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1.
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
2.
Winnie Tan Mitchell Adducci Rodney Trice 《Journal of the American Ceramic Society》2014,97(8):2639-2645
Rare‐earth modified ZrB2–SiC coatings were prepared via mechanical mixing Sm2O3 or Tm2O3 powders with spray‐dried ZrB2, or by chemically doping samarium ions into spray‐dried ZrB2. In either approach, SiC powders were also added and coatings were fabricated via shrouded air plasma spray. An oxyacetylene torch was utilized to evaluate the coatings under high heat flux conditions for hold times of 30 and 60 s. The resulting phases and microstructures were evaluated as a function of rare‐earth type, modification approach, and ablation time. A brittle m‐ZrO2 scale was observed in the ZrB2/SiC‐only coating after ablative tests; during cooling this scale detached from the unreacted coating. In contrast, rare‐earth modified coatings formed a protective oxide scale consisting primarily of either Sm0.2Zr0.8O1.9 or Tm0.2Zr0.8O1.9, along with small amount of m‐ZrO2. These rare‐earth oxide scales displayed high thermal stability and remained adhered to the unreacted coating during heating and cooling, offering additional oxidation protection. 相似文献
3.
Shunjie Deng Chi Jiang Tianwei Liu Yin Hu Jingjing Ding Maobing Shuai 《Journal of the American Ceramic Society》2019,102(3):1362-1372
Al2O3-Y2O3-SiC composite coatings were prepared on depleted uranium by cathode plasma electrolytic deposition in Al(NO3)3, Y(NO3)3, SiC nanoparticles and anhydrous ethyl alcohol mixture. The resulting coating consisted of an inner barrier layer and an outer porous layer. The SiC nanoparticles were incorporated into the composite coating and decreased the coating porosity by filling the pores. The potentiodynamic polarization test and neutral salt spray test revealed that the corrosion resistance of depleted uranium was enhanced by the composite coating. Moreover, with increasing the content of SiC nanoparticles in the coating, the coating corrosion resistance was improved gradually. 相似文献
4.
《Ceramics International》2022,48(4):5187-5196
To investigate the silicon/graphite ratio and temperature on preparation and properties of ZrB2–SiC coatings, ZrB2, silicon, and graphite powders were used as pack powders to prepare ZrB2–SiC coatings on SiC coated graphite samples at different temperatures by pack cementation method. The composition, microstructure, thermal shock, and oxidation resistance of these coatings were characterized and assessed. High silicon/graphite ratio (in this case, 2) did not guarantee higher coating density, instead could be harmful to coating formation and led to the lump of pack powders, especially at temperatures of 2100 and 2200 °C. But residual silicon in the coating is beneficial for high density and oxidation protection ability. The SiC/ZrB2–SiC (ZS50-2) coating prepared at 2000 °C showed excellent oxidation protective ability, owing to the residual silicon in the coating and dense coating structure. The weight loss of ZS50-2 after 15 thermal shocks between 1500 °C and room temperature, and oxidation for 19 h at 1500 °C are 6.5% and 2.9%, respectively. 相似文献
5.
《Ceramics International》2019,45(10):13004-13010
In this study, the REO-HfO2 (REO = Tb4O7, Gd2O3 and Sm2O3) coatings and pure HfO2 coatings were prepared by atmospheric plasma spraying. The chemical compositions, morphologies, infrared radiation performance and thermal resistances of the coatings were systematically investigated. The experimental results showed that the Tb4O7-HfO2, Gd2O3-HfO2, Sm2O3-HfO2 and pure HfO2 coatings had infrared emissivity values of 0.863, 0.852, 0.854 and 0.621, respectively, at room temperature. Based on the phase analysis, the higher infrared emissivity of the REO-HfO2 coatings could be attributed to the fact that the newly formed RE2Hf2O7 (RE = Tb, Gd and Sm) phase, which had a defective fluorite-type structure, and the RE3+ ions enhanced the lattice absorption and electron absorption. Additionally, the Tb4O7-HfO2 coating exhibited a relatively higher infrared emissivity than those of the Gd2O3-HfO2 and Sm2O3-HfO2 coating over the wavelength range of 1–15 μm, which was due to the relatively higher vibrational frequency of the TbO bond in RE2Hf2O7 (RE = Tb, Gd and Sm) and the transformation of Tb3+ into Tb4+ in the Tb4O7-HfO2 system. In addition, the REO-HfO2 ceramic coatings exhibited excellent thermal resistance, which could withstand high-temperature treatment at 1600 °C for at least 50 h without undergoing a phase change and exfoliation, and the infrared emissivity at different temperatures hardly changed after thermal treatment. 相似文献
6.
《Ceramics International》2016,42(16):18657-18665
The present study has been conducted in order to investigate the effect of the surface morphology of SiC inner coating on the bonding strength and ablation resistance of the sprayed ZrB2-SiC coating for C/C composites. The microstructure of SiC inner coatings prepared by chemical vapor deposition and pack cementation at different temperatures were analyzed by X-ray diffraction, scanning electron microscopy, and 3D Confocal Laser Scanning Microscope. Tensile bonding strength and oxyacetylene ablation testing were used to characterize the bonding strength and ablation resistance of the sprayed ZrB2-SiC coating, respectively. Results show that SiC inner coating prepared by chemical vapor deposition has a smooth surface, which is not beneficial to improve the bonding strength and ablation resistance of the sprayed ZrB2-SiC coating. SiC inner coating prepared by pack cementation at 2000 °C has a rugged surface with the roughness of 72.15 µm, and the sprayed ZrB2-SiC coating with it as inner layer exhibits good bonding strength and ablation resistance. 相似文献
7.
《Ceramics International》2022,48(18):26003-26012
In this study, a high-entropy RMgAl11O19 (HE-RMA, R = La, Pr, Nd, Sm, Gd) and LaMgAl11O19 (LMA) coatings were fabricated by atmospheric plasma spraying. The phase composition, microstructure, thermal stability, infrared emissivity performance and shock resistance were comparatively characterized. The results showed that doping multiple rare-earth cations could be conductive to enhance the infrared emissivity. The as-sprayed HE-RMA coating exhibited the highest infrared emissivity, which reached up to 0.971 at 1000 °C. The reason for the improvement of the infrared emissivity was attributed to introduced impurity energy level resulting from doping cations, which could reduce the forbidden bandwidth and increase probability of electronic transition. Meanwhile, HE-RMA coating exhibited better shock resistance at 1100 °C due to superior fracture toughness (1.84 ± 0.41 MPa·m1/2) during thermal cycling test at 1100 °C. In addition, HE-RMA coating still exhibited high infrared emissivity (0.932 at 1000 °C) at 1100 °C annealing for 100 h with only a slight reduction. 相似文献
8.
《Ceramics International》2023,49(2):1700-1709
Carbon fiber-reinforced silicon carbide (C/SiC) composites are important candidates for laser protection materials. In this study, ablation mechanism of C/SiC coated with ZrO2/Mo and ZrB2–SiC/ZrO2/Mo under laser irradiation was studied. ZrB2–SiC multiphase ceramic and ZrO2 ceramic were successfully coated on C/SiC composite by atmospheric plasma spraying technology with Mo as transition layer. Phase evolution and morphology of composite were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Moreover, ablation behavior of the composite was investigated by laser confocal microscopy. Results showed that ablation mechanism of C/SiC composite was controlled by phase transformation, thermal reaction, and thermal diffusion, with solid–liquid transition of ZrB2 and ZrO2 being dominant factor. Endothermic reaction and good thermal diffusivity of coatings were also important factors affecting ablation performance. Reflectivity effect of ZrO2 coating was limited under high-energy laser irradiation. Compared with ZrO2/Mo single-phase-monolayer coating, designed ZrB2–SiC/ZrO2/Mo coating showed better ablation performance, and breakdown time of C/SiC increased from 10 to 40 s. The depletion of liquid phase in molten pool was identified as an important factor responsible for rapid failure of C/SiC. The coating failed when the entire liquid phase was consumed within molten pool, followed by rapid damage of C/SiC substrate. Results of this study can provide theoretical guidance and research ideas for design and application of laser protective materials. 相似文献
9.
《Journal of the European Ceramic Society》2014,34(5):1243-1253
Rare-earth doped yttria-stabilized zirconia (YSZ) coatings with lower thermal conductivity have been fabricated via suspension plasma spray by dissolving rare-earth nitrates into YSZ powder-ethanol suspensions prior to plasma spraying. The effect of dopant concentration and dopant type on properties of the coatings was determined by comparing two coatings containing different concentrations of the same dopant pair (Nd2O3/Yb2O3), and three coatings having similar concentrations of different dopant pairs (Nd2O3/Yb2O3, Nd2O3/Gd2O3, and Gd2O3/Yb2O3). The porosity content of the coating was found to increase with increased total rare-earth dopant concentration but did not significantly change with dopant pairs. The cross-sectional morphology of every coating displayed a cauliflower-like structure. However, the most heavily doped coating exhibited a larger surface roughness and feathery features in the columnar structures. The thermal conductivity measurement showed that the thermal conductivity decreased with increased Nd2O3/Yb2O3 concentration. Among coatings containing different dopant pairs, the Gd2O3/Yb2O3 doped coating exhibited lowest conductivity. 相似文献
10.
Erica L. Corral 《Journal of the American Ceramic Society》2014,97(9):3004-3011
Carbon–carbon (C–C) composites are ideal for use as aerospace vehicle structural materials; however, they lack high‐temperature oxidation resistance requiring environmental barrier coatings for application. Ultra high‐temperature ceramics (UHTCs) form oxides that inhibit oxygen diffusion at high temperature are candidate thermal protection system materials at temperatures >1600°C. Oxidation protection for C–C composites can be achieved by duplicating the self‐generating oxide chemistry of bulk UHTCs formed by a “composite effect” upon oxidation of ZrB2–SiC composite fillers. Dynamic Nonequilibrium Thermogravimetric Analysis (DNE‐TGA) is used to evaluate oxidation in situ mass changes, isothermally at 1600°C. Pure SiC‐based fillers are ineffective at protecting C–C from oxidation, whereas ZrB2–SiC filled C–C composites retain up to 90% initial mass. B2O3 in SiO2 scale reduces initial viscosity of self‐generating coating, allowing oxide layer to spread across C–C surface, forming a protective oxide layer. Formation of a ZrO2–SiO2 glass‐ceramic coating on C–C composite is believed to be responsible for enhanced oxidation protection. The glass‐ceramic coating compares to bulk monolithic ZrB2–SiC ceramic oxide scale formed during DNE‐TGA where a comparable glass‐ceramic chemistry and surface layer forms, limiting oxygen diffusion. 相似文献
11.
《Journal of the European Ceramic Society》2003,23(6):961-976
This paper describes a preliminary investigation of a nanocomposite ceramic coating system, based on Al2O3/SiC. Feedstock Al2O3/SiC nanocomposite powder has been manufactured using sol-gel and conventional freeze-drying processing techniques and then low pressure plasma sprayed onto stainless steel substrates using a CoNiCrAlY bond coat. Coatings of a commercial Al2O3 powder have also been manufactured as a reference for phase transformations and microstructure. The different powder morphology and size distribution resulting from the different processing techniques and their effect on coating microstructure has been investigated. Phase analysis of the feedstock powders and of the as-sprayed coatings by X-ray diffractometry (XRD) and nuclear magnetic resonance (NMR) showed that the nano-scale SiC particles were retained in the composite coatings and that equilibrium α-Al2O3 transformed to metastable γ- and δ-Al2O3 phases during plasma spraying. Other minority phases in the sol-gel Al2O3/SiC nanocomposite powder such as silica and aluminosilicate were removed by the plasma-spraying process. Microstructure characterisation by scanning electron microscopy (SEM) of the as-sprayed surface, polished cross-section, and fracture surface of the coatings showed evidence of partially molten and unmolten particles incorporated into the predominantly lamella microstructure of the coating. The extent of feedstock particle melting and consequently the character of the coating microstructure were different in each coating because of the effects of particle morphology and particle size distribution on particle melting in the plasma. 相似文献
12.
Eugenio Garcia Andres Nistal María Isabel Osendi Pilar Miranzo 《Journal of the American Ceramic Society》2016,99(12):4066-4072
Glass compositions in the Y2O3–Al2O3–SiO2 (YAS) system are envisaged as promising coatings for high‐temperature protection, in particular for the thermal protection systems (TPS) looked for aerospace applications. Recently, thermally sprayed YAS hybrid coatings containing a small amount of graphene nanoplateletes (GNPs) showed enhanced performance as compared to the blank YAS coating, demonstrated by the occurrence of unusual electrical conductivity for these glasses and the development of better mechanical compliance, both phenomena associated with the presence of GNPs. Nevertheless, a crucial issue is to demonstrate if these kinds of coatings would also have superior behavior under ablation conditions, particularly regarding the mentioned TPS applications. This work goes far beyond, exploring the ablative behavior of new YAS/GNPs coatings flame sprayed over SiC substrates. These essential tests were carried out under laboratory conditions, reaching limit temperatures of 1350°C while blowing gas. Results evidence that hybrid coatings having just 1.05 vol% GNPs show enhanced ablation resistance, actually withstanding up to 30 thermal cycles (between 200°C and 1350°C) without apparent damage. This satisfactory performance is linked to the benefits of the GNP additions, and fundamentally to the higher emissivity and the directional thermal conduction characteristics of the hybrid coatings—produced by the formation of a GNP network with a preferential surface parallel arrangement—that preclude the creation of hot spots and also hinder heat propagation toward the substrate; accordingly, coating degradation is constrained to the uppermost layer of these coatings. 相似文献
13.
《Ceramics International》2022,48(2):1699-1714
In this research, the effect of the ZrB2 middle layer and SiC Weight percentage on the erosion behavior of SiC/ZrB2– SiC/ZrB2 functionally gradient coating were investigated. For this purpose, SiC gradient coating was prepared via the reactive melt infiltration method (RMI). Afterwards ZrB2–SiC layers containing 10, 20 and 30 wt% SiC and, ZrB2 as the outer layer were applied on SiC coated graphite via solid shielding shrouded plasma spraying (SSPS). To investigate the erosion resistance of the coating, the specimens were subjected to oxy-acetylene and propane flame. The results showed that by applying the ZrB2–SiC layer between SiC and ZrB2 coating, due to the gradual change of the coefficient of thermal expansion mismatch and reduction of thermal stresses, erosion resistance improves, so that the coating with 20 wt% SiC with mass and linear erosion rate, ?0.072 × 10?4 g.cm?2.s?1, 0.0166 μm s?1 respectively had the best erosion resistance under oxy propane flame.In the oxyacetylene flame test, a similar result was obtained to the oxy propane test and the SiC/ZrB2-20% wt. SiC/ZrB2 coating had the lowest erosion rate. 相似文献
14.
Angel A. Peña Jonathan P. Vernon Rodney W. Trice 《Journal of the American Ceramic Society》2019,102(9):5645-5655
In this paper, how rare-earth element dopants (samarium and erbium) affect the scale development of sintered ZrB2/SiC (ZBS) samples during ablation testing was investigated. ZBS billets with five different Sm to Er ratios, with a nominal total amount of 3 mol% dopant incorporated, were prepared by sintering in vacuum to 2000°C and subjected to 60 and 300 seconds ablation cycles. Differences in surface temperatures between ZBS samples with different dopant ratios suggests differences in spectral absorptance/emittance between each of the five compositions investigated. ZBS billets co-doped with Sm and Er form a beneficial c1-(Sm/Er)0.2Zr0.8O1.9 oxide scale as the majority phase, with some glassy phase observed. The crystalline c1-(Sm/Er)0.2Zr0.8O1.9 oxide scale is more thermally stable than the m-ZrO2 oxide scale typically formed in oxidized ZBS systems, resulting in a more adherent oxide scale to the unreacted material. The crystalline oxide scale and the amorphous phase are formed by a convection cell mechanism where the c1-(Sm/Er)0.2Zr0.8O1.9 crystalline islands precipitate, grow, and coalesce. 相似文献
15.
High temperature anti‐oxidation behavior of in situ and ex situ nanostructured C/SiC/ZrB2‐SiC gradient coatings: Thermodynamical evolution,microstructural characterization,and residual stress analysis
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Alireza Abdollahi Zia Valefi Naser Ehsani Shahla Torabi 《International Journal of Applied Ceramic Technology》2018,15(6):1319-1333
Nanostructured C/SiC/ZrB2–SiC oxidation protective gradient coating was prepared by a two‐step reactive melt infiltration method. In order to reduce production cost, ZrB2 phase was synthesized by the in situ reactive that included low‐cost ZrO2 and B2O3 powders as raw materials. High‐temperature oxidation behavior of coatings was evaluated by isothermal oxidation test at 1773 K in air for 10 hours. Thermodynamical behavior of the coatings at various temperatures during oxidation test and coating process was predicted by HSC Chemistry 6.0 software. Compressive residual stresses of 36.9 MPa and 41 MPa were calculated for in situ and ex situ coatings by Williamson‐Hall method. After 10 hours of isothermal oxidation at 1773K, in situ and ex situ coatings showed 12.84% and 15.69% of weight losses with oxidation rates of 1.87 × 10?2 g cm?3 h?1 and 0.91 × 10?2 g cm?3 h?1, respectively. These results indicated that the oxidation protection ability of the coating produced by the in situ method was very close to ex situ coating. 相似文献
16.
Shuko Akamine Toshio Ogasawara Chiharu Ogawa Takuya Aoki 《Journal of the American Ceramic Society》2022,105(8):5347-5358
Porous MgAl2O4 ceramics designated as THERMOSCATTTM have diffuse reflectance based on the Mie theory. The reflectance greatly suppresses radiation heat transfer and has low emissivity at 1–5 μm wavelengths. Their thermal conductivity has been measured as less than 0.3 W/(m K) at 1500°C. Furthermore, porous MgAl2O4 ceramics have near-zero hemispherical spectral emissivity values at 0.35–5 μm wavelengths. High heat resistance and low emissivity materials in the atmosphere are useful for the innermost layer of industrial furnaces to confine energy efficiently. Additionally, this material is useful as a radiation reflectors, such as in stand-off thermal protection systems. This study elucidated the suppression of radiation transfer in porous MgAl2O4 ceramics attributable to low thermal emissivity. Therefore, the thermal insulation performance under radiation heating in vacuum, the emissivity validity evaluation of low-emissivity porous materials using finite element analysis, and microstructure effects on radiation heating performance and mechanical properties were investigated. 相似文献
17.
Anneliese E. Brenner Angel A. Peña Xin Li Phuah Christopher Petorak Brian Thompson Rodney W. Trice 《Journal of the European Ceramic Society》2018,38(4):1136-1142
Samarium-doped ZrB2/SiC (ZBS) coatings possess properties of high emissivity and excellent ablation performance suitable for hypersonic applications. Of interest in the current study is how cyclic ablation affects the scale development on alumina substrates. ZBS coatings with 3, 5 and 8 mol% of samarium (Sm) dopant were prepared via shrouded plasma spray onto alumina substrates and subjected to two 60-s ablation cycles with temperatures reaching up to 1700 °C. Blisters were observed on the Sm-doped coatings after the 1st cycle as a result of a local eutectic reaction between the ablation products and alumina substrate. A Sm-stabilized t-ZrO2 phase was identified through X-ray diffraction after the ablation of the Sm-doped coatings. The ZBS with 5 mol% of Sm dopant produced a flower-like microstructure after the 2nd cycle due to the formation of convection cells. 相似文献
18.
Chenxu Liu Shuguang Zhang Ruonan Ji Peng Wang Jin Zhang Yu Tian Yonggang Meng Yedong He 《Ceramics International》2019,45(4):4747-4755
Semiconductor particles doped Al2O3 coatings were prepared by cathode plasma electrolytic deposition in Al(NO3)3 electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings. 相似文献
19.
To improve the oxidation protective ability of carbon/carbon composites, ZrB2–SiC gradient coating was prepared on the surface of C/C composites by an in-situ reaction method. The ZrB2–SiC gradient coating consisted of an inner ZrB2–SiC layer and an outer ZrB2–SiC–Si coating. The phase composition and microstructures of the multiphase coating were characterized by XRD, EDS and SEM. Results showed that the inner coating is mainly composed of ZrB2 and SiC, while the outer multiphase coating is composed of ZrB2, SiC and Si. The multilayer coating is about 200 μm in thickness, which has no penetration crack or big hole. The oxidation behavior of the coated C/C composites at 1773 K in air was investigated. Results show that the gradient ZrB2–SiC oxidation protective coating could protect C/C from oxidation for 207 h with only (4.56±1.2)×10−3 g/cm2 weight loss, owing to the compound silicate glass layer with the existence of thermally stable phase ZrSiO4. 相似文献
20.
《Ceramics International》2016,42(8):9511-9518
A double-layers ZrB2-based ceramic coatings containing ZrB2, MoSi2, SiCw and borosilicate glass were prepared on lightweight and porous ZrB2-modified carbon–bonded carbon fiber composites (CBCFs/ZrB2) by a trace oxygen sintered technology. The high-temperature erosion resistance of the coated CBCFs/ZrB2 was investigated under simulated atmospheric re-entry conditions by a high frequency plasma wind tunnel test with a heat fluxes of 1.3 MW/m and stagnation pressure of 1.2kPa. The results showed that the coated composites exhibited excellent ablation resistance for 800 s and the different positions of coating exhibit different response temperatures and microstructures. After ablation, the micrographs of marginal position show more compact than central position at sample surface. In addition, the side of the samples exhibits crack region, B2O3 precipitates region and virgin coating region. 相似文献