Interface Model Research Articles

Revealing the adhesion, stability, and electronic structure of SiC/M (M=Au, Pt) interface: A first-principles study

The interface bonding and electronic properties between SiC and metal are the key factors affecting the physical transport phenomena of metal-semiconductor field-effect transistors (MESFETs). The work of adhesion, interface energy and electronic structure of SiC/M (M = Au, Pt) interface are explored by first-principles method. Forty possible interface models were constructed for different surfaces and stacking positions, and the four most stable interfaces were screened based on the work of adhesion and interface energy. Moreover, the interfacial bonding behavior and strength of SiC/M were quantitatively and qualitatively described through partial density of states (PDOS), crystal orbital Hamilton population curves (COHP), and charge density distribution (CDD). The PDOS demonstrated covalent bond characteristics between M − Si and M − C, which are primarily bonded by M-d and Si-p or C-p orbital hybridization. Further, the COHP and CDD analyses clearly manifested that the Pt–C bond at the interface exhibits more pronounced electron aggregation and greater bonding strength than the Au–C bond. This study offers a comprehensive understanding of the interfacial bonding strength between SiC and Au or Pt and demonstrate that SiC/Pt contact is the more favorable option for electronic device materials.

Experimental characterization and modelling of adhesive bonded joints under static and non-monotonic fracture loading in the mode II regime

Understanding and predicting the behaviour of bonded joints under different loading conditions is certainly an aspect of primary importance. Although numerous experimental studies have been carried out over the last few decades, the shear behaviour of bonded joints under cyclic loading has not been investigated in detail. To fill this gap, an extensive experimental and numerical program of double lap shear bonded joints has been carried out. The double lap shear joints were tested under static and cyclic loading to evaluate and compare the influence of external forces on the adhesive performance. The results are discussed in terms of the force-displacement relationship, shear stress, stiffness, residual displacement, and initial damage. Finally, a method is presented for predicting the actual behaviour of double lap shear bonded joints under different loading conditions using an imperfect interface model with damage evolution. The numerical results are in good agreement with the experimental results for all loading conditions. This work has provided and validated an interesting design tool for adhesive structures.

A 3-D phase field study of dielectric droplet impact under a horizontal electric field

A 3-D diffuse interface model has been developed to simulate impact of a dielectric droplet under the influence of a horizontal electric field. The Cahn-Hilliard equation, coupled with the Navier-Stokes equations, is employed to track liquid-gas interface. The model is discretized utilizing the finite difference method on a half staggered grid and solved using the projection method with the aid of OpenMP. Mesh independence test was also performed to choose an appropriate grid size. After validating the model, extensive simulations were conducted. The paper takes into account various factors influencing drop impact dynamics under real conditions, such as contact angle and impacting velocity. Numerical results show that for a moderate electric field, the electric force stretches a droplet in the direction of the applied electric field, and that a horizontal electric field can be useful to suppress splashing by reducing the rising angle made by the lamella with the substrate.

Numerical Modelling of Water Flashing at Sub-Atmopsheric Pressure with a Multi-Regime Approach

The CFD numerical study of the flash boiling phenomenon of a water film was conducted using an Euler–Euler method, and compared to the experiments on the flashing of a water film. The water film is initially heated at temperatures ranging from 34 to 74 ∘C (frim 1 to 41 ∘C superheat), and the pressure is decreased from 1 bar to 50 mbar during the experiments. This paper shows that the experiments could not be correctly modelled by a simple liquid/bubble model because of the overestimation of the drag force above the water film (in the gas/droplet region). The generalised large interface model (GLIM), however, a multi-regime approach implemented in the version 7.0 of the neptune_cfd software, is able to differentiate the water film, where liquid/bubble interactions are predominant from the gas region where gas/droplet interactions are predominant, and gives nice qualitative results. Finally, this paper shows that the interfacial heat transfer model of Berne for superheated liquids could accurately predict the evolution of the water temperature over time.

Influences of upsetting on the propagation characteristic of the elastic wave in the countersunk head riveted joints

The countersunk head riveted joints (CHRJ) have extensive use in the aerospace and marine industry. When testing the CHRJ with ultrasonic technology, the signal near the initial pulse cannot be used to detect near-surface defects due to the blind zone of the ultrasonic testing (UT). Moreover, the presence of clutters between the first and second bottom echoes can significantly affect the effectiveness of the UT. Therefore, it is crucial to investigate the propagation characteristic of ultrasonic waves in the CHRJ. The relationship between the interface stiffness and the upsetting length was obtained because of the multi-interface feature of the CHRJ. The propagation characteristic of ultrasonic waves in the CHRJ was investigated using the finite element simulation based on the spring model of the imperfect interface. The simulation results showed that shank echoes would generate at the surface of the rivet shank when the elastic wave propagates in the shank of the CHRJ. The shank echoes would propagate obliquely downward and reflect repeatedly on the surface of the rivet shank. Furthermore, the amplitude of the first shank echo would decrease with the increase of the upsetting length due to the increase of contact stress and deformation. To verify the simulation results, the experiments were carried out using the piezoelectric ultrasonic transducer, and the experimental results matched well with the simulation results. This paper can provide a reference for the ultrasonic testing of defects in the CHRJ.

Atomistic simulation of tribology behaviors of Ti-based FeCoNiTi high entropy alloy coating during nanoscratching

Molecular dynamics (MD) simulations are performed to investigate the nanoscale tribology behavior of Ti-based FeCoNiTi High-entropy alloy (HEA) coating through nanoscratching. Three coating interface models, (001)HEA||(0001)Ti, (001)HEA||(11 2‾ 0)Ti, and (001)HEA||(1 1‾ 00)Ti, are selected to explore the effects cutting depth (D) and cutting velocity (V) of abrasive particles during the nanoscratching process. The results show that the Ti-based HEA coating with the interface (001)HEA||(0001)Ti has the smallest coefficient of friction (COF) making it most suitable as the coating interface. The increase in V resulted in the increase of the frictional force influenced by the Other structure composed of disordered atoms. Due to the existence of multiple phase structures in the limited area of the coating, dislocation nucleation is difficult and disordered atoms are formed. This is different from the strengthening caused by dislocation accumulation in the scratching region. The HEA coating plays an effective role in protecting the pure Ti substrate. With the protection of HEA coating, dislocation slip and deformation twinning were not observed in the pure Ti substrate. However, dislocation slip are the main plastic deformation mechanisms of uncoated pure Ti. These findings provide a theoretical reference for upgrading the wear resistance of pure Ti with HEA coating and expands the area of application of pure Ti.

Polyalthic acid and oleoresin from Copaifera trapezifolia Hayne reduce Toxoplasma gondii growth in human villous explants, even triggering an anti-inflammatory profile

Due to the lack of efficient antiparasitic therapy and vaccines, as well as emerging resistance strains, congenital toxoplasmosis is still a public health issue worldwide. The present study aimed to assess the effects of an oleoresin obtained from the species Copaifera trapezifolia Hayne (CTO), and an isolated molecule found in the CTO, ent-polyalthic acid (ent-15,16-epoxy-8(17),13(16),14-labdatrien-19-oic acid) (named as PA), against T. gondii infection. We used human villous explants as an experimental model of human maternal-fetal interface. Uninfected and infected villous explants were exposed to the treatments; the parasite intracellular proliferation and the cytokine levels were measured. Also, T. gondii tachyzoites were pre-treated and the parasite proliferation was determined. Our findings showed that CTO and PA reduced efficiently the parasite growth with an irreversible action, but without causing toxicity to the villi. Also, treatments reduced the levels of IL-6, IL-8, MIF and TNF by villi, what configures a valuable treatment option for the maintenance of a pregnancy in an infectious context. In addition to a possible direct effect on parasites, our data suggest an alternative mechanism by which CTO and PA alter the villous explants environment and then impair parasite growth, since the pre-treatment of villi resulted in lower parasitic infection. Here, we highlighted PA as an interesting tool for the design of new anti-T. gondii compounds.

Modeling of granular soil-structure interface under monotonic and cyclic loading with the nonlinear approach

A constitutive model that can accurately predict the behavior of the soil-structure interface is beneficial to the analysis and design for foundation engineering performance. This paper develops a new model with the nonlinear approach for simulating the monotonic and cyclic behaviors of the granular soil-structure interface. Based on the hyperbolic function, the concept of normalized shear displacement is proposed, and the basic model for the effects of the normal stress, the nonlinear shear modulus, and the friction angle on shear strength during shearing is deduced. On this basis, the Pyke criterion is modified to describe the cyclic loading responses. The relation between the friction angle and the state parameter of the interface in different interface states is established under the framework of critical state soil mechanics (CSSM) theory to further reflect the interface behaviors corresponding to the changes of void. Taking the phase transformation state as a reference state of volume increment, the incremental equation of stress-dilatancy induced by shearing is developed. In addition, the basic model is extended to be able to describe the interface mechanical behaviors under constant normal load (CNL), constant stiffness (CNS), and constant volume (CV) conditions by considering the characteristics of three typical stress loading paths. Only 10 calibrated parameters are required to reproduce the complex properties in the monotonic and cyclic behaviors. The predictive performance of the proposed interface model is examined by the previous experimental results.

Nonequilibrium criticality driven by Kardar-Parisi-Zhang fluctuations in the synchronization of oscillator lattices

The synchronization of oscillator ensembles is pervasive throughout nonlinear science, from classical or quantum mechanics to biology, to human assemblies. Traditionally, the main focus has been the identification of threshold parameter values for the transition to synchronization as well as the nature of such transition. Here, we show that considering an oscillator lattice as a discrete growing interface provides unique insights into the dynamical process whereby the lattice reaches synchronization for long times. Working on a generalization of the Kuramoto model that allows for odd or non-odd couplings, we elucidate synchronization of oscillator lattices as an instance of generic scale invariance, whereby the system displays space-time criticality, largely irrespective of parameter values. The critical properties of the system (like scaling exponent values and the dynamic scaling Ansatz which is satisfied) fall into universality classes of kinetically rough interfaces with columnar disorder, namely, those of the Edwards-Wilkinson (equivalently, the Larkin model of an elastic interface in a random medium) or the Kardar-Parisi-Zhang (KPZ) equations, for Kuramoto (odd) coupling and generic (non-odd) couplings, respectively. From the point of view of kinetic roughening, the critical properties we find turn out to be quite innovative, especially concerning the statistics of the fluctuations as characterized by their probability distribution function (PDF) and covariance. While the latter happens to be that of the Larkin model irrespective of the symmetry of the coupling, in the generic non-odd coupling case the PDF turns out to be the Tracy-Widom distribution associated with the KPZ nonlinearity. This brings the synchronization of oscillator lattices into a remarkably large class of strongly-correlated, low-dimensional (classical and quantum) systems with strong universal fluctuations.

Interface Bonding Properties of CrAlSiN-Coated Cemented Carbides Doped with CeO2 and Y2O3 Rare Earth Oxides.

This study performed first-principle-based calculations of the interface adhesion work in interface models of three terminal systems: CrAlSiNSi/WC-Co, CrAlSiNN/WC-Co, and CrAlSiNAl/WC-Co. The results proved that the CrAlSiNSi/WC-Co and CrAlSiNAl/WC-Co interface models had the highest and lowest interface adhesion work values (4.312 and 2.536 J·m-2), respectively. Thus, the latter model had the weakest interface bonding property. On this basis, rare earth oxides CeO2 and Y2O3 were doped into the Al terminal model (CrAlSiNAl/WC-Co). Then, doping models of CeO2 and Y2O3 doped on the WC/WC, WC/Co, and CrAlSiNAl/WC-Co interfaces were established. The adhesion work value was calculated for the interfaces in each doping model. When CeO2 and Y2O3 were doped in the WC/WC and CrAlSiNAl/WC-Co interfaces, four doping models were constructed, each model contains interfaces withreduced adhesion work values, indicating deteriorated interface bonding properties. When the WC/Co interface was doped with CeO2 and Y2O3, the interface adhesion work values of the two doping models are both increased, and Y2O3 doping improved the bonding properties of the Al terminal model (CrAlSiNAl/WC-Co) more significantly than CeO2 doping. Next, the charge density difference and the average Mulliken bond population were estimated. The WC/WC and CrAlSiNAl/WC-Co interfaces doped with CeO2 or Y2O3, with decreased adhesion work, exhibited low electron cloud superposition and reduced values of charge transfer, average bond population, and interatomic interaction. When the WC/Co interface was doped with CeO2 or Y2O3, superposition of the atomic charge densities of electron clouds was consistently observed at the CrAlSiNAl/WC-Co interface in the CrAlSiNAl/WC/CeO2/Co and CrAlSiNAl/WC/Y2O3/Co models; the atomic interactions were strong, and the interface bonding strength increased. When the WC/Co interface was doped with Y2O3, the superposition of atomic charge densities and the atomic interactions were stronger than for CeO2 doping. In addition, the average Mulliken bond population and the atomic stability were also higher, and the doping effect was better.

Tumor Evolution Models of Phase-Field Type with Nonlocal Effects and Angiogenesis

In this survey article, a variety of systems modeling tumor growth are discussed. In accordance with the hallmarks of cancer, the described models incorporate the primary characteristics of cancer evolution. Specifically, we focus on diffusive interface models and follow the phase-field approach that describes the tumor as a collection of cells. Such systems are based on a multiphase approach that employs constitutive laws and balance laws for individual constituents. In mathematical oncology, numerous biological phenomena are involved, including temporal and spatial nonlocal effects, complex nonlinearities, stochasticity, and mixed-dimensional couplings. Using the models, for instance, we can express angiogenesis and cell-to-matrix adhesion effects. Finally, we offer some methods for numerically approximating the models and show simulations of the tumor's evolution in response to various biological effects.

Insights into the role of water concentrations on nanomechanical behavior of type I collagen-hyaluronan interfaces in annulus fibrosus: A molecular dynamics investigation.

Multi-faceted deformation capabilities of Annulus Fibrosus (AF) results from an intricate mechanical design by nature. Wherein, organization and interactions between the constituents, collagen type I (CI), collagen type II (C2), hyaluronan, aggrecan, and water are instrumental. However, mechanisms by which such interactions influence AF mechanics at tissue-scale is not well understood. This work investigates nanoscale interfacial interactions between CI and hyaluronan (CI-H) and presents insights into their influence on tissue-scale mechanics of AF. For this, three-dimensional molecular dynamics (MD) simulations of tensile and compressive deformation are conducted on atomistic model of CI-H interface at 0%, 65%, and 75% water concentrations (WC). Results show hyaluronan lowers local hydration around CI component of interface, owing to its hydrophilic nature. Analyses show that increase in WC from 65% to 75% leads to increased interchain sliding in hyaluronan, which further lowers tensile modulus of the interface from 2.1 GPa to 660 MPa, contributing to softening observed from outer to inner AF. Furthermore, increase in WC from 65% to 75%, shifts compressive deformation from buckling-dominant to non-buckling-dominant which contributes towards lower radial bulge at inner AF. Findings provide deeper insights into mechanistic interactions and mechanisms at fundamental length-scale which influence the AF structure-mechanics at tissue-scale.

Cyclic Solid-Liquid Phase Transformations in the text {CaO}–text {SiO}_2 System—Experiments and Modelling

The cyclic growth and shrinkage of solid oxides (i.e. wollastonite) in text {CaO}–text {SiO}_2-based slags is investigated in-situ by means of High-Temperature Confocal Scanning Laser Microscopy (HT-CSLM). The compositions of the slags are carefully selected to induce different phase transformation conditions, i.e. congruent and incongruent melting/solidification. To complement the experimental results, the kinetics of growth and shrinkage of oxide crystals is investigated by means of a sharp interface model where the interfacial reaction and diffusion in the liquid bulk are considered as possible rate-controlling processes. The modelling approach combined with data analysis from key experiments reveals the underlying dissipative processes of solidification and melting phenomena, here, diffusion in the liquid bulk material and/or the interfacial reactions. The modelling approach is likely to be applicable for future materials design and processing problems from this perspective.

Molecular dynamic study of radiation-moisture aging effects on the interface properties of nano-silica/silicone rubber composites

The influence of radiation-moisture aging on the thermodynamic and interface properties of nano-silica/silicone rubber (PDMS) composites was investigated using molecular dynamics simulation. The deterioration of polymer matrix was incorporated into the PDMS-silica interface models based on the hydrolysis products and the dominant role of cross-linking over chain scission. The results indicate that the long-chain structure with the higher molecular weight and the stronger intermolecular interactions are formed by incorporating multi-chain cross-linking and more hydroxyl groups. The coupling effects of the long-chain structure and stronger intermolecular interactions enhance the binding strength between the silica and PDMS matrix owing to the formation of more hydrogen bonds, and restrict the diffusion mobility of PDMS chains and water molecules. The aging of the PDMS matrix facilitates water molecules to adsorb on the surface of the silica and the PDMS matrix to form hydrogen bonds, and eventually weakens the bonding strength of the silica-PDMS interface.

Many universality classes in an interface model restricted to non-negative heights.

We present a simple one-dimensional stochastic model with three control parameters and a surprisingly rich zoo of phase transitions. At each (discrete) site x and time t, an integer n(x,t) satisfies a linear interface equation with added random noise. Depending on the control parameters, this noise may or may not satisfy the detailed balance condition, so that the growing interfaces are in the Edwards-Wilkinson or in the Kardar-Parisi-Zhang universality class. In addition, there is also a constraint n(x,t)≥0. Points x where n>0 on one side and n=0 on the other are called "fronts." These fronts can be "pushed" or "pulled," depending on the control parameters. For pulled fronts, the lateral spreading is in the directed percolation (DP) universality class, while it is in a different universality class for pushed fronts, and another universality class in between. In the DP case, the activity at each active site can in general be arbitrarily large, in contrast to previous realizations of DP. Finally, we find two different types of transitions when the interface detaches from the line n=0 (with 〈n(x,t)〉→const on one side, and →∞ on the other), again with new universality classes. We also discuss a mapping of this model to the avalanche propagation in a directed Oslo rice pile model in specially prepared backgrounds.

Interfacial configuration and interfacial regulation of electronic properties of MoS2 heterophase junctions

The transition of 1H-transition metal dichalcogenides (TMDCs) to 1H-1T’ heterophase junction can be induced by alkali metal ion intercalation, laser irradiation, electric-field-induced etc, but the interfacial configuration is complex and the effect of the interface on the properties of TMDCs heterophase junction is not well known. Herein, we propose two kinds of interface models, namely, steep interface and gradient interface. The properties of 1H–MoS2 and 1T′-MoS2 phases are well preserved in the steep interface model due to clean atomic interface. In the gradient interface model, the interface configuration is relatively complex, but we find that the defects at the interface can release the local strain to improve the stability of the system. Interestingly, it is found that the 1H-1T’ MoS2 heterophase junction with higher intensity of density of state at the Fermi level (N(EF)) is more stable among the gradient interface model. Finally, it is found that the atoms in the interface of 1H-1T’ MoS2 heterophase junction have the largest out-of-plane deformation due to lattice mismatch regardless of the steep interface model or the gradient interface model, and the key factor affecting the electronic properties of the 1H-1T’ MoS2 heterophase junction is the electronic states of the atoms at the interface. We believe that our research provides a theoretical scheme for the interface regulation to achieve the application of 1H-1T’ heterophase junction based on TMDCs.

Development of an adaptive graphic web interface model for editing XML data

The ability of the end user to work with a large amount of data from a large number of heterogeneous sources and at the same time get an effective result from the work is carried out through the use of graphical web interfaces built on the basis of XML technologies that allow displaying any structure of a file presented in XML format. As a data exchange method between applications on the Web, XML still lacks capabilities for identification of web resources and a system that uses them, and capabilities to express the knowledge provided by XLM documents. In this study, a web interface has been developed (a web-based server application), as an XML records editor that provides display forms for the creation and editing of XML documents and is able to adapt to the internal resources of the system used. The technology is based on the XSD data set schema transformation by the way of XSLT transformations. Screen forms are generated on the server side and are provided to the user with all the necessary tools for correct input and/or editing of heterogeneous data. A distinguishing characteristic of this technology is the ability to display both properly and improperly formed XML data. The developed graphical interface allows any application to automatically exchange and read information from other applications without human intervention, which significantly improves performance and ease of use. This software solution could be used both as an independent data building and editing module presented in the XML format, and as a built-in module plugged into various server software for heterogeneous information management systems

Numerical analysis on subcooled boiling in PWR coolant channel based on a modified multi-scale interface model

A modified multi-scale interface model was employed with the Eulerian two-fluid framework to investigate the three-dimensional characteristics of subcooled boiling characteristics in a typical Pressurized Water Reactor (PWR) coolant channel with mixing grid. Based on the morphology identification by adopting an advanced interface topology map, the phase-average method and the interface-reconstruction method can be applied for dispersed bubble and sharp interface, respectively, to improve the calculated precision of interfacial transfers. Models were validated by using the dam break data for sharp interface topology and employing the flow boiling experimental data for the phase distribution in both radial and axial directions. The calculated results agreed well with the experimental data. Thermohydraulic characteristics in the coolant channel were obtained, including void fraction, phase velocity and flow streamline, based on which, the effects of mixing vane on the localized field were analyzed. The vapor volume fraction was decreased in downstream of spacer grid due to the mixing effect, while the lateral flow was enhanced. The vapor accumulation phenomenon was captured and the sharp interface between the liquid and the accumulated vapor was identified by the modified model. Based on this, the interfacial transfer characteristics of the sharp interface was considered in simulations.

Development of a Ni–Al reactive force field for Ni-based superalloy: revealing electrostatic effects on mechanical deformation

The physics-informed expression of interatomic potentials is critical to driving accurate molecular dynamics (MD) simulations while most alloy potentials neglect the electrostatic effects explicitly despite the existence of local charge non-neutrality in multi-component alloys. The Ni–Al ReaxFF force field (dubbed ReaxFFNiAl-S22), implementing charge equilibration scheme for explicit electrostatic interactions, was developed in this work for Ni-based superalloy via parametrization based on density functional theory (DFT) calculations. The ReaxFFNiAl-S22 described well the equation of states of Ni and Ni3Al across various polymorphous structures and defects, improving overall accuracy in comparison with several other reported potentials including ReaxFF and Embedded Atom Method (EAM) potentials. Moreover, the short-range repulsion (inner wall) terms implemented in ReaxFFNiAl-S22 extended the capability of describing highly compressed crystal structures. The new potential was applied in the tensile MD simulations of Ni, Al, and Ni/Ni3Al interface models. The obtained strain–stress relationship and the evolution of dislocations are critical to understanding the dynamics of plastic deformation and fracture of alloys. The charge redistribution was particularly examined during the tensile process of Ni3Al, revealing the important role of electrostatic interactions during the mechanical deformation of alloys that are often overlooked before. This work demonstrates that the reactive force field can be used to study the mechanism of mechanical deformation with electrostatic effects. The proposed electrostatic design principle suggests that alloying elements with large electronegativity and strong covalency would benefit electrostatic contribution to the strength of alloys.

Coupling stress fields and vacancy diffusion in phase-field models of voids as pure vacancy phase

High vacancy concentrations in crystals may lead to formation and growth of voids, which is connected to swelling under irradiation and degradation of material properties. Recent experimental work suggests that vacancy condensation may also be involved in nucleation and evolution of porosity in early stages of ductile fracture. Mostly in the realm of irradiation effects, void formation and growth has been simulated with phase-field methods, where voids are treated as pure vacancy phases. Since vacancies induce an eigenstrain field, it is well-known that the evolution of vacancy concentrations is coupled to the elastic stress field. However, the few existing elastically coupled diffuse interface models of void growth seem to face a conceptual problem in the diffuse interface; in the center of which they predict the highest eigenstrains, which results in unrealistically high, fluctuating stresses. In the current work, we present a new model for coupling elastically driven vacancy diffusion with a diffuse interface model of void surfaces, which overcomes the named short-comings and closely reproduces the sharp interface solution. This is achieved by making the eigenstrain a function of the non-conserved order parameter used to distinguish the crystal and void phase. The model is verified for two-dimensional example problems by comparison to the analytical solution of the according sharp interface model. Eventually, the model is used to show the impact of elasto-diffusional coupling on void growth in mechanically loaded systems. We analyze the model with regard to the bi-stable energy landscape and discuss limitations and future prospects of the approach.