High-temperature Measurements Research Articles

Synergistic Entropy Engineering with Oxygen Vacancy: Modulating Microstructure for Extraordinary Thermosensitive Property in ReNbO4 Materials.

The pursuit of high precision and stability simultaneously in high-temperature thermistor fields is longstanding. However, most spinel or perovskite-structured thermosensitive materials struggle to tolerate prolonged high-temperature environments at the expense of sensitivity and stability. Here, a novel entropy engineering strategy involving vacancies is proposed to balance sensitivity and stability for fergusonite-structured ReNbO4 (Re is a rare earth element) material in extreme environments. The synergistic effect of entropy stabilization and allovalent substitution on the A-site generates unusually high concentrations of oxygen vacancy that improves the electronic structure and structural stability. Moreover, entropy engineering involving oxygen vacancies introduces potent and stable microstructural features including twinned domains, lattice distortion, and lattice reconfigurations, which facilitate stability and accuracy at a wide temperature range, thereby synergistically contributing to excellent thermosensitive properties. As-prepared high-entropy ceramics show low aging drift rates and high-temperature measurement accuracy over the extended temperature range of 223-1423 K, exhibiting a competitive temperature coefficient of resistivity of 0.223%/K at 1423 K. This work not only provides valuable insights into the design of high-temperature thermosensitive sensors but also establishes an effective paradigm for entropy engineering involving vacancies.

Sensing characteristics of integrated fiber Bragg grating sensors for high-temperature strain measurement

Sensing characteristics of integrated fiber Bragg grating sensors for high-temperature strain measurement

Numerical simulation of flow field in continuous casting slab mould under EMS conditions assisted with high-temperature quantitative velocity measurement

Numerical simulation of flow field in continuous casting slab mould under EMS conditions assisted with high-temperature quantitative velocity measurement

A High-Temperature and Wide-Permittivity Range Measurement System Based on Ridge Waveguide.

Potential applications of microwave energy, a developed form of clean energy, are diverse and extensive. To expand the applications of microwave heating in the metallurgical field, it is essential to obtain the permittivity of ores throughout the heating process. This paper presents the design of a 2.45 GHz ridge waveguide apparatus based on the transmission/reflection method to measure permittivity, which constitutes a system capable of measuring the complex relative permittivity of the material under test with a wide temperature range from room temperature up to 1100 °C. The experimental results indicate that the system is capable of performing rapid measurements during the heating process. Furthermore, the system is capable of accurately measuring dielectric properties when the real part of the permittivity and the loss tangent vary widely. This measurement system is suitable for high-temperature dielectric property measurements and has potential applications in microwave-assisted metallurgy.

Crystal structure and elastic properties of parabreyite: a new high-pressure ring silicate in the CaSiO3 system

Abstract. The CaSiO3 system exhibits notable structural complexity, featuring different polymorphs and polytypes across various pressure (P) and temperature (T) conditions compatible with Earth's environments. Among these, the pseudowollastonite and breyite structures are characterized by the presence of threefold tetrahedral rings. In this study, we conducted multianvil syntheses in the pressure and temperature range 4–5 GPa and 600–800 °C to stabilize crystals of a new high-pressure polymorph reported by Chatterjee et al. (1984) and obtain structural information. The structure was solved by combining 3D electron diffraction (ED) and synchrotron single-crystal X-ray diffraction (SC-XRD). The new high-pressure polymorph, here referred to as parabreyite, features threefold tetrahedral rings, with a different configuration compared to breyite. Parabreyite is triclinic, P1‾, with unit cell parameters a= 8.1911(10) Å, b= 9.3441(9) Å, c= 10.4604(10) Å, α= 73.901(8)°, β= 89.814(9)° and γ= 77.513(9)°. The bulk modulus, K0= 90.7(5) GPa, was determined by an in situ SC-XRD experiment using a diamond anvil cell (DAC) in the pressure interval 0–10 GPa. Thermal expansion was also determined by low- and high-temperature SC-XRD measurements and resulted in a larger value compared to breyite. Additionally, we performed in situ synchrotron SC-XRD on synthetic pseudowollastonite in the pressure interval 0–14 GPa and did not observe any structural phase transition in this ring-type polymorph. We also report the differences between the Raman spectra of parabreyite and breyite to help with the in situ identification of these polymorphs. The threefold ring topology of parabreyite suggests a new configuration for high-density tetrahedra structures, with significant implications for the prediction of high-pressure sp3 carbonates.

Sapphire fiber Bragg gratings array demodulated with the multi-peak auto-tracking algorithm for quasi-distributed high-temperature measurement.

Sapphire fiber Bragg gratings (SFBGs) are promising high-temperature sensors in many harsh environments, such as aviation, nuclear power, and furnaces. Here, we proposed and experimentally demonstrated a quasi-distributed high-temperature sensor based on an SFBG array sealed in an argon gas-infiltrated sapphire tube interrogated by using an InGaAs-based interrogator. An SFBG array including five SFBGs was inscribed using the femtosecond laser line-by-line method and sealed in an argon gas-infiltrated sapphire tube. A multi-peak auto-tracking algorithm, including the Hilbert transform and cross correlation algorithm (CCA), was employed to demodulate the array. The Hilbert transform method is introduced for the segmentation of the peak region in the reflection spectrum. The CCA was used to obtain the Bragg wavelength shift of each SFBG reflection peak. Then, we investigated the stability in demodulation of the SFBG array, and the result shows that Bragg wavelength dispersion is less than ±12 pm, which indicates that the interrogator and the proposed algorithm exhibit high accuracy and stability. Moreover, the SFBG array was calculated at high temperatures up to 1676 °C, and the thermal response curves of the SFBG array were obtained. Furthermore, the temperature distribution measurement of the blackbody radiation source was successfully carried out using the calibrated SFBGs array sensor, with a maximum test temperature of 1900 °C. Therefore, such a quasi-distributed high-temperature sensing system, including an SFBG array, interrogator, and multi-peak detection algorithm, is promising in applications with thermal gradients, such as metallurgical, aviation, and nuclear power industries.

Nanolite Crystallization in Volcanic Glasses: Insights From High‐Temperature Raman Spectroscopy and Low‐Temperature Rock‐Magnetic Analysis

AbstractHigh‐temperature Raman spectroscopy offers a cost‐effective alternative to extensive infrastructure and sensitive instrumentation for investigating nanolite crystallization in undercooled volcanic melts, a key area of interest in volcanology. This study examined nanolite formation in anhydrous andesite melts in situ at high temperatures, identifying distinct Raman peaks at 310 and 670 cm−1 appearing above the glass transition temperature. The initial amorphous glass remained stable up to 655°C, beyond which Fe‐Ti‐oxide nanolites progressively formed at higher temperatures, as also confirmed by complementary XRD analysis. The evolution of the 310 cm−1 peak depends only on the magnitude of nanolite crystallization, while the intensity of the 670 cm−1 peak is temperature‐dependent and challenging to observe above 500°C. Complementary low‐temperature rock‐magnetic analyses confirmed Fe‐Ti‐oxide nanocrystallization with nanolites around 20 nm in diameter. The study tested lasers of different wavelengths (from 355 to 514 nm) and found the green laser to be the most effective for collecting spectra at both room and high temperature. However, above 720°C, black body radiation significantly hinders Raman observation with the green laser when using a non‐confocal setup and analyzing poorly transparent samples. If higher temperature measurements are desired, switching to a confocal setup and using lower wavelength lasers should be considered. This research offers a protocol for studying nanolite formation and melt dynamics at high temperatures, providing a foundation for future studies of volcanic processes.

FBG in coreless silica fiber for high temperature measurements

The paper demonstrates for the first time the possibility of measuring high temperatures up to 1200 °C using an FBG with central wavelength 985 nm formed in a coreless pure silica fiber using the femtosecond point-by-point FBG-writing technique. In our case, the length of the coreless fiber from the FBG to the connection with the multimode transport fiber was not less than 50 cm, and average temperature sensitivity was about 9 pm/°C. It is shown that such an FBG remains stable at temperatures up to 1150 °C for at least an hour. At 1200 °C, degradation of the reflectivity was observed. The use of a fully multimode interrogation scheme made it possible to significantly increase the intensity of reflected light and reduce the effect of mode interference on the obtained FBG spectrum, and the choice of a spectral range of up to 1100 nm makes it possible to use relatively inexpensive spectral devices based on silicon photodetectors.

High-temperature measurements of acetylene VUV absorption cross sections and application to warm exoplanet atmospheres

Most observed exoplanets have high equilibrium temperatures (T$_ eq $ > 500 K). Understanding the chemistry of their atmospheres and interpreting their observations requires the use of chemical kinetic models including photochemistry. The thermal dependence of the vacuum ultraviolet (VUV) absorption cross sections of molecules used in these models is poorly known at high temperatures, leading to uncertainties in the resulting abundance profiles. The aim of our work is to study experimentally the thermal dependence of VUV absorption cross sections of molecules of interest for exoplanet atmospheres and provide accurate data for use in atmospheric models. This study focuses on acetylene (C$_ $H$_ We measured absorption cross sections of C$_ $H$_ $ at seven temperatures ranging from 296 to 773 K recorded in the 115-230 nm spectral domain using VUV spectroscopy and synchrotron radiation. These data were used in our 1D thermo-photochemical model, to assess their impact on the predicted composition of a generic hot Jupiter-like exoplanet atmosphere. The absolute absorption cross sections of C$_ $H$_ $ increase with temperature. This increase is relatively constant from 115 to 185 nm and rises sharply from 185 to 230 nm. The abundance profile of C$_ $H$_ $ calculated using the model shows a slight variation, with a maximum decrease of 40<!PCT!> near 5 times 10$^ $ bar, when using C$_ $H$_ $ absorption cross sections measured at 773 K compared to those at 296 K. This is explained by the absorption, higher in the atmosphere, of the actinic flux from 150 to 230 nm due to the increase in the C$_ $H$_ $ absorption in this spectral range. This change also impacts the abundance profiles of other by-products such as methane (CH$_ $) and ethylene (C$_ $H$_ We present the first experimental measurements of the VUV absorption cross sections of C$_ $H$_ $ at high temperatures. Similar studies of other major species are needed to improve our understanding of exoplanet atmospheres.

High-Entropy Thermistor Ceramics (La1/3Nd1/3M1/3)2(Zr1/2Sn1/2)2O7 (M = Sm, Eu, Gd, or Dy) with High Sensitivity for High-Temperature Measurements.

A series of high-entropy pyrochlore ceramics, specifically (La1/3Nd1/3M1/3)2(Zn1/2Sn1/2)2O7 (M = Sm, Eu, Gd, or Dy), have been synthesized using the solid-state reaction method. Their potential as high-temperature thermistors was investigated by analyzing electrical and aging properties at elevated temperatures. Characterization using X-ray diffraction, scanning electron microscopy, and Raman spectroscopy confirms that these ceramics are dense, single-phase solid solutions with a pyrochlore structure. Electrical analysis demonstrate that these ceramics maintain high resistivity and resistance stability, exhibiting typical negative temperature coefficient features and high B values across a wide temperature range. These characteristics make (La1/3Nd1/3M1/3)2(Zn1/2Sn1/2)2O7 promising candidates for the development of high-sensitivity, long-life high-temperature thermistors suitable for applications within the temperature range of 400-1200 °C.

Thermochemical investigation of three 5-R-thio-1,3,4-thiadiazole derivatives: R = methyl, ethyl

An experimental and computational thermochemical study is reported focus on the relationship between the energetic properties, the structural characteristics and the inherent reactivity of three thiothiadiazoles: 2-amino-5-(methylthio-)-1,3,4-thiadiazole, 2-amino-5-(ethylthio-)-1,3,4-thiadiazole and 2-mercapto-5-methylthio-1,3,4-thiadiazole. From the DSC measurements, the enthalpies of fusion and the respective onset temperatures were determined. The standard molar energies of combustion of the (alkylthio)-1,3,4-thiadiazoles were determined by rotating bomb combustion calorimetry. The corresponding standard molar enthalpies of sublimation, at T = 298.15 K, were derived from high-temperature Calvet microcalorimetry measurements and the study of the dependence of the compound’s vapour pressures with the temperature, using the Knudsen-effusion technique. The combination of these experimental results enables the calculation of the standard molar enthalpies of formation in the gaseous state, at T = 298.15 K, which are discussed in terms of structural contributions. The latter property was also determined from high-level ab initio molecular orbital calculations at the G3(MP2)//B3LYP level of theory. The computed values are in good agreement with the experimental ones. In addition, a conformational and tautomeric study was conducted using the same approach, in order to provide insight on the amino/imino and thiol/thione tautomerism of the compounds studied. The amino form predominates in amino-thiadiazoles, while the thione form prevails in mercaptothiadiazole. Moreover, the relative thermodynamic stability of each compound was also evaluated showing that in both solid and gas phases, the most stable species is the mercaptothiadiazole (in its thione form). The thermochemical results of the (alkylthio)-1,3,4-thiadiazoles show a good agreement with the NBO (natural bond orbitals) analysis results.

Enhanced thermoelectric properties in Cu₁.₈Se thin films: Achieving superior power factor through phase control and optimal deposition temperature

Thermoelectric thin films are vital for efficient energy conversion and thermal management. XRD analysis reveals that Cu₁.₈Se films exhibit a mixed α-phase when deposited at room temperature, 100 °C, and 300 °C, but transition to a pure β-phase at 200 °C. The formation of the pure β-Cu₁.₈Se phase at 200 °C significantly improves the crystallinity of the films. Increased annealing temperatures lead to greater surface roughness and grain size as observed by AFM and FESEM. Electrical conductivity decreases with higher measurement temperatures, reflecting degenerate semiconductor behavior due to Cu vacancies. The sample deposited at 200 °C, exhibiting the pure β-phase, achieves the highest power factor of 5456 μWm⁻1K⁻2 and improved Seebeck coefficient, underscoring the importance of phase purity and controlled surface roughness for optimal thermoelectric performance.

AI-powered ultrasonic thermometry for HIFU therapy in deep organ

High-intensity focused ultrasound (HIFU) is considered as an important non-invasive way for tumor ablation in deep organs. However, accurate real-time monitoring of the temperature field within HIFU focal area remains a challenge. Although ultrasound technology, compared with other approaches, is a good choice for noninvasive and real-time monitoring on the temperature distribution, traditional ultrasonic thermometry mainly relies on the backscattered signal, which is difficult for high temperature (>50 °C) measurement. Given that artificial intelligence (AI) shows significant potential for biomedical applications, we propose an AI-powered ultrasonic thermometry using an end-to-end deep neural network termed Breath-guided Multimodal Teacher-Student (BMTS), which possesses the capability to elucidate the interaction between HIFU and complex heterogeneous biological media. It has been demonstrated experimentally that two-dimension temperature distribution within HIFU focal area in deep organ can be accurately reconstructed with an average error and a frame speed of 0.8 °C and 0.37 s, respectively. Most importantly, the maximum measurable temperature for ultrasonic technology has been successfully expanded to a record value of 67 °C. This breakthrough indicates that the development of AI-powered ultrasonic thermometry is beneficial for precise HIFU therapy planning in the future.

In situ high-temperature emissivity measurements of heat-treated, silicon coated stainless steel for solar thermal applications

Understanding thermal emissivity at high temperatures is crucial for developing efficient materials for solar thermal applications. We present a new approach for creating an efficient material for solar absorber by developing a nano structured surface on stainless steel substrate through Si deposition and annealing. We prepare five samples by annealing them at five temperatures between 700 °C and 1100 °C. Afterwards, we perform a systematic study of the spectral emissivity at elevated temperatures, focusing on different parameters: angle dependence, wavelength dependence, and temperature dependence. The spectral directional emissivity experiments performed in the mid-infrared range reveal a dielectric behavior of the samples in the short wavelength region (λ < 6 μm) and metallic behavior in the long wavelength region (λ > 12 μm). The results indicate an increase in hemispherical and total normal emissivity with measurement temperature (from 200 °C to 700 °C), influenced by oxide/silicide formation due to interdiffusion, and by surface roughness. Notably, samples annealed at 900 °C and 1000 °C demonstrate enhanced thermal stability at 700 °C, showcasing promising characteristics for high-temperature applications. Consequently, this study presents a viable method for developing cost-effective silicon-based solar absorber coatings on stainless steel with tailored properties for solar thermal applications along with its real time high temperature emissivity details.

High temperature thermoelectric properties of BaxSr2−xFeCoO6 double perovskites

Abstract In this study, environmentally benign BaxSr2-xFeCoO6 (BSFC) double perovskites are synthesized via solid-state reaction route for high-temperature thermoelectric applications. The crystal structure and morphology of the ceramic samples are analyzed using XRD and SEM, respectively. Rietveld refinement of XRD data confirms a cubic structure with Pm3̅m space-group. High-temperature thermoelectric measurements exhibits that substituting Ba for Sr in Sr2FeCoO6 increases the Seebeck coefficient (S) but at the expense of the electrical conductivity (σ). The highest Seebeck coefficient of 117 μV/K has been observed in Ba0.5Sr1.5FeCoO6 at 910 K. Temperature-dependent electrical conductivity measurements indicates a semiconductor-to-metal like transition in all samples, with BSFC (x = 0.1) achieving the highest conductivity of 4 × 104 S m−1 at ∼623 K. The thermoelectric power factor has been enhanced by over 50% with Ba substitution in Sr2FeCoO6. Electron transport in these double perovskites is found to follow the small polaron hopping conduction mechanism.

Remarkable Near-Infrared Temperature Sensing Properties of Y3Ga5O12:Cr3+ and Y3Ga5O12:Cr3+/Yb3+ Nanotubes Fabricated via a Single-Needle Electrospinning Technique.

For the first time, nanotubes of Y3Ga5O12:Cr3+ (referred to as YGO:Cr3+) and Y3Ga5O12:Cr3+/Yb3+ (referred to as YGO:Cr3+/Yb3+) were produced via a single-needle electrospinning method. The nanotubes of YGO:Cr3+ and YGO:Cr3+/Yb3+ have outer diameters between 190 and 210 nm, whereas the inner diameter ranges between 70 and 80 nm, and the wall thickness ranges from 50 to 60 nm. The temperature sensitivity of YGO:0.02Cr3+ nanotubes was examined by studying how the Cr3+ lifetime changes with temperature. In the temperature range of 303 to 723 K, the peak values of Sa and Sr were 0.274 and 0.0067 K-1, respectively. Temperature sensing properties of YGO:0.02Cr3+/yYb3+ (y = 0.01, 0.02, and 0.05) nanotubes were evaluated via the FIR technique utilizing nonthermally coupled energy levels. The I970/I708 in the YGO:0.05Cr3+/0.01Yb3+ nanotubes displayed a maximal Sr value of 0.013 K-1 at 633 K, which exceeds that of other Cr3+-doped NIR phosphors previously reported and is promising for high-temperature measurements.

High-temperature structure, elasticity, and thermal expansion of ε-ZrH1.8

Zirconium hydride is a promising candidate material for nuclear microreactor applications as a solid-state moderator component, owing to its favorable neutronics properties and good thermal stability over other metal hydrides. In the present work, the crystal structure, thermal expansion, and elastic properties of the hydrogen-rich ε phase hydride were measured at elevated temperatures in the range 300–900 K. Samples were prepared by direct hydriding Zircaloy-4 metal – a nuclear-grade zirconium alloy. Room-temperature lattice parameters agree well with those reported from literature for unalloyed zirconium hydride and fall within an observed quadratic H-content dependence. The coefficients of thermal expansion, determined from lattice expansion and dilatometry, agree well within our work but were about 30 % lower than those reported by others for unalloyed hydrides. Density functional theory-based molecular dynamics simulations were used to compare with thermal expansion and elasticity measurements. Results showed lattice parameter temperature dependence and slope of thermal expansion align with those from measurements. Based on diffraction scans at select temperatures, ε phase remained stable in air up to at least 770 K. Likewise, dilatometry showed smooth thermal expansion up to the thermal decomposition temperature around 950 K. The precise decomposition temperature was not determined via diffraction due to sparse scanning. The complete elastic property measurements were gathered for ε-phase Ziracloy-4 hydride for the first time. Young's modulus was lower compared to the metal and δ hydride phases. High-temperature elasticity measurements were limited to <350 K due to acoustic dissipation effects.

Influence of Silicon-Based Photoelectric Material Spectral Characteristics on Radiation Spectroscopy Thermometry

To research the influence of the photoelectric response characteristics of radiation thermometry, a high-temperature blackbody radiation spectrum measurement experimental system is built by using the standard blackbody furnace, optical-fiber spectrometer with silicon-based photoelectric detection material. By setting different integration times of the spectrometer, the standard blackbody radiation spectrum measurement at different temperatures is carried out. The influence of the photoelectric response characteristics parameters is analyzed in detail. Therefore, the linear range between fitting band and spectral response intensity of radiation spectrum thermometry parameters is optimized. On this basis, through the standard blackbody radiation temperature measurement, the influence of the optimal parameter fitting band and the linear interval of spectral response intensity on the radiation temperature measurement results are verified. The influence of the mentioned photoelectric detection response characteristics on the spectral radiation thermometry has an important reference value for improving the accuracy of the spectral radiation thermometry.

High-temperature thin-film strain sensors with low temperature coefficient of resistance and high sensitivity via direct ink writing

High-temperature thin-film strain sensors are advanced technological devices for monitoring stress and strain in extreme environments, but the coupling of temperature and strain at high temperature is a challenge for their use. Here, this issue is addressed by creating a composite ink that combines Pb2Ru2O6 and TiB2 using polysilazane (PSZ) as a binder. After direct writing and annealing the PSZ/Pb2Ru2O6/TiB2 film at 800 °C in air, the resulting thin film exhibits a low temperature coefficient of resistance (TCR) of only 281 ppm/°C over a wide temperature range from 100 °C to 700 °C, while also demonstrating high sensitivity with a gauge factor approaching 19.8. This exceptional performance is attributed to the intrinsic properties of Pb2Ru2O6, which has positive TCR at high temperature, and TiB2, which has negative TCR at high temperature. Combining these materials reduces the overall TCR of the film. Tests showed that the PSZ/Pb2Ru2O6/TiB2 film maintains stable strain responses and significant signal output even under varying temperature. These findings provide valuable insights for developing high-temperature strain sensors with low TCR and high sensitivity, highlighting their potential for applications in high-temperature strain measurements.

Development of a Novel High Temperature Continuous Particle Mass Flow Measurement Device for Particle-Based CSP Applications

Particle-based concentrating solar power (CSP) technology is one of the generation three (Gen3) CSP technologies that has potential for lowering the levelized cost of electricity produced by this solar thermal power systems. Commercially available ceramic particles, which are rated for high temperature applications up to 1200 °C, were selected for this study. This medium is commonly used as an energy carrier or heat transfer medium in Gen3 CSP research and development efforts [1]. Prior studies at the National Solar Thermal Test Facility (NSTTF) have investigated and evaluated various mass flow measurement methods, and a simple gravimetric temporal load measurement method was chosen as the best candidate for the research purpose [2]. This mass flow measurement method is a batch process and is not a viable solution for commercial-scale power generation applications based on cost, space, process control, and practical system integration factors. In-line and continuous particle mass flow measurement will play an integral role in efficient and cost effective Gen3 CSP particle technologies. Process parameters, including energy absorbed by the particles, receiver efficiency, temperature dependent flow phenomena, and general high temperature measurement reliability are all rely on repeatable and accurate measurement of particle mass flow under various operating conditions. Ceramic particles, like those used in this application, are not conventionally used as an energy carrier. A novel concept for continuous particle mass flow at a wide range of operating temperatures is currently under development and planned to be tested at the NSTTF, called the Particle In-LinE (PILE) mass flow sensor.