Kinetic and Thermodynamic Study of Calcite Marble Samples from Lesser Himalayas

A kinetic and thermodynamic study of selected calcite marble samples from Lesser Himalayas has been performed using thermogravimetric and differential thermal analyses at heating rates of \(10\,^{\circ }\mathrm{C}\,{\cdot }\min ^{-1}\) and \(30\,^{\circ }\mathrm{C}\,{\cdot }\min ^{-1}\) . The minero-petrography of calcite grains, phase analysis, chemical analysis, and minor impurities determination were carried out using thin-section polarized light microscopy, X-ray diffraction, X-ray fluorescence, and electron microprobe analysis, respectively. The calcite content of the investigated marble samples varied from 97.50 mass% to 98.70 mass%. The activation energy, \(E_\mathrm{a}\) , for the decomposition process increased from \(158.6\,\mathrm{kJ}\,{\cdot }\mathrm{mol}^{-1}\) to \(179.4\,\mathrm{kJ}\,{\cdot }\,\mathrm{mol}^{-1}\) and from \(214.1\,\mathrm{kJ}\,{\cdot }\, \mathrm{mol}^{-1}\) to \(232.8\,\mathrm{kJ}\,{\cdot }\, \mathrm{mol}^{-1}\) for heating rates of \(10\,^{\circ }\mathrm{C}\,{\cdot }\, \min ^{-1}\) and \(30\,^{\circ }\mathrm{C}\,{\cdot }\, \min ^{-1}\) , respectively, with decreasing calcite content. The activation energy values obtained in the present study were in good agreement with previous studies.     

Climatic Chamber for Temperatures up to 180\,^{\circ }\mathrm{C} and Pressures up to 0.5 MPa

A new relative-humidity setup was developed for calibrating sensors in the temperature range from \(-40\,^{\circ }\mathrm{C}\) up to \(180\,^{\circ }\mathrm{C}\) and at pressures down to 700 hPa and up to 0.5 MPa. The setup is based on the chamber-in-chamber model: a small additional chamber is positioned inside a climatic chamber. While the climatic chamber is used to generate the air temperature, a pre-conditioned gas from outside the climatic chamber delivers the required humidity in the new pressure chamber. Validation of the setup at atmospheric pressure showed relative-humidity uncertainties of 0.2 %rh at 5 %rh over the whole temperature range and 0.4 %rh at 95 %rh for temperatures above \(0\,^{\circ }\mathrm{C}\) . Below \(0\,^{\circ }\mathrm{C}\) , the maximum uncertainty increases to 0.9 %rh due to the influence of the temperature homogeneity. The temperature uncertainty of the new setup is between \(0.10\,^{\circ }\mathrm{C}\) and \(0.21\,^{\circ }\mathrm{C}\) . Five commercially available relative-humidity sensors, of different type and manufacturer and all suitable for high temperatures, were calibrated in the new setup. The measurements showed deviations outside the stated specifications of the manufacturer and the need of traceable calibration facilities.     

Search for Anomalous Temperature Behavior of the Viscosity of Polyethylene Glycol Solutions

Viscometric studies of polyethylene glycol (PEG 35000) aqueous solutions are presented. The temperature and concentration dependences of the PEG solution viscosities were studied in the range from \(10\,^{\circ }\mathrm{C}\) to \(60\,^{\circ }\mathrm{C}\) and \(5\,\mathrm{mg}{\cdot } \mathrm{ml}^{-1}\) to \(50\, \mathrm{mg}{\cdot } \mathrm{ml}^{-1}\) , respectively. The intrinsic viscosity and the Huggins coefficient have been calculated from the data. The results exclude the recently reported anomalous behavior of these quantities. The measured viscosity is also used to estimate the hydrodynamic and gyration radii of the polymers.     

Temperature Coefficients of the Refractive Index for Complex Hydrocarbon Mixtures

Temperature coefficients of the refractive index ( \(\mathrm{d}n/\mathrm{d}T\) ) in the \(25\,^{\circ }\mathrm{C}\) to \(35\,^{\circ }\mathrm{C}\) temperature interval for hydrocarbon mixtures containing as many as 14 compounds were investigated in this work. The measured \(-\mathrm{d}n/\mathrm{d}T\) of the mixtures were compared with calculations based on the values for each compound and their concentrations. Differences of about 1 % between measured and calculated values were observed for all mixtures. The additivity of \(-\mathrm{d}n/\mathrm{d}T\) for these hydrocarbons enables preparation of surrogate fuels that are formulated to have properties like those of specific diesel fuels.     

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.     

Calibration of Industrial Platinum Resistance Thermometers up to 700\,^{\circ }\mathrm{C}

Industrial grade platinum resistance thermometers were calibrated in the temperature range from \(200\,^{\circ }\mathrm{C}\) to \(700\,^{\circ }\mathrm{C}\) . Both wire-wound and thin-film sensor-based thermometers were investigated. The purpose of the study was to investigate thermometers which could be used in future coal power plants. The calibrations were performed in a vertical cesium heat-pipe furnace and in a horizontal and vertical sodium heat-pipe furnace. The reference thermometer was a standard platinum resistance thermometer calibrated at fixed points up to the aluminum point. In addition to calibration, various thermal tests including immersion measurements and thermal-cycling tests were performed. The stability of the sensors was determined by monitoring the ice-point resistance. Possible contamination of the sensors was determined by measuring the resistance ratio \(R(30\,^{\circ }\mathrm{C})/R(10\,^{\circ }\mathrm{C})\) several times during the measurement period. The calibration curves were compared with the ICE 60751 standard and International Temperature Scale 1990 (ITS-90) reference functions. Considerable changes were found in all tested thermometers. The wire-wound sensors were more stable than the thin-film sensors.     

Validation of Primary Water Dew-Point Generator for Methane at Pressures up to 6 MPa

In this paper, the validation of the water dew-point generator with methane as a carrier gas in the temperature range from \(-41\,^{\circ }\hbox {C}\) to \(+15\,^{\circ }\hbox {C}\) and at pressures up to 6 MPa is reported. During the validation, the generator was used with both nitrogen and methane to investigate the effect of methane on the generator and the chilled mirror dew-point meters. The effect of changing the flow rate and the dew-point temperature of the gas entering the generator, on the gas exiting the generator was investigated. As expected, methane at high pressures created hydrates in combination with water and low temperatures, thus limiting the temperature range of the generator to \(+8\,^{\circ }\hbox {C}\) to \(+15\,^{\circ }\hbox {C}\) at its maximum operating pressure of 6 MPa. A lower operating pressure extended the temperature range; for example, at 3 MPa, the temperature range was already extended down to \(-15\,^{\circ }\hbox {C}\) , and at 1 MPa, the range was extended down to \(-41\,^{\circ }\hbox {C}\) . The validation showed that, in its operating range, the generator can achieve with methane the same standard uncertainty of \(0.02\,^{\circ }\hbox {C}\) frost/dew point already demonstrated for nitrogen and air carrier gases.     

Bilateral Comparison Between CMI and CEM in Radiance Temperature Scale Realization from 232\,^{\circ }\mathrm{C} to 1085\,^{\circ }\mathrm{C}

A bilateral comparison between the Centro Español de Metrología (CEM) and the ?eský Metrologický Institut (CMI) of radiance temperature scale realizations in the range from \(232\,^{\circ }\mathrm{C}\) to \(1085\, ^{\circ }\mathrm{C}\) was carried out during 2012 to support the calibration measurements capabilities of CMI in radiation thermometry. The CEM capabilities were demonstrated previously in a recent comparison of European laboratories over the range from \(156\,^{\circ }\mathrm{C}\) to \(1000\,^{\circ }\mathrm{C}\) . A CMI KE-LP5 radiation thermometer, working at 1568 nm, was used as a traveling standard. CEM measurements were done at the fixed-points (FPs) of Zn, Ag, and Cu and, for the rest of the temperatures, variable temperature blackbodies (VTBBs) were used. CMI measurements were done at the FPs of Sn, Al, and Cu, and the rest of the temperatures were measured with VTBBs. The size-of-source effect was measured at CEM to decide whether or not the measurements from both laboratories should be corrected by this effect (when the diameter of the sources was different at each laboratory). CMI performed the measurement of the Al FP before and after CEM to evaluate the stability of the radiation thermometer. The results for both laboratories are summarized, and they agree within their expanded uncertainties.     

Validation of a Blackbody Comparator-Based System for Thermocouple Calibration

A blackbody comparator for thermocouple calibration in the temperature range from \(960\,^{\circ }\hbox {C}\) to \(1500\,^{\circ }\hbox {C}\) has previously been developed at the Centre for Metrology and Accreditation (MIKES). The calibration system is based on direct comparison of thermocouples and a radiation thermometer. In this article, the blackbody comparator is exploited by comparing an absolute calibrated irradiance mode filter radiometer and a linear pyrometer calibrated according to the International Temperature Scale of 1990 (ITS-90) to each other in the temperature range from \(1000\,^{\circ }\hbox {C}\) to \(1500\,^{\circ }\hbox {C}\) . The results of the comparison are in agreement within uncertainties ( \(k = 2\) ). Furthermore, thermal gradients in the blackbody comparator are studied by means of numerical simulation, as the gradients were found to be the major source of uncertainty in previous work. A thermal model was constructed with COMSOL software, and the radial and longitudinal gradients were studied in the comparator. The results of the modeling are in agreement with the uncertainty determination carried out in previous work, but the gradients still remain a significant uncertainty contribution. The validation of the calibration system was completed by comparing calibration results obtained with the system for a Pt/Pd thermocouple to calibration results reported by the National Physical Laboratory (NPL), UK. The results of the comparison agree within the expanded uncertainty ( \(k = 2\) ) of the comparison.     

Performance of Pt–C,Cr_7C_3–Cr_3C_2, Cr_3C_2–C,and Ru–C Fixed Points for Thermocouple Calibrations Above 1600 ^{\circ }C

A series of high-temperature fixed points (HTFPs) Pt–C (1738 \(^{\circ }\mathrm {C}), \text {Cr}_{7}\text {C}_{3}{-\text {Cr}}_{3}\text {C}_{2}\,(1742\,^{\circ } \mathrm{C}), \text {Cr}_{3}\text {C}_{2}{-\text {C}}\,(1826\,^{\circ }\mathrm{C})\) , and Ru-C (1953 \(^{\circ }\text {C}\) ) have been constructed at the National Physical Laboratory (NPL) and the Laboratoire National de métrologie et d’Essais and Conservatoire national des arts et métiers (LNE-Cnam). These are required for the calibration of high-temperature thermocouples in the framework of work package 6 of the European Metrology Research Programme IND01 project “HiTeMS.” The goal of this work package is to establish a European capability that can determine low-uncertainty reference functions of non-standard high-temperature thermocouples. For reference functions to be widely applicable, measurements must be performed by more than one institute and preferably by more than one method. Due to the high price of the ingot materials, miniature HTFP cells are used. NPL and LNE-Cnam constructed their HTFP cells with different designs; these are described here, together with the performance of the cells using both radiation thermometry and thermocouples. The melting temperature of the Ru–C cells (for thermocouple calibrations) was determined using radiation thermometry at both NPL and LNE-Cnam, and the two results are compared. The suitability of the cells for calibration of W–Re and Rh–Ir thermocouples is evaluated, and some results are presented. Some discussion is given regarding the materials challenges when calibrating Rh–Ir thermocouples up to 2000 \(^{\circ }\) C.     

Comparison of Air Temperature Calibrations

European national metrology institutes use calibration systems of various types for calibrating thermometers in air. These were compared to each other for the first time in a project organized by the European Association of National Metrology Institutes (EURAMET). This EURAMET P1061 comparison project had two main objectives: (1) to study the equivalence of calibrations performed by different laboratories and (2) to investigate correlations between calibration methods and achievable uncertainties. The comparison was realized using a pair of 100  \(\Omega \) platinum resistance thermometer probes connected to a digital thermometer bridge as the transfer standard. The probes had different dimensions and surface properties. The measurements covered the temperature range between \(-40\,^{\circ }\mathrm{{C}}\) and \(+150\,^{\circ }\mathrm{{C}}\) , but each laboratory chose a subrange most relevant to its scope and performed measurements at five nominal temperature points covering the subrange. To enable comparison between the laboratories, comparison reference functions were determined using weighted least-squares fitting. Various effects related to variations in heat transfer conditions were demonstrated but clear correlations to specific characteristics of calibration system were not identified. Calibrations in air and liquid agreed typically within \(\pm 0.05\,^{\circ }\mathrm{{C}}\) at \(+10\,^{\circ }\mathrm{{C}}\) and \(+80\,^{\circ }\mathrm{{C}}\) . Expanded uncertainties determined by the participants ranged from \(0.02\,^{\circ }\mathrm{{C}}\) to \(0.4\,^{\circ }\mathrm{{C}}\) and they were shown to be realistic in most cases.     

Thermal Stability of \beta -PtO_2 Investigated by Simultaneous Thermal Analysis and Its Influence on Platinum Resistance Thermometry

We present thermogravimetric and differential scanning calorimetric studies of PtO \(_2\) powders measured in different atmospheres. In synthetic air a mass loss of 11.4 % is found at the decomposition temperature \(T_\mathrm {D}\)  = 595  \(^{\circ }\hbox {C}\) which can be attributed to the reduction of PtO \(_2\) . In a helium atmosphere the mass loss is 12.0 % and is found at 490  \(^{\circ }\hbox {C}\) . Subsequent heating in air leads to another oxidation process above \(T_\mathrm {D}\) and a reduction at 800  \(^{\circ }\hbox {C}\) . The second oxidation and reduction process is strongly suppressed when the powder is heated in He. The remaining mass above \(T_\mathrm {D}\) does not comply with a reduction path PtO \(_2 \rightarrow \) PtO \(\rightarrow \) Pt. Differential scanning calorimetry shows an endothermic reaction at \(T_\mathrm {D}\) in synthetic air as well as in helium which corresponds with the mass loss. These measurements imply that the powder can be assigned to be \(\beta \) -PtO \(_2\) . Furthermore, catalytic activity of the PtO \(_2\) powder is evidenced by mass spectrometry to be present below 460  \(^{\circ }\hbox {C}\) . Finally, the impact of these findings on the stability of platinum resistance thermometers is discussed.     

Preflight Spectral Radiance Infrared Calibration Facility

Preflight calibration of space-based observation systems (SOBS) is carried out by means of standard sources with known spectral radiance. There are no difficulties in preflight calibration of SOBS within the visible spectral range. The main problem here lies in achieving sufficiently high uniformity of spectral radiance across the radiating aperture of a large-area source. Standard blackbody radiance sources with the temperature that is measured and with the calculated emissivity are used for calibration of SOBS in the infrared (IR) spectral range. The emissivity of sources having an aperture as large as 500 mm cannot be calculated accurately enough, and they have to be measured. It is quite challenging to conduct the measurements in a vacuum chamber simulating the low earth orbit environment in a broad temperature range. A spectral radiance calibration facility for preflight calibration of SOBS which is based on using a large-area blackbody with a diameter of 500 mm and an operational temperature range from \(-60~^{\circ }\mathrm{C}\) to \(150~^{\circ }\mathrm{C}\) is presented. The facility includes a gallium fixed-point blackbody, a variable temperature blackbody with a temperature range from \(-60\,^{\circ }\mathrm{C}\) to \(150\,^{\circ }\mathrm{C}\) , a reference liquid nitrogen-cooled blackbody located in the vacuum chamber, and a Fourier transform IR spectrometer (FT-IR) used as a comparator. Radiation from the different sources is fed, in sequence, into the comparator by means of a custom-made optomechanical system located in the vacuum chamber. Operation of the calibration facility is described. Characteristics and specifications of the sources are shown.     

Pure Nickel Fixed Points for Contact Thermometry Calibrations

A robust fixed point using pure nickel contained in an alumina crucible has been developed for thermocouple calibrations. It was observed that a deep supercool often caused the freezing plateau to be short and have a large slope. A procedure for realizing the pure nickel fixed points was developed that reserved a small amount of nickel in the solid state to act as a seed for nucleation of the freeze. This procedure was found to allow freezing plateaus that were suitably long and flat to make them useful for calibrating thermocouples. Using a calibrated Pt/Pd thermocouple, the freezing temperature of nickel was determined to be \(1455.22\,^{\circ }\hbox {C}\) with a \((k = 2)\) uncertainty of \(0.8\,^{\circ }\hbox {C}\) .     

Surface Recombination Velocity Dependence on Morphological Properties of CdTe Thin Films Prepared by Close-Spaced Sublimation

Cadmium telluride (CdTe) thin films were prepared on glass substrates by employing the close-spaced sublimation technique. Different source ( $T_\mathrm{sou}$ ) and substrate temperatures ( $T_\mathrm{sub}$ ) were used in order to change the structural properties of layers. The ranges chosen were: $550\,^{\circ }\hbox {C} \le T_\mathrm{sou} \le 650\,^{\circ }\hbox {C}$ and $400\,^{\circ }\hbox {C} \le T_\mathrm{sub} \le 600\,^{\circ }\hbox {C}$ . The environment in the growing chamber was also changed with the purpose to study its influence on the crystalline properties of the surface and volume of the material. Three different surroundings were used: vacuum, high-purity argon, and high-purity oxygen. The surface recombination velocity (SRV) was calculated from photoacoustic (PA) measurements by employing the open PA cell configuration. The behavior of the experimental results was analyzed as a function of the structural characteristics of the films: texture and grain size. Scanning electron microscopy, optical absorption, X-ray diffraction, and dark resistivity measurements were also employed to analyze the properties of the CdTe films. The minimum value for the SRV was found for $T_\mathrm{sou} = 650\,^{\circ }\hbox {C},\, T_\mathrm{sub} = 600\,^{\circ }\hbox {C}$ in an oxygen ambient.     

Experimental and Numerical Study on Heat Transfer Characteristics of Metallic Honeycomb Core Structure in Transient Thermal Shock Environments

The metallic honeycomb core structure has important engineering applications in the aerospace and aviation fields due to several advantages, such as being lightweight, its strong resistance to deformation in high-temperature environments, and its excellent energy absorption characteristics. In the present study, a transient heating experimental system for high-speed flight vehicles was developed to study the thermal insulation characteristics of a superalloy honeycomb core structure at different thermal shock rates \((5\,^{\circ }\mathrm{C}{\cdot }\mathrm{s}^{-1}\, \mathrm{to}\,30\,^{\circ }\mathrm{C}{\cdot }\mathrm{s}^{-1})\) . The highest instantaneous temperature tested was \(950\,^{\circ }\mathrm{C}\) . The three-dimensional finite element method was used to numerically calculate the thermal insulation characteristics of the metallic honeycomb core structure in a high-speed thermal shock environment. The calculated results agree well with the experimental results; this agreement demonstrates that to an extent, numerical calculations are a better alternative than expensive experiments. The results of this study provide an important reference for the thermal protection design of metallic honeycomb core structures of high-speed flight vehicles.     

Magnetic Properties of Nanocrystalline Nickel–Cobalt Ferrites (\mathrm{Ni}_{1/2}{\mathrm{{Co}}}_{1/2}{\mathrm{{Fe}}}_{2}{\mathrm{O}}_{4})

In this study, the nanocrystalline nickel–cobalt ferrites $(\mathrm{Ni}_{1/2}\mathrm{Co}_{1/2}\mathrm{Fe}_{2}\mathrm{O}_{4})$ were prepared via the citrate route method at $27\,^{\circ }\mathrm{C}$ . The samples were calcined at $300\,^{\circ }\mathrm{C}$ for 3 h. The crystalline structure and the single-phase formations were confirmed by X-ray diffraction (XRD) measurements. Prepared materials showed the cubic spinel structure with m3m symmetry and Fd3m space group. The analyses of XRD patterns were carried out using POWD software. It gave an estimation of lattice constant “ $a$ ” of 8.3584 Å, which was in good agreement with the results reported in JCPDS file no. 742081. The crystal size of the prepared materials calculated by Scherer’s formula was 27.6 nm and the electrical conductivity was around $10^{-5}~\mathrm{S}\,\cdot \, \mathrm{m}^{-1}$ . The permeability component variations with frequency were realized. The magnetic properties of the prepared materials were analyzed by a vibrating sample magnetometer (VSM). It showed a saturation magnetization of $27.26\,\mathrm{emu} \cdot \mathrm{m}^{-1}$ and the behavior of a hard magnet.     

Effect of Grain Size of BaTiO_{3}Ceramics on Thermal Expansion and Electrical Properties

The thermal expansion behavior and electrical resistivity of BaTiO \(_{3}\) ceramics with different grain sizes were investigated. When they were heated and subsequently cooled in the range from 25  \(^{\circ }\) C to 200  \(^{\circ }\) C, the expansion and contraction curves of BaTiO \(_{3}\) ceramics with grain sizes of 600 nm and 1500 nm were not matched well to each other, and abnormal contraction and expansion behaviors were observed. For 30 nm and 150 nm BaTiO \(_{3}\) ceramics, the expansion and contraction curves basically are straight lines during heating. The linear thermal expansion coefficients ( \(\alpha _\mathrm{L}\) ) and the electrical resistivity of BaTiO \(_{3}\) ceramics were also measured. Experimental results showed that the value of \(\alpha _\mathrm{L}\) increases and the electrical resistivity decreases gradually with reducing grain size. This phenomenon can be attributed to the combination effect of the grain boundary and oxygen vacancies.     

Miniature Fixed-Point Cell Approaches for {{\varvec{In\,Situ}}} 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.