Interphase Interaction Research Articles

Comparative analysis of properties of mechanochemical and chemically synthesized polyaniline and zeolite/polyaniline composites

Polyaniline and polyaniline-mineral composites on the base of zeolite with low polymer content have been synthesized mechanochemically (by solid phase synthesis) and chemically (by liquid phase synthesis). The formation of zeolite/polyaniline composites was confirmed by the results of X-ray phase, FTIR spectral and thermogravimetric analysis. The comparative analysis of spectral, thermal and electrical properties of the synthesized samples of polyaniline and zeolite/polyaniline composites has been carried out. It was shown that the structure of samples of polyaniline synthesized both by mechanochemical and chemical methods is amorphous. The structure of polyaniline in zeolite/polyaniline composites is also mainly crystalline-amorphous with the inclusion of crystalline particles of zeolite as matrices on which particles of polyaniline in the form of emeraldine salt of sulfate acid are formed. It was found that weak interphase interaction between macromolecule of polyaniline and particles of zeolite is possible due to the interaction of hydrogen bonds between surface hydroxy groups of zeolite and imino atoms of the macromolecular chains of polyaniline. The thermal stability of zeolite/polyaniline composites is much higher than pure polyaniline due to the presence of zeolite in the composite. Chemical composition of the composites is practically identical. It was established that the electrical conductivity of mechanically synthesized samples of polyaniline and zeolite/polyaniline composites is several times as high as the electrical conductivity of chemically synthesized samples. The physico-chemical analysis of samples properties has been carried out using a Dron-4 diffractometer (Cu Kα radiation; l=1.54060 Å) in the reflection mode. Fourier-transform infrared (FTIR) spectrа of powders sample were recorded in the range of 4 000–650 cm –1 using a NICOLET IS 10 spectrophotometer in the mode of reflection, which was later transformed into transmission mode. Thermal properties of synthesized samples have been analyzed using Q 1 500-D derivatograph (MOM Paulik - Paulik - Erdei , Hungary) in the temperature range of 20–900 °C under a heating rate of 10 K/min in the atmosphere of air (corundum crucibles; standard – Al 2 O 3 ; weight of samples – 100 mg). The morphology and composition of the polyaniline and zeolite / polyaniline composites were studied by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) methods respectively (accelerated voltage – 20 kV). For these studies, the samples were dispersed by ultrasound in water, put on the platinum plate and dried at room temperature. The electrical conductivity of the pelleted samples was determined by measuring their resistance in the "sandwich" type cells at the temperature of 293±1 K using a Rigol DM 3 068 set of equipment for resistance measuring. Keywords: synthesis, polyaniline, zeolite, composite, structure, morphology.

Selective photocatalytic oxidation of benzene to phenol using carbon nanotube (CNT)-supported Cu and TiO2 heterogeneous catalysts

Abstract Nanostructured composite photocatalysts, comprising multi-walled carbon nanotubes (CNT), the anatase phase of titanium dioxide, and copper oxide, were prepared by sol–gel methodology. The synthesized materials were consequently characterised by various techniques. Nanocomposite heterogeneous catalysts, combining Cu and TiO2 with CNT, were utilized for the direct photocatalytic oxidation of benzene to phenol. A correlation between the presence of nano-metal and the variations in absorption was observed, especially in the UV–vis spectral range. This behaviour was explained by a strong interphase interaction among Cu, TiO2 and CNT. Benzene conversion and turnover was due to an improved adsorption. The selectivity towards phenol production was enhanced by supporting TiO2 with CNT and by impregnating copper, thereby suppressing the mineralisation of benzene and favouring the evolution of phenolic compounds. The synergy between TiO2 and CNT was also observed through a high rate and kinetics of benzene oxidation. The sequential interactions of the hydroxyl radicals (formed from water) with the adsorbed state of benzene on copper or titania surfaces led to an intensified catalysis, and in turn, phenol or hydroquinone product formation. A combination of high activity and stability made the prepared hierarchical catalysts potentially interesting for the photocatalysis applications in selective phenol synthesis.

The Role of Interphase Interactions in Electrosynthesis of Composites Based of Graphene Oxide and Poly-o-Phenylenediamine

The formation of the composite of reduced graphene oxide (RGO) with poly-o-phenylenediamine (PPD) on the surface of SnO2-coated conducting glasses (CG) is studied by the methods of voltammetry, atomic force microscopy (AFM), electron microscopy (SEM) with energy-dispersive X-ray spectroscopic (EDXS) microanalysis, and electron spectroscopy, When a CG with deposited graphene oxide is placed into aqueous solution of o-phenylenediamine (OPD), the monomer is strongly fixed in the GO matrix, as confirmed by EDXS data. The further redox interaction in the two-phase system GO–OPD initiates polymerization of OPD in the GO film. When anodic polarization in switched on, the oxidation and the further polymerization of OPD go on, while GO is reduced to RGO as a result of mediated reaction to yield the RGO–PPD composite even in the absence of cathodic polarization. The electron spectra of composites reveal the presence of an absorption band close to absorption of individual PPD. According to AFM and SEM data, OPD incorporated into the composite structure keeps RGO from being folded in acidic media. As the time of impregnation increases, the degree of reduction of GO to RGO changes, which is reflected in the surface morphology and the amount of monomer in the composite (RGO–PPD)-1. The coating becomes black, which is typical of RGO, and its conductivity increases by 4–5 orders of magnitude.

Numerical simulation for the air entrainment of aerated flow with an improved multiphase SPH model

ABSTRACTAerated flow is a complex hydraulic phenomenon that exists widely in the field of environmental hydraulics. It is generally characterised by large deformation and violent fragmentation of the free surface. Compared to Euler methods (volume of fluid (VOF) method or rigid-lid hypothesis method), the existing single-phase Smooth Particle Hydrodynamics (SPH) method has performed well for solving particle motion. A lack of research on interphase interaction and air concentration, however, has affected the application of SPH model. In our study, an improved multiphase SPH model is presented to simulate aeration flows. A drag force was included in the momentum equation to ensure accuracy of the air particle slip velocity. Furthermore, a calculation method for air concentration is developed to analyse the air entrainment characteristics. Two studies were used to simulate the hydraulic and air entrainment characteristics. And, compared with the experimental results, the simulation results agree with the experimental results well.

A phase-slip moment method for condensing flows

The classic method of moment is extended to account the slips of velocity and temperature between the liquid phase and the gas phase in condensing flows. The moments of droplet size distribution are defined on the liquid phase, instead of on the mixture of liquid and gas, so that the gas phase and the liquid phase can be treated separately. The interphase interaction is realized through source terms which include the mass, momentum and energy exchanges. As a demonstration, this new method of moments is integrated into a numerical method and is applied to a vortex shedding problem with condensation. Due to the very strong velocity slip, a dry zone is found in the vortex core region. This phenomenon was experimentally observed but not discovered by the classic moment method.

A Mathematical Model of Spatial Self-Organization in a Mechanically Active Cellular Medium

A general continual model of a medium composed of mechanically active cells is proposed. The medium is considered to be formed by three phases: cells, extracellular fluid, and an additional phase that is responsible for active interaction forces between cells and, for instance, may correspond to a system of protrusions that provide the development of active contractile forces. The deformation of the medium, which is identified with the deformation of the cell phase, consists of two components: elastic deformation of individual cells and cell rearrangements. The elastic deformation is associated with stresses in the cell phase. The spherical component of the stress tensor describes the nonlinear resistance of the cellular medium, which leads to the impossibility of its excessive compression. The constitutive equation for pressure in the cell phase is taken in the form of a nonlinear dependence on the volume cell density. The rearrangement of cells is considered as a flow controlled by stresses in the cell phase, active stresses, and fluid pressure. The tensor of active stresses is assumed to be spherical and nonlocally dependent on the cell density. Assuming that the process of biological tissue deformation is slow, we obtained a reduced model that neglects the elastic deformation of cells, compared to the inelastic deformation. A linear stability analysis of a spatially uniform steady-state solution was performed. The hydrostatic pressure of fluid is present among the parameters that are responsible for the loss of stability of the steady-state solution: an increase in it has a destabilizing effect owing to the action of the component of the interphase interaction force that is determined by the fluid pressure. The model we obtained can be used to describe the process of cavity formation in an initially homogeneous cell spheroid. The role of local and nonlocal mechanisms of active stress generation in the formation of cavity is investigated.

On Diagnostics of Double Electric Layer in the Zone of Metal–Polymer Adhesion Contact Using the Positron-Annihilation-Probe Method

Application of the positron-annihilation-probe technique for nondestructive diagnostics of the double electric layer (DEL) at the polymer–metal interface and, hence, of the electric component of polymer adhesion to the metal is described. Separated curves of angular correlation of positron-annihilation radiation (ACPAR) for metal, polymer, and metal with a polymer layer allow detecting the presence of a strong electric field of a DEL at the nickel–epoxy-resin interface. The value of the DEL potential is determined to be 15 keV. The method of a positron-annihilation probe allows identifying the presence of a DEL on the internal interfaces of materials and estimating its energy parameters so as to correctly reflect the value of the contribution of the electrostatic component to the interphase interaction.

Tensile Strength of Al Particles/Sisal Fibres Hybrid Composite with Epoxy Matrix

The hybrid composite polymer system was prepared by a vacuum infusion. The reinforcement phase of the composite consists of natural fibers and inorganic aluminum particles. Hard inorganic particles are used in composite systems to optimize certain mechanical characteristics such as hardness, wear resistance or even strength. Hybrid system with an epoxy matrix and a variable concentration of reinforcing phases of aluminum min. purity of 99% (average particle size 31 μm) and sisal fibers was used in the experiment. Sisal fibers were used without a preferred orientation - it was a disordered long-fiber composite system and fibers were treated with 6% aqueous NaOH. The experiment focuses mainly on the hardness and strength characteristics of the composite. Electron microscopy was used to describe the particle morphology and size, and to evaluate matrix filler distribution and interphase interactions.

Measurement of thermally stimulated discharge current (TSDC) for detection of thyroid-stimulating hormone (TSH) in human blood

TSDC was measured in human blood sample with different level of TSH. The origin of TSDC could be explained on the basis of bioelectret effect in biological sample, which is interpreted by fundamental concepts of bioelectret state in biopolymers. The concept of thermal analysis of blood gives the basis of TSDC peaks. The nature of the TSDC peaks and their relation to the physicochemical transformations and the interphase interactions in these systems are discussed. It is observed that the position of TSDC peak is different for different level of TSH. The activation energy, charge released, and peak current were observed to decrease with TSH contents in human blood. The increase of TSH nonpolar salt in human blood is associated with the decrease of charge carriers due to denaturation or hydration of protein with temperature. It is noted that TSDC can be suitable diagnostics of TSH in human blood.

Reinforcing effect caused by equal channel multiple angular extrusion of polymers manufactured by the FDM process: Experimental investigation and mathematical modeling

ABSTRACTThe effect of orientation of the layers of the original structure of polymers produced by fused deposition modeling (FDM) on the reinforcing effect caused by succeeding equal channel multiple angular extrusion (ECMAE) is studied. As test objects, glassy acrylonitrile butadiene styrene copolymer (ABS), glycol‐modified poly(ethylene terephthalate) (PET‐G) and semicrystalline PET are selected, as well as layered composites ABS/PET and ABS/PET‐G. It is demonstrated that ECMAE results in enhancement of microhardness, storage modulus, impact strength. The density, the glass transition temperature, the melting temperature are increased, too. The crystallinity degree of extrudates is enhanced. It is shown that an increment in the mechanical characteristics is better in the case of longitudinal position of the melt layers, as compared to the transversal one. The achieved effects are related to the pore healing, formation of orientation ordering, and enhanced interphase interaction and homogenization of the system in the course of production of layered composites of thermodynamically incompatible polymers. A physical model is suggested that describes the behavior of the layered materials under ECMAE. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45727.

Obtaining of specified effective mechanical, thermal, and electrical characteristics of composite filled with dispersive materials

Properties of polymer matrices compositions can be governed in a variety of ways. The structural modification is one of the most commonly encountered methods, where different effective characteristics of the material are varied by means of reinforcing inclusions, while the chemical nature of the matrix and inclusions is not changed. We propose an approach to determination of governing parameters (phase composition, phase properties, internal geometry, interphase interaction character) providing specified effective properties to the material or getting them into predetermined intervals. In line with this approach, on the basis of solution of a limited number of direct problems (modeling tasks) that define effective characteristics by values of governing parameters, the corresponding response surfaces of electrical, thermal, and deformation-strength properties to the values of the governing parameters are constructed in the state space. Surface analysis allows us to determine whether there is a solution for the selected range of the specified effective characteristics and, if there is one, to specify the range of values of governing parameters. If necessary to ensure simultaneous receipt for the material of both effective thermal and electrical properties and deformation-strength properties, the values of governing parameters are found by the intersection of the relevant areas. The proposed method can obviously be extended to multiphase materials.

A depth-averaged two-phase model for fluvial sediment-laden flows over erodible beds

Fluvial sediment-laden flow represents a class of fluid-solid two-phase flows, which typically involve multi grain sizes, interphase and particle-particle interactions, and mass exchange with the bed. However, existing depth-averaged models ignore one or more of these physical aspects. Here a physically enhanced, coupled depth-averaged two-phase model is proposed for fluvial sediment-laden flow, which explicitly incorporates all these aspects and also turbulent Reynolds stresses. A well-balanced numerical algorithm is applied to solve the governing equations of the model. The present model is benchmarked against a series of typical cases, concerning refilling of a dredged trench, bed aggradation due to sediment overloading, and flood flows due to landslide dam failure. It features encouraging performance as compared to measured data and a quasi single-phase mixture model. The present model reveals that the larger the grain size, the slower the sediment fraction transports, which concurs with prior findings from experimental observations and field data. Also, the fluid phase Reynolds stresses are considerable where the flow rapidly varies, whilst the solid phase Reynolds stresses are negligible if sediment concentration is sufficiently low.

A depth-averaged two-phase model for debris flows over fixed beds

A depth-averaged two-phase model is proposed for debris flows over fixed beds, explicitly incorporating interphase and particle-particle interactions, fluid and solid fluctuations and multi grain sizes. A first-order model based on the kinetic theory of granular flows is employed to determine the stresses due to solid fluctuations, while the turbulent kinetic energy - dissipation rate model is used to determine the stresses from fluid fluctuations. A well-balanced numerical algorithm is applied to solve the governing equations. The present model is benchmarked against USGS experimental debris flows over fixed beds. Incorporating the stresses due to fluid and solid fluctuations and properly estimating the bed shear stresses are shown to be crucial for reproducing the debris flows. Longitudinal particle segregation is resolved, demonstrating coarser sediments around the fronts and finer grains trailing the head. Based on extended modeling exercises, debris flow efficiency is shown to increase with initial volume, which is underpinned by observed datasets.

2D CFD numerička simulacija fluidizacione komore sagorevanja bazirane na Euler-Euler granularnom modelu

U radu je predložen dvodimenzijski model numeričke simulacije sagorevanja tečnih goriva u flu-idizovanom sloju, koji se zasniva na dvo fluidnom Euler – Euler pristupom modeliranja fluidizovanog sloja uz određivanje polja brzina gasa i čestica u dvofaznim, granularnim tokovima zasnovane na ana-logiji sa kinetičkom teorijom gasova (KTGF). Sveobuhvatan model kompleksnih procesa u fluidizacio-noj komori sagorevanja podrazumeva, pored određivanja polja brzina gasne i čestične faze, inkorpori-ranje energetskih jednačina gasne i čestične faze, kao i transportnih jednačina hemijskih komponenti sa izvornim članovima usled konverzije komponenata. Brojni numerički eksperimenti pokazuju da je izbor koeficijenata u izrazima za sile trenja prilikom interakcije faza ima izuzetan značaj i mora se sprovesti za svaki, značajno različit režim fluidizacije, posebno. Urađene su serije numeričkih eksperi-menata sa simulacijom procesa sagorevanja u FS sa i bez značajnog sadržaja vode u gorivu. Proračuni su nestacionarni, a modelirani vremenski period odgovara vremenu za koje gas prođe kroz celu visinu reaktora. Numerički eksperimenti, na osnovu predloženog matematičkog modela, su takođe korišćeni za potrebe analize uticaja različitih snaga pri kojima radi reaktor, kao i različitih stepena fluidizacije, na efikasnost sagorevanja kao i na profile temperatura u zoni sagorevanja.

Fluid dynamics and reaction assessment of diesel oil hydrotreating reactors via CFD

In this work, computational fluid dynamics (CFD) has been used to investigate diesel hydrotreating (Hydrodesulfurization (HDS) and Hydrodearomatization (HDA)) in a laboratory scale trickle bed reactor (TBR). In order to investigate these reactions, the 3D model was developed using a multi-phase Eulerian-Eulerian approach, an inter-phase interaction model, a porosity distribution model for the trilobe particles, mass transfer and chemical reactions model. Due to the small dimensions of the reactor, the simulations are carried out at isothermal and transient conditions and the catalyst bed is considered to be fully wetted. In this first phase of the work, a reaction model was used, which was later validated. Then, a counter-current reactor is simulated and the results are compared with a co-current reactor. The analyzed parameters are conversion, pressure drop and liquid holdup and a special attention was given in order to verify how operational changes on pressure, temperature, velocity and gas and liquid flows influence the reactor performance. The influence of porosity on fluid velocity and volume fraction of liquid is also investigated. Finally, the influence of the liquid hourly space velocity (LHSV), temperature, gas-liquid ratio and partial pressure of H2S are also discussed. The results for the two types of reactors are similar despite the fact that the counter-current arrangement has achieved lower conversions.

Mathematical modelling and numerical simulation of two-phase gas-liquid flows in stirred-tank reactors

This paper presents the mathematical modelling and numerical simulation of the turbulent, two-phase flow of liquid and gas in a gas-induced agitated stirred-tank reactor, using Computational Fluid Dynamics (CFD) techniques. The reactor used as an application demonstration of the developed model is the ozone-induced one, first designed and modeled by Yang et al. (1999). A three-dimensional (3D), transient, Euler-Euler two-phase flow model is developed and used to investigate the turbulent flow and mixing of liquid and bubbles in the stirred-tank reactor, applying the sliding mesh approach. Turbulence is simulated by means of several available models, the Renormalization Group (RNG) k-ε model being the one finally recommended as the most appropriate of the ones studied, for the present application. Two-way coupling between the two phases is modeled by means of appropriate inter-phase interaction relations. The study focused on bubbles of one size group (mean aerodynamic diameter of 2.5E-03m), but it is easily extended to any number of sizes. It is concluded that the predicted overall flow field pattern and the mixing of both phases around the two blades of the simulated baffled stirred vessel, as well as inside and outside of the main tube of the reactor, are physically plausible, appear reasonably accurate, and are, therefore, satisfying.

Ionic Liquid-Silica Precursors via Solvent-Free Sol–Gel Process and Their Application in Epoxy-Amine Network: A Theoretical/Experimental Study

This work describes the solvent-free sol-gel synthesis of epoxy-functionalized silica-based precursors in the presence of 1-butyl-3-methylimidazolium-based ionic liquids (ILs) containing different anions: chloride (Cl-) and methanesulfonate (MeSO3-). The IL-driven sol-gel mechanisms were investigated in detail using experimental characterizations (29Si NMR and ATR FTIR spectroscopy) and a theoretical computational method based on density functional theory (DFT). We observed complex IL influence on both hydrolysis and condensation steps, involving especially H-bonding and Coulomb coupling stabilization of the process intermediates. The obtained IL-silica precursors and their further xerogels were widely characterized (rheology measurements, MALDI TOF, 29Si NMR, ATR FTIR, and DFT simulation), which allowed observation of their precise silica structures and established their most energetically favorable conformations. The detected silica structures were dependent on the IL type and varied from highly condensed 3D cage-like to branched ladder-like and cyclic ones. The application of prepared IL-silica precursors as reinforcing additives into the epoxy-amine network led to an improvement in the organic/inorganic interphase interactions through chemical and physical bonding. Uniform and well-dispersed silica aggregates, in the size of ∼30 nm, were formed when ≤6.8 wt % of each IL-silica precursor was applied into the epoxy-amine network. The use of imidazolium-based ILs contributed to a significant improvement in thermomechanical properties of hybrids and reduced their UV absorption ability compared to that of the reference matrix. All hybrids exhibited an increase in energy to break (up to ∼53%), elongation at break (up to ∼43%), shear storage modulus in the rubbery region (up to 4 times), and thermo-oxidative stability.

Accumulation of Free Electret Charges in Small-Sized Electrically Active Systems

The paper focuses on the study of structural features and electret properties of the fine-sized mineral kaolin. Special attention is paid to the mechanism of interphase interaction at the interface of electrically active heterogeneous media that leads to the emergence of internal self-electric field capable of ensuring the current circulation in such systems. The authors consider the possibility of regulating the processes of local change in the polar water structure under the impact of the self-electric field.

A study of internal friction anomalies in stainless steel with nanostructured plasma coating

The study of the damping in the elastic vibration energy was conducted on the samples of steel Cr18Ni9Ti and 12Cr18Ni10Ti shaped as a solid rod and a capillary, respectively. Plasma coatings based on NiА1–SiO 2 ·Al 2 O 3 were researched in broad temperature and deformation ranges. The research has proved an essential influence of plasma nanostructured coatings applied as aerosils on the temperature and amplitude dependences of the internal friction in the sample composite materials. The research has revealed anomalies and peak effects in the coated samples in the temperature spectrum, both in the low-temperature and high-temperature areas. The study has revealed the effect of coating (NiА1–SiO 2 ·Al 2 O 3 ) on the peaks of various physical nature. The presence of complex damping characteristics is due to the complex microstructure of the coating that contains internal interfaces and pores. Moreover, additional damping mechanisms are realized at the interfaces of individual grains, particles, and also at the interphase interaction boundary in the “coating-base” system. The proposed damping criterion is based on understanding of the opposite influence of coatings on the display of various factors. Such factors include: an increase in the damping in the energy of elastic vibrations and, at the same time, fixation of dislocations and a decrease in the shear formation in the presence of nanocomponents in different coating zones.

Numerical simulation of flow behavior of particles in a liquid-solid stirred vessel with baffles

Flow behavior of particles is simulated by means of two-fluid model combining with kinetic theory of granular flow in a liquid-solid stirred vessel with baffles. The Huilin-Gidaspow drag model is used to obtain interphase interaction of liquid and solids phases. The virtual mass force is considered in simulations. The moving reference frame is applied to the rotation of numerical domain. Predictions are compared with experimental data measured by Pianko-Oprych et al. (2009) in a liquid-solid stirred vessel. This comparison shows that the present model can capture the liquid-solid flow in a liquid-solid stirred vessel. The distributions of velocity and solids volume fraction are predicted at the different heights. The effects of particle density on flow behavior of particles are generally scarce using CFD. Simulations indicate the stirred vessel consists of three regions based on distributions of velocity and turbulent kinetic energy, they are blade circulation region, conical induced region and near-wall region. As an increasing of the impeller speed, the turbulence kinetic and solids phase velocity rise, and the particles fluctuation is intensified.