scholarly journals Reducing the Induction Time Using Ultrasound and High-Shear Mixing in a Continuous Crystallization Process

Crystals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 326 ◽  
Author(s):  
Arne Vancleef ◽  
Stijn Seurs ◽  
Jeroen Jordens ◽  
Tom Van Gerven ◽  
Leen C. J. Thomassen ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Induction Time ◽  
Average Particle ◽  
High Shear ◽  
Ultrasound Probe ◽  
Nucleation Behavior ◽  
Continuous Crystallization ◽  
Shear Mixing

Continuous crystallization in tubular crystallizers is of particular interest to the pharmaceutical industry to accurately control average particle size, particle size distribution, and (polymorphic) shape. However, these types of crystallizers require fast nucleation, and thus, short induction times at the beginning of the flow process, which is challenging for larger and complex organic molecules. High shear and/or the presence of bubbles were identified to influence the nucleation behavior. This work investigates the effects of both high-shear mixing and ultrasound on the anti-solvent crystallization of paracetamol in acetone–water. Both devices generate intense amounts of shear and gas bubbles. Generally, the results show that increasing input power decreases the induction time significantly for both the rotor–stator mixer and ultrasound probe. However, the induction time is almost independent of the supersaturation for the ultrasound probe, while the induction time significantly increases with decreasing supersaturation for the rotor–stator mixer. In contrast, the particle size distribution for the rotor–stator mixer is independent of the supersaturation, while increasing supersaturation decreases the particle size for the ultrasound probe.

Effects of Multiple Impacts and Size Distribution of Particles on Erosion Predictions Using CFD

2007 ◽  
Author(s):  
Yongli Zhang ◽  
Brenton S. McLaury ◽  
Siamack A. Shirzai
Keyword(s):  
Experimental Data ◽  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Target Material ◽  
Average Particle ◽  
Multiple Impacts ◽  
Cfd Simulations ◽  
Erosion Damage ◽  
Wide Range

Erosion equations are usually obtained from experiments by impacting solid particles entrained in a gas or liquid on a target material. The erosion equations are utilized in CFD (Computational Fluid Dynamics) models to predict erosion damage caused by solid particle impingements. Many erosion equations are provided in terms of an erosion ratio. By definition, the erosion ratio is the mass loss of target material divided by the mass of impacting particles. The mass of impacting particles is the summation of (particle mass × number of impacts) of each particle. In erosion experiments conducted to determine erosion equations, some particles may impact the target wall many times and some other particles may not impact the target at all. Therefore, the experimental data may not reflect the actual erosion ratio because the mass of the sand that is used to run the experiments is assumed to be the mass of the impacting particles. CFD and particle trajectory simulations are applied in the present work to study effects of multiple impacts on developing erosion ratio equations. The erosion equation as well as the CFD-based erosion modeling procedure is validated against a variety of experimental data. The results show that the effect of multiple impacts is negligible in air cases. In water cases, however, this effect needs to be accounted for especially for small particles. This makes it impractical to develop erosion ratio equations from experimental data obtained for tests with sand in water or dense gases. Many factors affecting erosion damage are accounted for in various erosion equations. In addition to some well-studied parameters such as particle impacting speed and impacting angle, particle size also plays a significant role in the erosion process. An average particle size is usually used in analyzing experimental data or estimating erosion damage cases of practical interest. In petroleum production applications, however, the size of sand particles that are entrained in produced fluids can vary over a fairly broad range. CFD simulations are also performed to study the effect of particle size distribution. In CFD simulations, particle sizes are normally distributed with the mean equaling the average size of interest and the standard deviation varying over a wide range. Based on CFD simulations, an equation is developed and can be applied to account for the effect of the particle size distribution on erosion prediction for gases and liquids.

scholarly journals Particle Size Distribution of E-Cigarette Aerosols and the Relationship to Cambridge Filter Pad Collection Efficiency

2015 ◽  
Vol 26 (4) ◽  
Author(s):  
Steven L. Alderman ◽  
Chen Song ◽  
Serban C. Moldoveanu ◽  
Stephen K. Cole
Keyword(s):  
Particle Size ◽  
Particulate Matter ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Propylene Glycol ◽  
Collection Efficiency ◽  
Transmission Measurement ◽  
Average Particle ◽  
Electrical Mobility ◽  
Total Particulate Matter

AbstractThe relatively volatile nature of the particulate matter fraction of e-cigarette aerosols presents an experimental challenge with regard to particle size distribution measure-ments. This is particularly true for instruments requiring a high degree of aerosol dilution. This was illustrated in a previous study, where average particle diameters in the 10-50 nm range were determined by a high-dilution, electrical mobility method. Total particulate matter (TPM) masses calculated based on those diameters were orders of magnitude smaller than gravimetrically determined TPM. This discrepancy was believed to result from almost complete particle evaporation at the dilution levels of the electrical mobility analysis. The same study described a spectral transmission measurement of e-cigarette particle size in an undiluted state, and reported particles from 210-380 nm count median diameter. Observed particle number concentrations were in the 10Described here is a study in which e-cigarette aerosols were collected on Cambridge filters with adsorbent traps placed downstream in an effort to capture any material passing through the filter. Amounts of glycerin, propylene glycol, nicotine, and water were quantified on the filter and downstream trap. Glycerin, propylene glycol, and nicotine were effciently captured (> 98%) by the upstream Cambridge filter, and a correlation was observed between filtration efficiency and the partial vapor pressure of each component. The present analysis was largely inconclusive with regard to filter efficiency and particle-vapor partitioning of water. [Beitr. Tabakforsch. Int. 26 (2014) 183-190]

Particle Size Distribution of ZrO2:Pr3+ – Influences of pH, High Power Ultrasound, Surfactant and Dopant Quantity

2007 ◽  
Vol 128 ◽  
pp. 97-100 ◽  
Author(s):  
Stephanie Möller ◽  
Janusz D. Fidelus ◽  
Witold Łojkowski
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
High Power ◽  
Average Particle Size ◽  
Sodium Dodecyl ◽  
Average Particle ◽  
Power Ultrasound ◽  
High Power Ultrasound ◽  
Influence Of Ph

The aim of the work was to examine the influence of pH, high power ultrasound, surfactant and dopant quantity on the particle size distribution of ZrO2:Pr3+, with praseodymium content varying between 0.05 and 10 %. The nanopowders were obtained via a hydrothermal microwave driven process. To establish if the dopant was located on the surface of the zirconia nanoparticles, the particle size distribution, as a function of pH, was measured to obtain an estimate of the isoelectric point of the samples. All results indicated that the dopant was concentrated on the surface: the measurements of the particle size distribution show that the pH corresponding to maximum average particle size changes towards higher values when the Pr content increases. Measurements of the particle size distribution dependency on the application of high power ultrasound and the addition of the sodium dodecyl sulphate surfactant show that, under certain conditions, there is a better stabilisation of the nanopowders in a dispersion and undesirable agglomeration is hindered.

News from the M in CMP - Viscosity of CMP Slurries, a Constant?

2003 ◽  
Vol 767 ◽  
Author(s):  
W. Lortz ◽  
F. Menzel ◽  
R. Brandes ◽  
F. Klaessig ◽  
T. Knothe ◽  
...  
Keyword(s):  
Particle Size ◽  
Shear Rate ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
High Shear Rate ◽  
Bet Surface Area ◽  
Energy Concentration ◽  
High Shear ◽  
Polishing Pad ◽  
Distribution Shape

AbstractIt is well known and accepted that the viscosity of CMP-slurries has an effect on polishing results. Even though the literature on rheology recognizes that viscosity is not always constant and the slurry can show non-Newtonian behavior or even dilatant effects, all calculations have been performed with constant viscosity.However, the “real” viscosity of a CMP-slurry during polishing can change significantly with shear rate.The typical equipment for viscosity measurement is based on a rotating cylinder or a plate. But even with a plate system it is only possible to reach a shear rate range up to 50,000 1/sec. A calculation of the shear rate between the wafer and the polishing pad is based on a relative velocity of 1 m/sec and a distance between the wafer and the pad of 20 μm; this correlates to a shear rate of 50,000 1/sec. If parts of the polishing pad come closer to the wafer or especially closer to the edge of structures on the wafer (for example 1 μm), the shear rate will increase locally to 1,000,000 1/sec.When the shear rate is high enough, viscosity depends mostly on hydrodynamic factors like viscosity of continuos phase, solids content, particle size, particle size distribution and shape of the particles.The shape of fumed metal oxides is controlled during the synthesis in the flame process. But the slurry-making process is also responsible for particle size distribution, shape of the particle and the high shear rate viscosity of the CMP-slurry.The high shear rate viscosity of different silica slurries in dependence from BET-surface area, used milling energy, concentration and preparation direction was measured in this investigation.

The Influence of Milling Regimes in Beater Mill on Particle Size Distribution and Structural Characteristics of Strontium Hexaferrite Powder

2018 ◽  
Vol 284 ◽  
pp. 158-162
Author(s):  
I.N. Yegorov ◽  
Nikolay Ya. Egorov
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Fluidized Bed ◽  
Structural Parameters ◽  
Average Particle Size ◽  
Strontium Hexaferrite ◽  
Average Particle ◽  
Electromagnetic Effect ◽  
Coarse Material

The paper experimentally substantiates effectiveness of method of milling particulate ferromagnetic materials in magneto fluidized bed. Comparative results of particle size distributions and structural parameters of strontium hexaferrite SrFe12O19 powder obtained by milling coarse material in beater mill without electromagnetic effect and in same mill with formation of magneto fluidized bed from mill material are presented. The magneto fluidized bed is formed by constant and alternating gradient magnetic fields with induction lines that are mutually perpendicular and parallel to the plane of rotating beaters. It is shown that application of electromagnetic effect to milling coarse material in beater mill allowed to greatly intensify that process, significantly increase powder quality: increase particle size distribution uniformity and decrease average particle size from 1558.50 μm to 0.56 μm after 120 minutes of processing in the mill. X-ray diffraction analysis showed that milling in beater mill in magneto fluidized bed leads to reduction of coherent-scattering region size, increase of lattice microstrain and dislocation density, making powder more active during sintering process.

Obtaining and Research of Additive Products from Electro-Erosive Cobalt-Chrome Powders

2020 ◽  
Vol 989 ◽  
pp. 801-805
Author(s):  
Evgeniy V. Ageev ◽  
O.G. Loktionova ◽  
A.Y. Altukhov
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Average Particle Size ◽  
Experimental Studies ◽  
Average Particle ◽  
Cobalt Chromium ◽  
Technical Literature ◽  
Specific Particle ◽  
Cobalt Chrome

The main requirement for powders for additive machines is the spherical shape of the particles. Such particles most compactly fit into a certain volume and provide the “fluidity” of the powder composition in the material supply systems with minimal resistance. Based on the peculiarities of the methods of obtaining spherical powders in order to obtain spherical granules of a regulated grain size, the technology of electroerosive dispersion, which is distinguished by relatively low energy costs and ecological cleanliness of the process, is proposed. The main advantage of the proposed technology is the use of waste as raw materials, which is much cheaper than the pure components used in traditional technologies. In addition, this technology is powder, which allows to obtain powder-alloys. The widespread use of the method of EED for the processing of metal waste into powders for the purpose of their reuse and application in additive technologies is hampered by the lack of complete information in the scientific and technical literature on the influence of the original composition, modes and media on the properties of powders and technologies of practical application. Therefore, the development of technologies for the reuse of EED powders and the evaluation of the effectiveness of their use requires the conduct of comprehensive theoretical and experimental studies. The purpose of this work was to obtain and study additive products from electroerosive cobalt-chromium powders of a specific particle size distribution and to study their microstructure. The granulometry of the obtained powders was determined on a laser analyzer of particle sizes “Analysette 22 NanoTec”. The microstructure of additive samples from cobalt-chromium powders (by transverse polishing) was investigated by optical microscopy on an inverted optical microscope OLYMPUS GX51. On the basis of completed studies, aimed at obtaining and studying additive products from electroerosive cobalt-chrome powders of a specific particle size distribution, and studying their microstructure, it was found that additive samples, obtained from a cobalt-chrome powder with an average particle size of 35,68 microns, have practically no pores.

scholarly journals Preparation and Characterization of NiO Nanoparticles by Anodic Arc Plasma Method

2009 ◽  
Vol 2009 ◽  
pp. 1-5 ◽  
Author(s):  
Hongxia Qiao ◽  
Zhiqiang Wei ◽  
Hua Yang ◽  
Lin Zhu ◽  
Xiaoyan Yan
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Specific Surface ◽  
Size Distribution ◽  
Surface Area ◽  
Specific Surface Area ◽  
Average Particle Size ◽  
Average Particle ◽  
Arc Plasma ◽  
Nio Nanoparticles

NiO nanoparticles with average particle size of 25 nm were successfully prepared by anodic arc plasma method. The composition, morphology, crystal microstructure, specific surface area, infrared spectra, and particle size distribution of product were analyzed by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and the corresponding selected area electron diffraction (SAED), Fourier transform infrared (FTIR) spectrum, and Brunauer-Emmett-Teller (BET)N2adsorption. The experiment results show that the NiO nanoparticles are bcc structure with spherical shape and well dispersed, the particle size distribution ranging from 15 to 45 nm with the average particle size is about 25 nm, and the specific surface area is 33 m2/g. The infrared absorption band of NiO nanoparticles shows blue shifts compared with that of bulk NiO.

Preparation of Monodispersed and Nano-Sized Spherical SiO2 Particles by Emulsion Method

2004 ◽  
Vol 449-452 ◽  
pp. 1161-1164 ◽  
Author(s):  
Jong Hwa Baek ◽  
Young Soo Kang ◽  
Seog Young Yoon ◽  
Hong Chae Park
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Mixing Time ◽  
Average Particle Size ◽  
Average Particle ◽  
Amorphous Sio2 ◽  
Emulsion Method ◽  
Sio2 Particles ◽  
20 Nm

Spherical nano-sized SiO2 particles have been synthesized from sodium silicate by emulsion method. The influence of emulsifier content and mixing time on the morphology and particle size distribution of the resulting materials was investigated. The characteristics of the obtained SiO2 particles were examined by means of XRD, SEM, TEM, and PSA. The monodispersed shperical SiO2 with the average particle size 20 nm was obtained at a emulsifer content of 3vol% and mixing time of 60 min using ultrasonic disruptor. After calcining at 1200oC for 2 hrs, the amorphous SiO2 transformed wholly to the crystalline cristobalite. As increase in emulsifier content from 1 to 3 vol% did not nearly influence on the morphology of SiO2 particle but slightly changed the particle size distribution. The average particle size of SiO2 decreased significantly from 100 nm to 20 nm with increasing the mixing time.

Effects of Addition Amount, Particle Size Distribution and Average Particle Size of NaCl Porogen on the Pore Connectivity of Silk Fibroin (SF) /Hydroxyapatite (HA) Porous Composites

2011 ◽  
Vol 332-334 ◽  
pp. 1904-1909
Author(s):  
Zhen Ran Xia ◽  
Miao Liang Luo ◽  
Qin Zhang ◽  
Jing Qu ◽  
Ming Zhong Li
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Silk Fibroin ◽  
Average Particle Size ◽  
Bone Tissue Regeneration ◽  
Average Particle ◽  
Pore Connectivity ◽  
Porous Composites ◽  
Addition Amount

In order to investigate the effects of addition amount, particle size distribution and aver- age particle size of NaCl porogen on the pore connectivity of silk fibroin (SF) / hydroxyapatite (HA) porous composites. In this paper, the SF/HA composites were fabricated by means of isostatic pressing. The pore structure of SF/HA porous composites was observed by Scanning electron microscopy (SEM), and the air permeability was tested by home-made device. Results indicated that the larger addition amount of NaCl particles, the greater scope of NaCl particles size distribution and increased the average particle size of NaCl particles were able to make the pore connectivity of the material improved significantly. The materials with good pore connectivity, which were conducive to the immigration and adhesion of bone repair cells, information transmission and exchange with the outside tissue, and also benefit for bone tissue regeneration.

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