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Phonon diffraction and interference patterns are observed at the atomic scale, using molecular dynamics simulations in systems containing crystalline silicon and nanometric obstacles, such as voids or amorphous inclusions. The diffraction patterns due to these nano-architectured systems of the same scale as the phonon wavelengths are similar to the ones predicted by the simple Fresnel–Kirchhoff integral. The few differences between the two approaches are attributed to the nature of the interface and the anisotropy of crystalline silicon. Based on the wave description of phonons, these findings can provide insights into the interaction of phonons with nano-objects and can have applications in smart thermal energy management. [ABSTRACT FROM AUTHOR]

Amorphous titanium dioxide (a-TiO2) is widely used as a coating material in applications such as electrochemistry and self-cleaning surfaces where its interface with water has a central role. However, little is known about the structures of the a-TiO2 surface and aqueous interface, particularly at the microscopic level. In this work, we construct a model of the a-TiO2 surface via a cut-melt-and-quench procedure based on molecular dynamics simulations with deep neural network potentials (DPs) trained on density functional theory data. After interfacing the a-TiO2 surface with water, we investigate the structure and dynamics of the resulting system using a combination of DP-based molecular dynamics (DPMD) and ab initio molecular dynamics (AIMD) simulations. Both AIMD and DPMD simulations reveal that the distribution of water on the a-TiO2 surface lacks distinct layers normally found at the aqueous interface of crystalline TiO2, leading to an ∼10 times faster diffusion of water at the interface. Bridging hydroxyls (Ti2–ObH) resulting from water dissociation decay several times more slowly than terminal hydroxyls (Ti–OwH) due to fast Ti–OwH2 → Ti–OwH proton exchange events. These results provide a basis for a detailed understanding of the properties of a-TiO2 in electrochemical environments. Moreover, the procedure of generating the a-TiO2-interface employed here is generally applicable to studying the aqueous interfaces of amorphous metal oxides. [ABSTRACT FROM AUTHOR]

The degradation of microplastics in relation to marine pollution has been receiving increasing attention. Because the spherulites that comprise microplastics have a highly ordered lamellar structure, their decomposition is thought to involve a lamellar structure collapse process. However, even in the simplest case of an order–disorder transition between lamellae and melt upon heating, the microscopic details of the transition have yet to be elucidated. In particular, it is unclear whether nucleation occurs at defects in the crystalline portion or at the interface between the crystalline and amorphous portions. To observe the transition in molecular simulations, an approach that distinguishes between the crystalline and amorphous structures that make up the lamella is needed. Local order parameters (LOPs) are an attempt to define the degree of order on a particle-by-particle basis and have demonstrated the ability to precisely render complex order structure transitions during phase transitions. In this study, 274 LOPs were considered to classify the crystalline and amorphous structures of polymers. Supervised machine learning was used to automatically and systematically search for the parameters. The identified optimal LOP does not require macroscopic information such as the overall orientation direction of the lamella layers but can precisely distinguish the crystalline and amorphous portions of the lamella layers using only a small amount of neighboring particle information. [ABSTRACT FROM AUTHOR]

A major challenge with water splitting technology is to develop highly active and stable electrocatalysts for the oxygen evolution reaction (OER). IrO2 – based electrocatalysts are one of the most active electrocatalysts for proton exchange membrane (PEM) electrolysers, due to their excellent activity for the OER in acidic conditions. However, IrO2 often suffers from dissolution during electrolysis due to phase transitions into more soluble forms. Herein, a range of electrodeposited IrO2 films annealed to different temperatures of up to 500°C are prepared to understand the influence that crystalline/amorphous interfaces have on performance during accelerated degradation tests in concentrated acidic solutions. This study showed that an IrO2 film annealed at 300 °C exhibited the highest catalytic activity with a low overpotential of 150 mV at 10 mA cm−2, the smallest Tafel slope of 51 mV dec−1, with a less progressive decay in activity over a period of 8 h of accelerated degradation testing. This contrasts with both fully amorphous or more crystalline IrO2 films that decayed much more rapidly within 1 h of testing indicating the role that amorphous/crystalline regions have on OER performance. [ABSTRACT FROM AUTHOR]

Interface engineering shows distinct advantages in the electrocatalytic hydrogen evolution reaction (HER) due to the unique structures that can be realized. The interfaces formed by amorphous materials often exhibit special properties that are beneficial for the HER. Herein, an amorphous/crystalline Rh(OH)3/CoP heterostructure is constructed, which exhibits outstanding HER performance in the all‐pH range. It only needs the overpotentials of 13, 12, and 25 mV to drive a current density of 10 mA cm−2 in alkaline, acidic, and neutral media, respectively, which ranks as one of the best HER electrocatalysts reported recently. The outstanding HER activities in the all‐pH range are attributed to the unique amorphous/crystalline heterostructure of Rh(OH)3/CoP, which possesses special hydrophilic/aerophobic features thataccelerate mass transfer, and provide abundant exposed active sites and appropriate defects. Importantly, the performance attenuation mechanism of the catalyst is also revealed, i.e., the formation of Rh aggregations leads to poor contact and efficacy loss of the amorphous/crystalline interface for HER. In short, this work provides a new idea for using amorphous/crystalline heterostructure to design electrocatalysts, not only for the HER, but also for the oxygen reduction and oxygen evolution reactions. [ABSTRACT FROM AUTHOR]

The technological advances in wearable electronics and military stealth have spawned extensive research into electromagnetic wave absorbents. Despite the rapid progress in the geometrical modulation of magnetic absorbents, the engineering strategy of microwave-responsive magnetic domains is underdeveloped and the response dynamics remain unclear. Herein, a surface finite-sized atom reconstruction procedure is proposed to accurately modulate the local magnetic topological domains, dramatically enhancing the magnetic loss capacity. Due to the selectivity of atom reconstruction, vortex and stripe domains are controllably hybridized around the porous surface to broaden the interactive domain region, significantly intensifying energy absorption of the microwave field. Meanwhile, the amorphous/crystalline interfaces around atom reconstruction regions can induce interfacial polarization, enabling the optimization of dielectric loss capacity. Therefore, a satisfactory magnetic-dielectric synergy is realized to demonstrate the strong absorption intensity of-31.2 dB and the broad absorption bandwidth of 5.9 GHz. Furthermore, the surface-based magnetic domain transformation and microwave energy attenuation mechanisms are thoroughly revealed to break the black box of structure-function through electron holography and micromagnetic simulation. These achievements demonstrate a promising solution to improve high-frequency magnetic properties and provide a feasible route to interpret the structure-relevant magnetic loss capacity. [ABSTRACT FROM AUTHOR]

The influence of uniaxial elastic strain of the Ni lattice on the intensity of mutual diffusion at a solid–liquid contact of Ni and Al has been studied by the molecular dynamics method. In all the cases under consideration, the intensity of diffusion has been found to increase and decrease upon extension and compression, respectively, which is related to a corresponding change in the free volume affecting to a great extent the diffusion mobility of atoms. It has been established that the intensity of mutual diffusion in the case of the (111) interface orientation relative to the Ni lattice is higher in comparison with the (001) orientation. This difference is explained by the different energies of Ni atoms in the aluminum phase and incorporated in the interface of crystalline nickel for both cases. [ABSTRACT FROM AUTHOR]

Nanofibrillated cellulose (NFC) consists of ultrafine cellulose structures in which the fibrils can have widths in the range from about 5 to 100 nm. NFC has been studied and developed in the paper industry, using bleached pulp from wood as the raw material. One of the issues in the application of NFC is their heat resistance to thermal degradation. The production process of NFC results in a decrease in their pyrolysis temperature during the nanofibrillation of bleached pulp; however, the details behind the reason and mechanisms are still unclear. In this study, NFC was prepared from bleached hardwood and softwood pulp by mechanical nanofibrillation using a grinder, and the pyrolysis behavior was investigated. For both bleached pulps, a decrease in the pyrolysis temperature was observed after nanofibrillation. The results suggest that the decrease in the pyrolysis temperature from nanofibrillation is not due to damage of the crystalline cellulose by nano fibrillation, but the damage of the hemicellulose components in the surface of the cellulose microfibrils or the interface between the crystalline cellulose and hemicellulose. If the hemicellulose on the surface of crystalline cellulose could be removed from the NFC, then the decrease in the pyrolysis temperature could be suppressed. [ABSTRACT FROM AUTHOR]

2H MoTe2 (molybdenum ditelluride) has generated significant interest because of its superconducting, nonvolatile memory, and semiconducting of new materials, and it has a large range of electrical properties. The combination of transition metal dichalcogenides (TMDCs) and two dimensional (2D) materials like hexagonal boron nitride (h-BN) in lateral heterostructures offers a unique platform for designing and engineering novel electronic devices. We report the fabrication of highly conductive interfaces in crystalline ionic liquid-gated (ILG) field-effect transistors (FETs) consisting of a few layers of MoTe2/h-BN heterojunctions. In our initial exploration of tellurium-based semiconducting TMDs, we directed our attention to MoTe2 crystals with thicknesses exceeding 12 nm. Our primary focus centered on investigating the transport characteristics and quantitatively assessing the surface interface heterostructure. Our transconductance (gm) measurements indicate that the very efficient carrier modulation with an ILG FET is two times larger than standard back gating, and it demonstrates unipolarity of the device. The ILG FET exhibited highly unipolar p-type behavior with a high on/off ratio, and it significantly increased the mobility in MoTe2/h-BN heterochannels, achieving improvement as one of the highest recorded mobility increments. Specifically, we observed hole and electron mobility values ranging from 345 cm2 V−1 s−1 to 285 cm2 V−1 s−1 at 80 K. We predict that our ability to observe the intrinsic, heterointerface conduction in the channels was due to a drastic reduction of the Schottky barriers, and electrostatic gating is suggested as a method for controlling the phase transitions in the few layers of TMDC FETs. Moreover, the simultaneous structural phase transitions throughout the sample, achieved through electrostatic doping control, presents new opportunities for developing phase change devices using atomically thin membranes. [ABSTRACT FROM AUTHOR]

During subduction, metamorphic dehydration reactions in the downgoing slab release fluids, generating fluid overpressure. It has been suggested that fluid is driven to flow upward by buoyancy, but a sufficiently high permeability allowing formation of a fluid percolation network is required. Traditionally, fluid percolation has been identified based on the textural equilibrium assumption by measuring the dihedral angle at the triple junction of grains. According to this theory, grain boundaries generally cannot be infiltrated by fluid, and only the grain edge can form a fluid flow channel. We argue that this theory is insufficient because we have found that water from fluid can be adsorbed into the crystalline interface, that is, a layered mineral interlayer, a crack, or a grain boundary. The high pressure in a subducting slab drives water adsorption into the crystalline interface, forming a low‐dimensional fluidic phase, and thus fluid percolation is achieved. Because water adsorbed in the interface is fluidic, water diffusion drives fluid transport in the subducting slab. Due to water adsorption, fluid overpressure at the dehydration front may release, so that dehydration embrittlement may be excluded. Stable water adsorption in the subduction‐slab conditions is determined here by combining molecular dynamics simulations and thermodynamic calculations. Analysis based on simulations shows that water adsorption requires crystalline surfaces which do not form hydrogen bonds well. Plain Language Summary: Fluids are released during dehydration reactions of hydrous minerals in downgoing slabs. As the density of fluid is smaller than that of rock, buoyancy drives the upward flow of the fluid. However, if fluid domains are isolated rather than well connected in porous rock, this fluid flow may be inhibited. The traditional textural equilibrium theory used to determine whether there is percolation of the fluid network excludes the infiltration of fluid into grain boundaries. However, here, we show that under high pressure, water from fluid can be adsorbed into a crystalline interface, forming a fluidic phase, and thus facilitating fluid percolation. The crystalline interface we study here is the interlayer of layered minerals, but in analogy, the understanding provided in this study can be generalized to other crystalline interfaces, for example, cracks or grain boundaries. If the crystalline surfaces do not form hydrogen bonds well, water adsorption can occur. Fluid migration in a slab is mediated by water within the crystalline interface. Water adsorption into crystalline interface may also play the role of transmitting earthquake‐triggering fluid overpressure, so that brittle failure may be excluded. Stable adsorption of water is identified here with a thermodynamic study based on atomic‐scale simulations. Key Points: Water from fluid can be adsorbed into crystalline interfaces under a high pressure, becoming a fluidic low‐dimensional phaseThis low‐dimensional phase facilitates fluid percolation and migration in a subducting slabWater adsorption into crystalline interface releases fluid overpressure, so that dehydration embrittlement may be excluded [ABSTRACT FROM AUTHOR]

Conducting oxide interfaces have attracted considerable attention, motivated by both fundamental science and potential for oxide electronic devices. An important gap for maturing such device technology is scalability and routes to control the electronic properties, which can narrow the device engineering space. Here, we demonstrate and explain the mechanisms of highly tunable conductive oxide interfaces. We synthesized amorphous--crystalline Al2O3/SrTiO3 interfaces using the scalable and industry-compatible atomic layer deposition (ALD) technique. An NH3 plasma pretreatment is employed in the ALD chamber, and its duration is used as a tuning parameter for the electrical properties, where a span of three orders of magnitude in the sheet resistance is observed at room temperature. For the most conductive sample, our results are comparable to the highest carrier density values reported for all-crystalline oxide interfaces prepared with state-of-the-art epitaxial growth techniques, such as pulsed laser deposition. We pinpoint the origin of conductivity to oxygen vacancies caused by the SrTiO3 reduction by the NH3 plasma pretreatment. These results present a simple, scalable, and industry-compatible route for realizing conductive oxide interfaces, with a broad parameter space, offering a versatile and flexible toolkit for oxide device engineering. [ABSTRACT FROM AUTHOR]

Phase-Change Materials (PCMs) are widely applied in dynamic optical modulation due to the dramatic changes in their complex refractive index caused by temperature variation. As the functionality varies, the application of a single PCM cannot meet the compact, efficient and broadband needs of optical modulators. In this work, we combine vanadium dioxide (VO2) and a chalcogenide (Ge2Sb2Te5 (GST) or In3SbTe2 (IST)) to obtain a VO2–GST/IST multiple-stack film that is optimized by a genetic algorithm. This film has a wide spectrum and high modulation properties with three self-switchable modes varied by temperature, including transmission, absorption and reflection. The optimal results are an average normal transmittance, absorbance, and reflectance of 0.76, 0.91, 0.86 in 3–5 μm and 0.72, 0.90, 0.90 in 8–14 μm under different temperature ranges. The film enhances the transmission and absorption properties due to the formation of anti-reflective coating and Fabry–Perot resonance. Compared with GST, the film maintains high reflectance due to the metal-like interface reflection of crystalline IST, which exhibits metallic properties. For different polarization states, the film demonstrates great directional insensitivity when the incidence angles vary from 0° to 60°. The designed self-adaptive multistage infrared radiative thermo-optic modulator has promising implications for optical fuse, fiber-optic communication and energy storage fields. [ABSTRACT FROM AUTHOR]

We report different growth modes and corresponding magnetic properties of thin EuSe films grown by molecular beam epitaxy on BaF2, Pb1−xEuxSe, GaAs, and Bi2Se3 substrates. We show that EuSe grows predominantly in the (001) orientation on GaAs(111) and Bi2Se3, but along the (111) crystallographic direction on BaF2 (111) and Pb1−xEuxSe (111). High resolution transmission electron microscopy measurements reveal a sharp and highly crystalline interface for both (001) and (111) EuSe films. In agreement with previous studies, ordered magnetic phases include antiferromagnetic, ferrimagnetic, and ferromagnetic phases. In contrast to previous studies, we found a strong hysteresis of the antiferromagnetic–ferrimagnetic transition. The ability to grow epitaxial films of EuSe on Bi2Se3 and of Bi2Se3 on EuSe enables further investigation of interfacial exchange interactions between various phases of an insulating metamagnetic material and a topological insulator. [ABSTRACT FROM AUTHOR]

The interfacial stiffness for nematic–smectic B (nm–smB) interface in a liquid crystalline (LC) material is calculated using Capillary Wave Theory (CWT) and molecular dynamics simulations. The Gay–Berne (GB) pair potential with parameters κ, κ′, μ, and ν equal to 3, 5, 2, and 1 is used to model the LC material. Using a smart three-step recipe, we have obtained an nm–smB phase coexistence in our simulations where the nm and smB directors are nearly parallel to each other and perpendicular to the interface normal. The density profiles are used to compute the nm–smB coexisting density range, the interfacial width, and its position. The smectic phase is differentiated from the nematic phase by using the local bond order parameter (q6q6), which has helped us to demonstrate that the interface is indeed rough. Finally, the interfacial stiffness of the nm–smB interface is computed by following the CWT analysis and is found to be γ ̃ n m − s m B = 0.398 61 k B T / σ e e 2 = 0.044 29 / σ s s 2 , where σee and σss are the length and diameter of the GB LC particles. [ABSTRACT FROM AUTHOR]

The 5d two‐dimensional electron gas (2DEG) based on KTaO3 (KTO) exhibits a lot of exotic properties such as stronger spin‐orbit coupling (SOC) and higher superconductivity transition temperature than those of SrTiO3 (STO)‐based 3d 2DEGs, whereas it has much lower electron mobility. Herein, the property of the 5d 2DEGs is investigated including the carrier mobility and Rashba SOC by interfacing both amorphous and crystalline STO with the crystalline KTO. Metallic 2DEGs are achieved at both interfaces of amorphous and crystalline STO‐capped KTO. Notably, the amorphous STO/KTO heterointerface has a larger carrier concentration and higher Hall mobility than the crystalline STO/KTO counterparts at low temperatures, which stems from two kinds of carriers. In contrast, the 5d 2DEG formed at the crystalline interface exhibits much stronger Rashba SOC as revealed through magnetotransport measurement. The deduced maximum strength of Rashba SOC and spin‐splitting energy are ≈8.56 × 10−12 eV m and ≈33.52 meV, respectively. Our results provide new insights on designing on‐demand properties of KTO‐based conducting interfaces. [ABSTRACT FROM AUTHOR]

Raman spectroscopy has proven its effectiveness as a highly informative and sensitive method for the nondestructive analysis of layered nanostructures and their interfaces. However, there is a lack of information concerning the characteristic phonon modes and their activity in Si/SiO2 nanostructures. In order to overcome this problem, the phonon states and Raman spectra of several Si/SiO2 superlattices (SL) with layer thicknesses varied within 0.5–2 nm are studied using DFT-based computer modeling. Two types of structures with different interfaces between crystalline silicon and SiO2 cristobalite were studied. A relationship between the phonon states of heterosystems and the phonon modes of the initial crystals was established. Estimates of the parameters of deformation potentials are obtained, with the help of which the shifts of phonon frequencies caused by elastic strains in the materials of the SL layers are interpreted. The dependence of intense Raman lines on the SL structure has been studied. Several ways have been proposed to use this information, both for identifying the type of interface and for estimating the structural parameters. The obtained information will be useful for the spectroscopic characterization of the silicon/oxide interfaces. [ABSTRACT FROM AUTHOR]

The oxide-semiconductor interface is a key element of MOS transistors, which are widely used in modern electronics. In silicon electronics, SiO2 is predominantly used. The miniaturization requirement raises a problem regarding the growing of heterostructures with ultrathin oxide layers. Two structural models of interface between crystalline Si and cristobalite SiO2 are studied by using DFT-based computer modelling. The structures of several Si/SiO2 superlattices (SL), with layer thicknesses varied within 0.5–2 nm, were optimized and tested for stability. It was found that in both models the silicon lattice conserves its quasi-cubic structure, whereas the oxide lattice is markedly deformed by rotations of the SiO4 tetrahedra around axes perpendicular to the interface plane. Based on the analysis of the calculated total energy of SLs with different thicknesses of the layers, an assessment of the interface formation energy was obtained. The formation energy is estimated to be approximately 3–5 eV per surface Si atom, which is close to the energies of various defects in silicon. Elastic strains in silicon layers are estimated at 5–10%, and their value rapidly decreases as the layer thickens. The elastic strains in the oxide layer vary widely, in a range of 1–15%, depending on the interface structure. [ABSTRACT FROM AUTHOR]

We investigate the magneto-optical (MO) polar Kerr enhancement of Fabry–Pérot cavities with perpendicular magnetic anisotropy for chemical and biological sensing applications. The MO cavities consist of stacked films with a half-mirrored surface layer, a dielectric interference layer, a total-reflection mirror, and a magnetic metal layer. Co80Pt20 and Al-doped ZnO (AZO) thin films were utilized as the magnetic and interference layers, respectively. The cavities produce two types of MO enhancement depending on the thickness of the magnetic layer. The sample with a thick magnetic layer as a total-reflection mirror generates a single peak in the polar Kerr spectrum. Contrarily, inserting a several-nanometer-thick CoPt layer into the AZO layer produces a resonant-type spectrum. Although both samples generate large MO enhancement factors (>50), the magnetic properties significantly differ. The AZO/CoPt/AZO interference layer controls the crystalline and interface conditions and produces a square-shaped out-of-plane hysteresis loop with a large Kerr rotation angle. Moreover, the use of an ultrathin CoPt film significantly reduces the saturation magnetization field. Thus, Fabry–Pérot cavities with a CoPt/AZO interference layer may serve as high-sensitivity, low-energy-consumption sensor elements. [ABSTRACT FROM AUTHOR]

Hydrogen evolution reaction (HER) is an important process in electrochemical energy technology, and efficient electrocatalysts are of great significance for renewable and sustainable energy conversion. Here, we report a facile hydrothermal and heat treatment process to synthesize a series of Pt-based nanocapsules (NCs) as an effective hydrogen evolution catalyst. The Pt/TeO x NCs exhibit excellent HER activity in an alkaline medium. The Pt/TeO x NCs only need the overpotential of 33 mV to achieve the current density of 10 mA cm−2, and the Tafel slope was as low as 29 mV dec−1, which was even better than that of commercial Pt/C. Detailed experimental characterizations demonstrate that the interface between the crystalline Pt/amorphous TeO x and the strong electron transfer contribute to alkaline HER activity. This work opens up a new direction for the preparation of efficient catalysts for electrocatalytic reactions or other conversion filed. The Pt/TeO x NCs with Pt clusters anchored on TeO x amorphous substrate were successfully prepared. The overpotential was only 33 mV at the current density of 10 mA cm−2 and the Tafel slope was as low as 29 mV dec−1, which was significantly better than that of commercial Pt/C. The excellent HER performance may originate from the strong electronic interaction and optimized binding energy for intermediate. [Display omitted] • The Pt/TeO x NCs with Pt clusters anchored on TeO x amorphous substrate is reported. • The Pt/TeO x NCs exhibit excellent HER activity with low overpotential in 0.1 M KOH. • The presence of Pt-TeO x interface is conducive to improving alkaline HER activity. [ABSTRACT FROM AUTHOR]

OER (oxygen evolution reaction) is a critical reaction in several storage and conversion systems for renewable and clean electrochemical energies, including solar fuel devices, metal–air batteries, as well as regenerative fuel and water splitting cells. Regarding the shortcomings of OER, apart from the sluggish kinetics and high reaction overpotential, the reaction rate and overpotential are difficult to be optimized simultaneously. Herein, a novel hierarchical particle–sheet-structured Fe-doped NixP electrocatalyst is developed, which presents abundant interfaces between crystalline particle and amorphous sheet. The OER overpotential is reduced to 204 mV at 20 mA cm−2 current density, while it is reduced to 225 and 231 mV at 100 and 300 mA cm−2, respectively. The Fe-doped NixP electrocatalyst also shows fast reaction kinetics, whose Tafel slope is a remarkable 25 mV dec−1. For an electrolytic cell whose cathode and anode are Pt/C/NF and Fe–NixP/NF, respectively, a mere 1.446 V voltage is necessary to drive a 10 mA cm−2 current density for achieving overall water-splitting property. Notably, it also works stably at considerably high current densities of 500 and 1000 mA cm−2, representing high potential for commercial applications. [ABSTRACT FROM AUTHOR]

The modifying influence of aluminium phosphide to the morphology of primary Si and eutectic Si was investigated in hypereutectic Al-20Si alloys via adding Al-Cu-P master alloy (0.5, 1, 20 wt.%). Microstructural results showed when Al-Cu-P addition from 0 to 0.5%, primary Si phase decreases and eutectic Si phase size remains invariable; when addition higher than 0.5%, primary Si phase keeps invariable, eutectic Si phase size increases. To prove the nucleation effect of AlP on Si phase, interfacial properties of Si/AlP interface were investigated using first-principles calculations. Results showed the AlP(100)/Si(100) interface energy is between −1.45 J/m2 and −1.38 J/m2 for Al-terminated and P-terminated AlP model, both is much smaller than liquid Si/crystalline Si interface (0.34 J/m2), consolidates that AlP particles possess strong nucleation potency for Si phases. Therefore, the modifying influence of AlP to the morphology Si phase is well clarified as a function of AlP content in Al-20Si alloys. [ABSTRACT FROM AUTHOR]

The oxidation resistance and tribological behavior of CrAlN/SiN x multilayer films with different interface structures were investigated. The multilayer film exhibited better oxidation resistance than the monolithic CrAlN film after oxidation at 900 °C and 1000 °C for 10 h. The crystalline SiN x sublayer was beneficial to oxidation resistance at 900 °C in contrast to the trend observed after oxidation at 1000 °C. The stacking faults generated in the multilayer film were induced by the oxidation of SiN x. The diffusion mechanism changed from the outward diffusion of cations to an inward diffusion of anions when the temperature was increased to 1000 °C. The multilayer film with a crystalline interface exhibited lower coefficient of friction (COF) and better tribological properties than the CrAlN film and multilayer with an amorphous interface. [ABSTRACT FROM AUTHOR]

Hybrid inorganic–organic semiconductor (HIOS) interfaces are of interest for new photovoltaic devices operating above the Shockley–Queisser limit. Predicting energy band alignment at the interfaces is crucial for their design, but represents a challenging problem due to the large scales of the system, the energy precision required and a wide range of physical phenomena that occur at the interface. To tackle this problem, many‐body perturbation theory in the non‐self‐consistent GW approximation, orbital relaxation corrections for organic semiconductors, and line‐up potential method for inorganic semiconductors which allows for tractable and accurate computing of energy band alignment in crystalline van‐der‐Waals hybrid inorganic–organic semiconductor interfaces are used. In this work, crystalline tetracene physisorbed on the clean hydrogen‐passivated 1 × 2 reconstructed (100) silicon surface is studied. Using this computational approach, it is found that the energy band alignment is determined by an interplay of the mutual dynamic dielectric screening of two materials and the formation of a dipole layer due to a weak hybridization of atomic/molecular orbitals at the interface. The significant role of the exchange‐correlation effects in predicting band offsets for the hybrid inorganic–organic semiconductor interfaces is also emphasized. [ABSTRACT FROM AUTHOR]

The article presents a study which revealed the molecular details of the cellulose chain arrangements on the surfaces of individual cellulose nanocrystals (CNC) using atomic force microscopy (AFM) and molecular dynamics (MD) simulations. Topics discussed include structural characterization of CNCs, 3D-AFM characterization of hydration structures at CNC-water interfaces, and frequency modulation AFM experiments.

In order to investigate the synergistic effect of different deformation modes (dislocations and local atomistic rearrangements) on the strength of mixed crystalline and amorphous materials, tensile and compressive deformation analyses of a two-dimensional binary system with various microstructures is performed through molecular dynamics simulations. The binary system is composed of atoms with two different atomic radii. By varying the mixing ratio and the interaction force between different atoms, 66 binary system models with various structures are represented, and each model is classified into three categories, crystalline, amorphous, and mixed crystalline/amorphous, through structural analysis. Deformation analysis shows that the strength of the mixed crystalline/amorphous models tends to be weaker than that of the crystal and amorphous models. The is because the edge of the force chain in the amorphous phase appears at the crystalline/amorphous interface, where dislocation release from the interface to the crystalline phase occurs easily. [ABSTRACT FROM AUTHOR]

The initial stage of the hydrogen absorption/desorption process in ceramic electrodes is discussed in this work. The experiments were carried out at 25 °C in a concentrated alkaline medium. The electrodes were prepared using LaB 6 and LaBO 3. Pd nanoparticles were incorporated into the electrodes to activate them electrochemically. The results showed that the electrodes could absorb hydrogen electrochemically at room temperature. The LaBO 3 electrode showed better hydrogen absorption characteristics than LaB 6. The morphological and volumetric properties were crucial in achieving the hydrogen storage in the electrode. The discharge capacity was similar in both electrodes. However, the LaBO 3 electrode supplied more energy than the LaB 6 -based electrode. The charge absorption reaction prevailed in both electrodes instead of the hydrogen evolution reaction. The capability of the ceramic electrodes to absorb/desorb hydrogen electrochemically is controlled by the diffusion processes that occur at the electrode/electrolyte interface and the crystalline planes of the ceramic materials. • LaBO 3 powders were synthesized by combustion method. • Ceramic electrodes were fabricated using synthesized LaBO 3 and commercial LaB 6. • Pd/C activated the ceramic electrodes. • Electrochemical techniques evaluated the hydrogen absorption in ceramic electrodes. • Ceramic hydrides absorbed and desorbed energy electrochemically. [ABSTRACT FROM AUTHOR]

Polymer materials with excellent physicochemical and electrical properties are desirable for energy storage applications in advanced electronics and power systems. Here, Al2O3@ZrO2 nanoparticles (A@Z) with a core-shell structure are synthesized and introduced to a P(VDF-HFP) matrix to fabricate P(VDF-HFP)/A@Z nanocomposite films. Experimental and simulation results confirm that A@Z nanoparticles increase the crystallinity and crystallization temperature owing to the effect of the refined crystal size. The incorporation of A@Z nanoparticles leads to conformational changes of molecular chains of P(VDF-HFP), which influences the dielectric relaxation and trap parameters of the nanocomposites. The calculated total trapped charges increase from 13.63 μC of the neat P(VDF-HFP) to 47.55 μC of P(VDF-HFP)/5 vol%-A@Z nanocomposite, indicating a substantial improvement in trap density. The modulated crystalline characteristic and interfaces between nanoparticles and polymer matrix are effective in inhibiting charge motion and impeding the electric conduction channels, which contributes to an improved electrical property and energy density of the nanocomposites. Specifically, a ~200% and ~31% enhancement in discharged energy density and breakdown strength are achieved in the P(VDF-HFP)/5 vol%-A@Z nanocomposite. [ABSTRACT FROM AUTHOR]

Reaching near-zero friction is one of the jewels on the crown of tribology, and structural superlubricity is a crucial mechanism to achieve it. Previous works focus mainly on the structural superlubricity at incommensurate crystalline interfaces. However, realizing such interfaces on a large scale without defects and contaminations is a formidable challenge. Here, we report a charge-induced robust macroscale superlubricity between graphite and atomically flat surfaces in the ambient condition. We transferred graphite flakes on Si 3 N 4 balls and used them to measure the friction properties on pristine and charged atomically flat surfaces such as 300 nm SiO 2 /Si and sapphire. We found that the surface charge can dramatically reduce the coefficient of friction between graphite and substrates by two orders of magnitude to 10−4, and the sliding is wearless even under harsh contact conditions (∼1.1 GPa center pressure and >100 m). We demonstrate that the surface charge is critical in achieving superlubricity possibly because it can reduce adhesion between graphite and substrate surfaces and make the substrate surfaces resistant to contaminations. Our method offers a ready-to-use solution to superlubricity alternative to achieve incommensurate crystalline interfaces. Thus, it can reduce the difficulty of realizing macroscale superlubricity for applications. [Display omitted] • The surface charge can reduce the coefficient of friction between graphite and atomically flat surfaces to 10−4. • The sliding between graphite and charged surfaces is wearless under harsh conditions (∼1.1 GPa center pressure, >100 m). • The surface charge can reduce the adhesion between graphite flake and substrate surface by 50%. [ABSTRACT FROM AUTHOR]

Skin effect that all eigenmodes within a frequency range become edge states is dictated by the topological properties of complex eigenvalues unique in non-Hermitian systems. The prevailing attempts to realize such a fascinating effect are confined to either one-dimensional or nonreciprocal systems exhibiting asymmetric couplings. Here, inspired by a recent model Hamiltonian theory, we propose a realistic reciprocal two-dimensional (2D) photonic crystal (PhC) system that shows the desired skin effect. Specifically, we establish a routine for designing such non-Hermitian systems via revealing the inherent connections between the nontrivial eigenvalue topology of order-2 exceptional points (EPs) and the skin effects. Guided by the proposed strategy, we successfully design a 2D PhC that possesses the EPs with nonzero eigenvalue winding numbers. The spectral area along a specific wavevector direction is then formed by leveraging the symmetry of the macroscopic geometry and the unit cell. The projected-band-structure calculations are performed to demonstrate that the desired skin effect exists at the specific crystalline interfaces. We finally employ time-domain simulations to vividly illustrate this phenomenon by exciting a pulse at the center of a finite-sized PhC. Our results form a solid basis for further experimental confirmations and applications of the skin effect. [ABSTRACT FROM AUTHOR]

At present, the purchasing prices for silicon-based photovoltaic modules with 20% efficiency and more are between 20 and 40 EURct/Wp. These numbers correspond to 40 to 80 EUR/m2 and are in the same range as the mounting costs (material prices plus salaries) of such modules. Installers and operators of photovoltaic systems carefully balance the module and mounting costs when deciding among modules of different efficiencies. This contribution emulates the installer's decision via a simple, analytical module mounting decision (Mo2De) model. A priori, the model, and the resulting conclusions are completely independent of the photovoltaically active material inside the modules. De facto, however, based on the present state (cost, efficiency, reliability, bankability, etc.) of modules fabricated from (single) crystalline Si cells, conclusions on other photovoltaic materials might also be drawn: On the one hand, the model suggests that lower-efficiency modules with efficiencies below 20% will be driven out of the market. Keeping in mind their installation costs, installers will ask for large discounts for lower-efficiency modules. Technologies based on organic semiconductors, CdTe, CIGS, and even multicrystalline Si, might not survive in the utility market, or in industrial and residential applications. Moreover, this 20% mark will soon reach 23%, and finally will stop at around 25% for the very best, large-area (square meter sized) commercial modules based on single crystalline silicon only. On the other hand, it also seems difficult for future higher-efficiency modules based on tandem/triple cells to compete with standard Si-based reference modules. Compared to their expected higher efficiency, the production costs of tandem/triple cell modules and, therefore, also their required markup in sales, might be too high. Depending on the mounting cost, the Mo2De-model predicts acceptable markup values of 1 EURct/Wp (for low mounting costs of around 10 EUR/m2) to 11 EURct/Wp (for high mounting costs of 100 EUR/m2) if the module efficiency increases from 23% to 30%. Therefore, a 23% to 24% module efficiency, which is possible with silicon cells alone, might be enough for many terrestrial photovoltaic applications. [ABSTRACT FROM AUTHOR]

The development of accident-tolerant materials is of great significance for preventing the zirconium–water reactions and improving the inherent safety of nuclear reactors. In this study, ZrC/Ni multilayers with average layer thicknesses of 5, 10, 20, 50, and 100 nm were designed and successfully fabricated by magnetron sputtering. The characterization results of GIXRD, SEM, AFM, TEM, etc., show that the series of films are mainly composed of alternately deposited Ni crystalline layers and ZrC amorphous layers, and the interface is clear. The films were irradiated with 50 keV He+ with a fluence of 1.0 × 1017 ions/cm2 at room temperature, and the films with different layer thicknesses kept the original phase composition. It was found that an amorphous transition layer with a thickness of about 30 nm appeared between the amorphous and crystalline interface of the 100 nm film by TEM characterization. The analysis shows that this layer is formed by the mixing of Ni and Zr elements induced by irradiation, which is not conducive to He+ migration and produces large-sized helium bubbles. The appearance of the transition layer improves the irradiation stability of the amorphous/crystalline composite film, thus providing a theoretical basis for the application of this type of material in fuel cladding. [ABSTRACT FROM AUTHOR]

In this work, the epitaxial semipolar (11–22) AlN was prepared on nonpolar m-sapphire substrate by combining sputtering and high-temperature annealing. According to our systematic measurements and analysis from XRD, Raman spectra, and AFM, the evolution of crystalline structure and morphology was investigated upon increasing AlN thickness and annealing duration. The annealing operation intensively resets the lattice and improves the crystalline quality. By varying the film thickness, the contribution from the AlN-sapphire interface on crystalline quality and lattice parameters during the annealing process was investigated, and its contribution was found to be not so obvious when the thickness increased from 300 nm to 1000 nm. When the annealing was performed under durations from 1 to 5 h, the crystalline quality was found unchanged; meanwhile, the evolution of morphology was pronounced, and it means the crystalline reorganization happens prior to morphology reset. Finally, the annealing treatment enabled a zig-zag morphology on the AlN template along the sapphire [0001] direction in the plane, which potentially affects the subsequent device epitaxy process. Therefore, our results act as important experience for the semipolar nitride semiconductor laser device preparation, particularly for the epitaxy of microcavity structure through providing the crystalline evolution. [ABSTRACT FROM AUTHOR]

Direct wafer bonding of β-Ga2O3 and N-polar GaN at a low temperature was achieved by acid treatment and atmospheric plasma activation. The β-Ga2O3/GaN surfaces were atomically bonded without any loss in crystalline quality at the interface. The impact of post-annealing temperature on the quality of bonding interfaces was investigated. Post-annealing at temperatures higher than 700 °C increases the area of voids at bonded interfaces probably due to the difference in the coefficient of thermal expansion. The integration of β-Ga2O3 on the GaN substrate achieved in this work is one of the promising approaches to combine the material merits of both GaN and Ga2O3 targeting the fabrication of novel GaN/β-Ga2O3 high-frequency and high-power electronics as well as optoelectronic devices. [ABSTRACT FROM AUTHOR]

Colloidal nanocrystals of metals, semiconductors, and other functional materials can self-assemble into long-range ordered crystalline and quasicrystalline phases, but insulating organic surface ligands prevent the development of collective electronic states in ordered nanocrystal assemblies. We reversibly self-assembled colloidal nanocrystals of gold, platinum, nickel, lead sulfide, and lead selenide with conductive inorganic ligands into supercrystals exhibiting optical and electronic properties consistent with strong electronic coupling between the constituent nanocrystals. The phase behavior of chargestabilized nanocrystals can be rationalized and navigated with phase diagrams computed for particles interacting through short-range attractive potentials. By finely tuning interparticle interactions, the assembly was directed either through one-step nucleation or nonclassical two-step nucleation pathways. In the latter case, the nucleation was preceded by the formation of two metastable colloidal fluids. [ABSTRACT FROM AUTHOR]

The focus of this investigation is the interface regions in crystalline Fe-nanoparticles as well as amorphous nanograins with an average grain size of about 4 nm. The iron nanograins have been compacted under external pressure; the resulting region of the contact between the grains is called an interface. It was found that the interface was three-dimensional with an atomic order different from that present in the neighboring nanograins. The structure of the interfacial region between adjacent amorphous grains has been found to be similar to those in crystalline Fe-nanograins. In other words, the structure of the interface formed under external pressure is independent of the structure of the adjacent grains. The effect of the structure of the interfaces on the magnetic hyperfine interactions and the magnetic moments is studied. In addition, the atomic structures of the interfaces have been studied by means of synchrotron high energy X-ray diffraction. The results obtained are presented in the form of radial distribution functions suggesting the following atomic structure of interfaces: (1) a short-range order of clusters with distorted bcc cells and (2) a middle-range (mesoscopic) order different from that of the bcc cells. [ABSTRACT FROM AUTHOR]

Phase‐change material (PCM) devices are one of the most mature nonvolatile memories. However, their high power consumption remains a bottleneck problem limiting the data storage density. One may drastically reduce the programming power by patterning the PCM volume down to nanometer scale, but that route incurs a stiff penalty from the tremendous cost associated with the complex nanofabrication protocols required. Instead, here a materials solution to resolve this dilemma is offered. The authors work with memory cells of conventional dimensions, but design/exploit a PCM alloy that decomposes into a heterogeneous network of nanoscale crystalline domains intermixed with amorphous ones. The idea is to confine the subsequent phase‐change switching in the interface region of the crystalline nanodomain with its amorphous surrounding, forming/breaking "nano‐bridges" that link up the crystalline domains into a conductive path. This conductive‐bridge switching mechanism thus only involves nanometer‐scale volume in programming, despite of the large areas in contact with the electrodes. The pore‐like devices based on spontaneously phase‐separated Ge13Sb71O16 alloy enable a record‐low programming energy, down to a few tens of femtojoule. The new PCM/fabrication is fully compatible with the current 3D integration technology, adding no expenses or difficulty in processing. [ABSTRACT FROM AUTHOR]

Mixtures of nonfullerene acceptors (NFAs) are prepared to fine‐tune bulk heterojunction (BHJ) thin‐film morphologies. The acceptor phase resulting from these mixtures has unique physical properties with excellent optoelectronic processes that dictate the output of organic photovoltaic (OPV) devices. Remarkable short‐circuit current densities (JSC) and fill factors (FFs) are achieved due to the formation of better crystalline fibrils that suppress geminate recombination, leading to improved charge transport with enhanced crystallinity and aligned cascading energy levels confirm efficient exciton diffusion and dissociation, yielding more effective exciton recycling. The decreased Urbach energy and suppressed energetic disorder account for the improvement in the open‐circuit voltage (VOC). A maximum power conversion efficiency of 17.86% is obtained, underscoring the importance of using specific material interactions to produce a suitable morphology and manage energy loss, resulting in ideal organic solar cell (OSC) devices. [ABSTRACT FROM AUTHOR]

The issue of accumulated seashell waste has been increasingly addressed in the studies of its applicability as a secondary source of calcium carbonate. In this work, the mechanism of the thermo-oxidative degradation of two types of mollusk shells (Dosinia exoleta—DE and oyster Ostrea edulis—OE) was investigated using simultaneous thermal analysis. Physicochemical characterization of raw and calcined materials was performed by XRD and SEM techniques. Results show that increasing powder particle size and heating rate affect the degradation of investigated shells differently and have a significant contribution to released quantities of CO2. It was proposed that the calcination rate of DE powders is determined by the strain-induced collapse of CO2-deficient calcite at its interface with crystalline CaO rods-like structure, with simultaneous expulsion of CO2. A much higher CO2 concentration was identified during the degradation of OE powders, favoring the carbonation reaction and, consequently, increasing the temperature and activation energy of the investigated reaction. Under elevated CO2 concentration, the CaO aggregation step is enhanced by slower reaction kinetics at lower temperatures since both CO2 desorption and structural transformations are probably hindered. The proposed mechanism leads to a meaningful correlation between thermodynamic quantities (enthalpy–entropy compensation) in the form of an iso-kinetic relationship. [ABSTRACT FROM AUTHOR]

[Display omitted] • Crystalline Ni(OH) 2 /Amorphous NiMoS electrocatalyst were designed and synthesized by two-step hydrothermal process. • The as-obtained material shows excellent hydrogen evolution over all pH ranges. • The synergistic mechanism and the role of crystalline Ni(OH) 2 and amorphous NiMoS was elucidated. Designing and fabricating efficient electrocatalysts is a practical step toward the commercial application of the efficient hydrogen evolution reaction (HER) over all pH ranges. Herein, novel Ti@Ni(OH) 2 -NiMoS heterostructure with interface between crystalline Ni(OH) 2 and amorphous NiMoS was rationally designed and fabricated on Ti mesh (denoted as Ti@Ni(OH) 2 -NiMoS). Acid etching and calcination experiments helped in accurate elucidation of the synergistic mechanism as well as the vital role on crystalline Ni(OH) 2 and amorphous NiMoS. In acidic solutions, the HER performance of Ti@Ni(OH) 2 -NiMoS was mainly attributed to the amorphous NiMoS. In neutral, alkaline, and natural seawater solutions, the HER performance was mainly determined by the synergistic interface behaviors between the Ni(OH) 2 and NiMoS. The crystalline Ni(OH) 2 accelerated water dissociation kinetics, while the amorphous NiMoS provided abundant active sites and allowed for fast electron transfer rates. To deliver current densities of 10 mA·cm−2 in acidic, neutral, alkaline, and natural seawater solutions, the Ti@Ni(OH) 2 -NiMoS required overpotentials of 138, 198, 180 and 371 mV, respectively. This paper provides general guidelines for designing efficient electrocatalyst with crystalline/amorphous interfaces for efficient hydrogen evolution over all-pH ranges. [ABSTRACT FROM AUTHOR]

• The effect of cavities on recrystallization growth in SiC was investigated. • The formed cavities can retard the epitaxial growth. • Nanocrystalline SiC was observed in the cavity layer. The effect of cavities on recrystallization growth of amorphous SiC induced by a high fluence He implantation was investigated. 300 keV He ions were used to implant the 6H-SiC (0001) wafer to a fluence of 4.4 × 1017/cm2 at room temperature. A buried amorphous layer with a width of approximately 468 nm was formed. Moreover, many spherical bubbles with diameters over 25 nm were observed by transmission electron microscopy. Recrystallization of the buried amorphous layer was visible after 900 °C annealing for 30 min. Some irregular cavities were found in the damaged layer. The recrystallization started from the amorphous/crystalline interface, and the formed cavities retarded the epitaxial growth. Nanocrystalline SiC was formed in the cavity layer. Extended defects were also characterized by transmission electron microscopy. The research results will give an insight into the recrystallization process in amorphous SiC. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are performed to investigate the effect of the interface structure, diffusion time and diffusion temperature on the diffusion behavior and amorphization mechanism of the dual-phase Mg alloys. The results indicate that there is a critical concentration of Y element in the amorphous/crystalline interface (ACI), which depends on the interface structure and temperature. And when the concentration of Y atoms in the ACI is higher than the critical concentration, the ACI will migrate towards the crystalline side, accompanied by the amorphization of the crystalline layer. In addition, it is found that the presence or absence of Y element in the amorphous layer has a significant impact on the amorphous layer thickness of the alloys. For the alloys containing Y atoms, the amorphous layer thickness increases with the increase of diffusion temperature and diffusion time. [ABSTRACT FROM AUTHOR]

A novel electrocatalyst containing amorphous FeSeO x and Mo doped NiSe 2 (denoted as FeSeO x /Mo-NiSe 2) was developed via pseudocrystalline replication method and selenization treatment, and heteroatom doping and amorphous and crystalline (a-c) interface enables attractive OER performances. [Display omitted] • A novel FeSeO x /Mo-NiSe 2 electrocatalyst was desinged for water oxidation. • The optimized FeSeO x /Mo-NiSe 2 exhibits a low overpotential of 205 mV at 10 mA cm−2 for OER in alkaline solution. • The excellent performance is attributed to amorphous and crystalline (a-c) interface engineering and heteroatom doping strategies. Exploring integrated regulation strategies to boosting electrocatalytic performance is essential to design more efficient and inexpensive OER catalysts. Herein, amorphous and crystalline (a-c) interface engineering and heteroatom doping are integrated to construct a novel electrocatalyst containing amorphous FeSeO x and crystalline Mo-doped NiSe 2 (denoted as FeSeO x /Mo-NiSe 2) via pseudocrystalline replication method and selenization treatment. The resultant FeSeO x /Mo-NiSe 2 electrocatalyst with 3D hierarchical nanoarchitectures of nanorod arrays covered by interlocking nanoblocks exposes more active sites and accelerated reaction kinetics. Furthermore, a-c interface engineering and heteroatom doping can synergistically enhance the intrinsic activity and charge transfer capability of NiSe 2 by decreasing the electron diffusion distance and flexibly modulating the electronic structure, which contributes to boost the oxygen evolution reaction (OER) performance. Consequently, the obtained FeSeO x /Mo-NiSe 2 achieves a low overpotential of 205 mV at 10 mA cm−2, which outperforms many other transitions metal selenides electrocatalysts. Density functional theory (DFT) calculations demonstrate that the formation of an internal electric field between FeSeO x and Mo-NiSe 2 accelerates charge transport and optimizes the adsorption/desorption of oxygen-containing intermediates, thereby accelerating the reaction kinetics and improving the OER performance. This work serves as a point of reference for designing innovative metal selenides based electrocatalysts combining a-c interface engineering and heteroatom doping. [ABSTRACT FROM AUTHOR]

Sodium ion batteries (SIBs) have garnered more and more attentions owing to the uneven distribution and increasing price of lithium mineral. Herein, BiVO 4 –V 2 C endogenous heterostructures as anode for SIBs are synthesized via one-step in situ hydrothermal method. The designed hydrangea-like heterostructure ensures a wide contact surface for the interaction of anode material with the electrolyte, and endows stable heterojunction interfaces between BiVO 4 and V 2 C MXene, the synergistic effect of which significantly improves the electrical conductivity, pseudo-capacitance and alleviates the volumetric change of BiVO 4 during charge/discharge process. Density functional theory (DFT) calculations ulteriorly demonstrate that the electric field at the BiVO 4 –V 2 C interface contributes to the excellent Na ion diffusion kinetics and impressive sodium storage capacity. As a result, the BiVO 4 –V 2 C anode achieved outstanding performance with a high discharge capacity (480 mAh g−1 after 600 cycles at 0.2 A g−1), and impressive long-term lifespan (303 mAh g−1 over 2000 cycles at 1 A g−1). This work reveals a new design of novel V 2 C MXene heterojunctions which coupling with BiVO 4 combined with the analysis of amorphous/crystalline interface, developing a proper strategy for the effective energy storage of sodium. An endogenous heterostructure of BiVO 4 coupled with V 2 C MXene (BiVO 4 –V 2 C) is developed via a one-step hydrothermal method. The designed hydrangea-like heterostructure provides a large surface area for the contact of the electrode material with electrolyte, and endows stable heterojunction interfaces between BiVO 4 and V 2 C, which significantly improves the reaction kinetics. [Display omitted] • Hydrangea-like endogenous BiVO 4 –V 2 C heterostructure is firstly reported. • Internal micro-electric field for improving Na+ migration and reaction kinetics. • The electrode delivers superior specific capacity and excellent cycle stability. • Endogenous heterostructure offers new insights for MXenes heterojunctions design. [ABSTRACT FROM AUTHOR]

Experiments have shown that high strength and high plastic stability are difficult to be simultaneously obtained in crystalline-amorphous layered composites. Here we report a complete suppression of plastic instability in a strong multilayered composite via nanoscale BCC Nb crystalline-amorphous CuNb interface architecting. Specifically, the size-dependent hardness and shear instability of the designed nanolayered composites are systematically investigated with individual layer thickness (h) ranging from 2 to 100 nm by nano/micro-indentation tests. A mechanics model is also proposed to quantify the shear instability. A non-monotonic shear instability behavior is revealed with decreasing h. When h > 40 nm, a cutting-like shear banding prevails in the composites and the shear instability reduces with decreasing h. Finally, a homogeneous plastic deformation without shear banding is achieved at h of 40 nm. For h < 40 nm, a kinking-like shear banding occurs in the composites and the shear instability increases with reducing h. Further theoretical analysis reveals a critical layer thickness for activating homogeneous deformation in the composites, i.e., 45 nm, above and below which the shear deformation would be dominated by cutting-like and kinking-like shear banding, respectively. The cutting-like shear banding is attributed to the propagation of the mature shear band formed in the amorphous phase that penetrates the crystalline layer. The homogeneous plastic deformation can be ascribed to the activation of the confined layer slip mechanism in the crystalline layer and the non-clustered shear transformation zones initiated in the amorphous layer. The kinking-like shear banding below 40 nm may originate from the cooperative kinking of the constituent layers with decreasing h. The potential advantage of the ductile BCC metals over FCC ones for suppression of shear instability in crystalline-amorphous composites is discussed based on the unique dislocation activities in nanoscale BCC crystals (e.g., self-multiplication and significant cross-slipping mechanisms). The present study sheds some light on designing strong and ductile crystalline-amorphous composites by selecting an appropriate BCC crystalline phase and an optimal interface spacing to eliminate plastic instability. • Shear instability of Nb/amorphous CuNb nanolayered composites is studied. • A mechanics model is proposed to quantify the shear instability. • A non-monotonic shear instability is discovered with decreasing layer thickness. • Shear instability is fully suppressed at 40 nm sample. • Cutting and kink-like shear bandings prevail respectively at large and small scales. [ABSTRACT FROM AUTHOR]

[Display omitted] • Anthracene-appended poly(ʟ-lactide)s (AAP) were synthesized by ROP of ʟ-lactide. • The excimer emission was observed in the low molecular weight AAP. • The monomeric emission is observed in amorphous and single crystals of AAP. • In crystallized AAP, fluorescence arises from anthracene excimers and monomers. • In the gel state AAP (e form), only the excimer emission was observed. The design and development of solid-state excimer-emitters bear great potential for attaining efficient solid-state luminescent materials. In this study, we have synthesized anthracene-appended poly(ʟ-lactide)s (AAPs) to regulate the arrangement of anthracene moieties by controlling the crystallization and polymorphic form of covalently linked poly(ʟ-lactide) (PLLA). In the high molecular weight AAP, the fluorescence intensity mainly arises from the monomeric anthracene moieties, whereas in the low molecular weight AAP, the excimer emission was observed depending on the structure and morphology of covalently-linked PLLA. The monomeric emission is predominantly observed in amorphous polymer due to the molecular level dispersion of covalently-linked anthracene moieties throughout the polymer matrix. When the polymer was crystallized under different conditions, covalently-linked anthracene moieties were excluded from polymer crystals or crystalline lamellae and are located on the surface or at the interface, which is advantageous for regulating the geometry of anthracene moieties. In the case of single crystals of PLLA, covalently-linked anthracene moieties assemble on the surface and emit mainly in their monomeric state due to the lack of π-stacking. In the melt-crystallized sample (α form), covalently-linked anthracene moieties reside at the interface of crystalline and amorphous domains by either dipolar interactions or π-stacking and fluorescence arising from anthracene excimers and monomers. In the gel state (ε form), only the excimer emission was observed due to the effective interactions between the anthracene moieties in the presence of excess solvent in the amorphous domains. In this way, polymer crystallization played a significant role in determining the arrangement of covalently-linked anthracene moieties in AAP. This study reveals the role of polymer crystallization on the excimer evolution in fluorophore-appended semicrystalline polymers and provides new insight into the design and development of fluorophore-appended polymers for optoelectronic devices. [ABSTRACT FROM AUTHOR]

• A method for developing models of realistic CASS microstructure is shown. • Simulated sound fields in CASS models agree well with experimental sound fields. • Simplified CASS models using Voronoi regions outperformed the realistic CASS models. • Large variations in echo amplitude were observed when randomizing the CASS model microstructure. Ultrasonic inspection of cast austenitic stainless steel (CASS) in the nuclear industry is particularly challenging because of sound field scatter and attenuation caused by the coarse-grained microstructure. Modeling and simulation are important tools in ultrasonic testing, as they can be used to help address key aspects of inspections, such as developing new probe designs, predicting inspection reliability, and testing phased-array focal laws. However, developing a useful and reliable CASS model is challenging due to the many grain interfaces and crystalline orientations that must be captured. We demonstrate a method of creating a realistic CASS model that is usable in CIVA, a commercially available modeling and simulation software platform. Using polished and chemically etched sections to highlight the grain structure and orientation, we generate models of a coarse-grained equiaxed specimen and a columnar specimen. We also test an alternative method of generating a coarse-grained model using Voronoi regions. We qualitatively compare sound field scatter and quantitatively compare sound field attenuation and beam partitioning in simulated sound fields to those of laboratory-measured sound fields. Results show that the Voronoi models perform as well as or better than the models based on actual grain morphology. We also show that model-to-model randomness in Voronoi grain structure can impact the magnitude of a simulated echo response by a factor of two or more. Although CASS models are potentially a good depiction of reality for a given scenario, they should not be considered representative since CASS morphology can change significantly from specimen to specimen or within the same specimen. [ABSTRACT FROM AUTHOR]

Bismuth telluride-based thermoelectric (TE) devices were widely used in waste heat recovery due to their high thermoelectric figure of merit (ZT), but the severe diffusion between Sn-based solder and TE pillar generated porous and brittle Sn-Te intermetallic compound (IMC), which seriously restricted the reliable service of devices. Ni-based coating was used but the thick Ni-Te IMC also impaired the properties of TE pillars. In this work, the crystalline Co-P coating was inserted between the p-type TE material Bi 0.5 Sb 1.5 Te 3 and the solder by electrodeposition, and the power generation sustainability of the TE pillar were significantly improved, and the mechanism was revealed. The microstructural characterization proved that the Co-P coating could effectively resist the diffusion of active Sn, Bi, Sb, Cu atoms. Co-P coating would provide support for the structural integrity and performance sustainability of TE pillars. It was worth noting that an ultrathin CoTe 2 IMC layer was formed between the Co-P coating and the Bi-Sb-Te pillar, which was much thinner than the Ni-Te IMC layer reported in the literature. This indicated that Co-P only consumed little thermoelectric elements, but also a good metallurgical bond was formed between the Co-P and the Bi-Sb-Te. After aging at 423 K for 150 h, the maximum output power and average Seebeck coefficient of the TE pillar without coating dropped significantly by 74% and 34%, respectively, and the internal resistance rose by 67%. Remarkably, the maximum output power and average Seebeck coefficient of the TE pillar protected by the Co-P coating only decreased by 14% and 5%, respectively, and the internal resistance only increased by 6%. [Display omitted] • Co-P coating showed a remarkable effect on the sustainability of TE power generation. • Co-P coating could effectively resist the diffusion of active Sn, Bi, Sb, Cu atoms. • An ultrathin CoTe 2 IMC layer was formed between the Co-P coating and the TE pillar. • Co-P coating consumed less thermoelectric elements than Ni-based coating. [ABSTRACT FROM AUTHOR]

[Display omitted] • The crystallization process of amorphous YAG oxide is investigated from an atomic point of view. • The crystallization proceeds on the surface and interior of the amorphous YAG separately, and which show the preferential crystallization of the surface atoms. • Some atoms in the amorphous phase were controlled by the periodic potential field of the crystal atoms and produced dynamically changing semi-ordered structures at the amorphous/crystalline interface with mainly concentrated within 1–2 nm from the interface. The transformation from amorphous materials to crystals and the corresponding microscopic mechanism have become a research focus in materials science, condensed matter physics, and biophysics etc. In this paper, taking Y 3 Al 5 O 12 (YAG) as an example, the crystallization process of amorphous YAG oxide is investigated from an atomic point of view through the combination of spherical aberration-corrected transmission electron microscopy (SCTEM) with an in situ heating method, and the morphology and structural evolution of the surface and interface are explored. It is observed that the crystallization proceeds on the surface and interior of the amorphous YAG separately. Through atomic-scale imaging, it is determined that semi-ordered structures are formed in a few atomic layers at the amorphous/crystalline interface and that the structural transformation process from the amorphous to the semi-ordered state and then to the crystal structure may be the main reason for the multiple stages of the crystallization of amorphous oxides. This study demonstrates the mechanism of the amorphous-to-crystal transformation on the atomic scale and contributes to gaining a better understanding of the crystallization process of bulk oxides, especially complex metal oxides. [ABSTRACT FROM AUTHOR]

Nano-porosity in amorphous Ge formed by swift heavy ion irradiation displays a peculiar self-organisation process. Initially almost randomly distributed pores grow with increasing irradiation fluence and segregate in layers orientated parallel to the sample surface. This self-organisation mechanism depends on the ion energy, thickness of the amorphous Ge layer and the angle of ion incidence and shows a characteristic length depending on ion energy and irradiation angle. Molecular dynamics simulations of individual ion tracks show that voids form due to the transition from the low-density amorphous to the high-density liquid phase, which also gives rise to a flow directed away from large pores and surfaces. The flow results in a characteristic distance from surfaces and larger pores, below which new voids do not form, and supports the formation of voids at the amorphous/crystalline interface. Simulations also demonstrate that, while direct impacts can reposition small voids, partial or nearby impacts promote their growth at the same location. These processes are plausible drivers for the self-organization. [Display omitted] [ABSTRACT FROM AUTHOR]

Making composites with crystalline inclusions can improve plasticity in brittle metallic glasses. In this study, we show a new metallic glass matrix composite designed with a gradient network architecture made of amorphous matrix regions and gradient crystalline network regions. Using molecular dynamics simulations, we validated theoretically the hypothesized concept of this new composite. Our results show that the unique microstructure leads to significant strain delocalization which can delay the generation of catastrophic shear bands. This is resulted from the new mechanism by both forming diffuse embryonic shear bands in the thin crystalline network interface and hindering or guiding their formation and movement in thick crystalline network regions with the presence of internal stresses generated from the gradient. This work demonstrates the synergistic effects induced by the heterogeneous gradient network design in the mechanical properties of metallic glass matrix composites and may open up exciting new possibilities. Macroscopic plasticity can be improved by spatially patterning heterogeneity into "microstructures" in the homogeneous structure-less amorphous metals. By further introducing gradients in the microstructure, we can elevate the improvement to a new level. Here, we show a new metallic glass matrix composite designed with a gradient network architecture made of amorphous matrix regions and gradient crystalline boundary network regions (a). The designed gradient structure can greatly enhance the plasticity as compared to the monolithic metallic glass (MG) and nanoglass (NG) (b). The new design of the MG composite creates a hierarchical heterostructure in the spatial pattern that can effectively cause delocalization of local shear (c) and the significant delay of brittle fracture. [Display omitted] [ABSTRACT FROM AUTHOR]