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 The role of mixing layer on changes of particle properties in lower troposphere

2009 ◽  
Vol 9 (4) ◽  
pp. 16483-16525
Author(s):  
L. Ferrero ◽  
E. Bolzacchini ◽  
M. G. Perrone ◽  
S. Petraccone ◽  
G. Sangiorgi ◽  
...  
Keyword(s):  
Size Distribution ◽  
Mixing Layer ◽  
Particle Diameter ◽  
Lower Troposphere ◽  
Atmospheric Particulate Matter ◽  
Vertical Profiles ◽  
Stable Conditions ◽  
The Mean ◽  
Hierarchical Statistical Model ◽  
Mean Particle Diameter

Abstract. Vertical profiles of atmospheric particulate matter number concentration, size distribution and chemical composition were directly measured in the city of Milan, over three years (2005–2008) of field campaigns. An optical particle counter, a portable meteorological station and a miniaturized cascade impactor were deployed on a tethered balloon. Mixing layer height was estimated by PM dispersion along height. More than 300 PM vertical profiles were measured both in the winter and summer, mainly in clear and dry sky conditions. Under these conditions, no significant changes in NO3−, SO42− or NH4+ into or over the mixing layer were found. From experimental measurements we observed changes in size distribution along height. An increase of the mean particle diameter, in the accumulation mode, passing through the mixing layer under stable conditions was highlighted; the mean relative growth was 2.1±0.1% in the winter and 3.9±0.3% in the summer. At the same time, sedimentation processes occurred across the ML height for coarse particles leading to a mean particle diameter reduction (14.9±0.6% in the winter and 10.7±1.0% in summer). A hierarchical statistical model for the PM size distribution has been developed to describe the aging process of the finest PM fraction along height. The proposed model is able to estimate the typical vertical profile that characterises launches within pre-specified groups. The mean growth estimated on the basis of the model was 1.9±0.5% in the winter and 6.1±1.2% in the summer, in accordance with experimental evidence.

Number concentration dependence of ultrasonic disruption ratio of diameter-sorted microcapsules

2022 ◽  
pp. 095441192110703
Author(s):  
Junsyou Kanashima ◽  
Naohiro Sugita ◽  
Tadahiko Shinshi
Keyword(s):  
Drug Delivery Systems ◽  
Focused Ultrasound ◽  
Particle Number ◽  
Particle Diameter ◽  
Number Concentration ◽  
The Mean ◽  
And Control ◽  
Polymer Shells ◽  
Filtration Technique ◽  
Mean Particle Diameter

The use of ultrasound to destroy microcapsules in microbubble-assisted drug delivery systems (DDS) is of great interest. In the present study, the disruption ratios of capsule clusters were measured by observing and experimentally analyzing microcapsules with polymer shells undergoing disruption by ultrasound. The microcapsules were dispersed in a planar microchamber filled with a gelatin gel and sonicated using 1 MHz focused ultrasound. Different capsule populations were obtained using a filtration technique to modify and control the capsule sizes. The disruption ratio as a function of the concentration of capsules was obtained through image processing of the recorded photomicrographs. We found that the disruption ratio for each population exponentially decreases as the particle number concentration (PNC) increases. The maximum disruption ratio of the diameter-sorted capsules was larger than that of polydispersed capsules. Particularly, for resonant capsule populations, the ratio was more than twice that of polydispersed capsules. Furthermore, the maximum disruption ratio occurred at higher concentrations as the mean particle diameter of the capsule cluster decreased.

Experimental Study of Water and Air Based Permeabilities of Washed and Screened Sands

2005 ◽  
Author(s):  
Shu-Ye Lei
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Porous Media ◽  
Particle Diameter ◽  
Velocity Slip ◽  
Slip Effect ◽  
Slip Effects ◽  
Water Based ◽  
The Mean ◽  
Mean Particle Diameter

The permeability of narrow screened washed sands of granularity 100–450 μm was measured experimentally using water and air to investigate the effect of slip on the gas based permeability. The experimental data show that the air based permeability of the unconsolidated particle media is not proportional to the square of the mean particle diameter and that slip significantly affects the air based permeability measurements for unconsolidated porous media. The velocity slip effect is significant even for Kn&lt;10−3. Slip effects were not found in the water based permeability measurements with the same sand samples. All of the experimental data lay around the curve k/d=0.283φ2.67 within ± 4.1%. However, the water based permeability was not below all of the air based permeability as expected. The air based permeability eliminated slip effects was about 59 % lower than that water based one, much larger than possible measurement. The experimental results showed that the standard air viscosity value in the handbooks was not its actual, the actual air viscosity may be over twice of that in handbooks.

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.

Luminescent and Photocatalytic Properties of BaCoF4: Ce3+ Synthesized by Reflux Method

2013 ◽  
Vol 341-342 ◽  
pp. 64-68
Author(s):  
Yan Xia Han ◽  
Qiu Hua Yang ◽  
Hai Yun Shen
Keyword(s):  
High Pressure ◽  
Ethylene Glycol ◽  
Degradation Rate ◽  
Particle Diameter ◽  
Emission Peak ◽  
Surface Oxygen ◽  
Mercury Lamp ◽  
The Mean ◽  
Mean Particle Diameter ◽  
Luminescent Spectrum

The complex fluorides BaCoF4and BaCoF4: Ce3+were synthesized by reflux method in ethylene glycol and characterized by means of XRD, TEM, XPS, UV-VIS and Fluorescence Spectrophotometer. In addition, the photocatalytic degradation property of BaCoF4: Ce3+was investigated. The results indicated that the mean particle diameter of BaCoF4was 54.6 nm. Only adsorption oxygen (α oxygen) existed on the surface of BaCoF4and the content of surface oxygen was 5%. The BaCoF4: Ce3+had a stronger absorption at 250 nm, which could be explained by d electronic transition of Ce3+. The maximum emission peak of BaCoF4: Ce3+was 361.8 nm in its luminescent spectrum, and emission band of Ce3+belonged to 5d4f transition. Meanwhile, the degradation rate of acid red 3B by BaCoF4: Ce3+reached 98.7% after being lightened for 2 h by a 450 W high pressure mercury lamp.

scholarly journals Nanoparticle coagulation and dispersion in a turbulent planar jet with constraints

2012 ◽  
Vol 16 (5) ◽  
pp. 1497-1501 ◽  
Author(s):  
Cheng-Xu Tu ◽  
Song Liu
Keyword(s):  
Standard Deviation ◽  
Dynamic Equation ◽  
Moment Method ◽  
Particle Diameter ◽  
Geometric Standard Deviation ◽  
Spatiotemporal Evolution ◽  
Planar Jet ◽  
The Mean ◽  
Mean Particle Diameter ◽  
General Dynamic

Numerical simulations of coagulating and dispersing nanoparticles in an incompressible turbulent planar jet with constraints are performed. The evolution of nanoparticle field is obtained by utilizing a moment method to approximate the particle's general dynamic equation. The spatiotemporal evolution of the first three moments along with the mean particle diameter and geometric standard deviation of particle diameter are discussed

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