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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 loss.This will prevent electromagnetic waves from entering the EMA materials,finally reducing overall absorbing performance.Here,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 loss.As 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 GHz.In 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 coat.In this study,to achieve the optimal lifetime of TBCs,a lifetime phase diagram was constructed for the entire service of TBCs.Herein,both the thermal mismatch stress during thermal cycling and the TGO growth stress during thermal exposure were considered.First,thickening behavior of the Al_(2)O_(3) scale related to grain size was investigated.Second,transverse delamination failure due to the thermal mismatch stress was analyzed.Third,vertical cracking failure related to early scale growth was explored.Finally,a critical scale grain size of~2.5μm was identified for achieving the optimal lifetime of TBCs.It 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 pre-oxidation.The 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 lifetime.However,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 aero-engine.To 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 temperature.During 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 pass.Meanwhile,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 region.This structure easily makes the intra-column fracture at the porous weak region.The 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 turbines.However,the adhesive transfer frequently occurs between metallic blade tips and aluminum-based composite coatings,resulting in engine vibration and even jam.Many past studies had tried to solve this problem by reducing coating hardness,improving lubrication,or strengthening blade tips,but all had failed.In 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 pair.The coating was developed via a hierarchical structure design.Large spherical pores were uniformly distributed in the continuous epoxy matrix with fine graphite dispersion.By 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 reached.When the metallic blades scrape the epoxy-based composite coating,no adhesive transfer occurs.Besides,a smooth scraped surface is formed by pseudoplastic deformation.This 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

Discovery of a tetrahydroisoquinoline-based CDK9-cyclin T1 proteineprotein interaction inhibitor as an anti-proliferative and anti-migration agent against triple-negative breast cancer cells

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Genes & Diseases 2022年第6期9卷 1674-1688页

作者： Shasha Cheng guan-jun yang Wanhe Wang Dik-Lung Ma Chung-Hang Leung State Key Laboratory of Quality Research in Chinese Medicine Institute of Chinese Medical SciencesUniversity of MacaoTaipaMacao SARPR China Department of Chemistry Hong Kong Baptist UniversityKowloon TongHong Kong SARPR China Institute of Medical Research Northwestern Polytechnical UniversityXi’anShaanxi 710072PR China Department of Biomedical Sciences Faculty of Health SciencesUniversity of MacaoMacao SARPR China

Triple-negative breast cancer(TNBC)is a highly aggressive and metastasizing cancer that has the worst prognosis out of all breast cancer subtypes.The epithelial emesenchymal transition(EMT)and cancer stem cells(CSCs)have been proposed as important mechanisms underlying TNBC metastasis.CDK9 is highly expressed in breast cancer,including TNBC,where it promotes EMT and induces cancer cell stemness.In this study,we have identified a tetrahydroisoquinoline derivative(compound 1)as a potent and selective CDK9-cyclin T1 inhibitor via virtual screening.Interestingly,by targeting the ATP binding site,compound 1 not only inhibited CDK9 activity but also disrupted the CDK9-cyclin T1 proteineprotein interaction(PPI).Mechanistically,compound 1 reversed EMT and reduced the ratio of CSCs by blocking the CDK9-cyclin T1 interaction,leading to reduced TNBC cell proliferation and migration.To date,compound 1 is the first reported tetrahydroisoquinoline-based CDK9-cyclin T1 ATP-competitive inhibitor that also interferes with the interaction between CDK9 and cyclin T1.Compound 1 may serve as a promising scaffold for developing more selective and potent anti-TNBC agents.Our work also provides insight into the role of the CDK9-cyclin T1 PPI on EMT and CSCs and highlights the feasibility and significance of targeting CDK9 for the treatment of TNBC.

关键词： Cancer stem cells CDK9-cyclin T1 Epithelial mesenchymal transition Proteineprotein interaction(PPI) Triple-negative breast cancer(TNBC)

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 service.One 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 exposure.The objective of this study is to obtain sintering-resistant TBCs by tailoring the width of interlamellar pores to avoid multiple connections.Firstly,the mechanism responsible for the multiple connections was revealed.The 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 splats.Consequently,the local surface height increases,which causes multiple connections and healing of the interlamellar pores.Secondly,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 grains.The 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 obtained.Finally,composite TBCs were prepared to form wide interlamellar pores in the coatings.Using this design,the increases in the thermal conductivity(λ)and the elastic modulus(E)can be prevented to a large extent.Thus,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

Pressure infiltration of molten aluminum for densification of environmental barrier coatings

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Journal of Advanced Ceramics 2022年第1期11卷 145-157页

作者： Lin DONG Mei-jun LIU Xiao-Feng ZHANG Xue-Shi ZHUO Jia-Feng FAN guan-jun yang Ke-Song ZHOU State Key Laboratory for Mechanical Behavior ofMaterials School ofMaterials Science and EngineeringXi’an Jiaotong UniversityXi’an 710049China National Engineering Laboratory for Modern Materials Surface Engineering Technology Institute of New MaterialsGuangdong Academy of ScienceGuangzhou 510650China

Environmental barrier coatings(EBCs)effectively protect the ceramic matrix composites(CMCs)from harsh engine environments,especially steam and molten salts.However,open pores inevitably formed during the deposition process provide the transport channels for oxidants and corrosives,and lead to premature failure of EBCs.This research work proposed a method of pressure infiltration densification which blocked these open pores in the coatings.These results showed that it was difficult for aluminum to infiltrate spontaneously,but with the increase of external gas pressure and internal vacuum simultaneously,the molten aluminum obviously moved forward,and finally stopped infiltrating at a depth of a specific geometry.Based on the wrinkled zigzag pore model,a mathematical relationship between the critical pressure with the infiltration depth and the pore intrinsic geometry was established.The infiltration results confirmed this relationship,indicating that for a given coating,a dense thick film can be obtained by adjusting the internal and external gas pressures to drive a melt infiltration.

关键词： infiltration process channel pore densification pressure assistant environmental barrier coating(EBC)

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 essentially.In order to realize the columnar structure deposited by gaseous phase units,the transition behavior of gaseous phase units to clusters must be fundamentally understood.This work investigated the transport process of gaseous phase units in the PS-PVD near-substrate boundary layer along with the condensation behavior.The Monte Carlo method was used to examine the transport process and condensation behavior of gaseous phase units under different scale boundary layers.Simulation results show that it is easier to form more numerous larger clusters at the edge of the plasma jet than at the center.Based 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 presented.And 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