Presence Of Dispersed Particles Research Articles

Sorption of 137Cs and 60Co on Titanium Oxide Films in Light Water Reactor Primary Circuit Environment.

This paper discusses the processes of the long-lived 137Cs and 60Co immobilization on titanium surfaces in simulated light water reactor primary circuit environments. This study is prompted by numerous problems in both the maintenance of equipment during reactor operation and the dismantling of the reactor after the completion of the operation, which is associated with contamination of working surfaces with long-lived radionuclides. The composition of the oxide films formed on the surface of commercial titanium alloy ПT-3B has been studied with specimens prepared in autoclave test conditions and surface samples from the pipeline sections to which the primary coolant was applied. These films on the coolant pipeline surface consist of a titanium dioxide layer tightly adhered to the pipeline metal surface and weakly fixed deposits—crystallites comprised of titanium oxides and other corrosion products (oxides and hydrated oxides of iron, nickel, chromium etc.). The radionuclide composition of the samples was studied by gamma-spectrometry. It is shown that the mechanism of titanium-surface contamination with 137Cs is by physisorption, contamination level increases upon the presence of dispersed particles. For 60Co, both sorption and deposition onto surfaces are observed.

Study into collagen hydrolyzate applicability as a structure forming agent

The study of foaming properties of collagen hydrolyzate has proved availability of its use as a structure forming agent in production of aerated drinks. The foaming dynamics obtained in a wide range of pH values have shown that glutin forms a stable foam at pH values within 5.8...7 in a temperature range of 8‒10 °C. Microscopy of the obtained foamy structure has shown that it is characterized by the presence of dispersed particles with sizes of various orders and an average radius of a disperse particle equal to 1.53 mm. The IR spectroscopy data have shown presence of free groups capable of hydration. The lowest degree of hydration was observed at pH=10.1 and the highest one at pH=7.0 after 3‒3.5 hours of incubation. Optimum technological parameters of making aerated milk drinks with the use of glutin were obtained: pH=5.2, glutin concentration of 5 %, agar or apple pectin concentration of 1.5 %

Solid distribution and mixing time in stirred tanks: The case of floating particles

AbstractThis work concerns floating particle distribution and liquid mixing dynamics in a solid‐liquid stirred tank. Measurements of local solids concentration distribution at steady‐state conditions and of liquid homogenization in the presence of dispersed particles at transient conditions are collected with up‐pumping and down‐pumping pitched blade turbines. Electrical resistance tomography is the selected experimental technique for the data acquisition in the opaque solid‐liquid mixture. For the time dependent conductivity data processing, the same method commonly applied to the mixing time determination from planar laser induced fluorescence measurements is considered. The method is successfully extended to the characterization of liquid mixing with floating particles. The local data obtained by the ERT technique over the whole vessel volume are fully exploited. The robustness of the method for tackling conductivity variations close to the liquid free surface and due to the particles movement is assessed.

Microstructurally induced computational and material instabilities

A dislocation-density based finite strain crystal plasticity finite element model and an hourglass strain measure orthogonal to the linear velocity field were used to investigate microstructural effects on deformation and hourglass instability. An aluminum aggregate was modeled in quasi-static plane strain tension and compression, and the effects of the presence of manganese-based dispersed particles were investigated. Both local plastic deformation and the presence of these dispersed particles can trigger hourglass instabilities, which can be mistaken for deformation or failure modes. These hourglass modes occur due to the difference in the deformability of neighboring elements or regions and the associated energy modes associated with hourglassing, and the proposed computational methodology can be used to delineate between failure modes and numerical instabilities.

Optimal disturbances of a dusty-gas plane-channel flow with a nonuniform distribution of particles

The classical stability theory for multiphase flows, based on an analysis of one (most unstable) mode, is generalized. A method for studying an algebraic (non-modal) instability of a disperse medium, which consists in examining the energy of linear combinations of three-dimensional modes with given wave vectors, is proposed. An algebraic instability of a dusty-gas flow in a plane channel with a nonuniform particle distribution in the form of two layers arranged symmetrically with respect to the flow axis is investigated. For all possible values of governing parameters, the optimal disturbances of the disperse flow have zero wavenumber in the flow direction, which indicates their banded structure (“streaks”). The presence of dispersed particles in the flow increases the algebraic instability, since the energy of optimal disturbances in the disperse medium exceeds that for the pure-fluid flow. It is found that for a homogeneous particle distribution the increase in the energy of optimal perturbations is proportional to the square of the sum of unity and the particle mass concentration and is almost independent of particle inertia. For a non-uniform distribution of the dispersed phase, the largest increase in the initial energy of disturbances is achieved in the case when the dust layers are located in the middle between the center line of the flow and the walls.

Time-Evolution Equations for Particle Dispersions in Nematic Liquid Crystal Media

A formal re-definition of the hydrodynamic equations for a compressible uniaxial nematic fluid in the presence of dispersed particles is presented, which is particularly amenable to computational treatment. Starting from the Parodi-Foster formulation of nematodynamics equations, it is shown that a functional formulation of the time evolution equations can be obtained which clearly separate conservative and dissipative terms. A simplified discretization scheme is also proposed, which leads to pseudo-particle representation of the fluid in combination with a standard description of the dispersed particles motion.

Spontaneous Formation of Vesicles and Dispersed Cubic and Hexagonal Particles in Amino Acid-Based Catanionic Surfactant Systems

Mixed catanionic surfactant systems based on amino acids were investigated with respect to the formation of liquid crystal dispersions and the stability of the dispersions. The surfactants used were arginine-N-lauroyl amide dihydrochloride (ALA) and N(alpha)-lauroyl-arginine-methyl ester hydrochloride (LAM), which are arginine-based cationic surfactants; sodium hydrogenated tallow glutamate (HS), a glutamic-based anionic surfactant; and the anionic surfactants sodium octyl sulfate (SOS) and sodium cetyl sulfate (SCS). It is demonstrated that in certain ranges of composition there is a spontaneous formation of vesicular, cubic, and hexagonal structures. The solutions were characterized with respect to internal structure and size by cryogenic transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS), and turbidity measurements. Vesicles formed spontaneously and were found for all systems studied; their size distribution is presented for the systems ALA/SCS/W and ALA/SOS/W; they are all markedly polydisperse. The aging process for the system ALA/SOS/W was monitored both by turbidity and by cryo-TEM imaging; the size distribution profile for the system becomes narrower and the number average radius decreases with time. The presence of dispersed particles with internal cubic structure (cubosomes) and internal hexagonal structure (hexosomes) was documented for the systems containing ALA and HS. The particles formed spontaneously and remained stably dispersed in solution; no stabilizer was required. (Cubosome and hexosome are USPTO registered trademarks of Camurus AB, Sweden.) The spontaneous formation of particles and their stability, together with favorable biological responses, suggests a number of applications.

Formation of dispersed particles during plasma oxidation

Microplasma oxidation is a promising method of producing ceramic coatings for various purposes [1–5]. At present theoretical models of breakdown and coating growth are being actively developed and new application areas suggested [6–8]. We already know the mechanisms of growth of microplasma coatings due to electrochemical and chemical oxidation of metals and inclusions of electrolyte elements in the course of thermal reactions on the surface [9]. In the place of microarc discharge on the solutionmetal interface during a short period of time (about 200–1000 μs) high temperatures of 103–104 K and pressure of 102–103 MPa are developed [10] which result in the formation of a vapor-gaseous medium in the space and the local fusing of the base metal, which is ejected by the arc process into the solution where part of it is hydrated and the rest of it remains there in ionic form [11]. The present article shows additional mechanisms of inclusion of electrolyte components into the microplasma coating composition as a result of crystal formation in the electrode layer. Specimens of 2024 aluminium alloy (4.4% Cu, 0.6% Mn, 1.5% Mg) with a total area of 0.02 dm2 served as anode. They were first etched in potassium hydroxide solution and then purified in nitric acid solution. A plate of stainless steel 3 dm2 in area, served as a cathode. The treatment was carried out in electrolyte based on sodium phosphate (20 g·l−1) with inclusions of ferrous citrate (10 g·l−1) and surface—active substances (triethylolamine 15 g·l−1). A potentiostatic processing regime with unipolar sinusoidal or pulse voltage ranging from 300 to 520 V was used. The coating formation time took from 20 to 40 min, with an electrolyte temperature of 298–318 K. The micrographs and the element composition data on the coatings were obtained using a JSM 84 scanning electron microscope with a link adapter at the magnification of 1000 times. Average concentrations of components were obtained from an area of 200 × 200 μm using three measurements. The concentrations in the crystal region were determined by focusing a beam to 5 μm in size. A morphology study of the surface after microplasma processing has revealed, in a number of cases, dispersed formations on the coating, including those of a regular geometric shape (Fig. 1). It indicates the crystalline nature of the above structures. The presence of dispersed particles on the coating surface is caused by the characteristic features of microarc oxidation. Ejection of melt, which accompanies a breakdown, and its interaction with electrolyte, result in the formation of both fused parts around pores and various dispersed particles of the amorphous structure weakly connected to the surface. Crystallisation on the coating surface under given physical conditions (high temperatures and pressures ) is unlikely. The formation of crystals deep in the solution is also highly improbable as it is not supersaturated in any component, and is heated during the microplasma process. In order to explain the mechanism of appearance of dispersed formations of a crystalline structure, the following approach has been suggested. When a unipolar electric current passes through the specimen surface, intensive decomposition of water occurs:

Reactive processing compatibilization of direct injection molded polyamide‐6/poly(ethylene terephthalate) blends

AbstractFinely dispersed blends of polyamide 6 (PA‐6) and poly(ethylene terephthalate) (PET) were obtained by direct injection molding throughout the full composition range. The blends comprised a probably pure PA‐6 phase, and a PET phase that was apparently pure in PET‐rich blends and contained slight reacted PA‐6 amounts in PA‐6‐rich blends. This very complex morphology was characterized by the presence of dispersed particles at three levels and by a very large interface area/dispersed phase volume ratio. The linear ductility behavior was attributed to both the presence of reacted copolymers and the large interface area/dispersed volume ratio, and the synergism in both the Young's modulus and yield stress to the increased orientation of the blends related to that of the pure components. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 564–574, 2005

Ｚｒ添加超微細結晶フェライト系ステンレス鋼の機械的性質 Ｉ．メカニカルアロイング法による組織制御

Targets of this study are realization of better mechanical strength and retention of toughness for ferritic stainless steel by micro-structural modification of grain refinement in the material processing by doping of an active element and mechanical alloying (MA). MA allows the introduction of large strain energy and for materials produced by MA, the formation and presence of dispersed particles in them plays an important role in the grain refinement. The authors have been interested in zirconium which has a high affinity for gaseous impurities such as oxygen, carbon etc., and they examined the effect of zirconium on grain refinement of 12 mass% chrome ferritic stainless steel by MA. Conventional 12Cr(SUS 410) and 12Cr-1Zr ferritic stainless steels containing about 1 mass%Zr were consolidated by extrusion-forming of their powders without MA at 1073 K. They had grain diameter sizes of about 30 μm and 1 μm, respectively. On the other hand, 12Cr-1Zr steel produced through MA and the same consolidation process (designated MA-12Cr-1Zr) had a grain diameter of 0.36 μm or less. For MA-12Cr-1Zr, it seemed that Zr atoms strongly reacted with gaseous impurities such as oxygen and carbon and fixed them as oxide and carbide. These dispersed particles ranged from 5 to 30 nm in diameter. In particular, it seemed that the zirconium oxide particles were more effective in suppressing the growth of grain boundaries as TEM images showed that the particles were mainly located along them. The grain sizes obtained from the diameter and volume fraction of dispersed particles tended to support Doherty's prediction.

Limits of the inertial particle deposition regime and heat transfer in supersonic viscous-dusty-gas flow past bodies

Supersonic steady dusty-gas flow past a blunt body at moderate and large Reynolds numbers Re is considered. Using the complete Navier-Stokes equations for the carrier phase, the effect of viscosity on the limits of the inertial particle deposition regime and the two-phase flow pattern near the frontal surface of the body is studied numerically for 102 ≤ Re ≤ 105. The dependence of the limits of the inertial particle deposition regime on the phase velocity slip ahead of the bow shock is investigated. For large Re, the flow near the stagnation point is studied in the boundary layer approximation. On the basis of numerical calculations over a wide range of variation of the Reynolds number and the particle inertia parameter, the maximum increase in the heat fluxes at the stagnation point due to the presence of dispersed particles in the free-stream is estimated.

Superspreading, Skein Wetting, and Dynamic Surface Tension

A study has been made of the spreading of 0.1% aqueous solutions of “superspreading” trisiloxane surfactants, especially the one made with 7.5 mol of ethylene oxide (L-77), on the hydrophobic surface Parafilm, their dynamic surface tension, and their Draves skein wetting time. No relationship was found between “superspreading” and Draves Skein wetting. The low surface tension of the wetting solution at short time (<0.2 s) is one of the critical conditions for good Draves skein wetting, while a surface tension of 21 mN/m appears to be a necessary but not sufficient requirement for superspreading. The presence of dispersed particles in the solutions is not a requirement for superspreading. The replacement of a portion of the L-77 in the solution by certain alkyl chain nonspreading materials can produce greater superspreading than shown by the former (synergy in superspreading). Synergistic materials contain alkyl chains with less than 10 carbon atoms and can have either one or two hydrophilic and hydrophobi...

Isolation of rhodopsin by the combined action of cardiotoxin and phospholipase A2 on rod outer segment membranes

Freeze-fracture electron microscopy was used to follow morphological changes induced by Naja mossambica mossambica venom V4II cardiotoxin in rod outer segment membrane preparations. The extent of the morphological changes depended on the purity of the cardiotoxin. Pure cardiotoxin had no detectable effect upon the preparation, but, when contaminated with venom phospholipase A2, let to a rapid disintegration of the membrane vesicles. With trace amounts (up to about 0.5% of the cardiotoxin) of phospholipase A2, the membrane vesicles disintegrated into smooth lamellae and particles in solution. These two components were separated by centrifugation. The pellet, which showed the presence of smooth lamellae and aggregated particles, was composed of unbleached rhodopsin, initial membrane lipids, lysolipids and cardiotoxin. The supernatant, which showed only the presence of dispersed particles, was composed of unbleached rhodopsin, lysolipids and cardiotoxin. With cardiotoxin containing larger amounts of phospholipase A2 (more than 0.5% of the cardiotoxin), membrane vesicles were disintegrated into large aggregates of amorphous material, composed of bleached rhodopsin, initial membrane lipids, lysolipids and cardiotoxin. These results confirm our previous observation on the release of integral membrane proteins from membrane vesicles by the action of cardiotoxin containing traces of phospholipase A2 (Gulik-Krzywicki, T., Balerna, M., Vincent, J.P. and Lazdunski, M. (1981) Biochim. Biophys. Acta 643, 101–114) and suggest its possible use for isolation and purification of integral membrane proteins.