Structure Of Interfacial Layer Research Articles

Preparation and interfacial layer microstructure of multilayer heterogeneous composite

The appropriate hetero interfacial layer structure between metal and ceramic matrix composites is a very interesting topic in materials science. In this work, an adaptive diffusion reactive interfacial layer composed of “Mo–Mo 2 C–Mo 5 Si 3 –MoSi 2 –SiC” between Mo and SiC f /SiC composite is successfully prepared by chemical vapor infiltration (CVI). This reactive interfacial system is among three possible structures of interfacial layers predicted by Density-functional theory (DFT) calculations, which has the largest total interfacial energy (5.679 J/m 2 ). At the same time, the formation process of the reaction interface layers is elucidated by thermodynamic calculations . In addition, dislocations are observed in Mo 5 Si 3 and Mo 2 C grains, and it is worth mentioning that the Mo 5 Si 3 grains are broken through dislocation movement to form fine grains, which release the residual thermal stress of the interfacial layer system caused by thermal mismatch during the long-term CVI process. Overall, our work provides a practical strategy for developing multilayer heterogeneous composites.

Dual In Situ Laser Techniques Underpin the Role of Cations in Impacting Electrocatalysts.

Understanding the electrode/electrolyte interface is crucial for optimizing electrocatalytic performances. Here, we demonstrate that the nature of alkali metal cations can profoundly impact the oxygen evolution activity of surface‐mounted metal–organic framework (SURMOF) derived electrocatalysts, which are based on NiFe(OOH). In situ Raman spectroscopy results show that Raman shifts of the Ni−O bending vibration are inversely proportional to the mass activities from Cs+ to Li+. Particularly, a laser‐induced current transient technique was introduced to study the cation‐dependent electric double layer properties and their effects on the activity. The catalytic trend appeared to be closely related to the potential of maximum entropy of the system, suggesting a strong cation impact on the interfacial water layer structure. Our results highlight how the electrolyte composition can be used to maximize the performance of SURMOF derivatives toward electrochemical water splitting.

Dual In Situ Laser Techniques Underpin the Role of Cations in Impacting Electrocatalysts

AbstractUnderstanding the electrode/electrolyte interface is crucial for optimizing electrocatalytic performances. Here, we demonstrate that the nature of alkali metal cations can profoundly impact the oxygen evolution activity of surface‐mounted metal–organic framework (SURMOF) derived electrocatalysts, which are based on NiFe(OOH). In situ Raman spectroscopy results show that Raman shifts of the Ni−O bending vibration are inversely proportional to the mass activities from Cs+ to Li+. Particularly, a laser‐induced current transient technique was introduced to study the cation‐dependent electric double layer properties and their effects on the activity. The catalytic trend appeared to be closely related to the potential of maximum entropy of the system, suggesting a strong cation impact on the interfacial water layer structure. Our results highlight how the electrolyte composition can be used to maximize the performance of SURMOF derivatives toward electrochemical water splitting.

Experimental evidence of a mixed amorphous-crystalline graphene/SiC interface due to oxygen-intercalation

• Oxygen intercalation in graphene/SiC systems leads to a highly disordered interface. • Amorphous phases were detected by means of two different experimental techniques. • Silicon oxycarbides (SiO X C Y ) structures were observed by photoelectron diffraction. • The abundant existence of SiO X C Y structures is related to the high degree of disorder. The introduction of atoms of different chemical species between epitaxial graphene and the SiC substrate by means of an intercalation process has been a reliable route to modify the interaction of this 2D material and its underlying substrate. Distinct atomic species have been intercalated so far and studies focusing on bond states of the electronically active layers were successful, retrieving the local chemical environment. However, the structure of interfacial layers is strongly affected whenever a more reactive atom is used in the intercalation process. In this work, we present experimental evidence based on X-ray crystal truncation rod scattering and photoelectron diffraction showing the coexistence of crystalline and amorphous regions in the oxidized interface. This interface between a bilayer graphene and the SiC substrate is generated by O-intercalation. Such fluctuations of the local structure are crucial to understand the abundant existence of silicon oxycarbides structures (SiO X C Y ) within the interfacial layer, which has been associated with the limited electronic properties of O- intercalated graphene bilayers. Consequently, this may be considered as a deterministic factor that affects device potentialities in these systems. .

Water contact angles on charged surfaces in aerosols

Interactions between water and solid substrates are of fundamental importance to various processes in nature and industry. Electric control is widely used to modify interfacial water, where the influence of surface charges is inevitable. Here we obtain positively and negatively charged surfaces using LiTaO3 crystals and observe that a large net surface charge up to 0.1 C/m2 can nominally change the contact angles of pure water droplets comparing to the same uncharged surface. However, even a small amount of surface charge can efficiently increase the water contact angle in the presence of aerosols. Our results indicate that such surface charges can hardly affect the structure of interfacial water molecular layers and the morphology of the macroscopic droplet, while adsorption of a small amount of organic contaminants from aerosols with the help of Coulomb attraction can notably decrease the wettability of solid surface. Our results not only provide a fundamental understanding of the interactions between charged surfaces and water, but also help to develop new techniques on electric control of wettability and microfluidics in real aerosol environments.

Scalable and Controllable Synthesis of Interface-Engineered Nanoporous Host for Dendrite-Free and High Rate Zinc Metal Batteries.

Rechargeable zinc (Zn)-ion batteries are regarded as highly prospective candidates for next-generation renewable and safe energy storage systems. However, the uncontrolled dendrite growth of the Zn anode impedes their practical application. Here, a scalable and controllable approach is developed for converting commercial titanium (Ti) foil to 3D porous Ti, which retains good resistance to corrosion, high electrical conductivity, and excellent mechanical properties. Benefiting from a spontaneous ultrathin zincophilic titanium dioxide (TiO2) interfacial layer and continuous 3D structure, the 3D porous Ti can act as an effective host to achieve a 3D Ti/Zn metal anode. By ensuring homogeneous nucleation, uniform current distribution, and volume change accommodation, the dendritic growth of 3D Ti/Zn metal anode is effectively inhibited with stable Zn plating/stripping up to 2000 h with low polarization. When conjugated with a 3D sulfur-doped Ti3C2Tx MXene@MnO2 nanotube cathode, a high rate and stable Zn cell is achieved with 95.46% capacity retention after 500 cycles at a high rate of 5 A g-1. This work may also be interesting for researches in porous metals and other battery systems.

Effect of Ni on the Suppression of Sn Whisker Formation in Sn-0.7Cu Solder Joint.

The evolution of internal compressive stress from the intermetallic compound (IMC) Cu6Sn5 growth is commonly acknowledged as the key inducement initiating the nucleation and growth of tin (Sn) whisker. This study investigates the effect of Sn-0.7Cu-0.05Ni on the nucleation and growth of Sn whisker under continuous mechanical stress induced. The Sn-0.7Cu-0.05Ni solder joint has a noticeable effect of suppression by diminishing the susceptibility of nucleation and growth of Sn whisker. By using a synchrotron micro X-ray fluorescence (µ-XRF) spectroscopy, it was found that a small amount of Ni alters the microstructure of Cu6Sn5 to form a (Cu,Ni)6Sn5 intermetallic layer. The morphology structure of the (Cu,Ni)6Sn5 interfacial intermetallic layer and Sn whisker growth were investigated by scanning electron microscope (SEM) in secondary and backscattered electron imaging mode, which showed that there is a strong correlation between the formation of Sn whisker and the composition of solder alloy. The thickness of the (Cu,Ni)6Sn5 IMC interfacial layer was relatively thinner and more refined, with a continuous fine scallop-shaped IMC interfacial layer, and consequently enhanced a greater incubation period for the nucleation and growth of the Sn whisker. These verification outcomes proposes a scientifically foundation to mitigate Sn whisker growth in lead-free solder joint.

Development and Optimization of Tin/Flux Mixture for Direct Tinning and Interfacial Bonding in Aluminum/Steel Bimetallic Compound Casting.

Interfacial bonding highly affects the quality of bimetallic bearing materials, which primarily depend upon the surface quality of a solid metal substrate in liquid–solid compound casting. In many cases, an intermediate thin metallic layer is deposited on the solid substrate before depositing the liquid metal, which improves the interfacial bonding of the opposing materials. The present work aims to develop and optimize the tinning process of a solid carbon steel substrate after incorporating flux constituents with the tin powder. Five ratios of tin-to-flux—i.e., 1:1, 1:5, 1:10, 1:15, and 1:20—were used for tinning process of carbon steel solid substrate. Furthermore, the effect of volume ratios of liquid Al-based bearing alloy to solid steel substrate were also varied—i.e., 5:1, 6.5:1 and 8.5:1—to optimize the microstructural and mechanical performance, which were evaluated by interfacial microstructural investigation, bonding area determination, hardness and interfacial strength measurements. It was found that a tin-to-flux ratio of 1:10 offered the optimum performance in AlSn12Si4Cu1/steel bimetallic materials, showing a homogenous and continuous interfacial layer structure, while tinned steels using other percentages showed discontinuous and thin layers, as in 1:5 and 1:15, respectively. Furthermore, bimetallic interfacial bonding area and hardness increased by increasing the volume ratio of liquid Al alloy to solid steel substrate. A complete interface bonding area was achieved by using the volume ratio of liquid Al alloy to solid steel substrate of ≥8.5.

Features of the structure of interfacial layers in polymer composites

Using relaxation spectrometry methods, the features of formation of interfacial layers in polymer composites based on 5-211-BN epoxyanilinophenol formaldehyde binder reinforced with CBM high-modulus aramid fibers are studied. The cases of the initial unmodified and modified neutralization of the surface of the reinforcing filler under loading in various temperature-time regimes are considered. It is shown that the used set of relaxation spectrometry methods allows one to evaluate the features of formation and the structure of interfacial layers in polymer-polymer systems. It is established that the morphological structure of the interfacial layer is strongly dependent on the chemical nature of the components and on the intensity of their interaction.

Segregation of Alloying Elements to Stabilize Teta Prime Phase Interfaces in Al-Cu Based Alloys

Interactions of alloying elements (Si,Mg,Mn,Zr,Zn) and vacancies with coherent interfaces of θ′ phase in Al-based alloys have been systematically studied by means of ab initio calculations. The interface structure with a filled interfacial Cu layer is calculated to be lower in energy than the structure with a half-filled Cu layer (by 0.1 eV per structural vacancy), which implies that a temperature-induced reconstruction of the interface may take place. The presence of vacancies in the interfacial Cu layer structure plays a crucial role in the interaction of solutes with a coherent θ′ phase interface. The solute–interface interaction energies are calculated to be much weaker for elements having closed (Cu,Zn) or empty (Mg,Si) d-electron shells than for d-transition metals (Mn,Zr). To clarify the roles of alloying elements and interface structure in the stability of θ′ phase precipitates, we analyze the solute–interface interactions in terms of electronic-structure and atomic-size contributions to interatomic bonding.

High-Density Liquid Water at a Water-Ice Interface.

Because ice surfaces catalyze various key chemical reactions impacting nature and human life, the structure and dynamics of interfacial layers between water vapor and ice have been extensively debated with attention to the quasi-liquid layer. Other interfaces between liquid water and ice remain relatively underexplored, despite their importance and abundance on the Earth and icy extraterrestrial bodies. By in situ optical microscopy, we found that a high-density liquid layer, distinguishable from bulk water, formed at the interface between water and high-pressure ice III or VI, when they were grown or melted in a sapphire anvil cell. The liquid layer showed a bicontinuous pattern, indicating that immiscible waters with distinct structures were separated on the interfaces in a similar manner to liquid-liquid phase separation through spinodal decomposition. Our observations not only provide a novel opportunity to explore ice surfaces but also give insight into the two kinds of structured water.

Non-isothermal flow of an electrolyte in a charged nanochannel

Electrokinetic flows are generally analyzed, assuming isothermal conditions even though such situations are hard to be achieved in practice. In this paper, the flow of a symmetric electrolyte in a charged nanochannel subjected to an axial temperature gradient is investigated using molecular dynamics simulations. We analyze the relative contribution of the Soret effect, the thermoelectric effect, and the double layer potential in the electrical double layer for various surface charges and temperature gradients. We find the flow driven by thermal gradient is analogous to electroosmotic flow. The thermophoretic motion of the electrolyte is significant for negative surface charge than the positive surface charge. The vibrational spectrum of graphene is calculated to delineate the effect of the surface charge polarity on the observed thermophoretic motion of the electrolyte. A unique structure of interfacial water layer is observed for the positive and negative surface charges. We attribute the presence of these structures to the differences in water-carbon interactions existing for various surface charge polarity. For an applied thermal gradient in the range 2.6 K nm−1 to 8 K nm−1, we observe a continuous net flow with average velocities reaching up to 9.4 m s−1 inside the channel for a negative surface charge of −0.101 C m−2. The results indicate that in a charged graphene-based nanochannel, temperature gradients can be employed to induce streaming current, depending on the relative influence of the Soret effect and the double layer potential.

Effects of annealing temperature on the interfacial microstructure and bonding strength of Cu/Al clad sheets produced by twin-roll casting and rolling

Abstract In this paper, Cu/Al clad sheets were prepared by twin-roll casting and multi-pass cold rolling. Annealing treatment was performed at temperatures of 250 °C, 300 °C, 350 °C and 400 °C, separately. The influences of the annealing temperature on the interface layer structure, peel strength and peeled surface microstructure of the clad sheets were studied. The crack propagation behavior in the peeling process of the clad sheets was revealed, and the strengthening mechanism of the interface was explained. The results showed that the Cu/Al interface metallurgical bonding rate increased and the intermetallic compound layer thickness could be controlled within 550 nm after annealing at 250 °C, which encouraged more cracks to propagate along the Al matrix, and the average peel strength could reach approximately 39 N/mm. However, after high-temperature annealing treatment (350 °C and 400 °C), the clad sheet broke completely in the intermetallic compound layer, and a large number of cleavage fractures appeared, which caused the bonding strength to decrease sharply.

Exploring Structures at Air-Water Interfaces at Beamline P08, PETRA III

Organic films at the air-water interface are widely used as model systems, e.g. for biomembrane systems. At the High Resolution Diffraction Beamline P08 at PETRA III, Hamburg, the grazing incidence diffraction setup with Langmuir trough allows users to obtain the in-plane crystallographic order together with the out-of-plane structure of such interfacial layers. Recent developments on the setup have enabled the users to do structural studies during kinetic processes in situ, e.g. adsorption of ions and drugs to the lipid monolayers.

Influence of dispersity of reinforcing polymer to the polymer-fiber composite materials’ rigidity

This research aims at validation of the technological approaches to the provision of penetrating the polymer binder into the structure of the filament carrier in order to construct a developed interfacial layer in the form of molecular brushes. Brush “bristles”, enshrined by the outer end in the layer of the copolymer binder, can give elastic properties to the composite material obtained by duplicating the shell material with reinforced adhesive interlining materials.As a large part of the interlining materials range comprises a mixture of polyester fiber with cotton or viscose, the problem of accessibility of textile liner web for reinforcing polymer is originally considered in relation to the cellulosic component, which has a developed system of pore spaces.This work defines the technical possibility of regulating the elastic-deformation properties of the fused panels of garment by changing the degree of reinforcing polymer (RP) dispersion fineness, providing different terms for penetration into the structure of fiber material. To change the capacity of the RP to penetrate into the fiber structure a method of ultra-dispergation was used by the mechanical activation of hydrosols in a colloid mill. There is an experimental prove of the decisive role of the reinforcing polymer penetration into the pore spaces of the cellulose component of the interlining material for the formation the branched comb structure of interfacial layer, which provides a comprehensive improvement in the ability of materials to form the bulk shape of the garment and its preservation while distorting.

Experimental investigation on the interactions of asphaltenes and ethylene–vinyl acetate (EVA) copolymeric flow improvers at the interface between brine water and model oil

In oil fields, ethylene–vinyl acetate copolymers (EVA) are often added to the produced fluid as flow improvers. Asphaltenes in the crude oil and EVA can both adsorb at the interface and form a protective interfacial layer, affecting the emulsion stability of produced fluid. In this study, the effects of the interactions between asphaltenes and EVAs with different VA contents on the oil/water interfacial properties are investigated. To explore the adsorption behavior of asphaltenes and EVAs, the dynamic interfacial tension is firstly measured with droplet shape analysis method. The effects of the interactions between asphaltenes and EVAs are observed by analyzing the dynamic interfacial tension of the binary system and that of the single system. The added EVAs participate in the formation of interfacial layer and motivate the interfacial activity of asphaltenes to different degrees by influencing the dispersion state of asphaltenes in the model oil. The dilational modulus is then obtained by interfacial small-amplitude oscillation method. The addition of EVAs decreases the modulus, weakening the structure of interfacial layer. The conductivity experiment, asphaltene precipitation experiment and dynamic lighting scattering experiment are combined to explore the effect of EVAs on the dispersion state of asphaltenes. The polar moieties of EVAs interact with asphaltenes and form composite particles with peripheral nonpolar moieties, thus inhibiting asphaltenes from aggregation and improving the dispersion state. Among all the EVAs in this study, the EVA with 30% VA content has the strongest influence on the dispersion state of asphaltenes.

Electric double layer structure and capacitance of imidazolium-based ionic liquids with FSI− and Tf− anions at graphite electrode by molecular dynamic simulations

Abstract Molecular dynamic simulations were performed to investigate the interfacial electric double layer (EDL) structure and differential capacitance (Cd) of ionic liquids (ILs), 1-ethyl-3-methyl-imidazolium bis(fluorosulfonyl)imide (EMIM+/FSI−) and 1-ethyl-3-methyl-imidazolium trifluoromethanesulfonate (EMIM+/Tf−) on planar graphite electrode. The differential capacitance curve (Cd − U) of EMIM+/Tf− is asymmetric camel-shaped. The higher Cd of EMIM+/Tf− than the EMIM+/FSI− at 0–0.5 V and 1.1–2.4 V, is attributed to the formation of a thinner EDL of EMIM+/Tf− induced by the smaller size of Tf− compared to FSI−. In addition, because of the fewer interaction sites between cations and Tf− with the more localized negative charge distribution, Tf− anions are expelled away from the charged electrode more easily, which makes more effective screening of EMIM+/Tf− to the charged electrode than that of EMIM+/FSI−. Accordingly, the Cd of EMIM+/Tf− within the potential of −1.1 V to 0 V is higher than that of the EMIM+/FSI−. At highly negative potentials of −2.5 V to −1.1 V, FSI− with more interaction sites with cations are gradually squeezed out from the EDL, and more cations of EMIM+/FSI− accumulate to replace FSI−, leading to a higher Cd of EMIM+/FSI− than EMIM+/Tf−. Meanwhile, the Cd of EMIM+/Tf− decreases sharply due to the thicker EDL resulted from the overcrowded counterions.

Reduction of the Hysteresis Voltage in Atomic‐Layer‐Deposited p‐Type SnO Thin‐Film Transistors by Adopting an Al2O3 Interfacial Layer

AbstractThe origin of hysteresis in the drain–source current (IDS)–gate‐source voltage (VGS) characteristics of atomic‐layer‐deposited (ALD) p‐type SnO thin‐film transistors (TFTs) is examined by adding ALD Al2O3 interfacial layers (IL) between the SnO channel layer and the SiO2 gate insulator (GI) layer. SnO TFTs with SiO2 GI exhibit a large hysteresis voltage (Vhy) due to the trap state density near the interface between the SnO active layer and the SiO2 GI (known as the border trap). Both experimental results and theoretical calculations show that the origin of border traps is the gap states in SiO2, which is induced by the Sn diffusion into the SiO2 layer. The use of Al2O3 films as ILs suppresses this diffusion. The effectiveness, however, is dependent on the thickness, crystallinity, and density of the Al2O3 films. The Vhy of the SnO TFTs can be decreased when the thickness and density of the ILs is increased if the amorphous structure of the Al2O3 IL is maintained after the rapid thermal annealing process. p‐Type ALD SnO TFTs with optimum ILs exhibit a high on‐off ratio of IDS (1.2 × 105), high field‐effect mobility (1.6 cm2 V−1 s−1), and a small Vhy (0.2 V).

Quantitatively identify and understand the interphase of SiO2/rubber nanocomposites by using nanomechanical mapping technique of AFM

Abstract The interphase between nanofillers and rubber matrix, also known as “bound rubber (BR)” composed of a tightly BR (TBR) layer that strongly interacts with the filler and a loosely BR (LBR) layer that is physically adsorbed, plays an important role in the properties of rubber nanocomposites. Up to now, there is seldom direct evidence of such interfacial double layer structure and their thickness. In this study, we quantitatively identified the interphase of a representative nano silicon dioxide (SiO2)/rubber composites by using peak force quantitative nanomechanical mapping (PFQNM) mode of Atomic Force Microscope (AFM). The thickness of interphase was quantitatively obtained, and the double layer structure of interphase was directly identified based on PFQNM images and the corresponding force-distance curves, and was further evidenced by high resolution transmission electron microscopy. We further studied the effect of molecular polarity on interphase of SiO2/hydrogenated nitrile butadiene rubber (HNBR) composites. Interestingly, the molecular polarity of HNBR has almost no effect on the thickness of TBR layer but has a significant effect on the LBR layer, leading to the remarkable increase in the total interfacial thickness of the composites with increasing the acrylonitrile content. The mechanism for the formation of interfacial double layer structure of BR and the effect of molecular polarity on the double layer structure was discussed. This study provides a simple method to identify and deeply understand the double layer structure of the interphase, and thus provides guidance for the design of interphase for the preparation of high performance rubber nanocomposites.

Adsorption and Interfacial Layer Structure of Unmodified Nanocrystalline Cellulose at Air/Water Interfaces.

Nanocrystalline cellulose (NCC) is a promising biological nanoparticle for the stabilization of fluid interfaces. However, the adsorption and interfacial layer structure of NCC are poorly understood as it is currently unknown howto form NCC interfacial layers. Herein, we present parameters for the adsorption of unmodified NCC at the air-water (A/W) interface. Initial NCC adsorption is limited by diffusion, followed by monolayer saturation and decrease in surface tension at the time scale of hours. These results confirm the current hypothesis of a Pickering stabilization. NCC interfacial performance can be modulated by salt-induced charge screening, enhancing adsorption kinetics, surface load, and interfacial viscoelasticity. Adsorbed NCC layers were visualized by atomic force microscopy at planar Langmuir films and curved air bubbles, whereat NCC coverage was higher at curved interfaces. Structural analysis by neutron reflectometry revealed that NCC forms a discontinuous monolayer with crystallites oriented in the interfacial plane at a contact angle < 90°, favoring NCC desorption upon area compression. This provides the fundamental framework on the formation and structure of NCC layers at the A/W interface, paving the way for exploiting NCC interfacial stabilization for tailored colloidal materials.