Narrow Results

After the parabolic equation method was initially applied to scalar wave propagation problems in ocean acoustics and seismology, it took more than a decade before there was any substantial progress in extending this approach to problems involving solid layers. Some of the key steps in the development of the elastic parabolic equation are discussed here. The first breakthrough came in 1985 with the discovery that changing to an unconventional set of dependent variables makes it possible to factor the operator in the elastic wave equation into a product of outgoing and incoming operators. This innovation, which included an approach for handling fluid-solid interfaces, was utilized in the first successful implementations of the elastic parabolic equation less than five years later. A series of papers during that period addressed the issues of accuracy and stability, which require special attention relative to the scalar case. During the 1990s, the self-starter made it possible to handle all types of waves, rotated rational approximations of the operator square root made it possible to handle relatively thin solid layers, and there was some progress in the accurate treatment of sloping interfaces. During the next decade, an improved formulation and approach for handling interfaces facilitated the treatment of piecewise continuous depth dependence and sloping interfaces. During the last 10 years, the accuracy of the elastic parabolic equation was improved and tested for problems involving sloping interfaces and boundaries, and this approach was applied to Arctic acoustics and other problems involving thin layers. After decades of development, the elastic parabolic equation has become a useful tool for a wide range of problems in seismology, seismo-acoustics, and Arctic acoustics, but possible directions for further work are discussed.

Flexible dielectric composites with high permittivity have been extensively studied due to their potential applications in high-density energy capacitors. In this review, effects of interface characteristics on the dielectric properties in the polymer-based nanocomposites with high permittivity are analyzed. The polymer-based dielectric composites are classified into two types: dielectric–dielectric (DD, ceramic particle-polymer) composites and conductor–dielectric (CD, conductive particle-polymer) composites. It is highly desirable for the dielectric–dielectric composites to exhibit high permittivity at low content of ceramic particles, which requires a remarkable interface interaction existing in the composite. For conductor–dielectric composites, a high permittivity can be achieved in composite with a small amount of conductor particle, but associated with a high loss. In this case, the interface between conductor and polymer with a good insulating characteristic is very important. Different methods can be used to modify the surface of ceramic/conductor particles before these particles are dispersed into polymers. The experimental results are summarized on how to design and make the desirable interface, and recent achievements in the development of these nanocomposites are presented. The challenges facing the fundamental understanding on the role of interface in high-permittivity polymer nanocomposites should be paid a more attention.

Large-size electronic-grade polycrystalline silicon is an important material in the semiconductor industry with broad application prospects. However, electronic-grade polycrystalline silicon has extremely high requirements for production technology and currently faces challenges such as carbon impurity breakdown, microstructure and composition nonuniformity and a lack of methods for preparing large-size mirror-like polycrystalline silicon samples. This paper innovatively uses physical methods such as wire cutting, mechanical grinding and ion thinning polishing to prepare large-size polycrystalline silicon samples that are clean, smooth, free from wear and have clear crystal defects. The material was characterized at both macroscopic and microscopic levels using metallographic microscopy, scanning electron microscopy (SEM) with backscattered electron diffraction (EBSD) techniques and scanning transmission electron microscopy (STEM). The crystal structure changes from single crystal silicon core to the surface of the bulk in the large-size polycrystalline silicon samples were revealed, providing a technical basis for optimizing and improving production processes.

This paper focuses on the problems encountered in the production process of electronic-grade polycrystalline silicon. It points out that the characterization of electronic-grade polycrystalline silicon is mainly concentrated at the macroscopic scale, with relatively less research at the mesoscopic and microscopic scales. Therefore, we utilize the method of physical polishing to obtain polysilicon characterization samples and then the paper utilizes metallographic microscopy, scanning electron microscopy-electron backscatter diffraction technology, and aberration-corrected transmission electron microscopy technology to observe and characterize the interface region between silicon core and matrix in the deposition process of electronic-grade polycrystalline silicon, providing a full-scale characterization of the interface morphology, grain structure, and orientation distribution from macro to micro. Finally, the paper illustrates the current uncertainties regarding polycrystalline silicon.

Electric-induced resistive switching effects have attracted wide attention for future nonvolatile memory applications known as resistive random access memory (RRAM). RRAM is one of the promising candidates because of its excellent properties including simple device structure, high operation speed, low power consumption and high density integration. The RRAM devices primarily utilize different resistance values to store the digital data and can keep the resistance state without any power. Recent advances in the understanding of the resistive switching mechanism are described by a thermal or electrochemical redox reaction near the interface between the oxide and the active metal electrode. This paper reviews the ongoing research and development activities on the interface engineering of the RRAM devices. The possible switching mechanisms for the bistable resistive switching are described. The effects of formation, composition and thickness of the interface layer on the resistive switching characteristics and consequently the memory performance are also discussed.

Nanoarchitectonics is the methodology for the architecture of nano-units of atoms, molecules, and nanomaterials to create functional material systems. This will integrate nanotechnology with other fields such as organic chemistry, supramolecular chemistry, material science, microfabrication technology, and bio-related sciences. Through this review, it is shown that nanoarchitectonics is important for the development of various functional materials. Porphyrins and their analogues are exemplified as important players in nanoarchitectonics strategies. The contents of this review can be briefly summarized as follows. First, recent examples of studies on porphyrins and their analogues, ranging from organic synthesis as basic research to biomedical applications as advanced usages, are presented. This demonstrates the broad utility of porphyrins as functional nano-units, from molecular nanoarchitectonics to material nanoarchitectonics. In subsequent sections, the organization and function of porphyrin assemblies by the Langmuir-Blodgett (LB) method and layer-by-layer (LbL) assembly are described as examples of nanoarchitectonics at interfaces. The creation of functional materials through nanoarchitectonics is rich in possibilities. Conversely, the wide range of possibilities may make it difficult to easily design and control. Confine the system from free three-dimensional space to a two-dimensional field such as an interface, and design, creation, and evaluation may become easier. The nanoarchitectonics of functional structures in a two-dimensional plane are also advantageous in terms of functional expression. The use of interfacial environments is an extremely powerful tool for creating functional systems through nanoarchitectonics.

Several methods for handling sloping fluid–solid interfaces with the elastic parabolic equation are tested. A single-scattering approach that is modified for the fluid–solid case is accurate for some problems but breaks down when the contrast across the interface is sufficiently large and when there is a Scholte wave. An approximate condition for conserving energy breaks down when a Scholte wave propagates along a sloping interface but otherwise performs well for a large class of problems involving gradual slopes, a wide range of sediment parameters, and ice cover. An approach based on treating part of the fluid layer as a solid with low shear speed is developed and found to handle Scholte waves and a wide range of sediment parameters accurately, but this approach needs further development. The variable rotated parabolic equation is not effective for problems involving frequent or continuous changes in slope, but it provides a high level of accuracy for most of the test cases, which have regions of constant slope. Approaches based on a coordinate mapping and on using a film of solid material with low shear speed on the rises of the stair steps that approximate a sloping interface are also tested and found to produce accurate results for some cases.

An emerging concept, nanoarchitectonics, is supposed to work on the preparation of functional materials systems from nanoscale components. Because porphyrin derivatives show their importance in many research targets, discussions on nanoarchitectonics with porphyrins and related molecules would provide meaningful opportunities to consider effective usages of the nanoarchitectonics. This review article explains various examples of nanoarchitectonics approaches with porphyrin derivatives. The examples are especially focused on two topics: (i) materials nanoarchitectonics for nanofibers, metal-organic frameworks, covalent organic frameworks, and hydrogen-bonded organic frameworks; (ii) interfacial nanoarchitectonics for surface monolayers (self-assembled monolayers), Langmuir-Blodgett films, and layer-by-layer assemblies. Functions and properties can be enhanced upon their organization in specific dimensions and arrangements in nanostructured frameworks. In many cases, interface-specific organization would lead to advanced performances with high efficiency and specificity. Even though only limited examples are described here, various possibilities are actually suggested. Not limited to porphyrin families, nanoarchitectonics for functional materials has to be considered with a wide range of materials.

Layered materials play a crucial role in numerous essential structures, including adhesive connections, composite laminates, and various electronic components. This work focuses on proposing a novel framework of algorithms to improve the adaptability of element-free Galerkin method for modeling fracture in bimaterials exposed to thermoelastic loads. A bimaterial fracture problem is modeled as a combination of both weak and strong discontinuities — strong discontinuity owing to the presence of crack and weak discontinuity due to inherent material discontinuities. Initially, three distinct methods, comprising domain partitioning, lagrange multiplier, and jump function have been employed for interface crack modeling and error norm is used as an indicator to select the optimum one. Second, a novel interface enrichment algorithm has been introduced to effectively model the interface with limited computational costs with higher accuracy. Owing to the applicability of bimaterials in numerous applications under a combination of thermal/mechanical loads, the proposed formulation has been utilized for modeling and simulating a diverse bimaterial thermoelastic fracture problems using the proposed framework. The mixed mode (complex) stress intensity factors (SIFs) are numerically examined using modified domain form of interaction integral. A good agreement of results with available results from literature extends the computational prowess of the proposed framework in modeling a variety of thermoelastic bimaterial problems accurately and swiftly as compared to conventional EFGM.

We have studied the superconductivity of Pb ultra-thin films with thickness from 1 monolayer (ML) to 7 ML grown on Si(111) by molecular beam epitaxy. In situ low temperature scanning tunneling spectroscopy (STS) and angle-resolved photoemission spectroscopy (ARPES) measurements were performed on the films. It is suggested that the interface effect plays a critical role in enhancing the electron-phonon coupling, which consequently increases the superconducting transition temperature when a film reaches to the two-dimensional limit.

Defects and stress distribution in the interface of Ge/Si hetero-structures play an important role in silicon-based semiconductor devices. This work at atomic scale performs molecular dynamics simulations to study the packing characteristics in the Ge/Si interface and loading features on the atoms for different contacting configurations between Ge nanopillars and Si substrates. Based on the analysis of energy, composition, the distribution of hydrostatic pressure, the Lode–Nadai parameters of each atom as well as visualized atomic packing images in the interface regions, simulation results show that contacting configurations of the Ge nanopillar with the (100) surface and the (110) surface of the Si substrate significantly affect the stability of the interface structures. The load-bearing positions of the Si surface and the inter-diffusion among the atoms in the interface regions greatly contribute to the lattice distortion of the silicon substrate, the composition, defects, and local stress distribution in the interface regions.

The poor stability of magnetic fluid is a key problem which limits its application. To understand the impact of surfactants on stability, we prepare kerosene-based magnetic fluid with Fe₃O₄ magnetic nanoparticles (MNPs) using different surfactants i.e. linoleic acid, oleic acid and stearic acid. The distribution of nanoparticles in magnetic fluid is obtained by transmission electron microscope (TEM) and granularity analyzer. We find that MNPs coated with stearic acid agglomerate and the size is the largest. In contrast, the MNPs coated with linoleic acid or oleic acid are well dispersed with smaller size, which reveals that the type of surfactant will affect the stability of the magnetic fluid. To understand this, the adhesion energy of surfactant on particles and the solvation energy of surfactant in carrier fluid are calculated by ab initio and molecular dynamics. Based on the calculation results, we propose a formula for estimating the stability of magnetic fluid by combining the repulsive energy between Fe₃O₄ nanoparticles covered by surfactant and the calculated solvation energy of surfactants and carrier fluid, which can well interpret our experimental results. Our study reveals the mechanism of magnetic fluid stability and provides theoretical guidance for the preparation of stable magnetic fluid.

In this study, molecular dynamics simulations were employed to investigate the effect of symmetrical tilt grain boundaries (STGBs) on the cascade collision evolution at the SiC/PyC interface. We observed that the tilt angle size of grain boundary (GB) spatial structures significantly influences both the type and number of defects caused by primary knock-on atom (PKA) collisions at the interface, altering the cascade damage morphology. Under the PKA range from 1.5keV to 15keV at 1000K, the interplay between GB and interface damage throughout various cascade collision stages impacts defect generation and PKA efficiency. Integrating the analyses of displacement cascade morphology, threshold displacement energy (TDE), and Frenkel pairs (FPs) evolution, it is evident that GBs introduced into the SiC/PyC interface with single crystals exhibit reduced defect absorption efficiency. This implies the existence of competing mechanisms of GB damage and interfacial damage. Notably, the GB plane near the interface exhibits enhanced irradiation resistance and atomic arrangement stability compared to areas without GB. Overall, our results offer crucial insights into the irradiation resistance mechanics of ceramic composite interfaces, laying the groundwork for future studies.

The paper discusses a unique technique developed initially at Nation Institute of Technology, Surat that is remodeled in real-world applications. The concept consists primarily of a user-friendly software facilitating direct communication with any intelligent or learning system/robot operating under known parameters of motor specifications. Any software base permitting high level PC interface without ASCII interrupt can be used for easy programming. This allows for a learning operation mode where a prevention of time lag is enabled by stored machine data, captured through movements such movements can be physically made or taught via programs to the device and such learning aspects make the machine more efficient where the robot can either perform individual actions as needed or learn new methods for the same results and can perform a series of actions continuously. Using the stored data, the machine is also capable of autonomous movements based on the path of least resistance as calculated by the time it takes to perform an act.

Interfacing Technique Tool Machining Robot (ITTMR) was developed as robotic tool holder that can determine the shape and size of different OCTG pipes utilized in the downhole industry and enable it to machine appropriate threads on the pipe with no manual intervention.

The process thereby completely negates any possibility of human error which can otherwise cause heavy loss on finished equipment that are rendered unusable because of threading errors on almost nearly finished complex milled parts or assemblies that are pending threads as the final operation. The purpose of the software codes is to provide a user-friendly GUI that can communicate with any machine by pulling in appropriate ACNC programs and performing the required tasks associated with the operating system and specifications of the motors/mobilization equipment’s used. For the purpose of this paper, the software code is not provided.

Any firmware base that permits the usage of an ASCII interrupt can be used and for the purpose of this operation, an RS323 equivalent board will also suffice for basic operations, however a complex ITTMR system has been utilized. This paper solely addresses the technique of how the threading operation is performed and does not address the process of how the pipe is bought to the machine or other associated aspects of the software to retain any possible patent applications on the same.

In this paper, the effects of rare earth elements on the bonding strength and stability of TiC/fcc-Fe interface are explored by using the first-principles method based on density functional theory. The results show that the Ti terminal is more stable than the C terminal in the process of forming the interface. The alloying elements tend to segregate at position 2 on the side of fcc-Fe. The segregation of Mo, Nb, Cr and Ce alloying elements increases the interatomic electron cloud enrichment and consumption between the interfaces and enhances the Fe–Ti interactions. The d orbitals of Mo, Nb, Cr and Ce and f orbitals of Ce have strong hybridization with Fe-d orbitals and Ti-d orbitals electrons near the Fermi energy level, indicating an increase in bonding strength and stability of the interfaces. When Fe atoms are replaced by W, Ni and Al atoms, the covalent bond strength between interfacial atoms is reduced, thus weakening the interfacial bonding strength. This provides solid theoretical foundation with regard to further application in austenitic heat-resistant steel fields.

The excellent photoelectric properties and low fabrication cost of perovskite solar cells have attracted extensive research attention. Despite this, long-term stability issues associated with perovskite solar cells continue to pose a significant barrier to commercialization. A new generation of two-dimensional (2D) and quasi-2D perovskites and newly introduced members of the 2D material family, have attracted growing attention due to their excellent stability and physical properties in contrast to their three-dimensional (3D) counterparts. Herein, we have presented the feasibility of using 4,$4^{\prime }$-dipyridyl as an additive material for quasi-2D perovskite solar cells. As a result of the addition of 4,$4^{\prime }$-dipyridyl, the solar cell device achieves a power conversion efficiency of 17.92% and a fill factor of 76.5%. Additionally, this strategy can be expanded to quasi-2D perovskite solar cells with an open-circuit voltage of 1.05V.

The nature of oxide phases at metal–oxide interfaces, i.e. of oxide layers in the proximity of a metal surface, is assessed by critically examining the available data in the literature. The data reveal a trend towards the formation of reduced oxide phases with lower oxidation states in the vicinity of the interface with a metal. The physical origin of these interface-stabilized oxide layers is discussed and the possible causes include strong metal–metal bonding, high oxygen affinity of the substrate metal, reduction of the interfacial strain, and the stability of two-dimensional oxide phases.

Facing the challenge of low energy density of conventional electric double layer supercapacitors, researchers have long been focusing on the development of novel pseudocapacitive electrode materials with higher energy densities. Since capacitive charge storage reaction mostly occurs on the interface of electrode and electrolyte, the interface chemistry determines the achievable power and energy densities of a supercapacitor. Consequently, understanding of surface–interface reaction mechanism is a key towards efficient design of high-performance supercapacitor electrode materials. In this paper, we have reviewed the recent advances in the understanding of surfaces–interfaces in the system of pseudocapacitive supercapacitors. With significant research advancements in the understanding of surface–interface of supercapacitors, novel colloidal electrode materials with improved surface–interface structures have been developed in our previous work, which have the potential to deliver both high energy and power densities. This review aims to provide an in-depth analysis on the surface–interface control approaches to improve the energy and power densities of supercapacitors.

The potential applications of diamond in the field of electronics working under high power and high temperature (aeronautic, aerospace, etc.) require highly oriented films on heterosubstrates. This is the key motivation of the huge research efforts that have been carried out during the last ten years. Very significant progress has been accomplished and nowadays diamond films with misorientations close to 1.5° are elaborated on β-SiC monocrystals. Moreover, an excellent crystalline quality with polar and azimuthal misalignments lower than 0.6° is reported for diamond films grown on iridium buffer layers. Unfortunately, these films are still too defective for high power electronics applications. To achieve higher crystalline quality, further improvements of the deposition methods are needed. Nevertheless, a deeper knowledge of the elemental mechanisms occurring during the early stages of growth is also essential. The first part of this paper focuses on the state of the art of the different investigated ways towards heteroepitaxy. Secondly, the present knowledge of the early stages of diamond nucleation and growth on silicon substrates for both classical nucleation and bias-assisted nucleation (BEN) is reviewed. Finally, the remaining questions concerning the understanding of the nucleation processes are discussed.

Granular materials as typical soft matter, their transport properties play significant roles in durability and service life in relevant practical engineering structures. Physico-mechanical properties of materials are generally dependent of their microstructures including interfacial and porous characteristics. The formation of such microstructures is directly related to particle components in granular materials. Understanding the interactive mechanism of particle components, microstructures, and transport properties is a problem of great interest in materials research community. The resulting rigorous component-structure-property relations are also valuable for material design and microstructure optimization. This review article describes state-of-the-art progresses on modeling particle components, interfacial and porous configurations and incorporating these internal structural characteristics into modeling transport properties of granular materials. We mainly focus on three issues involving the simulation for geometrical components, the quantitative characterization for interfacial and porous microstructures, and the modeling strategies for diffusive behaviors of granular materials. In the first aspect, in-depth reviews are presented to realize complex morphologies of geometrical particles, to detect the overlap between adjacent nonspherical particles, and to simulate the random packings of nonspherical particles. In the second aspect, we emphasize the development progresses on the interfacial thickness and porosity distribution, the interfacial volume fraction, and the continuum percolation of soft particles representing compliant interfaces and discrete pores. In the final aspect, a literature review is also provided on modeling of transport properties on the forefront of the effective diffusion and anomalous diffusion in multiphase granular materials. Finally, some conclusions and perspectives for future studies are provided.