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991.
《Ceramics International》2022,48(9):12014-12027
The formed deposits wear out of refractory wall linings in the rotary kiln and may cause production disturbances. This study describes the chemical composition and mineralogical phase components at the deposit/refractory interface in the rotary kiln for fluxed iron ore pellets production. The main phases of refractory bricks are corundum and mullite, while the deposits mainly contain hematite and silicates. The main phases in the deposit/refractory brick contact zone are hematite, anorthite (CaAl2Si2O8), mullite, corundum, and silicates. Moreover, the hematite phases in the deposit/brick interface averagely contain 6.98 wt% Al and 1.38 wt% Ti. The silicates in the contact zone contain higher aluminium content and lower iron content than the silicates in the deposits. Finally, the thermodynamic analysis indicates that the main phases in the deposits can react with the refractory to form Al2Fe2O6, CaAl2Si2O8, feldspar, and liquid phases lead to the degradation of bricks in the kiln during the iron ore pellets production. 相似文献
992.
《Ceramics International》2022,48(10):13524-13530
Thin film sensors are employed to monitor the health of hot-section components of aeroengine intelligence (for instance, blades), and electrical insulating layers are needed between the metal components and thin film sensors. For this purpose, the electrical insulation characteristics of an yttria-stabilized zirconia (YSZ)/Al2O3 multilayer insulating structure were investigated. First, YSZ thin films were deposited by DC reactive sputtering at various substrate temperatures, and the microstructural features were investigated by scanning electron microscopy and X-ray diffraction. The results indicate that the micromorphology of the YSZ thin film gradually became denser with increasing substrate temperature, and no new phases appeared. The compact and uniform topography of the YSZ thin film improved the insulation properties of the multilayer insulating structure and enhanced the adhesion of the thin film sensors. In addition, the electrical insulation properties of the YSZ/Al2O3 multilayer insulating structure were evaluated via insulation resistance tests from 25 to 800 °C, in which the YSZ thin film was deposited at 550 °C. The results show that the insulation resistance of the multilayer structure increased by an order of magnitude compared with that of the conventional Al2O3 insulating layer, reaching 135 kΩ (5.1 × 10?6 S/m) at 800 °C. Notably, the insulation resistance was still greater than 75 kΩ after annealing at 800 °C for 5 h. Finally, the shunt effect of the YSZ/Al2O3 multilayer insulating structure was estimated using a PdCr thin film strain gauge. The relative resistance error was 0.24%, which demonstrates that the YSZ/Al2O3 multilayer insulating structure is suitable for thin film sensors. 相似文献
993.
《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
994.
《Journal of the European Ceramic Society》2022,42(1):43-51
Poor antioxidant and thermal-shock capacities of C/C composites thermal barrier coating (TBC) caused by cracking and shedding of coatings has been a major obstacle blocking the development of C/C composites. Herein, in-situ growth of whisker reinforced silicon carbide transition layer and inter-embedding mechanism of multi-gradient coatings were brought into the design of TBC to enhance the antioxidant and thermal-shock capacities. A three-layer gradient coating SiC-SiCw/ZrB2-SiC/ZrSiO4-aluminosilicate glass (ZAG) from inside to outside, in which ZrB2-SiC/ZAG serve as oxygen barrier layers with self-healing ability and SiC-SiCw provides thermal stress buffering and bonding against cracking and shedding of coatings, is designed. The ZAG mainly forms a dense oxygen blocking frontier with self-healing ability through fluidized glass, while the ZrB2-SiC can react actively with infiltrated oxygen in a way of self-sacrifice, preventing oxygen erosion to C/C matrix and SiC-SiCw transition layer. As a result, the collaborative work among layers endows this coating with excellent high temperature service performance. This work provides a new insight for the design of excellent TBC. 相似文献
995.
Dielectric and mechanical properties of hypersonic radome materials and metamaterial design: A review 总被引:1,自引:0,他引:1
《Journal of the European Ceramic Society》2022,42(1):1-17
This review paper examines ten current ceramic radome materials under research and development and provides a comprehensive overview of available high temperature and high frequency data from literature. An examination of metamaterials for radio-frequency transparent radomes is given and our preliminary experimental results of a high-temperature metamaterial design are presented. The next-generation hypersonic vehicles’ radome temperatures will exceed 1000℃ and speeds will exceed Mach 5. An ideal radome material will have a high flexural strength, low dielectric constant and loss tangent, and high resistance to thermal shock and corrosion. The microstructural effect on the dielectric and mechanical properties and the effects of environmental factors such as rain are discussed. The impact of metamaterial structure on key radome factors such as boresight error, gain, and polarization is examined. After examining the associated benefits with the use of metamaterials, our preliminary results for a potential high-temperature metamaterial design are presented. 相似文献
996.
《Journal of the European Ceramic Society》2022,42(4):1388-1395
Dielectrics for automobile applications generally require high temperature reliability. Bi1/2Na1/2TiO3-based materials are excellent high-temperature dielectric candidates with relatively large temperature-insensitive dielectric responses and a maximum dielectric permittivity temperature as high as 300 °C. However, they suffer from a high dielectric loss that increases exponentially above 200 °C due to ionic conduction from thermally activated oxygen vacancy migration. Here, we demonstrate that the impact of ionic conduction on dielectric loss can be effectively suppressed by introducing a sodium deficiency and thermal annealing An appropriate combination of both treatments elevated the temperature insensitivity of the dielectric loss up to ~ 300 °C. A systematic investigation using impedance spectroscopy correlated with microstructure analysis revealed that the sodium deficiency and thermal annealing affected the mobile oxygen vacancy concentration differently. 相似文献
997.
《Journal of the European Ceramic Society》2022,42(9):3787-3801
The influences of the SiC infiltration and coating on the compressive mechanical behaviours of 2D C/SiC composites were determined up to 1600 °C at 0.001 and 1000/s strain rates in argon and air. In addition, the failure mechanisms responsible for the compressive mechanical behaviours were elucidated through in-situ observation and micro-analysis-based methods. The 2D C/SiC composite compressive strength was highly sensitive to temperature, loading rate, and oxidation, and was enhanced by the change in the thermal residual stress and decreased by oxidation. In argon, because of the extra infiltrated SiC matrix, SiC treated 2D C/SiC specimens exhibited higher compressive strengths and lower strain rate sensitivity factors than SiC untreated 2D C/SiC specimens. The SiC coating effectively improved the oxidation resistance of the 2D C/SiC composites in air, regardless of the temperature, strain rate, and oxidative damage-which depends on SiC coating, strain rate, and temperature. 相似文献
998.
《Journal of the European Ceramic Society》2022,42(9):3857-3864
The Mn-modified 0.75BiFeO3-0.25BaTiO3 (75BFBTMn) piezoelectric ceramic possesses a high depolarization temperature of 500 °C and a large piezoelectric coefficient of 110 pC/N, showing the potential for high temperature piezoelectric sensors. However, 75BFBTMn ceramic usually suffers dielectric degradation and abrupt drop of piezoelectric coefficient in the range of 300 °C to 500 °C. Combined the high-energy synchrotron X-ray diffraction analysis with Backscatter-SEM results, it is demonstrated that the electrical thermal instability is owing to the existence of chemical inhomogeneity. The Air-annealing treatment is able to decrease the volume fraction of pseudo-cubic phase and the lattice distortion, removes the chemical inhomogeneity in the grain and free Bi2O3 at grain boundary, and then eliminates dielectric anomalies and piezoelectric degradation with temperature. These results indicate that air-annealing is a simple but effective method to eliminate the chemical inhomogeneity in 75BFBTMn ceramics, thereby improving the property thermal stability for high temperature piezoelectric sensor applications. 相似文献
999.
《Ceramics International》2022,48(20):29882-29891
A simple strategy for preparing MgO–Al2O3–CaO-based porous ceramics (MACPC) with high strength and ultralow thermal conductivity has been proposed in this work based on the raw material of phosphorus tailings. The effects of phosphorus tailings content, carbon black addition and heat treatment temperature on the properties of MACPC were studied, and their pore-forming mechanism during sintering was revealed. The results showed that the main phase composition of MACPC was magnesia alumina spinel and calcium aluminate after sintering at 1225 °C. Furthermore, the MACPC exhibited excellent comprehensive properties when 60 wt% phosphorus tailings and 40 wt% alumina were added, whose apparent porosity was 62.8%, cold compressive strength was 14.8 MPa, and the thermal conductivity was 0.106 W/(m·K) at 800 °C. The synchronously enhanced strength and thermal insulation properties of MACPC were related to the formation of uniformly distributed micropores (<2 μm) and passages in the matrix, which originated from the decomposition of phosphorus tailings and the burnt out of carbon black during the sintering process. The preparation of MACPC with high temperature resistance and excellent mechanical and thermal insulation properties with the raw material of phosphorus tailings provided an effective method for the high-value utilization of phosphorus tailings. 相似文献
1000.
《Ceramics International》2022,48(20):29959-29966
High-purity SiC ceramic devices are applied in semiconductor industry owing to their outstanding properties. Nevertheless, it is difficult to densify SiC ceramics without any sintering additive even by HP sintering. In this work, high-purity and dense SiC ceramics were fabricated by HP sintering with very low amounts of sintering aids. Residual B content was only 556 ppm and relative density was more than 99.5%. Furthermore, thermal conductivity of as-prepared SiC ceramics was improved from 155 W m?1 K?1 to 167 W m?1 K?1 by increasing holding time and their plasma corrosion resistance was promoted in the meantime. The as-prepared high-purity SiC ceramics have broad application prospects in the field of semiconductor industry. 相似文献