Aerosol Synthesis of Aluminum Nitride Powders

1991 ◽  
Vol 249 ◽  
Author(s):  
Albert A. Adjaottor ◽  
Gregory L. Griffin
Keyword(s):  
Particle Size ◽  
Residence Time ◽  
Particle Diameter ◽  
Aerosol Formation ◽  
Yield Efficiency ◽  
Operating Variables ◽  
Aerosol Process ◽  
The Mean ◽  
Diffusive Mixing ◽  
Mean Particle Diameter

ABSTRACTWe describe a new laboratory-scale aerosol process for producing AIN powder. A two-stage reactor design is used. In the first stage, triethyl aluminum (TEA = AI(CC2H5 )3) and NH3 react to form an aerosol adduct in a laminar flow diffusive mixing zone. The aerosol then enters the furnace stage, where it is converted to AIN. We have examined the influence of the major operating variables (e.g., inlet TEA concentration, reactor residence time, and furnace temperature) on the particle size and distribution, yield, and efficiency. For example, increasing the TEA concentration from 0.12 to 1.30 µmol/cm3 causes an increase in the mean particle diameter (from 0.07 to 0.13 Pim), a slight increase in polydispersity (from 0.31 to 0.43), and a decrease in yield efficiency (from 90% to 73%). In contrast, decreasing the reactor residence time (by increasing the flow rate) has little effect on mean particle diameter, but causes a significant increase in yield efficiency (approaching 100%). The overall behavior of the reactor suggests a model in which the particle size distribution of the final product is determined primarily by the aerosol formation steps in the mixing stage (i.e., nucleation, growth, and coalescence), while the composition and crystallinity of the product are determined by furnace conditions.

Solubility and Micronization of Ganciclovir

2011 ◽  
Vol 393-395 ◽  
pp. 1421-1426
Author(s):  
Feng Xiang Tang ◽  
Yun Zhang ◽  
Su Na Lin ◽  
Zhong Li Guo
Keyword(s):  
Aqueous Solution ◽  
Particle Size ◽  
Particle Diameter ◽  
Absolute Bioavailability ◽  
Stabilizing Agents ◽  
Ph Values ◽  
Solubility Behavior ◽  
The Mean ◽  
Liquid Precipitation ◽  
Mean Particle Diameter

Ganciclovir (GCV) is only slightly soluble in water and hence oral GCV gives low absolute bioavailability. Liquid precipitation is an effective way to prepare micro-sized drug particles. The solubility of GCV in several solvents or in aqueous solution at different pH values was determined. According to its solubility behavior, reactive precipitation was suggested as the micronization method of GCV. The mean particle diameter of micronized GCV powder was around 15~20 μm, smaller than that of raw GCV powder, and the size distribution of micronized GCV was narrower than that of raw GCV. The stirring rate, the type and addition of stabilizing agents seemed to have no significant effect on the particle size of micronized GCV. Micronized GCV showed much faster dissolution rate than raw GCV.

Synthesis of Immiscible Alloys by the Mixalloying Process

1989 ◽  
Vol 111 (1) ◽  
pp. 70-78 ◽  
Author(s):  
S. Tu¨rker Oktay ◽  
Chong N. Chu ◽  
Nannaji Saka ◽  
Nam P. Suh
Keyword(s):  
Particle Size ◽  
Computational Simulation ◽  
Particle Diameter ◽  
Al Alloys ◽  
Size Distributions ◽  
Simulation Studies ◽  
Particle Size Distributions ◽  
The Mean ◽  
Log Normal ◽  
Mean Particle Diameter

Dispersed-phase microstructures of the immiscible Pb-Zn, Pb-Zn-Sn and Pb-Al alloys were produced by the Mixalloying Process [1]. The particle size was found to follow the log-normal statistical distribution and the mean particle diameter correlated well with the –3/5th power of the Weber number. Furthermore, computational simulation studies showed that the particle-size distributions became significantly broader due to Stokes coalescence during solidification.

Prediction of the deflagration index for organic dusts as a function of the mean particle diameter

2017 ◽  
Vol 50 ◽  
pp. 67-74 ◽  
Author(s):  
Anna Fumagalli ◽  
Marco Derudi ◽  
Renato Rota ◽  
Jef Snoeys ◽  
Sabrina Copelli
Keyword(s):  
Particle Diameter ◽  
Deflagration Index ◽  
The Mean ◽  
Mean Particle Diameter

Influence of nucleating agent type on the morphology of extruded polyetherimide foam for printed circuit boards*

2019 ◽  
Vol 56 (3) ◽  
pp. 317-341 ◽  
Author(s):  
Clemens Keilholz ◽  
Daniel Raps ◽  
Thomas Köppl ◽  
Volker Altstädt
Keyword(s):  
Surface Tension ◽  
Printed Circuit Boards ◽  
Particle Diameter ◽  
Nucleating Agent ◽  
Nucleating Agents ◽  
Circuit Boards ◽  
Printed Circuit ◽  
Foam Morphology ◽  
The Mean ◽  
Mean Particle Diameter

This work focuses on the development of foamed high temperature thermoplastic substrates for printed circuit boards. For this application it is necessary to achieve mean cell diameters smaller than 30 µm in order to be able to realize vias and high packaging densities (miniaturization). Different additives as nucleating agents, namely macro- and micro-crystalline talc, silica, calcium carbonate, and wollastonite, were melt-compounded with polyetherimide using a twin-screw extruder. Foamed samples are prepared by foam extrusion using a slit die and CO2 as physical blowing agent. The aim of this study is to analyze the influence of the mean particle size and the particle surface tension on the mean cell diameters. Therefore, the shape of the additives, the foam morphology, and the elongational viscosity were considered. The additives with a suitable particle size and surface tension exhibit a positive influence on the foam morphology, resulting in smaller cell diameters (<30 µm), a narrower cell size distribution and a foam density lower than 900 kg/m3. If the mean particle diameter of the nucleating agents is lower than 0.6 µm in this study, no nucleation effect could be observed. This is related to the fact that no heterogeneous nucleation occurs, if the particle diameter is too small. If the mean particle diameter of the used additives is larger than 1.5 µm, which could be demonstrated in this study in case of polyetherimide, then the additive acts as nucleating agent and heterogeneous nucleation occurs. Furthermore, it was observed that the mean cell diameter was affected by the different surface tensions of the studied nucleating agents.

scholarly journals Snow particle characteristics in the saltation layer

2014 ◽  
Vol 60 (221) ◽  
pp. 431-439 ◽  
Author(s):  
Christof Gromke ◽  
Stefan Horender ◽  
Benjamin Walter ◽  
Michael Lehning
Keyword(s):  
Particle Size ◽  
Particle Number ◽  
Particle Diameter ◽  
Wind Tunnel Experiments ◽  
Scale Parameters ◽  
Particle Characteristics ◽  
Maximum Particle ◽  
The Mean ◽  
Snow Particle ◽  
Measurement Area

AbstractShadowgraphy was employed to study snow saltation in boundary-layer wind tunnel experiments with fresh, naturally deposited snow. The shadowgraphy method allowed for a temporally and spatially high-resolution investigation of snow particle characteristics within a measurement area of up to 50 mm × 50 mm. Snow particle size and number characteristics, and their variation with height in the saltation layer, were analysed. The following observations and findings were made for the saltation layer: (1) the particle number decreases exponentially with height, (2) the mean particle diameter is fairly constant, with a very slight tendency to decrease with height, (3) the maximum particle diameter decreases linearly with height, and (4) the snow particle size distribution can be adequately described by gamma probability density functions. The shape and scale parameters of the gamma distribution were found to vary systematically, though only slightly, with height over ground and between experiments with different snowpack characteristics.

Effect of Ion Exchange Resin Particle Size on X-Ray Fluorescent Analysis

1971 ◽  
Vol 15 ◽  
pp. 534-538
Author(s):  
A. L. Allen ◽  
V. C. Rose
Keyword(s):  
Particle Size ◽  
Copper Concentration ◽  
Exchange Resin ◽  
Particle Diameter ◽  
Ion Exchange Resin ◽  
General Shape ◽  
X Ray ◽  
A Minor ◽  
The Relationship ◽  
Mean Particle Diameter

The effect of resin particles on copper x-ray fluorescence was studied. For any given resin size the relationship between copper concentration and x-ray intensity was linear. As the particle size decreased, the x-ray intensity increased for any given copper concentration. The general shape of the curves are similar to the ones predicted by Bernstein for a minor constituent in a power sample. This study indicates that the variation in intensity with particle size can be eliminated by using resins with a mean particle diameter of 56 microns or less.

scholarly journals Size-resolved cloud condensation nuclei (CCN) activity and closure analysis at the HKUST Supersite in Hong Kong

2014 ◽  
Vol 14 (18) ◽  
pp. 10267-10282 ◽  
Author(s):  
J. W. Meng ◽  
M. C. Yeung ◽  
Y. J. Li ◽  
B. Y. L. Lee ◽  
C. K. Chan
Keyword(s):  
Particle Size ◽  
Hong Kong ◽  
Atmospheric Aerosols ◽  
Cloud Condensation Nuclei ◽  
Particle Diameter ◽  
Volume Ratio ◽  
Condensation Nuclei ◽  
Mixing State ◽  
Scanning Mobility Particle Sizer ◽  
The Mean

Abstract. The cloud condensation nuclei (CCN) properties of atmospheric aerosols were measured on 1–30 May 2011 at the HKUST (Hong Kong University of Science and Technology) Supersite, a coastal site in Hong Kong. Size-resolved CCN activation curves, the ratio of number concentration of CCN (NCCN) to aerosol concentration (NCN) as a function of particle size, were obtained at supersaturation (SS) = 0.15, 0.35, 0.50, and 0.70% using a DMT (Droplet Measurement Technologies) CCN counter (CCNc) and a TSI scanning mobility particle sizer (SMPS). The mean bulk size-integrated NCCN ranged from ~500 cm−3 at SS = 0.15% to ~2100 cm−3 at SS = 0.70%, and the mean bulk NCCN / NCN ratio ranged from 0.16 at SS = 0.15% to 0.65 at SS = 0.70%. The average critical mobility diameters (D50) at SS = 0.15, 0.35, 0.50, and 0.70% were 116, 67, 56, and 46 nm, respectively. The corresponding average hygroscopic parameters (κCCN) were 0.39, 0.36, 0.31, and 0.28. The decrease in κCCN can be attributed to the increase in organic to inorganic volume ratio as particle size decreases, as measured by an Aerodyne high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). The κCCN correlates reasonably well with κAMS_SR based on size-resolved AMS measurements: κAMS_SR = κorg × forg + κinorg × finorg, where forg and finorg are the organic and inorganic volume fractions, respectively, κorg = 0.1 and κinorg = 0.6, with a R2 of 0.51. In closure analysis, NCCN was estimated by integrating the measured size-resolved NCN for particles larger than D50 derived from κ assuming internal mixing state. Estimates using κAMS_SR show that the measured and predicted NCCN were generally within 10% of each other at all four SS. The deviation increased to 26% when κAMS was calculated from bulk PM1 AMS measurements of particles because PM1 was dominated by particles of 200 to 500 nm in diameter, which had a larger inorganic fraction than those of D50 (particle diameter < 200 nm). A constant κ = 0.33 (the average value of κAMS_SR over the course of campaign) was found to give an NCCN prediction within 12% of the actual measured values. We also compared NCCN estimates based on the measured average D50 and the average size-resolved CCN activation ratio to examine the relative importance of hygroscopicity and mixing state. NCCN appears to be relatively more sensitive to the mixing state and hygroscopicity at a high SS = 0.70% and a low SS = 0.15%, respectively.

scholarly journals Simulation of Blood Flow and Nanoparticle Transport in a Stenosed Carotid Bifurcation and Pseudo-Arteriole

2012 ◽  
Vol 4 (1) ◽  
pp. 85-101
Author(s):  
Graham Doig ◽  
Guan H. Yeoh ◽  
Victoria Timchenko ◽  
Gary Rosengarten ◽  
Tracie J. Barber ◽  
...  
Keyword(s):  
Residence Time ◽  
Particle Diameter ◽  
Carotid Bifurcation ◽  
Nanoparticle Transport ◽  
Particle Residence Time ◽  
Flow Through ◽  
The Mean ◽  
Particle Approach ◽  
Wall Interactions

Numerical simulation of flow through a realistic bifurcated carotid artery geometry with a stenosis has been conducted for comparison to experimental measurements. The behaviour of simplified therapeutic nanoparticles in relatively low concentration was observed using a discrete particle approach. The role of size (diameters from 500 nm to 50 nm) in determining particle residence time and the potential for both desirable and undesirable wall interactions was investigated. It was found that mean particle residence time reduced with decreasing particle diameter, and the percentage of particles experiencing one or more wall interactions increased simultaneously. Further simulations were conducted on a scaled-down version of the geometry which approximated the size and flow conditions of an arteriole with capillary branches, and in this instance the mean residence time increased with decreasing particle diameter, owing largely to the greater influence of Brownian motion. 33% of all 50 nm particles were involved in wall interactions, indicating that smaller particles would have a greater ability to target, for instance, cancerous tumours in such regions.

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