Interphase Interaction Research Articles

Electret effect and electrotransport in disperse organic and inorganic systems

The electret properties and electrotransport of venous human blood of various groups and a disperse system based on fine-grained mica are studied. General laws are revealed in the thermally stimulated current spectra of these inorganic and organic systems. The nature of the current peaks and their relation to the physicochemical transformations and the interphase interactions in these systems are discussed. A set of numerical parameters is obtained to describe the electrophysical state of the biological system; it can be used to diagnose the functional and biochemical states of this system.

Study on Multiphase Flow and Mixing in Semidry Flue Gas Desulfurization with a Multifluid Alkaline Spray Generator Using Particle Image Velocimetry

Particle image velocimetry (PIV) technique was used to measure the velocity fields of gas-droplet-solid multiphase flow in the experimental setup of a novel semidry flue gas desulfurization process with a multifluid alkaline spray generator. The flow structure, mixing characteristic, and interphase interaction of gas-droplet-solid multiphase flow were investigated both in the confined alkaline spray generator and in the duct bent pipe section. The results show that sorbent particles in the confined alkaline spray generator are entrained into the spray core zone by a high-speed spray jet and most of the sorbent particles can be effectively humidified by spray water fine droplets to form aqueous lime slurry droplets. Moreover, a minimum amount of air stream in the generator is necessary to achieve higher collision humidification efficiency between sorbent particles and spray water droplets and to prevent the possible deposition of fine droplets on the wall. The appropriate penetration length of the slurry droplets from the generator can make uniform mixing between the formed slurry droplets and main air stream in the duct bent pipe section, which is beneficial to improving sulfur dioxide removal efficiency and to preventing the deposition of droplets on the wall.

Enhanced visible light-induced photoelectrocatalytic degradation of phenol by carbon nanotube-doped TiO 2 electrodes

We used a modified sol–gel method to prepare titanium dioxide and multi-walled carbon nanotube (CNT) composites that we subsequently deposited onto indium tin oxide (ITO) conductive glass plates. We characterized these CNT-doped TiO 2 (CNT–TiO 2) films using X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and diffuse reflectance UV–vis spectroscopy. The photoelectrocatalytic (PEC) activity of the composites was evaluated through their ability to mediate the degradation of phenol. XRD measurements indicated that the TiO 2 component existed solely in the anatase phase and that the crystallinity of the CNTs was low. XPS indicated that carbon atoms could substitute for both oxygen and titanium atoms in the TiO 2 lattice to form Ti–C and Ti–O–C structures, which were responsible for the extra photoabsorption and PEC activity under illumination with visible light, in addition to those provided by the CNTs and carbonaceous and Ti 3+ species. An interphase interaction between TiO 2 and the CNTs elevated the photoabsorbance of the composites in the visible light region. A sample of TiO 2 doped with 10% CNTs and calcined at 400 °C exhibited the highest photocurrent and PEC efficiency. We systematically investigated the effects of several parameters of the PEC process, including the applied potential and pH, on the phenol conversion.

Simultaneous Use Of Class-i And Class-ii Force Fields In CHARMM For Solid-liquid Multiphase Simulation Of Protein-surface Interaction

An appropriate understanding of conformational and behavioral changes of proteins upon their adsorption to synthetic surfaces is of crucial importance in the development of biomaterials because the changes play a governing role in determining cellular responses to implanted materials and substrates for tissue engineering. A detailed analysis of molecular behavior is key to such an understanding, and classical molecular dynamic (MD) simulation is one of the direct methods of addressing this issue. However, one of the challenges in using MD simulation is that class-I force fields (CHARMM, AMBER, OPLS, etc.) that have been parameterized for proteins are not suitable for polymers (i.e., polymer crystal structure not maintained during simulation) and extensive class-II force fields (CFF, PCFF, COMPASS, etc.) have not been parameterized for use in proteins. We have extended the CHARMM code so as to use a dedicated class-I force field for the protein, a class-II force field (image bond extended CFF, or newly implemented PCFF) for the polymer surfaces, and tuned electrostatic and van der Waals parameters for the interphase interaction. Results will be presented on the insufficiency of class-I force field for polymers and the suitability of the use of dual (one class-I and one class-II) force fields for solid-liquid interphase interactions relevant for protein adsorption on PLA polymers.

Optical modulators based on a dual-frequency nematic liquid crystal

This paper experimentally investigates the dynamic characteristics of electrically controlled modulators based on liquid crystals (LCs) in the visible and near-IR regions and the effect of the electric-field parameters on them, along with the variation of the conditions of the interphase interaction of the LCs with the orienting surface. It is shown that it is effective to use a dual-frequency liquid crystal for phase and amplitude modulation of radiation with wavelength 1.55μm. In an LC modulator operating on the S effect, a 2π phase lag is obtained in a time of 2ms. The switching times can be reduced to the microsecond range when the twist effect is used and the LC layer is about 7μm thick by increasing the voltage from 30to50V.

Mathematical and computer modeling of dynamic processes in composite media

Problems of vibrations of a representative element of a composite medium with allowance made for the interphase interaction of components are investigated. The results of computer modeling of plane linear and nonlinear problems and also a three-dimensional problem of dynamic equilibrium of a composite system are considered. The surfaces of solutions for various proportions of reinforcing fibers and interphase layers are obtained and analyzed, and the influence of these layers on the character of vibrational processes is investigated.

Nanocrystalline CNT-TiO<sub>2</sub> Composites Produced by an Acid Catalyzed Sol-Gel Method

Carbon nanotube-TiO2 composites and pure TiO2 are prepared by a modified sol-gel method. The nanoscaled materials obtained are extensively characterized by spectroscopic, microscopic and calorimetric techniques. Their photoactivity is tested in the degradation of phenol under visible illumination. A correlation between the CNT content and the changes in the UV–vis absorption properties was found. The effect induced by CNT on the composite catalysts is explained in terms of an interphase interaction between CNT and TiO2 in the composite catalysts.

Nanostructured polyolefins/clay composites: role of the molecular interaction at the interface

AbstractThe extent of interphase interactions between polymer phase and inorganic particles is the driving force addressing the preparation/properties design in the field of the corresponding micro‐ and nanocomposites. In the case of preparation of nanocomposites based on polyolefins (POs) and inorganic compounds as potentially nanodispersed phase, the use of a PO with proper functional groups is necessary for the interface adhesion and stabilization of the nanostructured morphology. According to this approach, ethylene/propylene copolymers with a different propylene content were used for the preparation of nanocomposites through melt mixing with organophilic montmorillonites (OMMT). By taking into account the important role of functionalities grafted onto POs, two different synthetic approaches were compared here: (1) the dispersion of the inorganic filler was obtained by using previously functionalized POs bearing carboxylate groups as matrices; (2) the nanocomposites were prepared by performing contemporaneously the functionalization of POs (by using maleic anhydride (MAH) and/or diethyl maleate (DEM)) and the dispersion of the filler in a one‐step process. The morphology of the nanocomposites as well as the variation of solubility and glass transition temperature (Tg) of the PO matrix were evaluated and tentatively discussed with reference to functionalization degrees, structure of PO, and preparation procedure. Copyright © 2008 John Wiley & Sons, Ltd.

Thermal-resistant TiB x -n-GaP Schottky diodes

The effect of rapid thermal annealing on the parameters of TiBx-n-GaP Schottky barriers and interphase interactions at the TiBx-GaP interface are studied. It is shown that the contact TiBx-n-GaP system features an increased thermal stability without varying the electrical parameters of the Schottky barrier at temperatures as high as 600°C.

Synthesis, structure and bioactivity of pHEMA/SiO2 hybrids derived through in situ sol–gel process

A novel procedure to synthesize poly(2-Hydroxyethylmethacrylate)-silica blend hybrids is presented. Methacrylate monomers bearing an alkoxysilyl unit, prepared by Michael addition of 2-Hydroxyethylmethacrylate (HEMA) to 3-Aminopropyltriethoxysilane (APTS), were employed. By 13C NMR and mass analysis it was possible to establish the formation of coupling hybrid species. A hybrid material, with final concentration of 30% w/w of silica gel to the mass of polymer, was obtained through basic catalysed sol–gel process of tetraethoxysilane (TEOS) and the alkoxysilyl unit of the hybrid monomer, followed by in situ free-radical polymerization. Optical transparency and higher glass transition temperature than pHEMA suggest an increase in either density or strong interphase interactions. Moreover, pHEMA/SiO2 gel blend hybrid exhibits better thermal stability than the as-prepared polymer. Morphology and structure were studied through scanning electron microscopy (SEM), transmission electron spectroscopy (TEM), and dynamic light scattering (DLS). The structure of the hybrid consisted of nanosilica, 10 nm in mean diameter, uniformly dispersed in the pHEMA phase with strong interactions between the phases. Nevertheless, the swelling ratio of the hybrid was comparable to pHEMA. Using FT-IR spectroscopy, SEM and energy dispersive system (EDS), XRD analysis in vitro bioactivity of the hybrid, due to the inorganic phase, was ascertained therefore, the obtained hybrid can be used to make bioactive scaffold for bone engineering.

Nanocomposites based on polyolefins and functional thermoplastic materials

AbstractPolyolefins are today the most used thermoplastic materials thanks to the high technology and sustainability of the polymerization process, their excellent thermomechanical properties and their good environmental compatibility, including easy recycling. In the last few decades much effort has been devoted worldwide to extend the applications of polyolefins by conferring on them new properties through mixing and blending with different materials. In this latter context, nanocomposites have recently offered new exciting possibilities. This has been made possible on the basis of the improvement of polyolefin functionalization processes with the availability of several olefin homo‐ and copolymers bearing a small (generally less than 1 mol%) amount of backbone grafted polar groups. These are indeed adequate to endow favourable interface interactions with polar macromolecules and inorganic compounds, leading first to compatible blends and then to microcomposites. The successful use of nanostructured dispersed materials has opened, on a similar basis, the way to nanocomposites as described in this review. This review provides a broad and updated description of the synthetic routes to nanostructured biphase materials having the typical structural properties of polyolefins (continuous matrix) but showing enhanced thermomechanical properties, thermostability, lower flammability, lower gas permeability and electrical and optical properties, thanks to the presence of an extended interphase interaction with very different nanodispersed species. Copyright © 2008 Society of Chemical Industry

Synthesis and characterization of SrFe12O19/CoFe2O4 nanocomposites with core-shell structure

SrFe 12 O 19 /CoFe 2 O 4 nanocomposites with core-shell structure were successfully synthesized with two-step coprecipitation method. The samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), Raman spectroscopy, vibrating sample magnetometer (VSM) and radar absorbing material reflectivity far field radar cross-section method, respectively. XRD and TEM results show that CoFe 2 O 4 shell is obtained on the surface of SrFe 12 O 19 . And Raman spectra confirm the core-shell structure of the nanocomposites. The magnetic properties and microwave absorption analyses reveal that there are interphase interactions at the interface of SrFe 12 O 19 and CoFe 2 O 4 , which can affect the magnetic properties and microwave absorption properties of the samples. Compared with core material, the coercivity and saturation magnetization of core-shell nanocomposites decrease obviously, but the microwave absorption properties of nanocomposites are improved greatly.

The impact of the nature of nanofillers on the performance of wood polymer nanocomposites

Wood polymer nanocomposites have been prepared from aspen wood using melamine-urea-formaldehyde (MUF) and montmorillonite nanoclay. The nanoparticles were ground with a ball-mill and mixed with the prepolymer to form suspensions that were subsequently impregnated into the wood and in situ polymerized. The influence of the nature of nanofillers and interphase interactions between nanoparticles and MUF on the physical/mechanical properties of the resulting wood polymer nanocomposites was investigated, using SEM, TEM and Electron Probe Micro-Analysis (EPMA) methods. Significant improvements in wood properties, including surface hardness, modulus of elasticity, dimensional stability and water repellence, were obtained with the addition of hydrophobic nanoparticles into the wood. The improved properties could be ascribed to inherent properties as well as better interphase between MUF and nanoparticles, and their co-reinforcement on the wood. Ball-mill treatment favored the dispersion of the nanoparticles into the wood, but broke down functional groups on the hydrophobic nanoclay surface, which was detrimental for the bonding between the nanoparticles and the MUF matrix.

Phase modulation of light in a two-frequency nematic liquid crystal

This paper presents original studies of the phase modulation of light by nematic liquid crystals (NLCs) with a sign change of the dielectric anisotropy (Δε) as a function of the frequency of the supplied sinusoidal voltage. The voltage dependences of the phase lag are obtained for a number of frequencies. The threshold voltage of the S effect is experimentally determined, and its frequency dependences are found to have a characteristic maximum that corresponds to the critical frequency at which the sign of Δε of the NLC mixture changes. It is shown that, in the frequency interval 100–5000Hz where Δε>0, the phase lag and the threshold voltage are independent of the frequency of the supplied voltage, but they are affected by the conditions of the anisotropic-elastic interphase interaction associated with the orienting surface.

Optical properties of cadmium sulfide colloidal dispersions prepared by interphase synthesis

Cadmium sulfide stable colloidal dispersions in hexane, toluene and toluene solution of polystyrene or polyepoxypropylcarbazole have been obtained by the interphase interaction of cadmium oleate and sodium or hydrogen sulfide dissolved in organic solvent and water, respectively. The effect of the precipitant nature and starting molar ratio Cd 2+/S 2− on the properties of the dispersions have been investigated. CdS nanoparticles exhibited relatively uniform size distribution at about 3 nm and crystal cubic structure. The optical properties of the dispersions have been studied by absorption spectroscopy and photoluminescence.

Slurry Reactors for Gas-to-Liquid Processes: A Review

With the dramatic increase in the international oil price, gas-to-liquid processes of Fischer−Tropsch (FT) synthesis, methanol synthesis, and dimethyl ether (DME) synthesis have become increasingly important and received much attention from both academic and industrial interests. The slurry reactor has the advantages of simple construction, excellent heat transfer performance, online catalyst addition and withdrawal, and a reasonable interphase mass transfer rate with low energy input, which make it very suitable for gas-to-liquid processes. However, its multiphase flow behaviors are very complex and the multiphase reactor has some remarkable scale-up effects; therefore, extensive studies are still needed for the development and design of a high-performance slurry reactor. This article gives a state-of-the-art review of the recent studies on the slurry reactor for gas-to-liquid processes. The influences of the superficial gas velocity, operating pressure and temperature, solid concentration, column dimensions, and gas distributor are discussed. Some recent developments in the liquid−solid separation in a slurry reactor are also summarized. The concept of using internals to intensify the mass transfer and improve the hydrodynamics is discussed based on both experimental results and theoretical analysis. Modeling and simulations of the gas−liquid and gas−liquid−solid flows are briefly reviewed, with focus on the new trend of coupling the population balance model (PBM) into the computational fluid dynamics (CFD) framework to describe the complex bubble behaviors and gas−liquid interphase interactions. The results of a 3000 ton/year pilot plant for DME synthesis are given, showing that the slurry reactor has promising applications in gas-to-liquid processes.

Characterisation of macroporous poly(methyl methacrylate) coated with plasma-polymerised poly(2-hydroxyethyl acrylate)

Macroporous poly(methyl methacrylate) networks with varying cross-linking density and porosity were coated with plasma-polymerised poly(2-hydroxyethyl acrylate) grafted on the pores surface. The result is a mechanically reinforced hydrogel (PMMA- gr- plPHEA) whose properties are characterised in this work using several experimental techniques. Bulk PMMA and bulk PHEA were also characterised as reference materials. The diffusion and water sorption properties of these hydrogels were studied through equilibrium water sorption isotherms and desorption starting with the sample equilibrated in immersion in liquid water or in a vapour atmosphere. Glass transition, dynamic-mechanical relaxation and thermal degradation were characterised in order to study the interphase interaction in these biphasic systems. All these experimental techniques suggested that plasma-polymerised PHEA is more homogeneously interpenetrated with highly cross-linked macroporous PMMA than if the porous substrate is a loosely cross-linked polymer network.

Coupling parameter for low-temperature plasma with condensed phase

The detection of plasma crystals in the dusty plasma [1,2], and the ordered structures of the condensed grains in the plasma of combustion products (smoky plasma) [3,4] stimulated the research of mechanisms of the charged grains interaction in the low-temperature plasma and definition of the criteria parameters of phase transition. Thus it has been found out that the formation of the ordered structures of dust grains occurs in strongly coupled (nonideal) plasma. It has been suggested to use a Coulomb coupling parameter Γ, defined as the ratio of the potential energy of Coulomb interaction between neighboring particles and their kinetic temperature, in order to distinguish the weakly coupled plasma and the strongly coupled plasma [5–11]. The application of such a form of coupling parameter for the description of the condensed grains interactions in the smoky plasma is not always comprehensible, which is caused by a number of its specific properties. The principal distinction of the smoky plasma from discharge dusty plasma is its thermal collision nature. The displacement of ionization equilibrium in the plasma gas phase, caused by the presence of a noncompensate volume charge, is formed in plasma due to the interphase interaction [12]. The condensed grains are formed by homogeneous and heterogeneous condensation in the smoky plasma at burning. Therefore, the condensed phase contains a multimode distribution function for sizes of grains of submicron fraction. This enables us to consider the dusty and smoky plasma as two different kinds of plasma with a condensed disperse phase. Thus, multimode distribution functions for the mentioned grain sizes and the displacement of ionization equilibrium do not make it possible to use the coupling parameter, obtained both for the dusty and smoky plasmas. The present paper is devoted to the development of a coupling parameter applicable to the description of polydisperse systems such as the smoky plasma.

Preparation and characterization of nanostructured MWCNT-TiO 2 composite materials for photocatalytic water treatment applications

Nanoscale composite materials containing multi-walled carbon nanotubes (MWCNT) and titania were prepared by using a modified sol–gel method. The composites were comprehensively characterized by thermogravimetric analysis, nitrogen adsorption–desorption isotherm, powder X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis, transmission electron microscopy, X-ray photoelectron spectroscopy and UV–vis absorption spectroscopy. The analysis revealed the presence of titania crystallites of about 7.5 nm aggregated together with MWCNT in particles of 15–20 nm of diameter. The photoactivity of the prepared materials, under UV or visible irradiation, was tested using the conversion of phenol from model aqueous solutions as probe reaction. A synergy effect on the photocatalytic activities observed for the composite catalysts was discussed in terms of a strong interphase interaction between carbon and TiO 2 phases by comparing the different roles of MWCNT in the composite materials.

Calculation of turbulent momentum transfer in a solid phase based on equations for the second and third moments of particle-velocity pulsations

A chain of transfer equations for the second and third moments of dispersed-phase-velocity pulsations in the anisotropic field of energy of random particle motion is obtained based on the computational procedure developed. The interphase and interparticle interactions are allowed for. The turbulent characteristics of the gas are calculated on the basis of a one-parameter turbulence model generalized to the case of two-phase turbulent flows.