Interphase Interaction Research Articles

Mechanisms of formation of an epitaxial ferrospinel layer

Experimental data and theoretical analysis of the process of formation of an epitaxial ferrospinel layer on the (001) plane of magnesium oxide depending on the composition are presented. It is demonstrated that the special features of nucleation and growth of ferrospinel films in the initial stage are determined by the concentration of point defects in the substrate, and after achievement of a certain critical size, by the character of interphase interaction at the film-substrate boundary and thermodynamic parameters of synthesis.

Characterization and relative sonocatalytic efficiencies of a new MWCNT and CdS modified TiO2 catalysts and their application in the sonocatalytic degradation of rhodamine B

TiO2 nanoparticles modified with MWCNTs and CdS were synthesized by the sol–gel method followed by solvothermal treatment at low temperature. The chemical composition and surface structure of the CdS/CNT–TiO2 composites were investigated by X-ray diffraction, specific surface area measurements, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and scanning electron microscopy. Then a series of sonocatalytic degradation experiments were carried out under ultrasonic irradiation in the presence of CNT/TiO2 and the CdS/CNT–TiO2 composites. It was found that RhB was quickly and effectively degraded under different ultrasonic conditions. As expected, the nanosized CdS/CNT–TiO2 photocatalyst showed enhanced activity compared with the non CdS treated CNT/TiO2 material in the sonocatalytic degradation of RhB. The sonocatalyst CCTb with 34.68% contents of Ti heat treated at 500°C for 1h showed the highest sonocatalytic activity. The synergistic effect of the greater surface area and catalytic activities of the composite catalysts was examined in terms of their strong adsorption ability and interphase interaction by comparing the effects of different amounts of MWCNTs and CdS in the catalysts and their roles. The mechanism of sonocatalytic degradation over the CdS/CNT modified TiO2 composites under different ultrasonic conditions was also discussed.

Periodic Bicontinuous Composites for High Specific Energy Absorption

We report on the mechanical behavior of an interpenetrating carbon/epoxy periodic submicrometer-scale bicontinuous composite material fabricated following the design principles deduced from biological composites. Using microscopic uniaxial compressive tests, the specific energy absorption is quantitatively evaluated and compared with the epoxy/air and carbon/air precursors. The carbon/epoxy material demonstrates extremely high specific energy absorption up to 720 kJ/kg and shear-dominant interphase interactions from the interlocked hard (carbon) and soft (epoxy) phases. Such bicontinuous nanocomposites are a new type of structural metamaterial with designed cell topology and mechanical anisotropy. Their inherent small length scale can play a critical role in prohibiting segregated mechanical responses leading to flaw tolerance.

Numerical modelling of dust-layered detonation structure in a narrow tube

The problems of lifting and dispersing of a dust layer behind the propagating shock wave as well as ignition, combustion of coal particles and dust-layered detonation formation in a tube are numerically investigated. The layered detonation is formed at large distance from the place of the primary shock wave initiation (∼100 diameters of the tube). The strong oblique transverse shocks caused by combustion zone were discovered. The acceleration of leading shock wave and dust-layered detonation formation are connected with increasing and intensification of combustion zone which strongly depends on arising system of the oblique waves due to the development of the dust layer instabilities and vice versa. In the applied model, the moving medium is treated as a two-phase, two-velocity and two-temperature continuum with mechanical and thermal interphase interaction. The numerical procedure is based on the finite-volume approach and is implemented for parallel computing. The results obtained are of interest for applications in predictive modelling of accidents in industrial systems with reactive dust.

Numerical simulation of gas–solid flow in a conveying vessel

Conveying vessels, which are widely used in pneumatic systems, feature gas–solid flow with intensive inter-phase interactions and complex flow patterns. In this study, a two-fluid model was used to simulate flow behaviors in an experimental vessel. To model the gas phase, a k-ε turbulent model and the particle phase kinetic theory of granular flow were used. Three hydraulic stages were indicated: the rising, static and declining phases. Flow regimes similar to a spouted bed were formed near the wall, which became increasingly stable over time. Unstable flow regimes that consisted of bubbles and slugs were formed near the central part of the vessel. The velocity distributions of the gas and particles, the pressure profile and the secondary flow are described. A fitted curve of the output and input was obtained, and the influences of inlet conditions, such as velocity and pressure, were also investigated.

Simulation of multiphase systems utilizing independent force fields to control intraphase and interphase behavior

Fixed-charge empirical force fields have been developed and widely used over the past three decades for all-atom molecular simulations. Most simulation programs providing these methods enable only one set of force field parameters to be used for the entire system. Whereas this is generally suitable for single-phase systems, the molecular environment at the interface between two phases may be sufficiently different from the individual phases to require a different set of parameters to be used to accurately represent the system. Recently published simulations of peptide adsorption to material surfaces using the CHARMM force field have clearly demonstrated this issue by revealing that calculated values of adsorption free energy substantially differ from experimental results. Whereas nonbonded parameters could be adjusted to correct this problem, this cannot be done without also altering the conformational behavior of the peptide in solution, for which CHARMM has been carefully tuned. We have developed a dual-force-field approach (Dual-FF) to address this problem and implemented it in the CHARMM simulation package. This Dual-FF method provides the capability to use two separate sets of nonbonded force field parameters within the same simulation: one set to represent intraphase interactions and a separate set to represent interphase interactions. Using this approach, we show that interfacial parameters can be adjusted to correct errors in peptide adsorption free energy without altering peptide conformational behavior in solution. This program thus provides the capability to enable both intraphase and interphase molecular behavior to be accurately and efficiently modeled in the same simulation.

Current limiting performance test of 3-phase tri-axial transformer-type SFCL with re-wound structure at 3-line-to-ground fault in lab-scale transmission system

We have proposed a transformer-type SFCL of a re-wound structure, which can produce a limiting reactance (L-limiting) for smaller fault current and, for larger one, additively give a limiting resistance (L+R limiting). The single-phase proposed model SFCL had been tested and shown good limiting characteristics and excellent recovery performance. A 3-phase tri-axial SFCL of the proposed type had been designed and made using BSCCO2223. This paper describes demonstration tests of the model SFCL carried out using a lab-scale one-machine infinite bus transmission model system. The experimental results on the current limiting performance of the SFCL at the 3-line-to-ground (3LG) fault were shown and discussed. The peak fault current 560 A without SFCL was reduced to 230A with SFCL immediately. The 3-phase SFCL successfully worked without large inter-phase interaction. The SFCL recovered to the stand-by mode under a typical Circuit Breaker (CB) operation sequence.

Charging of dust in thermal collisional plasmas

Thermal strongly collisional dusty plasma is studied. The electrical neutrality of the plasma suggests that the gas phase has some electrostatic energy when the plasma contains charged dust grains. The value of this energy determines the interphase interaction and ionization balance in the plasma. Proceeding from this, a new method of calculation of the dust grains' charges in plasmas with any number of ions (down to zero) has been proposed. The correspondence between the theory and the experimental data is demonstrated.

Intrinsic nanoscale phase separation in miscible mixtures and supramolecular assemblies

A model is used to describe the intrinsic nanoscale phase separation in miscible mixtures and supramolecular assemblies. Phase-separated nanostructures related to size-dependent surface tension, molecular structural factors and strong interphase interactions exist in miscible mixtures and supramolecular assemblies. The intrinsic nanoscale phase separation may exist universally in miscible mixtures.

PVC-silica hybrids: effect of sol–gel conditions on the morphology of silica particles and thermal mechanical properties of the hybrids

Hybrid materials from poly(vinyl chloride) (PVC) and silica have been prepared using different conditions by the sol–gel technique. In situ generation of silica network in the PVC matrix was carried out by hydrolysis/condensation of tetraethoxysilane (TEOS) in the matrix. Morphology of the silica particles produced in hybrid films was studied by scattering electron microscopy. The shape of silica particle produced in the matrix was modified by carrying out the sol–gel process under steam on the hybrid films using TEOS. The films were subjected to strain conditions during this process, which produced lamellar shaped particles in the matrix. It was possible to produce platelet type of structure with different aspect ratio by changing the composition and the stress conditions on the films during the steaming process. Addition of a very small amount of γ-glycidoxypropyltrimethoxysilane as compatibilizer drastically reduced the silica particles size in the matrix to nano-level. Thermal–mechanical properties of some of these hybrids were studied and related to the composition, structure and inter-phase interaction between the silica and the matrix.

Effect of interphase interaction within zinc-filled composite coating on the potential of the cathodic protection of steel

The potential of cathodic protection of steel with composite coatings based on polystyrene (PS) filled by highly dispersed powders of zinc (Zn) of different forms and dispersivities is investigated. The potential for all PS/Zn systems with a low content of filler is shown to be less than for pure metal; as some critical value (the percolation threshold) is reached, the negative values of potential increase abruptly and become higher in absolute value than the potential of pure metal. The threshold zinc contents are found to depend on the particle shape and rise from 9 to 30 vol% upon transitioning from spear-shaped to spherical particles. The electrochemical protection properties of a composite coating are correlate with the enthalpy of mixing of filled composites. The enthalpy of mixing in regions of low filling is shown to be negative, indicating strong interphase interaction; that in regions of high filling is positive. The positive enthalpy of mixing corresponds to compositions that generate the potential of cathodic protection. It is found that an increase in the concentration range of positive values of a composition’s enthalpy of mixing occurs symbatically with a decrease in the threshold concentration of metallic zinc within the composition. We conclude that cathodic protection by zinc-filled polymeric composites is due to weak interphase interaction that results in the aggregation of particles of metallic zinc within a polymeric matrix and the appearance of an infinite cluster. In the case of PS/Zn compositions, it is shown that the infinite cluster appears at enthalpies of mixing greater than 0.6 J/g of the composition.

Photoluminescence of a 5CB liquid crystal–organomontmorillonite nanoparticle heterocomposite

Photoluminescence (PL) of a heterocomposite, consisting of the nematic liquid crystal (LC) 4-pentyl-4´-cyanobiphenyl (5CB) and anisometric nanoparticles of montmorillonite (MMT) clay, modified by cetyltrimethylammonium bromide (CTAB) has been investigated at 4.2 and 300 K. The incorporation of this organoclay (B4) to 5CB decreases the emission intensity by 7–8 times due to efficient resonant quenching of the exciting energy by the organoclay. The spectrum shifts to a long-wave region, with this effect being considerably larger at low temperatures. Graphical separation of complex bands, corresponding to the bulk 5CB and 5СВ + В4 heterosystem at both temperatures revealed that the presence of the organoclay resulted in a significant growth of LC dimer quantity, shifting spectra towards longer wavelengths. Changes in the 5CB luminescence under organoclay influence can be explained by quite strong interphase interactions specified earlier by infrared spectroscopy between the MMT surface and LC, and by a realisation of more flat conformations of 5CB molecules. Confinement effects prevent full crystallisation of 5CB in the 5CB + B4 composite, and LC dimer structures located in the organoclay near-surface layers on the outer surface of the nanoparticles and inside its galleries remain in a larger amount, at low temperature, when compared to bulk 5CB. The remaining LC crystallises and photoluminescence from the 5CB monomers becomes intense.

CONTRIBUTION OF THE INTERPHASE INTERACTION TO THE INTERNAL ENERGY AND THERMODYNAMIC PROPERTIES OF DISPERSED MATRIX COMPOSITES

This paper is devoted to the analysis of physical processes in composite matrix materials whose properties are greatly affected by the interphase interaction of the matrix and the modifier. Contribution of this interaction to thermodynamic and dielectric properties of such materials is investigated by the example of a model system which is a colloid solution of solid particles with charged surface in a polar liquid. Mechanisms underlying formation and stabilization of specific structures near the interphase boundaries of the examined system are discussed. Special attention is paid to the assessment of additional contribution to the internal energy and heat capacity related to the electric interaction of solid and liquid components. Results obtained within the proposed model show that for a certain concentration of liquid (about several percent) the interphase energy in a unit of volume magnificently increases to the values of about 107–108 J/m3 and therefore exceeds heat motion energy of polar molecules. Moreover it was revealed that the electrical part of heat capacity is comparable to self-capacity of the liquid matrix provided that the surface charge density of solid particles is high enough.

Heterogeneous ion-induced nucleation in thermal dusty plasmas

Heterogeneous ion-induced nucleation in thermal dusty plasmas such as welding fumes or combustion plasmas containing metals and metal oxide vapours is considered. The influence of nucleus charging as a result of the interphase interaction on the nucleation free energy is determined. It is shown that the environment enrichment by electrons results in the formation of nuclei at lower values of supersaturation than without electrons. The nucleus equilibrium and the critical radii dependences on the plasma temperature and dusty plasma contents are demonstrated.

Energy velocity and quality factor of poroelastic waves in isotropic media

The energy velocity and Q factor of poroelastic acoustic waves in the context of classical isotropic Biot's theory are revisited. Special attention is paid to the high frequency regime when interphase interaction is viscoelastic. The analogy with viscoelastic behavior is emphasized in derivation of the energy balance equations which relate kinetic energy, potential energy, viscous power dissipation, and elastic energy stored associated with each wave. These lead to exact closed form expressions for the energy velocity and Q factor for both longitudinal and shear waves from energy principles. Most notably, the analysis of the resulting expressions reveals that the energy velocity of both longitudinal and shear waves equals (exceeds) the corresponding phase velocity in the case of the low (full) frequency range theory, and that the exact expression for the Q factor contains an additive correction due to viscoelastic interphase interaction.

Preparation of polystyrene–polyisoprene core–shell nanoparticles for reinforcement of elastomers

Latex-formed core–shell nanoparticles composed of cross-linked polystyrene (PS) core and polyisoprene (PI) shell were successfully synthesized by means of a two-stage emulsion polymerization. The PS core possessed a Z-average diameter of 50.3 nm, and the PS–PI particles took a spherical shape with a Z-average size of 50–70 nm in diameter. Shell thickness was controlled by varying isoprene loading. Necessary interphase interactions between the core and shell domains were also achieved by grafting and swelling polymerization. Latex compounding method was employed to prepare the filled elastomer compounds. As expected, the PS–PI core–shell nanoparticles exhibited excellent reinforcement to elastomeric matrix, enhancing the tensile strength of the styrene–butadiene rubber by approximately 400%. The lower density, better interfacial interactions, and latex compounding process would benefit the PS–PI nanoparticles reinforced elastomer nanocomposites in energy saving.

CONTRIBUTION OF THE INTERPHASE INTERACTION TO THE DIELECTRIC PERMITTIVITY OF COLLOID SYSTEMS

Specific features of the dielectric response of colloid systems with electrically interacting components (polar liquid matrix and solid spherical inclusions) have been revealed. A theory was developed to describe dielectric dispersion and anisotropy of the liquid phase caused by the electric field of surface charges on the solid particles. It was found that the local dielectric permittivity in different directions can vary over a wide range and strongly depends on the strength of the inner field. The existence of the interphase interaction leads to the formation of thin structured liquid layers in the contact area of two phases and, therefore, to a decrease in the average dielectric permittivity of the considered system. Nonuniform structure of the polar liquid was taken into account while the derivation of a mixing formula which clearly demonstrates the contribution of the interphase interaction to the dielectric response of the investigated colloid system.

Numerical Method for Calculation of Two-Phase Electrohydrodynamic Flows in Electrostatic Precipitators

This article presents a detailed description of the numerical method for fully coupled calculation of two-phase electrohydrodynamic flows in electrostatic precipitators (ESPs). The method takes into consideration all the relevant processes involved in an industrial ESP; namely, flow of gas, particle dynamics and electrostatics. It employs the finite volume discretization of the governing equations of the gas flow and electrostatics, and an iterative segregated procedure to solve the resulting set of nonlinear algebraic equations. The behavior of solid particles is described in a Lagrangian manner. Particles of different sizes were tracked. Several interphase interactions, including the turbulence modulation, were modeled. As a result, a simple, accurate and efficient numerical technique, applicable to complex geometries as encountered in ESPs, is obtained. The method is applied to the analysis of the precipitation processes in an ESP with shaped collecting plates.

МодЕлированиЕ многофазноЙ дИффузИИ В двухкоМпонентноМ МеталлическоМ сплавЕ

In this work presented an one-dimensional mathematical model of multiphase diffusion in binary metal system. In constructing the model was taken into account the effect differences of partial molar volumes of components on the processes of interphase interaction

Modified halloysite as a filler for epoxy resins

Modified halloysite as a filler for epoxy resins The modification methods of halloysite and further applications of the modified mineral as a filler for epoxy resins have been presented. The advantage of ultrasound treatment prior to chemical modification with an organic compound in order to obtain a hybrid filler was confirmed. The analysis of the composites obtained with the use of the modified halloysite (3-5 wt.% range) as a filler for epoxy resins indicates an improved interphase interaction and mechanical properties in comparison to the composites based on neat halloysite.