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1.
《International Journal of Hydrogen Energy》2022,47(94):40099-40115
In order to reveal the mechanism of water fog explosion suppression and research the combined effect of water fog and obstacle on hydrogen/air deflagration, multiple sets of experiments were set up. The results show that the instability of thermal diffusion under lean combustion conditions is the main influencing factor of hydrogen/air flame surface instability, and the existence of water fog will aggravate the hydrogen/air flame surface instability. When obstacle is not considered, 8 μm, 15 μm, 30 μm water fog can significantly reduce the flame velocity and explosion overpressure of hydrogen/air, 45 μm fine water fog plays the opposite role. When considering the relative position of the water fog release position and the obstacle, the 8 μm, 15 μm, 30 μm water fog has almost no suppression effect when released near the obstacle, but a significant suppression effect occur, when using the 45 μm water fog. In the field of theoretical research, the research results not only provide an experimental basis for the fine water fog to reduce the consequences of hydrogen explosion accidents, and the optimal diameter range used by the water fog, but also provide experimental reference for the numerical simulation of hydrogen/air explosion suppression in semi-open space, and promote the development of hydrogen explosion suppression theory. In terms of engineering applications, this study can provide a theoretical basis for the layout of fire fighting equipment in the engine room of nuclear power plants or hydrogen-powered ships. 相似文献
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《Ceramics International》2022,48(17):24906-24914
Synthesis of materials in Ni/SrTiO3 system was undertaken. Perovskite structure material with nominal composition SrTi0.98O3 was synthesised by the sol-gel method. Nickel was introduced into the system by the wet impregnation method followed by proper thermal treatment. Two research paths were carried out: the evaluation of sintering conditions on material properties (sintering temperature: 1100, 1200, 1300 and 1400 °C; sintering time: 1, 3 and 5 h for sintering at 1300 °C) and the effect of nickel addition on the material properties - 1, 2, and 5 mol% of Ni compared to the amount of Ti was introduced into the analysed system. The microstructures of the materials, together with their structural (XRD analysis) and electrical (total conductivity and Seebeck coefficient) properties, were determined. Furthermore, temperature-programmed reduction (TPR) and temperature-programmed oxidation (TPOx) measurements were performed to evaluate the materials’ redox properties. It was shown that less than 1 mol% of Ni could be incorporated into the strontium titanate structure when a wet impregnation was chosen as the method for the introduction of Ni into the SrTiO3-based system. NiO and, for the highest amount of introduced nickel, also NiTiO3 were the main additional nickel-containing phases. For all materials synthesised in the Ni/SrTiO3 system, the positive value of the Seebeck coefficient was observed, suggesting that nickel is an acceptor-type dopant while incorporated into the perovskite structure. However, the TPR measurements clearly imply that nickel can be incorporated into the strontium titanate structure in various oxidation states. 相似文献
5.
《Ceramics International》2022,48(21):31559-31569
Colloidal Zinc oxide quantum dots (ZnO QDs) prepared with varying concentrations through precipitation method were deposited on flexible ITO/PET substrates using spin-coating technique. Various characterization tools were utilized to investigate the morphological, structural, electrical and optical properties of the films. The crystallinity of the films was found to improve with increasing ZnO QD concentration (ZQC) as evident from the X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) studies. Crystallographic and optical parameters were evaluated and explained in depth. The average nanograin size and bandgap were increased and decreased respectively, from ~5 nm to ~8 nm and 3.29 eV–3.24 eV with an increase in ZQC from 10 mg/mL to 70 mg/mL. Columnar structure growth of the films is revealed by AFM results. The films showed decent optical transparency up to 81%. All the ZnO films exhibited n-type semiconducting property as indicated by the electrical measurements with carrier mobility and low resistivity of 12.21–26.63 cm2/Vs and 11.84 × 10?3 to 13.16 × 10?3 Ω cm respectively. Based on the experimental findings, ZnO QD nanostructure film grown at 50 mg/mL is envisaged to be a potential candidate for flexible perovskite photovoltaic application. 相似文献
6.
《Ceramics International》2021,47(22):31920-31926
The Sr and Ba bearing Tl-1212 phase, Tl(Ba,Sr)CaCu2O7 is an interesting superconductor. The Sr only bearing TlSr2CaCu2O7 is not easily prepared in the superconducting form. The Ba only bearing TlBa2CaCu2O7 on the other hand does not show improvement in the transition temperature with elemental substitution. In this work the influence of multivalent Se (non-metal) and Te (metalloid) substitutions at the Tl-site of Tl1-xMx(Ba,Sr)CaCu2O7 (M = Se or Te) superconductors for x = 0–0.6 was studied. The samples were prepared via the conventional solid-state reaction method. XRD patterns showed a single Tl-1212 phase for x = 0 and 0.1 Se substituted samples. The critical current density at the peak temperature, Tp of the imaginary (χ”) part of the AC susceptibility (χ = χ’ +χ”), Jc-inter(Tp) for all samples was between 15 and 21 A cm−2. The highest superconducting transition temperature was shown by the x = 0.3 Se-substituted sample (Tc-onset = 104 K, Tc-zero = 89 K, Tcχ’ = 104 K and Tp = 80 K). Te suppressed the superconductivity of Tl-1212 phase. The order of highest transition temperatures are as follows: Tl1-xTex(Ba,Sr)CaCu2O7<Tl(Ba,Sr)CaCu2O7<Tl1-xSex(Ba,Sr)CaCu2O7. This work showed that Se was better than Te in improving the transition temperature and flux pinning of the Tl-1212 phase. The roles of ionic radius of Se and Te on the superconductivity of Tl(Ba,Sr)CaCu2O7 are discussed in this paper. 相似文献
7.
教学行为分析作是教学质量分析的重要组成部分,也是教学引导与反馈机制的重要依据。文章阐述了人工智能(AI)的含义及发展历程,重点分析总结了教学行为分析方法及AI在教学行为分析上的应用。文章以东南大学电工电子在线实验为研究平台,探索分析了AI技术在实验教学行为分析上的可行性,梳理了基于专家系统的在线实验分析系统的设计思路,充分探讨了“智能”教育在实验教学中的深刻内涵。 相似文献
8.
《Ceramics International》2021,47(21):29598-29606
A hybrid nanocomposite comprising nanosized ZrO2 and graphene nanoplatelet (GNP)-reinforced Cu matrix was synthesised via powder metallurgy. The influence of sintering temperature and GNP content on the electrical and mechanical behaviour of the Cu–ZrO2/GNP nanocomposite was investigated. The ZrO2 concentration was fixed at 10% for all the composites. Upon increasing the GNP concentration up to 0.5%, a significant improvement was observed in the compressive strength, microhardness, and electrical conductivity of the composite. Furthermore, the properties were significantly improved by increasing the sintering temperature from 900 to 1000 °C. The compressive strength, hardness, and electrical conductivity of Cu–10%ZrO2/0.5%GNP were higher than those of the Cu–ZrO2 nanocomposite by 60, 21, and 23.8%, respectively. This improvement in the mechanical properties is because of the decrease in the crystallite size and dislocation spacing, which increases the dislocation density, thereby increasing the impedance towards dislocation movement. The lower stacking fault energy of the hybrid nanocomposites enables easier electron transfer within and between the Cu grains, resulting in an improved electrical conductivity. The enhancement in strength and electrical conductivity were aided by the GNPs and ZrO2 nanoparticles that were dispersed widely in the Cu matrix. 相似文献
9.
《Ceramics International》2022,48(22):33092-33100
CeNbO4+δ ceramics have attracted extensive research interest because of their unique mixed ion-electron transport characteristics and interesting structure-functional characteristics caused by the difference in oxygen ion content. Although the change of oxygen ion content brings rich redox properties, it also causes serious crystal transformation and abnormal electrical transport properties. In order to obtain stable structure and excellent electrical transport properties, the directional regulation of the oxygen ion content has been realized through introducing Al2O3 and high temperature aging. After 600 h of aging at 1073 K, the prepared composite ceramics not only obtain a stable structure without crystal transformation, but also show good negative temperature coefficient (NTC) thermistor characteristics in the temperature range of 473 K–1273 K, in which the linear fitting maximum Pearson's r of the relationship between lnρ and 1000/T can reach 99.97%. The proposed method provides a new thought for the design and application of high-temperature electronic ceramics. 相似文献
10.
《Ceramics International》2022,48(11):15293-15302
The in situ temperature monitoring of hot components in harsh environments remains a challenging task. In this study, SiBCN thin-film resistance grids with thicknesses of 1.8 μm were fabricated on alumina substrates via direct writing. Owing to their dense microscopic morphology and extremely high graphitisation level, the produced SiBCN films exhibited large high-temperature oxidation resistance and electrical conductivity. The resistance–temperature, stability, and repeatability characteristics of these films were examined in an aerobic environment at temperatures up to 800 °C. The obtained results revealed that the thermistor resistance decreased monotonously with increasing temperature from room temperature to 800 °C. The SiBCN film resistance variations observed during repeated temperature cycling in the regions of 505–620 °C and 610–720 °C were 0.09% and 1.7%, respectively. The high cyclability and stability of the SiBCN thin film thermistor suggested its potential applicability for the in situ temperature monitoring of hot components in harsh environments. 相似文献