Home About us Contact
|
Home About us Contact | ||
|
|
||
Primary Particle Size (primary + particle_size)
Selected AbstractsIn-situ Measurement of Primary Particle Sizes during Carbon Black ProductionCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2003S. Dankers During the production of carbon black monitoring of primary particle size plays an important role since this parameter determines product properties and is specified accordingly. For process control fast information about this size is absolutely necessary. In the work presented here it was investigated whether time-resolved laser-induced incandescence is suitable for on-line measurement of primary particle sizes of carbon black during the production process. The results obtained experimentally in industrial production and test reactors were compared with values for the specific surface area from laboratory analyses of sampled material. [source] Low-Temperature Synthesis of Phase-Pure 0D,1D BaTiO3 Nanostructures Using H2Ti3O7 TemplatesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2010Duk Kyu Lee Abstract One-dimensional (1D) barium titanate (BaTiO3) nanowires, which were uniformly covered with 0D BaTiO3 nanocrystals, were synthesized by using a simple solvothermal reaction of protonated trititanate (H2Ti3O7) nanowires with barium hydroxide octahydrate [Ba(OH)2·8H2O] at 80 °C in ethanol/water mixed solvent systems. The compositions of the mixed solvents , the volume ratio of ethanol to deionized water , was a key controlling parameter in order to determine the phase formation and primary particle size of the 0D BaTiO3 nanocrystals. Single-phase cubic perovskite BaTiO3 started to form at 80 °C in a mixed solvent containing more than approximately 60,% by volume of ethanol. Field-emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) analysis revealed that the as-prepared BaTiO3 retained its wire-shaped morphology with nanocrystals on the surface. Furthermore, the synthetic mechanism of the 0D-1D BaTiO3 nanostructures was demonstrated in view of the dielectric tuning of the mixed solvent and the similarities between the crystal structures of BaTiO3 and H2Ti3O7. [source] Design of granule structure: Computational methods and experimental realizationAICHE JOURNAL, Issue 11 2006Mansoor A. Ansari Abstract The spatial distribution of solid components and porosity within a composite granule,its microstructure,is an important attribute as it carries information about the processing history of the granule and determines its end-use application properties, particularly the dissolution rate. In this work, the problem of rational design of granule structure is formulated, and two methods for its solution are proposed,stochastic design, which is based on random permutation of points within the structure using the simulated annealing algorithm, and variational design, which is based on direct simulation of granule formation from its constituent primary particles, followed by direct simulation of granule dissolution. The variational design method is demonstrated in a case study of the effect of primary particle size, radial distribution of components, and composition of a two-component granule (active, excipient) on the dissolution profile. Selected granule structures designed computationally were also physically made by fluid-bed granulation, their structure analyzed by X-ray micro-tomography, and dissolution curves measured. It was confirmed that the designed structures are feasible to manufacture and that they meet the required dissolution profiles. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Polymer flocculation of calcite: Experimental results from turbulent pipe flowAICHE JOURNAL, Issue 4 2006Alex R. Heath Abstract The kinetics of aggregation/breakage of calcite particles flocculated with a high-molecular-weight polymer flocculant has been studied in turbulent pipe flow. The mean flocculation residence time was varied by changing the length of pipe between the flocculant injection point and the in-stream particle-sizing probe (Lasentec FBRM). A variety of pipe sizes and flow rates were used to produce a range of mean fluid shear rates. The mean shear rate was calculated from the pressure drop along the pipe reactor, as measured by manometer, and was found to vary markedly as a function of both the solid fraction and aggregate size. Increased fluid shear increased the initial mixing and aggregation rates, but ultimately lead to a reduced final aggregate size due to increased aggregate breakage. Several other process variables were also studied, with the aggregate size increased with flocculant dosage and primary particle size, but reduced at higher solid fraction. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source] Comparison of particle sizing techniques in the case of inhalation dry powdersJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2001Cynthia Bosquillon Abstract The objectives of this work were (i) to validate electrical zone sensing and laser diffraction for the analysis of primary particle size in the case of inhalation dry powders and (ii) to study the influence of the aggregation state of the powder on the sizing techniques. Free-flowing dry powders were prepared by spray-drying with a combination of albumin, lactose, and dipalmitoylphosphatidylcholine. The replacement of lactose by mannitol, the removal of albumin, and the atomization at high relative humidity all increased powder cohesion. Automated measurements were compared with primary particle sizes collected by light and electron microscopy. The mass mode obtained by electrical zone sensing and the mass median diameter measured by laser diffraction following dispersion with compressed air at a pressure of 3 bar or following suspension in water and ultrasonic dispersion at a power of 60 W for 30 s each provided primary particle sizes close to microscopy measurements. However, these conditions only applied in the case of slightly to moderately aggregated powders. For strongly agglomerated powders, an exact measurement of the size was only collected by laser diffraction in the wet state combined with ultrasonic dispersion. Our study underlies how measurement of primary particle size highly depends on both powder material and proper particle dispersion. © 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:2032,2041, 2001 [source] Fabrication and Luminescent Properties of Nd3+ -Doped Lu2O3 Transparent Ceramics by Pressureless SinteringJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2009Ding Zhou The fabrication of transparent Nd3+ ion-doped Lu2O3 ceramics is investigated by pressureless sintering under a flowing H2 atmosphere. The starting Nd-doped Lu2O3 nanocrystalline powder is synthesized by a modified coprecipitant processing using a NH4OH+NH4HCO3 mixed solution as the precipitant. The thermal decomposition behavior of the precipitate precursor is studied by thermogravimetric analysis and differential thermal analysis. After calcination at 1000°C for 2 h, monodispersed Nd3+:Lu2O3 powder is obtained with a primary particle size of about 40 nm and a specific surface area of 13.7 m2/g. Green compacts, free of additives, are formed from the as-synthesized powder by dry pressing followed by cold isostatic pressing. Highly transparent Nd3+:Lu2O3 ceramics are obtained after being sintered under a dry H2 atmosphere at 1880°C for 8 h. The linear optical transmittance of the polished transparent samples with a 1.4 mm thickness reaches 75.5% at the wavelength of 1080 nm. High-resolution transmission electron microscopy observations demonstrate a "clear" grain boundary between adjacent grains. The luminescent spectra showed that the absorption coefficient of the 3 at.% Nd-doped Lu2O3 ceramic at 807 nm reached 14 cm,1, while the emission cross section at 1079 nm was 6.5 × 10,20 cm2. [source] Spray Pyrolysis of Fe3O4,BaTiO3 Composite ParticlesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2009Tomoyuki Adachi Fe3O4,BaTiO3 composite particles were successfully prepared by ultrasonic spray pyrolysis. A mixture of iron(III) nitrate, barium acetate and titanium tetrachloride aqueous solution were atomized into the mist, and the mist was dried and pyrolyzed in N2 (90%) and H2 (10%) atmosphere. Fe3O4,BaTiO3 composite particle was obtained between 900° and 950°C while the coexistence of FeO was detected at 1000°C. Transmission electron microscope observation revealed that the composite particle is consisted of nanocrystalline having primary particle size of 35 nm. Lattice parameter of the Fe3O4,BaTiO3 nanocomposite particle was 0.8404 nm that is larger than that of pure Fe3O4. Coercivity of the nanocomposite particle (390 Oe) was much larger than that of pure Fe3O4 (140 Oe). These results suggest that slight diffusion of Ba into Fe3O4 occurred. [source] Synthesis of Ba(Mg1/3Ta2/3)O3 Microwave Ceramics through a Sol,Gel Route Using Acetate SaltsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2004Chien-Cheng Tsai A sol,gel process to unsophisticatedly synthesize Ba(Mg1/3Ta2/3)O3 (BMT) ceramics at low cost has been developed in the present work. This process involves the reaction of TaCl5 with acetates of Ba and Mg in the presence of citric acid. Pure BMT polycrystalline powders can be obtained by calcining the synthesized products at 1000°C. The BMT powders were found to have a primary particle size as small as 100 nm. BMT ceramics with favorable structural characteristics can be obtained from sintering of the sol,gel BMT at temperatures much lower than that for the conventional solid-state BMT. Sintering the sol,gel BMT in pellet form at 1300°C resulted in an ordering parameter of 0.72 for the pellet, and a relative density of >95% was achieved with sintering at 1500°C. The grain size of the sintered sol,gel BMT was large and uniform in comparison with the products from the solid-state method. Using the sol,gel route, sintering at temperatures as low as 1400°C gave ceramics with acceptable microwave dielectric properties (a dielectric constant of 16 and Qf factor of 14 400 GHz), while higher temperatures (>1600°C) are needed for the solid-state route to give similar properties. [source] Formation Mechanism of Hydrous Zirconia Particles Produced by the Hydrolysis of ZrOCl2 Solutions: III, Kinetics Study for the Nucleation and Crystal-Growth Processes of Primary ParticlesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2001Koji Matsui The formation rate and primary particle size of monoclinic, hydrous zirconia particles produced by the hydrolysis of various ZrOCl2 solutions (with and without the addition of HCl, NH4OH, NaCl, CaCl2, or AlCl3) were measured to clarify the effects of the H+ and Cl, ion concentrations on the nucleation and crystal-growth processes of primary particles of hydrous zirconia. Chemical-kinetic analyses, to which Avrami,Erofeev's equation was applied, and XRD measurements revealed that both the rate constant and the primary particle size of the hydrous zirconia decreased as the concentrations of H+ and/or Cl, ions produced by hydrolysis increased. The nucleation rate per unit of ZrOCl2 concentration and the crystal-growth rate of the primary particles of the hydrous zirconia were determined by analyzing the relationships between the rate constant and primary particle size. The nucleation rate per unit of ZrOCl2 concentration revealed almost no change and remained constant as the H+ and/or Cl, ion concentrations increased, except in the case of a slight increase for ZrOCl2 solutions with added HCl. The crystal-growth rate decreased as the H+ and/or Cl, ion concentration increased. The present kinetic analyses revealed that the decrease in rate constant with increasing H+ and/or Cl, ion concentrations resulted from the decrease in the crystal-growth rate. The decreasing tendency of the crystal-growth rate was attributed to interference with crystal growth by the Cl, ions attracted onto the particle surface through the formation of an electric double layer. The formation mechanisms for the primary particles of hydrous zirconia were determined based on the present experimental results. [source] Influence of Particle Morphology and Flow Conditions on the Dispersion Behavior of Fumed Silica in Silicone PolymersPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 3 2004John Boyle Abstract The dispersion behavior of agglomerates of several grades of fumed silica in poly(dimethyl siloxane) liquids has been studied as a function of particle morphology and applied flow conditions. The effects of primary particle size and aggregate density and structure on cohesivity were probed through tensile and shear strength tests on particle compacts. These cohesivity tests indicated that the shear strength of particle compacts was two orders of magnitude higher than the tensile strength at the same overall packing density. Experiments carried out in both steady and time-varying simple-shear flows indicate that dispersion occurs through tensile failure. In the steady-shear experiments,enhanced dispersion was obtained at higher levels of applied stress and, at comparable levels of applied stress, dispersion was found to proceed faster at higher shear rates. Experiments conducted in time-varying flows further corroborated the results obtained in tensile cohesivity tests. Experiments in which the mean and maximum stresses in the time-varying flows were matched to the stresses produced in steady shear flows highlight the influence of flow dynamics on dispersion behavior. [source] In-situ Measurement of Primary Particle Sizes during Carbon Black ProductionCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2003S. Dankers During the production of carbon black monitoring of primary particle size plays an important role since this parameter determines product properties and is specified accordingly. For process control fast information about this size is absolutely necessary. In the work presented here it was investigated whether time-resolved laser-induced incandescence is suitable for on-line measurement of primary particle sizes of carbon black during the production process. The results obtained experimentally in industrial production and test reactors were compared with values for the specific surface area from laboratory analyses of sampled material. [source] Comparison of particle sizing techniques in the case of inhalation dry powdersJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2001Cynthia Bosquillon Abstract The objectives of this work were (i) to validate electrical zone sensing and laser diffraction for the analysis of primary particle size in the case of inhalation dry powders and (ii) to study the influence of the aggregation state of the powder on the sizing techniques. Free-flowing dry powders were prepared by spray-drying with a combination of albumin, lactose, and dipalmitoylphosphatidylcholine. The replacement of lactose by mannitol, the removal of albumin, and the atomization at high relative humidity all increased powder cohesion. Automated measurements were compared with primary particle sizes collected by light and electron microscopy. The mass mode obtained by electrical zone sensing and the mass median diameter measured by laser diffraction following dispersion with compressed air at a pressure of 3 bar or following suspension in water and ultrasonic dispersion at a power of 60 W for 30 s each provided primary particle sizes close to microscopy measurements. However, these conditions only applied in the case of slightly to moderately aggregated powders. For strongly agglomerated powders, an exact measurement of the size was only collected by laser diffraction in the wet state combined with ultrasonic dispersion. Our study underlies how measurement of primary particle size highly depends on both powder material and proper particle dispersion. © 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:2032,2041, 2001 [source] Hydrothermal Synthesis of Alpha Alumina (,-Al2O3) Powders: Study of the Processing Variables and Growth MechanismsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2010Wojciech L. Suchanek Alpha alumina (,-Al2O3) powders and ,-Al2O3/boehmite (,-AlOOH) mixtures with controlled ,-AlOOH contents were synthesized hydrothermally under alkaline or acidic conditions at 380°,435°C for 1,10 days, under 6.9,14.5 MPa pressure, from concentrated precursors without stirring. The precursors were formed by mixing different types of aluminum hydroxides with water, and optionally with ,-Al2O3 seeds, hydrogen peroxide, sulfuric acid, dopants (i.e., KMnO4), and/or other additives. The experiments were performed on industrial scale in large production autoclaves. The synthesized ,-Al2O3 powders exhibited up to 100% phase purity, 99.98% chemical purity, equiaxed morphology, low aggregation levels, narrow crystallite size distributions with primary particle sizes ranging between 100 nm and 40 ,m, and high reproducibility. Precursor types, seeds, chemical additives, and temperature/time of the hydrothermal synthesis were found to govern properties of the powders. Different growth mechanisms for nanosized and rough powders are discussed. Results of this study enable the use of hydrothermal ,-Al2O3 powders in a multitude of applications, and make their hydrothermal production a commercial reality. [source] In-situ Measurement of Primary Particle Sizes during Carbon Black ProductionCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2003S. Dankers During the production of carbon black monitoring of primary particle size plays an important role since this parameter determines product properties and is specified accordingly. For process control fast information about this size is absolutely necessary. In the work presented here it was investigated whether time-resolved laser-induced incandescence is suitable for on-line measurement of primary particle sizes of carbon black during the production process. The results obtained experimentally in industrial production and test reactors were compared with values for the specific surface area from laboratory analyses of sampled material. [source] | |||||||||||||