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Corrosion behavior of Gd_(2)Zr_(2)O_(7)thermal barrier coatings under Fe-containing environmental sediment attack

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Journal of Advanced Ceramics 2024年第4期13卷 447-462页

作者： Lei Guo yanyan Li kai yan School of Materials Science and Engineering Tianjin UniversityTianjin 300072China Tianjin Key Laboratory of Advanced Joining Technology Key Lab of Advanced Ceramics and Machining Technology of Ministry of EducationTianjin 300072China Key Laboratory of Special Equipment Safety and Energy-saving for State Market Regulation China Special Equipment Inspection&Research InstituteBeijing 100029China

Environmental sediments mainly consisting of CaO–MgO–Al_(2)O_(3)–SiO_(2)(CMAS)corrosion are a serious threat to thermal barrier coatings(TBCs),in which Fe element is usually ***_(2)Zr_(2)O_(7)TBCs are famous for their excellent CMAS *** this study,the characteristics of Fe-containing environmental sediments(CMAS-Fe)and their corrosiveness to Gd_(2)Zr_(2)O_(7)coatings were *** types of CMAS-Fe glass with different Fe contents were *** melting points were measured to be 1322–1344℃,and the high-temperature viscosity showed a decreasing trend with increasing Fe *** corrosion behavior of four types of CMAS-Fe to Gd_(2)Zr_(2)O_(7)coatings at 1350℃was *** the initial corrosion stage(0.1 h),anorthite was precipitated in CMAS-Fe with a high Ca:Si ratio,while Fe-garnet was formed in the melt with the highest Fe *** the corrosion time resulted in the formation of a reaction layer,which exhibited an interpenetrating network composed of Gd-oxyapatite,ZrO_(2),and residual *** spinel was precipitated within the reaction *** 1 h or even longer time,the reaction layers tended to be stable and compact,which had comparable hardness and fracture toughness to those of Gd_(2)Zr_(2)O_(7)*** the cyclic CMAS-Fe attack,the residual CMAS-Fe in the interpenetrating network provided a pathway for the redeposited CMAS-Fe infiltration,resulting in the continuous growth of the reaction *** a result,the Gd_(2)Zr_(2)O_(7)coatings had a large consumption in the thickness,degrading the coating ***,the Gd_(2)Zr_(2)O_(7)coatings exhibit unsatisfactory corrosion resistance to CMAS-Fe attack.

关键词： thermal barrier coatings(TBCs) Gd_(2)Zr_(2)O_(7) Fe-containing CaO-MgO-Al2O3-SiO_(2)(CMAS) corrosion resistance reaction layer

Drag Effects of Solute and Second Phase Distributions on the Grain Growth Kinetics of Pre-Extruded Mg-6Zn Alloy

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Journal of Materials Science & Technology 2016年第12期32卷 1260-1266页

作者： Zhaoyang Jin Donghua Yu Xintong Wu kai Yin kai yan College of Mechanical Engineering Yangzhou University

In order to control the grain size during hot forming,grain growth behavior of a pre-extruded Mg-6Zn magnesium alloy and its correlation with solute and second phase distribution were *** annealing was conducted on a Gleeble-1500 thermo-mechanical *** mean grain size Dg of each annealed specimen was measured by the quantitative metallography *** grain growth kinetics of the Mg-6Zn alloy annealed at 473-623 K was obtained as Dg^4- Dg0^4=2.25 ×10^11 exp（-95450）by the least square linear regression *** deviation of grain growth exponent n = 4 from the theoretical value of 2 may be attributed to the presence of solute zinc and second phases which will retard the boundary *** observations show that the non-uniform distribution of grain size for samples pre-extruded or annealed at low temperatures is closely related to the non-uniform distribution of fine and dispersed second phases but not to the non-uniform distribution of solute *** indicates that second phase pinning effect plays an important role in microstructure refinement.

关键词： Grain growth kinetics Second phase distribution Solute dragging Magnesium alloys

Oxidation behaviour of electron beam physical vapour deposition β-NiAlHf coatings at 1100℃ in dry and humid atmospheres

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Rare Metals 2016年第7期35卷 513-519页

作者： kai yan Hong-Bo Guo Hui Peng Sheng-kai Gong School of Materials Science and Engineering Beihang University Beijing Key Laboratory for Advanced Functional Material and Thin Film Technology Beihang University

NiA1 intermetallic compounds attract increas- ing attention for high-temperature applications due to their combination of excellent properties, especially as metallic protective coatings on superalloys or as bond coats in thermal barrier coatings （TBCs）. Oxidation behaviour of the β-NiA1Hf coatings prepared by electron beam physical vapour deposition （EB-PVD） was investigated at 1100 ℃ for short time and 100h in 20% 02＋Ar and 15 % H20 ＋ Ar, respectively. The results of mass changes re- veal that the addition of minor reactive element Hf sig- nificantly improves the cyclic oxidation resistance of the 13- NiA1 coatings in both dry and humid atmospheres. During the initial oxidation stage, water vapour retards the phase transformation from 0-A1203 to a-A1203. Moreover, com- pared with the case in dry atmosphere, water vapour sig- nificantly reduces the surface roughness of the oxide scales formed on EB-PVD β-NiA1Hf coatings after 100 h cyclic oxidation, which corresponds with the difference of surface morphologies of the oxide scales.

关键词： β-NiA1Hf coatings Water vapour Oxidation Phase transformation Roughness

High-temperature oxidation behaviour of minor Hf-dopedβ-NiAI single crystals in dry and humid atmospheres

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Rare Metals 2023年第8期42卷 2767-2773页

作者： kai yan Jian He Hong-Bo Guo School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100191China State Key Laboratory of Virtual Reality Technology and Systems Beihang UniversityBeijing 100191China School of Energy and Power Engineering Beihang UniversityBeijing 100191China School of Materials Science and Engineering Beihang UniversityBeijing 100191China

Oxidation behaviour of undopedβ-NiAl andβ-NiAl-0.05Hf single crystals were investigated at 1100℃in 20 vol%O_(2)+Ar and 15 vol%H2O+Ar,*** contrary to the well-known beneficial effect of Hf additions on the oxidation behaviour of polycrystallineβ-NiAl,severe-scale spallation is observed forβ-NiAl-0.05Hf single-crystal alloy,especially in dry *** is proposed that the presence of the grain boundaries in the polycrystalline substrate enables proper content of Hf segregating at the grain boundaries of the oxide scale and at the scale-substrate interface,which promotes the conditions required for reactive element *** the reactive element effect of Hf does not work,its strong affinity with oxygen will accelerate the process of high-temperature ***,the absence of the grain boundaries as fast diffusion paths partially compromises the adverse influence of water vapour on cyclic oxidation resistance ofβ-NiAl single crystal,resulting in considerable suppression of the oxidation rate and less loss of protection compared with that in dry *** addition,interfacial cavities are observed in dry and humid atmospheres,which may eventually result in the spallation of the oxide scale.

关键词： Oxidation Reactive element Water vapour β-NiAl Grain boundary

Common Properties of the Operator Products in Local Spectral Theory

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Acta Mathematica Sinica,English Series 2015年第11期31卷 1715-1724页

作者： kai yan Xiao Chun FANG Department of Mathematics Tongji University

Let X,Y be Banach spaces, A,D ： X - Y and B,C ： Y - X be the bounded linear operators satisfying operator equation set ACD=DBD DBA=ACAIn this paper, we show that AC and BD share some basic operator properties such as the injectivity and the invertibility. Moreover, we show that AG＇ and BD share many common local spectral properties including SVEP, Bishop property （β） and Dunford property （C）.

关键词： Jacobson's lemma operator equation set common property local spectral theory

Finite element modelling on microstructure evolution during multi-pass hot compression for AZ31 alloys using incremental method

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Journal of Materials Science & Technology 2017年第11期33卷 1255-1262页

作者： Zhaoyang Jin kai Yin kai yan Defeng Wu Juan Liu Zhenshan Cui School of Mechanical Engineering Yangzhou University Yangzhou 225127 China School of Chemistry & Chemical Engineering Yangzhou University Yangzhou 225127 China Nationai Die and Mold CAD Engineering Research Center Shanghaifiao Tong University Shanghai 200030 China

Based on the principle of piecewise linearization, the incremental forms of microstructure evolution models were integrated into the thermo-mechanical coupled finite element（FE） model to simulate nonlinear microstructure evolution during multi-pass hot deformation. This is an unsteady-state deformation where dynamic recrystallization（DRX）, meta-dynamic recrystallization（MDRX）, static recrystallization（SRX） and grain growth（GG） take place during hot deformation or deformation interval. The distributions of deformation and microstructure for cylindrical AZ31 sample during single-pass and double-pass hot compressions were quantitatively calculated and compared with the metallographic observation. It is shown that both the deformation and microstructure are non-uniformly distributed due to the presence of friction between the die and the flat end of sample. The average grain size and its standard deviation under the double-pass hot compression are slightly smaller than those under single-pass *** simulated average grain sizes agree well with the experiments, which validates that the developed FE model on the basis of incremental forms of microstructure evolution models is reasonable.

关键词： Incremental method Microstructure evolution Multi-pass hot compression Finite element method Magnesium alloys

Synthesis, Crystal Structure and Copper Complex of 1,3-Alternate p-tert-Butylthiacalix[4]arene 2-picolyl Schiff Base

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Chemical Research in Chinese Universities 2014年第2期30卷 245-249页

作者： HUANG Kun LIU kai yan Chaoguo College of Chemistry & Chemical Engineering Yangzhou University Yangzhou 225002 P.R.China

A p-tert-butylthiacalix[4]arene-based polydentated ligand with four Schiff base units on 1,3-alternate position at lower rim has been prepared in three steps,which coordinated to copper ion to form a novel dicopper *** structures of the polydentated thiacalixarene ligand and copper complex were fully characterized by spectroscopy and X-ray single crystal diffraction method.

关键词： Calixarene Thiacalixarene Schiff base Pyridine Copper complex Crystal structure

Electrodeposited 3D hierarchical NiFe microflowers assembled from nanosheets robust for the selective electrooxidation of furfuryl alcohol

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Green Energy & Environment 2023年第3期8卷 874-882页

作者： Biying Liu Man Zhang Yaoyu Liu Yuchen Wang kai yan Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology School of Environmental Science and EngineeringSun Yat-sen University135 Xingang Xi RoadGuangzhou510275China

A robust and green strategy for the selective upgrading of biomass-derived platform chemicals towards highly valuable products is important for the sustainable ***,the efficient electrocatalytic oxidation of biomass-derived furfuryl alcohol(FFA)into furoic acid(FurAc)catalyzed by the electrodeposited non-precious NiFe microflowers was successfully reached under the low temperature and ambient *** 3D hierarchical NiFe microflowers assembled from ultrathin nanosheets were controllably synthesized by the electrodeposition method and uniformly grown on carbon fiber paper(CFP).Electrochemical analysis confirmed that NiFe nanosheets more preferred in the selective oxidation of FFA(FFAOR)than oxygen evolution reaction(OER).The linear sweep voltammetry(LSV)in FFAOR displayed a clear decrease towards lower potential,resulting in 30 mV reduction of overpotential at 20 mA cm^(-2) compared with that of *** optimal catalyst Ni_(1)Fe_(2) nanosheets exhibited the highest selectivity of FurAc(94.0%)and 81.4%conversion of FFA within 3 ***,the influence of various reaction parameters on FFAOR was then explored in *** that,the reaction pathway was investigated and rationally *** outstanding performance for FFAOR can be ascribed to the unique structure of 3D flower-like NiFe nanosheets and oxygen vacancies,resulting in large exposure of active sites,faster electron transfer and enhanced adsorption of *** findings highlight a facile and convenient mean with a promising green future,which is promising for processing of various biomass-derived platform chemicals into value-added products.

关键词： Electrodeposition Microflowers assembled by nanosheets NiOOH Oxygen vacancies Electrochemical oxidation Furfuryl alcohol Furoic acid

Synthesis, Characterization and Gas Sensing Properties of In(OH)_3 and In_2O_3 Nanorods through Carbon Spheres Template Method

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Journal of Materials Science & Technology 2012年第5期28卷 396-400页

作者： Xifeng Lu Lei Zhang Hui Zhao kai yan yan Cao Lumin Meng Lunan Institute of Coal Chemical Engineering Jining 272000China College of Chemistry and Life Sciences Zhejiang Normal UniversityJinhua 321004China Jining Institute of Supervision and Inspection on Product Quality Jining 272000China

Poly-crystalline In（OH） 3 nanorods have been successfully prepared via a urea-based precipitation using the colloidal carbon spheres as the templates. After calcinations, the resulted In 2 O 3 nanorods with poly-crystalline structure were fabricated. Structure and morphology of the product were characterized by X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. The possible formation process was schemed. The sensor gas properties towards C 2 H 5 OH and CO were examined.

关键词： Nanostructures Self-assembly Characterization Gas sensor