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Particle Suspension (particle + suspension)
Selected AbstractsIn Situ X-Ray Radiography and Tomography Observations of the Solidification of Aqueous Alumina Particle Suspensions,Part I: Initial InstantsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2009Sylvain Deville This paper investigates by in situ high-resolution X-ray radiography and tomography the behavior of colloidal suspensions of alumina partic les during directional solidification by freezing. The combination of these techniques provided both qualitative and quantitative information about the propagation kinetic of the solid/liquid interface, the particle redistribution between the crystals and a particle-enriched phase, and the three-dimensional organization of the ice crystals. In this first part of two companion papers, the precursor phenomena leading to directional crystallization during the first instants of solidification are studied. Mullins,Sekerka instabilities are not necessary to explain the dynamic evolution of the interface pattern. Particle redistribution during these first instants is dependent on the type of crystals growing into the suspension. The insights gained into the mechanisms of solidification of colloidal suspensions may be valuable for the materials processing routes derived for this type of directional solidification (freeze-casting), and of general interest for those interested in the interactions between solidification fronts and inert particles. [source] Fabrication of Gas Electrodes by Wet Powder Spraying of Binder-Free Particle Suspensions Using a Pulse Injection ProcessJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2007Naoki Oishi A process for wet powder spraying of binder-free particle suspensions using pulse injection was devised for the fabrication of gas electrodes. The resulting deposited electrodes were found to have fine and uniformly distributed pores, to have good adhesion, and low interfacial resistance on electrolyte substrates. The uniformity of the layers was improved by decreasing the spray pulse to 0.05 s with a 1-s off period. Even without drying or any pre-treatments before firing, there was no cracking or delamination of the deposited layer. The deposited layer remained porous, crack-free, and well bound to the substrate after firing. [source] Particle Redistribution During Dendritic Solidification of Particle SuspensionsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2006Noah O. Shanti Solidification of the liquid medium in ceramic suspensions containing less than a critical volume fraction powder leads to the formation of particle-free dendrites of the frozen medium. These particle-free dendrites create, after sublimation of the frozen vehicle, large dendrite pores. We define the conditions under which particle-free dendrites form, and relate the size and volume fraction of the dendrites to the volume fraction powder and the solidification rate. [source] Online Particle Size Measurement in Microgel Particle Suspensions: Principles and Data AnalysisCHEMIE-INGENIEUR-TECHNIK (CIT), Issue 10 2010Prof. Dr.-Ing. Abstract If a gelled system is subjected to shearing or the concentration of reactive components is low, microgel particles are formed. Since labile microgel particles with high water capacities can often be found in food systems, and as they are important for the textural properties, particle size measurement is relevant for fundamental research and control of industrial processes. A chord length measurement system was tested for online particle sizing. [source] Natural convection of a water-fine particle suspension in a rectangular cell heated and cooled from opposing vertical walls: The effect of distribution of particle sizeHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 8 2001Masashi Okada Abstract A water-fine particle suspension with a uniform initial temperature and concentration in a rectangular cell was heated from a vertical wall and cooled from the opposing vertical wall. The dispersed particles had a distribution in size. In this natural convection, many layers separated by almost-horizontal sharp interfaces were observed. In the beginning many layers appear, and each interface of the layers falls gradually with a constant velocity, and finally all layers vanish. To clarify this phenomenon, concentrations and mean diameters of the particles in each layer and temperature distributions were measured. Moreover, natural convection of the other suspension with particles which had a narrow size distribution was also investigated. © 2001 Scripta Technica, Heat Trans Asian Res, 30(8): 636,647, 2001 [source] Kinetics of fluid,solid reaction with an insoluble product: zinc borate by the reaction of boric acid and zinc oxideJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2004Aparna V Shete Abstract Mixing parameters influencing the final particle size and conversion of zinc oxide were studied for the formation of zinc borate. Formation of zinc borate was via a fluid,solid reaction. The process was kinetically controlled above the minimum speed for particle suspension, Ns. The reaction kinetics was developed and the rate constant was estimated. Copyright © 2004 Society of Chemical Industry [source] Drug encapsulation using supercritical fluid extraction of emulsionsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2006P. Chattopadhyay Abstract The current work was aimed at evaluating a new method, supercritical fluid extraction of emulsions (SFEE), for the production of composite (e.g., polymer-drug) micro- and nanoparticles, intended for application in sustained-release drug delivery formulations. Using the proposed method, composite particles were obtained, both in a continuous or batch manner by supercritical carbon dioxide extraction of oil-in-water (o/w) emulsions. Model drugs indomethacin and ketoprofen and biodegradable polymers poly(lactic/glycolic) acid and Eudragit RS were used in order to demonstrate the effectiveness of the SFEE process for producing these particles. Stable aqueous suspensions of composite micro and nanoparticles, having sizes ranging between 0.1 and 2 µm were consistently obtained. Emulsion droplet diameter was found to be the major size control parameter. Other parameters investigated included polymer and drug concentrations in solvent and emulsion solvent fraction. The residual solvent content in the particle suspension obtained was consistently below 50 ppm. Standard dissolution tests were used to observe the sustained release phenomenon of the composite particles. The dissolution profile was characterized in terms of the intrinsic dissolution kinetic coefficients taking into account the specific surface area and solubility of the particles. It was observed that the kinetic coefficient parameter for encapsulated drugs was reduced by 2,4 orders of magnitude when compared to the unprocessed drug particles. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:667,679, 2006 [source] Tissue distribution of radioactivity following intranasal administration of radioactive microspheresJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 5 2001J. E. Eyles The aim of this study was to increase understanding of the kinetics of microparticle distribution and elimination following intranasal application. To do this we investigated the in-vivo distribution of radioactivity following intranasal instillation of scandium-46 labelled styrene-divinyl benzene 7-,m-diameter microspheres. Groups of BALB/c mice received 0.250 mg (47.5 kBq) particles suspended in either 50-,l or 10-,l volumes of phosphate buffered saline. The in-vivo distribution of radioactivity was influenced by the volume of liquid that was used to instil the microsphere suspension. Comparatively large (50 ,l) administration vehicle volumes resulted in substantial bronchopulmonary deposition (, 50% of administered dose). Intranasal instillation of microspheres suspended in 10-,l volumes tended to restrict particle deposition initially to the nasal cavity. For both administration vehicle volumes tested, the radioactivity per unit mass of excised nasal-associated lymphoid tissue (NALT) was found to be consistently elevated relative to other tissues. This corroborates the findings of other workers who have previously identified NALT as an active site of microparticle accumulation following intranasal application. Elimination via the alimentary canal was the principal fate of intranasally applied radiolabeled material. No significant concentration of radioactivity within excised gut-associated lymphoid tissue (GALT) (Peyer's patches) was noted. At latter time points we observed, in mice that received the 50-,l volume particle suspension nasally, accumulation of potentially relevant quantities of radioactivity in the liver (0.3% after 576 h) and spleen (0.04% after 576 h). Thus, our data corroborate the notion that epithelial membranes in the lung are probably less exclusive to the entry of microparticulates into systemic compartments than are those mucosae in the gastrointestinal tract or nasopharynx. This effect may contribute to the effectiveness of pulmonary delivered antigen-loaded microparticles as humoral immunogens. [source] Experimental Study on Particle Size Distribution and Concentration Using Transmission Fluctuation Spectrometry with the Autocorrelation TechniquePARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 3 2005Xiaoai Guo Abstract Based on the statistical characteristics of the transmission fluctuations in the particle suspension, transmission fluctuation spectrometry with autocorrelation (TFS-AC) is described theoretically, with the assumptions of geometric ray propagation and completely absorbent particles in the suspension. The experiments presented here are realized in a focused Gaussian beam with the TFS-AC technique. The acquisition of transmission fluctuation signals is achieved by using a high-resolution digital oscilloscope. The transition function of TFS-AC is obtained by varying the autocorrelation time. With a modified iterative Chahine inversion algorithm, solving a linear equation retrieves information on the particle size distribution and particle concentration. Some experimental results on spherical and non-spherical particles are presented and discussed. The experiments cover a particle size range from 1,m to 1000,,m and a particle concentration of up to 12,%. [source] Improved electroluminescence of spark-processed silicon by an aerosol-assisted technique,PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003N. Shepherd Abstract The electroluminescence (EL) intensity (radiant flux) of spark-processed (sp) Si has been improved by one order of magnitude by introducing into the spark plasma an intimately mixed methanol/silicon particle suspension. This results in a smoother surface and an increased contact area to the semitransparent silver layer. As a consequence the light emitting region is substantially enhanced. Further, the device current increases by aerosol-assisted spark processing compared to conventional sp techniques. The EL spectra of sp-Si display maxima near 750 nm (1.7 eV) and 660 nm (1.9 eV) and a threshold wavelength for light emission at about 360 nm (3.2 eV). A mechanism for sp-induced EL of Si is proposed. [source] Utilization of nanoscale zero-valent iron for source remediation,A case studyREMEDIATION, Issue 2 2006Keith W. Henn A pilot-scale study was performed using a palladium-catalyzed and polymer-coated nanoscale zero-valent iron (ZVI) particle suspension at the Naval Air Station in Jacksonville, Florida. A total of 300 pounds of nanoscale ZVI particle suspension was injected via a gravity feed and recirculated through a source area containing chlorinated volatile organic compounds (VOCs). The recirculation created favorable mixing and distribution of the iron suspension and enhanced the mass transfer of sorbed and nonaqueous constituents into the aqueous phase, where the contaminants could be reduced. Between 65 and 99 percent aqueous-phase VOC concentration reduction occurred, due to abiotic degradation, within five weeks of the injection. The rapid abiotic degradation processes then yielded to slower biological degradation as subsequent decreases in -elimination parameters were observed,yet favorable redox conditions were maintained as a result of the ZVI treatment. Post-treatment analyses revealed cumulative reduction of soil contaminant concentrations between 8 and 92 percent. Aqueous-phase VOC concentrations in wells side gradient and downgradient of the source were reduced up to 99 percent and were near or below applicable regulatory criteria. These reductions, coupled with the generation of innocuous by-products, indicate that nanoscale ZVI effectively degraded contamination and reduced the mass flux from the source, a critical metric identified for source treatment. A summary of this project was recently presented at the US EPA Workshop on Nanotechnology for Site Remediation in Washington, D.C., on October 21,22, 2005. This case study supplied evidence that nanoscale zero valent iron, an emerging remediation technology, has been implemented successfully in the field. More information about this workshop and this presentation can be found at www.frtr.gov/nano/index.htm. © 2006 Wiley Periodicals, Inc. [source] Nanoparticle Coating for Advanced Optical, Mechanical and Rheological Properties,ADVANCED FUNCTIONAL MATERIALS, Issue 16 2007F. Hakim Abstract Primary titania nanoparticles were coated with ultrathin alumina films using Atomic Layer Deposition (ALD). The deposited films were highly uniform and conformal with an average growth rate of 0.2,nm per coating cycle. The alumina films eliminated the surface photocatalytic activity of titania nanoparticles, while maintained their original extinction efficiency of ultraviolet light. Deposited films provided a physical barrier that effectively prevented the titania surface from oxidizing organic material whereas conserving its bulk optical properties. Parts fabricated from coated powders by pressureless sintering had a 13,% increase in surface hardness over parts similarly fabricated from uncoated particles. Owing to its homogeneous distribution, the secondary alumina phase suppressed excessive grain growth. Alumina films completely reacted during sintering to form aluminum titanate composites, as verified by XRD. Coated particles showed a pseudoplastic behavior at low shear rates due to modified colloidal forces. This behavior became similar to the Newtonian flow of uncoated nanoparticle slurries as the shear rate increased. Suspensions of coated particles also showed a decreased viscosity relative to the viscosity of uncoated particle suspensions. [source] Instabilities during batch sedimentation in geometries containing obstacles: A numerical and experimental study,INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 8 2007Rekha R. Rao Abstract Batch sedimentation of non-colloidal particle suspensions is studied with nuclear magnetic resonance flow visualization and continuum-level numerical modelling of particle migration. The experimental method gives particle volume fraction as a function of time and position, which then provides validation data for the numerical model. A finite element method is used to discretize the equations of motion, including an evolution equation for the particle volume fraction and a generalized Newtonian viscosity dependent on local particle concentration. The diffusive-flux equation is based on the Phillips model (Phys. Fluids A 1992; 4:30,40) and includes sedimentation terms described by Zhang and Acrivos (Int. J. Multiphase Flow 1994; 20:579,591). The model and experiments are utilized in three distinct geometries with particles that are heavier and lighter than the suspending fluid, depending on the experiment: (1) sedimentation in a cylinder with a contraction; (2) particle flotation in a horizontal cylinder with a horizontal rod; and (3) flotation around a rectangular inclusion. Secondary flows appear in both the experiments and the simulations when a region of higher density fluid is above a lower density fluid. The secondary flows result in particle inhomogeneities, Rayleigh,Taylor-like instabilities, and remixing, though the effect in the simulations is more pronounced than in the experiments. Published in 2007 by John Wiley & Sons, Ltd. [source] Fabrication of Gas Electrodes by Wet Powder Spraying of Binder-Free Particle Suspensions Using a Pulse Injection ProcessJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2007Naoki Oishi A process for wet powder spraying of binder-free particle suspensions using pulse injection was devised for the fabrication of gas electrodes. The resulting deposited electrodes were found to have fine and uniformly distributed pores, to have good adhesion, and low interfacial resistance on electrolyte substrates. The uniformity of the layers was improved by decreasing the spray pulse to 0.05 s with a 1-s off period. Even without drying or any pre-treatments before firing, there was no cracking or delamination of the deposited layer. The deposited layer remained porous, crack-free, and well bound to the substrate after firing. [source] Transmission Fluctuation Spectrometry in Concentrated Suspensions.PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 1 2005Part Three: Measurements Abstract The theory of transmission fluctuation spectrometry (TFS) was developed for particle size analysis in flowing particle suspensions, whereby the statistical transmission fluctuations are used to extract the particle size distribution (PSD) and particle concentration. In the previous parts of this publication high concentration effects on TFS were investigated theoretically and by simulation. This work presents a study on TFS measurements in concentrated suspensions. By introducing an empirical correction to include the high concentration effects from both the monolayer structure and particle overlapping in the inversion algorithm, it is possible to obtain the particle size distribution and particle concentration over broad ranges of particle sizes and concentrations. [source] | ||||||||||||||||