共查询到20条相似文献,搜索用时 10 毫秒
1.
Jiatong Zhu Xuanyu Meng Ping Zhang Zhuolun Li Jie Xu Michael J. Reece Feng Gao 《Journal of the European Ceramic Society》2021,41(4):2861-2869
A series of rare earth zirconates (RE2Zr2O7) high-entropy ceramics with single- and dual-phase structure were prepared. Compared with La2Zr2O7 and Yb2Zr2O7, the smaller “rattling” ions (Yb3+, Er3+, Y3+) have been incorporated into pyrochlore lattice in (La0.2Nd0.2Y0.2Er0.2Yb0.2)2Zr2O7 (LNYEY) while larger ions (La3+, Nd3+, Sm3+, Eu3+) incorporated into fluorite lattice in (La0.2Nd0.2Sm0.2Gd0.2Yb0.2)2Zr2O7 (LNSGY). Due to high-entropy lattice distortion and resonant scattering derived from smaller ions Yb3+, Er3+, and Y3+, LNYEY shows a lower glass-like thermal conductivity (1.62-1.59 W m-1 K-1, 100-600℃) than LNSGY (1.74-1.75 W m-1 K-1, 100-600℃). Moreover, LNYEY and LNSGY exhibit enhanced Vickers’ hardness (LNYEY, Hv = 11.47 ± 0.41 GPa; LNSGY, Hv = 10.96 ± 0.26 GPa) and thermal expansion coefficients (LNYEY, 10.45 × 10-6 K-1, 1000℃; LNSGY, 11.02 × 10-6 K-1, 1000℃). These results indicate that dual-phase rare-earth-zirconate high-entropy ceramics could be desirable for thermal barrier coatings. 相似文献
2.
《Journal of the European Ceramic Society》2023,43(12):5339-5346
Anti-spinel oxide SrY2O4 has attracted extensive attention as a promising host lattice due to its outstanding high-temperature structural stability and large thermal expansion coefficient (TEC). However, the overhigh thermal conductivity limits its application in the field of thermal barrier coatings. To address this issue, a novel high-entropy Sr(Y0.2Sm0.2Gd0.2Dy0.2Yb0.2)2O4 ceramic was designed and synthesized for the first time via the solid-state method. It is found that the thermal conductivity of Sr(Y0.2Sm0.2Gd0.2Dy0.2Yb0.2)2O4 is reduced to 1.61 W·m−1·K−1, 53 % lower than that of SrY2O4 (3.44 W·m−1·K−1) at 1500 °C. Furthermore, reasonable TEC (11.53 ×10−6 K−1, 25 °C ∼ 1500 °C), excellent phase stability, and improved fracture toughness (1.92 ± 0.04 MPa·m1/2) remained for the high-entropy Sr(Y0.2Sm0.2Gd0.2Dy0.2Yb0.2)2O4 ceramic, making it a promising material for next-generation thermal barrier coatings. 相似文献
3.
《Journal of the European Ceramic Society》2022,42(5):2391-2399
Emerging of high-entropy ceramics has brought new opportunities for designing and optimizing materials with desired properties. In the present work, high-entropy rare-earth zirconates (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 and (Yb0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 are designed and synthesized. Both high-entropy ceramics exhibit a single pyrochlore structure with excellent phase stability at 1600 °C. In addition, the Yb-containing system possesses a high coefficient of thermal expansion (10.52 × 10?6 K-1, RT~1500 °C) and low thermal conductivity (1.003 W·m-1 K-1, 1500 °C), as well as excellent sintering resistance. Particularly, the Yb-containing system has significantly improved fracture toughness (1.80 MPa·mm1/2) when compared to that of lanthanum zirconate (1.38 MPa·mm1/2), making it a promising material for thermal barrier coatings (TBCs) applications. The present work indicates that the high-entropy design can be applied for further optimization of the comprehensive properties of the TBCs materials. 相似文献
4.
《Journal of the European Ceramic Society》2021,41(13):6670-6676
High-temperature thermal barrier coating (TBC) materials are desired for the development of high-efficient gas turbines and diesel engines. Herein, to meet up with this requirement, a new class of high-entropy fluorite-type oxides (HEFOs) has been synthesized via a solid-state reaction method. Comparing to La2Ce2O7, a promising TBC material, the HEFOs exhibit similar high thermal expansion coefficients (TECs) of 11.92×10−6∼12.11×10−6 K-1 at temperatures above 673 K but a better TEC matching performance at the temperature range of 473–673 K. It is also found that through tuning the average A-site cation radius, the TEC of the HEFOs could be tailored efficiently. The HEFOs also possess low thermal conductivities of 1.52-1.55 W∙m-1∙K-1 at room temperature, which is much lower than that of La2Ce2O7 and comparable to pyrochlores as Gd2Zr2O7. Moreover, the HEFOs display good sintering resistance and phase stability even at temperatures as high as 1873 K. The combination of these fascinating properties makes the HEFOs good candidates for thermal barrier coating and thermal insulating materials. 相似文献
5.
《Journal of the European Ceramic Society》2022,42(2):649-657
The corrosion resistance to calcium-magnesium-alumino-silicates (CMAS) is critically important for the thermal barrier coatings (TBCs). High-entropy zirconate (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 (HEZ) ceramics with low thermal conductivity, high coefficient of thermal expansion and good durability to thermal shock is expected to be a good candidate for the next-generation TBCs. In this work, the CMAS corrosion of HEZ at 1300°C was firstly investigated and compared with the well-studied La2Zr2O7 (LZ). It is found that the HEZ ceramics showed a graceful behavior to CMAS corrosion, obviously much better than the LZ ceramics. The HEZ suffered from CMAS corrosion only through dissolution and re-precipitation, while additional grain boundary corrosion existed in the LZ system. The precipitated high-entropy apatite showed fine-grained structure, resulting in a reaction layer without cracks. This study reveals that HEZ is a promising candidate for TBCs with extreme resistance to CMAS corrosion. 相似文献
6.
《Ceramics International》2023,49(1):766-772
Superb toughening is achieved by incorporating a secondary ferroelastic phase in high-entropy rare-earth zirconate 5RE2Zr2O7 (HZ). Here, we report an enhancement of 64% in fracture toughness through the addition of 30mol% high-entropy rare-earth aluminate 5REAlO3 (HA) to the HZ matrix (30HA). The aforementioned rare-earth elements RE are La, Sm, Eu, Gd, and Yb. The present dual-phase composite ceramic 30HA has a large fracture toughness of 2.77 ± 0.14 MPa m1/2, along with excellent high-temperature phase stability, resulting in good usage for potential thermal barrier coating applications. Particularly, the fracture toughness of the dual-phase composite ceramics at first increases to a maximum and then drops suddenly, as the mole fraction of HA increases from 0 to 50%. A clear definition of fitting parameters and their physical significance is provided for a better interpretation of the experimental data. The present toughening mechanism sheds light on microstructure engineering in high-entropy ceramics for excellent mechanical properties. 相似文献
7.
《Ceramics International》2022,48(7):9602-9609
The (La0.2Gd0.2Y0.2Yb0.2Er0.2)2(Zr1-xTix)2O7 (x = 0–0.5) high-entropy ceramics were successfully prepared by a solid state reaction method and their structures and thermo-physical properties were investigated. It was found that the high-entropy ceramics demonstrate pure pyrochlore phase with the composition of x = 0.1–0.5, while (La0.2Gd0.2Y0.2Yb0.2Er0.2)2Zr2O7 shows the defective fluorite structure. The sintered high-entropy ceramics are dense and the grain boundaries are clean. The grain size of high-entropy ceramics increases with the Ti4+ content. The average thermal expansion coefficients of the (La0.2Gd0.2Y0.2Yb0.2Er0.2)2(Zr1-xTix)2O7 high-entropy ceramics range from 10.65 × 10?6 K?1 to 10.84 × 10?6 K?1. Importantly, the substitution of Zr4+ with Ti4+ resulted in a remarkable decrease in thermal conductivity of (La0.2Gd0.2Y0.2Yb0.2Er0.2)2(Zr1-xTix)2O7 high-entropy ceramics. It reduced from 1.66 W m?1 K?1 to 1.20 W m?1 K?1, which should be ascribed to the synergistic effects of mass disorder, size disorder, mixed configuration entropy value and rattlers. 相似文献
8.
Xinyu Ping Bin Meng Chen Li Wu Lin YingQuan Chen CongCong Fang Han Zhang Wenke Liang Qian Zheng 《Journal of the American Ceramic Society》2022,105(7):4910-4920
A new series of rare-earth-cerate high-entropy ceramics with compositions of (La0.2Nd0.2Sm0.2Gd0.2Dy0.2)2Ce2O7 (HEC1), (La0.2Nd0.2Sm0.2Gd0.2Yb0.2)2Ce2O7 (HEC2), (La0.2Nd0.2Sm0.2Yb0.2Dy0.2)2Ce2O7 (HEC3), (La0.2Nd0.2Yb0.2Gd0.2Dy0.2)2Ce2O7 (HEC4), (La0.2Yb0.2Sm0.2Gd0.2Dy0.2)2Ce2O7 (HEC5) as well as a single component of Nd2Ce2O7 are fabricated via sintering the corresponding sol–gel-derived powders at 1600°C for 10 h. HEC1–5 samples exhibit a single-cerate phase with fluorite structure and high configurational entropy. Compared with Nd2Ce2O7, HEC1–5 samples have a lower grain growth rate owing to the sluggish diffusion effect. The chemical compositional uniformity of HEC1–5 as well as Nd2Ce2O7 does not apparently change after annealing at 1500°C for different time intervals (1, 6, 12, and 18 h). Compared with 8YSZ, HEC1–5 samples display the decreased thermal conductivity and increased thermal expansion coefficient. The lattice size disorder parameter of HEC1–5 is negatively related to the thermal conductivity in 26–450°C. Furthermore, HEC1–5 and Nd2Ce2O7 exhibit lower oxygen-ion conductivity, meaning an increased resistance to oxygen diffusion. 相似文献
9.
《Journal of the European Ceramic Society》2022,42(8):3480-3488
In this work, a novel high-entropy n-type thermoelectric material Sr0.9La0.1(Zr0.25Sn0.25Ti0.25Hf0.25)O3 with pure perovskite phase was prepared using a conventional solid state processing route. The results of TEM and XPS show that various types of crystal defects and lattice distortions, such as oxygen vacancies, edge dislocations, in-phase rotations of octahedron and antiparallel cation displacements coexist in this high-entropy ceramic. At 873 K, the high-entropy ceramics showed both a low thermal conductivity (1.89 W/m/K) and a high Seebeck coefficient (393 μV/K). This work highlights a way to obtain high-performance perovskite-type oxide thermoelectric materials through high-entropy composition design. 相似文献
10.
Zicheng Wei Qingqing Yang Bin Meng Chen Li Xinyu Ping Congcong Fang Han Zhang 《International Journal of Applied Ceramic Technology》2023,20(4):2392-2400
Six rare-earth tantalate high-entropy ceramics of (5RE.2)Ta3O9 (RE represents any five elements selected from La, Ce, Nd, Sm, Eu, Gd) were designed and prepared by spark plasma sintering process at 1400°C in this study. The (5RE.2)Ta3O9 ceramics only consist of a single-phase solid solution with perovskite structure. Their relative densities are all above 90%, and the average grain size is in the range of 1.47–2.92 μm. The thermal conductivity of (5RE.2)Ta3O9 ceramics is in 2.24–1.90 W m−1 K−1 (25°C–500°C), which is much lower than that of yttria-stabilized zirconia. In six samples, (La.2Nd.2Sm.2Gd.2Eu.2)Ta3O9 possesses a thermal conductivity of 1.90 W m−1 K−1, a thermal expansion coefficient of 3.47 × 10−6 K−1 (500°C), a Vickers hardness of about 7.33 GPa, and a fracture toughness of about 5.20 MPa m1/2, which are suitable for its application as thermal barrier coatings. 相似文献
11.
《Journal of the European Ceramic Society》2020,40(5):2120-2129
Using fluorite oxides as an example, this study broadens high-entropy ceramics (HECs) to compositionally-complex ceramics (CCCs) or multi-principal cation ceramics (MPCCs) to include medium-entropy and/or non-equimolar compositions. Nine compositions of compositionally-complex fluorite oxides (CCFOs) with the general formula of (Hf1/3Zr1/3Ce1/3)1-x(Y1/2X1/2)xO2-δ (X = Yb, Ca, and Gd; x = 0.4, 0.148, and 0.058) are fabricated. The phase stability, mechanical properties, and thermal conductivities are measured. Compared with yttria-stabilized zirconia, these CCFOs exhibit increased cubic phase stability and reduced thermal conductivity, while retaining high Young’s modulus (∼210 GPa) and nanohardness (∼18 GPa). Moreover, the temperature-dependent thermal conductivity in the non-equimolar CCFOs shows an amorphous-like behavior. In comparison with their equimolar high-entropy counterparts, the medium-entropy non-equimolar CCFOs exhibit even lower thermal conductivity (k) while maintaining high modulus (E), thereby achieving higher E/k ratios. These results suggest a new direction to achieve thermally-insulative yet stiff CCCs (MPCCs) via exploring non-equimolar and/or medium-entropy compositions. 相似文献
12.
《Ceramics International》2020,46(17):26626-26631
A new high-entropy monoboride (Mo0.2Ta0.2Ni0.2Cr0.2W0.2)B ceramic with a WB-type orthogonal structure was designed and synthesised by in-situ reactive hot pressing at 2000 °C and 30 MPa for 1.5 h under an argon atmosphere. The microstructure of the sintered samples was comprehensively characterised, and the formation of a high-entropy monoboride (Mo0.2Ta0.2Ni0.2Cr0.2W0.2)B ceramic was confirmed. Owing to the high density of the dislocations and strengthening metal-boron bonds, the high-entropy (Mo0.2Ta0.2Ni0.2Cr0.2W0.2)B ceramic exhibited a hardness of 48.51 ± 4.07 GPa, which enabled it to be classed as a new superhard material. In addition, the thermal conductivity (2.05 ± 0.10 W/(m·K) at 400 °C) and electric conductivity (132.30 S/cm) were determined. 相似文献
13.
Ferroelastic RETaO4 ceramics are promising thermal barrier coatings (TBCs) because of their attractive thermomechanical properties. The influence of crystal structure distortion degree on thermomechanical properties of RETaO4 is estimated in this work. The relationship between Young's modulus and TECs is determined. The highest TECs (10.7 × 10−6 K−1, 1200°C) of RETaO4 are detected in ErTaO4 ceramics and are ascribed to its small Young's modulus and low Debye temperature. The intrinsic lattice thermal conductivity (3.94-1.26 W m−1 K−1, 100-900°C) of RETaO4 deceases with increasing of temperature due to an elimination in thermal radiation effects. The theoretical minimum thermal conductivity (1.00 W m−1 K−1) of RETaO4 indicates that the experimental value is able to be reduced further. We have delved deeply into the thermomechanical properties of ferroelastic RETaO4 ceramics and have emphasized their high-temperature applications as TBCs. 相似文献
14.
Wang Shi-min Zhu Wei-wei Zhang Hong-song Wang Fei Sun Debing Yang Xian-feng Su Zhi-he Duan Qun-peng Mai Wen-peng 《Ceramics International》2019,45(8):10414-10419
For the development of ceramic candidates for thermal barrier coatings, two kinds of new ceramics, Y3Ce7Ta2O23.5 and Yb3Ce7Ta2O23.5, were synthesized by sintering at 1873?K for 10?h. The obtained samples were composed of a single fluorite-type phase, and their relative densities are greater than 90%. Because of phonon scattering caused by the complex lattice, the large number of oxygen vacancies, and substituted atoms, the thermal conductivity is lower than that of 8YSZ. The coefficients of thermal expansion (CTEs) of these two products are located in the range of 10.22–12.57?×?10?6/K and 9.62–12.66?×?10?6/K, respectively, from 323?K to 1473?K, and they also exhibit excellent phase stability up to 1473?K. However, their thermal conductivities and CTEs are lower than those of RE2Ce2O7 (RE?=?La, Nd, or Sm). 相似文献
15.
《Ceramics International》2021,47(21):29960-29968
Here, we report a novel high-entropy rare earth zirconate (HE-REZ) (Sm0.2Eu0.2Tb0.2Dy0.2Lu0.2)2Zr2O7 ceramic aerogel prepared through a sol-gel template method and high-temperature calcination followed by 3-D-structure reconstruction. The structural evolution and crystallisation behaviour of the prepared aerogel were characterised through scanning electron microscopy, X-ray diffraction and transmission electron microscopy. The results indicated that the as-prepared HE-REZ ceramic aerogels had a typical nanoporous structure. The HE-REZ ceramic aerogels thermally treated at 900 °C presented an ultralow room temperature thermal conductivity of 0.031 W/(m·K), high specific surface areas of 443.26 m2/g and a relatively high strength of 12.95 MPa. The effects of different calcination temperatures on the microstructure of the samples were also investigated. Therefore, the excellent insulation performance of these unique HE-REZ ceramic aerogels indicate that they can be used as high-temperature insulators for hypersonic vehicles in the future. 相似文献
16.
《Ceramics International》2023,49(18):29729-29735
Herein, five new La2Zr2O7 based high-entropy ceramic materials, such as (La0.2Ce0.2Gd0.2Y0.2Er0.2)2Zr2O7, (La0.2Ce0.2Gd0.2Er0.2Sm0.2)2Zr2O7, (La0.2Gd0.2Y0.2Er0.2Sm0.2)2Zr2O7, (La0.2Ce0.2Y0.2Er0.2Sm0.2)2Zr2O7, (La0.2Ce0.2Gd0.2Y0.2Sm0.2)2Zr2O7), were synthesized using a sol-gel and high-temperature sintering (1000 °C) method. The spark plasma sintered (SPS) (La0.2Ce0.2Gd0.2Er0.2Sm0.2)2Zr2O7 pellet shows a low thermal conductivity of 1.33 W m-1 K-1 at 773 K, and it also exhibits better CaO–MgO–Al2O3–SiO2 corrosion resistance than that of Y2O3 stabilized ZrO2. It shows that (La0.2Ce0.2Gd0.2Er0.2Sm0.2)2Zr2O7 has a promising application potential as a thermal barrier coating. 相似文献
17.
《Ceramics International》2023,49(16):26397-26410
Inspired by the high entropy effects of high-entropy components, a novel high-entropy rare-earth zirconate (La1/5Gd1/5Y1/5Sm1/5Yb1/5)2Zr2O7 (HEC-LZ) was designed and successfully synthesized in this work. In addition, two binary rare-earth doped zirconates (RE-LZ), (La1/3Sm1/3Yb1/3)2Zr2O7 (LSYZ) and (La1/3Gd1/3Y1/3)2Zr2O7 (LGYZ), were proposed using the same rare-earth elements for comparison. The thermal barrier coatings with LZ-based ceramic top layer were prepared by spray granulation, solid-phase synthesis and atmospheric plasma spraying techniques. The as-synthesized LZ-based ceramics are all dominated by the pyrochlore phase. Under 1000 °C, the thermal cycling performances of the three coatings were studied. The microstructure evolution and crack expansion during the failure process were investigated in detail. The strengthening mechanism and the cause of coating spallation are proposed in combination with mechanical properties and thermal matching analysis. The results showed that compared with the undoped LZ coating, the thermal shock life of LGYZ coating, LSYZ coating and HEC-LZ coating is improved by nearly 46%, 27% and 57%, respectively. Due to the characteristics of high randomness, HEC-LZ ceramic has a large lattice distortion than RE-LZ ceramics, resulting in a higher coefficient of thermal expansion and fracture toughness, which contributes to maintaining the structure stability of coatings under thermal stress. 相似文献
18.
《Journal of the European Ceramic Society》2020,40(7):2623-2633
Silica-bonded porous nano-SiC ceramics with extremely low thermal conductivity were prepared by sintering nano-SiC powder-carbon black template compacts at 600–1200 °C for 2 h in air. The microstructure of the silica-bonded porous nano-SiC ceramics consisted of SiC core/silica shell particles, a silica bonding phase, and hierarchical (meso/macro) pores. The porosity and thermal conductivity of the silica-bonded porous nano-SiC ceramics can be controlled in the ranges of 8.5–70.2 % and 0.057–2.575 Wm−1 K−1, respectively, by adjusting both, the sintering temperature and template content. Silica-bonded porous nano-SiC ceramics with extremely low thermal conductivity (0.057 Wm−1 K−1) were developed at a very low processing temperature (600 °C). The typical porosity, average pore size, compressive strength, and specific compressive strength of the porous nano-SiC ceramics were ∼70 %, 50 nm, 2.5 MPa, and 2.7 MPa·cm3/g, respectively. The silica-bonded porous nano-SiC ceramics were thermally stable up to 1000 °C in both air and argon atmospheres. 相似文献
19.
Yao Han Cuiwei Li Chao Bian Shibo Li Chang-An Wang 《Journal of the European Ceramic Society》2013,33(13-14):2573-2578
Porous anorthite ceramics with an ultra-low thermal conductivity of 0.018 W/m K have been fabricated by hydrous foam-gelcasting process and pressureless sintering method using γ-alumina, calcium carbonate and silica powders as raw materials. Microstructure and phase composition were analyzed by SEM and XRD respectively. Properties such as porosity, pore size distribution and thermal conductivity were measured. High porosity (69–91%) and low thermal conductivity (0.018–0.13 W/m K) were obtained after sintering samples with different catalyst additions at 1300–1450 °C. Porosity, pore size, pore structure and grain size had obvious effect on heat conduction, resulting in the low thermal conductivity. The experimental thermal conductivity data of porous anorthite ceramics were found to be fit well with the computed values derived from a universal model. 相似文献
20.
《Ceramics International》2016,42(12):13491-13496
Two kinds of novel Ln2LaTaO7 (Ln=Er and Yb) ceramics were prepared via high-temperature solid reaction method. The phase composition, micro-morphology and thermophysical properties were investigated. Results indicate that pure Ln2LaTaO7 ceramics with single fluorite-type structure are synthesized successfully. The thermal conductivities of Er2LaTaO7 and Yb2LaTaO7 are in the range of 1.22–1.43 W/m K and 1.17–1.51 W/m K, respectively, which are much lower than that of YSZ. The lower thermal conductivity can be attributed to the phonon scattering caused by oxygen vacancies and the substituting atoms. The average thermal expansion coefficients of Yb2LaTaO7 and Er2LaTaO7 are 9.94×10−6/K and 9.63×10−6/K, respectively. As compared with Yb2LaTaO7, the higher thermal expansion coefficient of Er2LaTaO7 can be ascribed to its lower ionic-bond strength between cations at sites A and B. 相似文献