Interfacial Transition Layer Research Articles

The evolution of resistive switching behaviors dependent on interface transition layers in Cu/Al/FTO nanostructure

Here, the Cu/Al/FTO layered nanostructure was designed and manufactured for investigating the roles of the interface transition layers in its resistive switching (RS) behaviors. The presence of the interface transition layers was confirmed by X-ray photoelectron spectroscopy (XPS) depth profile scans, indeed there is a very thin Al2O3 interface transition layer (interface 1, denoted as I1) produced by the natural oxidation within the Cu/Al interfaces, and a thicker interface transition layer (interface 2, denoted as I2, consisting of Al, Al2O3, SnO and SnO2) generated by interdiffusion and redox reaction between the Al/FTO interfaces. The test results showed that the device, with actual structure of Cu/I1/Al/I2/FTO, could show the evolution of resistive switching behaviors: from irreversible write-once-read-many-times (WORM) characteristics to reversible bipolar resistive switching (BRS) behaviors with negative differential resistance (NDR) effect and subsequent disappearance and recovery of the BRS. Correlation analysis suggests the observed RS behaviors strongly depend on the permanent rupture of pre-existing Al conductive filaments (Al-CFs) in the transition layer I2, and their evolution. This work gives an insight into the role of interface transition layers in RS behaviors and provides a simple way to design and build new sandwiched nanostructure using for nonvolatile memory.

Phthalocyanine nanowires@GO/carbon fiber composites with enhanced interfacial properties and electromagnetic interference shielding performance

In this study, we describe the preparation of a hierarchical nanostructure consisting of tetraamino-phthalocyanine nanowires (TAPc NWs) decorated on graphene oxide (GO) supported on carbon fibers (CF-TAPc NWs@GO) through one-pot method of solvent-evaporation and self-assemble. The morphology and chemical composition of various CFs are investigated. The X-ray diffraction and UV–vis spectroscopy demonstrate the formation of α-phase TAPc NWs is induced with J-aggregation, and the possible assembly mechanism is presented. The adhesive forces between the CFs and TAPc molecules are quantitatively characterized by atomic force microscopy (AFM) with peak force quantitative nanomechanical mapping (PF-QNM) mode, explaining the reason of TAPc NWs preferentially grown on the GO sheets. Moreover, the decreased contact angle and increased surface energy promote the impregnating of the matrix onto the CFs surface to improve the wettability. The interfacial shear strength of CF-TAPc NWs@GO composite is remarkably enhanced by 66.9% at 30 °C and 206.6% at 180 °C compared with untreated CF, which could be ascribed to its hierarchical nanostructure and increased active groups. The interfacial failure mechanisms are discussed by PF-QNM of AFM, which demonstrate that the interfacial transition layer has been established by the hierarchical structure of TAPc NWs@GO and act as a buffer to transfer stress, resulting in the cohesive failure. Additionally, the multiple interfacial polarization and conductive loss from the hierarchically structure of TAPc NWs@GO are highly efficient in endowing CF composite with a satisfactory electromagnetic interference (EMI)-shielding effectiveness of 29 dB in the X-band at a low CF-TAPc NWs@GO content of 0.5 wt%, which is enhanced 108.3% compared with untreated CF. The prepared CF-TAPc NWs@GO/EP composite shows great potential in aerospace and EMI applications.

Superior and versatile interface transition layer with a sandwich-like multiscale rigid-soft dual-locked structure for high performance composites

In order to integrate eco-friendly, flexible and versatile purpose into interphase design strategy, a multiscale rigid-soft dual-locked interface layer with sandwich structure was designed and fabricated to modify the interface between carbon fibers (CFs) and matrix by a facile and green method, with water as the only solvent. Polydopamine (PDA) was chosen as a functional platform to introduce Ni(OH)2 nanosheets self-assembling onto the CFs surface. After incorporation with a soft and amine-rich polymer, a steadier and more entangled dual-locked interface layer could be realized. The interlaminar shear strength (ILSS) results indicated that the ILSS improved up to 43.38%, compared with untreated CFs composites, the flexural properties represented a dramatic breakthrough, indicating the superiority of this interfacial network. Interestingly, this design strategy could be extended to other system due to the versatile characteristic of PDA and cater different application fields by varying functional nanoparticles.

Conservative Allen–Cahn equation with a nonstandard variable mobility

In this article, we present the conservative Allen–Cahn equation with a nonstandard variable mobility. Unlike the classical variable mobility, the proposed nonstandard variable mobility has small value at the interface and large value away from the interface. As benchmark tests, we perform temporal evolutions of two droplets without velocity field, 2D droplet deformation under a simple shear flow, 2D droplet deformation under a swirling flow, and 3D droplet deformation under a shear flow. The numerical results of the proposed method demonstrate a remarkable accuracy in preserving interfaces. Moreover, the proposed method not only captures interface location but also maintains uniform interface transition layer thickness.

Interfacial Bonding and Abrasive Wear Behavior of Iron Matrix Composite Reinforced by Ceramic Particles.

Using zirconia toughened alumina (ZTA) particles and Ni–Ti complex powders as raw materials, high-Cr cast iron reinforced by ZTA particles was prepared by an infiltration casting process. A continuous transition layer formed at the interface between ZTA particles and the Cr15 matrix, which proves that there is strong metallurgical interfacial bonding at the interface. The phases in the Ni–Ti layer of the ZTAP/Fe composite were preserved compared with the microstructure of sintered ZTA ceramic preform. The hardness of the Ni3Ti, TiO and AlNi2Ti phases in the interfacial transition layer was measured by the nano-indentation method, which is 12.5 GPa, 16.1 GPa and 9.2 GPa, respectively. The three-body wear resistance of the composite reached 12.6 times that of high-Cr cast iron.

Novel approach for fabrication and characterisation of porosity-graded material

ABSTRACTA novel continuously graded material that is based on a porosity-graded structure was successfully synthesised via a cold pressing-vacuum sintering-dissolution process (SDP) of powder metallurgy technology. Microscopic observations and the Archimedes method were used to confirm the newly synthesised porosity-graded material, the mechanical properties and the modulus. The results show that the density continuously increased from 1.4 to 2.7 g cm−3, and there was no obvious interfacial transition layer. In addition, the hardness and elastic modulus were obtained from nanoindentation tests and display a stepwise feature along the gradient direction. Moreover, we found that the fractography changes from typical ductile fracture to ductile and cleavage fracture with an increase in the porosity.HighlightsA porosity graded material has been successfully synthesised by powder metallurgy.The density continuously transit from 1.4 to 2.7 g cm−3, and it has no obvious interfacial transition layer.The stepwise feature of density and modulus shows great potential in the shields of spacecrafts.

Effect of coatings on thermal conductivity and tribological properties of aluminum foam/polyoxymethylene interpenetrating composites

The purpose of this work is to solve the problem of interface bonding in aluminum foam (AF)/polyoxymethylene (POM) interpenetrating phase composites (AF/POM). Silane coupling agent (KH-550), graphene oxide (GO), sulfonated graphene (S-GNS) and graphene (GS) coatings were prepared on the surface of AF, respectively, as an interfacial transition layer. The molten modified POM(POMC) was injected into the hole of coated AF by injection molding to prepare different kinds of coated AF/POMC. Thermal conductivity, friction coefficient and wear loss of coated AF/POMC were analyzed, and the wear mechanisms were discussed in detail based on evidences from SEM. The effect of coatings on thermal conductivity of coated AF/POMC was also verified by ANSYS. The investigation has shown that four kinds of coating are successfully covered on the surface of AF, respectively, and the morphology of S-GNS coating is the smoothest. The thermal conductivity of coated AF/POMC is higher than that of AF/POMC. The thermal conductivity of S-GNS-AF/POMC reaches the highest value of 2.25 W m−1 K−1, because S-GNS coating plays a role in reducing the thermal resistance of the interface between AF and POMC phases. The friction coefficient and wear loss of coated AF/POMC are also lower than that of AF/POMC. Three types of graphene coating(S-GNS,GO,GS) as an interface transition layer between AF and POMC phases can homogenize friction, accelerate heat transfer and reduce the friction coefficient and wear loss of composites. Through ANSYS thermal steady-state simulation, S-GNS-AF/POMC has the maximum number of heat flow paths and the highest heat flux compared with other materials.

Comparisons of the microstructures and micro-mechanical properties of copper/steel explosive-bonded wave interfaces

This paper presents a systematic study of the differences in the microstructures and micro-mechanical properties of various Cu/Fe wave interfaces prepared by explosive welding. These wave interfaces, fabricated by different parameters, have been divided into four categories according to variations in their microstructures and the element distribution: vortex region, transition layer, interface without metal bonding, and interface with defects. In the wave interfaces, nanocrystalline areas filled with nano-copper and nano-iron grains (50 nm), medium-sized grains (300 nm), coarse grains (1 μm) and finer nanocrystals (5 nm) or amorphous phases in wave interfaces. The variations in the grain size contribute to the inhomogeneity of hardness distribution in the first kind of interface, the vortex region. In the second kind of interface, the transition layer, both EDS and TEM measurements reveal a gradient in the element contents due to atomic diffusion. This transition layer possesses rather higher and more uniformly distributed nano-hardness (up to 15.75 GPa) because of the combined effects of fine grain strengthening and work hardening. The third kind of interface with an abrupt change in element distribution does not form metal bonds at the boundaries. Additionally, a comprehensive analysis on these four kinds of interfaces suggests that the second type of interface (transition layer) is the ideal one.

The Interfacial Characterization and Performance of Cu/Al-Conductive Heads Processed by Explosion Welding, Cold Pressure Welding, and Solid-Liquid Casting

The Cu/Al composites conductive head is widely used in hydrometallurgy as the core component of cathode plate. Its conductive properties directly affect the power consumption, and the bonding strength and corrosion resistance determine the conductive head service life. The Cu/Al conductive head prepared by explosion welding, cold pressure welding, and solid-liquid casting methods were investigated in this paper. The interface microstructure and compositions were examined by scanning electron microscope and X-ray energy dispersive spectrometry. The bonding strength, interface conductivity, and the corrosion resistance of three types of joints were characterized. The Cu/Al bonding interface produced by explosive welding presented a wavy-like morphology with typical defects and many of brittle compounds. A micro-interlocking effect was caused by the sawtooth structures on the cold pressure welding interface, and there was no typical metallurgical reaction on the interface. The Cu/Al bonding interface prepared by solid-liquid casting consisted mainly of an Al-Cu eutectic microstructure (Al2Cu+Al) and partial white slag inclusion. The thickness of the interface transition layer was about 200–250 µm, with defects such as holes, cracks, and unwelded areas. The conductivity, interfacial bonding strength, and corrosion resistance of the conductive head prepared by explosive welding were superior to the other two.

A Parallel Bicomponent TPU/PI Membrane with Mechanical Strength Enhanced Isotropic Interfaces Used as Polymer Electrolyte for Lithium-Ion Battery.

In this work, a side-by-side bicomponent thermoplastic polyurethane/polyimide (TPU/PI) polymer electrolyte prepared with side-by-side electrospinning method is reported for the first time. Symmetrical TPU and PI co-occur on one fiber, and are connected by an interface transition layer formed by the interdiffusion of two solutions. This structure of the as-prepared TPU/PI polymer electrolyte can integrate the advantages of high thermal stable PI and good mechanical strength TPU, and mechanical strength is further increased by those isotropic interface transition layers. Moreover, benefiting from micro-nano pores and the high porosity of the structure, TPU/PI polymer electrolyte presents high electrolyte uptake (665%) and excellent ionic conductivity (5.06 mS·cm−1) at room temperature. Compared with PE separator, TPU/PI polymer electrolyte exhibited better electrochemical stability, and using it as the electrolyte and separator, the assembled Li/LiMn2O4 cell exhibits low inner resistance, stable cyclic and notably high rate performance. Our study indicates that the TPU/PI membrane is a promising polymer electrolyte for high safety lithium-ion batteries.

Influence of Extrusion Speed on the Microstructure Evolution, Interface Bonding and Mechanical Response of Mg MB26/Al 7075 Composite Rod

The Mg MB26/Al 7075 composite rod, in which Mg MB26 serves as the sleeve and Al 7075 serves as the core, is fabricated via the process of co-extrusion. The influence of extrusion speed on the microstructure evolution, interface bonding and mechanical response of the Mg MB26/Al 7075 composite rod is investigated. The results show that the typical extrusion texture of Mg sleeve does not change during co-extrusion; however, the average grain size in the Mg sleeve slightly changes from 1.57 μm in the case of extrusion speed of 0.3 mm/s to 2.78 μm in the case of extrusion speed of 2.1 mm/s. The thickness of interface transition layer increases significantly from 5.5 to 50 μm, and therefore, the interface bonding becomes deteriorative with increasing extrusion speed; in particular, many cavities emerge in the case of 1.2 and 2.1 mm/s.

A meso-scale analysis of the hygro-thermo-chemical characteristics of early-age concrete

Concrete has a high degree of heterogeneity and a complex porous structure, so to accurately study the performance evolution mechanism of concrete, multi-scale research should be carried out. A three-phase meso-model of concrete is constructed based on the method of randomly generating particles. A meso-macro connection framework is built, and the accuracy of the fixed hygro-thermo-chemical model at the meso-scale is verified through comparing its outcomes with experimental data and macroscopic results. The hygro-thermo-chemical behaviours of early-age concrete at the meso-scale are studied under adiabatic–sealed, radiating–sealed and adiabatic–drying conditions, by considering the cooling effect of the aggregate, low diffusivity of the aggregate, high diffusivity of the interface transition layer and concrete gradation. Additionally, distribution and evolution of several eigenvalues, such as the relative humidity, are obtained.

Effects of As2 pressure on InAs heteroepitaxial growth on vicinal GaSb(001) substrate by molecular beam epitaxy

The effects of As2 pressure on the InAs heteroepitaxial growth on a vicinal GaSb(001) substrate by solid-source molecular beam epitaxy were investigated. Transition layers with small lattice constants compared with GaSb caused by As/Sb exchange were observed at various pressures. When the As2 pressure was high, misfit dislocations were observed at the interface transition layer. As the As2 pressure decreased, misfit dislocations disappeared with the reduction in transition layer thickness, whereas pits were formed. From the result of strain analysis, dislocations were found to accompany lattice relaxation, whereas pits were formed by excess As2 pressure. By further reducing the As2 pressure, a high-quality pseudomorphic InAs layer free from dislocations and pits was obtained.

Preparation, properties and modification mechanism of polyurethane modified emulsified asphalt

To prepare new polyurethane (PU) modified emulsified asphalt (EA), and further understand modification mechanism of PU to EA, effects of PU on basic engineering performances, chemical composition compatibility, morphology and element compositions, thermal properties, phase microstructures of EA were discussed. The results indicate that basic properties of PU modified EA firstly meet relevant requirements of technical specifications. Improvement effects of PU with a suitable content on penetration and ductility is better than that of styrene butadiene styrene (SBS), but their softening points are similar. Secondly, PU modified EA process includes physical and chemical modifications. PU is dispersed uniformly in evaporation residues of EA when PU content is less than 6%, and meta-stable two-phase interface transition layers are formed between PU and asphalt binder, forming a uniform dispersion system and interpenetrating network structures in modified EA. The compatibility between PU and EA is satisfactory, forming a stable multiphase structure in modified EA. This is conductive to improve high-temperature stability and low-temperature ductility of modified EA. Thirdly, the contents of such main chemical elements as carbon (C), oxygen (O) and sulfur (S) in evaporation residues of EA show no obvious changes before and after modified by PU, indicating that physical modification is main method during the preparation of PU modified EA. Fourthly, PU is difficult to form a continuous crystalline phase in EA. However, the molecular chain spacing and microcrystalline size of PU modified EA are decreased at a suitable PU content, generating more compact interpenetrating network of molecular chains. Motions of asphalt molecules are limited, improving thermal stability and mechanical properties of EA. Finally, a suitable PU content of 6% is proposed to prepare modified EA.

Mitigating Interfacial Potential Drop of Cathode-Solid Electrolyte via Ionic Conductor Layer To Enhance Interface Dynamics for Solid Batteries.

The rapid capacity decay caused by the poor contact and large polarization at the interface between the cathode and solid electrolytes is still a big challenge to overcome for high-power-density solid batteries. In this study, a superior Li+ conductive transition layer Li1.4Al0.4Ti1.6(PO4)3 is introduced to coat LiNi0.6Co0.2Mn0.2O2, as a model cathode, to mitigate polarization and enhance dynamic characteristics. The critical attribute for such superior dynamics is investigated by the atomic force microscopy with boundary potential analysis, revealing that the formed interfacial transition layer provides a gradual potential slope and sustain-released polarization, and endows the battery with improved cycling stability (90% after 100 cycles) and excellent rate capability (116 mA h g-1 at 2 C) at room temperature, which enlightens the comprehension of interface engineering in the future solid batteries systems.

A multiscale numerical simulation approach for chloride diffusion and rebar corrosion with compensation model

Refined analysis depicting mass transportation and physicochemical reaction and reasonable computing load with acceptable DOFs are the two major challenges of numerical simulation for concrete durability. Mesoscopic numerical simulation for chloride diffusion considering binder, aggregate and interfacial transition zone is unable to be expended to the full structure due to huge number of DOFs. In this paper, a multiscale approach of combining both mesoscopic model including full-graded aggregate and equivalent macroscopic model was introduced. An equivalent conversion of chloride content at the Interfacial Transition Layer (ITL) connecting both models was considered. Feasibility and relative error were discussed by analytical deduction and numerical simulation. Case study clearly showed that larger analysis model in multiscale model expanded the diffusion space of chloride ion and decreased chloride content in front of rebar. Difference for single-scale simulation and multiscale approach was observed. Finally, this paper addressed some worth-noting conclusions about the chloride distribution and rebar corrosion regarding the configuration of rebar placement, rebar diameter, concrete cover and exposure period.

Effect of carbon nanotubes and octa-aminopropyl polyhedral oligomeric silsesquioxane on the surface behaviors of carbon fibers and mechanical performance of composites

A kind of carbon fiber/carbon nanotubes/octa-aminopropyl polyhedral oligomeric silsesquioxane (CF/CNTs/POSS for short) reinforcement was prepared by grafting CNTs and OA-POSS to CFs surfaces in order to improve the mechanical properties and interfacial performance. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and contact angle testing and analysis were applied to characterize the carbon fibers surface. Tensile testing, bending testing and interlayer shear strength (ILSS) testing were employed to analyze the mechanical properties of composites. The experimental results of SEM and XPS indicate that CNTs and OA-POSS are grafted uniformly on fibers surface with chemical bonding of NH in CNTs and POSS and COOH on CFs surface. The contact angle test and analysis results show that the surface energy of modified CFs decrease compared with that of the unmodified. Furthermore, the mechanical properties of composites after coating with CNTs and OA-POSS are enhanced effectively. Especially, the properties of composites fabricated by CF/1%CNTs/POSS are significantly improved, because OA-POSS increases the interfacial strength and CNTs increases the thickness of the interfacial transition layer, which both improves the interface defects diffusion of composites. Therefore, CF/CNTs/POSS can improve the performance of the composites by forming interface transition layers.

Study of the Boron Distribution and Microstructure of Solidified Al-Si Alloy During the Process of Silicon Purification

AbstractThe Al-Si melts that contain different silicon contents were solidified with a series of cooling rates, and the boron contents in primary silicon phases and eutectic silicon phases were measured and discussed. The results indicate that the boron content in the eutectic silicon phases is higher than that in the primary silicon phases when the cooling rate is constant. When the cooling rate decreases, the boron content in the primary silicon phases decreases, but the boron content in the eutectic silicon phases increases. The microstructure observations of solidified ingots show that there is an interface transition layer beside the primary silicon phase, and the average width of the interface transition layer increases with decreasing cooling rate.

Macromodel of interfacial transition layer in ceramic matrix composites

The purpose of the study is to create a macromodel of interfacial transition layer in ceramic matrix composites. Chemical and mineralogical compositions were investigated by means of X-ray fluorescence analysis and X-ray diffractometry, ceramic and technological properties of raw materials were defined using standard test methods for argillaceous raw materials. Phase composition and structure of ceramic specimens were studied using a complex of modern physico-chemical analysis methods. The layer-by-layer model of shell-core transition in ceramic matrix material was suggested. Boundary conditions for obtaining specimens were defined in terms of number of layers, thickness of such layers and pitch of core-to-shell material ratio. Forced air supply was organized while burning for directed heat and mass transfer inside the specimens. Mineral composition of layers was defined for ceramic specimens with the core of iron ore waste and the shell of clay. The study enabled to determine dependences between qualitative and semi-quantitative variation of new mineral formations content in transitional layers of a composite, which is the evidence of interaction between the core and the shell products while burning a ceramic matrix material.

Macromodel of interfacial transition layer in ceramic matrix composites

The purpose of the study is to create a macromodel of interfacial transition layer in ceramic matrix composites. Chemical and mineralogical compositions were investigated by means of X-ray fluorescence analysis and X-ray diffractometry, ceramic and technological properties of raw materials were defined using standard test methods for argillaceous raw materials. Phase composition and structure of ceramic specimens were studied using a complex of modern physico-chemical analysis methods. The layer-by-layer model of shell-core transition in ceramic matrix material was suggested. Boundary conditions for obtaining specimens were defined in terms of number of layers, thickness of such layers and pitch of core-to-shell material ratio. Forced air supply was organized while burning for directed heat and mass transfer inside the specimens. Mineral composition of layers was defined for ceramic specimens with the core of iron ore waste and the shell of clay. The study enabled to determine dependences between qualitative and semi-quantitative variation of new mineral formations content in transitional layers of a composite, which is the evidence of interaction between the core and the shell products while burning a ceramic matrix material.