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51.
52.
Chengpeng Yang Fei Jia Bo Wang Tao Huang Guiqiong Jiao 《Journal of the American Ceramic Society》2021,104(2):1002-1013
To predict the nonlinear stress-strain behavior and the rupture strength of orthotropic ceramic matrix composites (CMCs) under macroscopic plane stress, a concise damage-based mechanical theory including a new constitutive model and two kinds of failure criteria was developed in the framework of continuum damage mechanics (CDM). The damage constitutive model was established using strain partitioning and damage decoupling methods. Meanwhile, the failure criteria were formulated in terms of damage energy release rate (DERR) in order to correlate the failure property of CMCs with damage driving forces, and the maximum DERR criterion and the interactive DERR criterion were suggested simultaneously. For the sake of model evaluation, the theory was applied to a typical CMC with damageable and nonlinear behavior, that is, 2D-C/SiC. The damage evolution law, strain response and rupture strength under incremental cyclic tension along both on-axis and off-axis directions were completely investigated. Comparison between theoretical predictions and experimental data illustrates that the newly developed mechanical theory is potential to give reasonable and accurate results of both stress-strain response and failure property for orthotropic CMCs. 相似文献
53.
Kwon-Hyeon Kim Paul H. Dannenberg Hao Yan Sangyeon Cho Seok-Hyun Yun 《Advanced functional materials》2021,31(48):2103413
Fluorescent microbeads are widely used for applications in life sciences and medical diagnosis. The spectral contrast and sharpness of photoluminescence are critical in the utilities of microbeads for imaging and multiplexing. Here, microbeads capable of generating single-peak laser emission with a sub-nanometer linewidth are demonstrated. The microbeads are made of quantum dots that are tightly packed and crosslinked via ligand exchange for high optical gain and refractive index as well as material stability. Bright single-mode lasing with no photobleaching is achieved with particle diameters as small as 1.5 µm in the air. Sub-nm lasing emission is maintained even inside high-index surroundings, such as organic solvents and biological tissues. Feasibility of intracellular tagging and multi-color imaging in vivo is demonstrated. 相似文献
54.
Yongqiang Zhang Zhiwei Zhou Weiwei Li Yu Yang Bingchu Mei Zaichun Sun 《Journal of the American Ceramic Society》2022,105(4):2932-2944
Nd3+ doped strontium fluorophosphate (S-FAP), with chemical formula Sr5(PO4)3F, nanopowders were prepared using the co-precipitation method. The prepared powders had no impurity phase with a grain size of about 30 nm and the doping limit of Nd3+ ions in strontium fluorophosphate is about 9 at.%. The morphology and particle size were determined by the doping concentration of Nd3+. Anisotropic Nd: S-FAP transparent ceramics with different Nd3+ doping concentrations were fabricated successfully by the simple hot-pressing method. The grain size of prepared S-FAP transparent ceramics decreased first and then increased with the increase of Nd3+ concentration. The 2 at.% Nd: S-FAP ceramic presented the highest optical transmittance at all wavelengths range. The characteristic transitions from the ground state to the excited states of Nd3+ ions were observed from the absorption spectra, and the absorption cross-section was calculated at 3.71 × 10–20 cm2. The influence of Nd3+ ion concentration on luminescence intensity and fluorescence lifetime was studied under 796 nm excitation. The strong emission of 4F3/2→4I9/2 transition in Nd: S-FAP was calculated by Judd–Ofelt (J-O) theory. 相似文献
55.
《Ceramics International》2022,48(22):32827-32836
To investigate the crystal structure, electrical properties, and magnetic properties of Ca–Sn co-doped Y3-xCaxFe5-xSnxO12 (x = 0.00–0.25 in steps of 0.05), solid-state reaction experiments, first principles calculations, and complex crystal bonding theoretical calculations were performed. The relative permittivity (εr) is strongly correlated with the average bond ionicity when Ca2+ is added. Furthermore, appropriate Sn4+ substitution significantly lowers the dielectric loss (tanδε) associated with the lattice energy. The right amount of Ca–Sn co-doping can change the saturation magnetization (4πMS) and improve the microscopic morphology of YIG, lowering the ferromagnetic resonance linewidth (ΔH) of YIG. The optimized microwave dielectric and magnetic properties are as follows: εr = 14.7, tanδε = 4.15 × 10?4, 4πMS = 1680 G, and ΔH = 53 Oe for Y2.8Ca0.2Fe4.8Sn0.2O12 sintered for 6 h at 1425 °C. Based on this material, a simple 3D model of a strip-line circulator with an insertion loss of less than 0.3 dB at each port and isolation greater than 20 dB in the 10–12 GHz range was developed, indicating the potential of the material for microwave high-frequency components such as circulators. 相似文献
56.
Controlling machining deformation of annular parts is crucial for ensuring the performance of high value products and equipment. For example, during manufacturing of critical parts in aircrafts and spacecrafts, accurate prediction of machining deformation is the basis for guiding the formulation of deformation control strategies. However, due to the complexity of the machining deformation of annular parts, existing methods still have limitations in accurate prediction. To this end, this paper proposes a mechanism informed neural network (MINN) to predict machining deformation of annular parts. MINN is realized by establishing the dual sub-networks structure and using enhanced loss functions with the consideration of the deformation mechanism model characteristics of annular parts. The deformation was decomposed into the axisymmetric portion and the non-axisymmetric portion according to the deformation superposition principle, and modeled separately based on the thin-shell theory and Fourier series. Experiment results showed that the proposed method could predict the machining deformation of annular parts more accurately and stably with a small amount of training data, compared with previous methods. 相似文献
57.
Nannan Chen Yanhong Wang Xiaoqiang Du Xiaoshuang Zhang 《International Journal of Hydrogen Energy》2021,46(49):25114-25120
Urea electrolysis is a promising technology for hydrogen production, which can alleviate environmental pollution of urea-rich wastewater. It's worth noting that electrochemistry activity can be significantly improved by reasonably regulating the electron configuration around the active site for the doped materials. In this work, a series of well-tuned Ni doped CoWO4 nanoarrays on Ni foam supports have been prepared through a typical hydrothermal approach for the first time. Moreover, the resulting Ni–CoWO4-2 material significantly promotes urea oxidation performance with an applied potential of 1.35 V at 50 mA cm?2, which is lower than that of water oxidation reaction (1.60 V). Density functional theory results suggest that the Ni doped CoWO4 has larger urea adsorption energy compared with CoWO4 and the CO(NH2)2 molecule is strongly adsorbed on surface of Ni doped CoWO4, which is beneficial to accelerate the kinetics of the reaction and improve the electrocatalytic activity of the urea electrolysis. 相似文献
58.
59.
Verification of unified effective stress theory based on the effect of moisture on mechanical properties of fiber reinforced unsaturated soil 总被引:1,自引:0,他引:1
Omar Al Hattamleh Samer Rababah Ahmad Alawneh Ahmad Alqawab'ah 《Geotextiles and Geomembranes》2021,49(4):976-990
The unified effective stress theory based on suction stress (SSCC theory) enables the characterization of soils under both saturated and unsaturated conditions with one closed-form relationship. This study provides experimental verification of this theory through the unconfined compressive strength test (UCS) and indirect tensile test strength (ITS) on silty clay soil stabilized with fiber. A series of matric suction, ITS, and UCS tests were conducted to validate the SSCC theory through the representation of the results of ITS and UCS tests in terms of mean total stress (p) versus deviatoric stress (q) and mean effective stress (p`) versus deviatoric stress (q). The results of the validation procedures showed that the SSCC theory is applicable and valid at a range of 6%–16% of water content on the silty clay and the silty clay fiber-reinforced soils. There is a small fluctuation in the increase of ITS and UCS values with increasing fiber content due to randomly oriented distribution of the fiber. The addition of glass fiber does not significantly affect the capacity of water retention of the soil. It improves the condition of the mechanical soil properties at the end of construction more than of the effective stress condition. 相似文献
60.
《International Journal of Hydrogen Energy》2021,46(58):30061-30078
A uniform solid product layer normally assumed in the shrinking-core model cannot predict the kinetic transition behavior of the H2 adsorption reactions. In this study, the concept of a uniform solid product layer has been replaced by that of the inward growth of solid products on the solid surface. A rate equation is established to calculate the inward growth of the solid product and was implemented into the shrinking-core model to calculate the H2 adsorption kinetics for various shapes of Mg-based materials. The prediction accuracy of the developed model is verified from the detailed experimental data. To account for the external gas diffusion around the particle and the intraparticle gas diffusion, an analytical equation is derived using the Thiele modulus method. This model can be used to analyze various kinetic aspects and to analyze the effect of change in the particle microstructure on intraparticle diffusion. 相似文献