Fe(Al,Ta)/Fe_(2)Ta(Al)eutectic composites with solidification rates of 6,20,30,and 80μm/s were prepared by a modified Bridgman directional solidification technology.The coarse Fe_(2)Ta(Al)Laves phase was precipitated...Fe(Al,Ta)/Fe_(2)Ta(Al)eutectic composites with solidification rates of 6,20,30,and 80μm/s were prepared by a modified Bridgman directional solidification technology.The coarse Fe_(2)Ta(Al)Laves phase was precipitated at the eutectic colony boundary during the solidification process,which can affect the stability of microstructure and properties of the composites.The coarse Laves phase was refined using different heat treatment processes in the present paper.The influences of different heat treatment parameters on the Laves phase content,lamella/rod spacing,and mechanical properties were investigated in detail.In addition,the corrosion behaviors of Fe(Al,Ta)/Fe_(2)Ta(Al)eutectic composites before and after being annealed heat treatment in a 3 g/L Na_(2)S_(2)O_(3)solution were also studied.It is shown that both the content of Laves phase and lamella/rod spacing are gradually decreased after heat treatment.Micro-hardness is decreased,while the yield strength,compressive strength,and corrosion resistance are improved.The optimum heat treatment process is selected as well.展开更多
Microstructure control is a great challenge in the high-temperature gradient directional solidification of eutectic composite ceramics due to the complex solidification behavior.Herein,the microstructure trans-formati...Microstructure control is a great challenge in the high-temperature gradient directional solidification of eutectic composite ceramics due to the complex solidification behavior.Herein,the microstructure trans-formation of faceted Al_(2)O_(3)/Er_(3)Al_(5)O_(12) thermal emission eutectic composite ceramics is explored over wide ranges of compositions(13.5 mol%-22.5 mol%Er_(2)O_(3))and solidification rates(2-200μm/s).Entirely cou-pled eutectics with primary phases suppressed are fabricated and the coupled zone is broadened in a wide range of 15.5 mol%-22.5 mol%Er_(2)O_(3) at low solidification rates.The competitive growth between eutectic and dendrite is evaluated on the basis of the maximum interface temperature criterion.In ad-dition,the mechanisms of irregular eutectic spacing selection and adjustment under different solidifi-cation rates are revealed based on Magnin-Kurz model.A successful prediction of lamellar to rod-like eutectics is achieved associated with the dynamic instability of lamellar eutectic and the corresponding enlarged coexistence region is mapped based on the interface undercooling.According to the well mi-crostructure tailoring,the flexural strength of Al_(2)O_(3)/Er_(3)Al_(5)O_(12) eutectic composite ceramics has improved from 508 MPa up to 1800 MPa due to the refined eutectic spacing with low fluctuation.The eutectic composite ceramics show strong selective optical absorption and the intensity increases with the refin-ing microstructure.The as-designed Al_(2)O_(3)/Er_(3)Al_(5)O_(12) composites with microstructural tailoring have great potential as integrations of structural and functional materials.展开更多
Design process of A/ADm-BCn type directional eutectic composites was instanced by investigating Al-Mg-Si-Li and Ni-Mo-C-Al systems in this study by thermoanalysis and directional solidification techniques. It was demo...Design process of A/ADm-BCn type directional eutectic composites was instanced by investigating Al-Mg-Si-Li and Ni-Mo-C-Al systems in this study by thermoanalysis and directional solidification techniques. It was demonstrated that A(D)-BCn eutectic alloys could be obtained more conveniently by using Smith′s thermoanalysis method to trace change of the eutectic Points of A-BCn induced by addition of components D. A/ADm-BCn directional eutectic composites could be produced from directionally solidified A/ADm-BCn alloys after proper heat treatments if components D have higher solid solubility in components A at high temperature and stable of metastable phases ADm could be formed at room temperature.展开更多
As a 3D printing method,laser powder bed fusion(LPBF)technology has been extensively proven to offer significant advantages in fabricating complex structured specimens,achieving ultra-fine microstructures,and enhancin...As a 3D printing method,laser powder bed fusion(LPBF)technology has been extensively proven to offer significant advantages in fabricating complex structured specimens,achieving ultra-fine microstructures,and enhancing performances.In the domain of manufacturing melt-grown oxide ceramics,it encounters substantial challenges in suppressing crack defects during the rapid solidification process.The strategic integration of high entropy alloys(HEA),leveraging the significant ductility and toughness into ceramic powders represents a major innovation in overcoming the obstacles.The ingenious doping of HEA parti-cles preserves the eutectic microstructures of the Al_(2)O_(3)/GdAlO_(3)(GAP)/ZrO_(2)ceramic composite.The high damage tolerance of the HEA alloy under high strain rates enables the absorption of crack energy and alleviation of internal stresses during LPBF,effectively reducing crack initiation and growth.Due to in-creased curvature forces and intense Marangoni convection at the top of the molt pool,particle collision intensifies,leading to the tendency of HEA particles to agglomerate at the upper part of the molt pool.However,this phenomenon can be effectively alleviated in the remelting process of subsequent layer de-position.Furthermore,a portion of the HEA particles partially dissolves and sinks into the molten pool,acting as heterogeneous nucleation particles,inducing the formation of equiaxed eutectic and leading pri-mary phase nucleation.Some HEA particles diffuse into the lamellar ternary eutectic structures,further promoting the refinement of eutectic microstructures due to increased undercooling.The innovative dop-ing of HEA particles has effectively facilitated the fabrication of turbine-structured,conical,and cylindrical ternary eutectic ceramic composite specimens with diameters of about 70 mm,demonstrating significant developmental potential in the field of ceramic composite manufacturing.展开更多
AlCoCrFeNi_(2.1)-xNi_(3)Al(x=0,5.0,7.5,and 10 wt%,denoted as Ni_(3)Al0,Ni_(3)Al5.0,Ni_(3)Al_(7.5),and Ni_(3)Al_(10))eutectic high-entropy alloy(EHEA)matrix composites were fabricated by mechanical alloying and spark p...AlCoCrFeNi_(2.1)-xNi_(3)Al(x=0,5.0,7.5,and 10 wt%,denoted as Ni_(3)Al0,Ni_(3)Al5.0,Ni_(3)Al_(7.5),and Ni_(3)Al_(10))eutectic high-entropy alloy(EHEA)matrix composites were fabricated by mechanical alloying and spark plasma sintering methods.The effects of Ni_(3)Al content on the microstructures,mechanical and wear properties of AlCoCrFeNi_(2.1)EHEA were investigated.The results indicate that the AlCoCrFeNi_(2.1)-xNi_(3)Al composites present cellular grid morphologies composing of FCC/Ll2 and B2 phases,and a small amount of Al_(2)O_(3)and Cr_(7)C_(3)phases.The addition of Ni_(3)Al significantly enhanced the compressive yield strength,compressive fracture strength,compressive strain and wear properties of the AlCoCrFeNi_(2.1)composites.In particular,the Ni_(3)Al_(10)composite exhibits excellent comprehensive mechanical properties.The compressive yield strength,compressive fracture strength and compressive strain of the Ni_(3)Al_(10)composite,are 1845 MPa,2301 MPa and 10.1%,respectively.The friction coefficient,wear width and depth,and mass loss of the Ni_(3)Al_(10)composite were 0.40,0.9 mm,20.5 mm,0.016 g,respectively.Moreover,the wear mechanism of the Ni_(3)Al_(10)composite is major abrasive wear with a small amount of adhesive wear.展开更多
This work mainly involved the preparation of a nano-scale form-stable phase change material（PCM） consisting of capric and myristic acid（CA-MA） binary eutectic acting as thermal absorbing material and nano silicon ...This work mainly involved the preparation of a nano-scale form-stable phase change material（PCM） consisting of capric and myristic acid（CA-MA） binary eutectic acting as thermal absorbing material and nano silicon dioxide（nano-SiO_2） serving as the supporting material. Industrial water glass for preparation of the nano silicon dioxide matrix and CA-MA eutectic mixture were compounded by single-step sol-gel method with the silane coupling agent. The morphology, chemical characterization and form stability property of the composite PCM were investigated by transmission electron microscopy（TEM）, scanning electron microscopy（SEM）, Fourier-transform infrared（FT-IR） spectroscopy and polarizing microscopy（POM）. It was indicated that the average diameter of the composite PCM particle ranged from 30-100 nm. The CA-MA eutectic was immobilized in the network pores constructed by the Si-O bonds so that the composite PCM was allowed no liquid leakage above the melting temperature of the CA-MA eutectic. Differential scanning calorimetry（DSC） and thermogravimetric analysis（TGA） measurement were conducted to investigate the thermal properties and stability of the composite PCM. From the measurement results, the mass fraction of the CA-MA eutectic in the composite PCM was about 40%. The phase change temperature and latent heat of the composite were determined to be 21.15 ℃ and 55.67 J/g, respectively. Meanwhile, thermal conductivity of the composite was measured to be 0.208 W·m^（-1）·K^（-1） by using the transient hot-wire method. The composite PCM was able to maintain the surrounding temperature close to its phase change temperature and behaved well in thermalregulated performance which was verified by the heat storage-release experiment. This kind of form-stable PCM was supposed to complete thermal insulation even temperature regulation by the dual effect of relatively low thermal conductivity and phase change thermal storage-release properties. So it can be formulated that the nanoscale CA-MA/SiO_2 composite PCM with the form-stable property, good thermal storage capacity and relatively low thermal conductivity can be applied for energy conservation as a kind of thermal functional material.展开更多
Fe-Al-Ta eutectic composites were obtained by a modified Bridgman directional solidification technique at different solidification rates.Solidification microstructure transforms from regular eutectic to eutectic colon...Fe-Al-Ta eutectic composites were obtained by a modified Bridgman directional solidification technique at different solidification rates.Solidification microstructure transforms from regular eutectic to eutectic colony with the increase of the solidification rate.The solid/liquid interface of Fe-Al-Ta eutectic evolves from planar interface to cellular interface with the increase of the solidification rate.In addition,threepoint bending method was adopted to study the room-temperature fracture toughness of the as-cast Fe-Al-Ta eutectic alloy and the Fe-Al-Ta eutectic composites.Moreover,the fracture morphologies,the crack propagation path and the strengthening mechanism of Fe-Al-Ta eutectic were discussed.展开更多
Microstructure evolution and solidification behaviour of ZrB_(2)-SiC composite ceramics fabricated by laser surface zone-melting were investigated.Microstructure coarsening at high scanning speed and mi-crostructure r...Microstructure evolution and solidification behaviour of ZrB_(2)-SiC composite ceramics fabricated by laser surface zone-melting were investigated.Microstructure coarsening at high scanning speed and mi-crostructure refining after turning off the laser was observed due to the changes in the solidification rate.The solidification behaviour from bottom to top of the molten pool was studied,where there are some coarsen eutectic bands caused by the secondary heating of the melting pool on the solidified eu-tectic zone in the molten pool.The deviation of melt composition from the eutectic ratio due to the volatilization of SiC can form a coarse primary ZrB_(2) phase among fine eutectic structure(single-phase instability),and the constitutional supercooling due to the accumulation of impurity elements can form coarse eutectic dendrites among fine eutectic structure(two-phase instability).Both single-phase insta-bility and two-phase instability are adverse to the mechanical properties,which should be prevented by adjusting the composition of raw materials and the solidification process.展开更多
A series of dysprosium-based ternary, quadruple, and quintuple bulk metallic glasses （BMGs） based on Dy-Al binary eutectic composition were obtained with the partial substitution of Co, Gd, and Ni elements, for dysp...A series of dysprosium-based ternary, quadruple, and quintuple bulk metallic glasses （BMGs） based on Dy-Al binary eutectic composition were obtained with the partial substitution of Co, Gd, and Ni elements, for dysprosium. The results showed that the Dy31Gd25Co20Al24 alloy, which had the best glass forming ability （GFA）, could be cast into an amorphous rod with a diameter of 5 ram. The GFA of alloys was evaluated on the basis of the supercooled liquid region width, 7 parameter, the formation enthalpy, and the equivalent electronegativity difference of amorphous alloys. It was found that the eutectic composition was closely correlated with the GFA of the Dy-based BMGs.展开更多
In order to confirm the eutectic composition, eutectic temperature and phases of Al-rich Al-RE（La, Ce, Pr, Nd） binary systems, the eutectic Al-RE alloys with the controversial compositions were investigated. The sca...In order to confirm the eutectic composition, eutectic temperature and phases of Al-rich Al-RE（La, Ce, Pr, Nd） binary systems, the eutectic Al-RE alloys with the controversial compositions were investigated. The scanning electron microscopy/energy dispersive spectroscopy（SEM/EDS）, differential scanning calorimetric（DSC） and cooling curve tests analysis indicated that a similar eutectic composition（~12 wt.% RE） on the Al-rich region was observed in the Al-La, Al-Ce, Al-Pr and Al-Nd alloys, and the eutectic structure of the alloys was consisted of α-Al and α-Al11RE3 phases by combining with X-ray diffraction（XRD） tests. In addition, the eutectic temperatures determined by DSC and cooling curve tests were very close and around 645 oC.展开更多
In order to improve the thermal storage capacity of expanded vermiculite（EV） based formstable composite PCM（FS-PCM） via organic modification of EV, first, EV was modified with a sodium stearate（Na St） as surface...In order to improve the thermal storage capacity of expanded vermiculite（EV） based formstable composite PCM（FS-PCM） via organic modification of EV, first, EV was modified with a sodium stearate（Na St） as surface modifier, and organic EV（OEV） with hydrophobicity and higher adsorption capacity for fatty acid was obtained. A novel capric-stearic acid eutectic（CA-SA）/OEV FS-PCM with high thermal storage capacity was then developed. OEV and CA-SA/OEV were characterized by scanning electron microscopy（SEM）, X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FTIR）, differential scanning calorimetry（DSC）, thermal gravimetry（TG）, and thermal cycling test. Results showed that OEV has obvious hydrophobicity and a higher adsorption capacity for fatty acid. Its adsorption ratio has increased by 48.71% compared with that of EV. CA-SA/OEV possesses high thermal storage density（112.52 J/g）, suitable melting temperature（20.49 ℃）, good chemical compatibility, excellent thermal stability and reliability, indicating great application potential for building energy efficiency. Moreover, organic modification of inorganic matrix may offer novel options for improving its adsorption capacity for organic PCMs and increasing heat storage capacity of corresponding FS-PCMs.展开更多
Although rare earth zirconates(RE_(2)Zr_(2)O_(7))have garnered attention as viable candidates for thermal barrier coatings(TBCs),they suffer from low fracture toughness and accelerated calcium–magnesium–alumina–sil...Although rare earth zirconates(RE_(2)Zr_(2)O_(7))have garnered attention as viable candidates for thermal barrier coatings(TBCs),they suffer from low fracture toughness and accelerated calcium–magnesium–alumina–silicate(CMAS)melt corrosion at high service temperatures,which impedes their practical application.In this work,we developed a series of REAlO_(3)/RE_(2)Zr_(2)O_(7)(RE=La,Nd,Sm,Eu,Gd,and Dy)composites with a eutectic composition that not only significantly enhanced the fracture toughness by more than 40%relative to that of RE_(2)Zr_(2)O_(7)but also exhibited improved resistance to CMAS corrosion.The increase in toughness arises from multiple mechanisms,such as ferroelastic toughening,fine-grain strengthening,and residual stress toughening,all of which trigger more crack defects and energy consumption.Additionally,the CMAS penetration depth of the REAlO_(3)/RE_(2)Zr_(2)O_(7)composites is approximately 36%lower than that of RE_(2)Zr_(2)O_(7).Al–O constituents in composites can capture CaO,SiO_(2),and MgO in CMAS melts and increase their viscosity,resulting in enhanced CMAS corrosion resistance.The thermophysical properties of the REAlO_(3)/RE_(2)Zr_(2)O_(7)composites were also investigated,and their coefficient of thermal expansion and thermal conductivity are comparable to those of 7–8 wt%Y_(2)O_(3)partially stabilized ZrO2(YSZ),indicating their potential as TBC materials.展开更多
CE （=%C＋（1/3）x（%Si）） does not suit experiment results in many cases. In this work, the effect of alloy elements on primary crystal temperature was measured and the relationship between primary crystal temperatu...CE （=%C＋（1/3）x（%Si）） does not suit experiment results in many cases. In this work, the effect of alloy elements on primary crystal temperature was measured and the relationship between primary crystal temperature （Tc） and carbon equivalent （CEL） was investigated. The results show that Tc （Celsius degree） = 1650-110 × （%C） -25 × （%Si）＋3 × （%Mn） -35 × （%P） -71 × （%5）-2 × （%Ni） -7 × （%Cr）; CEL=%C ＋ 0.23×（%Si）-0.03× （%Mn）＋0.32×（%P）＋0.64×（%S） ＋0.02×（%Ni）＋0.06×（%Cr）. That is, in hypo eutectic composition, carbon equivalent should be calculated with CEL=%C＋ 0.23×（%Si）, not with CE=%C＋（1/3） x（%Si）.展开更多
The Si-TaSi2 eutectic in situ composite, which has highly-aligned and uniformly-distributed TaSi2 fibers in the Si matrix, can be obtained when the solidification rate changes from 0.3 to 9.0 mm/min. It is very intere...The Si-TaSi2 eutectic in situ composite, which has highly-aligned and uniformly-distributed TaSi2 fibers in the Si matrix, can be obtained when the solidification rate changes from 0.3 to 9.0 mm/min. It is very interesting that one or two TaSi2 fibers are curved when the solidification rate reaches 6.0 mm/min, although it is very brittle in general. The formation mechanism of the curved fiber is discussed and mechanical properties of the TaSi2 fibers are examined by nanoindentation. It is found that the hardness and the elastic modulus of the bended TaSi2 fiber are much higher than that of the straight TaSi2 fiber. Moreover, the reasons why the mechanical properties of the straight TaSi2 fiber are different from that of the curved TaSi2 fiber are discussed. This can be ascribed to internal stress which results from mismatch of the thermal expansion coefficients of the two phases and different crystallographic orientations.展开更多
Eutectic and near-eutectic high entropy alloys （HEAs） have recently attracted a great deal of interest because of their promising properties, such as an excellent castability and unique combination of good ductility...Eutectic and near-eutectic high entropy alloys （HEAs） have recently attracted a great deal of interest because of their promising properties, such as an excellent castability and unique combination of good ductility and high strength. However, in the absence of a phase diagram, it remains a non-trivial task to find a eutectic or near-eutectic composition for a HEA system, which usually demands a tremendous amount of efforts if a trial-and-error approach is followed. In this paper, we briefly review the thermodynamics that governs the entectic solidification in regular binary and ternary alloys, and proceed to the discussion for the design of eutectic HEAs. Based on the data reported, we then propose an improved strategy which may enable an efficient search for the eutectic or near eutectic HEA compositions.展开更多
Polymer-based solid electrolytes have been extensively studied for solid-state lithium metal batteries to achieve high energy density and reliable security.But,its practical application is severely limited by low ioni...Polymer-based solid electrolytes have been extensively studied for solid-state lithium metal batteries to achieve high energy density and reliable security.But,its practical application is severely limited by low ionic conductivity and slow Li+transference.Herein,based on the“binary electrolytes”of poly(vinylidene fluoride-chlorotrifluoroethylene)(P(VDF-CTFE))and lithium salt(LiTFSI),a kind of eutectogel hybrid electrolytes(EHEs)with high Li+transference number was developed via tuning the spontaneous coupling of charge and vacated space generated by Li-cation diffusion utilizing the Li6.4La3Zr1.4Ta0.6O12(LLZTO)dopant.LLZTO doping promotes the dissociation of lithium salt,increases Li+carrier density,and boosts ion jumping and the coordination/decoupling reactions of Li+.As a result,the optimized EHEs-10%possess a high Li-transference number of 0.86 and a high Li+conductivity of 3.2×10–4 S·cm–1 at room temperature.Moreover,the prepared EHEs-10%composite solid electrolyte presents excellent lithiumphilic and compatibility,and can be tested stably for 1,200 h at 0.3 mA·cm–2 with assembled lithium symmetric batteries.Likewise,the EHEs-10%films match well with high-loading LiFePO4 and LiCoO2 cathodes(>10 mg·cm–2)and exhibit remarkable interface stability.Particularly,the LiFePO4//EHEs-10%//Li and LiCoO2//EHEs-10%//Li cells deliver high rate performance of 118 mAh·g–1 at 1 C and 93.7 mAh·g–1 at 2 C with coulombic efficiency of 99.3%and 98.1%,respectively.This work provides an in-depth understanding and new insights into our design for polymer electrolytes with fast Li+diffusion.展开更多
基金Funded by the Key Industry Innovation Chain(Group)Project of Shaanxi Province,China(No.2019ZDLGY 04-04)the Project of Yulin Science and Technology Bureau(No.2023-CXY-197)。
文摘Fe(Al,Ta)/Fe_(2)Ta(Al)eutectic composites with solidification rates of 6,20,30,and 80μm/s were prepared by a modified Bridgman directional solidification technology.The coarse Fe_(2)Ta(Al)Laves phase was precipitated at the eutectic colony boundary during the solidification process,which can affect the stability of microstructure and properties of the composites.The coarse Laves phase was refined using different heat treatment processes in the present paper.The influences of different heat treatment parameters on the Laves phase content,lamella/rod spacing,and mechanical properties were investigated in detail.In addition,the corrosion behaviors of Fe(Al,Ta)/Fe_(2)Ta(Al)eutectic composites before and after being annealed heat treatment in a 3 g/L Na_(2)S_(2)O_(3)solution were also studied.It is shown that both the content of Laves phase and lamella/rod spacing are gradually decreased after heat treatment.Micro-hardness is decreased,while the yield strength,compressive strength,and corrosion resistance are improved.The optimum heat treatment process is selected as well.
基金supported by the National Natural Science Foundation of China (Nos.52130204,52174376,and 51822405)the Guangdong Basic and Applied Basic Research Foundation (No.2021B1515120028)+2 种基金the Science and Technology Innovation Team Plan of Shaan Xi Province (No.2021TD-17)the Youth Innovation Team of Shaanxi Universities,Fundamental Research Funds for the Central Universities (No.D5000210902)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University (Nos.CX2021056,CX2021066,and CX2022033),China.
文摘Microstructure control is a great challenge in the high-temperature gradient directional solidification of eutectic composite ceramics due to the complex solidification behavior.Herein,the microstructure trans-formation of faceted Al_(2)O_(3)/Er_(3)Al_(5)O_(12) thermal emission eutectic composite ceramics is explored over wide ranges of compositions(13.5 mol%-22.5 mol%Er_(2)O_(3))and solidification rates(2-200μm/s).Entirely cou-pled eutectics with primary phases suppressed are fabricated and the coupled zone is broadened in a wide range of 15.5 mol%-22.5 mol%Er_(2)O_(3) at low solidification rates.The competitive growth between eutectic and dendrite is evaluated on the basis of the maximum interface temperature criterion.In ad-dition,the mechanisms of irregular eutectic spacing selection and adjustment under different solidifi-cation rates are revealed based on Magnin-Kurz model.A successful prediction of lamellar to rod-like eutectics is achieved associated with the dynamic instability of lamellar eutectic and the corresponding enlarged coexistence region is mapped based on the interface undercooling.According to the well mi-crostructure tailoring,the flexural strength of Al_(2)O_(3)/Er_(3)Al_(5)O_(12) eutectic composite ceramics has improved from 508 MPa up to 1800 MPa due to the refined eutectic spacing with low fluctuation.The eutectic composite ceramics show strong selective optical absorption and the intensity increases with the refin-ing microstructure.The as-designed Al_(2)O_(3)/Er_(3)Al_(5)O_(12) composites with microstructural tailoring have great potential as integrations of structural and functional materials.
文摘Design process of A/ADm-BCn type directional eutectic composites was instanced by investigating Al-Mg-Si-Li and Ni-Mo-C-Al systems in this study by thermoanalysis and directional solidification techniques. It was demonstrated that A(D)-BCn eutectic alloys could be obtained more conveniently by using Smith′s thermoanalysis method to trace change of the eutectic Points of A-BCn induced by addition of components D. A/ADm-BCn directional eutectic composites could be produced from directionally solidified A/ADm-BCn alloys after proper heat treatments if components D have higher solid solubility in components A at high temperature and stable of metastable phases ADm could be formed at room temperature.
基金supported by the National Natural Science Foundation of China(Nos.52130204,52174376,52202070,51822405)Guangdong Basic and Applied Basic Research Foundation(No.2021B1515120028)+6 种基金TQ Innovation Foundation(No.23-TQ09-02-ZT-01-005)Aeronautical Science Foundation of China(No.20220042053001)Science and Technology Innovation Team Plan of Shaanxi Province(No.2021TD-17)Key R&D Project of Shaanxi Province(No.2024GX-YBXM-220)Thousands Person Plan of Jiangxi Province(JXSQ2020102131)Fundamental Research Funds for the Central Universities(Nos.D5000230348,D5000220057)China Scholarship Council(Nos.202206290133,202306290190).
文摘As a 3D printing method,laser powder bed fusion(LPBF)technology has been extensively proven to offer significant advantages in fabricating complex structured specimens,achieving ultra-fine microstructures,and enhancing performances.In the domain of manufacturing melt-grown oxide ceramics,it encounters substantial challenges in suppressing crack defects during the rapid solidification process.The strategic integration of high entropy alloys(HEA),leveraging the significant ductility and toughness into ceramic powders represents a major innovation in overcoming the obstacles.The ingenious doping of HEA parti-cles preserves the eutectic microstructures of the Al_(2)O_(3)/GdAlO_(3)(GAP)/ZrO_(2)ceramic composite.The high damage tolerance of the HEA alloy under high strain rates enables the absorption of crack energy and alleviation of internal stresses during LPBF,effectively reducing crack initiation and growth.Due to in-creased curvature forces and intense Marangoni convection at the top of the molt pool,particle collision intensifies,leading to the tendency of HEA particles to agglomerate at the upper part of the molt pool.However,this phenomenon can be effectively alleviated in the remelting process of subsequent layer de-position.Furthermore,a portion of the HEA particles partially dissolves and sinks into the molten pool,acting as heterogeneous nucleation particles,inducing the formation of equiaxed eutectic and leading pri-mary phase nucleation.Some HEA particles diffuse into the lamellar ternary eutectic structures,further promoting the refinement of eutectic microstructures due to increased undercooling.The innovative dop-ing of HEA particles has effectively facilitated the fabrication of turbine-structured,conical,and cylindrical ternary eutectic ceramic composite specimens with diameters of about 70 mm,demonstrating significant developmental potential in the field of ceramic composite manufacturing.
基金supported by the Support Program for Youth Innovation Technology in Colleges and Universities of Shandong Province(2023KJ095)the Qingdao Municipal Science and Technology Benefits the People Special Fund(24-1-8-cspz-3-nsh).
文摘AlCoCrFeNi_(2.1)-xNi_(3)Al(x=0,5.0,7.5,and 10 wt%,denoted as Ni_(3)Al0,Ni_(3)Al5.0,Ni_(3)Al_(7.5),and Ni_(3)Al_(10))eutectic high-entropy alloy(EHEA)matrix composites were fabricated by mechanical alloying and spark plasma sintering methods.The effects of Ni_(3)Al content on the microstructures,mechanical and wear properties of AlCoCrFeNi_(2.1)EHEA were investigated.The results indicate that the AlCoCrFeNi_(2.1)-xNi_(3)Al composites present cellular grid morphologies composing of FCC/Ll2 and B2 phases,and a small amount of Al_(2)O_(3)and Cr_(7)C_(3)phases.The addition of Ni_(3)Al significantly enhanced the compressive yield strength,compressive fracture strength,compressive strain and wear properties of the AlCoCrFeNi_(2.1)composites.In particular,the Ni_(3)Al_(10)composite exhibits excellent comprehensive mechanical properties.The compressive yield strength,compressive fracture strength and compressive strain of the Ni_(3)Al_(10)composite,are 1845 MPa,2301 MPa and 10.1%,respectively.The friction coefficient,wear width and depth,and mass loss of the Ni_(3)Al_(10)composite were 0.40,0.9 mm,20.5 mm,0.016 g,respectively.Moreover,the wear mechanism of the Ni_(3)Al_(10)composite is major abrasive wear with a small amount of adhesive wear.
基金Funded by the National Natural Science Foundation of China(No.51308275)Natural Science Foundation of Liaoning Province(No.SY2016004)the Colleges and Universities Excellent Talents Supporting Plan Program of Liaoning Province(No.LJQ2015049)
文摘This work mainly involved the preparation of a nano-scale form-stable phase change material（PCM） consisting of capric and myristic acid（CA-MA） binary eutectic acting as thermal absorbing material and nano silicon dioxide（nano-SiO_2） serving as the supporting material. Industrial water glass for preparation of the nano silicon dioxide matrix and CA-MA eutectic mixture were compounded by single-step sol-gel method with the silane coupling agent. The morphology, chemical characterization and form stability property of the composite PCM were investigated by transmission electron microscopy（TEM）, scanning electron microscopy（SEM）, Fourier-transform infrared（FT-IR） spectroscopy and polarizing microscopy（POM）. It was indicated that the average diameter of the composite PCM particle ranged from 30-100 nm. The CA-MA eutectic was immobilized in the network pores constructed by the Si-O bonds so that the composite PCM was allowed no liquid leakage above the melting temperature of the CA-MA eutectic. Differential scanning calorimetry（DSC） and thermogravimetric analysis（TGA） measurement were conducted to investigate the thermal properties and stability of the composite PCM. From the measurement results, the mass fraction of the CA-MA eutectic in the composite PCM was about 40%. The phase change temperature and latent heat of the composite were determined to be 21.15 ℃ and 55.67 J/g, respectively. Meanwhile, thermal conductivity of the composite was measured to be 0.208 W·m^（-1）·K^（-1） by using the transient hot-wire method. The composite PCM was able to maintain the surrounding temperature close to its phase change temperature and behaved well in thermalregulated performance which was verified by the heat storage-release experiment. This kind of form-stable PCM was supposed to complete thermal insulation even temperature regulation by the dual effect of relatively low thermal conductivity and phase change thermal storage-release properties. So it can be formulated that the nanoscale CA-MA/SiO_2 composite PCM with the form-stable property, good thermal storage capacity and relatively low thermal conductivity can be applied for energy conservation as a kind of thermal functional material.
基金This work was supported financially by the National Natural Science Foundation of China(No.51201121)the Science and Technology Foundation for Selected Overseas Chinese Scholars of Shaanxi Province(2015)+1 种基金the Key Industry Innovation Chain(group)Project of Shaanxi Province(No.2019ZDLGY 04-04)the Research Project of Shaanxi Engineering Technology Research Center for Wear-resisting Materials(No.2016NMZX03).
文摘Fe-Al-Ta eutectic composites were obtained by a modified Bridgman directional solidification technique at different solidification rates.Solidification microstructure transforms from regular eutectic to eutectic colony with the increase of the solidification rate.The solid/liquid interface of Fe-Al-Ta eutectic evolves from planar interface to cellular interface with the increase of the solidification rate.In addition,threepoint bending method was adopted to study the room-temperature fracture toughness of the as-cast Fe-Al-Ta eutectic alloy and the Fe-Al-Ta eutectic composites.Moreover,the fracture morphologies,the crack propagation path and the strengthening mechanism of Fe-Al-Ta eutectic were discussed.
基金supported by the National Natural Science Foundation of China(Nos.52130204,52174376,52202070)the Guangdong Basic and Applied Basic Research Foundation(No.2021B1515120028)+5 种基金the TQ Innovation Foundation(No.23-TQ09-02-ZT-01-005)the Aeronautical Science Foundation of China(No.20220042053001)the Science and Technology Innovation Team Plan of ShaanXi Province(No.2021TD-17)the Thousands Person Plan of Jiangxi Province(No.JXSQ2020102131)the Xi’an Science and Technology Program(No.21ZCZZHXJS-QCY6-0005)the Fundamental Research Funds for the Central Universities(Nos.D5000230348 and D5000220057).
文摘Microstructure evolution and solidification behaviour of ZrB_(2)-SiC composite ceramics fabricated by laser surface zone-melting were investigated.Microstructure coarsening at high scanning speed and mi-crostructure refining after turning off the laser was observed due to the changes in the solidification rate.The solidification behaviour from bottom to top of the molten pool was studied,where there are some coarsen eutectic bands caused by the secondary heating of the melting pool on the solidified eu-tectic zone in the molten pool.The deviation of melt composition from the eutectic ratio due to the volatilization of SiC can form a coarse primary ZrB_(2) phase among fine eutectic structure(single-phase instability),and the constitutional supercooling due to the accumulation of impurity elements can form coarse eutectic dendrites among fine eutectic structure(two-phase instability).Both single-phase insta-bility and two-phase instability are adverse to the mechanical properties,which should be prevented by adjusting the composition of raw materials and the solidification process.
基金supported by the National Natural Science Foundation of China (50571054)
文摘A series of dysprosium-based ternary, quadruple, and quintuple bulk metallic glasses （BMGs） based on Dy-Al binary eutectic composition were obtained with the partial substitution of Co, Gd, and Ni elements, for dysprosium. The results showed that the Dy31Gd25Co20Al24 alloy, which had the best glass forming ability （GFA）, could be cast into an amorphous rod with a diameter of 5 ram. The GFA of alloys was evaluated on the basis of the supercooled liquid region width, 7 parameter, the formation enthalpy, and the equivalent electronegativity difference of amorphous alloys. It was found that the eutectic composition was closely correlated with the GFA of the Dy-based BMGs.
基金supported by the National Natural Science Foundation of China(21573077,51373055)the International Lead and Zinc Research Organization Foundation(ILZRO/IZA/CN201212)
文摘In order to confirm the eutectic composition, eutectic temperature and phases of Al-rich Al-RE（La, Ce, Pr, Nd） binary systems, the eutectic Al-RE alloys with the controversial compositions were investigated. The scanning electron microscopy/energy dispersive spectroscopy（SEM/EDS）, differential scanning calorimetric（DSC） and cooling curve tests analysis indicated that a similar eutectic composition（~12 wt.% RE） on the Al-rich region was observed in the Al-La, Al-Ce, Al-Pr and Al-Nd alloys, and the eutectic structure of the alloys was consisted of α-Al and α-Al11RE3 phases by combining with X-ray diffraction（XRD） tests. In addition, the eutectic temperatures determined by DSC and cooling curve tests were very close and around 645 oC.
基金Funded by the Major State Research Development Program of China during the 13th Five-Year Plan Period(No.2016YFC0700904)the Science and Technology Support Program of Hubei Province(Nos.2014BAA134 and 2015BAA107)
文摘In order to improve the thermal storage capacity of expanded vermiculite（EV） based formstable composite PCM（FS-PCM） via organic modification of EV, first, EV was modified with a sodium stearate（Na St） as surface modifier, and organic EV（OEV） with hydrophobicity and higher adsorption capacity for fatty acid was obtained. A novel capric-stearic acid eutectic（CA-SA）/OEV FS-PCM with high thermal storage capacity was then developed. OEV and CA-SA/OEV were characterized by scanning electron microscopy（SEM）, X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FTIR）, differential scanning calorimetry（DSC）, thermal gravimetry（TG）, and thermal cycling test. Results showed that OEV has obvious hydrophobicity and a higher adsorption capacity for fatty acid. Its adsorption ratio has increased by 48.71% compared with that of EV. CA-SA/OEV possesses high thermal storage density（112.52 J/g）, suitable melting temperature（20.49 ℃）, good chemical compatibility, excellent thermal stability and reliability, indicating great application potential for building energy efficiency. Moreover, organic modification of inorganic matrix may offer novel options for improving its adsorption capacity for organic PCMs and increasing heat storage capacity of corresponding FS-PCMs.
基金supported by the National Key R&D Program of China(No.2021YFB3702300)the National Natural Science Foundation of China(No.52022042)+2 种基金the Project of the Science Center for Gas Turbine(No.HT-P2022-DB-Ⅳ-002-001)the National Science and Technology Major Project(No.J2019-Ⅶ−0008-0148)the Research on the Development and Preparation of Thermal Barrier Coating Materials on New Generation of Heavy-duty Gas Turbines(No.UGTC-HT-WXKT-2022-032).
文摘Although rare earth zirconates(RE_(2)Zr_(2)O_(7))have garnered attention as viable candidates for thermal barrier coatings(TBCs),they suffer from low fracture toughness and accelerated calcium–magnesium–alumina–silicate(CMAS)melt corrosion at high service temperatures,which impedes their practical application.In this work,we developed a series of REAlO_(3)/RE_(2)Zr_(2)O_(7)(RE=La,Nd,Sm,Eu,Gd,and Dy)composites with a eutectic composition that not only significantly enhanced the fracture toughness by more than 40%relative to that of RE_(2)Zr_(2)O_(7)but also exhibited improved resistance to CMAS corrosion.The increase in toughness arises from multiple mechanisms,such as ferroelastic toughening,fine-grain strengthening,and residual stress toughening,all of which trigger more crack defects and energy consumption.Additionally,the CMAS penetration depth of the REAlO_(3)/RE_(2)Zr_(2)O_(7)composites is approximately 36%lower than that of RE_(2)Zr_(2)O_(7).Al–O constituents in composites can capture CaO,SiO_(2),and MgO in CMAS melts and increase their viscosity,resulting in enhanced CMAS corrosion resistance.The thermophysical properties of the REAlO_(3)/RE_(2)Zr_(2)O_(7)composites were also investigated,and their coefficient of thermal expansion and thermal conductivity are comparable to those of 7–8 wt%Y_(2)O_(3)partially stabilized ZrO2(YSZ),indicating their potential as TBC materials.
文摘CE （=%C＋（1/3）x（%Si）） does not suit experiment results in many cases. In this work, the effect of alloy elements on primary crystal temperature was measured and the relationship between primary crystal temperature （Tc） and carbon equivalent （CEL） was investigated. The results show that Tc （Celsius degree） = 1650-110 × （%C） -25 × （%Si）＋3 × （%Mn） -35 × （%P） -71 × （%5）-2 × （%Ni） -7 × （%Cr）; CEL=%C ＋ 0.23×（%Si）-0.03× （%Mn）＋0.32×（%P）＋0.64×（%S） ＋0.02×（%Ni）＋0.06×（%Cr）. That is, in hypo eutectic composition, carbon equivalent should be calculated with CEL=%C＋ 0.23×（%Si）, not with CE=%C＋（1/3） x（%Si）.
基金the National Natural ScienceFoundation of China (No. 50102004)the Aeronau-tical Science Foundation of China (No. 04G53048)+3 种基金the Development Program for Outstanding Persons in NPUand the Science Plane Project of Xi an University of Architecture and Technology (projects for talent personsRC0907)the fund of the stale Key Laboratory of Solidifi-cation Processing in NWPU (SKLSP200904)the Education Commission of Shanxi Province of China (095K511)the Doctoral fund of Ministry of Education of China(20096120120017) for financial support
文摘The Si-TaSi2 eutectic in situ composite, which has highly-aligned and uniformly-distributed TaSi2 fibers in the Si matrix, can be obtained when the solidification rate changes from 0.3 to 9.0 mm/min. It is very interesting that one or two TaSi2 fibers are curved when the solidification rate reaches 6.0 mm/min, although it is very brittle in general. The formation mechanism of the curved fiber is discussed and mechanical properties of the TaSi2 fibers are examined by nanoindentation. It is found that the hardness and the elastic modulus of the bended TaSi2 fiber are much higher than that of the straight TaSi2 fiber. Moreover, the reasons why the mechanical properties of the straight TaSi2 fiber are different from that of the curved TaSi2 fiber are discussed. This can be ascribed to internal stress which results from mismatch of the thermal expansion coefficients of the two phases and different crystallographic orientations.
基金supported by the City University of Hong Kong through the UGC Block Grant with the Project(Grant No.9610366)
文摘Eutectic and near-eutectic high entropy alloys （HEAs） have recently attracted a great deal of interest because of their promising properties, such as an excellent castability and unique combination of good ductility and high strength. However, in the absence of a phase diagram, it remains a non-trivial task to find a eutectic or near-eutectic composition for a HEA system, which usually demands a tremendous amount of efforts if a trial-and-error approach is followed. In this paper, we briefly review the thermodynamics that governs the entectic solidification in regular binary and ternary alloys, and proceed to the discussion for the design of eutectic HEAs. Based on the data reported, we then propose an improved strategy which may enable an efficient search for the eutectic or near eutectic HEA compositions.
基金This work was supported by the International Cooperation Projects of Sichuan Provincial Department of Science and Technology(No.2021YFH0126)Quzhou Science and Technology Bureau Project(No.2021D006)+2 种基金the Fundamental Research Funds for the Central Universities(No.A030202063008029)The China Postdoctoral Science Foundation(Nos.2021T140433,2020M683408)the Natural Science Foundation of Shaanxi Province(No.2021JQ-538).
文摘Polymer-based solid electrolytes have been extensively studied for solid-state lithium metal batteries to achieve high energy density and reliable security.But,its practical application is severely limited by low ionic conductivity and slow Li+transference.Herein,based on the“binary electrolytes”of poly(vinylidene fluoride-chlorotrifluoroethylene)(P(VDF-CTFE))and lithium salt(LiTFSI),a kind of eutectogel hybrid electrolytes(EHEs)with high Li+transference number was developed via tuning the spontaneous coupling of charge and vacated space generated by Li-cation diffusion utilizing the Li6.4La3Zr1.4Ta0.6O12(LLZTO)dopant.LLZTO doping promotes the dissociation of lithium salt,increases Li+carrier density,and boosts ion jumping and the coordination/decoupling reactions of Li+.As a result,the optimized EHEs-10%possess a high Li-transference number of 0.86 and a high Li+conductivity of 3.2×10–4 S·cm–1 at room temperature.Moreover,the prepared EHEs-10%composite solid electrolyte presents excellent lithiumphilic and compatibility,and can be tested stably for 1,200 h at 0.3 mA·cm–2 with assembled lithium symmetric batteries.Likewise,the EHEs-10%films match well with high-loading LiFePO4 and LiCoO2 cathodes(>10 mg·cm–2)and exhibit remarkable interface stability.Particularly,the LiFePO4//EHEs-10%//Li and LiCoO2//EHEs-10%//Li cells deliver high rate performance of 118 mAh·g–1 at 1 C and 93.7 mAh·g–1 at 2 C with coulombic efficiency of 99.3%and 98.1%,respectively.This work provides an in-depth understanding and new insights into our design for polymer electrolytes with fast Li+diffusion.
