About
42
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Introduction
My research interests are focused on developments of novel thermal barrier coatings based on rare earth zirconates as well as novel environmental barrier coating system applied on the next-generation gas turbine hot-section components. To this end, both theoretical and experimental approaches are employed. The first principle caculations are used for the prediction of material properties. After selection, the properties of bulk materials are thoroughly investigated with an emphasis on both thermophysical and mechanical properties. After modificatoin of comprehensive properties for a promisiing candidate material, it is then made to coating form by conventional coating technology such as air plasma spraying.
Current institution
Additional affiliations
September 2009 - September 2013
Position
- PhD Student at School of Materials
Description
- working on the novel thermal barrier coating system
Publications
Publications (42)
The mechanical and thermophysical properties of KD‐SA SiCf/SiC composites manufactured by the hybrid chemical vapor infiltration (CVI)–precursor impregnation and pyrolysis (PIP) technique were systematically studied at 1400, 1600, and 1800°C, respectively, under argon atmosphere for 1 h. The results show that Si element in SiC fiber escapes and dif...
Using citric acid, ethylene glycol, ZrOCl2·8H2O, HfOCl2·8H2O, TiCl4, NbCl5, and TaCl5 as raw materials, the (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C high‐entropy ceramic precursor was prepared by Pechini coordination polymerization method. The precursor and pyrolysis products were analyzed and characterized by different methods. The results showed that the pre...
Environmental barrier coatings (EBCs) are crucial to the reliability and durability of SiCf/SiC composite components seeking applications in hot sections of next‐generation advanced aero‐engines. The cracks initiated and developed in EBCs owing to various reasons during service greatly undermine their lifespans. To address this problem, in this wor...
SiC ceramic materials were prepared using a combination of direct ink writing (DIW) and liquid silicon infiltration (LSI). In this study, we investigated the effects of the content of a copolymer of isobutene and maleic anhydride (ISOBAM) on the rheological properties of the slurry, microstructure of green bodies and SiC ceramics, and bending prope...
Environmental barrier coatings (EBCs) are crucial for SiCf/SiC composites to resist water vapor-oxygen corrosion and maintain the stability of their structure and properties in a complex combustion environment at high temperatures. In this work, an EBC system, composing Yb2Si2O7 topcoats and Si bond coats, has been prepared by an air plasma sprayin...
Lanthanum hafnate (La2Hf2O7) with a pyrochlore structure has excellent high temperature stability and low thermal conductivity, which is promising for thermal/environmental barrier coatings (T/EBCs) applications. To reduce its thermal expansion coefficient (TEC) so as to better match SiCf/SiC composites, a smaller tetravalent dopant Ti⁴⁺ has been i...
The protection effects of an environmental barrier coating (EBC) consisting of silicon bond coat and mixed ytterbium monosilicate and ytterbium disilicate composite topcoat are directly evaluated by measuring the strength retention rate of SiCf/SiC composites completely wrapped up by the previous EBCs after soaking in a mixed oxygen and water vapor...
The corrosion behavior and corresponding mechanisms of SiCf/SiC composites have been studied in a mixed water vapor and oxygen environment at 1300 ℃ for up to 120 h.It has been unveiled that, the formation of liquid amorphous silica fulfilling gaps left by the oxidation of pyrolytic carbon interphase is extremely detrimental due to that: 1) the pre...
In this study, PyC coating with different thickness was prepared on SiC fibers via chemical vapor deposition method. Uncoated and PyC coated SiC fibers were heat treated in Ar atmosphere under different annealing condition. The effects of PyC coating on the mechanical properties of SiC fibers at room temperature were investigated. The morphology, c...
Cf/Hf0.5Zr0.5C-SiC composites were prepared by introducing Hf0.5Zr0.5C matrix (11 cycles) and SiC matrix (9 cycles) into the carbon cloth preform through precursor impregnation and pyrolysis (PIP) process. The influence of the introduction time of SiC matrix on the microstructure and mechanical properties of Cf/Hf0.5Zr0.5C-SiC composites was studie...
The SiCf/SiC composites have been manufactured by a hybrid route combining chemical vapor infiltration (CVI) and precursor infiltration and pyrolysis (PIP) techniques. A relatively low deposition rate of CVI SiC matrix is favored ascribing to that its rapid deposition tends to cause a ‘surface sealing’ effect, which generates plenty of closed pores...
Cf/SiC–ZrC ultra-high temperature ceramic matrix composites prepared by precursor impregnation and pyrolysis (PIP) method were exposed to laser with energy density of kW level and the ablation behavior and mechanism were investigated. The results show that under different ablation times, the composites exhibited similar ablation region divisions, n...
A bi-layer environmental barrier coating (EBC) consisting of silicon(Si) bond coat/mixed ytterbium disilicate (Yb2Si2O7) and ytterbium monosilicate (Yb2SiO5) topcoats has been successfully prepared to completely wrap up the SiCf/SiC composites and the protective effects of such EBC have been evaluated by soaking them in a mixed 50% O2 and 50% H2O c...
The poor fracture toughness of La2Zr2O7 severely limits its application as a high temperature thermal barrier coating topcoat material. To toughen it, a ferroelastic second phase, NdAlO3, with a Curie temperature of 1367°C has been introduced to form x NdAlO3/(1‐x) La2Zr2O7 composite ceramics by a spark plasma sintering technique, where x = 10, 20,...
In this paper, the A 2 B 2 O 7-type compounds RE 2 FeTaO 7 synthesized via a solid-state reaction were researched for high-temperature applications, and their thermophysical properties were documented for the first time. The relationships between thermophysical properties and structures of RE 2 FeTaO 7 were established, the results show that the RE...
The mechanical and thermophysical properties of Xenotime-type REPO4 (RE = Lu, Yb, Er, Y and Sc) have been theoretically and experimentally investigated for a potential environmental barrier coating (EBC) topcoat application. The results show that the current studied REPO4 exhibits a quasi-ductile property, suggesting a potential long life expectanc...
Monoclinic (m) and monoclinic-prime (m′) phases of Yb(TaxNb1−x)O4 ceramics were synthesized successfully, and the relationships between the crystal structures and the thermophysical properties were investigated by various methods. A ferroelastic domain existed in the m-Yb(TaxNb1-x)O4 ceramics, as observed by a scanning electron microscopy, which su...
3D needled carbon fiber reinforced composites (C/C-SiC) were fabricated by gaseous silicon infiltration (GSI) for different reaction times, followed by further densification with liquid silicon infiltration (LSI). The density, flexural modulus and flexural strength increased as a spatially connected SiC structure developed, but the flexural strengt...
The microstructure morphologies have been characterized by high resolution laboratory X-ray computed tomography in Carbon Fiber Reinforced Carbon and Silicon Carbide (C/C-SiC) ceramic composites fabricated by Gaseous Silicon Infiltration (GSI) from C/C preforms of three different architectures: 3D stitched cloth fabric; 3D orthogonal woven fabric;...
In situ observations of damage development within 3-dimensional 5-directional braided carbon fiber reinforced carbon and silicon carbide (C/C-SiC) ceramic composites, fabricated by gaseous silicon infiltration (GSI) and precursor infiltration pyrolysis (PIP), have been obtained using laboratory X-ray computed tomography during in situ flexural test...
3D needle-punched C/C-SiC composites were fabricated from carbon fiber reinforced carbon (C/C) preforms, with densities of 1.05 g/cm³ and 1.28 g/cm³, by the gaseous silicon infiltration (GSI) method at fabrication temperatures from 1500 °C to 1800 °C. The compressive strengths and elastic moduli in transverse direction are larger than those measure...
Damage development has been observed in situ within a 3-dimensional needle-punched carbon fiber reinforced carbon and silicon carbide (C/C-SiC) ceramic composite, as compressive loads were applied longitudinally, transversely and obliquely to its anisotropic structure. Laboratory X-ray computed tomographs were analyzed using digital volume correlat...
Corrosion resistance of rare earth monosilicates (RE2SiO5, RE = Lu, Yb, Tm, Er, Ho, Dy, Y, and Sc) in water vapor has been studied using the first-principles calculations. The results show that the water vapor corrosion resistance of RE2SiO5 demonstrates the following order: Sc2SiO5 > Dy2SiO5 > Y2SiO5 > Ho2SiO5 > Er2SiO5 > Yb2SiO5 > Tm2SiO5 > Lu2Si...
The yttrium heavily doped La2Zr2O7 solid solutions coatings, with a Y to La molar ratio of 1:1, have been successfully prepared by air plasma spraying technique. The evolution of phase composition, phase structure and thermal conductivity of such coatings with annealing at 1300 °C has been investigated. The results show that, a single pyrochlore st...
The poor fracture toughness limits the wide application of the cubic lanthanum zirconate (La2Zr2O7) ceramics. The current study reports a dramatic fracture toughness improvement of lanthanum zirconates by the introduction of lanthanum aluminates (LaAlO3), a ferroelastic second phase. A composite ceramic with the composition of x LaAlO3/ (1-x) La2Zr...
The poor fracture toughness of cubic pyrochlores has severely blocked their wide application. To toughen them, a series of yttrium dopants have been introduced to lanthanum zirconate, creating atomic or phase-scale compressive stress dependent on the concentration of dopants. We find bigger substitutional dopants, rather than smaller ones, can toug...
Effects of SiC/HfC ratios on the ablation and mechanical properties of 3D Cf/HfC-SiC composites by precursor impregnation and pyrolysis (PIP) process were investigated systematically. Both strength (flexural and compressive strength) and modulus increase as the SiC/HfC ratio are improved. The compact and stiff HfC-SiC matrix in addition to the carb...
The poor fracture toughness of La2Zr2O7 hinders its practical application as a thermal barrier coating topcoat material. To toughen La2Zr2O7, metastable tetragonal 8 wt.% yttria-stabilized zirconia (t’-8YSZ), has been introduced into the La2Zr2O7 matrix by plasma spray quenching of 8YSZ powders and spark plasma sintering. An evident fracture toughn...
A series of yttrium-doped lanthanum zirconate (La1−xYx)2Zr2O7 (0 ≤ x ≤ 1) bulk samples were prepared and their ionic conductivities were studied by impedance spectroscopy. It is found that intermixing of Y and La ions increases the conductivity of the end members pyrochlore-type La2Zr2O7 and fluorite-type Y2Zr2O7. Highest conductivity which is 2–3...
The low fracture toughness of lanthanum zirconate (La2Zr2O7, LZ) greatly impedes its wide application as thermal barrier coatings (TBC). The 3 mol% Y2O3-stabilized tetragonal zirconia polycrystals (3Y-TZP) have been introduced to toughen the brittle LZ ceramics. The dispersive 3Y-TZP undergoes a simultaneous t–m transformation upon cooling below a...
The effects and determining factors of substitutional defects on thermal conductivity (k) have been studied by introducing Hf4+ (96% heavier than, but a similar size to, Zr4+) and Ce4+ (21% larger and 50% heavier), to replace Zr4+ on the B site of La2Zr2O7 pyrochlores. La2(Zr1−xCex)2O7, exhibits a flatter k–T curve and a dramatically reduced high-t...
High temperature plateau thermal conductivity (kmin) remains poorly understood despite its crucial importance in thermal insulation components at elevated temperature. We report In/Sc doped La2Zr2O7 pyrochlores with rattlers and oxygen vacancies and their effects on heat transport. Rattlers can dramatically flatten k-T curves at very low doping lev...
The evolution of structure and thermal conductivity (k) has been studied for a range of Y–La2Zr2O7 solid solutions. Within the pyrochlore range (x < 0.40) Y3+ solely substitutes for La3+ below a critical composition factor (x = 0.15), above which it substitutes for both La3+ and the Zr4+. A glass-like k, approaching the amorphous limit, is observed...
Questions
Question (1)
Dear all,
With increasing temepratures, the radiative thermal conduction gradually becomes a nonnegligible part of overall thermal conduction (i.e. lattice plus photon/radiative thermal conduction) in scenarios of typical dielectric materials like ceramics. With the aim of heat insulation such as in the fields of thermal barrier coatings, is there any way to effectively reduce radiative thermal conduction?
Many thanks!!!
Yanfei
