Effect Of Interfacial Energy Research Articles

Effect of the interface energy on the pressure-induced superheating of metallic nanoparticles embedded in a matrix

The pressure-induced superheating of metallic nanoparticles embedded in a coherent or incoherent matrix was evaluated by considering the interface energy effect. As the size decreases, the superheating is weakened from the bulk value to zero for these two systems. Associated to the competing roles of different thermodynamic quantities, the weakening in the coherent system originates from the predominant lattice contraction and melting enthalpy reinforcement because of the negative interface energy, but that in the incoherent system results from the bulk modulus decline due to the positive interface energy. Our theoretical predictions are in agreement with available literature results.

Generalized interfacial energy and size effects in composites

The objective of this contribution is to explain the size effect in composites due to the interfacial energy between the constituents of the underlying microstructure. The generalized interface energy accounts for both jumps of the deformation as well as the stress across the interface. The cohesive zone and elastic interface are only two limit cases of the general interface model. A closed form analytical solution is derived to compute the effective interface-enhanced material response. Our novel analytical solution is in excellent agreement with the numerical results obtained from the finite element method for a broad variety of parameters and dimensions. A remarkable observation is that the notion of size effect is theoretically bounded verified by numerical examples. Thus, the gain or loss via reducing the dimensions of the microstructure is limited to certain ultimate values, immediately relevant for designing nano-composites.

Revisiting Jackson-Hunt calculations: Unified theoretical analysis for generic multi-phase growth in a multi-component system

A straight-forward extension of the Jackson-Hunt theory for directionally solidifying multi-phase growth where the number of components exceeds the number of solid phases becomes difficult on account of the absence of the required number of equations to determine the boundary layer compositions ahead of the interface. In this paper, we therefore revisit the Jackson-Hunt(JH) type calculations for any given situation of multi-phase growth in a multi-component system and self-consistently derive the variations of the compositions of the solid phases as well as their volume fractions, which grow such that the composite solid-liquid interface is isothermal. This allows us to unify the (JH) calculation schemes for both in-variant as well as multi-variant eutectic reactions. The derived analytical expressions are then utilized to study the effect of dissimilar solute diffusivities and interfacial energies on the undercoolings and the solidified fractions. We also perform phase field simulations to confirm our theoretical predictions and find a good agreement between our analytical calculations and model predictions for model symmetric alloys as well as for a particular Ni-Al-Zr alloy.

High-Efficiency Perovskite Quantum-Dot Light-Emitting Devices by Effective Washing Process and Interfacial Energy Level Alignment.

All inorganic perovskites quantum dots (PeQDs) have attracted much attention for used in thin film display applications and solid-state lighting applications, owing to their narrow band emission with high photoluminescence quantum yields (PLQYs), color tunability, and solution processability. Here, we fabricated low-driving-voltage and high-efficiency CsPbBr3 PeQDs light-emitting devices (PeQD-LEDs) using a PeQDs washing process with an ester solvent containing butyl acetate (AcOBu) to remove excess ligands from the PeQDs. The CsPbBr3 PeQDs film washed with AcOBu exhibited a PLQY of 42%, and a narrow PL emission with a full width at half-maximum of 19 nm. We also demonstrated energy level alignment of the PeQD-LED in order to achieve effective hole injection into PeQDs from the adjacent hole injection layer. The PeQD-LED with AcOBu-washed PeQDs exhibited a maximum power efficiency of 31.7 lm W-1 and EQE of 8.73%. Control of the interfacial PeQDs through ligand removal and energy level alignment in the device structure are promising methods for obtaining high PLQYs in film state and high device efficiency.

Giant perpendicular exchange bias with antiferromagnetic MnN

We investigated an out-of-plane exchange bias system that is based on the antiferromagnet MnN. Polycrystalline, highly textured film stacks of Ta/MnN/CoFeB/MgO/Ta were grown on SiOx by (reactive) magnetron sputtering and studied by x-ray diffraction and Kerr magnetometry. Nontrivial modifications of the exchange bias and the perpendicular magnetic anisotropy were observed as functions of both film thicknesses and field cooling temperatures. In optimized film stacks, a giant perpendicular exchange bias of 3600 Oe and a coercive field of 350 Oe were observed at room temperature. The effective interfacial exchange energy is estimated to be Jeff = 0.24 mJ/m2 and the effective uniaxial anisotropy constant of the antiferromagnet is Keff = 24 kJ/m3. The maximum effective perpendicular anisotropy field of the CoFeB layer is Hani = 3400 Oe. These values are larger than any previously reported values. These results possibly open a route to magnetically stable, exchange biased perpendicularly magnetized spin valves.

Effect of Interfacial Energy on Distribution of Nanoparticle in the Melt During the Preparation of Fe-Based ODS Alloys by Thermite Reaction

Effect of Interfacial Energy on Distribution of Nanoparticle in the Melt During the Preparation of Fe-Based ODS Alloys by Thermite Reaction

Interface energy effect on electromechanical behavior of N piezoelectric cylindrical nano-inclusions in piezoelectric matrix

• The electro-elastic surface/interface theory for N piezoelectric cylindrical nano-inclusions is constructed. • The Taylor series transform is introduced to analyze the interacting effect of interface energy between the inclusions. • The effect of interface factors on the stress and electric displacement is discussed in detail. • Some important methods for improving the serving behaviors of piezoelectric nano-structures are proposed. Based on the electro-elastic surface/interface theory for nano-scale piezoelectric composites, the interface energy effect on the stress and electric displacement around N piezoelectric cylindrical nano-inclusions in piezoelectric matrix is investigated, and the matrix is subjected to an anti-plane shear stress and an in-plane electric field at infinity. Combining the complex variable method and stroth's formalism, the general solutions for the complex potentials in the piezoelectric matrix and inside the nano-inclusions are derived by using power series. To consider the interacting effect of interface energy between the nano-inclusions, the transform of Taylor series is introduced. A special case of two piezoelectric nano-inclusions is illustrated. Analyses show that the interaction between the interfaces of nano-inclusions exhibits significant effects on the electromechanical response. The elastic, piezoelectric and dielectric factors of interfaces express different effects on the distribution of electromechanical fields.

Droplets in turbulence: a new perspective

Stirring olive oil and vinegar to make salad dressing creates an emulsion of vinegar droplets in oil. More vigorous stirring gives smaller droplets, while if left to sit the droplets will begin to coalesce and the two fluids will separate. In this vein, Dodd & Ferrante (J. Fluid Mech., vol. 806, 2016, pp. 356–412) present a new analysis of how homogeneous turbulence in a carrier fluid interacts with a suspension of droplets of an immiscible liquid. Based on a set of direct numerical simulations, the authors provide new insights on how turbulence affects the motion of the droplets, their shape and size; then in turn how the droplets alter the flow including effects of interfacial surface energy on the kinetic energy of the flow.

Canonical free-energy barrier of particle and polymer cluster formation

A common approach to study nucleation rates is the estimation of free-energy barriers. This usually requires knowledge about the shape of the forming droplet, a task that becomes notoriously difficult in macromolecular setups starting with a proper definition of the cluster boundary. Here we demonstrate a shape-free determination of the free energy for temperature-driven cluster formation in particle as well as polymer systems. Combined with rigorous results on equilibrium droplet formation, this allows for a well-defined finite-size scaling analysis of the effective interfacial free energy at a fixed density. We first verify the theoretical predictions for the formation of a liquid droplet in a supersaturated particle gas by generalized-ensemble Monte Carlo simulations of a Lennard-Jones system. Going one step further, we then generalize this approach to cluster formation in a dilute polymer solution. Our results suggest an analogy with particle condensation, when the macromolecules are interpreted as extended particles.

Effect of graphite on the electrical conductivity of the lithospheric mantle

AbstractGraphite is considered as one of candidate to explain the high‐conductivity anomalies revealed through magnetotelluric (MT) observations. To investigate the effect of interfacial energy on the interconnection of graphite in olivine matrix, we measured the electrical conductivity of polycrystalline San Carlos olivine mixed with 0.8 vol % graphite on the grain boundaries via impedance spectroscopy at 1 GPa and 300–1700 K in a cubic multianvil apparatus. The olivine‐graphite dihedral angle of the recovered sample was also measured to determine interfacial energy between graphite and olivine. The bulk electrical conductivities and large activation enthalpy (∼1.32 eV) of the carbon‐bearing sample were consistent with those of dry polycrystalline olivine. This behavior implies that graphite cannot be interconnected on olivine grain boundaries, which is also supported by the large dihedral angle (98°) of the olivine/graphite system. Impedance spectroscopy measurements were performed at 3 GPa and a temperature of up to 1700 K for carbon‐coated olivine bicrystal samples to investigate the stability of graphite films on the grain boundaries of silicate minerals under upper‐mantle conditions. The conductivities rapidly or slowly dropped as a function of time and graphite film thickness during annealing at the target temperature. This phenomenon exhibits that graphite film on the olivine grain boundary is readily destroyed under upper‐mantle conditions as supported by microstructural observations on the recovered carbon‐coated olivine bicrystal samples. Higher interfacial energy and larger dihedral angle (∼98°) between graphite and olivine would not allow the maintenance of graphite film on olivine grain boundaries. The activation enthalpy for the apparent disconnection rate of a graphite film on olivine grain boundaries is close to that of carbon diffusion in olivine grain boundaries, which suggests that the disconnection of the graphite film is likely to be controlled by carbon grain boundary diffusion. Therefore, graphite is an unlikely candidate to explain the high‐conductivity anomalies revealed by MT surveys in the upper mantle.

Effect of surface and interface energies on the nonlinear bending behaviour of nanoscale laminated thin plates

Using an improved multilayered plate model, the influence of surface and interface energies on the bending behaviour of laminated nanoplates is incorporated into the Kirchhoff plate theory. Governing equations taking into account the geometrical nonlinearity are obtained to study the influences of surface/interface energies. Based on the Navier and Ritz methods, closed-form solutions for both simply supported and clamped nanoplates are obtained. Numerical results for single- and multilayered nanoplates indicate that the interface effect can noticeably change the elastic behaviour of laminated plates on the nanometer scale. In addition, the flakiness ratio, external load, and number of layers also affect the surface/interface effects at large deformations. This study will be useful for the design and examination of nanoplates and nanoscale devices, especially multilayered plates at large deformations.

Molecular Approach to the Effect of Interfacial Energy on Growth Habit of ε-HNIW

The present work describes how consideration of the onset of supersaturation for 2D nucleation, σ2D, is very important for prediction of the growth habit of ε-hexanitrohexaazaisowurtzitane (ε-HNIW) when the edge energy decreases extremely in solution. From ethyl acetate, the spiral growth model without considering σ2D was shown to accurately predict the polyhedral morphology of ε-HNIW, where the {110}, {101}, {111̅}, {002}, and {101̅} faces are mainly constructed. However, that model was found to be inappropriate for predicting the bipyramidal morphology of ε-HNIW from methanol because the {101} face was anticipated to dominate, but a bipyramid shape is possible only if the {101} face grows faster and finally disappears. The present simulation results show that the edge energy of the {101} face is considerably reduced from methanol by forming a hydrogen bond. This gives rise to a decrease in the σ2D compared with the growth of ε-HNIW from ethyl acetate, which means that the {101} face has a relatively high probability to grow faster by 2D nucleation. As a consequence, a parameter of σ2D enables us to exclude the morphologically unimportant faces among flat-faces by determining which face tends to grow faster by 2D nucleation.

Interfacial Energy and Glass Temperature of Polymers Confined to Nanoporous Alumina

We report on the effect of interfacial energy on the glass temperature, Tg, of several amorphous polymers with various glass temperatures and polymer/substrate interactions confined within self-ordered nanoporous alumina (AAO). The polymers studied include poly(phenylmethylsiloxane) (PMPS), poly(vinyl acetate) (PVAc), 1,4-polybutadiene (PB), oligostyrene (PS), and poly(dimethylsiloxane) (PDMS). The segmental dynamics and associated Tg’s are studied by means of dielectric spectroscopy. The interfacial energy for the polymer/substrate interface, γSL, is calculated with Young’s equation whereas the AAO membrane surface energy is obtained by measuring contact angles for several reference liquids. We find that interfacial energy plays a significant role in the segmental dynamics of polymers under confinement within AAO. There is a trend for a decreasing glass temperature relative to the bulk with increasing interfacial energy. PDMS exhibits the highest interfacial energy and the highest reduction in glass temp...

Size effects in martensitic microstructures: Finite-strain phase field model versus sharp-interface approach

A finite-strain phase field model for martensitic phase transformation and twinning in shape memory alloys is developed and confronted with the corresponding sharp-interface approach extended to interfacial energy effects. The model is set in the energy framework so that the kinetic equations and conditions of mechanical equilibrium are fully defined by specifying the free energy and dissipation potentials. The free energy density involves the bulk and interfacial energy contributions, the latter describing the energy of diffuse interfaces in a manner typical for phase-field approaches. To ensure volume preservation during martensite reorientation at finite deformation within a diffuse interface, it is proposed to apply linear mixing of the logarithmic transformation strains. The physically different nature of phase interfaces and twin boundaries in the martensitic phase is reflected by introducing two order-parameters in a hierarchical manner, one as the reference volume fraction of austenite, and thus of the whole martensite, and the second as the volume fraction of one variant of martensite in the martensitic phase only. The microstructure evolution problem is given a variational formulation in terms of incremental fields of displacement and order parameters, with unilateral constraints on volume fractions explicitly enforced by applying the augmented Lagrangian method. As an application, size-dependent microstructures with diffuse interfaces are calculated for the cubic-to-orthorhombic transformation in a CuAlNi shape memory alloy and compared with the sharp-interface microstructures with interfacial energy effects.

"Cross" Supermicelles via the Hierarchical Assembly of Amphiphilic Cylindrical Triblock Comicelles.

Self-assembled "cross" architectures are well-known in biological systems (as illustrated by chromosomes, for example); however, comparable synthetic structures are extremely rare. Herein we report an in depth study of the hierarchical assembly of the amphiphilic cylindrical P-H-P triblock comicelles with polar (P) coronal ends and a hydrophobic (H) central periphery in a selective solvent for the terminal segments which allows access to "cross" supermicelles under certain conditions. Well-defined P-H-P triblock comicelles M(PFS-b-PtBA)-b-M(PFS-b-PDMS)-b-M(PFS-b-PtBA) (M = micelle segment, PFS = polyferrocenyldimethylsilane, PtBA = poly(tert-butyl acrylate), and PDMS = polydimethylsiloxane) were created by the living crystallization-driven self-assembly (CDSA) method. By manipulating two factors in the supermicelles, namely the H segment-solvent interfacial energy (through the central H segment length, L1) and coronal steric effects (via the PtBA corona chain length in the P segment, L2 related to the degree of polymerization DP2) the aggregation of the triblock comicelles could be finely tuned. This allowed a phase-diagram to be constructed that can be extended to other triblock comicelles with different coronas on the central or end segment where "cross" supermicelles were exclusively formed under predicted conditions. Laser scanning confocal microscopy (LSCM) analysis of dye-labeled "cross" supermicelles, and block "cross" supermicelles formed by addition of a different unimer to the arm termini, provided complementary characterization to transmission electron microscopy (TEM) and dynamic light scattering (DLS) and confirmed the existence of these "cross" supermicelles as kinetically stable, micron-size colloidally stable structures in solution.

Interfacial welding of dynamic covalent network polymers

Dynamic covalent network (or covalent adaptable network) polymers can rearrange their macromolecular chain network by bond exchange reactions (BERs) where an active unit replaces a unit in an existing bond to form a new bond. Such macromolecular events, when they occur in large amounts, can attribute to unusual properties that are not seen in conventional covalent network polymers, such as shape reforming and surface welding; the latter further enables the important attributes of material malleability and powder-based reprocessing. In this paper, a multiscale modeling framework is developed to study the surface welding of thermally induced dynamic covalent network polymers. At the macromolecular network level, a lattice model is developed to describe the chain density evolution across the interface and its connection to bulk stress relaxation due to BERs. The chain density evolution rule is then fed into a continuum level interfacial model that takes into account surface roughness and applied pressure to predict the effective elastic modulus and interfacial fracture energy of welded polymers. The model yields particularly accessible results where the moduli and interfacial strength of the welded samples as a function of temperature and pressure can be predicted with four parameters, three of which can be measured directly. The model identifies the dependency of surface welding efficiency on the applied thermal and mechanical fields: the pressure will affect the real contact area under the consideration of surface roughness of dynamic covalent network polymers; the chain density increment on the real contact area of interface is only dependent on the welding time and temperature. The modeling approach shows good agreement with experiments and can be extended to other types of dynamic covalent network polymers using different stimuli for BERs, such as light and moisture etc.

Force of adhesion on supersolvophobic surfaces: The role of capillary necks.

We study theoretically the force of adhesion of pinned liquid drops in contact with supersolvophobic surfaces. We develop a method to calculate the contact and excess surface areas vs compression of the drops against surfaces characterized by an effective interfacial energy in the Cassie-Baxter wetting regime. We find that a 9° difference in contact angle can increase the force of adhesion by almost three orders of magnitude. We investigate the role that the inevitable formation of capillary necks has on this force, which has the same functional form of Derjaguin's result for elastic solids. Our results suggest that measuring the force of adhesion directly on nearly perfectly solvophobic surfaces may be a more precise technique to quantify the effective interfacial energy than traditional contact angle measurements on macroscopic drops.

Mapping Substrate Surface Field Propagation in Block Polymer Thin Films

We isolated the key substrate–polymer interactions responsible for the propagation of substrate surface field effects in block polymer (BP) thin films through a modified approach to the Owens and Wendt interfacial energy formalism. This modification captured the influence of long-range surface energy components on through-film nanostructure orientation in BP thin films, and it provides a framework for manipulating BP thin film behavior without the need for extensive parameter space exploration. Optical microscopy (OM) of gradient thickness films on chlorosilane-modified substrates provided a high-throughput approach for identifying the critical propagation depth of substrate–polymer interfacial energy effects. Atomic force microscopy (AFM) was combined with OM to verify changes in free surface nanostructure as a function of film thickness. Using a model poly(methyl methacrylate-b-n-butyl acrylate) BP thin films system, we mapped the critical propagation depth as a function of interfacial energy difference...

Stability of the Frank-Kasper σ-phase in BABC linear tetrablock terpolymers.

The phase behavior of B1AB2C tetrablock terpolymer melts is systematically studied using the self-consistent field theory, focusing on the emergence and stability of the complex Frank-Kasper σ-phase. Our study starts with an investigation of the stability region of the σ phase for a generic model of B1AB2C terpolymers, in which the C-blocks form spherical domains immersed in the A/B matrix. Then, we examine the stability of the σ phase for a model system with a specific set of parameters mimicking poly(styrene-b-isoprene-b-styrene-b-ethylene oxide) (SISO) block copolymers which were examined in recent experiments. Our results reveal that the formation of the σ phase is mainly governed by two factors. The first factor is the conformational asymmetry between the A/B-blocks and the C-block, similar to that in conformationally asymmetric AB-type block copolymers. The second factor is the specific chain architecture of B1AB2C. The tetrablock architecture with a specific set of interaction parameters and compositions leads to the formation of large core-shell spherical domains, which amplifies the effect of interfacial energy and thereby stabilizes the σ phase.

The exchange of fines between carriers in adhesive particle mixing: A study using DEM simulation

This study employs DEM simulations to investigate the transfer of fine particles between carrier particles, which is one of the important mechanisms governing adhesive particle mixing. Single collisions between a carrier coated with fines and a non-coated carrier were simulated, in which the interaction between particles was modelled using the JKR theory. Detailed post-impact analysis was carried out to characterise the transfer mechanism and the effects of interface energy between particles, impact velocity and impact angle on the transfer process. It was found that fines are transferred between carriers and are restructured with different patterns according to the relative magnitude of the kinetic energy and the interface energies of particles, both between fines and between fine–carrier. The impact angle, which is closely related to mixer type, has a significant influence on the transfer of fines when the kinetic energy is able to be dissipated into adhesive bonds between fines (which strength is characterised by the corresponding interface energy). The correlation of the particle properties (e.g. interface energies), the processing parameters (e.g. the impact velocity), and the type of mixer (e.g. the impact angle) in characterising the transfer mechanism is established.