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Journal of Advanced Ceramics 2024年第7期13卷 976-986页

作者： Lin Dong Wen-Qi yang Lin Chen guan-jun yang Chang-Jiu Li State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi’an Jiaotong UniversityXi’an 710049China Xi’an Aerospace Engine Company Limited in China Aerospace Science and Technology Corporation Xi’an 710065China

The lifetime of Si-based environmental barrier coatings(EBCs)is constrained by thermally grown SiO_(2)oxidelayer(SiO_(2)-TGO),which can cause premature cracking and *** address this issue,a new approach for surfacemodification using aluminum is *** oxidation performance was examined in a 50 vol%H_(2)O-50 vol%O_(2)environment at 1350℃for up to 300 *** results indicate that a dense ytterbium aluminum garnet(YbAG)layer wasformed after modification,decreasing the porosity by 80%.Due to the elimination of fast diffusion channels and the lowoxygen permeability of YbAG,aluminum modification significantly reduced the growth rate of SiO_(2)-TGO by nearly twoorders of ***,its thickness decreased by more than 70%after 300 h of exposure.A diffusioncontrolled oxidation mechanism indicates that the modified dense surface is equivalent to an initial SiO_(2)layer with a specificthickness,causing a shift in the oxidation time and increasing the oxidation *** research provides valuableinsights for designing Si-based EBC with improved lifetimes.

关键词： environmental barrier coating(EBC) oxidation modification diffusion cracking

Durable dual-state duplex Si-HfO_(2)with excellent oxidation and cracking resistance

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Journal of Advanced Ceramics 2024年第3期13卷 388-401页

作者： Lin Chen Jing-Chuan Luo Wen-Qi yang Chang-Jiu Li guan-jun yang State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi’an Jiaotong UniversityXi’an 710049China Xi’an Aerospace Engine Company Limited in CASC Xi’an 710065China

The lifetime of Si bond coatings in environmental barrier coatings is constrained by phase-transition-induced cracking of the SiO_(2)*** this study,Si-HfO_(2)dual-state duplex composite materials are proposed to address this issue by partially forming HfSiO_(4)and minimizing the SiO_(2)*** as-prepared composite exhibited a structure comprising discrete HfO_(2)“bricks”embedded in a continuous Si“mortar”,while the oxidized state transformed into discrete HfSiO_(4)“bricks”within continuous thin SiO_(2)“mortars”.The results indicate that continuous thin SiO_(2)contributes to reducing the oxidation rate to a level comparable to that of pure Si,and discrete HfSiO_(4)particles aid in relieving phase transition-induced stress and inhibiting crack propagation,thereby enhancing oxidation and cracking resistance ***,the composite with 20 mol%HfO_(2)and a mean particle size of~500 nm at 1370℃exhibited a service lifetime 10 times greater than that of pure *** research provides valuable insights for designing Si-based bond coatings with improved service lifetime.

关键词： oxidation environmental barrier coatings(EBCs) phase transition cracking bond coatings

Condensation behavior of gaseous phase during transported in the near-substrate boundary layer of plasma spray-physical vapor deposition

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Journal of Materials Science & Technology 2021年第8期67卷 127-134页

作者： Mei-jun Liu guan-jun yang State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi'an fiaotong UniversityXi’anShaanxi710049PR China

Plasma spray-physical vapor deposition(PS-PVD)has exhibited the potential ability to prepare columnar structures for advanced thermal barrier coatings(TBCs).The coating structure is nominally affected by operating parameters,but it is controlled by the type of deposition unit actually and *** order to realize the columnar structure deposited by gaseous phase units,the transition behavior of gaseous phase units to clusters must be fundamentally *** work investigated the transport process of gaseous phase units in the PS-PVD near-substrate boundary layer along with the condensation *** Monte Carlo method was used to examine the transport process and condensation behavior of gaseous phase units under different scale boundary *** results show that it is easier to form more numerous larger clusters at the edge of the plasma jet than at the *** on the understanding of the changes in deposition unit caused by the condensation of gaseous phase in the near-substrate boundary layer of PS-PVD,an outlook towards TBCs with different structures is *** it is in good agreement with the experimental data.

关键词： Condensation behavior Transport process Cluster Boundary layer PS-PVD

Epitaxial growth and cracking of highly tough 7YSZ splats by thermal spray technology

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Journal of Advanced Ceramics 2018年第1期7卷 17-29页

作者： Lin CHEN guan-jun yang State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and Engineering Xi'an Jiaotong University

Thermally sprayed coatings are essentially layered materials and contain large numbers of lamellar pores. It is thus quite necessary to clarify the formation mechanism of lamellar pores which significantly influence coating performances. In the present study, to elaborate the formation mechanism of lamellar pores, the yttria-stabilized zirconia(ZrO_2–7 wt% Y_2O_3, 7YSZ) splats, which have high fracture toughness and tetragonal phase stability, were employed. Interestingly, anomalous epitaxial growth occurred for all deposition temperatures in spite of the extremely high cooling rate,which clearly indicated chemical bonding and complete contact at splat/substrate interface before splat cooling. However, transverse spallation substantially occurred for all deposition temperatures in spite of the high fracture toughness of 7YSZ, which revealed that the lamellar pores were from transverse cracking/spallation due to the large stress during splat cooling. Additionally, fracture mechanics analysis was carried out, and it was found that the stress arose from the constraint effect of the shrinkage of the splat by locally heated substrate with the value about 1.97 GPa. This clearly demonstrated that the stress was indeed large enough to drive transverse cracking/spallation forming lamellar pores during splat cooling. All of these contribute to understanding the essential features of lamellar bonding and further tailoring the coating structures and performance.

关键词： epitaxial growth crack patterns transverse cracking/spallation stress locally heated substrate

Boosting electromagnetic wave absorption of Ti_(3)AlC_(2) by improving effective electrical conductivity

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先进陶瓷(英文) 2023年第8期12卷 1533-1546页

作者： Kai-Yu Guo Lin Chen guan-jun yang State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi’an Jiaotong UniversityXi’an 710049China

Electromagnetic wave-absorbing(EMA)materials at high temperatures are limited by poor conduction loss(L_(c)).However,adding conductors simultaneously increases the conduction loss and interfacial polarization loss,leading to a conflict between impedance matching(Z_(in)/Z_(0))and electromagnetic wave *** will prevent electromagnetic waves from entering the EMA materials,finally reducing overall absorbing ***,the effective electrical conductivity(σ)is enhanced by synchronizing particle size and grain number of Ti_(3)AlC_(2) to increase the conduction loss and avoid the conflict between the impedance matching and the electromagnetic wave *** a result,the best-absorbing performance with an effective absorption bandwidth(EAB)of 4.8 GHz(10.6–15.4 GHz)at a thickness of only 1.5 mm is realized,which is the best combination of wide absorption bandwidth and small thickness,and the minimum reflection loss(RL_(min))reaches−45.6 dB at 4.1 *** short,this work explores the regulating mechanism of the EMA materials of effective electrical conductivity by simulated calculations using the Vienna ab-initio Simulation Package(VASP)and COMSOL as well as a series of experiments,which provide new insight into a rational design of materials with anisotropic electrical conductivity.

关键词： anisotropic electrical conductivity conduction loss(Lc) interfacial polarization loss(LIP) effective electrical conductivity co-optimize impedance matching(Zin/Z0) electromagnetic wave loss

Critical scale grain size for optimal lifetime of TBCs

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Journal of Materials Science & Technology 2022年第20期115卷 241-250页

作者： Lin Chen Guo-Hui Meng Chang-Jiu Li guan-jun yang State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi’an Jiaotong UniversityXi’an 710049China

Thermal barrier coatings(TBCs)suffer from spalling failure resulting from the rapid growth of thermally grown oxides(TGO)on the metallic bond *** this study,to achieve the optimal lifetime of TBCs,a lifetime phase diagram was constructed for the entire service of ***,both the thermal mismatch stress during thermal cycling and the TGO growth stress during thermal exposure were ***,thickening behavior of the Al_(2)O_(3) scale related to grain size was ***,transverse delamination failure due to the thermal mismatch stress was ***,vertical cracking failure related to early scale growth was ***,a critical scale grain size of~2.5μm was identified for achieving the optimal lifetime of *** was experimentally proved that vertical cracking of the Al_(2)O_(3) scale occurred during early oxidation as the scale grain size was larger than~4μm after *** proposed lifetime phase diagram and critical scale grain size effect serve as novel criteria for the design of next-generation durable TBCs.

关键词： TGO growth Grain size Grain boundaries Channel cracking Service lifetime

Heterogeneous layered structure in thermal barrier coatings by plasma spray-physical vapor deposition

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Journal of Advanced Ceramics 2023年第2期12卷 386-398页

作者： Yan-Hong LU Lu HUANG Mei-jun LIU guan-jun yang Chang-Jiu LI State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi’an Jiaotong UniversityXi’an 710049China

The unique columnar structure endows thermal barrier coatings(TBCs)prepared by plasma spray-physical vapor deposition(PS-PVD)with high thermal insulation and long ***,the coating delamination failure resulting from an intra-column fracture(within a column rather than between columns)is a bottleneck in the solid dust particle impact environment for *** clarify the intra-column fracture mechanism,a basic layer deposition model is developed to explore a heterogeneous weak-to-strong layered structure formed by a local transient in-situ deposit *** the PS-PVD,an in-situ deposit surface is continuously updated due to constantly being covered by vapor condensation,showing a transient temperature,which means that the in-situ deposit surface temperature rises sharply in short period of 0.2 s of depositing a thin layer during a single ***,the increasing temperature of the in-situ deposit surface results in an experimentally observed heterogeneous weak-to-strong structure,showing a continuous transition from a porous weak structure at the bottom region to a dense strong structure at the top *** structure easily makes the intra-column fracture at the porous weak *** results shed light on improving TBC lifetime by restraining the intra-column fracture.

关键词： transient temperature in-situ deposit surface heterogeneous layered structure fracture mechanism plasma spray-physical vapor deposition(PS-PVD)

Self-lubricating epoxy-based composite abradable seal coating eliminating adhesive transfer via hierarchical design

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Journal of Materials Science & Technology 2022年第9期104卷 145-154页

作者： Yun-qi Tong Wei Li Qiu-sheng Shi Lin Chen guan-jun yang State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi’an Jiaotong UniversityXi’an 710049China AECC Hunan Aviation Powerplant Research Institute Zhuzhou 412002China

Aluminum-based composite abradable seal coatings are pivotal to improving the efficiency of aero engines or gas ***,the adhesive transfer frequently occurs between metallic blade tips and aluminum-based composite coatings,resulting in engine vibration and even *** past studies had tried to solve this problem by reducing coating hardness,improving lubrication,or strengthening blade tips,but all had *** this paper,we proposed a novel epoxy-based composite abradable seal coating,eliminating adhesive transfer by changing metal-to-metal scraping pair to metal-to-polymer scraping *** coating was developed via a hierarchical structure *** spherical pores were uniformly distributed in the continuous epoxy matrix with fine graphite *** adding 20 vol.%graphite and 50 vol.%hollow microspheres,a self-lubricating epoxy-based coating of 0.26 friction coefficient with thermal conductivity of 0.28 W/(m·K),coating HR15 Y hardness at 54.8,and bonding strength at 18.7 MPa can be *** the metallic blades scrape the epoxy-based composite coating,no adhesive transfer ***,a smooth scraped surface is formed by pseudoplastic *** epoxy-based composite abradable seal coating opens a new way to improve the efficiency and reliable operations of air engine compressors.

关键词： Epoxy-based composite coating Hierarchical structure design Self-lubricating Pseudoplastic deformation

Achieving the high phase purity of CH_3NH_3PbI_3 film by two-step solution processable crystal engineering

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Journal of Materials Science & Technology 2018年第8期34卷 1405-1411页

作者： Yan Li Bin Ding guan-jun yang Chang-Jiu Li Cheng-Xin Li State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi'an Jiaotong University

To date, it is still a great challenge for highly efficient perovskite devices to realize the high quality per- ovskite films with high purity, high coverage ratio and good crystallization by two-step scalable solution method. In this study, a series PbI2 films with tunable micro-architecture of Pbl2 crystals are prepared via solution processable crystal engineering. The perovskite film, prepared by optimized pit spacing in gas pumped PbI2 film at 1000 Pa, shows the highest film quality, including no residual Pbl2 phase, compact morphology, and improved photoluminescence intensity. A transformation kinetics shows that the pit spacing strongly influences both the mass transfer and the sequential intercalation reaction between CH3NH31 and PbI2 crystals, which ultimately determines the full reaction state of the perovskite film. The perovskite solar cells assembled by the perovskite film show both high power-conversion efficiency and good reproducibility of photovoltaic performance due to the restrained charge recombination arising from the high quality perovskite film.

关键词： High phase purity CHHNH3PbI3 film Two-step solution method Perovskite solar cells

Tailoring sintering-resistant thermal barrier coatings by considering critical healing width of two-dimensional interlamellar pores

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Journal of Advanced Ceramics 2023年第7期12卷 1317-1330页

作者： guang-Rong Li Tao Liu Xiao-Tao Luo guan-jun yang Chang-Jiu Li State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi'an Jiaotong UniversityXi'an 710049China

Large degradation in thermal insulation and strain tolerance is a main headache and a primary cause of the failure for plasma-sprayed thermal barrier coatings(TBCs)during *** mechanism behind such degradation is the healing of interlamellar pores formed by multiple connections between edges of a pore,which significantly speeds up healing during thermal *** objective of this study is to obtain sintering-resistant TBCs by tailoring the width of interlamellar pores to avoid multiple ***,the mechanism responsible for the multiple connections was *** splat surfaces before and after thermal treatments were characterized via an atomic force microscope(AFM).The roughening of the pore surface occurs during thermal exposure,along with the grain growth inside the ***,the local surface height increases,which causes multiple connections and healing of the interlamellar ***,critical widths of the interlamellar pores for avoiding the multiple connections during thermal exposure are established by correlating the extent of surface roughening with the growth of individual *** height increase of the splat surface and the growth of the grain size(D)were found to increase with the exposure temperature and duration.A relationship linking the height increase and the growth of the grain size induced by thermal exposure in plasma-sprayed ceramic splats was ***,composite TBCs were prepared to form wide interlamellar pores in the *** this design,the increases in the thermal conductivity(λ)and the elastic modulus(E)can be prevented to a large ***,sintering-resistant TBCs that maintain high thermal insulation and strain tolerance,even afer long thermal exposure,can be created.

关键词： thermal barrier coatings(TBCs) air plasma spraying(APS) multiple connections grain growth sintering-resistant structure