, HgSe, Hg2GeSe3, Hg2GeSe4, Ag2Hg3GeSe6, and Ag1.4Hg1.3GeSe6 compounds and selenium was performed using X-ray diffraction and differential thermal analysis methods. The spatial position of the determined four-phase regions regarding figurative point of silver was used to write the equations of virtual potential-forming chemical reactions. Potential-forming processes were performed in electrochemical cells (ECCs) of the type (−) C | Ag | Ag3GeS3I glass | D | C (+) where C are the inert (graphite) electrodes, Ag and D are the electrodes of the ECCs, D represents equilibrium four-phase alloys, and Ag3GeS3I glass is a membrane with purely ionic Ag+ conductivity. The linear dependences of the EMF of galvanic cells on temperature in the range of 425–455 K were used to calculate the standard thermodynamic values of saturated solid solutions of Hg2GeSe3, Hg2GeSe4, Ag2Hg3GeSe6, and Ag1.4Hg1.3GeSe6 compounds.

Magmatism as a response to exhumation of the Priest River complex, northern Idaho: Constraints from zircon U–Pb geochronology and Hf isotopes

Zircon and monazite U–Pb geochronology and zircon Hf isotopes place constraints on the temporal and source relationships between crustal anatexis, magmatism, and exhumation of the Priest River metamorphic core complex, northern Idaho. Granitoids that intruded the migmatitic, pelitic Hauser Lake gneiss include the <76.5±0.1Ma Spokane granite, 50.13±0.02Ma Silver Point quartz monzonite, c. 47.9Ma Wrencoe granodiorite, <46.4±1.8Ma Rathdrum granite, and a <49.8±0.4Ma leucocratic dike. Cretaceous magmatism preceded the c. 64Ma peak metamorphism (recorded by monazite) of the Hauser Lake gneiss, whereas discrete pulses of Eocene magmatic activity post-date the onset of exhumation by 10Ma. The relative timing of pluton emplacement in the Priest River complex indicates that it was primarily a response to decompression rather than a cause. The mylonitized Silver Point and undeformed Wrencoe plutons bracket the end of a rapid phase of exhumation to c. 50–48Ma. Zircon εHf(i) values and Lu–Hf isotope evolution indicate that the Silver Point and Wrencoe plutons crystallized from homogeneous magmas sourced from Archean–Proterozoic basement orthogneisses, whereas the Spokane granite and two leucocratic units appear to have been produced by partial melting of the Hauser Lake gneiss. Comparison of the Priest River complex with other deeply exhumed northern Cordilleran complexes indicates variability in the timing and, therefore, relative influences of partial melting and magmatism on the initiation of exhumation, which must be accounted for in numerical models of metamorphic core complex formation and evolution.

A Comparison of Time Needed for Instrumentation of Simulated Curved Canals by Using Different Files

Background : A more flexible file was needed for instrumentation of curved canals using step back enlargement technique Ni-Ti files has been shown to be exceptionally elastic , having a lower bending moment and lower permanent set after torsion with similar gauge stainless steel files . Aim of the study: is to compare the time needed to prepare curved resin simulated root canals with Ni-Ti, S.S., and SS K-Flex files using a step –back enlargement technique. Materials and methods: 30 simulated root canals were constructed using size 20 silver points as a mold, then divided into 3 groups: group 1: Canals instrumented with SS K – files, group 2: Canals instrumented with stainless steel K- flex files. And group 3: Canals instrumented with Ni – Ti files. Results: The comparison between the three groups using ANOVA and T- test, showed a significant difference in time needed to fully instrument the canals. CONCLUSION: Ni- Ti files required more time to instrument the canals than other files.

LTCC processed CoTi substituted M-type barium ferrite composite with BBSZ glass powder additives for microwave device applications

Hexagonal magnetoplumbite ferrites typically have sintering temperatures above 1100∘C in order to stabilize a single phase compound, which is much higher than the melting point of silver leading to device fabrication challenges. Application of low temperature co-fired ceramics (LTCC) technologies may prove effective in decreasing the sintering temperature of hexagonal ferrites. Ferrite powders combined with glass frit powder is an effective pathway to lowering the sintering temperature. Here, hexagonal M-type barium ferrite (i.e., Ba(CoTi)1.5Fe9O19) ceramics, combined with BBSZ glass powder as a sintering aid were synthesized. Co and Ti ions where used to substitute for Fe cations in order to modify the magnetic anisotropy field. The density, microstructure, magnetic properties and complex permeability are reported. The BBSZ glass addition was shown to improve the densification and magnetic properties of the barium ferrite. The densification of the BaM ferrite Ba(CoTi)1.5Fe9O19 was further enhanced by the glass additive at low firing temperatures of below 900∘C because of the formation of a liquid phase. Complex permeability of ferrites sintered at 900∘C was also influenced by the BBSZ addition and the resonance frequency was shown to decrease with increased amounts of the glass modifier.

Thermodynamic temperature by primary radiometry.

Above the freezing temperature of silver (1234.93 K), the International Temperature Scale of 1990 (ITS-90) gives a temperature, T90, in terms of a defining fixed-point blackbody and Planck's law of thermal radiation in ratio form. Alternatively, by using Planck's law directly, thermodynamic temperature can be determined by applying radiation detectors calibrated in absolute terms for their spectral responsivity. With the advent of high-quality semiconductor photodiodes and the development of high-accuracy cryogenic radiometers during the last two decades radiometric detector standards with very small uncertainties in the range of 0.01-0.02% have been developed for direct, absolute radiation thermometry with uncertainties comparable to those for the realization of the ITS-90. This article gives an overview of a number of design variants of different types of radiometer used for primary radiometry and describes their calibration. Furthermore, details and requirements regarding the experimental procedure for obtaining low uncertainty thermodynamic temperatures with these radiometers are presented, noting that such radiometers can also be used at temperatures well below the silver point. Finally, typical results obtained by these methods are reviewed.

Dissemination of thermodynamic temperature above the freezing point of silver.

The mise-en-pratique for the definition of the kelvin at high temperatures will formally allow dissemination of thermodynamic temperature either directly or mediated through high-temperature fixed points (HTFPs). In this paper, these two distinct dissemination methods are evaluated, namely source-based and detector-based. This was achieved by performing two distinct dissemination trials: one based on HTFPs, the other based on absolutely calibrated radiation thermometers or filter radiometers. These trials involved six national metrology institutes in Europe in the frame of the European Metrology Research Programme joint project 'Implementing the new kelvin' (InK). The results have shown that both dissemination routes are possible, with similar standard uncertainties of 1-2 K, over the range 1273-2773 K, showing that, depending on the facilities available in the laboratory, it will soon be possible to disseminate thermodynamic temperatures above 1273 K to users by either of the two methods with uncertainties comparable to the current temperature scale.

Study on the Impurity Effect in the Realization of Silver Fixed Point

The application of a thermal analysis model to estimate the temperature depression from the ideal fixed-point temperature is important, especially when the chemical analysis of the sample in a cell is insufficient or the cell might have been contaminated during fabrication. This study extends previous work, on thermal analysis with the tin point, to an investigation of the impurity dependence of the silver-point temperature. Close agreement was found between the temperature depression (\(-0.36\) mK) inferred from the thermal analysis of the measured fixed-point plateau and the temperature depression (\(-0.32\) mK) inferred using the sum of individual estimates (SIE) method with an impurity analysis based on glow discharge mass spectrometry. Additionally, the results of the thermal analysis manifest no significant dependence on the rate of solidification, and the scatter of observed gradients was within 0.36 mK among five plateaux with different temperature settings of the furnace. Although the results support the application of both the SIE method and thermal analysis for the silver point, further experiments with cell-to-cell comparisons linked to thermal analysis, a study of the thermometer-furnace systematic effects, the oxygen effect, and the locus of the freezing plateau should be investigated to reach a firm conclusion.

High-temperature platinum resistance thermometry: the problem with silver and the case for gold

The diffusion of silver through quartz at high temperatures leads to contamination of the platinum sensing element of high temperature platinum resistance thermometers. While some protection of the PRT element may be afforded by the application of appropriate electric fields, the contamination of the quartz elements of silver fixed points causes their premature failure. Contamination is evidenced by the yellowish colour imparted to the glass by the silver particles growing within the quartz glass matrix. The presence of silver as the contaminating element has been confirmed unambiguously through energy dispersive x-ray analysis and secondary ion mass spectrometry. To mitigate the risk of silver contamination, the gold point is proposed as an alternative calibration point. PRT resistance ratios measured at the freezing points of silver and gold in different laboratories at different times are highly correlated. This suggests that the ITS-90 reference function might be extrapolated to 1064.18 °C (the gold fixed point). However, it remains unclear from the gold and silver PRT resistance ratios from the literature whether extrapolation of the reference function leads to the correct value at the gold point. A direct comparison of gold fixed points may be required to resolve the inconsistencies. Additional PRT data may help resolve the discrepancy.

A Peep into What Was Behind the Incorporation of Gold Nano Particles in Nano Medicine

or silver points of light so far beyond his reach. The phenomenon of absorption, reflection and scattering of light always fascinated man from ages. The mysterious and curious man started exploiting his gray matter to understand the mystery of colloidal solutions when light is impinged on it. No wonder peeping into the world of metal colloids which explicitly deal with these allpervading phenomena became a matter of excitement.

Alternative Methods of Blackbody Thermodynamic Temperature Measurement Above Silver Point

Presently, absolute radiometry is the main method of thermodynamic temperature determination above the silver point. The importance of such measurements has increased, as a large international project is underway aimed at assigning thermodynamic temperatures to high-temperature fixed points (HTFPs). All participants are using filter radiometers calibrated against an absolute cryogenic radiometer which, therefore, will be the basis of the provided thermodynamic temperatures of the fixed points. However, such a unified approach may lead to systematic errors (if any) common to all participants. There are methods, providing an alternative to absolute radiometry, which allow the determination of blackbody thermodynamic temperatures using relative measurements. Alternative methods, even if they have lower accuracy than absolute radiometry, could disclose some possible unrecognized systematic errors, or, on the contrary, could confirm the results obtained using absolute radiometry and increase confidence of the thermodynamic temperature determination. One such method, known as the method of ratios (i.e., double wavelength technique), is based on measuring the ratios of fluxes emitted by a blackbody in separate spectral ranges at two temperatures. This approach has been developed at VNIIOFI, but its realization met serious technical difficulties. Modern sensors with improved sensitivity and stability, extremely reproducible HTFP blackbodies, and significant progress in computational methods and computer performance provide a new chance to realize this approach with sufficient accuracy. Another method is based on comparing the ratio of fluxes measured at two wavelengths for a high-temperature blackbody with that measured for synchrotron radiation. This article overviews possibilities of the alternative methods for determination of blackbody thermodynamic temperatures by means of relative radiometry to attract attention of the thermometry and radiometry communities to the importance of international cooperation for realization of these methods.

Thermoelectric properties of currently available Au/Pt thermocouples related to the valid reference function

Au/Pt thermocouples are considered to be an alternative to High Temperature Standard Platinum Resistance Thermometers (HTSPRTs) for realizing temperatures according to the International Temperature Scale of 1990 (ITS-90) in the temperature range between aluminium (660.323 °C) and silver (961.78 °C). The original aim of this work was to develop and to validate a new reference function for Au/Pt thermocouples which reflects the properties of presently commercially available Au and Pt wires. The thermoelectric properties of 16 Au/Pt thermocouples constructed at different National Metrological Institutes by using wires from different suppliers and 4 commercially available Au/Pt thermocouples were investigated. Most of them exhibit significant deviations from the current reference function of Au/Pt thermocouples caused by the poor performance of the Au-wires available. Thermoelectric homogeneity was investigated by measuring immersion profiles during freezes at the freezing point of silver and in liquid baths. The thermoelectric inhomogeneities were found to be one order of magnitude larger than those of Au/Pt thermocouples of the Standard Reference Material® (SRM® ) 1749. The improvement of the annealing procedure of the gold wires is a key process to achieve thermoelectric homogeneities in the order of only about (2–3) mK, sufficient to replace the impracticable HTSPRTs as interpolation instruments of the ITS-90. Comparison measurements of some of the Au/Pt thermocouples against a HTSPRT and an absolutely calibrated radiation thermometer were performed and exhibit agreements within the expanded measurement uncertainties. It has been found that the current reference function of Au/Pt thermocouples reflects adequately the thermoelectric properties of currently available Au/Pt thermocouples.

Proposed Process for Estimating Definitive Temperatures of High-Temperature Fixed Points

Filter radiometric measurements of high-temperature fixed points will provide a means of realizing and disseminating the thermodynamic temperature for temperatures above the silver point, with uncertainties that are competitive with the defined ITS-90. This paper presents the analysis method proposed for determining the thermodynamic temperature of the melting transitions of Re–C, Pt–C, and Co–C eutectic fixed points by combining filter radiometer measurements by nine laboratories to obtain a single temperature for each fixed point. It discusses the key sources of error, the corrections applied for known systematic effects, and the uncertainties. These sources of error introduce correlation between the measured values; the paper describes how data can be combined in a way that accounts for that correlation.

Bilateral Comparison Between NPL and INMETRO Using a High-Temperature Fixed Point of Unknown Temperature

There is an on-going requirement to perform scale comparisons above the silver point \((962\,^\circ \hbox {C})\) with reduced uncertainties. Previous comparisons have been performed with high stability lamps or radiation thermometers, neither of which were able to achieve the required uncertainty. Ideally a set of driftless unknown temperature fixed points would be used to compare scales, but up to now such artifacts did not exist. This study develops blind high-temperature comparison artifacts based on doped versions of the high-temperature fixed point (HTFP) Ni–C (nominal temperature \(1329\,^\circ \hbox {C}\)). At INMETRO three HTFP blackbodies were constructed, one of pure Ni–C and two doped with different levels of Cu. To ascertain the effect of doping on the transition temperature, the cells were compared to the reference pure Ni–C cell. The doped cells were then transported to NPL and their temperatures measured. NPL was not informed of the INMETRO result ensuring that the measurements remained blind. The cells were then returned to INMETRO and re-measured to establish their stability. The temperatures measured at INMETRO and NPL were then compared and showed very good equivalence of the scale at the fixed-point temperatures. The results of the comparison of the NPL and INMETRO temperature scale, at nominally \(1329\,^\circ \hbox {C}\), are reported, along with evidence of the stability of the artifacts determined from repeat measurements. These promising results indicate that it may be possible to make HTFPs with altered temperatures which are stable enough to serve as comparison artifacts.

Miniature Fixed-Point Cell Approaches for $${{\varvec{In\,Situ}}}$$ I n S i t u Monitoring of Thermocouple Stability

In the framework of the European Metrology Research Project ENG08 “MetroFission,” LNE-Cnam and NPL have undertaken cooperative research into the development of temperature measurement solutions for the next generation of nuclear fission power plants. Currently, in-pile temperature monitoring is usually performed with nickel-based (Type K or N) thermocouples. When these thermocouples are exposed to a neutron flux, the thermoelements transmute, leading to large and unknown drifts in output. In addition, it is impossible to routinely recalibrate the thermocouples after irradiation for obvious reasons of safety. To alleviate this problem, both LNE-Cnam and NPL have developed, via differing approaches, in situ calibration methods for the thermocouples. The self-validating thermocouple methodologies are based on the principle of a miniature fixed-point cell to be co-located with the thermocouple measurement junction in use. The drift of the thermocouple can be monitored and corrected for by regular determination of the output at the phase transition of the fixed-point material: in effect performing regular in situ calibration checks. The two institutes have constructed miniature fixed-point cells for use at three different temperatures; the freezing point of silver $$(961.78\,^{\circ }\mathrm{C}$$ ; LNE-Cnam), the freezing point of copper $$(1084.62\,^{\circ }\mathrm{C}$$ ; LNE-Cnam and NPL), and the melting point of Fe–C ( $${\sim }1154\,^{\circ }\mathrm{C}$$ ; NPL). This paper introduces the construction and validation of the miniature fixed-point cells prior to use, to ensure traceability to the ITS-90. A comparison of the performance of the two cell designs is discussed, where typical industrial Type N thermocouples have been used for measurement of the fixed-point cells. Such initial measurements demonstrate the feasibility of each of these two approaches.

Monochromator-Based Absolute Calibration of a Standard Radiation Thermometer

Centro Espanol de Metrologia (CEM) is disseminating the International Temperature Scale (ITS-90), at high temperatures, by using the fixed points of Ag and Cu and a standard radiation thermometer. However, the future mise-en-pratique for the definition of the kelvin (MeP-K) will include the dissemination of the kelvin by primary methods and by indirect approximations capable of exceptionally low uncertainties or increased reliability. Primary radiometry is, at present, able to achieve uncertainties competitive with the ITS-90 above the silver point with one of the possible techniques the calibration for radiance responsivity of an imaging radiometer (radiance method). In order to carry out this calibration, IO-CSIC (Spanish Designated Institute for luminous intensity and luminous flux) has collaborated with CEM, allowing traceability to its cryogenic radiometer. A monochromator integrating sphere-based spectral comparator facility has been used to calibrate one of the CEM standard radiation thermometers. The absolute calibrated standard radiation thermometer has been used to determine the temperatures of the fixed points of Cu, Co–C, Pt–C, and Re–C. The results obtained are 1357.80 K, 1597.10 K, 2011.66 K, and 2747.64 K, respectively, with uncertainties ranging from 0.4 K to 1.1 K.

Long-Term Monitoring of Thermocouple Stability with Miniature Fixed-Point Cells

In the framework of the European Metrology Research Programme ENG08 “MetroFission” project, two National Measurement Institutes, LNE-Cnam (France) and NPL (UK), have cooperatively developed methods of in situ validation of thermocouple output for application in next-generation nuclear fission power plants. Miniature fixed-point cells for use at three temperatures were constructed in the first step of this project: at the freezing point of silver (\(961.78\,^{\circ }\mathrm{C}\)), the freezing point of copper (\(1084.62\,^{\circ }\mathrm{C}\)), and the melting point of the iron–carbon eutectic (\(1154\,^{\circ }\mathrm{C}\)). This paper reports the results of a second step in the study, where the robustness of the self-validation method has been investigated. Typical industrial Type N thermocouples have been employed with each of the miniature fixed-point devices installed, and repeatedly thermally cycled through the melting and freezing transitions of the fixed-point ingots. The devices have been exposed to a total of up to 90 h in the molten state. Furthermore, the LNE-Cnam devices were also subjected to fast cool-down rates, on five occasions, where the rate is estimated to have been between \(150\,^{\circ }\mathrm{C}\,{\cdot }\min ^{-1}\) and \(200\,^{\circ }\mathrm{C}\,{\cdot } \min ^{-1}\). The devices are shown to be repeatable, reliable, and robust over the course of these tests. The drift of the Type N thermocouple has been identified separately to the behavior of the device. A reliable method for improving thermocouple performance and process control is therefore demonstrated. Requirements for implementation and the advantages of each approach for monitoring and correcting thermocouple drift are discussed, and an uncertainty budget for self-validation is presented.