scholarly journals General nucleation-growth type kinetic models of nanoparticle formation: possibilities of finding analytical solutions

2021 ◽  
Author(s):  
Rebeka Szabó ◽  
Gábor Lente
Keyword(s):  
Analytical Solutions ◽  
Kinetic Models ◽  
Average Particle Size ◽  
Experimental Studies ◽  
Chemical Species ◽  
Average Particle ◽  
Growth Type ◽  
Nanoparticle Formation ◽  
Spontaneous Nucleation ◽  
Nucleation Growth

AbstractIn this work, analytical solutions for the time dependences for the concentration of each chemical species are determined in a class of nucleation-growth type kinetic models of nanoparticle formation. These models have an infinitely large number of dependent variables and describe the studied process without approximations. Symbolic solutions are found for the mass kernel (where reactivity is directly proportional to the mass of a nanoparticle) and the diffusion kernel (where reactivity is independent of the size of the nanoparticle). The results show that the average particle size is primarily determined by the type of the kernel function and the ratio of the rate constants of spontaneous nucleation and particle growth. The final distribution of nanoparticle sizes is a continuously decreasing function in each studied case. Furthermore, the time dependences of the concentrations of monomeric units show the induction behavior that has already been observed in many experimental studies.

Kinetics of Structural Changes in Strontium Hexa-Ferrite Powder during Milling in Beater Mill

2020 ◽  
Vol 989 ◽  
pp. 199-203
Author(s):  
Ivan N. Egorov ◽  
Nikolay Ya. Egorov ◽  
Viktor P. Kryzhanovsky
Keyword(s):  
Particle Size ◽  
Structural Characteristics ◽  
Average Particle Size ◽  
Experimental Studies ◽  
Milling Process ◽  
Strontium Hexaferrite ◽  
Average Particle ◽  
Relative Deformation ◽  
Ferrite Powder ◽  
Electromagnetic Effect

The paper presents the results of experimental studies of strontium hexa-ferrite average particle size and structural characteristics changes during milling process. Coarse strontium hexaferrite was milled in beater mill, without and with electromagnetic effect. Electromagnetic effect was produced by constant and alternating gradient magnetic fields with mutually perpendicular induction lines. Particle sizes were measured by microscopic methods, and structural characteristics were calculated by processing of X-ray diffractograms. Diffraction studies showed that during milling process, both with and without electromagnetic effect, the most intensive changes of coherent scattering region (CSR) sizes, dislocation densities and relative deformation of particulate material occur at earlier stage of milling. At this stage the speed of average particle size decrease is maximal. At later stage both average particle size and structural characteristic changes correlate and have asymptotic character.

scholarly journals Adsorption of phosphorus onto nanoscale zero-valent iron/activated carbon: removal mechanisms, thermodynamics, and interferences

2022 ◽  
Author(s):  
Adel Adly ◽  
Nagwan G. Mostafa ◽  
Abdelsalam Elawwad
Keyword(s):  
Activated Carbon ◽  
Removal Efficiency ◽  
Kinetic Models ◽  
Average Particle Size ◽  
Zero Valent Iron ◽  
Solution Temperature ◽  
Average Particle ◽  
Phosphorus Adsorption ◽  
Removal Mechanisms ◽  
Nanoscale Zero Valent Iron

Abstract This study investigated removal mechanisms, thermodynamics, and interferences of phosphorus adsorption onto nanoscale zero-valent iron (nZVI)/activated carbon composite. Activated carbon was successfully used as support for nZVI particles to overcome shortcomings of using nZVI include its tendency to aggregate and separation difficulties. A comprehensive characterization was done for the composite particles, which revealed a high specific surface area of 72.66 m2/g and an average particle size of 37 nm. Several adsorption isotherms and kinetic models have been applied to understand the removal mechanisms. Adsorption isotherm is best fitted by Freundlich and Langmuir models, which indicates that the estimated maximum phosphorus adsorption capacity is 53.76 mg/g at pH 4. Adsorption kinetics showed that the chemisorption process behaved according to a pseudo-second-order model. An adsorption mechanism study conducted using the intra-particle diffusion and Boyd kinetic models indicated that the adsorption rate is limited by surface diffusion. A thermodynamic study showed that phosphorus removal efficiency increased as the solution temperature increased from 15 to 37 °C. Finally, the results of an interference study showed that the presence of Ni2+, Cu2+, Ca2+, Na+ cations, nitrate ions (), and sodium acetate improves removal efficiency, while the presence of sulfate ions () and urea reduces removal efficiency.

scholarly journals Production and Characterization of Commercial Aluminum Powders by a New Nozzle Design and Atomization Unit

2021 ◽  
Vol 9 (12) ◽  
pp. 1259-1263
Author(s):  
Hakan Gokmese
Keyword(s):  
Particle Size ◽  
Average Particle Size ◽  
Experimental Studies ◽  
Average Particle ◽  
Powder Size ◽  
Gas Atomization ◽  
Pure Aluminium ◽  
Metal Powders ◽  
Important Place ◽  
Measuring Device

Abstract: A large area cross section of the production of spherical metal powders by gas atomization in the manufacturing method. Powder metal characteristic improves with small powder size. This aim was realized by vertical gas atomization unit, a new a closely-matched nozzle system and manufacture. In the experimental studies, pure aluminium powders which has an important place in the automotive, air and defence industries were produced. In the studies carried out with the Vertical Gas Atomization unit, aluminium was superheated up to 900°C and atomized at different gas pressures (20-30 bar). Scanning electron microscope (SEM) and particle size measuring device were used for the characterization and size measurements of the produced powders, respectively. The average particle size of the finest powder produced with increasing atomization pressure was determined as d50=19.50µm. Aluminium powder shape and morphology was used as spherical and very little satellization was seen. Keywords: Powder Metallurgy, Atomisation, Nozzle, Al powder, Characterisation

scholarly journals Influence of electromagnetic effect parameters on ferromagnetic powders fluidity

2018 ◽  
Vol 226 ◽  
pp. 03002
Author(s):  
Ivan N. Egorov ◽  
Nikolay Ya. Egorov
Keyword(s):  
Symmetry Axis ◽  
Average Particle Size ◽  
Experimental Studies ◽  
Barium Hexaferrite ◽  
Strontium Hexaferrite ◽  
Average Particle ◽  
Particle Sizes ◽  
Electromagnetic Effect ◽  
Flow Through ◽  
Particulate Medium

The paper presents result of experimental studies of ferromagnetic powders fluidity management by effecting on particulate medium with constant and alternating gradient magnetic fields. Induction lines of constant magnetic field are perpendicular to symmetry axis of powder hopper. Alternating field is created by electromagnet with one tapering pole and has higher induction gradient values near hopper outlet. These fields form magneto fluidized bed from powder in hopper allowing powders of barium and strontium hexaferrite to flow through the hopper outlet. Dependencies of efflux speed from parameters of electromagnetic fields are presented for barium hexaferrite powder with average particle size 1 μm and strontium hexaferrite powders with average particle sizes 1 and 9 μm.

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.

Structure and properties of electroerosive materials from lead bronze waste BrS30, obtained in oxygen- and carbon-containing media

2021 ◽  
pp. 309-312
Author(s):  
E.V. Ageev ◽  
A.S. Pereverzev
Keyword(s):  
Particle Size ◽  
Chemical Composition ◽  
Average Particle Size ◽  
Experimental Studies ◽  
Average Particle ◽  
Distilled Water ◽  
Structure And Properties ◽  
Technological Parameters ◽  
Elliptical Shape

The results of experimental studies of the structure and properties of electroerosive materials from lead bronze waste BrS30 obtained in oxygen- and carbon-containing media are presented. The influence of the chemical composition of liquids and technological parameters of dispersion on the properties of the resulting electroerosive materials is shown. In particular, a part of oxygen is present on the surface of particles obtained in distilled water, and part of carbon is present in lighting kerosene. The average particle size obtained in lighting kerosene is 1.2 times higher than the average particle size obtained in distilled water. The particles of the BrS30 alloy dispersed by electroerosion have a regular spherical, elliptical shape and agglomerates.

A discussion on advanced methods of energy conversion- Magnetohydrodynamic power generation - An experimental study of gas borne suspensions of thermionic emitters as m .h.d. working fluids

1967 ◽  
Vol 261 (1123) ◽  
pp. 490-495 ◽  
Keyword(s):  
Atmospheric Pressure ◽  
Average Particle Size ◽  
Experimental Studies ◽  
Barium Oxide ◽  
Inert Gases ◽  
Average Particle ◽  
Experimental Conditions ◽  
Working Fluids ◽  
Electrical Conductivities ◽  
Oxide Particles

The use of gaseous suspensions of thermionically emitting particles as alternatives to alkali metal seeded gases for use as m.h.d. working fluids is discussed briefly. Theoretical relations proposed by Sodha & Bendor (1964) are used to show that suspensions of barium oxide in argon can have significantly higher electrical conductivities than thermally ionized caesium-argon mixtures at temperatures below about 2000 °K. This advantage is emphasized at pressures above atmospheric pressure. Experimental studies to check the theoretically predicted conductivities are described. A technique has been developed for the preparation of submicron suspensions of barium oxide and other alkali earth oxides in inert gases. A suspension of barium oxide particles in argon has been shown to have a conductivity of 0-1 mho/m at atmospheric pressure and 1600 °K. This value is low, because of the relatively large average particle size, 0-3 ^m diameter, but is of the same order as the theoretical conductivity for the experimental conditions.

scholarly journals A novel and green nanoparticle formation approach to forming low-crystallinity curcumin nanoparticles to improve curcumin’s bioaccessibility

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Ali Ubeyitogullari ◽  
Ozan N. Ciftci
Keyword(s):  
Average Particle Size ◽  
Average Particle ◽  
Nanoparticle Formation ◽  
Curcumin Nanoparticles ◽  
Novel Approach ◽  
Health Promoting ◽  
Formation Method ◽  
20 Nm ◽  
Bioaccessible Fraction ◽  
Low Crystallinity

AbstractHealth-promoting effects of curcumin are well-known; however, curcumin has a very low bioavailability due to its crystalline structure. The main objective of this study was to develop a novel green nanoparticle formation method to generate low-crystallinity curcumin nanoparticles to enhance the bioavailability of curcumin. Nanoporous starch aerogels (NSAs) (surface area of 60 m2/g, pore size of 20 nm, density of 0.11 g/cm3, and porosity of 93%) were employed as a mold to produce curcumin nanoparticles with the help of supercritical carbon dioxide (SC-CO2). The average particle size of the curcumin nanoparticles was 66 nm. Impregnation into NSAs decreased the crystallinity of curcumin and did not create any chemical bonding between curcumin nanoparticles and the NSA matrix. The highest impregnation capacity was 224.2 mg curcumin/g NSA. Curcumin nanoparticles significantly enhanced the bioaccessibility of curcumin by 173-fold when compared to the original curcumin. The concentration of curcumin in the bioaccessible fraction was improved from 0.003 to 0.125 mg/mL by impregnation of curcumin into NSAs (42-fold). This is a novel approach to produce food grade curcumin nanoparticles with reduced crystallinity and maximize the utilization of curcumin due to increased bioaccessibility.

scholarly journals Structural, morphological and optical properties of Mn doped ZnS nanocrystals

Cerâmica ◽  
2013 ◽  
Vol 59 (352) ◽  
pp. 614-619 ◽  
Author(s):  
V. D. Mote ◽  
Y. Purushotham ◽  
B. N. Dole
Keyword(s):  
Optical Properties ◽  
Average Particle Size ◽  
Chemical Species ◽  
Average Particle ◽  
Secondary Phases ◽  
Zinc Blend ◽  
Composition Formula ◽  
Xrd Patterns ◽  
Mn Concentration ◽  
Mn Doped

Mn doped ZnS samples with composition formula Zn1-xMn xS where x = 0, 0.02, 0.05 and 0.10 were prepared by chemical method. Samples characterized for its structural, morphological and optical properties by X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) and UV-vis spectrometry. XRD patterns confirm cubic zinc blend structure with no secondary phases for pure and Mn doped ZnS. Lattice constant value increases slightly with Mn concentration due to the substitution of Mn in ZnO lattice. TEM images show that the particles have spherical in shape with an average particle size 3-4 nm. The chemical species of the grown crystals are identified by FTIR spectra. Optical absorption spectra show decrement in band gap with increasing Mn concentration.

scholarly journals Structural, morphological and optical properties of Mn doped ZnS nanocrystals

Cerâmica ◽  
2013 ◽  
Vol 59 (351) ◽  
pp. 395-400 ◽  
Author(s):  
V. D. Mote ◽  
Y. Purushotham ◽  
B. N. Dole
Keyword(s):  
Optical Properties ◽  
Average Particle Size ◽  
Chemical Species ◽  
Average Particle ◽  
Secondary Phases ◽  
Zinc Blend ◽  
Composition Formula ◽  
Xrd Patterns ◽  
Mn Concentration ◽  
Mn Doped

Mn doped ZnS samples with composition formula Zn1-xMn xS where x = 0.00, 0.02, 0.05 and 0.10 were prepared by chemical method. Samples characterized for its structural, morphological and optical properties by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and UV-vis spectrometer. XRD patterns confirm cubic zinc blend structure with no secondary phases for pure and Mn doped ZnS. Lattice constant value increases slightly with Mn concentration due to the substitution of Mn in ZnS lattice. TEM images show that the particles have spherical in shape with an average particle size between 3-4 nm. The chemical species of the grown crystals are identified by FTIR spectra. Optical absorption spectra show decrement in band gap with increasing Mn concentration.

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