共查询到20条相似文献,搜索用时 15 毫秒
1.
Xingye Guo Li Li Hyeon-Myeong Park James Knapp Yeon-Gil Jung Jing Zhang 《Journal of Thermal Spray Technology》2018,27(4):581-590
Lanthanum zirconate (La2Zr2O7) has been proposed as a promising thermal barrier coating (TBC) material due to its low thermal conductivity and high stability at high temperatures. In this work, both single and double-ceramic-layer (DCL) TBC systems of La2Zr2O7 and 8 wt.% yttria-stabilized zirconia (8YSZ) were prepared using air plasma spray (APS) technique. The thermomechanical properties and microstructure were investigated. Thermal gradient mechanical fatigue (TGMF) tests were applied to investigate the thermal cycling performance. The results showed that DCL La2Zr2O7 + 8YSZ TBC samples lasted fewer cycles compared with single-layered 8YSZ TBC samples in TGMF tests. This is because DCL La2Zr2O7 TBC samples had higher residual stress during the thermal cycling process, and their fracture toughness was lower than that of 8YSZ. Bond strength test results showed that 8YSZ TBC samples had higher bond strength compared with La2Zr2O7. The erosion rate of La2Zr2O7 TBC samples was higher than that of 8YSZ samples, due to the lower critical erodent velocity and fracture toughness of La2Zr2O7. DCL porous 8YSZ + La2Zr2O7 had a lower erosion rate than other SCL and DCL La2Zr2O7 coatings, suggesting that porous 8YSZ serves as a stress-relief buffer layer. 相似文献
2.
Zhenhua Xu Shimei HeLimin He Rende MuGuanghong Huang Xueqiang Cao 《Journal of Alloys and Compounds》2011,509(11):4273-4283
Double-ceramic-layer (DCL) thermal barrier coatings (TBCs) of La2(Zr0.7Ce0.3)2O7 (LZ7C3) and yttria stabilized zirconia (YSZ) were deposited by electron beam-physical vapor deposition (EB-PVD). The thermal cycling test at 1373 K in an air furnace indicates the DCL coating has a much longer lifetime than the single layer LZ7C3 coating, and even longer than that of the single layer YSZ coating. The superior sintering-resistance of LZ7C3 coating, the similar thermal expansion behaviors of YSZ interlayer with LZ7C3 coating and thermally grown oxide (TGO) layer, and the unique growth modes of columns within DCL coating are all very helpful to the prolongation of thermal cycling life of DCL coating. The failure of DCL coating is mainly a result of the reduction-oxidation of cerium oxide, the crack initiation, propagation and extension, the abnormal oxidation of bond coat, the degradation of t′-phase in YSZ coating and the outward diffusion of Cr alloying element into LZ7C3 coating. 相似文献
3.
D. Lozano-Mandujano C. A. Poblano-Salas H. Ruiz-Luna B. Esparza-Esparza A. L. Giraldo-Betancur J. M. Alvarado-Orozco L. G. Trápaga-Martínez J. Muñoz-Saldaña 《Journal of Thermal Spray Technology》2017,26(6):1198-1206
This paper deals with the deposition of La2Zr2O7 (LZO) and LaAlO3 (LAO) mixtures by air plasma spray (APS). The raw material for thermal spray, single phase LZO and LAO in a 70:30 mol.% ratio mixture was prepared from commercial metallic oxides by high-energy ball milling (HEBM) and high-temperature solid-state reaction. The HEBM synthesis route, followed by a spray-drying process, successfully produced spherical agglomerates with adequate size distribution and powder-flow properties for feeding an APS system. The as-sprayed coating consisted mainly of a crystalline LZO matrix and partially crystalline LAO, which resulted from the high cooling rate experienced by the molten particles as they impact the substrate. The coatings were annealed at 1100 °C to promote recrystallization of the LAO phase. The reduced elastic modulus and hardness, measured by nanoindentation, increased from 124.1 to 174.7 GPa and from 11.3 to 14.4 GPa, respectively, after the annealing treatment. These values are higher than those reported for YSZ coatings; however, the fracture toughness (K IC) of the annealed coating was only 1.04 MPa m0.5. 相似文献
4.
Zhenbang Wei Yong Jiang Limeng Liu Laner Wu Zhenkun Huang 《Journal of Phase Equilibria and Diffusion》2016,37(2):149-154
Phase formation sequence of the yttrium aluminates in the Y2O3-Al2O3-SiC ternary system as temperature increases were investigated via x-ray diffraction (XRD). Results showed that YAM (monoclinic), YAP (perovskite) and YAG (garnet) were the yttrium aluminates presented in the solid-state reacted samples at a fixed Al2O3:SiC ratio of 1:1. Formation of the yttrium aluminates depended on the temperature. The YAM, YAP and YAG started to form below 1150 °C, at 1300 °C, and at 1450 °C, respectively. Accordingly, two behavior phase diagrams of the Y2O3-Al2O3-SiC ternary system were recognized, one is in the temperature range of 1150-1300 °C and the other is in 1300-1450 °C, respectively. Thereafter, the phase equilibrium was reached in the temperature range of 1450-1700 °C. Effects of SiC on the phase formation processes in the ternary system were discussed. 相似文献
5.
In this study, three groups of thermal barrier coatings (TBCs) samples were remelted by CO2 laser with different laser energy densities (1, 5 and 10 J/mm2) to seal the surface of yttria-stabilized zirconia (YSZ) coatings. Microscopic observations showed that the cracks size and the remelted depth in YSZ coatings increased. A ~ 50-μm-thick dense layer was formed on the surface of YSZ coating in samples with 1 J/mm2 energy density. Microindentation tests showed that the Vickers hardness of YSZ coatings increases with the increase in laser energy density. After isothermal oxidation at 1200 °C for 200 h, thinner thermally growth oxides were found in laser remelted YSZ samples under energy density of 1 J/mm2 (6.32 ± 0.28 μm). Cyclic oxidation results showed that the weight gain per unit area of low energy density laser remelted TBCs was smaller than that of the high energy density laser remelted and as-sprayed TBCs. 相似文献
6.
Junfeng Gou Jian Zhang Qiwen Zhang You Wang Chaohui Wang 《Journal of Thermal Spray Technology》2017,26(4):764-777
In this paper, the effect of nano-Si3N4 additives and plasma treatment on the wear behavior of Al2O3-8YSZ ceramic coatings was studied. Nano-Al2O3, nano-8YSZ (8 wt.% Y2O3-stabilized ZrO2) and nano-Si3N4 powders were used as raw materials to fabricate four types of sprayable feedstocks. Plasma treatment was used to improve the properties of the feedstocks. The surface morphologies of the ceramic coatings were observed. The mechanical properties of the ceramic coatings were measured. The dry sliding wear behavior of the Al2O3-8YSZ coatings with and without Si3N4 additives was studied. Nano-Si3N4 additives and plasma treatment can improve the morphologies of the coatings by prohibiting the initiation of micro-cracks and reducing the unmelted particles. The hardness and bonding strength of AZSP (Al2O3-18 wt.% 8YSZ-10 wt.% Si3N4-plasma treatment) coating increased by 79.2 and 44% compared to those of AZ (Al2O3-20 wt.% 8YSZ) coating. The porosity of AZSP coating decreased by 85.4% compared to that of AZ coating. The wear test results showed that the addition of nano-Si3N4 and plasma treatment could improve the wear resistance of Al2O3-8YSZ coatings. 相似文献
7.
Li1.3Al0.3Ti1.7(PO4)3-coated LiMn2O4 was prepared by wet chemical route. The phase, surface morphology, and electrochemical properties of the prepared powders
were characterized by X-ray diffraction, scanning electron micrograph, and galvanostatic charge-discharge experiments. Li1.3Al0.3Ti1.7(PO4)3-coated LiMn2O4 has similar X-ray diffraction patterns as LiMn2O4. The corner and border of Li1.3Al0.3Ti1.7(PO4)3-coated LiMn2O4 particles are not as clear as the uncoated one. The two powders show similar values of lithium-ion diffusion coefficient.
When cycled at room temperature and 55°C for 40 times at the charge-discharge rate of 0.2C, Li1.3Al0.3Ti1.7(PO4)3-coated LiMn2O4 shows the capacity retentions of 98.2% and 93.9%, respectively, which are considerably higher than the values of 85.4% and
79.1% for the uncoated one. Both the capacity retention differences between Li1.3Al0.3Ti1.7(PO4)3-coated LiMn2O4 and LiMn2O4 cycling at room temperature and 55°C become larger with the increase of charge-discharge rate. When the charge-discharge
rate reaches 2C, the capacity retention of LATP-coated LiMn2O4 becomes 8.4% higher than the uncoated LiMn2O4 for room temperature cycling, and it becomes 11.1% higher than the latter when cycled at 55°C. 相似文献
8.
H. S. Nithin Vijay Desai M. R. Ramesh 《Journal of Materials Engineering and Performance》2017,26(11):5251-5261
In this paper, investigation into solid particle erosion behavior of atmospheric plasma-sprayed composite coating of CoCrAlY reinforced with Al2O3 and CeO2 oxides on Superni 76 at elevated temperature of 600 °C is presented. Alumina particles are used as erodent at two impact angles of 30° and 90°. The microstructure, porosity, hardness, toughness and adhesion properties of the as-sprayed coatings are studied. The effects of temperature and phase transformation in the coatings during erosion process are analyzed using XRD and EDS techniques. Optical profilometer is used for accurate elucidation of erosion volume loss. CoCrAlY/CeO2 coating showed better erosion resistance with a volume loss of about 50% of what was observed in case of CoCrAlY/Al2O3/YSZ coating. Lower erosion loss is observed at 90° as compared to 30° impact angle. The erosion mechanism evaluated using SEM micrograph revealed that the coatings experienced ductile fracture exhibiting severe deformation with unusual oxide cracks. Reinforced metal oxides provide shielding effect for erodent impact, enabling better erosion resistance. The oxidation of the coating due to high-temperature exposure reforms erosion process into oxidation-modified erosion process. 相似文献
9.
ZHANG Hongsong SUN Kun XU Qiang WANG Fuchi LIU Ling WEI Yuan CHEN Xiaoge 《稀有金属(英文版)》2009,28(3):226-230
Sm2(Zr1−x
Ce
x
)2O7 (x = 0.1, 0.2, and 0.3) ceramics were prepared by solid reaction method at 1600°C for 10 h using Sm2O3, ZrO2, and CeO2 as starting reactants. The phase compositions, microstructures, thermal expansion coefficients, and partial thermal conductivities
of these materials were investigated. X-ray diffraction (XRD) results reveal that Sm2(Zr0.9Ce0.1)2O7 with pyrochlore structure and Sm2(Zr1−x
Ce
x
)2O7 (x = 0.2 and 0.3) with fluorite structure were synthesized, and scanning electrical microscopy (SEM) images show that the microstructures
of these products are very dense. The linear thermal expansion coefficients increase with increasing temperature in the temperature
range from ambient to 1200°C, and the thermal expansion coefficients increase with increasing content of doped CeO2. The thermal conductivities of Sm2(Zr0.8Ce0.2)2O7 and Sm2(Zr0.7Ce0.3)2O7 decrease gradually with an increase in temperature. These results show that the synthesized ceramic materials can be explored
as novel prospective candidate materials for use in new thermal barrier coating systems in the future. 相似文献
10.
Jiajun You Xia Chen Bingbing Zheng Xin Geng Chao Zhang 《Journal of Thermal Spray Technology》2017,26(4):728-734
Zinc ferrite (ZnFe2O4) sensitive coatings have been deposited by suspension plasma spraying. The phase constitution of the coatings was characterized by x-ray diffraction while the top surface and cross-sectional morphology of the coatings were inspected by scanning electron microscopy. The response to acetone was tested with the concentration in the range of 25-500 ppm at the working temperature from 175 to 275 °C. The sensors that were deposited at an arc current of 400 A showed better performance than those at 600 A owing to small grain size and high porosity. The sensor response increased with acetone concentration. The optimized sensors showed excellent response/recovery time and selectivity to acetone at 200 °C. 相似文献
11.
V. S. Rudnev T. P. Yarovaya P. M. Nedozorov A. Yu. Ustinov L. M. Tyrina I. V. Malyshev V. G. Kuryavyi V. S. Egorkin S. L. Sinebryukhov S. V. Gnedenkov 《Protection of Metals and Physical Chemistry of Surfaces》2011,47(5):621-628
Regularities of the effect produced by Ce2(SO4)3 salt introduced in an aqueous electrolyte containing Zr(SO4)2 on the plasma-electrolytic formation of oxide coatings on titanium, their composition, and structure are studied. ZrO2 + CeO
x
+ TiO2 three-phase oxide coatings with a thickness about 10 μm are obtained. The coatings involve ZrO2 cubic phase. The ZrO2-to-TiO2 phase ratio in the coatings can be controlled. The zirconium content in the coatings reaches 20 at %, while that of cerium
is 3–5 at %. The surface layer (∼3-nm thick) contains Ce3+ (∼30%) and Ce4+ (∼70%). Pores in the surface part of coatings have diameters around or smaller than 1 μm and are regularly arranged. The
obtained systems have a certain catalytic activity with respect to the oxidation of CO to CO2 at temperatures above 400–450°C. The coatings are corrosion-resistant in chloride-containing environments. The thickness
h of coatings depending on the charge Q supplied to the cell is described by the equation h = h
0(Q/Q
0)
n
, where n = 0.35 and h
0 is the thickness of the coating formed at Q
0 = 1 C/cm2. 相似文献
12.
This paper investigates the high-temperature oxidation of cermet coatings composed of two types of nanosized particles (WC and a mixture of WC and Al2O3) incorporated in nickel and produced by co-electrodeposition. For this purpose, high-temperature oxidation tests were conducted at three temperatures (500, 600, and 700 °C) in dry air with 6 time intervals up to 96 h and mass changes at each specific time interval was measured. Statistical techniques were used to calculate the oxidation rate constants (k) and growth-rate time constants (a) for all coatings. The confidence intervals associated with tests were also calculated. The results showed linear to sub-parabolic oxidation rates for coatings composed of only WC particles and sub-liner to liner oxidation rates for coating with both WC and Al2O3 particles. The reduction in oxidation rates for coatings with both WC and Al2O3 particles were correlated to the addition of Al2O3 particles in the matrix. 相似文献
13.
Xin Zhong Yaran Niu Liping Huang Hong Li Xuebin Zheng Chuanxian Ding Jinliang Sun 《Journal of Thermal Spray Technology》2017,26(1-2):203-210
In the present work, Yb2Si2O7 powder was synthesized by solid-state reaction using Yb2O3 and SiO2 powders as starting materials. Atmospheric plasma spray technique was applied to fabricate Yb2Si2O7 coating. The phase composition and microstructure of the coating were characterized. The density, open porosity and Vickers hardness of the coating were investigated. Its thermal stability was evaluated by thermogravimetry and differential thermal analysis (TG-DTA). The thermal diffusivity and thermal conductivity of the coating were measured. The results showed that the as-sprayed coating was mainly composed of crystalline Yb2Si2O7 with amorphous phase. The coating had a dense structure containing defects, such as pores, interfaces and microcracks. The TG-DTA results showed that there was almost no mass change from room temperature to 1200 °C, while a sharp exothermic peak appeared at around 1038 °C in DTA curve, which indicated that the amorphous phase crystallized. The thermal conductivity of the coating decreased with rise in temperature up to 600 °C and then followed by an increase at higher temperatures. The minimum value of the thermal conductivity of the Yb2Si2O7 coating was about 0.68 W/(m K). 相似文献
14.
Zirconia (ZrO2) ceramics are being considered as a candidate material for thermal insulating barriers in pressure tubes used in the supercritical water (SCW) nuclear reactors. However, the literature suggests that zirconia may undergo a detrimental phase transformation which is accelerated in aqueous environments. In this research, 8 mol% Yttria-Stabilized Zirconia (YSZ) ceramics with the addition of 5 and 10 mol% Nd2O3 were manufactured via spark plasma sintering (SPS) process and subsequently subjected to a SCW environment. The weight losses and microstructural evolutions of these materials during SCW exposure were studied. The results suggest that doping YSZ with Nd2O3 significantly decreased the degradation rate of the YSZ ceramic and improved its structural stability. X-ray diffraction studies revealed that after degradation testing, the Nd2O3 helped to retain the desirable cubic phase of YSZ matrix. In the case of pure YSZ ceramic, a phase change of the matrix toward the monoclinic lattice was observed and likely contributed to the ceramic’s disintegration in SCW environment. 相似文献
15.
Ahmed Mohamed Ahmed Abd El-Moez Ahmed Mohamed Medhat Abdelrady Abdellateef Hassan Ahmed Abd El-Ghanny 《稀有金属(英文版)》2016,35(7):551-558
La0.7Sr0.3Mn1?x Ni x O3 (x = 0, 0.025, 0.050 and 0.075) ceramics were prepared by the conventional solid-state reaction method. The partial substitution of Mn by Ni2+ leads to a decrease in cell volume as well as a structural transition from the rhombohedral to the orthorhombic structure. Ni2+ doping increases the electrical resistivity, decreases the semiconductor–metal transition temperature (T ms) and relatively enhances the room temperature magnetoresistance (MR), especially in x = 0.025 and around T ms. With respect to conduction mechanism, the small polaron hopping (SPH) and the variable range hopping (VRH) models were used to examine conduction in the semiconducting region. 相似文献
16.
Xuemei Song Ziwei Liu Mingguang Kong Yongzhe Wang Liping Huang Xuebin Zheng Yi Zeng 《Journal of Thermal Spray Technology》2016,25(4):770-777
The microstructures of three atmospheric plasma-sprayed (APS) Al2O3-ZrO2 coatings were investigated using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The differences in the microstructures of the three Al2O3-ZrO2 coatings, including their phase compositions, cracks, pores, grain sizes, and solid solutions, were analyzed in detail. A close relationship was observed between the thermal conductivities of the coatings and the microstructures, and the Al2O3-YSZ coatings with more spherical pores, fewer vertical cracks, and finer grains exhibited the lowest thermal conductivity of 0.91 W/m·K. Compared with YSZ coatings, Al2O3-YSZ coatings can exhibit lower thermal conductivity, which may be attributed to the formation of an amorphous phase, smaller grains, and Al2O3-YSZ solid solution. 相似文献
17.
Lutz-Michael Berger Kerstin Sempf Yoo Jung Sohn Robert Vaßen 《Journal of Thermal Spray Technology》2018,27(4):654-666
The formation and decomposition of aluminum titanate (Al2TiO5, tialite) in feedstock powders and coatings of the binary Al2O3-TiO2 system are so far poorly understood. A commercial fused and crushed Al2O3-40%TiO2 powder was selected as the feedstock for the experimental series presented in this paper, as the composition is close to that of Al2TiO5. Part of that powder was heat-treated in air at 1150 and 1500 °C in order to modify the phase composition, while not influencing the particle size distribution and processability. The powders were analyzed by thermal analysis, XRD and FESEM including EDS of metallographically prepared cross sections. Only a maximum content of about 45 wt.% Al2TiO5 was possible to obtain with the heat treatment at 1500 °C due to inhomogeneous distribution of Al and Ti in the original powder. Coatings were prepared by plasma spraying using a TriplexPro-210 (Oerlikon Metco) with Ar-H2 and Ar-He plasma gas mixtures at plasma power levels of 41 and 48 kW. Coatings were studied by XRD, SEM including EDS linescans of metallographically prepared cross sections, and microhardness HV1. With the exception of the powder heat-treated at 1500 °C an Al2TiO5-Ti3O5 (tialite–anosovite) solid solution Al2?xTi1+xO5 instead of Al2TiO5 existed in the initial powder and the coatings. 相似文献
18.
Hong-song Zhang Kun Sun Qiang Xu Fu-chi Wang Ling Liu 《Journal of Materials Engineering and Performance》2009,18(8):1140-1143
A pure Sm2(Zr0.6Ce0.4)2O7 ceramic was prepared via solid-state reaction using ZrO2, CeO2, and Sm2O3 as the starting powders at 1600 °C for 10 h. The phase composition and microstructure were studied by X-ray diffraction (XRD),
Fourier-transform infrared spectrometer (FT-IR), and scanning electron microscope (SEM). The thermal conductivity was measured
by laser-flash method. The results indicated that the prepared ceramic had a pure fluorite structure. Its microstructure was
dense with a relative density of 93.35% and there were no other unreacted oxides or interphases in the interfaces between
grains. Because of the structure transformation from pyrochlore to fluorite, the synthesized product had a higher thermal
conductivity than Sm2Zr2O7 ceramic. However, the average thermal conductivity of Sm2(Zr0.6Ce0.3)2O7 was lower than that of yttria-stabilized zirconia. The measurements of thermal conductivity suggested that the synthesized
ceramic can be used as a new material for new thermal barrier coatings in the future. 相似文献
19.
S. Mantry A. Mandal D. K. Mishra B. B. Jha B. K. Mishra M. Chakraborty 《Journal of Thermal Spray Technology》2014,23(7):1073-1080
Nanostructured La2Ce2O7-doped YSZ coatings were developed using atmospheric plasma-spraying technique by optimizing various process parameters. To ensure the retention of nanostructure, the molten state of nanoagglomerates was monitored using plasma and particle diagnostic tools. It was observed that the morphology of the coating exhibits a bimodal microstructure consisting of nanozones reinforced in a matrix of fully-molten particles. The thermal diffusivity of nano-LaCeYSZ coatings is lower than that of nano and bulk YSZ. The reason for this change in thermal diffusivity may be attributed to scattering of phonons at grain boundaries, point defect scattering and higher inter-splat porosity. Also, the thermal conductivity of the nanocomposite coatings was lower than those of nanostructured and bulk YSZ coatings. XRD results show cubic zirconia with a small amount of tetragonal zirconia. The average grain size of the as-sprayed La2Ce2O7-YSZ nanocomposite coatings is ~150-200 nm. The improved thermal behavior is mainly due to a dense, packed, and more compact structure of the coatings. 相似文献
20.
Xiangwei Wu Hong Luo Meng Sheng Huanchao Liu Zhen Xiao Haoran Geng 《JOM Journal of the Minerals, Metals and Materials Society》2017,69(2):184-190
In this article, the effects of lanthanum oxide (La2O3) on the microstructure and mechanical properties of H62 brass were investigated by using the universal testing machine, Brinell hardness tester, optical microscope, and scanning electron microscope (SEM). Immersion corrosion and electrochemical measurements were carried out to identify the influence of La2O3 on the corrosion behavior of the H62 brass. The phase constitution, microstructure, and phase composition of the H62 brass were analyzed by x-ray diffraction, SEM, and energy-dispersive spectrometer, respectively. The results show that the microstructure of α phase changes from dendrite grains to equiaxed grains, and the content and distribution of β phase are improved significantly. When the La2O3 content reaches 0.8 wt.%, the H62 brass obtains favorable comprehensive mechanical properties and the strength and hardness decrease but elongation increases, which is conducive to plastic processing. In addition, under the optimum amount of 0.8 wt.% La2O3 content, the corrosion rate of immersion corrosion attains the minimum values: As 12.6 g m?2 h?1, it decreases by 24%; as the corrosion potential changes from ?1.1327 V to ?0.328 V, it increases by 70.9%; and as the corrosion current density decreases from ?2.833 mA mm?2 to ?3.28 mA mm?2 corrosion, it decreases by 15.78%, when compared with H62 brass. 相似文献