High-temperature Measurements Research Articles

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.

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.

YAG:Dy co-doped with Tb for lifetime-based phosphor thermometry from room temperature to 1600 °C

Phosphor thermometry has demonstrated significant potential for nondestructive high-temperature measurements in gas turbines. To expand the measurement range through lifetime-based phosphor thermometry, we developed a novel phosphor, YAG:Dy co-doped with Tb (YAG:Dy,Tb). Three YAG:Dy,Tb samples with varying Tb concentrations were synthesized through the sol–gel method. A fiber-optic-coupled measurement system was established to capture multiple emission peaks of YAG co-doped with Dy3+ and Tb3+ at 544 nm, 484 nm, and 458 nm. Efficient energy transfer from Dy3+ to Tb3+ resulted in a substantial enhancement of Tb3+ emission at 544 nm under 355 nm excitation. Owing to the energy transfer, the temperature measurement range under the lifetime method was extended from room temperature to 1600 °C using the combination of Tb3+ emission at 544 nm and Dy3+ emission at 458 nm. YAG:Dy,Tb samples with higher concentrations of Tb3+ exhibited superior temperature measurement performance, mainly owing to their stronger signal-to-noise ratio at >1000 °C. The performances of different emission peaks were also compared according to temperature uncertainty, which generally ranged from 0.1 °C to 2.7 °C across the entire measurement range.

Temperature dependent stochastic dynamics mass spectrometric analysis of configurationally locked polyenes

This paper derived relation between mass spectrometric variable intensity of analyte peaks and three-dimensional molecular structures of ions toward temperature utilising innovative stochastic dynamics equations, which provide exact analyte quantification and 3D structural analysis and are attractive formulas for modelling of mass spectrometric phenomena. The same equations are opened to develop new relations accounting for temperature; thus, providing argumentation about temperature dependent variables. High-temperature measurement of vapours are important tool, amongst others and use the Arrhenius’s plot. However, there is a variation between experimental and theoretical linear correlation toward temperature; thus, highlighting soft ionisation methods showing significant standard deviations. It could be explained with temperature perturbation of charge values. Descriptive models, so far, provide semi-quantification. This study, first shows validity of new functional model. Straightforwardly, its empirical proof is obtained determining 3D structurally protomers and isotopomers of configurationally locked polyenes via ultra-high resolution electrospray ionization and atmospheric pressure chemical ionization mass spectrometry within the temperature range T=300-450°C. There are used high accuracy quantum chemical static methods, molecular dynamics and chemometrics. There are excellent method performances (|r|=0.99978). The tool could be regarded as an actually honest alternative of available theoretical models.

Novel Surface Acoustic Wave Strain Sensor with Enhanced High-Temperature Performance and Resistance to Aging

Abstract Surface acoustic wave (SAW) sensors based on Langasite (La3Ga5SiO14, LGS) have emerged as promising candidates for high-temperature strain measurement in passive wireless systems. However, limitations of strain transfer at temperatures above 800°C have hindered the repeatability of sensors due to temperature-induced effects. For instance, the aging of conventional high-temperature adhesives at elevated temperatures restricts the strain transfer between the measured object and the sensor. Moreover, materials like Inconel-600 exhibit a coefficient of thermal expansion significantly larger than the LGS, leading to thermal strains caused by thermal expansion mismatch beyond the maximum range of existing SAW strain sensors. Such factors increase the likelihood of sensor damage during a test. In this paper, we present a novel SAW sensor utilizing an ultra-thin LGS substrate encapsulated within a ceramic coating, which transfers strain by exerting pressure on both sides of the sensor. The strain sensor is mounted on an equal-strain beam inside a high-temperature furnace. The ceramic coating is not tightly bonded to the sensor, thereby mitigating the thermal expansion mismatch between the sensor and the beam at high temperatures. Furthermore, the ceramic coating can withstand large strain caused by thermal expansion while maintaining pressure on the sensor. This innovative SAW sensor enables repeat strain tests up to 800°C, including both calibration and formal tests. The measured strain exhibits an error of less than 5% compared to a standard strain gauge, demonstrating the sensor’s enhanced performance and reliability.

Performance Study of F-P Pressure Sensor Based on Three-Wavelength Demodulation: High-Temperature, High-Pressure, and High-Dynamic Measurements.

F-P (Fabry-Perot) pressure sensors have a wide range of potential applications in high-temperature, high-pressure, and high-dynamic environments. However, existing demodulation methods commonly rely on spectrometers, which limits their application to high-frequency pressure signal acquisition. To solve this problem, this study developed a self-compensated, three-wavelength demodulation system composite with an F-P pressure sensor and a thermocouple to construct a comprehensive sensing system. The system produces accurate pressure measurements in high-temperature, high-pressure, and high-dynamic environments. In static testing at room temperature, the sensing system shows excellent linearity, and the pressure sensitivity is 158.48 nm/MPa. In high-temperature testing, the sensing system maintains high linearity in the range of 100 °C to 700 °C, with a maximum pressure-indication error of about 0.13 MPa (0~5 MPa). In dynamic testing, the sensor exhibits good response characteristics at 1000 Hz and 5000 Hz sinusoidal pressure frequencies, with a signal-to-noise ratio (SNR) greater than 37 dB and 45 dB, respectively. These results indicate that the sensing system proposed in this study has significant competitive advantages in the field of high-temperature, high-speed, and high-precision pressure measurements and provides an important experimental basis and theoretical support for technological progress in related fields.

Design and characterization of the time-resolved opacity spectrometer (OpSpecTR) for the NIF iron opacity campaign.

A new time-resolved opacity spectrometer (OpSpecTR) is currently under development for the National Ignition Facility (NIF) opacity campaign. The spectrometer utilizes Icarus version 2 (IV2) hybridized complementary metal-oxide-semiconductor sensors to collect gated data at the time of the opacity transmission signal, unlocking the ability to collect higher-temperature measurements on NIF. Experimental conditions to achieve higher temperatures are feasible; however, backgrounds will dominate the data collected by the current time-integrating opacity spectrometer. The shortest available OpSpecTR integration time of ∼2ns is predicted to reduce self-emission and other late-time backgrounds by up to 80%. Initially, three Icarus sensors will be used to collect data in the self-emission, backlighter, and absorption regions of the transmission spectrum, with plans to upgrade to five Daedalus sensors in future implementations with integration times of ∼1.3ns. We present the details of the diagnostic design along with recent characterization results of the IV2 sensors.

Evolution of the Pd0/PdO phase change on Pd-MCM-41 catalyst for efficient production of furfural from the fast pyrolysis of cellulose

Furfural (C5H4O2) is a high-value platform chemical that is traditionally derived from the solvolysis of hemicellulose. However, its production from pyrolysis is far from satisfactory. In particular, the abundant cellulose within lignocellulosic biomass has yet to be successfully upgraded into furfural. Consequently, the overall yield of furfural from a lignocellulosic biomass is extremely low. Herein, we report a facile heterogeneous catalyst prepared from a simple impregnation of palladium (Pd) onto MCM-41 mesoporous silica. The catalyst demonstrated a remarkably high selectivity of ∼58.5% and yield of ∼32.5 wt% for furfural from the fast pyrolysis of wet cellulose. It was also confirmed to reach a selectivity of 65.4% and yield of 44.5 wt% for furfural from wet xylan, as well as a furfural yield of 23.9 wt% from wet sugarcane bagasse. All these values are superior to the literature reports. Through advanced characterisation including in-situ synchrotron high-temperature XRD and DRIFTS measurement, the loading of Pd in a tiny quantity of 1 mol% was confirmed to be sufficient in enhancing the surface hydrophilicity of the MCM-41 support, promoting the adsorption of reactants especially the formaldehyde group (HCHO), as well as the desorption of the target product furfural. In addition, Pd oxide (i.e., Pd2+O) was confirmed to be the catalytic active site. However, it was partly reduced into metallic Pd0 during the cellulose pyrolysis, due to the preferred reduction by adsorbed formaldehyde group and other reductants including H2 and CO in the vicinity of the PdO sites on the Pd-O-Si interface. Nevertheless, the catalyst was proven to retain the memory of its initial state after combustive regeneration in air, having oxidation state of Pd, particle size, and dispersion degree being reversed to its original construction. Accordingly, its activity remained stable upon cyclic testing. All these results demonstrate a high practical viability of this heterogenous catalyst for the valorisation of cellulose-rich biomass, an otherwise abundant crop waste across the world.

Online Flow Measurement of Liquid Metal Solutions Based on Impact Force Sequences: Modeling Analysis, Simulation, and Validation of Experimental Results.

Aiming at the existing high-temperature liquid metal flow online accurate measurement by the metal melt characteristics, installation space, and high-temperature environment adaptability limitations, this paper innovatively puts forward a soft measurement method based on the impact force generated in the fluid flow process as an observational variable series. Fluid mechanics theory and simulation software are used to analyze and verify the feasibility of the impact force as an observable variable to measure the flow rate, followed by the construction of the CNN-LSTM-CNN-Double (CLCD) flow measurement model of impact force and flow rate based on the parameters of the learning rate and the number of training times, and finally the construction of a test platform for the flow measurement, and the validity of the method is verified through actual operation.

Contrast and Complexity in the Low-Temperature Kinetics of CN(v = 1) with O2 and NO: Simultaneous Kinetics and Ringdown in a Uniform Supersonic Flow.

Bimolecular rate coefficients were determined for the reaction CN(v = 1) + NO and O2 using continuous wave cavity ringdown spectroscopy in a uniform supersonic flow (UF-CRDS). The well-matched time scales for ringdown and reaction under pseudo-first-order conditions allow for the use of the SKaR method (simultaneous kinetics and ringdown) in which the full kinetic trace is obtained on each ringdown. The reactions offer an interesting contrast in that the CN(v = 1) + NO system is nonreactive and proceeds by complex-mediated vibrational relaxation, while the CN(v = 1) + O2 reaction is primarily reactive. The measured rate coefficients at 70 K are (2.49 ± 0.08) × 10-11 and (10.49 ± 0.22) × 10-11 cm3 molecule-1 s-1 for the reaction with O2 and NO, respectively. The rate for reaction with O2 is a factor 2 lower than previously reported for v = 0 in the same temperature range, a surprising result, while that for NO is consistent with extrapolation of previous high-temperature measurements to 70 K. The latter is also discussed in light of theoretical calculations and measurements of the rate constants for the association reaction in the high-pressure limit. The measurements are complicated by the presence of a metastable population of high-J CN formed by photolysis of the precursor BrCN, and a kinetic model is developed to treat the competing relaxation and reaction. It is particularly problematic for reactions at low temperatures where the rotational relaxation and reaction have similar rates, precluding a reliable determination of the rate coefficients at 30 K. Also presented are important modifications to the data acquisition and control for the instrument that have yielded considerably enhanced stability and throughput.

Development of a Rayleigh-Brillouin scattering spectrometer for fast high-gas-temperature measurements.

We proposed a Rayleigh-Brillouin scattering (RBS) spectrometer based on a virtually imaged phased array (VIPA) for fast measurements of high-gas temperature. We measured the RBS spectra of air in the temperature range of 374 to 1073 K with an acquisition time of 7 s. We used the Tenti S6 model to fit the spectra and retrieve the absolute temperature values. The root mean square errors of spectra fit residual were less than 3.05%, and the absolute error of the retrieved temperature was less than 39 K. This study demonstrated the ability of the RBS spectrometer to realize fast high-temperature measurement and its potential for combustion control applications.

Advancing Heteroanionicity in Zintl Phases: Crystal Structures, Thermoelectric and Magnetic Properties of Two Quaternary Semiconducting Arsenide Oxides, Eu8Zn2As6O and Eu14Zn5As12O.

Two novel quaternary oxyarsenides, Eu8Zn2As6O and Eu14Zn5As12O, were synthesized through metal flux reactions, and their crystal structures were established by single-crystal X-ray diffraction methods. Eu8Zn2As6O crystallizes in the orthorhombic space group Pbca, featuring polyanionic ribbons composed of corner-shared triangular [ZnAs3] units, running along the [100] direction. The structure of Eu14Zn5As12O crystallizes in the monoclinic space group P2/m and its anionic substructure can be described as an infinite "ribbonlike" chain comprised of [ZnAs3] trigonal-planar units, although the structural complexity here is greater and also amplified by disorder on multiple crystallographic positions. In both structures, the O2- anion occupies an octahedral void with six neighboring Eu2+ cations. Formal electron counting, electronic structure calculations, and transport properties reveal the charge-balanced semiconducting nature of these heteroanionic Zintl phases. High-temperature thermoelectric transport properties measurements on Eu14Zn5As12O reveal relatively high resistivity (ρ500K = 8 Ω·cm) and Seebeck coefficient values (S500K = 220 μV K-1), along with a low concentration and mobility of holes as the dominant charge-carriers (n500K = 8.0 × 1017 cm-3, μ500K = 6.4 cm2/V s). Magnetic studies indicate the presence of divalent Eu2+ species in Eu14Zn5As12O and complex magnetic ordering, with two transitions observed at T1 = 21.6 K and T2 = 9 K.

High-Temperature DIC Deformation Measurement under High-Intensity Blackbody Radiation

During the high-speed flight of a vehicle in the atmosphere, surface friction with the air generates aerodynamic heating. The aerodynamic heating phenomenon can create extremely high temperatures near the surface. These high temperatures impact material properties and the structure of the aircraft, so thermal deformation measurement is essential in aerospace engineering. This paper revisits high-temperature deformation measurement using the digital image correlation (DIC) technique under high-intensity blackbody radiation with a precise speckle pattern fabrication and a heat haze reduction method. The effects of the speckle pattern on the DIC measurement have been thoroughly studied at room temperature, but high-temperature measurement studies have not reported such effects so far. We found that the commonly used methods to reduce the heat haze effect could produce incorrect results. Hence, we propose a new method to mitigate heat haze effects. An infrared radiation heater was employed to make an experimental setup that could heat a specimen up to 950 °C. First, we mitigated image saturation using a short-wavelength bandpass filter with blue light illumination, a standard procedure for high-temperature DIC deformation measurement. Second, we studied how to determine the proper size of the speckle pattern in a high-temperature environment. Third, we devised a reduction method for the heat haze effect. As proof of the effectiveness of our developed experimental method, we successfully measured the deformation of stainless steel 304 specimens from 25 °C to 800 °C. The results confirmed that this method can be applied to the research and development of thermal protection systems in the aerospace field.

Solidification and microstructure investigation on as-cast and annealed hypoeutectic Ti–Fe alloys

This work explored the solidification behavior, microstructure development, and resulting mechanical properties of hypoeutectic Ti–Fe alloys under both as-cast and annealed conditions. Ti-(27, 28, 29)Fe (wt%) alloys were synthesized through arc-melting, followed by annealing at 950 °C for 24 h and slow furnace cooling. The investigation procedures included thermodynamic calculations, differential scanning calorimetry, scanning electron microscopy, high-temperature laser-scanning confocal microscopy, X-ray diffraction, hardness measurements, and compression tests. The study demonstrated the efficacy of annealing treatments in reducing excess eutectic in the as-cast structure formed during solidification. Results from both thermodynamic calculation and experiment for the solidification process demonstrated reasonable agreement. The high β-stabilizing effect of Fe ensured the presence of the β phase at room temperature under both studied conditions. The solid-solution hardening of the β phase, coupled with the TiFe intermetallic, substantially contributed to the increased hardness and mechanical strength, although the increase in brittleness was noticeable in the as-cast state. Subsequent annealing enhanced plasticity but resulted in a reduction in strength, albeit maintaining yield strength at a considerable level, approximately 1450 MPa.

Ruddlesden-Popper Oxyfluorides La2Ni1-xCuxO3F2 (0 ≤ x ≤ 1): Impact of the Ni/Cu Ratio on the Thermal Stability and Magnetic Properties.

Ruddlesden-Popper oxyfluorides of the substitution series La2Ni1-xCuxO3F2 (0 ≤ x ≤ 1) were obtained by topochemical fluorination with polyvinylidene fluoride (PVDF) of oxide precursors La2Ni1-xCuxO4. The thermal stability and the temperature-dependent unit cell evolution of the oxyfluorides were investigated by high-temperature XRD measurements. The oxyfluoride with x = 0.6 shows the highest decomposition temperature of θdec ∼ 520 °C, which is significantly higher than the ones found for the end members La2NiO3F2 (x = 0) θdec ∼ 460 °C and La2CuO3F2 (x = 1) θdec ∼ 430 °C. The magnetic properties of all La2Ni1-xCuxO3F2 oxyfluorides were characterized by field- and temperature-dependent measurements as well as DFT calculations of the magnetic ground state. An antiferromagnetic ordering was derived for all substitution levels. For the Néel temperature (TN), a nonlinear dependence on the copper content was found, and comparably high values of TN in the region of 200-250 K were observed in the broad composition range of 0.3 ≤ x ≤ 0.8.

Electrohydrodynamic-Printed AgNPs/PR Thin-Film Temperature Sensors With Micro Dimensions and Higher Temperature Measurement Capabilities

Electrohydrodynamic-Printed AgNPs/PR Thin-Film Temperature Sensors With Micro Dimensions and Higher Temperature Measurement Capabilities