Composition and Element Distribution Mapping of γ' and γ″ Phases of Inconel 718 by High-Resolution Scanning Transmission Electron Microscopy and X-ray Energy-Dispersive Spectrometry

The main strengthening mechanism for Inconel 718 (IN718), a Ni-based superalloy, is precipitation hardening by γ' and γ″ particles. It is thus essential, for good alloy performance, that precipitates with the desired chemical composition have adequate size and dispersion. The distribution of the γ' and γ″ phases and their chemical composition were investigated in the nickel-based Inconel 718 superalloy by taking advantage of the new capabilities of scanning transmission electron microscopy and energy-dispersive X-ray spectrometry using a windowless multiple detector, a high-brightness Schottky electron gun, and a spherical aberration corrector in the illumination probe optics. A small routine was developed to deconvolute the respective compositions of γ' and γ″ nanoprecipitates embedded in the γ matrix. Keeping the electron probe current low enough-a few hundred pA-prevented excessive irradiation damage during the acquisition of element maps and brought their spatial resolution down to the atomic column level to track their element compositions. The present results agree with and complement atomic probe tomography observations and Thermo-Calc predictions from the literature. The presence of an Al enrichment at the γ'/γ″ interface-which may control the γ″ phase coarsening-is observed in the last row of Al-Nb-Ti columns along this interface. In addition, a few columns with similar composition changes are found randomly distributed in the γ' phase.

Investigation on the Interface Structure, Mechanical Properties, and Thermal Stability of TiAlSiN/TiAlN Multilayers

Recently, the TiAlSiN/TiAlN coatings with excellent mechanical and thermal properties have great potential for protective applications that face deteriorated service environments. Here, we systematically investigate the interface structure, mechanical properties, and thermal stability of TiAlSiN/TiAlN multilayers with varied Al and Si contents of TiAlSiN sublayer. Both Ti0.53Al0.38Si0.09N/Ti0.52Al0.48N (ML_1) and Ti0.48Al0.38Si0.14N/Ti0.52Al0.48N (ML_2) exhibit the face-centered cubic structure through epitaxial growth, whereas the Ti0.43Al0.48Si0.09N/Ti0.52Al0.48N (ML_3) shows a mixed cubic/wurtzite (c/w) structure. This mechanism is explored by first-principles calculations that the increased content of Al and Si within the TiAlSiN sublayer is detrimental to the formation of a coherent interface. Meanwhile, the change of interfacial structure leads to a variation in hardness from ∼35.6 GPa of ML_1 to ∼35.4 GPa of ML_2 and then to ∼30.9 GPa of ML_3. In addition, ML_1 presents a delayed thermal decomposition by ∼100 °C, compared to those of ML_2 and ML_3 multilayers.

Effects of alloying elements on diamond/Cu interface properties based on first-principles calculations

Diamond/copper composites with high thermal conductivity and a variable thermal expansion coefficient are promising materials for thermal management applications. However, achieving the desired thermal conductivity of the composite material is difficult due to detachment or weak bonding between diamond and Cu. The interfacial properties of diamond/Cu composites can be improved using metal matrix alloying methods. In this study, we investigate the effects of alloying elements (B, Cr, Hf, Mo, Nb, Si, Ti, V, Zr) on the interfacial properties of diamond/Cu using first-principles calculations. Results showed that all alloying components could increase the interfacial bonding of diamond/Cu. Analysis of the electronic structure revealed that increased interfacial bonding strength after doping was the result of the stronger bonding of the alloying element atoms to the C atoms. The C atoms in the first layer of diamond at the interface formed wave peaks near the Fermi energy level after doping with B or Si atoms, facilitating electron-phonon interaction at the interface. The phonon properties of B₄C and SiC were similar to those of diamond, which facilitated phonon-phonon coupling. B and Si were shown to be better alloying elements when interfacial bond strength and heat transfer were considered.

Progress in the Application of Food-Grade Emulsions

The detailed investigation of food-grade emulsions, which possess considerable structural and functional advantages, remains ongoing to enhance our understanding of these dispersion systems and to expand their application scope. This work reviews the applications of food-grade emulsions on the dispersed phase, interface structure, and macroscopic scales; further, it discusses the corresponding factors of influence, the selection and design of food dispersion systems, and the expansion of their application scope. Specifically, applications on the dispersed-phase scale mainly include delivery by soft matter carriers and auxiliary extraction/separation, while applications on the scale of the interface structure involve biphasic systems for enzymatic catalysis and systems that can influence substance digestion/absorption, washing, and disinfection. Future research on these scales should therefore focus on surface-active substances, real interface structure compositions, and the design of interface layers with antioxidant properties. By contrast, applications on the macroscopic scale mainly include the design of soft materials for structured food, in addition to various material applications and other emerging uses. In this case, future research should focus on the interactions between emulsion systems and food ingredients, the effects of food process engineering, safety, nutrition, and metabolism. Considering the ongoing research in this field, we believe that this review will be useful for researchers aiming to explore the applications of food-grade emulsions.

Dual Function Modification of Cs2CO3 for Efficient Perovskite Solar Cells

Organic-inorganic hybrid perovskite solar cells (PeSCs) attract much attention in the field of solar cells due to their excellent photovoltaic performance. Many efforts have been devoted to improving their power conversion efficiency (PCE). However, few works focus on simultaneously improving their electrical and optical property. Herein, a simple strategy is proposed to improve the PCE from 19.8% of a reference device to 22.9%, by utilizing cesium carbonate (Cs₂CO₃) to modify indium tin oxide (ITO) substrate. The insertion of a Cs₂CO₃-modification layer between ITO substrate and SnO₂ electron transport layer simultaneously offers two benefits: improving the electron extraction capability and adjusting the light field distribution in the device. The optical optimization effect of Cs₂CO₃ revealed in this work has not been reported before. This work provides a new and simple strategy to obtain high performance PeSCs by improving the electrical and optical properties of the devices at the same time.

Unraveling the Complexity of Nano-Dispersoids in the Oxide Dispersion Strengthened Alloy 617

Nanocrystalline oxides are mainly responsible for Ni-base oxide dispersion strengthened (ODS) superalloys excellent thermo-mechanical properties. To establish the microstructural correlations between the metallic matrix and various oxide dispersoids, we report here the atomic-scale structure and chemistry of the complex nano-oxide dispersoids. Ultrahigh-resolution Cs-aberration-corrected scanning transmission electron microscopy (STEM) based techniques have been used to resolve nano-dispersoids in the Alloy 617 ODS. These nano-oxides, interestingly, possess a variety of high-angle annular dark-field (HAADF) contrasts, that is, bright, dark, and bi-phases. Both the light and heavy atoms have been found to be present in Y–Al–O complex-oxide nanostructures in varying quantities and forming a characteristic interface with the metallic matrix. In overcoming the limitation of conventional STEM-HAADF imaging, the integrated differential phase-contrast imaging technique was employed to investigate the oxygen atoms along with other elements in the dispersoids and its interface with the matrix. The most intriguing aspect of the study is the discovery of a few atoms thick Al2O3 interlayer (shell) around a monoclinic Y–Al–O core in the Ni-matrix. On the other hand, when the dispersoid is a hexagonal type Y–Al–O complex, the interface energy is already low, maintaining a semi-coherent interface and it was devoid of a shell.

Boosting CO2 Electroreduction via Construction of a Stable ZnS/ZnO Interface

Carbon dioxide (CO₂) electroreduction can offer a way of relieving environmental and energy issues. Gold and silver catalysts show considerable electrochemical performance for CO production; however, the electrochemical CO₂ conversion to CO is still restricted by the Faradaic efficiency, current density, and stability over the catalysts. Non-noble metal (zinc) is considered as a promising catalyst for CO₂ electroreduction because of its low cost. However, because of the electron-rich property of zinc, it has a weak adsorption capacity of intermediates, resulting in a poor CO₂ electroreduction performance. In this work, ZnS nanoparticles are embedded onto the ZnO surface to construct a stable ZnS/ZnO interface structure. The ZnS/ZnO interface reaches a maximum current density of 327.2 ± 10.6 mA cm^-2 with a CO Faradaic efficiency of 91.9 ± 0.6% at -0.73 V vs a reversible hydrogen electrode (RHE) and remains stable for 40 h at a current density of 115.7 ± 7.0 mA cm^-2 with a CO Faradaic efficiency of 93.8 ± 3.7% at -0.56 V vs RHE.

Identification of Interface Structure for a Topological CoS2 Single Crystal in Oxygen Evolution Reaction with High Intrinsic Reactivity

Transition metal chalcogenides such as CoS₂ have been reported as competitive catalysts for oxygen evolution reaction. It has been well confirmed that surface modification is inevitable in such a process, with the formation of different re-constructed oxide layers. However, which oxide species should be responsible for the optimized catalytic efficiencies and the detailed interface structure between the modified layer and precatalyst remain controversial. Here, a topological CoS₂ single crystal with a well-defined exposed surface is used as a model catalyst, which makes the direct investigation of the interface structure possible. Cross-sectional transmission electron microscopy of the sample reveals the formation of a 2 nm thickness Co₃O₄ layer that grows epitaxially on the CoS₂ surface. Thick CoO pieces are also observed and are loosely attached to the bulk crystal. The compact Co₃O₄ interface structure can result in the fast electron transfer from adsorbed O species to the bulk crystal compared with CoO pieces as evidenced by the electrochemical impedance measurements. This leads to the competitive apparent and intrinsic reactivity of the crystal despite the low surface geometric area. These findings are helpful for the understanding of catalytic origins of transition metal chalcogenides and the designing of high-performance catalysts with interface-phase engineering.

Effects of Hexagonal Boron Nitride Insulating Layers on the Driving Performance of Ionic Electroactive Polymer Actuators for Light-Weight Artificial Muscles

To improve the energy efficiency and driving performance of ionic electroactive polymer actuators, we propose inserting insulating layers of 170 nm hexagonal boron nitride (h-BN) particles between the ionic polymer membrane and electrodes. In experiments, actuators exhibited better capacitance (4.020 × 10-1 F), displacement (6.01 mm), and curvature (35.59 m-1) with such layers than without them. The excellent insulating properties and uniform morphology of the layers reduced the interfacial resistance, and the ion conductivity (0.071 S m-1) within the ionic polymer improved significantly. Durability was enhanced because the h-BN layer is chemically and thermally stable and efficiently blocks heat diffusion and ion hydrate evaporation during operation. The results demonstrate a close relationship between the capacitance and driving performance of actuators. A gripper prepared from the proposed ionic electroactive polymer actuator can stably hold an object even under strong external vibration and fast or slow movement.

Surface-Enhanced Raman Scattering Stimulated by Strong Metal-Molecule Interactions in a C60 Single-Molecule Junction

Specifying the geometric and electronic structures of a metal-molecule interface at the single-molecule level is crucial for the improvement of organic electronics. A single-molecule junction (SMJ) can be used to investigate interfaces because it can be regarded as an elementary unit of the interface structure. Although considerable efforts have been made to this end, the detection of structural changes in SMJs associated with metal-molecule interactions remains challenging. In this study, we detected the surface-enhanced Raman scattering (SERS) signal originating from the metal-molecule interaction change induced by a local structural change in a C₆₀ SMJ. This junction has attracted wide attention owing to its unique electronic and vibronic properties. We fabricated a C₆₀ SMJ using a lithographically fabricated Au electrode and measured the SERS spectra along with the current-voltage (I-V) response. By continuous measurement of SERS for the C₆₀ SMJ, we obtained SERS spectra dependent on the local structural change. The analysis of the I-V response revealed that the vibration energy shift originates from the change in the local structure for different Au-C₆₀ interactions. Based on the discrimination of the states in accordance with the Au-C₆₀ interaction, we found that the probability of SERS for geometry with a large Au-C₆₀ interaction was enhanced.

DFT-Based Studies on Carbon Adsorption on the wz-GaN Surfaces and the Influence of Point Defects on the Stability of the Diamond-GaN Interfaces

Integration of diamond with GaN-based high-electron-mobility transistors improves thermal management, influencing the reliability, performance, and lifetime of GaN-based devices. The current GaN-on-diamond integration technology requires precise interface engineering and appropriate interfacial layers. In this respect, we performed first principles calculation on the stability of diamond–GaN interfaces in the framework of density functional theory. Initially, some stable adsorption sites of C atoms were found on the Ga- and N-terminated surfaces that enabled the creation of a flat carbon monolayer. Following this, a model of diamond–GaN heterojunction with the growth direction [111] was constructed based on carbon adsorption results on GaN{0001} surfaces. Finally, we demonstrate the ways of improving the energetic stability of diamond–GaN interfaces by means of certain reconstructions induced by substitutional dopants present in the topmost GaN substrate’s layer.

High-Fidelity NIR-II Multiplexed Lifetime Bioimaging with Bright Double Interfaced Lanthanide Nanoparticles

Fluorescence lifetime imaging provides more possibility of in vivo multiplexing in second near infrared (NIR-II) window. However, it still faces the obstacle that fluorescent probes with differentiable lifetime often exhibit quite different fluorescence intensity, especially the short lifetime usually accompanies with a weak fluorescence intensity, resulting in the difficulty for simultaneously decoding multiplexed lifetime information due to the interference of background noise. To facilitate high-fidelity lifetime multiplexed imaging, we developed a series of Er³⁺ doped double interface fluorescent nanoprobes (Er-DINPs): α-NaYF₄ @NaErF₄ : Ce@NaYbF₄ @NaErF₄ : Ce@NaYF₄ with strong fluorescence intensity and easily distinguishable fluorescence lifetime. Both in vitro and in vivo experimental results confirmed the advantage of these probes with comparable fluorescence intensity for high-fidelity multiplexed lifetime bioimaging.

Modeling Electrified Pt(111)-Had/Water Interfaces from Ab Initio Molecular Dynamics

Unraveling the atomistic structures of electric double layers (EDL) at electrified interfaces is of paramount importance for understanding the mechanisms of electrocatalytic reactions and rationally designing electrode materials with better performance. Despite numerous efforts dedicated in the past, a molecular level understanding of the EDL is still lacking. Combining the state-of-the-art ab initio molecular dynamics (AIMD) and recently developed computational standard hydrogen electrode (cSHE) method, it is possible to realistically simulate the EDL under well-defined electrochemical conditions. In this work, we report extensive AIMD calculation of the electrified Pt(111)-Had/water interfaces at the saturation coverage of adsorbed hydrogen (Had) corresponding to the typical hydrogen evolution reaction conditions. We calculate the electrode potentials of a series of EDL models with various surface charge densities using the cSHE method and further obtain the Helmholtz capacitance that agrees with experiment. Furthermore, the AIMD simulations allow for detailed structural analyses of the electrified interfaces, such as the distribution of adsorbate Had and the structures of interface water and counterions, which can in turn explain the computed dielectric property of interface water. Our calculation provides valuable molecular insight into the electrified interfaces and a solid basis for understanding a variety of electrochemical processes occurring inside the EDL.

Enhanced Thermoelectric Performance of Carbon Nanotubes/Polyaniline Composites by Multiple Interface Engineering

Here, we put forward an effective strategy to regulate the interface structure of carbon nanotubes/polyaniline (CNTs/PANI) composite films and improve their thermoelectric (TE) properties by sequential dedoping-redoping treatment. Dedoping induces conductive resistance-undoped PANI to enhance the energy barrier between CNTs and PANI, leading to a greatly increased Seebeck coefficient and deteriorated conductivity. Subsequently, upon the redoping process, the electrical conductivity is dramatically improved owing to the generated conductive PANI chains, while Seebeck coefficient is maintained at 90% of the dedoped composites. This yields a significantly improved power factor of 407 μW m^-1 K^-2 from the as-prepared composites (234 μW m^-1 K^-2), which is the highest value among those of all the reported CNTs/PANI composites. The outstanding TE performanceis probably ascribed to the multiple interface structure of the PANI composite generated from incomplete dedoping and redoping processes, contributing to the enhanced carrier-filtering effect to retain a relatively high Seebeck coefficient and efficient charge transport to improve conductivity. Furthermore, the flexible TE device generates a high power of 1.5 μW at ΔT = 50 K, demonstrating the applicability of this composite for energy-harvesting electronic devices.

Unveiling the Interface Structure of the Exsolved Co-Fe Alloy Nanoparticles from Double Perovskite and Its Application in Solid Oxide Fuel Cells

Exsolution of catalytic nanoparticles (NPs) from perovskites has arisen as a flexible method to develop high-performance functional materials with enhanced durability for energy conversion and catalytic synthesis applications. Here, we unravel the interface structure of the in situ exsolved alloy nanoparticles from the double perovskite substrate on the atomic scale. The results show that the Co-Fe alloy NPs exsolved topologically from the {100} facets terminations of the Sr₂FeMo_0.65Co_0.35O_6-δ (SFMC) double perovskite along ⟨100⟩ directions exhibiting the same orientation and identical crystal structure. The lattice planes of these two phases align and insert into each other at the interface, forming a smooth and continuous coherent connection. The presence of moiré patterns at the interface confirms the topological exsolution mechanism. The coherent interface can significantly reduce the interfacial energy and therefore stabilize the exsolved nanoparticles. Therefore, excellent and stable electrochemical performance of the NP-decorated SFMC perovskite is observed as the anode for solid oxide fuel cells. Our contribution promotes a fundamental understanding of the interface structure of the in situ exsolved alloy nanoparticles from perovskite substrate.

Excellent Capacitor-Varistor Properties in Lead-Free CaCu3Ti4O12-SrTiO3 System with a Wrinkle Structure via Interface Engineering

Lead-free perovskite CaCu₃Ti₄O₁₂ (CCTO) dielectrics are extremely important candidates for capacitor-varistor dual-function materials. However, their overall success in applications is somewhat controlled by the longstanding issues such as relatively large dielectric loss and insufficiently high electric breakdown field. Herein, we report the success in the preparation of an optimized lead-free (1-x)CaCu₃Ti₄O₁₂-xSrTiO₃ (CCTO-STO) composite system with improved dielectric and nonlinear properties via interface engineering. Interestingly, looking closer at the grain boundaries using transmission electron microscopy, it is found that an obvious interface region with a transition layer of a wrinkled structure is formed between the CCTO matrix phase and STO dopant phase. Significantly, all the composite ceramic samples present high permittivity in the order of about 10³ to 10⁴, and the 0.9CCTO-0.1STO composite ceramic sample exhibits a lower dielectric loss of about 0.068 at room temperature and at 1 kHz. Excitingly, the optimized 0.9CCTO-0.1STO composite ceramic sample also exhibits a remarkably elevated breakdown field strength of about 14.03 kV/cm and a large nonlinear coefficient of about 16.11. The improvement in nonlinear properties with a high breakdown field strength and large nonlinear coefficient could be attributed to the interfacial effect in the composite structure, originating from the formation of the transition layer with a wrinkle structure at the interface between CCTO and STO phases. Such effects can result in great electrical heterogeneity caused by the higher resistance of the grain boundary and the enhanced potential barrier at the interface region. The new insights on the formation of the interfacial wrinkle structure near the phase boundaries of the CCTO-STO composite system and their effects on improvement of electrical properties can stimulate future research on lead-free CCTO-STO-based systems toward capacitor-varistor dual-function applications and may offer an effective way to design other lead-free dielectric materials as well.

Prediction of orientation relationships and interface structures between α-, β-, γ-FeSi2 and Si phases

A pure crystallogeometrical approach is proposed for predicting orientation relationships, habit planes and atomic structures of the interfaces between phases, which is applicable to systems of low-symmetry phases and epitaxial thin film growth. The suggested models are verified with the example of epitaxial growth of α-, γ- and β-FeSi₂ silicide thin films on silicon substrates. The density of near-coincidence sites is shown to have a decisive role in the determination of epitaxial thin film orientation and explains the superior quality of β-FeSi₂ thin grown on Si(111) over Si(001) substrates despite larger lattice misfits. Ideal conjunctions for interfaces between the silicide phases are predicted and this allows for utilization of a thin buffer α-FeSi₂ layer for oriented growth of β-FeSi₂ nanostructures on Si(001). The thermal expansion coefficients are obtained within quasi-harmonic approximation from the DFT calculations to study the influence of temperature on the lattice strains in the derived interfaces. Faster decrease of misfits at the α-FeSi₂(001)||Si(001) interface compared to γ-FeSi₂(001)||Si(001) elucidates the origins of temperature-driven change of the phase growing on silicon substrates. The proposed approach guides from bulk phase unit cells to the construction of the interface atomic structures and appears to be a powerful tool for the prediction of interfaces between arbitrary phases for subsequent theoretical investigation and epitaxial film synthesis.

Multiple Interface Structures of M23C6 carbides at Grain Boundary in an Aged 100Mn13 High Carbon High Manganese Steel

Multiple interface structures of M₂₃C₆ carbides precipitated at grain boundary in 100Mn13 high carbon high manganese steel, including the interface between the carbide particle and the matrix together with the interface between two adjacent carbides, were studied after 1050 °C solution treatment and subsequently after 475 °C aging treatment by high resolution transmission electron microscope (HRTEM) based on traditional transmission electron microscope (TEM). A growth model describing the adjacent M₂₃C₆ precipitations was proposed. The results show that precipitated carbide type is M₂₃C₆, which grows into both sides of austenite by a step growth mechanism. When two adjacent carbides precipitate along grain boundary, there are two cases as follows: If the two carbides have the same orientation relationship with the same austenite grain, they would grow independently to contact with each other to coalesce into a larger size carbide with the same orientation relationship. If the two carbides have different orientation relationships with the same austenite grain, and there is an original twinning in one carbide, they would grow independently to contact with each other to form a precipitated twinning.

Embedding Ultrafine Metal Oxide Nanoparticles in Monolayered Metal-Organic Framework Nanosheets Enables Efficient Electrocatalytic Oxygen Evolution

The development of highly efficient electrocatalysts to reduce overpotentials is vital for accelerating the sluggish oxygen evolution reaction (OER) processes. Herein, we demonstrate ultrathin heterogeneous nanosheets as a promising OER electrocatalyst, which are composed of ultrafine CoFeO_x nanoparticles and a monolayered CoN₄-based metal-organic framework (MOF) matrix. The embedding of such inorganic nanoparticles in the MOF lattice creates metal Co sites located at the CoFeO_x/MOF interfaces. Structural characterization and analysis indicated a higher valence and changed 3d electronic configuration for the interfacial Co in contrast to the CoN₄ sites. Furthermore, theoretical calculations reveal the high activity of interfacial Co sites for OER. Electrochemical studies confirm that the ultrathin heterogeneous nanosheets deposited on carbon cloth can achieve an excellent electrocatalytic OER performance with a low overpotential of 232 mV at a current density of 10 mA cm^-2 with good stability. This work provides insights on the development of ultrathin OER heterocatalysts with highly active interfaces of inorganic units and MOFs.

Orientation Relationships and Interface Structure in MgAl2O4 and MgAlB4 Co-Reinforced Al Matrix Composites

Ceramic phase reinforced aluminum matrix composites (CAMCs) are widely used in high-tech fields represented by aerospace industry due to their advantages of high specific strength, high specific modulus, high thermal stability, and light weight. Strong interface bonding is a prerequisite for high performance of multiphase materials. Herein, a novel CAMC in situ reinforced by MgAl₂O₄ particles and MgAlB₄ nanorods was prepared by vacuum hot-pressing combined with hot-extrusion process. A high-resolution transmission electron microscope was used to characterize the orientation relationship and interface structure between the ceramic phases and the aluminum matrix. Two orientation relationships (OR1 and OR2) of MgAl₂O₄/Al and one (OR3) of MgAlB₄/Al are determined: OR1-[011]_p//[011]_Al, (11̅1)_p//(11̅1)_Al; OR2-[211]_p//[011]_Al, (113̅)_p//(022̅)_Al; OR3-[101̅0]_R//[001]_Al, (0002)_R//(2̅20)_Al. The MgAl₂O₄ in OR1 forms a coherent interface with the aluminum matrix at (111) surface, while they form a 4 × 5 near coincidence site lattice (CSL) interface structure for OR2. In OR3, the MgAlB₄ forms an approximate coherent interface with Al matrix at its (0002) surface and a 2 × 5 CSL interface structure at its (011̅0) surface. First-principles calculations suggest that MgAl₂O₄ combines to aluminum at (111) plane through covalent bonds, which means high interfacial bonding strength. The hot-extrusion process makes the ceramic phase evenly distributed in the matrix. The mechanical properties of the composites are greatly improved compared with pure aluminum.

Deformation and Compressive Strength of Steel Fiber Reinforced MgO Concrete

To reduce the cracking caused by shrinkage and avoid the brittle behavior of concrete, MgO expansion agent and steel fibers were used in this paper. Firstly, the effect of MgO and steel fibers on the compressive strength of concrete was compared. The results showed that the compressive strength of steel fibers reinforced concrete (SC) and steel fiber reinforced MgO concrete (SMC) was significantly improved. Compared with ordinary concrete (OC), SMC’s 28 days compressive strength increased by 19.8%. Secondly, the influence of MgO and steel fibers with different contents on the self-volumetric deformation of concrete was compared through the experiment. The results showed that as a result of the hydration expansion of MgO, MC and SMC both showed obvious expansion, and their 190 days expansion was 335 με and 288 με, respectively. Lastly, through a scanning electron microscope (SEM) test, it was found that the constraint effect of steel fibers changed the expansion mode of MgO from outward expansion to inward extrusion, thus improving the interfacial bond strength of concrete.

Strongly Coupled Interface Structure in CoFe/Co3 O4 Nanohybrids as Efficient Oxygen Evolution Reaction Catalysts

The quest for developing electrochemical energy-storage and -conversion technologies continues to be a great impetus to develop cost-effective, highly active, and electrochemically stable electrocatalysts for overcoming the activation energy barriers of the oxygen evolution reaction (OER). Co₃ O₄ nanocrystals have great potential as OER catalysts, and research efforts on improving the catalytic activity of Co₃ O₄ are currently underway in many laboratories. Herein, CoFe layered double hydroxide (LDH) nanosheets were directly grown on the active Co₃ O₄ substrate to form nanohybrid electrocatalysts for OER. The CoFe LDH/Co₃ O₄ (6:4) nanohybrid exhibited superior catalytic performance with a low overpotential and a small Tafel slope in alkaline solution. The outstanding performance of the CoFe LDH/Co₃ O₄ (6:4) nanohybrid was primarily owing to the synergistic effects induced by the strongly coupled interface between CoFe LDH and Co₃ O₄ ; this feature enhanced the intrinsic OER catalytic activity of the nanohybrid and favored fast charge transfer. Compared with other Co₃ O₄ -based catalysts, the nanohybrid shows advantages and offers a feasible avenue for improving the activity of Co₃ O₄ -based catalysts.

Distinguishing nitrogen-containing sites in SiO2/4H-SiC(0001) after nitric oxide annealing by X-ray absorption spectroscopy

The atomic structure of nitrogen at the SiO₂/4H-SiC(0001) interface has been investigated using X-ray absorption spectroscopy (XAS) in two nitric oxide annealed samples, one of which was oxidized in dry O₂ (NO-POA) prior to the experiment. The peak shapes and energies of the observed and simulated spectra are in agreement and indicate that the N-containing sites could be the substitutional C site at the interface for the NO-annealed sample and the interstitial site in the interior of SiC for the NO-POA-annealed sample. XAS analysis distinguished between the N-containing sites at the SiO₂/SiC interface.

Charge Density Waves Driven by Peierls Instability at the Interface of Two-Dimensional Lateral Heterostructures

The origin of charge density wave (CDW) observed in low-dimensional systems is, for long, a subject of intensive debate in contemporary condensed matter physics. Specifically, a simple and well established model, namely, the Peierls instability is often (but not always) used to clearly explain CDW states in real systems. Here, first-principles density functional theory calculations are used to show CDW formation at a one-dimensional interface embedded in a lateral heterostructure comprising blue and black phosphorene, even at room temperature. The CDW formation is fully explained by the Peierls mechanism, including a double-periodicity lattice distortion energy lowering and a bandgap opening. The lattice distortion also substantially modifies the band alignment of the heterostructure. Comparison with a freestanding P chain shows that the structural distortion is confined to one dimension within the heterostructures, ruling out competing non-Peierls-type distortions in two dimensions. In addition, similar Peierls-type distortions for other lateral heterostructures are shown by using the example of a graphene-hexagonal boron nitride heterostructure, which may stimulate related studies in different 2D systems. These findings not only shed more light on the Peierls mechanism, but also have important implications for devices based on 2D lateral heterostructures.

Multifunctional Thermal Barrier Application Composite with SiC Nanowires Enhanced Structural Health Monitoring Sensitivity and Interface Performance

Carbon fiber (CF)-reinforced ceramic composites show the attractive potential for next generation thermal protection materials because of their outstanding reliability and excellent high-temperature resistance but are facing great challenges in the combination of the engineering practicality and versatility. Herein, it is demonstrated that silicon carbide nanowires can be grown on the surface of CF to create a multifunctional thermal barrier application composite. The embedding of the silicon carbide nanowires in the interface of CF and ceramic matrix significantly increased the structural health monitoring sensitivity and interface strength of the composites. Compared to the conventional CF/ZrC composites, the structural health monitoring sensitivity of the composites with SiC nanowires is greatly elevated with a 14-fold improvement. Additional investigations revealed that the multifunctional SiC_nws-CF/ZrC nanocomposites enjoyed a low thermal conductivity of 0.49 W/(m·K), a light weight (0.76-1.85 g/cm³), and a relative high compressive strength of 23.64 MPa, which is favorite in applying as a thermal barrier material. Furthermore, the interface design strategy could be extended as a universal method in fabricating various fiber-reinforced composites for a wide range of other applications.

Enhanced Interface Structure and Properties of Titanium Carbonitride-Based Cermets with the Extra Solid Phase Reaction

In this paper, the influence of the extra solid phase reaction on the interface structure and mechanical properties of titanium carbonitride-based cermets were investigated. The extra solid phase reaction in the preparation process of cermets could induce the formation of a core/rim/binder interface with the coherent structure and reinforce the interface bonding strength in cermets. The existence of a coherent structure interface can inhibit crack spread and improve the toughness and abrasion resistance of titanium carbonitride-based cermets significantly. Cermets can exhibit the high hardness Rockwell Hardness A (HRA) 92.3, fracture toughness of 11.6 MPa·m^1/2, and transverse rupture strength of 2810 MPa.

Interfacial Metal-Oxide Interactions in Resistive Switching Memories

Metal oxides are commonly used as electrolytes for redox-based resistive switching memories. In most cases, non-noble metals are directly deposited as ohmic electrodes. We demonstrate that irrespective of bulk thermodynamics predictions an intermediate oxide film a few nanometers in thickness is always formed at the metal/insulator interface, and this layer significantly contributes to the development of reliable switching characteristics. We have tested metal electrodes and metal oxides mostly used for memristive devices, that is, Ta, Hf, and Ti and Ta₂O₅, HfO₂, and SiO₂. Intermediate oxide layers are always formed at the interfaces, whereas only the rate of the electrode oxidation depends on the oxygen affinity of the metal and the chemical stability of the oxide matrix. Device failure is associated with complete transition of short-range order to a more disordered main matrix structure.

Effect of Core/Shell Interface on Carrier Dynamics and Optical Gain Properties of Dual-Color Emitting CdSe/CdS Nanocrystals

Two-color emitting colloidal semiconductor nanocrystals (NCs) are of interest for applications in multimodal imaging, sensing, lighting, and integrated photonics. Dual color emission from core- and shell-related optical transitions has been recently obtained using so-called dot-in-bulk (DiB) CdSe/CdS NCs comprising a quantum-confined CdSe core embedded into an ultrathick (∼7-9 nm) CdS shell. The physical mechanism underlying this behavior is still under debate. While a large shell volume appears to be a necessary condition for dual emission, comparison between various types of thick-shell CdSe/CdS NCs indicates a critical role of the interface "sharpness" and the presence of potential barriers. To elucidate the effect of the interface morphology on the dual emission, we perform side-by-side studies of CdSe/CdS DiB-NCs with nominally identical core and shell dimensions but different structural properties of the core/shell interface arising from the crystal structure of the starting CdSe cores (zincblende vs wurtzite). While both structures exhibit dual emission under comparable pump intensities, NCs with a zincblende core show a faster growth of shell luminescence with excitation fluence and a more readily realized regime of amplified spontaneous emission (ASE) even under "slow" nanosecond excitation. These distinctions can be linked to the structure of the core/shell interface: NCs grown from the zincblende cores contain a ∼3.5 nm thick zincblende CdS interlayer, which separates the core from the wurtzite CdS shell and creates a potential barrier for photoexcited shell holes inhibiting their relaxation into the core. This helps maintain a higher population of shell states and simplifies the realization of dual emission and ASE involving shell-based optical transitions.

Structure of A-C Type Intervariant Interface in Nonmodulated Martensite in a Ni-Mn-Ga Alloy

The structure of A-C type intervariant interface in nonmodulated martensite in the Ni54Mn25Ga21 alloy was studied using high resolution transmission electron microscopy. The A-C interface is between the martensitic variants A and C, each of which has a nanoscale substructure of twin-related lamellae. According to their different thicknesses, the nanoscale lamellae in each variant can be classified into major and minor lamellae. It is the boundaries between these lamellae in different variants that constitute the A-C interface, which is thus composed of major-major, minor-minor, and major-minor lamellar boundaries. The volume fraction of the minor lamellae, λ, plays an important role in the structure of A-C interfaces. For major-major and minor-minor lamellar boundaries, they are symmetrical or asymmetrical tilt boundaries; for major-minor boundary, as λ increases, it changes from a symmetrical tilt boundary to two asymmetrical microfacets. Moreover, both lattice and misfit dislocations were observed in the A-C interfaces. On the basis of experimental observations and dislocation theory, we explain how different morphologies of the A-C interface are formed and describe the formation process of the A-C interfaces from λ ≈ 0 to λ ≈ 0.5 in terms of dislocation-boundary interaction, and we infer that low density of interfacial dislocations would lead to high mobility of the A-C interface.

Influence of Interface Structure on Magnetic Proximity Effect in Pt/Y3Fe5O12 Heterostructures

The influence of interface structure on the magnetic proximity effect (MPE) in Pt/Y3Fe5O12 (YIG) bilayered heterostructures is studied by first-principles calculations based on the density functional theory (DFT). When Pt atoms are in close proximity with Y or Fe ions at the interface, Pt-Y and Pt-Fe bonds are observed. The crystalline orientations and interface termination layers of the YIG strongly modify both the strength and the length of the Pt-Fe bonding and thereby influence the magnetic properties of the Pt. Point defects including tetrahedral Fe, octahedral Fe, and Y vacancies are introduced at the Pt/YIG interface to quantitatively evaluate the influence on the MPE from individual atoms. For the Pt(100)/YIG(100) structure, the interface tetrahedral Fe vacancies can significantly reduce or even completely diminish the magnetic moments in the Pt. In a stark contrast, the octahedral Fe vacancies slightly enhance the Pt magnetism, and the nonmagnetic Y vacancies cause little influences to the Pt magnetism. These results indicate that the strength of the MPE at the Pt/YIG interface strongly depends on the interface structure. This dependence originated from the direct exchange interaction between the Fe 3d and Pt 5d electrons via electronic state hybridization as well as the electron exchange coupling between the Pt atoms.

Structural Origin of the Activity in Mn3O4-Graphene Oxide Hybrid Electrocatalysts for the Oxygen Reduction Reaction

Non-precious metal oxide/carbon hybrid electrocatalysts are of increasing importance for the oxygen reduction reaction (ORR). A synergistic effect is commonly used to explain the superior ORR activity exerted by metal oxide/nanocarbon hybrids, and this effect is attributed to covalently coupled interfaces between the two materials. However, the origin of the high activity, the structure, and the electrocatalytic nature of the interface remain unclear. By combining X-ray photoelectron spectroscopy with synchrotron far-infrared spectroscopy, we resolved the interface structure between spinel manganese oxide nanocrystals and graphene oxide nanoribbons, and the role of this interface in the promoted ORR. Moreover, we demonstrated the excellent ORR activity by a functional synergism of the hybrid constituents through a series of comparative electrochemical experiments.

Structure, Morphology and Reducibility of Epitaxial Cerium Oxide Ultrathin Films and Nanostructures

Cerium oxide is a very interesting material that finds applications in many different fields, such as catalysis, energy conversion, and biomedicine. An interesting approach to unravel the complexity of real systems and obtain an improved understanding of cerium oxide-based materials is represented by the study of model systems in the form of epitaxial ultrathin films or nanostructures supported on single crystalline substrates. These materials often show interesting novel properties, induced by spatial confinement and by the interaction with the supporting substrate, and their understanding requires the use of advanced experimental techniques combined with computational modeling. Recent experimental and theoretical studies performed within this field are examined and discussed here, with emphasis on the new perspectives introduced in view of the optimization of cerium oxide-based materials for application in different fields.

Ripples, strain, and misfit dislocations: structure of graphene-boron nitride superlattice interfaces

In recently synthesized two-dimensional superlattices of graphene and boron nitride, the atomic structure of the interface is complicated by a 2% lattice mismatch between the two materials. Using atomistic and continuum analysis, we show that the mismatch results in a competition between two strain-relieving mechanisms: misfit dislocations and rippling. For flat superlattices, beyond a critical pitch the interface is decorated by strain-relieving misfit dislocations. For superlattices that can deform out-of-plane, optimal ripple wavelengths emerge.

Effect of interface atomic structure on the electronic properties of nano-sized metal-oxide interfaces

We report that the size dependence of electronic properties at nanosized metal-semiconducting oxide interfaces is significantly affected by the interface atomic structure. The properties of interfaces with two orientations are compared over size range of 20-200 nm. The difference in interface atomic structure leads to electronic structure differences that alter electron transfer paths. Specifically, interfaces with a higher concentration of undercoordinated Ti result in enhanced tunneling due to the presence of defect states or locally reduced tunnel barrier widths. This effect is superimposed on the mechanisms of size dependent properties at such small scales.

Interface structure in Cu/Ta2O5/Pt resistance switch: a first-principles study

The interface structures of a Cu/Ta2O5/Pt resistance switch under various oxidation conditions have been examined from first-principles. The O-rich Cu/Ta2O5 interface is found to be stable within a wide range of O chemical potentials. In this interface structure, a considerable number of interface Cu atoms tend to migrate to the amorphous Ta2O5 (a-Ta2O5) layer, which causes the formation of the Cu2O layer. The interface Cu atoms become more ionized with an increase in the interface O concentration and/or temperature. These ionized Cu(+) ions could function as one of the main sources for the formation of conduction filaments in the Cu/a-Ta2O5/Pt resistance switch. In contrast, the ionization of the interface Cu atoms is not observed in the Cu/crystal-Ta2O5 interface primarily due to the much lower Cu ionic conductivity in crystal-Ta2O5 than that in amorphous state. In addition, the Pt electrode could not be ionized, irrespective of the interface O concentration and temperature. The formation of interface O vacancies in Pt/Ta2O5 is always energetically more stable than that in Cu/Ta2O5, which may be partly responsible for the cone shape of conduction filament formed in the Cu/a-Ta2O5/Pt resistance switch, where the base of the cone lies on the Pt/Ta2O5 interface.

A general method to determine twinning elements

The fundamental theory of crystal twinning has been long established, leading to a significant advance in understanding the nature of this physical phenomenon. However, there remains a substantial gap between the elaborate theory and the practical determination of twinning elements. This paper proposes a direct and simple method - valid for any crystal structure and based on the minimum shear criterion - to calculate various twinning elements from the experimentally determined twinning plane for Type I twins or the twinning direction for Type II twins. Without additional efforts, it is generally applicable to identify and predict possible twinning modes occurring in a variety of crystalline solids. Therefore, the present method is a promising tool to characterize twinning elements, especially for those materials with complex crystal structure.