A357-SiCp/A357 layered composites were prepared using a semi-solid vacuum stirring suction casting method.The microstructures,mechanical properties,and thermal conductivities of the composites fabricated under differe...A357-SiCp/A357 layered composites were prepared using a semi-solid vacuum stirring suction casting method.The microstructures,mechanical properties,and thermal conductivities of the composites fabricated under different suction casting processes were compared.Additionally,the microstructural evolution characteristics and performance enhancement mechanism of the A357-SiCp/A357 layered composites were discussed.The results demonstrate that suction casting at 610°C with a low solid phase ratio can significantly enhance the material density and reduce the agglomeration of SiCp.The A357-SiC_(p)/A357 interface is clear and straight with good bonding.With an increase in the suction casting temperature,the bending resistance and thermal conductivity of the A357-SiC_(p)/A357 layered composites exhibit a trend of significantly increase at first and then slowly decrease owing to casting defects,interface bonding,and SiCp distribution.Compared with SiCp/A357 composites,the bending strength,deflection,and thermal conductivity of the A357-SiCp/A357 layered composites increase from 257 MPa,1.07 mm,and 155.72 W·(m·K)^(-1) to 298 MPa,2.1 mm,and 169.86 W·(m·K)^(-1),respectively.This study provides a reference for improving the rheological casting of aluminum matrix layered composites.展开更多
It has always been challenging work to reconcile the contradiction between the strength and plasticity of titanium materials.Laser powder bed fusion(LPBF) is a convenient method to fabricate innovative composites incl...It has always been challenging work to reconcile the contradiction between the strength and plasticity of titanium materials.Laser powder bed fusion(LPBF) is a convenient method to fabricate innovative composites including those inspired by gradient layered materials.In this work,we used LPBF to selectively prepare Ti N/Ti gradient layered structure(GLSTi)composites by using different N_(2)–Ar ratios during the LPBF process.We systematically investigated the mechanisms of in-situ synthesis Ti N,high strength and ductility of GLSTi composites using microscopic analysis,TEM characterization,and tensile testing with digital image correlation.Besides,a digital correspondence was established between the N_(2) concentration and the volume fraction of LPBF in-situ synthesized Ti N.Our results show that the GLSTi composites exhibit superior mechanical properties compared to pure titanium fabricated by LPBF under pure Ar.Specifically,the tensile strength of GLSTi was more than 1.5times higher than that of LPBF-formed pure titanium,reaching up to 1100 MPa,while maintaining a high elongation at fracture of 17%.GLSTi breaks the bottleneck of high strength but low ductility exhibited by conventional nanoceramic particle-strengthened titanium matrix composites,and the hetero-deformation induced strengthening effect formed by the Ti N/Ti layered structure explained its strength-plasticity balanced principle.The microhardness exhibits a jagged variation of the relatively low hardness of 245 HV0.2 for the pure titanium layer and a high hardness of 408 HV0.2 for the N_(2) in-situ synthesis layer.Our study provides a new concept for the structure-performance digital customization of 3D-printed Ti-based composites.展开更多
Combining high conductivity,hydrophilicity and excellent electrochemical perfo rmance in one,MXe nes have attracted increasing attention since their inception.However,easy to stack caused by the van der Waals’force b...Combining high conductivity,hydrophilicity and excellent electrochemical perfo rmance in one,MXe nes have attracted increasing attention since their inception.However,easy to stack caused by the van der Waals’force between the layers limits their practical application.Fortunately,intercalating other substances between layers of MXe nes and getting intercalated MXene-based layered composites(IMLCs)with open structure can improve their physical and chemical properties effectively.Larger available surface helps expose more active sites and enlarged layer spacing facilitates ion transport.In addition,other substances fixed in the interlayers by MXenes’two-dimensional confinement effect can produce synergistic effect and expand their applicable range greatly.This review is dedicated to summarizing the preparation methods and applications of IMLCs,emphasizing the advantages of them in the fields of energy storage,catalysis,sensors,electromagnetic interference(EMI)shielding and biomedicine.Furthermore,prospects and further developments in these gratifying fields are also commented.展开更多
The effect of height on performance of the PZT/Ni cylindrical bilayered magnetoelectric (ME) com- posites was studied in situ in this paper. Multiple resonant peaks appear between 1 and 300 kHz frequency for cyl- in...The effect of height on performance of the PZT/Ni cylindrical bilayered magnetoelectric (ME) com- posites was studied in situ in this paper. Multiple resonant peaks appear between 1 and 300 kHz frequency for cyl- inders of different heights. The first resonance frequency does not change with the cylinder height decreasing, but the second and the third resonant frequencies increase. The first three resonant modes radial, first-order height are attributed to the cylinder resonance, and second-order height resonance, respectively. The appropriate size and resonance frequency were chosen to obtain the highest ME voltage coefficient when designing cylindrical bilayered magnetoelectric devices. This article provides reference to design cylindrical magnetoelectric devices.展开更多
The interaction of anti-plane elastic SH waves with a periodic array of interface cracks in a multi-layered periodic medium is analyzed in this paper. A perfect periodic structure without interface cracks is first stu...The interaction of anti-plane elastic SH waves with a periodic array of interface cracks in a multi-layered periodic medium is analyzed in this paper. A perfect periodic structure without interface cracks is first studied and the transmission displacement coefficient is obtained based on the transfer matrix method in conjunction with the Bloch-Floquet theorem. This is then generalized to a single and periodic distribution of cracks at the center interface and the result is compared with that of perfect periodic cases without interface cracks. The dependence of the transmission displacement coefficient on the frequency of the incident wave, the influences of material combination, crack configuration and incident angle are discussed in detail. Compared with the corresponding perfect periodic structure without interface cracks, a new phenomenon is found in the periodic layered system with a single and periodic array of interface cracks.展开更多
To extend the application of carbon nanotubes (CNTs) and explore novel aluminum matrix composites,CNTs were coated by molybdenum layers using metal organic chemical vapor deposition,and then Mo-coated CNT (Mo-CNT)...To extend the application of carbon nanotubes (CNTs) and explore novel aluminum matrix composites,CNTs were coated by molybdenum layers using metal organic chemical vapor deposition,and then Mo-coated CNT (Mo-CNT)/Al composites were prepared by the combination processes of powder mixing and spark plasma sintering.The influences of powder mixing and Mo-CNT content on the mechanical properties and electrical conductivity of the composites were investigated.The results show that magnetic stirring is better than mechanical milling for mixing the Mo-CNTs and Al powders.The electrical conductivity of the composites decreases with increasing Mo-CNT content.When the Mo-CNT content is 0.5wt%,the tensile strength and hardness of Mo-CNT/Al reach their maximum values.The tensile strength of 0.5wt% Mo-CNT/Al increases by 29.9%,while the electrical conductivity only decreases by 7.1%,relative to sintered pure Al.The phase analysis of Mo-CNT/Al composites reveals that there is no formation of Al carbide in the composites.展开更多
Theoretical analysis and numerical calculations of Love wave propagation in layered graded composites with imperfectly bonded interface are described in this paper. On the basis of WKB method, the approximate analytic...Theoretical analysis and numerical calculations of Love wave propagation in layered graded composites with imperfectly bonded interface are described in this paper. On the basis of WKB method, the approximate analytic solutions for Love waves are obtained. By the interface shear spring model, the dispersion relations for Love waves in layered graded composite structures with rigid, slip, and imperfectly bonded interfaces are given, and the effects of the interface conditions on the phase velocities of Love waves in SiC/Al layered graded composites are discussed. Numerical analysis shows that the phase velocity decreases when the defined flexibility parameter is greater. For the general imperfectly bonded interface, the phase velocity changes in the range of the velocities for the rigid and slip interface conditions.展开更多
The effects of a magnesium-based layered composite on the flammability of a phenolic epoxy resin(EP)are studied.In order to produce the required composite material,first,magnesium hydroxide,aluminum salt and deionized...The effects of a magnesium-based layered composite on the flammability of a phenolic epoxy resin(EP)are studied.In order to produce the required composite material,first,magnesium hydroxide,aluminum salt and deionized water are mixed into a reactor according to a certain proportion to induce a hydrothermal reaction;then,the feed liquid is filtered out using a solid-liquid separation procedure;finally,the material is dried and crushed.In order to evaluate its effects on the flammability of the EP,first,m-phenylenediamine is added to EP and vacuum defoamation is performed;then,EP is poured into a polytetrafluoroethylene mold,cooled to room temperature and demoulded;finally,the magnesium-based layered composite is added to EP,and its flame retardance is characterized by thermogravimetric analysis,limiting oxygen index and cone calorimetry.The X-ray diffraction patterns show that the baseline of magnesium-based layered composite is stable and the front shape is sharp and symmetrical when the molar ratio of magnesium to aluminium is 3.2:1;with the addition of magnesium-based layered composite,the initial pyrolysis temperature of EP of 10%,15%and 30%magnesium-based layered composite decreases to 318.2°C,317.9°C and 357.1°C,respectively.After the reaction,the amount of residual carbon increases to 0.1%,3.45%and 8.3%,and the limiting oxygen index increases by 28.3%,29.1%and 29.6%,respectively.The maximum heat release rate of cone calorimeter decreases gradually.The optimum molar ratio of Mg:Al for green synthesis is 3.2:1,and the NO_(3)-intercalated magnesium-based layered composite has the best flame retardance properties.展开更多
Large area diamond films were fabricated on copper substrates by a multi-step process comprised of electroplating Cu-diamond composite layer on Cu substrate, plating a Cu layer to fix the protruding diamond particles,...Large area diamond films were fabricated on copper substrates by a multi-step process comprised of electroplating Cu-diamond composite layer on Cu substrate, plating a Cu layer to fix the protruding diamond particles, and depositing continuous diamond film on composite interlayer by hot-filament chemical vapor deposition (HFCVD). The interface characteristics, internal stress and adhesion strength were investigated by scanning electron microscopy, Raman analysis and indentation test. The results show that the continuous film without cracks is successfully obtained. The microstructure of the film is a mixture of large cubo-octahedron grains grown from homo-epitaxial growth and small grains with (111) apparent facets grown from lateral second nuclei. The improved adhesion between diamond film and substrate results from the deep anchoring of the diamond particles in the Cu matrix and the low residual stress in the film.展开更多
A low carbon steel (LCS)/high chromium white cast iron (HCCI) bimetal wear plate about 20 mm in thickness was prepared by liquid-liquid bimetal composite casting technology to substitute for the welding wear plate...A low carbon steel (LCS)/high chromium white cast iron (HCCI) bimetal wear plate about 20 mm in thickness was prepared by liquid-liquid bimetal composite casting technology to substitute for the welding wear plate. A clear and distinguishable composite layer between the LCS and the HCCI was detected with SEM, and the composition and phase were analyzed through EDS and XRD. The composite layer was composed of three sublayers from the LCS to the HCCI: pearlite transition layer, composite layer, and HCCI transition layer. The Vickers hardness from the pearlite transition layer to the HCCl transition layer was 360 HV to 855 HV. The austenite grows as dendrites between the composite layer and the HCCI transition layer under constitutional undercooling. A large amount of C and Cr, and a small amount of Si and Mn dissolve in the matrix. Granular Cr7C3 is uniformly distributed. Due to the solute redistribution at the solid-liquid interface, the primary austenite grows from planar to cellular and finally to the distinct dendrite crystals. The dendrite crystals have an obvious growth direction perpendicular to the composite layer.展开更多
The surface infiltrated composite (Ni/WC) layers on gray iron substrate were fabricated through a vacuum infiltration casting technique (VICT) using Ni-based composite powder with different WC particles content as...The surface infiltrated composite (Ni/WC) layers on gray iron substrate were fabricated through a vacuum infiltration casting technique (VICT) using Ni-based composite powder with different WC particles content as raw materials.The microstructures of surface infiltrated composite layer,the interface structures between surface composite layer and the substrate,the changes of macro-hardness with the increasing of WC content and the micro-hardness distribution are investigated.The infiltrated composite layer includes a surface composite layer and a transition layer,and the thickness of the transition layer decreases with the increasing content of WC.The thickness of transition layer with 20%WC content in the surface infiltrated composite layer was 170 μm which was the thickest for all transition layers with different WC content.The surface composite layer was mainly composed of WC,W2C,FeB and NiB,along with Ni-Cr-Fe,Ni (Cr) solid solution,Ni (Si) solid solution and Ni (Fe) solid solution.The transition layer was composed of Ni (Cr) solid solution,Ni (Fe) solid solution,Ni (Si) solid solution,Fe (Ni) solid solution and eutectic.The surface macro-hardness and micro-hardness of the infiltrated layer had been evaluated.The macro-hardness of the surface composite layer decreases with the WC content increasing,and the average macro-hardness is HRC60.The distribution of micro-hardness presents gradient change.The average micro-hardness of the infiltrated layer is about HV1000.展开更多
The optical catastrophic damage that usually occurs at the cavity surface of semiconductor lasers has become the main bottleneck affecting the improvement of laser output power and long-term reliability.To improve the...The optical catastrophic damage that usually occurs at the cavity surface of semiconductor lasers has become the main bottleneck affecting the improvement of laser output power and long-term reliability.To improve the output power of 680 nm AlGaInP/GaInP quantum well red semiconductor lasers,Si-Si_(3)N_(4)composited dielectric layers are used to induce its quantum wells to be intermixed at the cavity surface to make a non-absorption window.Si with a thickness of 100 nm and Si_(3)N_(4)with a thickness of 100 nm were grown on the surface of the epitaxial wafer by magnetron sputtering and PECVD as diffusion source and driving source,respectively.Compared with traditional Si impurity induced quantum well intermixing,this paper realizes the blue shift of 54.8 nm in the nonabsorbent window region at a lower annealing temperature of 600 ℃ and annealing time of 10 min.Under this annealing condition,the wavelength of the gain luminescence region basically does not shift to short wavelength,and the surface morphology of the whole epitaxial wafer remains fine after annealing.The application of this process condition can reduce the difficulty of production and save cost,which provides an effective method for upcoming fabrication.展开更多
Tungsten inert gas(TIG) welding was applied to creating a composite layer on the surface of cast aluminum alloy A380. Different mixtures of Al, Si and SiC powders mixed with sodium silicate solution were pasted on s...Tungsten inert gas(TIG) welding was applied to creating a composite layer on the surface of cast aluminum alloy A380. Different mixtures of Al, Si and SiC powders mixed with sodium silicate solution were pasted on substrates. Surface melting was conducted by TIG welding to produce Al-SiC layer on the surface. Microstructural evolution was investigated by X-ray diffractometry(XRD), optical and scanning electron microscopy(SEM) and elemental microanalysis(EDS). Properties of clad layers were studied by microhardness and sliding wear testing. The results showed a uniform distribution of SiC particles in dendritic aluminum matrix. Addition of excess silicon caused the formation of eutectic crystals and coarse silicon particles in the clad layer which resulted in higher hardness and wear resistance of clad layers.展开更多
The hazard of Hg ion pollution triggers the motivation to explore a fast, sensitive, and reliable detection method. Here, we design and fabricate novel 36-nm-thick Ag-Au composite layers alternately deposited on three...The hazard of Hg ion pollution triggers the motivation to explore a fast, sensitive, and reliable detection method. Here, we design and fabricate novel 36-nm-thick Ag-Au composite layers alternately deposited on three-dimensional (3D) periodic SiO2 nanogrids as surface-enhanced Raman scattering (SERS) probes. The SERS effects of the probes depend mainly on the positions and intensities of their localized surface plasmon resonance (LSPR) peaks, which is confirmed by the absorption spectra from finite-difference time-domain (FDTD) calculations. By optimizing the structure and material to maximize the intrinsic electric field enhancement based on the design method of 3D periodic SERS probes proposed, high performance of the Ag-Au/SiO2 nanogrid probes is achieved with the stability further enhanced by annealing. The optimized probes show the outstanding stability with only 4.0% SERS intensity change during 10-day storage, the excellent detection uniformity of 5.78% (RSD), the detection limit of 5.0 × 10-12 M (1 ppt), and superior selectivity for Hg ions. The present study renders it possible to realize the rapid and reliable detection of trace heavy metal ions by developing high- performance 3D periodic structure SERS probes by designing novel 3D structure and optimizing plasmonic material.展开更多
Fe-Cr-Ni/Al-Si-Cu-Ni-Mg composite was taken as the experimental material. The chemical composition of interfacial layer was tested. The generation mechanism and influence of interfacial layer on the composite were ana...Fe-Cr-Ni/Al-Si-Cu-Ni-Mg composite was taken as the experimental material. The chemical composition of interfacial layer was tested. The generation mechanism and influence of interfacial layer on the composite were analyzed. The results indicated that the generation of interfacial layer is sensitive to temperature. Interfacial layer will generate rapidly when temperature reaches 500 ℃ or above. The interfacial layer is mainly composed of Al, Si, Cu, Fe, and Cr, element Ni distributes at the outward of the interfacial layer for the precipitate of Ni later than Si and Cu, and there is almost no diffusion of Ni during the solution treatment. During heat treatment process, unequal quantity changing of metal atom results in disperse or concentrated vacancies or holes near the matrix. The existence of interfacial layer will induce a decrease of compression strength and plasticity at room temperature and an increase of strength at higher temperature comparing with composite without interfacial layer.展开更多
In this paper, the NU308 bearing rings were subjected to strengthen grinding treatment (SGT) at ambient temperature. And the running reliabilities of specimens that subjected to SGT and conventional treatment (CT) wer...In this paper, the NU308 bearing rings were subjected to strengthen grinding treatment (SGT) at ambient temperature. And the running reliabilities of specimens that subjected to SGT and conventional treatment (CT) were respectively investigated by testing dynamic properties including the running temperature, vibrations, and surface burning. Moreover, the residual stress, microtopography, and microstructures on the cross-section were respectively tested with residual stress analyzer and field-emission scanning electron microscopy. The results showed that the running reliabilities of the specimen after SGT had been significantly improved with the reduction of running temperature, vibration, and surface burning. Further study showed that the specimen’s surface was filled with disordered micropores after SGT compared to the regular strip texture on the CT specimen’s surface, and the maximum residual compressive stress induced by SGT was about −900 MPa. Moreover, the thickness of the residual compressive stress layer was over 180 µm, while the thickness of severe plastic deformation layer was about 50 µm.展开更多
A concave die with an equal-strain contour line was used in the hydrostatic extrusion process to deform the two-layer Cu/A1 composite. The extruding process was simulated using the fi- nite element method (FEM). The...A concave die with an equal-strain contour line was used in the hydrostatic extrusion process to deform the two-layer Cu/A1 composite. The extruding process was simulated using the fi- nite element method (FEM). The effect of the friction coefficients on the relative slippage of the contact surfaces between the internal and external metals was investigated, and the stress distribu- tion in the extruded specimen was studied. The simulation results reveal that the relative slippage de- creases with increasing friction coefficient at the contact surface of the two metals. However, the relative slippage increases rapidly with increasing friction coefficient at the contact surface between the specimen and die. No axial tensile stress appears in the plastic deformation zone near the axis, indicating that the inner fracture will not occur in internal metal in the hydrostatic extrusion process as the concave die with equal-strain contour lines is used. The experimental test reveals that the met- allurgical bond is formed between Cu and A1 when the friction coefficient at the surface between the two metals is 0. 3 and the extrusion ratio is 12.展开更多
1.IntroductionMetal matrix composites consist of afamily of advanced materials which mayhave attractive properties including highstrength,high specific modulus,lowcoefficient of thermal expansion,good wearresistance,a...1.IntroductionMetal matrix composites consist of afamily of advanced materials which mayhave attractive properties including highstrength,high specific modulus,lowcoefficient of thermal expansion,good wearresistance,and attractive high temperature展开更多
The nature of the native oxides formed on the surface layer of amorphous alloy Ni_(64)P_(20)Fe_(16)has been studied by X-ray photoelectron spectroscopy (XPS)and Auger electron spectroscopy(AES)with depth profiling by ...The nature of the native oxides formed on the surface layer of amorphous alloy Ni_(64)P_(20)Fe_(16)has been studied by X-ray photoelectron spectroscopy (XPS)and Auger electron spectroscopy(AES)with depth profiling by ion bombardment.There are great distinctions in compositions and chemical states between the surface layer and the bulk.The main constituents Ni,P and Fe are lower in the sur- face layer,and they are mostly in oxidized states, whereas C,O and N are enriched in the surface lay- er.The thickness of surface oxide layer is approximately 20 nm,this layer was assumed to be of great significance to various properties of amor- phous alloy Ni_(64)P_(20)Fe_(16),expecially to the chemical and catalytic properties.Experiments proved that transitional element Fe cannot improve oxidation resistance of the amorphous Ni-P system.展开更多
[FeNi(3 nm)/Zn1-xCoxO(3 nm)]2/ZnO(d nm)/[Zn1-xCoxO(3 nm)/Co(3 nm)]2 (d=3 and 10) semiconductor junctions were prepared by magnetron sputtering system and photolithography. The spin valve effect was observe...[FeNi(3 nm)/Zn1-xCoxO(3 nm)]2/ZnO(d nm)/[Zn1-xCoxO(3 nm)/Co(3 nm)]2 (d=3 and 10) semiconductor junctions were prepared by magnetron sputtering system and photolithography. The spin valve effect was observed in these junctions because the utility of the ferromagnetic composite layers acted as soft and hard magnetic layers. The electrical detection was performed by measuring the magnetoresistance of these junctions to investigate the current spin polarization asc in the ZnO layer and the spin injection efficiency η of spin-polarized electrons. asc was reduced from 11.7% (and 10.5%) at 90 K to 7.31% (and 5.93%) at room temperature for d=3 (and d=10). And η was reduced from 39.5% (and 35.5%) at 90 K to 24.7% (and 20.0%) at room temperature for d=3 (and d=10).展开更多
文摘A357-SiCp/A357 layered composites were prepared using a semi-solid vacuum stirring suction casting method.The microstructures,mechanical properties,and thermal conductivities of the composites fabricated under different suction casting processes were compared.Additionally,the microstructural evolution characteristics and performance enhancement mechanism of the A357-SiCp/A357 layered composites were discussed.The results demonstrate that suction casting at 610°C with a low solid phase ratio can significantly enhance the material density and reduce the agglomeration of SiCp.The A357-SiC_(p)/A357 interface is clear and straight with good bonding.With an increase in the suction casting temperature,the bending resistance and thermal conductivity of the A357-SiC_(p)/A357 layered composites exhibit a trend of significantly increase at first and then slowly decrease owing to casting defects,interface bonding,and SiCp distribution.Compared with SiCp/A357 composites,the bending strength,deflection,and thermal conductivity of the A357-SiCp/A357 layered composites increase from 257 MPa,1.07 mm,and 155.72 W·(m·K)^(-1) to 298 MPa,2.1 mm,and 169.86 W·(m·K)^(-1),respectively.This study provides a reference for improving the rheological casting of aluminum matrix layered composites.
基金supported by the Guangdong Basic and Applied Basic Research Foundation (2020B1515120013,2022B1515120066)National Natural Science Foundation of China (Nos.U2001218, 51875215)+1 种基金Key-Area Research and Development Program of Guangdong Province (2020B090923001)Special Support Foundation of Guangdong Province (No.2019TQ05Z110)。
文摘It has always been challenging work to reconcile the contradiction between the strength and plasticity of titanium materials.Laser powder bed fusion(LPBF) is a convenient method to fabricate innovative composites including those inspired by gradient layered materials.In this work,we used LPBF to selectively prepare Ti N/Ti gradient layered structure(GLSTi)composites by using different N_(2)–Ar ratios during the LPBF process.We systematically investigated the mechanisms of in-situ synthesis Ti N,high strength and ductility of GLSTi composites using microscopic analysis,TEM characterization,and tensile testing with digital image correlation.Besides,a digital correspondence was established between the N_(2) concentration and the volume fraction of LPBF in-situ synthesized Ti N.Our results show that the GLSTi composites exhibit superior mechanical properties compared to pure titanium fabricated by LPBF under pure Ar.Specifically,the tensile strength of GLSTi was more than 1.5times higher than that of LPBF-formed pure titanium,reaching up to 1100 MPa,while maintaining a high elongation at fracture of 17%.GLSTi breaks the bottleneck of high strength but low ductility exhibited by conventional nanoceramic particle-strengthened titanium matrix composites,and the hetero-deformation induced strengthening effect formed by the Ti N/Ti layered structure explained its strength-plasticity balanced principle.The microhardness exhibits a jagged variation of the relatively low hardness of 245 HV0.2 for the pure titanium layer and a high hardness of 408 HV0.2 for the N_(2) in-situ synthesis layer.Our study provides a new concept for the structure-performance digital customization of 3D-printed Ti-based composites.
基金supported by the National Natural Science Foundation of China(Nos.21776061,21978069,21707081 and 41807128)the program for Science&Technology Innovation Team in Universities of Henan Province(No.19IRTSTHN029)。
文摘Combining high conductivity,hydrophilicity and excellent electrochemical perfo rmance in one,MXe nes have attracted increasing attention since their inception.However,easy to stack caused by the van der Waals’force between the layers limits their practical application.Fortunately,intercalating other substances between layers of MXe nes and getting intercalated MXene-based layered composites(IMLCs)with open structure can improve their physical and chemical properties effectively.Larger available surface helps expose more active sites and enlarged layer spacing facilitates ion transport.In addition,other substances fixed in the interlayers by MXenes’two-dimensional confinement effect can produce synergistic effect and expand their applicable range greatly.This review is dedicated to summarizing the preparation methods and applications of IMLCs,emphasizing the advantages of them in the fields of energy storage,catalysis,sensors,electromagnetic interference(EMI)shielding and biomedicine.Furthermore,prospects and further developments in these gratifying fields are also commented.
基金supported by the Beijing Nova Program(No.Z141103001814006)the National Key Technology R&D Program(Nos.2012BAC12B05 and 2012BAC02B01)+1 种基金the National Natural Science Foundation of China(Nos.51174247 and U1360202)the National High-Tech Research and the Development Program of China(No.2012AA063202)
文摘The effect of height on performance of the PZT/Ni cylindrical bilayered magnetoelectric (ME) com- posites was studied in situ in this paper. Multiple resonant peaks appear between 1 and 300 kHz frequency for cyl- inders of different heights. The first resonance frequency does not change with the cylinder height decreasing, but the second and the third resonant frequencies increase. The first three resonant modes radial, first-order height are attributed to the cylinder resonance, and second-order height resonance, respectively. The appropriate size and resonance frequency were chosen to obtain the highest ME voltage coefficient when designing cylindrical bilayered magnetoelectric devices. This article provides reference to design cylindrical magnetoelectric devices.
基金supported by the National Natural Science Foundation of China(Nos.11002026 and 11372039)Beijing Natural Science Foundation(No.3133039)the Scientific Research Foundation for the Returned(No.20121832001)
文摘The interaction of anti-plane elastic SH waves with a periodic array of interface cracks in a multi-layered periodic medium is analyzed in this paper. A perfect periodic structure without interface cracks is first studied and the transmission displacement coefficient is obtained based on the transfer matrix method in conjunction with the Bloch-Floquet theorem. This is then generalized to a single and periodic distribution of cracks at the center interface and the result is compared with that of perfect periodic cases without interface cracks. The dependence of the transmission displacement coefficient on the frequency of the incident wave, the influences of material combination, crack configuration and incident angle are discussed in detail. Compared with the corresponding perfect periodic structure without interface cracks, a new phenomenon is found in the periodic layered system with a single and periodic array of interface cracks.
基金supported by the National High-Tech Research and Development Program of China (No.2009AA03Z116)the National Natural Science Foundation of China (No.50971020)
文摘To extend the application of carbon nanotubes (CNTs) and explore novel aluminum matrix composites,CNTs were coated by molybdenum layers using metal organic chemical vapor deposition,and then Mo-coated CNT (Mo-CNT)/Al composites were prepared by the combination processes of powder mixing and spark plasma sintering.The influences of powder mixing and Mo-CNT content on the mechanical properties and electrical conductivity of the composites were investigated.The results show that magnetic stirring is better than mechanical milling for mixing the Mo-CNTs and Al powders.The electrical conductivity of the composites decreases with increasing Mo-CNT content.When the Mo-CNT content is 0.5wt%,the tensile strength and hardness of Mo-CNT/Al reach their maximum values.The tensile strength of 0.5wt% Mo-CNT/Al increases by 29.9%,while the electrical conductivity only decreases by 7.1%,relative to sintered pure Al.The phase analysis of Mo-CNT/Al composites reveals that there is no formation of Al carbide in the composites.
基金Engineering Research Institute of Peking University (ERIPKU) Joint Building Project of Beijing Education Committee
文摘Theoretical analysis and numerical calculations of Love wave propagation in layered graded composites with imperfectly bonded interface are described in this paper. On the basis of WKB method, the approximate analytic solutions for Love waves are obtained. By the interface shear spring model, the dispersion relations for Love waves in layered graded composite structures with rigid, slip, and imperfectly bonded interfaces are given, and the effects of the interface conditions on the phase velocities of Love waves in SiC/Al layered graded composites are discussed. Numerical analysis shows that the phase velocity decreases when the defined flexibility parameter is greater. For the general imperfectly bonded interface, the phase velocity changes in the range of the velocities for the rigid and slip interface conditions.
文摘The effects of a magnesium-based layered composite on the flammability of a phenolic epoxy resin(EP)are studied.In order to produce the required composite material,first,magnesium hydroxide,aluminum salt and deionized water are mixed into a reactor according to a certain proportion to induce a hydrothermal reaction;then,the feed liquid is filtered out using a solid-liquid separation procedure;finally,the material is dried and crushed.In order to evaluate its effects on the flammability of the EP,first,m-phenylenediamine is added to EP and vacuum defoamation is performed;then,EP is poured into a polytetrafluoroethylene mold,cooled to room temperature and demoulded;finally,the magnesium-based layered composite is added to EP,and its flame retardance is characterized by thermogravimetric analysis,limiting oxygen index and cone calorimetry.The X-ray diffraction patterns show that the baseline of magnesium-based layered composite is stable and the front shape is sharp and symmetrical when the molar ratio of magnesium to aluminium is 3.2:1;with the addition of magnesium-based layered composite,the initial pyrolysis temperature of EP of 10%,15%and 30%magnesium-based layered composite decreases to 318.2°C,317.9°C and 357.1°C,respectively.After the reaction,the amount of residual carbon increases to 0.1%,3.45%and 8.3%,and the limiting oxygen index increases by 28.3%,29.1%and 29.6%,respectively.The maximum heat release rate of cone calorimeter decreases gradually.The optimum molar ratio of Mg:Al for green synthesis is 3.2:1,and the NO_(3)-intercalated magnesium-based layered composite has the best flame retardance properties.
基金Projects(51071070,51271079)supported by the National Natural Science Foundation of ChinaProject(NCET-11-0156)supported by New Century Excellent Talents in University,China
文摘Large area diamond films were fabricated on copper substrates by a multi-step process comprised of electroplating Cu-diamond composite layer on Cu substrate, plating a Cu layer to fix the protruding diamond particles, and depositing continuous diamond film on composite interlayer by hot-filament chemical vapor deposition (HFCVD). The interface characteristics, internal stress and adhesion strength were investigated by scanning electron microscopy, Raman analysis and indentation test. The results show that the continuous film without cracks is successfully obtained. The microstructure of the film is a mixture of large cubo-octahedron grains grown from homo-epitaxial growth and small grains with (111) apparent facets grown from lateral second nuclei. The improved adhesion between diamond film and substrate results from the deep anchoring of the diamond particles in the Cu matrix and the low residual stress in the film.
基金financially supported by the National Natural Science Foundation of China Project under grant No.51371090the Science and Technology Support Program of 12th Five-Year Plan under grant No.2011BAD20B03010401+4 种基金the Educational Department Surface Project of Heilongjiang Province under grant No.12521519the Cultivation Plan of the New Century Excellent Talents of Heilongjiang Province under grant No.1155-NCET-017the College Student Science and Technology Innovation of Heilongjiang Province under grant No.201410222037the College Student Science and Technology Innovation of Jiamusi University under grant No.xsld2014-002Graduate Student Science and Technology Innovation of Jiamusi University LZR2014_007
文摘A low carbon steel (LCS)/high chromium white cast iron (HCCI) bimetal wear plate about 20 mm in thickness was prepared by liquid-liquid bimetal composite casting technology to substitute for the welding wear plate. A clear and distinguishable composite layer between the LCS and the HCCI was detected with SEM, and the composition and phase were analyzed through EDS and XRD. The composite layer was composed of three sublayers from the LCS to the HCCI: pearlite transition layer, composite layer, and HCCI transition layer. The Vickers hardness from the pearlite transition layer to the HCCl transition layer was 360 HV to 855 HV. The austenite grows as dendrites between the composite layer and the HCCI transition layer under constitutional undercooling. A large amount of C and Cr, and a small amount of Si and Mn dissolve in the matrix. Granular Cr7C3 is uniformly distributed. Due to the solute redistribution at the solid-liquid interface, the primary austenite grows from planar to cellular and finally to the distinct dendrite crystals. The dendrite crystals have an obvious growth direction perpendicular to the composite layer.
基金Funded by"Xi-Bu-Zhi-Guang" Foundation of Chinese Academy of Sciences(No.XBZG-2007-5)Gansu Natural Science Foundation of China(No.0806RJYA004)Outstanding Youngth of Lanzhou University of Technology (No.Q200910)
文摘The surface infiltrated composite (Ni/WC) layers on gray iron substrate were fabricated through a vacuum infiltration casting technique (VICT) using Ni-based composite powder with different WC particles content as raw materials.The microstructures of surface infiltrated composite layer,the interface structures between surface composite layer and the substrate,the changes of macro-hardness with the increasing of WC content and the micro-hardness distribution are investigated.The infiltrated composite layer includes a surface composite layer and a transition layer,and the thickness of the transition layer decreases with the increasing content of WC.The thickness of transition layer with 20%WC content in the surface infiltrated composite layer was 170 μm which was the thickest for all transition layers with different WC content.The surface composite layer was mainly composed of WC,W2C,FeB and NiB,along with Ni-Cr-Fe,Ni (Cr) solid solution,Ni (Si) solid solution and Ni (Fe) solid solution.The transition layer was composed of Ni (Cr) solid solution,Ni (Fe) solid solution,Ni (Si) solid solution,Fe (Ni) solid solution and eutectic.The surface macro-hardness and micro-hardness of the infiltrated layer had been evaluated.The macro-hardness of the surface composite layer decreases with the WC content increasing,and the average macro-hardness is HRC60.The distribution of micro-hardness presents gradient change.The average micro-hardness of the infiltrated layer is about HV1000.
基金supported by the National Natural Science Foundation of China(NNSFC)(Grant No.62174154).
文摘The optical catastrophic damage that usually occurs at the cavity surface of semiconductor lasers has become the main bottleneck affecting the improvement of laser output power and long-term reliability.To improve the output power of 680 nm AlGaInP/GaInP quantum well red semiconductor lasers,Si-Si_(3)N_(4)composited dielectric layers are used to induce its quantum wells to be intermixed at the cavity surface to make a non-absorption window.Si with a thickness of 100 nm and Si_(3)N_(4)with a thickness of 100 nm were grown on the surface of the epitaxial wafer by magnetron sputtering and PECVD as diffusion source and driving source,respectively.Compared with traditional Si impurity induced quantum well intermixing,this paper realizes the blue shift of 54.8 nm in the nonabsorbent window region at a lower annealing temperature of 600 ℃ and annealing time of 10 min.Under this annealing condition,the wavelength of the gain luminescence region basically does not shift to short wavelength,and the surface morphology of the whole epitaxial wafer remains fine after annealing.The application of this process condition can reduce the difficulty of production and save cost,which provides an effective method for upcoming fabrication.
文摘Tungsten inert gas(TIG) welding was applied to creating a composite layer on the surface of cast aluminum alloy A380. Different mixtures of Al, Si and SiC powders mixed with sodium silicate solution were pasted on substrates. Surface melting was conducted by TIG welding to produce Al-SiC layer on the surface. Microstructural evolution was investigated by X-ray diffractometry(XRD), optical and scanning electron microscopy(SEM) and elemental microanalysis(EDS). Properties of clad layers were studied by microhardness and sliding wear testing. The results showed a uniform distribution of SiC particles in dendritic aluminum matrix. Addition of excess silicon caused the formation of eutectic crystals and coarse silicon particles in the clad layer which resulted in higher hardness and wear resistance of clad layers.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0207104)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA09040101)+2 种基金the National Natural Science Foundation of China(Grant No.Y6061111JJ)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2015030)the Key Technology Talent Program of Chinese Academy of Sciences(Grant Nos.Y8482911ZX and Y7602921ZX)
文摘The hazard of Hg ion pollution triggers the motivation to explore a fast, sensitive, and reliable detection method. Here, we design and fabricate novel 36-nm-thick Ag-Au composite layers alternately deposited on three-dimensional (3D) periodic SiO2 nanogrids as surface-enhanced Raman scattering (SERS) probes. The SERS effects of the probes depend mainly on the positions and intensities of their localized surface plasmon resonance (LSPR) peaks, which is confirmed by the absorption spectra from finite-difference time-domain (FDTD) calculations. By optimizing the structure and material to maximize the intrinsic electric field enhancement based on the design method of 3D periodic SERS probes proposed, high performance of the Ag-Au/SiO2 nanogrid probes is achieved with the stability further enhanced by annealing. The optimized probes show the outstanding stability with only 4.0% SERS intensity change during 10-day storage, the excellent detection uniformity of 5.78% (RSD), the detection limit of 5.0 × 10-12 M (1 ppt), and superior selectivity for Hg ions. The present study renders it possible to realize the rapid and reliable detection of trace heavy metal ions by developing high- performance 3D periodic structure SERS probes by designing novel 3D structure and optimizing plasmonic material.
基金Funded by the Program of International S&T Cooperation(No.2013DFA51230)the Opening Subject Fund of Ningbo University(No.zj1226)
文摘Fe-Cr-Ni/Al-Si-Cu-Ni-Mg composite was taken as the experimental material. The chemical composition of interfacial layer was tested. The generation mechanism and influence of interfacial layer on the composite were analyzed. The results indicated that the generation of interfacial layer is sensitive to temperature. Interfacial layer will generate rapidly when temperature reaches 500 ℃ or above. The interfacial layer is mainly composed of Al, Si, Cu, Fe, and Cr, element Ni distributes at the outward of the interfacial layer for the precipitate of Ni later than Si and Cu, and there is almost no diffusion of Ni during the solution treatment. During heat treatment process, unequal quantity changing of metal atom results in disperse or concentrated vacancies or holes near the matrix. The existence of interfacial layer will induce a decrease of compression strength and plasticity at room temperature and an increase of strength at higher temperature comparing with composite without interfacial layer.
文摘In this paper, the NU308 bearing rings were subjected to strengthen grinding treatment (SGT) at ambient temperature. And the running reliabilities of specimens that subjected to SGT and conventional treatment (CT) were respectively investigated by testing dynamic properties including the running temperature, vibrations, and surface burning. Moreover, the residual stress, microtopography, and microstructures on the cross-section were respectively tested with residual stress analyzer and field-emission scanning electron microscopy. The results showed that the running reliabilities of the specimen after SGT had been significantly improved with the reduction of running temperature, vibration, and surface burning. Further study showed that the specimen’s surface was filled with disordered micropores after SGT compared to the regular strip texture on the CT specimen’s surface, and the maximum residual compressive stress induced by SGT was about −900 MPa. Moreover, the thickness of the residual compressive stress layer was over 180 µm, while the thickness of severe plastic deformation layer was about 50 µm.
基金Supported by the National Basic Research Program of China("973" Program)(613135)
文摘A concave die with an equal-strain contour line was used in the hydrostatic extrusion process to deform the two-layer Cu/A1 composite. The extruding process was simulated using the fi- nite element method (FEM). The effect of the friction coefficients on the relative slippage of the contact surfaces between the internal and external metals was investigated, and the stress distribu- tion in the extruded specimen was studied. The simulation results reveal that the relative slippage de- creases with increasing friction coefficient at the contact surface of the two metals. However, the relative slippage increases rapidly with increasing friction coefficient at the contact surface between the specimen and die. No axial tensile stress appears in the plastic deformation zone near the axis, indicating that the inner fracture will not occur in internal metal in the hydrostatic extrusion process as the concave die with equal-strain contour lines is used. The experimental test reveals that the met- allurgical bond is formed between Cu and A1 when the friction coefficient at the surface between the two metals is 0. 3 and the extrusion ratio is 12.
文摘1.IntroductionMetal matrix composites consist of afamily of advanced materials which mayhave attractive properties including highstrength,high specific modulus,lowcoefficient of thermal expansion,good wearresistance,and attractive high temperature
文摘The nature of the native oxides formed on the surface layer of amorphous alloy Ni_(64)P_(20)Fe_(16)has been studied by X-ray photoelectron spectroscopy (XPS)and Auger electron spectroscopy(AES)with depth profiling by ion bombardment.There are great distinctions in compositions and chemical states between the surface layer and the bulk.The main constituents Ni,P and Fe are lower in the sur- face layer,and they are mostly in oxidized states, whereas C,O and N are enriched in the surface lay- er.The thickness of surface oxide layer is approximately 20 nm,this layer was assumed to be of great significance to various properties of amor- phous alloy Ni_(64)P_(20)Fe_(16),expecially to the chemical and catalytic properties.Experiments proved that transitional element Fe cannot improve oxidation resistance of the amorphous Ni-P system.
基金supported by the State Key Project of Fundamental Research of China No.2007CB924903 and NSFC No.50572053
文摘[FeNi(3 nm)/Zn1-xCoxO(3 nm)]2/ZnO(d nm)/[Zn1-xCoxO(3 nm)/Co(3 nm)]2 (d=3 and 10) semiconductor junctions were prepared by magnetron sputtering system and photolithography. The spin valve effect was observed in these junctions because the utility of the ferromagnetic composite layers acted as soft and hard magnetic layers. The electrical detection was performed by measuring the magnetoresistance of these junctions to investigate the current spin polarization asc in the ZnO layer and the spin injection efficiency η of spin-polarized electrons. asc was reduced from 11.7% (and 10.5%) at 90 K to 7.31% (and 5.93%) at room temperature for d=3 (and d=10). And η was reduced from 39.5% (and 35.5%) at 90 K to 24.7% (and 20.0%) at room temperature for d=3 (and d=10).