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排序方式: 共有379条查询结果,搜索用时 31 毫秒
31.
Laura R. Turcer Amanda R. Krause Hector F. Garces Lin Zhang Nitin P. Padture 《Journal of the European Ceramic Society》2018,38(11):3905-3913
The high-temperature (1500?°C) interactions of two promising dense, polycrystalline EBC ceramics, YAlO3 (YAP) and γ-Y2Si2O7, with a calcia-magnesia-aluminosilicate (CMAS) glass have been explored as part of a model study. Despite the fact that the optical basicities of both the EBC ceramics and the CMAS are similar, they both react with the CMAS. In the case of the Si-free YAlO3, the reaction zone is small and it comprises three regions of reaction-crystallization products, including Y-Ca-Si apatite solid-solution (ss) and Y3Al5O12 (YAG)(ss). In contrast, only Y-Ca-Si apatite(ss) forms in the case of Si-containing γ-Y2Si2O7, and the reaction zone is an order-of-magnitude thicker. These CMAS interactions are analyzed in detail, and are found to be strikingly different than those observed in Y-free EBC ceramics (β-Yb2Si2O7 and β-Sc2Si2O7) in the accompanying Part II paper. This is attributed to the presence of the Y in the YAlO3 and γ-Y2Si2O7 EBC ceramics. 相似文献
32.
Lana-Simone Unger Rian Ruhl Matthias Meffert Christian Niedrig Wolfgang Menesklou Stefan F. Wagner Dagmar Gerthsen Henny J.M. Bouwmeester Ellen Ivers-Tiffée 《Journal of the European Ceramic Society》2018,38(5):2388-2395
Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) in its cubic perovskite phase has attracted much interest for potential use as oxygen transport membrane (OTM) due to its very high oxygen permeability at high temperatures. However, performance degradation due to a sluggish phase decomposition occurs when BSCF is operated below 840?°C. Partial B-site substitution of the transition metal cations in BSCF by larger and redox-stable cations has emerged as a potential strategy to improve the structural stability of cubic BSCF. In this study, the influence of yttrium doping (0…10?mol-%) on oxygen transport properties and stability of the cubic BSCF phase is assessed by in situ electrical conductivity relaxation (ECR) and electrical conductivity measurements during long-term thermal annealing both at 700?°C and 800?°C. Detailed phase analysis is performed by scanning electron microscopy (SEM) after long-term annealing of the samples in air at different temperatures. 相似文献
33.
In the present study, white light emission based on both upconversion and thermal processes from single-phase yttrium silicate nanopowder doped with Neodymium (III) (Nd3+) was investigated at both room pressure and vacuum (0.01 mbar) with a diode laser excitation of 808 nm. 1% Nd3+ doped (per mole) yttrium silicate (Y2O3:SiO2) nanopowder was synthesized by using the sol-gel method and annealed at 1250 °C for 12 h to obtain the powder form. Emission for upconverted white light mainly due to the transitions of Nd3+ ions was obtained below ~ 5.79 W of the laser beam power at atmospheric pressure. For powers exceeding ~ 5.79 W, the powder emitted a thermal white light (WL) due to the photon avalanche mechanism together with thermal processes. The threshold power to obtain thermal white light with the transitions of Nd3+ ions was decreased to ~ 3.51 W at the vacuum condition. These processes were investigated in detail by studying the spectral differences of the rise and decay patterns at atmospheric pressure and vacuum conditions. 相似文献
34.
Trinh Nguyen Thi Phuoc Cao Van Duc Duong Viet Viet Dong Quoc Hayeong Ahn Viet Anh Cao Min-Gu Kang Junghyo Nah Byong-Guk Park Jong-Ryul Jeong 《Ceramics International》2021,47(12):16770-16775
In this study, we examined the dependence of surface morphology and spin Seebeck effect (SSE) voltages on the poly[vinylpyrrolidone] (PVP) concentration in polycrystalline Y3Fe5O12 (YIG) ultrathin films on a silicon substrate synthesized by metal-organic decomposition followed by a crystallization process. During fabrication, PVP concentrations of 0.5–2 g were used while all other conditions remained fixed. Atomic force microscopy and grazing incidence X-ray diffraction (XRD) measurements revealed a strong dependence of crystallinity and sample morphology on PVP concentration. The 1-g PVP sample had the smoothest surface, with a root mean square roughness of 0.2 nm, as well as superior bulk uniformity with respect to the shape and intensity of XRD reflection peaks. This was confirmed by scanning electron microscopy measurements of a cross-section of the sample that revealed a uniform film without pores. SSE measurements were performed to obtain the output SSE voltages (VSSE) of all samples, to which a platinum layer was added as a spin-detection layer. Repeatedly, the 1-g PVP sample had the best performance, demonstrating the importance of film crystallinity and morphology in the spin-to-charge conversion efficiency of YIG films. 相似文献
35.
《Ceramics International》2020,46(6):7324-7335
In order to obtain high-quality superalloy castings, the wettability and interactions between superalloy melts with various Y contents and SiO2-based ceramic cores were investigated at 1823 K. The results indicated that the wettability and interface reactions were affected by the content of Y in the alloy. For the alloys with Y content less than 0.011 wt%, no Y-oxide was found at the interface, but HfO2, Al2O3 and ZrO2 phases were formed, and the wetting angle dropped slightly. However, different Y-oxides precipitated at the alloy-ceramic interface for the alloys with Y content more than 0.017 wt%, and the wetting angle dropped sharply. When the content of Y was 0.017 and 0.025 wt%, Al2O3, Y3Al2(AlO4)3, HfO2 and ZrO2 phases were formed at the interface. When the content of Y was 0.1 wt%, YAlO3, Y3Al5O12, Y4Al2O9, HfO2 and ZrO2 phases were formed. The formation of different reaction products was mainly caused by the change of Y activity (aY) in the alloy. The reaction between Y and SiO2 could improve the wettability of the system apparently. 相似文献
36.
Pure nanostructures of yttrium aluminum garnet (YAG) was prepared based on the cathodic electrodeposition method from the mixture of YCl3 and AlCl3 dissolved in water/ethanol solution. At first, hydroxide precursors cathodically were grown on the steel substrates then, the hydroxide powders heat treated at 850 °C for 4 h in dry air atmosphere. The formation of crystalline YAG nanopowder was confirmed by X-ray diffraction (XRD), thermogravimetric analysis (DSC-TGA), scanning electron microscopy (SEM) and Fourier transformed infrared spectroscopy (FT-IR). The results of the SEM showed that applied current density and bath temperature have the prominent effect on the morphology and particle size of the products. The results revealed that cathodic electrodeposition followed by heat-treatment can be used as a facile method for preparation of YAG nanostructures with different morphology. 相似文献
37.
Junxia Ren 《Electrochimica acta》2006,52(3):1120-1126
Through homogeneous precipitation method, uniform spherical α-Ni(OH)2 particles were obtained at appreciate aging time in urea solution without any help of templates or dispersants. From SEM images, aging time exhibited great effects on the morphology of as-synthesized α-Ni(OH)2. Also, long aging time helped to improve the electrochemical performances of α-Ni(OH)2. It was found that the proper aging time was 12 h. However, α-Ni(OH)2 showed low charge/discharge capacities at high temperatures. Therefore, yttrium was added to improve the high-temperature electrochemical performances of α-Ni(OH)2. The influences of doping ratios of Y on the morphologic and high-temperature electrochemical characteristics were investigated through XRD, SEM, TEM, constant current charge/discharge, and cyclic voltammetric measurements. The α-Ni(OH)2 samples with the addition of about 5.8 mol% Y showed a discharge capacity of 250 mAh/g at 0.2 C rate and 60 °C, much higher than that of α-Ni(OH)2 without Y dopants (157 mAh/g). 相似文献
38.
Yttrium oxide doped with cerium (Y2O3:Ce3+) blue emitting phosphors was prepared by a new method called the bicontinuous cubic phase (BCP) method. The experimental results showed that the prepared precursors were amorphous yttrium hydroxide with a spherical shape and primary size 30-50 nm. After heat treatment, high crystallinity and luminescence efficiency phosphors were obtained. The obtained Y2O3:Ce3+ phosphors had a strong blue emitting at 400 nm. The optimum Ce3+ concentration was 1 mol% to obtain the highest PL intensity. This study indicated that the calcining temperature of 700 °C needed for high luminescence efficiency in this work is much lower than 1000 °C or above needed for the conventional solid-state method. 相似文献
39.
Y2.9-xCe0.1BixFe5O12 (x = 0-0.5) nanoparticles ranging from 58 to 63 nm were fabricated by a sol-gel method, and their crystallite structures and magnetic properties were investigated by X-ray diffraction (XRD), IR spectroscopy, and vibrating sample magnetometer (VSM). Results of VSM show that the saturation magnetization intensity increased with increase in Ce content (0.1), decrease in Bi concentration (x), and increase in particle size of the formulation. 相似文献
40.
Y2.9Ce0.1Fe5-xCrxO12 (x = 0-0.5) nanoparticles were fabricated by a sol-gel method. Samples with particle size ranging from 60 to 64 nm were obtained and their crystalline structures and magnetic properties were investigated by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). Results of VSM show that the saturation magnetization is increased firstly, after decreased with the Cr concentration (x). The saturation magnetization is increased with increasing the particle size. 相似文献