High ceiling temperature and the corresponding thermal stability are crucial to thermo-sensitive materials under extreme conditions. However, these features are often difficult to achieve simultaneously in conventional thermo-sensitive ceramics, thus becoming a key bottleneck restricting the development of thermo-sensitive ceramics in next-generation advanced high-temperature sensors. Here, for the first time, a (Ho0.2Er0.2Tm0.2Yb0.2Lu0.2)3NbO7 high-entropy ceramic is reported which possesses exceptional thermosensitive capability and high thermal stability. With the structure construction involving constraining a NbO6 octahedron by tailoring the lattice distortion and solving the stability degeneration caused by the tilt of the NbO6 octahedron and dipolar interactions of the off-centered Nb cations, the materials with highly dense lattice distortion dominated by symmetric tensile–compressive strains exhibit thermo-sensitive characteristics from 623 K to 1873 K. More importantly, the materials demonstrate exceptional thermal stability, with an aging coefficient of less than 1% after aging at 1873 K for 400 h. They also show an ultrahigh measurement accuracy (R2 as high as 999.92‰ and RSS as low as 0.071) maintaining excellent sensitivity at temperatures up to 1873 K. This work provides an effective way to design high-temperature thermosensitive ceramics with high ceiling temperature and high thermal stability to meet the demanding requirements of advanced high-temperature measurement applications.
Yao Hu,Donghui Wang,Bo Hu,Haihui Lan,Wen Zhong,Qi Wang,Huicong Xia,Mingde Yao,Mingqing Chen,Mingliang Du
The field of electrochemical ammonia synthesis has made rapid advancements, attracting a large number of scientists to contribute to this area of research. Accurate detection of ammonia is crucial in this process for evaluating the efficiency and selectivity of electrocatalysts. In this study, we systematically investigate the indophenol blue method for ammonia detection, examining the effects of key factors such as solution pH, nitrate concentration, and metal ion concentration on measurement accuracy. Based on experimental optimization and mathematical algorithms, we propose an iterative refinement method supported by custom-developed code. This method automates the generation and adjustment of calibration curves, reduces measurement errors, and enhances detection precision, offering a valuable framework for the quantitative detection of ammonia and other small molecules in electrochemical synthesis.
This paper reports on a practical headspace gas chromatographic method (HS-GC) for rapid determination of degree of substitution (DS) in sodium carboxymethyl starch (Na-CMS). After Na-CMS was acidified by hydrochloric acid (HCl) solution, the supernatant of the solution was added to a bicarbonate solution in a closed headspace vial. Thus, the remaining HCl reacts with bicarbonate to form carbon dioxide gas and thus was measured by HS-GC. The result showed that the Na-CMS was completely converted to H-CMS within 45 min at a room temperature when a small sample size (= 0.5 g) was used by acidification pretreatment. The present method has a good measurement precision (the relative standard deviation <3.25%) and accuracy (the relative difference < 5.46%, compared to the data measured by the reference method) on the determination of DS in Na-CMS. The present method is simple, practical, and suitable for the use in the carboxymethyl starch related research and applications.
Next-generation advanced high-temperature sensors rely heavily on negative temperature coefficient thermosensitive ceramics with low cost, small volume, high sensitivity, and fast response. However, thus far, the enormous challenge of achieving ultrahigh stability and accuracy has become a critical bottleneck restricting the development of thermosensitive ceramics in high-temperature sensor applications. Here, we propose a high-entropy strategy to design a “cation valence self-equilibrium” system in CeNbO4+δ-based ceramics introducing redox couple compensation and ultrahigh density dislocations to solve the problem of temperature-dependent oxygen nonstoichiometry that restricts the performances of high-temperature thermosensitive ceramics. Ferroelastic domains are generated by enhancing the configurational entropy at both A and B sites, resulting in a dramatic increase of dislocation density to >1010 mm–2, which ultimately optimizes the thermosensitive performances. Extreme temperature measurement accuracy with R2 as high as 999.98‰ and RSS as low as 0.011 and high-temperature stability with ΔR/R0 as low as 0.23% after aging at 873 K for 1000 h are realized in high-entropy CeNbO4+δ-based ceramics, indicating a breakthrough in the comprehensive performances of thermosensitive ceramics. This work opens up an effective way to design thermosensitive materials with ultrahigh comprehensive performance to meet the requirements of advanced high-temperature sensors.
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