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31.
《Ceramics International》2022,48(7):9673-9680
Solid oxide fuel cells (SOFCs) have strong potential for next-generation energy conversion systems. However, their high processing temperature due to multi-layer ceramic components has been a major challenge for commercialization. In particular, the constrained sintering effect due to the rigid substrate in the fabrication process is a main reason to increase the sintering temperature of ceramic electrolyte. Herein, we develop a bi-layer sintering method composed of a Bi2O3 sintering sacrificial layer and YSZ main electrolyte layer to effectively lower the sintering temperature of the YSZ electrolyte even under the constrained sintering conditions. The Bi2O3 sintering functional layer applied on the YSZ electrolyte is designed to facilitate the densification of YSZ electrolyte at the significantly lowered sintering temperature and is removed after the sintering process to prevent the detrimental effects of residual sintering aids. Subsequent sublimation of Bi2O3 was confirmed after the sintering process and a dense YSZ monolayer was formed as a result of the sintering functional layer-assisted sintering process. The sintering behavior of the Bi2O3/YSZ bi-layer system was systematically analyzed, and material properties including the microstructure, crystallinity, and ionic conductivity were analyzed. The developed bi-layer sintered YSZ electrolyte was employed to fabricate anode-supported SOFCs, and a cell performance comparable to a conventional high temperature sintered (1400 °C) YSZ electrolyte was successfully demonstrated with significantly reduced sintering temperature (<1200 °C). 相似文献
32.
33.
《Ceramics International》2022,48(7):9765-9780
The polycrystalline ceramic specimens of three different alumino-silicate solid solutions (Al0.70Si0.30O, Al0.73Si0.27O and Al0.75Si0.25O) consisting of different alumina and silica concentrations have been synthesized by thermal plasma sintering technique. From structural analysis carried out by X-ray diffraction, the ceramics are mostly found to consist of two different phases of mullite and sillimanite. SEM images of these ceramics reveal a high dense and less porous microstructure with homogeneous distribution of grains throughout their surface. These materials exhibit high dielectric constant value (>103) with low dissipation factor. The AC conductivity analysis reveals that Al0.70Si0.30O and Al0.75Si0.25O ceramics possess room temperature conductivity values of the order of 10?5, whereas Al0.73Si0.27O has conductivity of 10?7 order that increases with rise in temperature. From the Nyquist plots, the grain and grain boundary conductivities are distinguished and negative temperature coefficient of resistance behavior is identified in these ceramics with small positive temperature coefficient of resistance effect. 相似文献
34.
《Ceramics International》2022,48(11):15640-15646
Ferroelectric ceramic with a large electrocaloric (EC) effect at a very low electric field is very attractive in the next solid state refrigeration technology. In this work, two Pb(Sc0.25In0.25Nb0.25Ta0.25)O3 (PSINT) medium-entropy ceramics were successfully synthesized by a spark plasma sintering (SPS) technology, including one-step-SPS processed and two-step-SPS processed samples. A large EC effect (△T ~ 0.85 K) with a high EC strength (△T/△E ~ 0.021 K cm/kV) around room temperature are obtained at a very low electric field (~40 kV/cm) in the two-step-SPS processed sample. Moreover, the working temperature range is very broad (~120 K), which can be responsible for the high relaxation degree of the dielectric peak. It can be believed that the PSINT medium-entropy ceramics can be promising candidates for application in the next-generation EC cooling devices. 相似文献
35.
《Journal of the European Ceramic Society》2022,42(2):729-733
The microstructure evolution in 3D was studied by X-ray microtomography to reveal the relation between topology of pore networks and characteristic length in viscous sintering. The mean intercept length was defined from solid/pore interface for characterizing the length of solid phase and pore phase. The increase of the characteristic length with densification was termed as domain coarsening. The topological pore evolution was analyzed by using genus. The characteristic length increased with decreasing genus in the intermediate stage. The domain coarsening takes place as a natural consequence of pore evolution in viscous sintering, i.e., the decrease of total surface area concurrent with the topological transformations. 相似文献
36.
《Journal of the European Ceramic Society》2022,42(14):6762-6765
Transparent YIG (Y3Fe5O12) ceramics are successfully synthesized by reactive sintering at normal pressure using γ-Fe2O3 and Y2O3 as starting materials. The grain size of the sintered YIG ceramics is ca. 10–15 µm. Residual pores are not observed on the surface of sample, but numerous residual pores are observed by infrared transmission microscopy. In-line transmittance of a commercially available high-quality YIG single crystal (thickness 1 mm) fabricated by the floating zone method is 75 % in the near to mid-infrared region, whereas the sample produced in this study shows an in-line transmittance of 71 % in the wavelength range above 1.5 µm. 相似文献
37.
《Journal of the European Ceramic Society》2022,42(8):3559-3569
To explore the mechanism of phase transformation, YTa3O9 was prepared by an integrated one-step synthesis and sintering method at 1500 °C using Y2O3 and Ta2O5 powders as starting materials. High-temperature XRD patterns and Raman spectra showed that a phase transformation from orthorhombic to tetragonal took place in YTa3O9 through the bond length and angle changes at 300–400 °C, which caused a thermal conductivity rise. To inhibit the phase transformation, a high-entropy (Y0.2La0.2Ce0.2Nd0.2Gd0.2)Ta3O9 (HE RETa3O9) was designed and synthesized at 1550 °C using the integrated solid-state synthesis and sintering method. In tetragonal structured HE RETa3O9, phase transformation was inhibited by the high-entropy effect. Furthermore, HE RETa3O9 exhibited low thermal conductivity, and its tendency to increase with temperature was alleviated (1.69 W/m·K, 1073 K). Good phase stability, low thermal conductivity and comparable fracture toughness to YSZ make HE RETa3O9 promising as a new thermal barrier coating material. 相似文献
38.
《Ceramics International》2022,48(16):23151-23158
SiC composite ceramics have good mechanical properties. In this study, the effect of temperature on the microstructure and mechanical properties of SiC–TiB2 composite ceramics by solid-phase spark plasma sintering (SPS) was investigated. SiC–TiB2 composite ceramics were prepared by SPS method with graphite powder as sintering additive and kept at 1700 °C, 1750 °C, 1800 °C and 50 MPa for 10min.The experimental results show that the proper TiB2 addition can obviously increase the mechanical properties of SiC–TiB2 composite ceramics. Higher sintering temperature results in the aggregation and growth of second-phase TiB2 grains, which decreases the mechanical properties of SiC–TiB2 composite ceramics. Good mechanical properties were obtained at 1750 °C, with a density of 97.3%, Vickers hardness of 26.68 GPa, bending strength of 380 MPa and fracture toughness of 5.16 MPa m1/2. 相似文献
39.
《Ceramics International》2022,48(20):29561-29571
Currently, materials with outstanding absorption abilities, such as thin size, better absorbing power, and light weight are the need of industry to resolve the electromagnetic issues. However, the research on optimizing the composition of the material, microstructure and the structure of the absorber are also the important factors for enhancing the absorption features. A metamaterial microwave absorber (MMA) based on nano ferrites with desirable absorption peaks is proposed and simulated. Sol-gel auto combustion route is used to prepare the nanosized Sm doped Co ferrite with Co1+xSmxFe2-2xO4 at x = 0.00, 0.03, 0.06, 0.09, respectively. XRD, VSM, FESEM, and VNA were employed to evaluate the structural, magnetic, morphological, and dielectric features. Rietveld refinement of the XRD patterns of samples was evaluated. Refined parameters show the spinel phase's emergence and the Fe2O3 phase. Grain size and crystallite size were increased with Sm doping in Co ferrite. Electromagnetic studies depicted that the highest dielectric constant value was found at x = 0.09 and the minimum value at x = 0.03, respectively. Sm doped Co ferrite at x = 0.09 depicted high Q values at higher frequencies. The coercivity values first decreased and then increased. All samples exhibit variations in coercivity and magneto-crystalline anisotropy constant. This variation was attributed to the super-exchange interactions and strong LS coupling of the cations. The multiple absorption peaks are attained for TE-polarization, and the absorptivity is considerably improved for x = 0.09. The proposed absorber simulated from CST depicted the absorption peaks of the S-band and C-band of the microwave regime. The synergistic effects among the metamaterial and ferrite layers may enhance the absorption feature and would be useful for satellite communication applications. 相似文献
40.
《Journal of the European Ceramic Society》2022,42(4):1354-1361
Core–rim structures were observed as common features in Y-α-SiAlON ceramics hot-pressed between 1550?1950 °C. We found most dopants were taken into α’-rims, and a transition layer grown first on α-cores from liquid-phase over-saturated with metal solutes. Elongated β’-grain were formed as minor phase with α’- or AlN-cores thus only after the α’ matrix had consumed up all Y solutes, revealing that the α’ → β’ transformation is controlled by the transient liquid-phase and similar defects and dangling bonds could be detected in both SiAlON phases by cathodoluminescence. Quantitative assessment of Ym/3Si12?(m+n)Alm+nOnN16?n demonstrates the multiphase evolution, initiated by over-saturation of Y solutes at low temperatures thus retaining α-phase as cores to lower the infra-red transmittance, dictated by homogenization of Al solutes at higher temperature. The elimination of those phase boundaries leads to better dopant and sintering design for achieving transparent and high-performance SiAlON ceramics. 相似文献