Properties of the material spontaneously formed in interfacial layer of system at extraction of rare-earth elements

The wetting ability of the material formed spontaneously in the interface layer of an aqueous solution of a rare-earth element (REE) salt/solution of di-(2-ethylhexyl)phosphoric acid (D2EHPA) extraction system adhered onto a glass plate is investigated. It is found that its properties depend on the natures of the REE and the solvent, and the initial concentrations of the REE and the extracting reactant. It is shown that the material formed at the interface and adhered onto a glass plate has controlled wetting ability. The difference between the properties of interface REE formations for yttrium and cerium subgroups is established. The electric conductivity of interphase formations in the same systems is measured and shown to display an extreme dependence on time in systems with heptane but a monotonically increasing one in systems with toluene. It is shown that the electric conductivity of interphase formations diminishes sharply with an increase in the ratio of the initial concentrations of REE salt and D2EHPA. It is concluded that an increase in the relative gain of the average molar mass of interphase formations indicates coagulation and the formation of polymers.     

Effect of thermal treatment on interfacial properties of beta-lactoglobulin

The changes in the secondary conformation and surface hydrophobicity of beta-lactoglobulin subjected to different thermal treatments were characterized at pH values of 7, 5.5 and 4 using circular dichroism (CD) and hydrophobic dye binding. Heating resulted in a decrease in alpha-helix content with a corresponding increase in random coil at all pH values, this change being more pronounced for small heating times. Heating also resulted in an increase in surface hydrophobicity as a result of partial denaturation, this increase being more pronounced at pH 4. Thermal treatment resulted in a shift of the spread monolayer isotherm at air-water interface to smaller area per molecule due to increased flexibility and more loop formation. Thermal treatment led to an increase in interfacial shear elasticity and viscosity of adsorbed beta-lactoglobulin layer at pH 5.5 and 7. Interfacial shear elasticity, shear viscosity, stability of beta-lactoglobulin stabilized emulsion and average coalescence time of a single droplet at a planar oil-water interface with adsorbed protein layer exhibited a maximum for protein subjected to 15 min heat treatment at pH 7. At pH 5.5, the interfacial shear rheological properties and average single drop coalescence time were maximum for 15 min heat treatment whereas emulsion stability was maximum for 5 min heat treatment. At pH 7, thermal treatment was found to enhance foam stability. Analysis of thin film drainage indicated that interfacial shear rheological properties do not influence thin film drainage.     

Effect of interfacial tension on the dynamic behavior of droplet formation during microchannel emulsification

Microchannel (MC) emulsification is a novel technique for producing monodisperse emulsions. In this study, we investigated the effect of interfacial tension on the dynamic behavior of droplet formation with various surfactant concentrations. Interfacial tension did not affect the resultant droplet diameter in lower flow velocity ranges, but it did affect the time-scale parameters. These results were interpreted using the droplet formation mechanism reported in our previous study. At surfactant concentrations below 0.3%, the emulsification behavior was differed from that at higher surfactant concentrations. An analysis of diffusional transfer indicated that dynamic interfacial tension affects the emulsification behavior at lower surfactant concentrations. Dynamic interfacial tension that exceeded the equilibrium value led to a shorter detachment time. This resulted in stable droplet formation of monodispersed emulsions by spontaneous transformation, even at flow velocities above the predicted critical flow velocity. A previous study predicted that the droplet formation would become unstable and polydispersed larger droplets would form over critical flow velocity. Wetting of the MC with the dispersed phase at lower surfactant concentrations induced formation of larger polydispersed droplets at high flow velocities.     

Effect of an external periodic field on the rate of chemical reactions

The rates of direct and concert passages of nuclei through a potential barrier in an external periodic field were determined within a generalized Slater model of thermal dissociation of multiatomic molecules. The external field accelerated direct and — to a much greater degree — concert passages. The curves of the efficiency of the concert mechanism of the chemical reaction as a function of the field amplitude were estimated.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 2, pp. 127–132, March–April, 1993.     

Thermophysical properties of interfacial layer in nanofluids

Although recent experiments have revealed that nanofluids have superior thermal conductivities to base fluids, the inherent physics are not fully understood. In this study, an interfacial layer, competing with Brownian motion as a corresponding mechanism, is conceptually connected with the surface-charge-induced electrical double layer. By applying colloidal science, the first explicit equations for the thickness and thermal conductivity of the layer are obtained. A fractal model including the new concept of the layer is developed. The model predictions are compared with experimental data for effects of pH, temperature, volume fraction, and primary particle size of CuO-water nanofluids.     

Effect of heating rate on activation energies derived by a dynamic kinetic method

Alkaline fading of bromophenol blue was chosen for the investigation of the effect of heating rate on the activation energies derived from the dynamic kinetic method. Freeman and Carroll's treatment was adopted to compute the activation energies from experimental data taken with three heating rates: namely 1°, 0.5° and 0.25°/min. It was found that the activation energy increases as the heating rate decreases. This is attributed to the non-equilibrium conditions. By extrapolating to zero heating rate, the activation energy obtained is comparable to that obtained via classical isothermal kinetics.

---

Zusammenfassung Die in alkalischem Medium erfolgende Entfärbung von Bromphenolblau wurde zum Studium des Einflusses der Aufheizgeschwindigkeit auf die nach der dynamischen kinetischen Methode erhaltenen Aktivierungsenergien herangezogen. Das Verfahren von Freeman und Carroll wurde zur Berechnung der Aktivierungsenergien aus Versuchsdaten, welche bei drei Aufheizgeschwindigkeiten, nämlich 1°, 0.5° und 0.25°/min erhalten worden waren, verwendet. Es wurde festgestellt, daß die Aktivierungsenergie mit abnehmender Aufheizgeschwindigkeit zunimmt. Der Grund hierfür wird den Nicht-Gleichgewichtsbedingungen zugeschrieben. Wird auf Aufheizgeschwindigkeit=0 extrapoliert, so ist die erhaltene Aktivierungsenergie mit der nach klassischer isothermer Kinetik erhaltenen vergleichbar.

---

Résumé On a choisi la décoloration du bleu de bromophénol en milieu alcalin pour étudier l'influence de la vitesse de chauffage sur l'énergie d'activation calculée à partir des données fournies par une méthode d'étude cinétique dynamique. On a adopté la méthode de Freeman et Carroll pour calculer les énergies d'activation à partir des données expérimentales obtenues avec trois vitesses de chauffage, à savoir 1°, 0.5° et 0.25°/min. On montre que l'énergie d'activation augmente quand la vitesse de chauffage diminue. On attribue ce phénomène aux conditions de non-équilibre. En extrapolant pour une vitesse de chauffage nulle, on obtient une énergie d'activation comparable à celle calculée par la méthode classique en cinétique isotherme.

---

, . , (1°, 0,5°, 0,25°/) . , .

     

Effect of SDBS on interfacial electron transfer at the liquid/liquid interface by thin layer method

The effect of an adsorbed anionic surfactant sodium dodecyl benzene sulfonate(SDBS) on electron transfer(ET) reaction between ferricyanide aqueous solution and decamethylferrocene(DMFc) located on the adjacent organic phase was investigated for the first time by thin layer method.The adsorption of SDBS at the interface resulted in a decay in the cathodic plateau current of bimolecular reaction with increasing concentrations of SDBS in aqueous phase.However,the rate constant of electron transfer(k_(et)) i...     

Effect of the vibration shear flow field in capillary dynamic rheometer on the crystallization behavior of polypropylene

The self-made capillary dynamic rheometer was adopted to study the relationship between the crystallization behavior of isotactic polypropylene (iPP) and the vibration shear conditions, namely, vibration amplitude and vibration frequency. The crystalline structure of iPP under different vibration conditions was characterized by using differential scanning calorimeter (DSC) and wide-angle X-ray diffractometer (WAXD) techniques. The samples extruded under vibration shear conditions had a higher melting temperature (from DSC). A new shoulder-shape peak appeared at ca. 162 °C under low frequency or low amplitude conditions, which was engulfed by the main melting peak with the increase of the vibration amplitude or frequency. This was probably an indication that more perfect crystals had formed [Polym Eng Sci 38 (1998) 1-20]. The WAXD demonstrated that crystalline form of iPP extruded was not changed but the average crystalline size decreased, according to the Scherrer formula [Analytical methods of polymer materials, China Petrochemical Press, Beijing, 1997]. This proved a large increase in the number of small crystals.     

Effect of anisotropic diffusion and external electric field on the rate of diffusion-controlled reactions

In this paper we investigate theoretically the effect of an external electric field on the rate constant of steady-state bulk diffusion-controlled reactions. We generalize previously derived results for isotropic diffusion in the absence of interparticle interaction [J. Chem. Phys. 87, 4622 (1987)] to the case where translational diffusion is anisotropic. A frequently occurring situation of transverse isotropy where D(x)=D(y) not equal to D(z) is considered in detail. We derive the first-order expansion for the reaction rate constant in terms of the electric field strength E, k(E)=k(0) (1+1/2epsilongamma), where gamma=k(0)/4piRD( perpendicular ), epsilon=qER/k(B)T, q is the charge, R is the contact distance, and D( perpendicular ) is the transverse diffusion coefficient. Numerical calculations show that this first-order expansion works well in the whole range of applicability of the Nernst-Einstein relation, i.e., for epsilon<1.     

Investigation of the dependence of inferred interfacial tension on rotation rate in a spinning drop tensiometer

The spinning drop tensiometer is widely used to study the interfacial properties of many systems. However, there have also been several reported limitations with the spinning drop tensiometer. In this paper, it is shown that there is a relationship between the measured interfacial tension and the rotation rate of the drop. A detailed investigation of this relationship is presented.     

Effect of strain rate on the dynamic tensile behaviour of UHMWPE fibre laminates

Ultra-high molecular weight polyethylene (UHMWPE) fibre has great potential for strengthening structures against impact or blast loads. A quantitative characterization of the mechanical properties of UHMWPE fibres at varying strain rates is necessary to achieve reliable structural design. Quasi-static and high-speed tensile tests were performed to investigate the unidirectional tensile properties of UHMWPE fibre laminates over a wide range of strain rates from 0.0013 to 163.78 s⁻¹. Quasi-static tensile tests of UHMWPE fibre laminates were conducted at thicknesses ranging from 1.76 mm to 5.19 mm. Weibull analysis was conducted to investigate the scatter of the test data. The failure mechanism and modes of the UHMWPE fibre laminates observed during the test are discussed. The test results indicate that the mechanical properties of the UHMWPE fibre laminate are not sensitive to thickness, whereas the strength and the modulus of elasticity increase with strain rate. It is concluded that the distinct failure modes at low and high strain rates partially contribute to the tensile strength of the UHMWPE fibre laminates. A series of empirical formulae for the dynamic increase factor (DIF) of the material strength and modulus of elasticity are also derived for better representation of the effect of strain rate on the mechanical properties of UHMWPE fibre laminates.     

系列烷基苯磺酸盐对烷烃的动态界面性能研究

从表面活性剂分子量、表面活性剂浓度、电解质浓度、 烷烃碳数等方面考察了系列烷基苯磺酸盐异构体纯化合物的油水动态界面张力行为。研究表明,表面活性剂分子量越大和电解质浓度增加使界面张力动态变化越慢,达到平衡所需时间越长;表面活性剂浓度增加和烷烃碳数增加使界面张力动态变化加快,达到平衡所需时间减少。     

Self-assembled structures based on rare earth element salts in the interfacial layer of a liquid/liquid system

1. Download high-res image (189KB)
2. Download full-size image

     

Effect of a reduced mobility layer on the interplay between molecular relaxations and diffusion-limited crystallization rate in ultrathin polymer films

In ultrathin polymer films, the coupling between the segmental mobility, precursor of the molecular diffusion, and the crystallization rate is broken down because of interfacial interactions. In particular, in the presence of a reduced mobility layer at the interface with the substrate, the crystallization kinetics slow down at a length scale bigger than the one connected with the deviation from bulk behavior of the structural relaxation. By modeling the influence of the substrate interactions on the parameters governing the temperature evolution of the main relaxation time, it was possible to reproduce the effect of geometrical confinement on the quantities connected to the diffusion-limited crystallization rate. Upon reduction of the thickness or increasing of the substrate interaction, the films show an apparent higher glass stability in terms of an increase of the cold crystallization temperature and of the crystallization time. The deviations from bulk behavior were found to vanish above a crossover temperature as already observed for the phenomena connected to the glass transition.     

Effect of layer charge and heat treatment on Cs fixation by layer silicate minerals

The effects of total negative layer charge and heat treatments on Cs fixation by layer silicate minerals have been examined. High charge vermiculites produced by K-depletion of micas fixed as much as 97.8% while illites interstratified with low charge montmorillonite layers fixed only 3.9% of the total Cs sorbed from an intermediate-level simulated radioactive waste. Cs fixation increased with an increase in the total negative layer charge of the layer silicate minerals. Heat treatment to various temperatures after Cs sorption as well as exchange saturation increased the Cs fixation in all the layer silicate minerals. However, the temperature to which a layer silicate mineral needs to be heated in order to fix the Cs completely depends also on the total negative layer charge of the mineral.     

Effect of chemical treatment of Kevlar fibers on mechanical interfacial properties of composites

In this work, the effects of chemical treatment on Kevlar 29 fibers have been studied in a composite system. The surface characteristics of Kevlar 29 fibers were characterized by pH, acid-base value, X-ray photoelectron spectroscopy (XPS), and FT-IR. The mechanical interfacial properties of the final composites were studied by interlaminar shear strength (ILSS), critical stress intensity factor (K(IC)), and specific fracture energy (G(IC)). Also, impact properties of the composites were investigated in the context of differentiating between initiation and propagation energies and ductile index (DI) along with maximum force and total energy. As a result, it was found that chemical treatment with phosphoric acid solution significantly affected the degree of adhesion at interfaces between fibers and resin matrix, resulting in improved mechanical interfacial strength in the composites. This was probably due to the presence of chemical polar groups on Kevlar surfaces, leading to an increment of interfacial binding force between fibers and matrix in a composite system.