共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
Qiong Wu Xiaojuan Ji Haoran Peng Xianjing Ren Yueguang Yu 《Journal of Thermal Spray Technology》2016,25(4):757-762
Ce-modified La2Zr2O7 powders, i.e., La2Zr2O7 (LZ), La2(Zr0.7Ce0.3)2O7 (LZ7C3), and La2(Zr0.3Ce0.7)2O7 (LZ3C7), were used to produce thermal barrier coatings by atmospheric plasma spray process. The chemical compatibility of the CeO2-doped La2Zr2O7 with the traditional YSZ was investigated in LZ-YSZ powder mixtures and LZ-YSZ bilayer coatings by x-ray diffraction and scanning electron microscope. The powder mixtures and coatings were aged at 1200 and 1300 °C for 100 h. The results showed that LZ and LZ7C3 presented single pyrochlore structure after the heat treatments at both 1200 and 1300 °C. For LZ3C7, however, fluorite structure was observed at 1300 °C, indicating a poor phase stability of LZ3C7 at the elevated temperature. The results further showed that La2(Zr0.3Ce0.7)2O7 reacted with YSZ in the bilayer ceramic coatings due to the diffusion of cerium, zirconium, and yttrium. While for La2Zr2O7(LZ) and La2(Zr0.7Ce0.3)2O7, a better chemical compatibility with YSZ was shown. 相似文献
3.
Recently, extensive efforts have been made to develop new thermal barrier coating (TBC) materials which can operate at temperatures
above 1523 K over a long term. In this article, LaTi2Al9O19 (LTA) was synthesized by solid-state reaction at 1773 K, and the mechanical properties of the LTA bulk were evaluated. The
microhardness is about 14 GPa, comparable to that of YSZ bulk, whereas the Young’s modulus is about 44 GPa, lower than the
value of YSZ. However, the fracture toughness of 0.8-1 MPa m1/2 is much lower than that of bulk YSZ. A double-ceramic-layer LTA/YSZ TBC structure was proposed and the TBC sprayed by plasma
spraying. Thermal cycling tests of the TBC specimens were performed at 1373 K with a dwell time of 10 min. The LTA remained
good stability with ZrO2 and Al2O3. However, the single layer LTA TBC was cracked at the LTA/bond coat interface after about 300 cycles, due to its poor thermal
shock resistance, while the YSZ TBC yielded a lifetime of about 1000 cycles. The LTA/YSZ TBC remained intact even after 3000
cycles, exhibiting a promising potential as new TBC materials. 相似文献
4.
Émilien Darthout Guillaume Laduye François Gitzhofer 《Journal of Thermal Spray Technology》2016,25(7):1264-1279
The solution precursor plasma spray process, in which a solution of metal salts is axially injected into an induction thermal plasma, is suitable for deposition of nanostructured environmental barrier coatings. The effects of main processing parameters, namely the solution precursor concentration, spraying distance, reactor pressure, and atomization gas flow rate, have been analyzed using D-optimal design of experiments regarding the deposition rate and coating porosity responses. Among these four parameters, the solution precursor concentration had the greatest influent on the coating structure, followed by the spraying distance and reactor pressure, and finally the atomization gas flow rate with a small contribution. It is pointed out that the species that impact on the substrate are agglomerates of nanoparticles. The equivalent thermal conductivity of selected coatings was computed from experimental temperature evolution curves obtained by laser flash thermal diffusivity analysis, using two methods: a multilayer finite-element model with optimization, and a multilayer thermal diffusion model. The results of the two models agree, with coatings exhibiting low thermal conductivity between 0.7 and 1 W/(m K) at 800 °C. 相似文献
5.
Emine Bakan Diana Marcano Dapeng Zhou Yoo Jung Sohn Georg Mauer Robert Vaßen 《Journal of Thermal Spray Technology》2017,26(6):1011-1024
Dense, crack-free, uniform, and well-adhered environmental barrier coatings (EBCs) are required to enhance the environmental durability of silicon (Si)-based ceramic matrix composites in high pressure, high gas velocity combustion atmospheres. This paper represents an assessment of different thermal spray techniques for the deposition of Yb2Si2O7 EBCs. The Yb2Si2O7 coatings were deposited by means of atmospheric plasma spraying (APS), high-velocity oxygen fuel spraying (HVOF), suspension plasma spraying (SPS), and very low-pressure plasma spraying (VLPPS) techniques. The initial feedstock, as well as the deposited coatings, were characterized and compared in terms of their phase composition. The as-sprayed amorphous content, microstructure, and porosity of the coatings were further analyzed. Based on this preliminary investigation, the HVOF process stood out from the other techniques as it enabled the production of vertical crack-free coatings with higher crystallinity in comparison with the APS and SPS techniques in atmospheric conditions. Nevertheless, VLPPS was found to be the preferred process for the deposition of Yb2Si2O7 coatings with desired characteristics in a controlled-atmosphere chamber. 相似文献
6.
Hsin Wang Ralph B. Dinwiddie Wallace D. Porter 《Journal of Thermal Spray Technology》2010,19(5):879-883
Thermal diffusivities of air plasma sprayed (APS) thermal barrier coatings (TBCs) were measured by the laser flash method.
The data were used to calculate thermal conductivity of TBCs when provided with density and specific heat data. Due to the
complicated microstructure and other processing-related parameters, thermal diffusivity of TBCs can vary as much as three-
to four-fold. Data collected from over 200 free-standing ZrO2-7-8wt.%Y2O3 TBCs are presented. The large database gives a clear picture of the expected “band” of thermal diffusivity values. When this
band is used as a reference for thermal diffusivity of a specific TBC, the thermal transport property of the TBC can be more
precisely described. This database is intended to serve researchers and manufacturers of TBCs as a valuable resource for the
evaluation of TBCs. 相似文献
7.
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
8.
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
9.
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
10.
Fabrication and Properties of Plasma-Sprayed Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/ZrO<Subscript>2</Subscript> Composite Coatings 总被引:1,自引:0,他引:1
N. Dejang A. Limpichaipanit A. Watcharapasorn S. Wirojanupatump P. Niranatlumpong S. Jiansirisomboon 《Journal of Thermal Spray Technology》2011,20(6):1259-1268
Al2O3
/xZrO2 (where x = 0, 3, 13, and 20 wt.%) composite coatings were deposited onto mild steel substrates by atmospheric plasma spraying of mixed
α-Al2O3 and nano-sized monoclinic-ZrO2 powders. Microstructural investigation showed that the coatings comprised well-separated Al2O3 and ZrO2 lamellae, pores, and partially molten particles. The coating comprised mainly of metastable γ-Al2O3 and tetragonal-ZrO2 with trace of original α-Al2O3 and monoclinic-ZrO2 phases. The effect of ZrO2 addition on the properties of coatings were investigated in terms of microhardness, fracture toughness, and wear behavior.
It was found that ZrO2 improved the fracture toughness, reduced friction coefficient, and wear rate of the coatings. 相似文献
11.
12.
C. Piña-Hernández L. Hernández L. M. Flores-Vélez L. F. del Castillo O. Domínguez 《Journal of Materials Engineering and Performance》2007,16(4):470-476
We present preliminary results concerning natural rubber reinforced with nanometric ZnFe2O4 obtained from an industrial solid waste. The study investigate the influence of these nanometric ceramic particles on the
processing as well as the mechanical properties of the obtained rubber composite, opening the possibility of partial replacement
of carbon black and exposing a new potential composite material. The hardness of unfilled and reinforced rubber increased
as nanometric ZnFe2O4 was increased. Besides, tensile properties of the reinforced rubber were measured, observing once again that as the amount
of nanometric ZnFe2O4 particles was increased, ultimate strength improved from 2.5 MPa to almost 20 MPa. 相似文献
13.
CHENG Hua LU Zhouguang LIU Ying YANG Haihua GU Yingying LI Wei TANG Yougen 《稀有金属(英文版)》2011,30(6):602-606
Eu3+ doped La2Ti2O7 nanocrystals with pure monoclinic phase and size of about 100 nm were prepared by a citric acid (CA) assisted sol-gel method.
Techniques of thermo-gravimetric (TG) and differential scanning calorimetry (DSC), X-ray diffraction (XRD), as well as transmission
electron microscopy (TEM) were employed to characterize the as-synthesized nanoparticles. Furthermore, photoluminescence (PL)
performances of the Eu3+ doped La2Ti2O7 nanocrystals were evaluated with focus on the effects of calcination temperature and Eu3+ doping concentration on the photoluminescence properties. 相似文献
14.
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
15.
Ya-Xin Xu Xiao-Tao Luo Cheng-Xin Li Guan-Jun Yang Chang-Jiu Li 《Journal of Thermal Spray Technology》2016,25(3):526-534
A novel approach to prepare a coating system containing an in situ grown Cr2O3 diffusion barrier between a nickel top layer and 310SS was reported. Cold spraying was employed to deposit Ni(O) interlayer and top nickel coating on the Cr-contained stainless steel substrate. Ni(O) feedstock was prepared by mechanical alloying of pure nickel powders in ambient atmosphere, acting as an oxygen provider. The post-spray annealing was adopted to grow in situ Cr2O3 layer between the substrate and nickel coating. The results revealed that the diffusible oxygen can be introduced into nickel powders by mechanical alloying. The oxygen content increases to 3.25 wt.% with the increase of the ball milling duration to 8 h, while Ni(O) powders maintain a single phase of Ni. By annealing the sample in Ar atmosphere at 900 °C, a continuous Cr2O3 layer of 1-2 μm thick at the interface between 310SS and cold-sprayed Ni coating is formed. The diffusion barrier effect evaluation by thermal exposure at 750 °C shows that the Cr2O3 oxide layer effectively suppresses the outward diffusion of Fe and Cr in the substrate effectively. 相似文献
16.
Xianhui Wang Shuhua Liang Ping Yang Zikang Fan 《Journal of Materials Engineering and Performance》2010,19(9):1330-1336
Al2O3/Cu composites were prepared by external addition of Al2O3, and the effect of Al2O3 content on microstructure, density, hardness, electrical conductivity and vacuum electrical breakdown properties was studied.
The results show that with increasing Al2O3 addition, the density of Al2O3/Cu composite significantly decreases, the hardness sharply increases and then slowly decreases, but the electrical conductivity
invariably decreases. The vacuum breakdown test shows that with increasing Al2O3 addition, the breakdown strength first sharply increases and then decreases when the Al2O3 content exceeds 1.2 wt.%; the chopping current always exhibits a decreasing trend and the arc life first increases and then
decreases. According to the morphology of arc erosion and analysis, the arc erosion resistance increases and then decreases
sharply. In the range of experiments, the optimal arc erosion resistance of Al2O3/Cu composite can be obtained with the addition of 1.2 wt.% Al2O3. 相似文献
17.
K. A. Habib D. L. Cano C. T. Caudet M. S. Damra I. Cervera J. Bellés P. Ortells 《Journal of Materials Engineering and Performance》2017,26(4):1647-1656
The influence of micrometric alumina (low surface area-to-volume ratio) and nanometric alumina (high surface area-to-volume ratio) on microstructure, hardness and abrasive wear of a NiCrBSi hardfacing alloy coating applied to an AISI 304 substrate using flame spraying (FS) combined with surface flame melting (SFM) is studied. Remelting after spraying improved the mechanical and tribological properties of the coatings. Microstructural characterization using XRD, SEM and EDS indicated that alumina additions produced similar phases (NiSi, Ni3B, CrC and Ni31Si12) regardless of the alumina size, but the phases differed in morphology, size distribution and relative proportions from one coating to another. The addition of 12 wt.% nanometric Al2O3 increased the phases concentration more than five- to sixfold and reduced the hard phases size about four-to threefold compared with NiCrBSi + 12 wt.% micrometric Al2O3. Nanoalumina led to reduced mass loss during abrasive wear compared to micrometric alumina and greater improvement in hardness. 相似文献
18.
A glass based on the P2O5-ZnO-Sb2O3 ternary system was modified with various additives, such as RO (R=Ca, Ba and Mn), B2O3 and V2O5, for low temperature and low expansion sealing materials. The glass transition temperature (Tg) and coefficient of thermal expansion (CTE) were monitored and reduced with additive compositions of RO. Additional incorporation
of B2O3 at the expense of RO also showed a similar result. Significant improvement was observed when the glass was modified with
V2O5. A glass showing Tg<350 °C along with CTE<65×10−7/°C was found, suggesting a high potential for low temperature sealing materials especially for display applications. The
role of the quaternary element within the glass is discussed, along with the structural effect using Raman spectroscopy. 相似文献
19.
The thermodynamic database of the ZrO2-Gd2O3-Y2O3-Al2O3 system is up-dated taking into account new data on lattice stabilities of ZrO2, Gd2O3 and Y2O3 and heat capacity measurements for the monoclinic phase Gd4Al2O9 and phase with garnet structure Gd3Al5O12. New data for the heat capacities of Gd2Zr2O7 (pyrochlore) and GdAlO3 (perovskite) as well as on the enthalpy of formation of fluorite solid solutions (Zr1−x
Gd
x
)O2−x/2 were found to be in good agreement with calculated results. In comparison with the previous assessment, taking into account
new experimental data resulted in a change of the melting character of the Gd4Al2O9 phase from a peritectic one to a congruent one in the Gd2O3-Al2O3 system. Correspondently, in the ternary system ZrO2-Gd2O3-Al2O3, the melting character of the three-phase assemblage Gd2O3 (B), Gd4Al2O9 and GdAlO3 changed from eutectic to transition type U. The T
0-lines for T/M and F/T diffusionless transformations and driving force of partitioning to equilibrium assemblage T + F were
calculated in the ZrO2-Gd2O3-Y2O3 system. 相似文献
20.
The powders of pure Al, Fe, and Zr for preparing Al78Fe20Zr2 were subject to a high-energy planetary ball milling. The microstructure evolution of the mixtures at the different intervals
of milling was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential scanning
calorimetry (DSC). It was found that a nearly complete amorphization could be achieved in the mixtures after ball milling
for 23 h. Further ball milling led to the crystallization of the amorphous powders. A long time ball milling, e.g., 160 h,
led to a complete crystallization of the amorphous powders and the formation of Al3Zr and Al13Fe4. The crystallization products caused by ball milling are almost the same as that produced by isothermal annealing of the
amorphous powders in vacuum at 800 K for 1 h. 相似文献