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1.
Emmanuel E. Boakye Thomas S. Key Pavel Mogilevsky Samuel J. Opeka Randall Corns Randall S. Hay Michael K. Cinibulk 《Journal of the European Ceramic Society》2021,41(5):3132-3140
Solutions of YPO4 were used to precipitate YPO4 on pre-oxidized Hi-Nicalon-S SiC fibers. Tows of the coated fibers were then infiltrated with a preceramic polymer loaded with SiC particles to form mini-composites. During pyrolysis of the matrix, SiO2 and YPO4 on the fibers reacted and formed a Y2Si2O7 fiber matrix interphase. Mini-composites were exposed to steam at 1000 °C for 10, 50, and 100 h, tensile tested, and the effect of oxidation in steam on the functionality of the Y2Si2O7 fiber coating was investigated. The minicomposites oxidized at 1000 °C for 10 h retained 100 % of their unoxidized strength, and those oxidized for 50 and 100 h retained 92 % and 90 % of unoxidized strength, respectively. Strength retention and fiber pullout in both unoxidized and oxidized minicomposites suggests that the Y2Si2O7 interphase was effective in maintaining a weak fiber-matrix interface. 相似文献
2.
Emmanuel E. Boakye Pavel Mogilevsky Triplicane A. Parthasarathy Kristin A. Keller Randall S. Hay Michael K. Cinibulk 《Journal of the American Ceramic Society》2016,99(2):415-423
Rare‐earth disilicates (RE2Si2O7) are investigated for use as oxidation‐resistant alternatives to carbon or BN fiber–matrix interphases in ceramic matrix composites (CMC). Dense α, β, γ‐Y2Si2O7, and γ‐Ho2Si2O7 pellets were formed at 64 MPa and 1050°C–1200°C for 1 h using the field‐assisted sintering technique (FAST). Pellet modulus was measured using nanoindentation, and Vickers hardness was measured at loads of 100, 500, and 1000 g. The sliding stress of SCS‐0 SiC fibers incorporated in α‐, β‐, and γ‐RE2Si2O7 matrices were measured by fiber push‐out. Deformation of RE2Si2O7 after indentation and after fiber push‐out was characterized by TEM. Implications of the results for use of RE2Si2O7 as a fiber–matrix interphase in CMCs are discussed. 相似文献
3.
Emmanuel E. Boakye Pavel Mogilevsky Thomas S. Key Triplicane A. Parthasarathy Kristin A. Keller Samuel J. Opeka Randall S. Hay Michael K. Cinibulk Randall Corns 《Journal of the American Ceramic Society》2019,102(10):5725-5737
Y2Si2O7 coatings were formed on Hi-Nicalon-S SiC fibers by reaction of solution-derived YPO4 coatings with glass SiO2 scales formed by fiber oxidation. Two oxidation methods were used: pre-oxidation, where fibers were oxidized prior to YPO4 coating, or post-oxidation, where fibers were first coated with YPO4 and then oxidized. Fibers with YPO4/SiO2 films were heat-treated in argon at 1200°C for 20 hours to react YPO4 and SiO2 to Y2Si2O7. The effects of SiO2 to YPO4 film thicknesses on fiber strength and on the Y2Si2O7formation kinetics were investigated. An optimized process to obtain single-phase continuous Y2Si2O7 coatings on Hi-Nicalon-S fibers with low loss in fiber strength is suggested. 相似文献
4.
Ling Pan Pengju Chen Peng Xiao Ling He Wei Zhou Yang Li 《International Journal of Applied Ceramic Technology》2023,20(3):1740-1752
The mullite and ytterbium disilicate (β-Yb2Si2O7) powders as starting materials for the Yb2Si2O7/mullite/SiC tri-layer coating are synthesized by a sol–gel method. The effect of SiC whiskers on the anti-oxidation properties of Yb2Si2O7/mullite/SiC tri-layer coating for C/SiC composites in the air environment is deeply studied. Results show that the formation temperature and complete transition temperature of mullite were 800–1000 and 1300°C, respectively. Yb2SiO5, α-Yb2Si2O7, and β-Yb2Si2O7 were gradually formed between 800 and 1000°C, and Yb2SiO5 and α-Yb2Si2O7 were completely transformed into β-Yb2Si2O7 at a temperature above 1200°C. The weight loss of Yb2Si2O7/(SiCw–mullite)/SiC tri-layer coating coated specimens was 0.15 × 10−3 g cm−2 after 200 h oxidation at 1400°C, which is lower than that of Yb2Si2O7/mullite/SiC tri-layer coating (2.84 × 10−3 g cm−2). The SiC whiskers in mullite middle coating can not only alleviate the coefficient of thermal expansion difference between mullite middle coating and β-Yb2Si2O7 outer coating, but also improve the self-healing performance of the mullite middle coating owing to the self-healing aluminosilicate glass phase formed by the reaction between SiO2 (oxidation of SiC whiskers) and mullite particles. 相似文献
5.
《Journal of the European Ceramic Society》2017,37(16):5177-5191
Environmental barrier coatings are required to protect Si3N4 against hot gas corrosion and enable its application in gas turbines, among which yttrium and ytterbium silicate-coatings stand out. Thus, the polymer-derived ceramic route was used to synthesize these silicates for basic investigations regarding their intrinsic properties from a mixture of Y2O3 or Yb2O3 powders and the oligosilazane Durazane 1800. After pyrolysis above 1200 °C in air, the silicates are predominant phases. The corrosion behaviour of the resulting composites was tested at 1400 °C for 80 h in moist environments. The material containing x2-Yb2SiO5 and Yb2Si2O7 undergoes the lowest corrosion rate (−1.8 μg cm−2 h−1). Finally, the processing of Y2O3/Durazane 1800 as well-adherent, crack-free and thick (40 μm) coatings for Si3N4 was achieved after pyrolysis at 1400 °C in air. The coating consisted of an Y2O3/Y2SiO5 top-layer and an Y2O3/Y2Si2O7 interlayer due to the interaction of the coating system with the substrate. 相似文献
6.
Pavel Mogilevsky Emmanuel E. Boakye Thomas S. Key Triplicane A. Parthasarathy Randall S. Hay Michael K. Cinibulk 《Journal of the American Ceramic Society》2019,102(1):167-177
It is shown using thermodynamic analysis and kinetic modeling that a processing window exists for the formation of Y2Si2O7 coatings on SiC. The proposed method is validated using an experimental procedure in which the in situ formation of Y2Si2O7 on a commercial SiC-based fiber is demonstrated. The method involves the deposition of YPO4 on preoxidized fine diameter SiC-based fibers, and heat treating the coated fibers within a calculated processing window of oxygen partial pressure, temperature, degree of preoxidation, and coating thickness. The results are promising for the development of environmentally resistant interfacial coatings for SiC-fiber reinforced SiC-based matrix composites. The proposed and validated approach allows a low-cost method to obtain continuous hermetic coatings on SiC fibers with interfacial properties adequate for tough composite behavior that resists degradation under turbine engine conditions. 相似文献
7.
Texture,microstructures, and mechanical properties of AlN‐based ceramics with Si3N4–Y2O3 additives
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Cong Liu Wei‐Ming Guo Shi‐Kuan Sun Ji Zou Shang‐Hua Wu Hua‐Tay Lin 《Journal of the American Ceramic Society》2017,100(8):3380-3384
Textured AlN‐based ceramics with improved mechanical properties were prepared by hot pressing using Si3N4 and Y2O3 as additives. The introduction of Si3N4–Y2O3 into AlN matrix led to the formation of secondary Y3AlSi2O7N2 and fiber‐like 2Hδ AlN‐polytypoid phases, the partial texture of all crystalline phases, and the fracture mode change from intergranular to transgranular. Consequently, Vickers hardness, fracture toughness and flexural strength of AlN‐based ceramics by the replacement of Y2O3 by Si3N4–Y2O3 increased significantly from 10.4±0.3 GPa, 2.4±0.3 MPa m½ and 333.3±10.3 MPa to 14.2±0.4 GPa, 3.4±0.1 MPa m½ and 389.5±45.5 MPa, respectively. 相似文献
8.
Dianying Chen Aaron Pegler Mitch Dorfman 《Journal of the American Ceramic Society》2020,103(9):4840-4845
Yb2Si2O7/Si bilayer environmental barrier coatings (EBCs) on SiC ceramic substrate were produced by low pressure plasma spray (LPPS) process. Phase composition, microstructure, and thermal durability of LPPS Yb2Si2O7/Si coating were investigated. XRD analysis indicated that the coating is mainly composed of Yb2Si2O7 with ~15.5v% Yb2SiO5 phases. The LPPS EBCs have a dense microstructure with porosity less than 4%. Adhesion strength measurement indicated the LPPS EBCs have an average adhesion strength of 29.1 ± 0.8 MPa. Furnace cycle test (FCT) on the coatings in air at 1316°C was performed and the test ran for 900 cycles and there was no coating spallation/failure for LPPS Yb2Si2O7/Si EBCs. The FCT results demonstrated the excellent thermal cycle durability of LPPS EBCs. Oxidation kinetics investigation of LPPS EBCs in flowing 90% H2O (g)+10% air at 1316°C showed that the thermally grown oxide (TGO) growth rate is close to the oxidation rate of pure Si in dry air and is significantly lower than that in water vapor environment. The LPPS process is promising in making highly durable Yb2Si2O7-based dense EBCs by impeding diffusion and ingression of water vapor/O2. 相似文献
9.
Liu Miao Huang Jianfeng Zhang Yutao Deng Fei Cao Liyun Wu Jianpeng 《Journal of Coatings Technology and Research》2009,6(4):531-535
Oxidation-resistant yttrium silicates coatings for SiC precoated carbon/carbon composites were prepared by a novel hydrothermal
electrophoretic deposition process. Sonochemical-synthesized yttrium silicates nanocrystallites, isopropanol, and iodine were
respectively used as source materials, solvent, and charging agent during the deposition. Phase compositions, surface and
cross-section microstructures of the as-prepared multilayer coatings were characterized by an X-ray diffractometer (XRD) and
a scanning electron microscopy (SEM). The influence of deposition temperatures on the phase, microstructure, and oxidation
resistance of the multilayer coated C/C composites was particularly investigated. Results show that the as-prepared outer
coatings are composed of yttrium silicates crystallites with a main phase of Y2Si2O7 and Y2SiO5. The thickness and density of the yttrium silicates coatings are improved with the increase of deposition temperature. Compared
with SiC coating prepared by pack cementation, the multilayer coatings prepared by pack cementation with a later hydrothermal
electrophoretic deposition process exhibit better antioxidation properties. The as-prepared multilayer coatings can effectively
protect C/C composites from oxidation at 1773 K in air for 35 h with a weight loss of 0.32 × 10−3 g/cm2. 相似文献
10.
Jiahao Yang Zahoor Ahmad Mingming Zhu Jianjun Chen 《Journal of the American Ceramic Society》2023,106(10):6130-6140
In this study, the high-content SiCnw reinforced SiC ceramic matrix composites (SiCnw/SiC CMC) were successfully fabricated by hot pressing β-SiC and sintering additive (Al2O3-Y2O3) with boron nitride interphase modification SiCnw. The effects of sintering additive content and mass fraction (5–25 wt%) of SiCnw on the density, microstructure, and mechanical properties of the composites were investigated. The results showed that with the increase of sintering additives from 10 wt% to 12 wt%, the relative density of the SiCnw/SiC CMC increased from 97.3% to 98.9%, attributed to the generated Y3Al5O12 (YAG) liquid phase from the Al2O3-Y2O3 that promotes the rearrangement and migration of SiC grains. The comprehensive performance of the obtained composite with 15 wt% SiCnw possessed the optimal flexural strength and fracture toughness of 524 ± 30.24 MPa and 12.39 ± 0.49 MPa·m1/2, respectively. Besides, the fracture mode of the composites with 25 wt% SiCnw content revealed a pseudo-plastic fracture behavior. It concludes that the 25 wt% SiCnw/SiC CMC was toughened by the fiber pull-outs, debonding, bridging, and crack deflection that can consume plenty of fracture energy. The strategy of SiC nanowires worked as a main bearing phase for the fabrication of SiC/SiC CMC providing critical information for understanding the mechanical behavior of high toughness and high strength SiC nanoceramic matrix composites. 相似文献
11.
Ziqi Sun Ling Wu Meishuan Li Yanchun Zhou 《Journal of the American Ceramic Society》2013,96(10):3228-3238
In this work, novel Y2Si2O7/ZrO2 composites were developed for structural and coating applications by taking advantage of their unique properties, such as good damage tolerance, tunable mechanical properties, and superior wear resistance. The γ‐Y2Si2O7/ZrO2 composites showed improved mechanical properties compared to the γ‐Y2Si2O7 matrix material, that is, the Young's modulus was enhanced from 155 to 188 GPa (121%) and the flexural strength from 135 to 254 MPa (181%); when the amount of ZrO2 was increased from 0 to 50 vol%, the γ‐Y2Si2O7/ZrO2 composites also presented relatively high facture toughness (>1.7 MPa·m1/2), but this exhibited an inverse relationship with the ZrO2 content. The composition–mechanical property–tribology relationships of the Y2Si2O7/ZrO2 composites were elucidated. The wear resistance of the composites is not only influenced by the applied load, hardness, strength, toughness, and rigidity but also effectively depends on micromechanical stability properties of the microstructures. The easy growth of subcritical microcracks in Y2Si2O7 grains and at grain boundaries significantly contributes to the macroscopic fracture toughness, but promotes the pull‐out of individual grains, thus resulting in a lack of correlation between the wear rate and the macroscopic fracture toughness of the composites. 相似文献
12.
Li-Xiang Wu Lin-Lin Zhu Yang You Rui-Lin Lin Qing-Qing Liu Wei-Ming Guo Hua-Tay Lin Kevin Paul Plucknett 《Ceramics International》2021,47(1):935-942
Dense pressure-sintered reaction-bonded Si3N4 (PSRBSN) ceramics were obtained by a hot-press sintering method. Precursor Si powders were prepared with Eu2O3–MgO–Y2O3 sintering additive. The addition of Eu2O3–MgO–Y2O3 was shown to promote full nitridation of the Si powder. The nitrided Si3N4 particles had an equiaxial morphology, without whisker formation, after the Si powders doped with Eu2O3–MgO–Y2O3 were nitrided at 1400 °C for 2 h. After hot pressing, the relative density, Vickers hardness, flexural strength, and fracture toughness of the PSRBSN ceramics, with 5 wt% Eu2O3 doping, were 98.3 ± 0.2%, 17.8 ± 0.8 GPa, 697.0 ± 67.0 MPa, and 7.3 ± 0.3 MPa m1/2, respectively. The thermal conductivity was 73.6 ± 0.2 W m?1 K?1, significantly higher than the counterpart without Eu2O3 doping, or with ZrO2 doping by conventional methods. 相似文献
13.
High temperature oxidation resistance of Y2O3 modified ZrB2-SiC coating for carbon/carbon composites
Hanchun Ma Qiang Miao Wenping Liang Yangyang Liu Hao Lin Hairui Ma Shiwei Zuo Lin Xue 《Ceramics International》2021,47(5):6728-6735
To protect carbon/carbon (C/C) composites from oxidation at high temperature, Y2O3 modified ZrB2-SiC coating was fabricated on C/C composites by atmospheric plasma spraying. The microstructure and chemical composition of the coatings were characterized by SEM, EDS, and XRD. Experiment results showed that the coating with 10 wt% Y2O3 presented a relatively compact surface without evident holes and cracks. No peeling off occurred on the interface between the coating and substrate. The ZSY10 coating underwent oxidation at 1450 °C for 10 h with a mass loss of 5.77%, while that of ZS coating was as high as 16.79%. The existence of Y2O3 played an important role in inhibiting the phase transition of ZrO2, thus avoiding the cracks caused by the volume expansion of the coating. Meanwhile, Y2SiO5 and ZrSiO4 had a similar coefficient of thermal expansion (CTE), which could relieve the thermal stress inside the coating. The ceramic phases Y2SiO5, Y2Si2O7 and ZrSiO4 with high thermal stability and low oxygen permeability reduced the volatilization of SiO2. 相似文献
14.
《Journal of the European Ceramic Society》2023,43(13):5652-5661
Dense multilayer gradient rare earth disilicate (γ-Y2Si2O7 /β-Yb2Si2O7 /β-Lu2Si2O7) coatings were in-situ prepared by melt-infiltration /sintering procedure on porous Si3N4 ceramics for water resistance. Experimental and numerical simulation methods were used to study their thermal shock behavior. As a control, thermal shock behavior of pure γ-Y2Si2O7 coatings were also compared. FEM results showed that the gradient design of modulus in ceramic coating can effectively avoid the mismatch of mechanical properties between coating layer and internal substrate, reducing the transient thermal stress in each layer during thermal shock. All of the pure γ-Y2Si2O7 coatings were failed after thermal shock tests with ΔT ≈ 1200 ℃. However, when sintering temperature of multi-layer disilicate coatings were higher than 1400 ℃, the water absorption rates after thermal shock were all less than 5%, still showing good waterproof performance. The gradient design of modulus could effectively improve the structural stability of ceramic coatings. 相似文献
15.
《Ceramics International》2020,46(11):18698-18706
Three different kinds of thermal barrier coatings (TBCs) — 8YSZ, 38YSZ and a dual-layered (DL) TBCs with pure Y2O3 on the top of 8YSZ were produced on nickel-based superalloy substrate by air plasma spraying (APS). The Calcium–Magnesium–Aluminum-Silicate (CMAS) corrosion resistance of these three kinds of coatings were researched via burner rig test at 1350 °C for different durations. The microstructures and phase compositions of the coatings were characterized by SEM, EDS and XRD. With the increase of Y content, TBCs exhibit better performance against CMAS corrosion. The corrosion resistance against CMAS of different TBCs in descending was 8YSZ + Y2O3, 38YSZ and 8YSZ, respectively. YSZ diffused from TBCs into the CMAS, and formed Y-lean ZrO2 in TBCs because of the higher diffusion rate and solubility of Y3+ in CMAS than Zr4+. At the same time, 38YSZ/8YSZ + Y2O3 reacts with CAMS to form Ca4Y6(SiO4)6O/Y4·67(SiO4)3O with dense structure, which can prevent further infiltration of CMAS. The failure of 8YSZ coatings occurred at the interface between the ceramic coating and the thermally grown oxide scale (TGO)/bond coating. During the burner rig test, the Y2O3 layer of the DL TBCs peeled off progressively and the 8YSZ layer exposed gradually. DL coatings keep roughly intact and did not meet the failure criteria after 3 h test. 38YSZ coating was partially ablated, the overall thickness of the coating is thinned simultaneously after 2 h. Therefore, 8YSZ + Y2O3 dual-layered coating is expected to be a CMAS corrosion-resistant TBC with practical properties. 相似文献
16.
Shu‐Bin Wang Yan‐Ru Lu Yan‐Xia Chen 《International Journal of Applied Ceramic Technology》2015,12(6):1140-1147
Single‐phase β‐Yb2Si2O7 was synthesized by solid‐state reaction using Yb2O3 and SiO2 gel. SiO2 gel significantly decreased the synthesis temperature and shortened the holding time. Bulk Yb2Si2O7 was obtained by pressureless sintering. Grain size, relative density (92.9%), and flexural strength [(182.3 ± 2.0) MPa] were enhanced as the sintering temperature increased and equiaxed grains were obtained with an average grain size of approximately 3 μm. Bulk Yb2Si2O7 possessed a suitable thermal expansion coefficient [(4.64 ± 0.01) × 10?6/K] between 473 and 1573 K, and the thermal conductivities at 300 and 1400 K were 4.31 and 2.27 W/m·K, respectively. 相似文献
17.
Junjie Xu Yanbo Liu Zhuang Ma Shizhen Zhu Yijin Wang Haikun Chen Kangzhi Ma 《Ceramics International》2021,47(1):400-408
To improve the emissivity of ZrB2/SiC coatings for serving in more serious environment, ZrB2/SiC coatings with varying contents of high emissivity Sm2O3 were fabricated using atmospheric plasma spraying. The microstructure, infrared radiative performance and anti-ablation behaviour of the modified coatings were investigated. The results showed that as the content of Sm2O3 increased, the density of the coatings increased because of the low melting point of Sm2O3. When the content of Sm2O3 was 10 vol%, the coating had the highest emissivity in the 2.5–5 μm band at 1000 °C, up to 0.85, because of the oxygen vacancies promoting additional electronic transitions. Due to the high emissivity, the surface temperature of the coating modified with 10 vol% Sm2O3 decreased by 300 °C, which led to little volatilisation of the sealing phase. Further, the mass ablation ratio of the above coating was 3.19 × 10?4 g/s, decreasing 31% compared to that of a ZrB2/SiC coating. The formed dense surface structure of the coatings showed considerable oxygen obstructive effects. These findings indicate that the modified coatings show considerable anti-ablation performance, which provides effective anti-ablation protection for the C/C composite substrate. 相似文献
18.
《Journal of the European Ceramic Society》2023,43(14):6427-6439
The oxidation of SiC and the formation of a thermally grown oxide layer (TGO) limit the lifetime of environmental barrier coatings. Thus, this paper focuses on the deposition of denser Yb2Si2O7 coatings using electrophoretic deposition to reduce the TGO growth rate. The findings showed densification for Yb2Si2O7 can be achieved with an optimized sintering profile (heating/cooling rate, temperature, and time). However, the addition of 1.5 wt% of Al2O3 to Yb2Si2O7 promoted densification and lowered the required sintering temperature, 1380 °C using 2 °C/min heating/cooling rate for 10 h provided efficient coating density. Moreover, adding Al2O3 reduced the TGO growth rate by more than 70 % compared to the Al2O3-free coatings, without cracking in TGO after 150 h of thermal ageing at 1350 °C. Results within this study suggest electrophoretic deposition with Al2O3 addition produces promising Yb2Si2O7 environmental barrier coatings on SiC substrate with low oxidation rates and increased lifetime. 相似文献
19.
《Ceramics International》2023,49(16):26767-26777
In order to improve the oxidation resistance of the Ta substrate, a novel two-step process including molten salt electrodeposition (Na2WO4-WO3 system) and halide activated pack cementation was adopted to prepare a WSi2–TaSi2 coating on tantalum substrate. During the electrodeposition process, dense tungsten coatings were fabricated at current densities of 30 mA/cm2, 40 mA/cm2 and 50 mA/cm2. It was observed that the grain size exhibited a log-normal distribution. When the current density was 40 mA/cm2, the grain size and flattest surface of the tungsten coating reached 9.50 ± 0.23 μm and 6.792 μm, respectively. When performing the static oxidation test, the WSi2–TaSi2 coating could effectively protect the Ta substrate oxidized at 1600 °C for 30 h. This is attributed to the presence of dense SiO2 and Ta2O5, which acted as a protective layer and suppressed the further penetration of oxygen. Furthermore, due to the matching thermal expansion coefficient between each layer and the sealing ability of semi-molten SiO2, the four-layer SiO2–W5Si3–WSi2–Ta5Si3 coating could successfully pass 721 thermal shock tests from 1600 °C to room temperature. 相似文献
20.
Carlos G. Levi 《Journal of the American Ceramic Society》2013,96(4):1300-1308
Application of SiC‐based ceramic matrix composites (CMCs) in combustion environments demands the use of an environmental barrier coating (EBC) to prevent volatilization of the protective SiO2 scale in flowing water vapor. The EBC only provides protection while present on the surface; cracking and spallation of the coating leaves the underlying SiC vulnerable to the oxidation–volatilization processes. A robust matrix material chemically tailored to regrow a yttrium silicate scale in the event of EBC loss has been developed by incorporating yttrium bearing species including YB2, Y2O3, and Y5Si3 into the SiC. During oxidation a borosilicate glass helps seal cracks while Y2O3 and SiO2 react to form Y2Si2O7 for environmental protection. Candidate compositions were oxidized for 10 min to 100 h at 1400°C and for 24 h at 1500°C to understand the scale growth. The prospects for effectively applying this approach in CMCs are discussed. 相似文献