Thermodynamic Temperature Measurement to the Indium Point Based on Radiance Comparison

A multi-national project (the EMRP InK project) was completed recently, which successfully determined the thermodynamic temperatures of several of the high-temperature fixed points above the copper point. The National Metrology Institute of Japan contributed to this project with its newly established absolute spectral radiance calibration capability. In the current study, we have extended the range of thermodynamic temperature measurement to below the copper point and measured the thermodynamic temperatures of the indium point (\(T_{90} =\) 429.748 5 \(\hbox {K}\)), tin point (505.078 K), zinc point (692.677 K), aluminum point (933.473 K) and the silver point (1 234.93 K) by radiance comparison against the copper point, with a set of radiation thermometers having center wavelengths ranging from \(0.65\,\upmu \hbox {m}\) to \(1.6\,\upmu \hbox {m}\). The copper-point temperature was measured by the absolute radiation thermometer which was calibrated by radiance method traceable to the electrical substitution cryogenic radiometer. The radiance of the fixed-point blackbodies was measured by standard radiation thermometers whose spectral responsivity and nonlinearity are precisely evaluated, and then the thermodynamic temperatures were determined from radiance ratios to the copper point. The values of \(T-T_{90}\) for the silver-, aluminum-, zinc-, tin- and indium-point cells were determined as ?4 mK (\(U = 104\,\hbox {mK}, k=2\)), ?99 mK (88 mK), ?76 mK (76 mK), ?68 mK (163 mK) and ?42 mK (279 mK), respectively.     

Apparatus for Measuring Spectral Emissivity of Solid Materials at Elevated Temperatures

Spectral emissivity measurements at high temperature are of great importance for both scientific research and industrial applications. A method to perform spectral emissivity measurements is presented based on two sample heating methods, the flat plate and tubular furnace. An apparatus is developed to measure the normal spectral emissivity of solid material at elevated temperatures from 1073 K to 1873 K and wavelengths from \(2\,\upmu \hbox {m}\) to \(25\,\upmu \hbox {m}\). Sample heating is accomplished by a torch flame or a high temperature furnace. Two different variable temperature blackbody sources are used as standard references and the radiance is measured by a FTIR spectrometer. Following calibration of the spectral response and background radiance of the spectrometer, the effect of the blackbody temperature interval on calibration results is discussed. Measurements are performed of the normal spectral emissivity of SiC and graphite over the prescribed temperature and wavelength range. The emissivity of SiC at high temperatures is compared with the emissivity at room temperature, and the influence of an oxide layer formed at the surface of SiC on the emissivity is studied. The effect of temperature on the emissivity of graphite is also investigated. Furthermore, a thorough analysis of the uncertainty components of the emissivity measurement is performed.     

Emission of Gas and $$\hbox {Al}_{2}\hbox {O}_{3}$$ Smoke in Gas–Al Particle Deflagration: Experiments and Emission Modeling for Explosive Fireballs

Emission of gas and \(\hbox {Al}_{2}\hbox {O}_{3}\) smoke within the deflagration of \(\hbox {H}_{2}{-}\hbox {O}_{2}\)–{\(\hbox {N}_{2}{-}\hbox {CO}_{2}\)}–Al particles has been studied in a closed combustion chamber at pressures of up to 18 bar and at gas temperatures of up to 3700 K. Measurements of radiance intensity were taken using a five wavelength pyrometer (0.660 \(\upmu \hbox {m}\), 0.850 \(\upmu \hbox {m}\), 1.083 \(\upmu \hbox {m}\), 1.260 \(\upmu \hbox {m}\), 1.481 \(\upmu \hbox {m}\)) and a grating spectrometer in the range (4.10 \(\upmu \hbox {m}\) to 4.30 \(\upmu \hbox {m}\)). In order to characterize the aluminum oxide smoke size and temperature, an inversion method has been developed based on the radiation transfer equation and using pyrometer measurements and thermochemical calculations of \(\hbox {Al}_{2}\hbox {O}_{3}\) smoke volume fractions. Temperatures in combustion gas have been determined using a method based on the assumed blackbody head of the 4.26 \(\upmu \hbox {m}\) \(\hbox {CO}_{2}\) emission line and on its spectral shift with pressure and temperature. For validation purpose, this method has been applied to measurements obtained when calibrated alumina particles are injected in a combustion chamber prior to gaseous deflagrations. This mathematical inversion method was developed to investigate explosive fireballs.     

Facility for Measuring the Spatial Uniformity of the Radiation Power of the Surface of the Large-Area Blackbody

The new stage of the development of space-borne information systems is the creation of the Global Earth Observation System. For the full functioning of such a system, it is necessary to provide the uniformity of measurements of all national systems as members of the global system, with high-quality measurement data. This requires the implementation of a high level of ground (prelaunch) calibration of Earth remote sensing instruments. To solve these problems, there were created calibration facilities on the basis of large vacuum chambers with vacuum reference radiation sources, including sources on the basis of black bodies with a wide aperture of 500 mm in the spectral range from \(3~{\upmu }\hbox {m}\) to \(14~{\upmu }\hbox {m}\). Such a facility was created by FGUP “VNIIOFI” in cooperation with FGUP “TsNIIMash”. The ground calibration of Earth remote sensing instruments is being carried out by using blackbody models as radiation sources with known spectral radiance. Facility for ground calibration of remote sensing devices on spectral radiance is based on the usage of a large-aperture blackbody (LABB) with 500 mm diameter and working temperature range from 213 K to 423 K, as a radiation source. This calibration setup comprises a set of reference blackbodies, such as a blackbody on the phase transition of Gallium, a variable-temperature blackbody with temperature range from 213 K to 423 K, a reference blackbody cooled with liquid nitrogen, and IR Fourier spectrometer utilized as a comparator to perform LABB calibration on spectral radiance. The second important characteristic of LABB is the uniformity of spectral radiance across the radiating aperture of this blackbody. The paper describes the device for measuring the spatial homogeneity of the radiation power of the LABB’s radiating surface. This device is based on the use of two-color InSb-CdHgTe detector equipped with modulator and IR lens, which are mounted on a two-axis translation stage suitable for operation in vacuum and installed in the vacuum chamber against LABB. During the measurement of the radiation uniformity, the modulator sequentially sends probing radiation spot either from the LABB’s surface or from the thermostatic radiation source to the detector input. The principle of operation of the device is described. The results of measurements of the radiation power homogeneity across the LABB’s radiating aperture are presented in wide-temperature range.     

The Influence of Impurities on the Zinc Fixed Point

Impurities are considered to be the most significant source of uncertainty for the realization of the International Temperature Scale of 1990 by means of metal fixed points. The determination and further reduction in this uncertainty require a traceable chemical analysis of dissolved impurities in the fixed-point metal and accurate knowledge of the specific temperature change caused by impurities (slope of the liquidus line). We determined the slope of the liquidus line for three binary systems and present results and conclusions from the chemical analysis of zinc with a nominal purity of 7N. For the Fe–Zn system, we determined a liquidus slope of (\(-0.91\pm 0.14\)) mK / (\(\upmu \hbox {g}{\cdot }\hbox { g}^{-1}\)) from the evaluation of freezing plateaus and (\(-0.76~\pm 0.20\)) mK / (\(\upmu \hbox {g}{\cdot }\hbox { g}^{-1}\)) from the evaluation of melting plateaus; for the Pb–Zn system, the corresponding results are (\(-0.27~\pm 0.05\)) mK / (\(\upmu \hbox {g}{\cdot }\hbox { g}^{-1}\)) and (\(-0.26~\pm 0.05\)) mK / (\(\upmu \hbox {g}{\cdot }\hbox { g}^{-1}\)). Although for the Sb–Zn system, we determined a liquidus slope of about \(-0.8\) mK / (\(\upmu \hbox {g}{\cdot }\hbox { g}^{-1}\)), our investigations showed that a correction of the influence of antimony is highly questionable because antimony can be found in zinc in a fully dissolved state or precipitated as an insoluble compound. Iron is the only impurity where a correction of the fixed-point temperature was possible. For the realization of the zinc fixed point at PTB, this correction is between 2 \(\upmu \)K and 16 \(\upmu \)K depending on the batch of zinc used. The influence of the sum of all impurities was estimated by means of the OME method. The resulting uncertainty contribution is between 12 \({\upmu }\hbox {K}\) and 48 \({\upmu }\hbox {K}\).     

Comparative Study of Two InGaAs-Based Reference Radiation Thermometers

More than one decade ago, an InGaAs detector-based transfer standard infrared radiation thermometer working in the temperature range from \(150\,{^{\circ }}\hbox {C}\) to \(1100\,{^{\circ }}\hbox {C}\) was built at TUBITAK UME in the scope of collaboration with IMGC (INRIM since 2006). During this timescale, the radiation thermometer was used for the dissemination of the radiation temperature scale below the silver fixed-point temperature. Recently, a new radiation thermometer with the same design but with different spectral responsivity was constructed and employed in the laboratory. In this work, we present the comparative study of these thermometers. Furthermore, the paper describes the measurement results of the thermometer’s main characteristics such as the size-of-source effect, spectral responsivity, gain ratio, and linearity. Besides, both thermometers were calibrated at the freezing temperatures of indium, tin, zinc, aluminum, and copper reference fixed-point blackbodies. The main study is focused on the impact of the spectral responsivity of thermometers on the interpolation parameters of the Sakuma–Hattori equation. Furthermore, the calibration results and the uncertainty sources are discussed in this paper.     

The Melting Point of Palladium Using Miniature Fixed Points of Different Ceramic Materials: Part II—Analysis of Melting Curves and Long-Term Investigation

Fifteen miniature fixed-point cells made of three different ceramic crucible materials (\(\hbox {Al}_{2}\hbox {O}_{3}\), \(\hbox {ZrO}_{2}\), and \(\hbox {Al}_{2}\hbox {O}_{3}(86\,\%)+\hbox {ZrO}_{2}\)(14 %)) were filled with pure palladium and used to calibrate type B thermocouples (Pt30 %Rh/Pt6 %Rh). A critical point by using miniature fixed points with small amounts of fixed-point material is the analysis of the melting curves, which are characterized by significant slopes during the melting process compared to flat melting plateaus obtainable using conventional fixed-point cells. The method of the extrapolated starting point temperature using straight line approximation of the melting plateau was applied to analyze the melting curves. This method allowed an unambiguous determination of an electromotive force (emf) assignable as melting temperature. The strict consideration of two constraints resulted in a unique, repeatable and objective method to determine the emf at the melting temperature within an uncertainty of about \(0.1\,\upmu \hbox {V}\). The lifetime and long-term stability of the miniature fixed points was investigated by performing more than 100 melt/freeze cycles for each crucible of the different ceramic materials. No failure of the crucibles occurred indicating an excellent mechanical stability of the investigated miniature cells. The consequent limitation of heating rates to values below \({\pm }3.5\,\hbox {K}\,\hbox {min}^{-1}\) above \(1100\,{^{\circ }}\hbox {C}\) and the carefully and completely filled crucibles (the liquid palladium occupies the whole volume of the crucible) are the reasons for successfully preventing the crucibles from breaking. The thermal stability of the melting temperature of palladium was excellent when using the crucibles made of \(\hbox {Al}_{2}\hbox {O}_{3}(86\,\%)+\hbox {ZrO}_{2}(14\,\%)\) and \(\hbox {ZrO}_{2}\). Emf drifts over the total duration of the long-term investigation were below a temperature equivalent of about 0.1 K–0.2 K.     

Reproducibility of the Helium-3 Constant-Volume Gas Thermometry and New Data Down to 1.9 K at NMIJ/AIST

This study confirms reproducibility of the International Temperature Scale of 1990 (ITS-90) realized by interpolation using the constant-volume gas thermometer (CVGT) of National Metrology Institute of Japan (NMIJ)/AIST with \(^{3}\)He as the working gas from 3 K to 24.5561 K by comparing the newly obtained results and those of earlier reports, indicating that the CVGT has retained its capability after renovation undertaken since strong earthquakes struck Japan. The thermodynamic temperature T is also obtained using the single-isotherm fit to four working gas densities (\(127\,\hbox {mol}\cdot \hbox {m}^{-3}\), \(145\,\hbox {mol}\cdot \hbox {m}^{-3}\), \(171\,\hbox {mol}\cdot \hbox {m}^{-3}\) and \(278\,\hbox {mol}\cdot \hbox {m}^{-3})\) down to 1.9 K, using the triple point temperature of Ne as a reference temperature. In this study, only the second virial coefficient is taken into account for the single-isotherm fit. Differences between T and the ITS-90 temperature, \(T-T_{90}\), reported in earlier works down to 3 K were confirmed in this study. At the temperatures below 3 K down to 2.5 K, \(T-T_{90}\) is much smaller than the standard combined uncertainty of thermodynamic temperature measurement. However, \(T- T_{90}\) seems to increase with decreasing temperature below 2.5 K down to 1.9 K, although still within the standard combined uncertainty of thermodynamic temperature measurement. In this study, T is obtained also from the CVGT with a single gas density of \(278\,\hbox {mol}\cdot \hbox {m}^{-3}\) using the triple-point temperature of Ne as a reference temperature by making correction for the deviation from the ideal gas using theoretical values of the second and third virial coefficients down to 2.6 K, which is the lowest temperature of the theoretical values of the third virial coefficient. T values obtained using this method agree well with those obtained from the single-isotherm fit. We also found that the second virial coefficient obtained by the single-isotherm fit to experimental results agrees well with that obtained by the single-isotherm fit to the theoretically expected behavior of \(^{3}\)He gas with the theoretical second and third virial coefficients at four gas densities used in the present work.     

Improving the Dynamic Emissivity Measurement Above 1000 K by Extending the Spectral Range

To improve the dynamic emissivity measurement, which is based on the laser-flash method, an array spectrometer is characterized regarding its spectral radiance responsivity for a spectrally resolved emissivity measurement above \(1000\,\)K in the wavelength range between \(550\,\)nm and \(1100\,\)nm. Influences like dark signals, the nonlinearity of the detector, the size-of-source effect, wavelength calibration and the spectral radiance responsivity of the system are investigated to obtain an uncertainty budget for the spectral radiance and emissivity measurements. Uncertainties for the spectral radiance of lower than a relative \(2\,\%\) are achieved for wavelengths longer than \(550\,\)nm. Finally, the spectral emissivity of a graphite sample was determined in the temperature range between \(1000\,\)K and \(1700\,\)K, and the experimental data show a good repeatability and agreement with literature data.     

Small Multiple Fixed-Point Cell as Calibration Reference for a Dry Block Calibrator

A small multiple fixed-point cell (SMFPC) was designed to be used as in situ calibration reference of the internal temperature sensor of a dry block calibrator, which would allow its traceable calibration to the International Temperature Scale of 1990 (ITS-90) in the operating range of the block calibrator from \(70\,^{\circ }\hbox {C}\) to \(430\,^{\circ }\hbox {C}\). The ITS-90 knows in this temperature range, three fixed-point materials (FPM) indium, tin and zinc, with their respective fixed-point temperatures (\(\vartheta _\mathrm {FP}\)), In (\(\vartheta _\mathrm {FP}\,{=}\,156.5985\,^{\circ }\hbox {C}\)), Sn (\(\vartheta _\mathrm {FP}\,{=}\,231.928\,^{\circ }\hbox {C}\)) and Zn (\(\vartheta _\mathrm {FP}\,{=}\,419.527\,^{\circ }\hbox {C}\)). All of these FPM are contained in the SMFPC in a separate chamber, respectively. This paper shows the result of temperature measurements carried out in the cell within a period of 16 months. The test setup used here has thermal properties similar to the dry block calibrator. The aim was to verify the metrological properties and functionality of the SMFPC for the proposed application.     

Variable Temperature Blackbodies via Variable Conductance: Thermal Design,Modelling and Testing

This paper presents the overall design for large (\(\sim \)400 mm aperture) reference blackbody cavities currently under development at the Science and Technology Facilities Council Rutherford Appleton Laboratory Space Department (STFC RAL Space), in collaboration with the National Physical Laboratory (NPL). These blackbodies are designed to operate in vacuum over a temperature range from 160 K to 370 K, with an additional capability to operate at \(\sim \)100 K as a point of near-zero radiance. This is a challenging problem for a single blackbody. The novel thermal design presented in this paper enables one target that can physically achieve and operate successfully at both thermal extremes, whilst also meeting stringent temperature gradient requirements. The overall blackbody design is based upon a helium gas-gap heat switch and modified to allow for variable thermal conductance. The blackbody design consists of three main concentric cylinder components—an inner cavity (aluminium alloy), a radiation shield (aluminium) and an outer liquid nitrogen (\(\hbox {LN}_{2}\)) jacket (stainless steel). The internal surface of the cavity is the effective radiating surface. There is a helium gas interspace surrounding the radiation shield and enclosed by the \(\hbox {LN}_{2}\) jacket and the inner cavity. The blackbodies are now at a mature stage of development. In this paper, the overall design, focusing upon the thermal design solution, is detailed. This paper will also concern the full-scale prototype breadboard model, for which results on thermal stability, spatial gradients and other sensitivities will be presented.     

Calibration of a Photodiode Array Spectrometer Against the Copper Point

This paper describes a method to calibrate photodiode array spectrometers in the spectral radiance mode using a fixed-point blackbody as a reference source. Fixed-point blackbodies are characterized by their excellent emissivity, uniformity, and stability, which make them superior to both conventional standard lamps and variable temperature blackbodies. The temperature of these fixed points is accurately determined being traceable to either the International Temperature Scale (ITS-90) or thermodynamically through radiometric standards. The potential advantage of the fixed-point traceability chain is that it can be universally reproduced without recourse to any hierarchical calibrations or standards. The paper presents the calibration system and discusses the limitations of such an approach. The method used obtained an uncertainty of around 1.4 % ( \(k = 2\) ) associated with radiance responsivity across the spectral region from 550 nm to 1050 nm, which is comparable to what is readily achieved with a lamp-tile or lamp-illuminated spherical source.     

Comparison of a Detector-Based Near-IR Radiance Scale to an ITS-90 Calibrated Radiation Thermometer

Integrating-sphere-input InGaAs radiometers (ISIR) have been developed at the National Institute of Standards and Technology (NIST) to extend the detector-based calibration of radiation thermometers from the Si range to the near-infrared (NIR). These near-infrared radiometers are used to determine the reference spectral irradiance responsivity scale based on the primary-standard cryogenic radiometer. The irradiance responsivity scale is then propagated to spectral radiance at the exit port of an integrating sphere. The near-infrared radiation thermometer (NIRT) is calibrated using this detector-based radiance scale. The first phase of this research work is reported here where the relative spectral radiance responsivity of the NIRT has been determined using a monochromator-based system. Thereafter, the relative spectral responsivity of the NIRT is converted into an absolute responsivity using the radiances from the Zn fixed point blackbody. Then, the NIRT is used to extend these calibrations for temperature measurements between 157 °C and 1000 °C. The NIRT has also been calibrated in this temperature range using the five, fixed point blackbodies of the ITS-90. The two different calibration approaches for temperature measurements are compared.     

Synthesis,structure and thermoelectric properties of $$\mathrm{La}_{1-x}\mathrm{Na}_{x}\mathrm{CoO}_{3 }$$ perovskite oxides

Monovalent ion doped lanthanum cobaltate \(\hbox {La}_{1-x}\hbox {Na}_{x}\hbox {CoO}_{3 }\) (\(0 \le x \le 0.25\)) compositions were synthesized by the nitrate–citrate gel combustion method. All the heat treatments were limited to below 1123 K, in order to retain the Na stoichiometry. Structural parameters for all the compounds were confirmed by the Rietveld refinement method using powder X-ray diffraction (XRD) data and exhibit the rhombhohedral crystal structure with space group R-3c (No. 167). The scanning electron microscopy study reveals that the particles are spherical in shape and sizes, in the range of 0.2–0.5 \(\upmu \)m. High temperature electrical resistivity, Seebeck coefficient and thermal conductivity measurements were performed on the high density hot pressed pellets in the temperature range of 300–800 K, which exhibit p-type conductivity of pristine and doped compositions. The X-ray photoelectron spectroscopy (XPS) studies confirm the monotonous increase in \(\hbox {Co}^{4+}\) with doping concentration up to \(x = 0.15\), which is correlated with the electrical resistivity and Seebeck coefficient values of the samples. The highest power factor of \(10~\upmu \hbox {W~mK}^{-2 }\) is achieved for 10 at% Na content at 600 K. Thermoelectric figure of merit is estimated to be \({\sim }1 \times 10^{-2}\) at 780 K for 15 at% Na-doped samples.     

Thermo-transport properties of Zn-substituted layered Li-nickel oxide, $$\hbox {LiNiO}_{2}$$

The layered Li-TM-\(\hbox {O}_{2}\) materials have been investigated extensively due to their application as cathodes in Li batteries. The electrical properties of these oxides can be tuned or controlled either by non-stoichiometry or substitution. Hence the thermo-transport properties of Zn-substituted \(\hbox {LiNi}_{1-x}\hbox {Zn}_{x}\hbox {O}_{2}\) for \(0 \le x \le 0.16\) have been investigated in the temperature range of 300–900 K for potential application as a high-temperature thermoelectric material. For \(x < 0.08\), the compounds were of single phase belonging to the space group R-3mH while for \(x > 0.08\) an additional minority phase, ZnO forms together with the main layered phase. All the compounds exhibit a semiconducting behaviour with electrical resistivity, varying in the range of  \(\sim 10^{-4}\) to \(10^{-2}\,\,\Omega \hbox {m}\) between 300 and 900 K. The electrical resistivity is found to increase with increasing Zn-substitution predominantly due to a decrease in the charge carrier hole mobility. The activation energy remains constant, \(\sim \)10  meV, with Zn-substitution. The Seebeck coefficient of the compounds is found to decrease with increasing temperature and increase with increasing Zn-substitution. The Seebeck coefficient decreases from \(\sim \)95 to \(35\ \upmu \hbox {V K}^{-1}\) and the corresponding power factor is \(\sim \)12\(\ \upmu \hbox {W m}^{-1}\ {\hbox {K}}^{-2}\) for the \(x = 0.16\) compound.     

High-Accuracy Emissivity Data on the Coatings Nextel 811-21, Herberts 1534, Aeroglaze Z306 and Acktar Fractal Black

The Physikalisch-Technische Bundesanstalt determined the directional spectral emissivities of several widely used black coatings: Nextel 811-21, Herberts 1534, Aeroglaze Z306 and Acktar Fractal Black. These are and were often applied in different industrial and scientific applications. The measurements are taken angularly resolved over a range from \(10{^{\circ }}\) to \(70{^{\circ }}\). They cover the temperature range typical for the application of the respective coating and a wide wavelength range from \(4~\upmu \hbox {m}\) to \(100~\upmu \hbox {m}\). The respective directional total emissivities and hemispherical total emissivities are given as well. The measurements were taken under vacuum at the reduced background calibration facility to achieve low uncertainties and avoid atmospheric interferences. Additionally, some measurements were taken with the emissivity measurement setup in air.     

Temperature and Heat Flow Rate Calibration of a Calvet Calorimeter from $$0\,{^{\circ }}\hbox {C}$$ to $$190 \,{^{\circ }}\hbox {C}$$19

This study describes the temperature and heat flow rate calibrations of a Calvet calorimeter (SETARAM, BT2.15) in the temperature range of 0–190 \({^{\circ }}\hbox {C}\). Temperature calibration is carried out using three reference materials, namely water, gallium, and indium, as specified in the International Temperature Scale of 1990 (ITS-90). The sample temperature of the Calvet calorimeter is corrected by the obtained mean value, \(-0.489 \,{^{\circ }}\hbox {C}\), of the measured extrapolated peak onset temperature (\(T_{e})\) when the heating rate (\(\upbeta )\) is zero (\(\Delta T_\mathrm{corr }(\upbeta ~=~0\))). The heat flow rate is calibrated using a reference material with a known heat capacity, namely SRM 720 \(\alpha \)-\(\hbox {Al}_{2}\hbox {O}_{3}\) (synthetic sapphire), which is traceable to the National Institute of Standards and Technology. From the heat flow rate measurements of the blank baseline and SRM 720, the proportional calibration factor, \(\hbox {K}_{\Phi }\), in the 0–190\( \,{^{\circ }}\hbox {C}\) temperature range was determined. The specific heat capacity of copper was measured with the obtained calibration values, and the measured data show consistency with the reference value.     

Design and Investigation of Pd–C Eutectic Fixed-Point Cells for Thermocouple Calibration at NMIA

The calibration of Pt/Rh thermocouples up to 1560 \(^{\circ }\hbox {C}\) at NMIA currently uses the conventional ‘melt-wire technique’ to realize Gold (Au) and Palladium (Pd) melting points, resulting in the loss of 20 mm of wire from the junction end for each calibration. To avoid this loss, NMIA intends to replace the melt-wire technique with the use of miniature fixed-point cells. NMIA has established Copper (Cu) and Cobalt–Carbon (Co–C) eutectic cells for calibration of thermocouples to 1324 \(^{\circ }\hbox {C}\). To extend the calibration up to 1500 \(^{\circ }\hbox {C}\), miniature Palladium–Carbon (Pd–C) eutectic cells (1492 \(^{\circ }\hbox {C}\)) have been constructed and tested in collaboration with NMIJ, AIST. Although these cells are made of high-purity reference materials, careful consideration must be given to contamination introduced during the manufacture and filling of the crucibles and by their long-term use. These issues can only be assessed by measurement of cell-to-cell temperature differences within the ensemble of cells traceable to ITS-90. In the work presented here, 3 NMIA-design mini Pd–C cells were constructed: 1 at NMIA and 2 at NMIJ. These cells were compared, together with a “large” NMIJ Pd–C cell, using type-R, type-B and Pt/Pd thermocouples and radiation thermometry. Although the cells are found to be stable and repeatable, significant problems arising from migration of Pd to the thermocouples were identified.     

Development of a 300 L Calibration Bath for Oceanographic Thermometers

The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has been developing a 300 L calibration bath to calibrate 24 oceanographic thermometers (OT) simultaneously and thereby reduce the calibration work load necessary to service more than 180 OT every year. This study investigated characteristics of the developed 300 L calibration bath using a SBE 3plus thermometer produced by an OT manufacturer. We also used 11 thermistor thermometers that were calibrated to be traceable to the international temperature scale of 1990 (ITS-90) within 1 mK of standard uncertainty through collaboration of JAMSTEC and NMIJ/AIST. Results show that the time stability of temperature of the developed bath was within \(\pm 1 \,\hbox {mK}\). Furthermore, the temperature uniformity was \(\pm 1.3 \,\hbox {mK}\). The expanded uncertainty (\(k=2\)) components for the characteristics of the developed 300 L calibration bath were estimated as 2.9 mK, which is much less than the value of 10 mK: the required specification for uncertainty of calibration for the OT. These results demonstrated the utility of this 300 L calibration bath as a device for use with a new calibration system.     

Hydrothermal growth of wheatear-shaped ZnO microstructures and their photocatalytic activity

A facile hydrothermal process was developed to synthesize novel wheatear-shaped ZnO microstructures at a low temperature (\(85^{\circ }\hbox {C}\)) without the assistance of any template agent. X-ray diffraction and field emission scanning electron microscopy were used to characterize the structure and morphology of the samples. Results showed that the length of the ‘wheatear’ was about \(5.8~\upmu \!\hbox {m}\) and the section width was \(1.2~\upmu \!\hbox {m}\). The particles consisted of closely packed nanorods with average diameter of 100 nm. The growth of wheatear-shaped ZnO is very rapid and can be achieved in only 5 min. \(\hbox {OH}^{-}\)-driven oriented aggregation and multistep nucleation resulted in the formation of wheatear-shaped ZnO microstructures. The product had assembled open structures and it exhibited excellent photocatalytic activity in the degradation of methyl orange under UV-light irradiation.