Diagnostic of Structural Changes in Ferromagnetic Powders during Milling in Beater Mill

2021 ◽  
Vol 316 ◽  
pp. 187-192
Author(s):  
I.N. Egorov ◽  
S.I. Egorova ◽  
G.F. Lemeshko
Keyword(s):  
Particle Size ◽  
Fluidized Bed ◽  
Structural Changes ◽  
Structural Characteristics ◽  
Average Particle Size ◽  
Coherent Scattering ◽  
Milling Process ◽  
Average Particle ◽  
Ferrite Powder ◽  
Great Decrease

Problem of obtaining fine powders of strontium hexa-ferrite is actual because of its wide applications. The paper provides the results of studies of particle size distribution and structural characteristic changes of strontium hexa-ferrite powder (SrFe12O19) during milling in impact mill and after its consequent annealing. Mechanical processing of coarse particulate system was carried out in the mill for 120 minutes without electromagnetic effect and with creation of magneto fluidized bed, formed by perpendicular constant and alternating magnetic field with induction gradient of 210 mT/m, providing reciprocating motion of particles and aggregates with sizes of 3 – 4 mm. It was shown that milling of coarse strontium hexa-ferrite with average particle size 1558.5 μm and the most possible size 1500 μm in magneto fluidized bed allowed to intensify milling process and to provide a significant increase of powder particle sizes uniformity. It was found out, that milling in magneto fluidized bed leads to a great decrease of coherent scattering regions sizes and an increase of lattice micro-deformations and relative dislocation density. Consequent annealing of the powder for 2 hours at 850°C refined structural characteristics significantly. The carried out research allows to choose the optimal milling duration for solution of practical problems of powder metallurgy.

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.

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.

scholarly journals Improving the CO and CH4 Gas Sensor Response at Room Temperature of α-Fe2O3(0001) Epitaxial Thin Films Grown on SrTiO3(111) Incorporating Au(111) Islands

Coatings ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 848
Author(s):  
Aída Serrano ◽  
Jesús López-Sánchez ◽  
Iciar Arnay ◽  
Rosalía Cid ◽  
María Vila ◽  
...  
Keyword(s):  
Particle Size ◽  
Room Temperature ◽  
Gas Sensing ◽  
Structural Characteristics ◽  
Average Particle Size ◽  
Average Particle ◽  
Epitaxial Thin Films ◽  
Before And After ◽  
Crystallographic Axes ◽  
Gas Exposure

In this work, the functional character of complex α-Fe2O3(0001)/SrTiO3(111) and Au(111) islands/α-Fe2O3(0001)/SrTiO3(111) heterostructures has been proven as gas sensors at room temperature. Epitaxial Au islands and α-Fe2O3 thin film are grown by pulsed laser deposition on SrTiO3(111) substrates. Intrinsic parameters such as the composition, particle size and epitaxial character are investigated for their influence on the gas sensing response. Both Au and α-Fe2O3 layer show an island-type growth with an average particle size of 40 and 62 nm, respectively. The epitaxial and incommensurate growth is evidenced, confirming a rotation of 30° between the in-plane crystallographic axes of α-Fe2O3(0001) structure and those of SrTiO3(111) substrate and between the in-plane crystallographic axes of Au(111) and those of α-Fe2O3(0001) structure. α-Fe2O3 is the only phase of iron oxide identified before and after its functionalization with Au nanoparticles. In addition, its structural characteristics are also preserved after Au deposition, with minor changes at short-range order. Conductance measurements of Au(111)/α-Fe2O3(0001)/SrTiO3(111) system show that the incorporation of epitaxial Au islands on top of the α-Fe2O3(0001) layer induces an enhancement of the gas-sensing activity of around 25% under CO and 35% under CH4 gas exposure, in comparison to a bare α-Fe2O3(0001) layer grown on SrTiO3(111) substrates. In addition, the response of the heterostructures to CO gas exposure is around 5–10% higher than to CH4 gas in each case.

SYNTHESIS OF RELATIVELY HIGHLY MAGNETIC NANO-SIZED NiZn-FERRITE IN MICROEMULSION AT 45°C

2005 ◽  
Vol 12 (01) ◽  
pp. 97-100 ◽  
Author(s):  
VUK USKOKOVIĆ ◽  
MIHA DROFENIK
Keyword(s):  
Particle Size ◽  
Qualitative Analysis ◽  
Saturation Magnetization ◽  
Average Particle Size ◽  
Average Particle ◽  
Precipitation Reaction ◽  
Ferrite Powder

The procedure for the preparation of NiZn-ferrite powder with average particle size of 10 nm and saturation magnetization of 50 emu/g by using precipitation reaction between acidified sulphate precursor salts and NH4OH as the precipitating agent in the water-in-oil domain of the microemulsion CTAB/1-hexanol/water at 45°C is presented herein. TEM measurements have revealed relatively uniform morphology of the particles, which are associated in coral-like agglomerates. EDS measurements have been used for qualitative analysis of the sample, whereby FAAS measurement has been performed in order to reveal the proportion of the cations in the sample — Ni : Zn : Fe = 0.17 : 0.18 : 2.64.

Milling Duration Influence on Strontium Hexaferrite Technological Characteristics

2021 ◽  
Vol 410 ◽  
pp. 730-734
Author(s):  
Ivan N. Egorov ◽  
Nikolay Ya. Egorov ◽  
Svetlana I. Egorova
Keyword(s):  
Particle Size ◽  
Powder Metallurgy ◽  
Bulk Density ◽  
Fluidized Bed ◽  
Average Particle Size ◽  
Strontium Hexaferrite ◽  
Average Particle ◽  
Actual Problem ◽  
Technological Characteristics ◽  
Milling Duration

Fine powders of strontium hexaferrite are widely used in powder metallurgy for the production of permanent magnets resistant to atmospheric oxygen and high working temperatures. Obtaining powders with predefined technological characteristics in minimal time and with minimal energy consumption is an actual problem of powder metallurgy. The paper provides the results of experimental studies of technological characteristics of strontium hexaferrite powder (SrFe12O19) during milling in a beater mill. Mechanical milling of coarse strontium hexaferrite was carried out in the mill with the system of rotating beaters for 120 minutes without and with the creation of a pseudo fluidized bed. The fluidization was formed by a perpendicular constant and alternating magnetic field with induction gradients of 150 and 210 mT/m. Average particle size and powder bulk density dependencies from milling time were studied. Experimental data show that milling with the formation of a magneto fluidized bed allows intensifying the process. Beginning from 70 minutes, the dependencies of average particle size and bulk density come to almost asymptotic behavior making further milling rather ineffective. Carried out research allows choosing optimal milling duration for obtaining the required average particle size.

scholarly journals Phase Transformation and Morphology Evolution of Ti50Cu25Ni20Sn5 during Mechanical Milling

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1769 ◽  
Author(s):  
Dora Janovszky ◽  
Ferenc Kristaly ◽  
Tamas Miko ◽  
Adam Racz ◽  
Maria Sveda ◽  
...  
Keyword(s):  
Particle Size ◽  
Phase Transformation ◽  
Ball Milling ◽  
Milling Time ◽  
Average Particle Size ◽  
Amorphous Powder ◽  
Xrd Analysis ◽  
Milling Process ◽  
Average Particle ◽  
Amorphous Content

Nanocrystalline/amorphous powder was produced by ball milling of Ti50Cu25Ni20Sn5 (at.%) master alloy. Both laser diffraction particle size analyzer and scanning electron microscope (SEM) were used to monitor the changes in the particle size as well as in the shape of particles as a function of milling time. During ball milling, the average particle size decreased with milling time from >320 µm to ~38 µm after 180 min of milling. The deformation-induced hardening and phase transformation caused the hardness value to increase from 506 to 779 HV. X-ray diffraction (XRD) analysis was used to observe the changes in the phases/amorphous content as a function of milling time. The amount of amorphous fraction increased continuously until 120 min milling (36 wt % amorphous content). The interval of crystallite size was between 1 and 10 nm after 180 min of milling with 25 wt % amorphous fractions. Cubic Cu(Ni,Cu)Ti2 structure was transformed into the orthorhombic structure owing to the shear/stress, dislocations, and Cu substitution during the milling process.

Fabrication of Nanosized Alumina Powders by a Simple Polymer Solution Route

2006 ◽  
Vol 6 (11) ◽  
pp. 3633-3636
Author(s):  
Sang-Jin Lee ◽  
Sung-Yong Chun ◽  
Choong-Hyo Lee ◽  
Young-Soo Yoon
Keyword(s):  
Particle Size ◽  
Polymer Solution ◽  
Gas Adsorption ◽  
Average Particle Size ◽  
High Specific Surface Area ◽  
Milling Process ◽  
Degree Of Polymerization ◽  
Average Particle ◽  
Porous Microstructure ◽  
Solution Route

Nanosized alumina (Al2O3) powders had been successfully fabricated by a simple polymer solution route employing polyvinyl alcohol (PVA) as an organic carrier. The fabricated alumina powders had an average particle size of 6.1 nm with a high specific surface area of 99.5 m2/g. As well, the alumina powders were fully crystallized to α phase at a relatively low temperature of 1000 °C. The PVA polymer contributed to a soft and porous microstructure of the calcined alumina powders, and ball-milling process with the porous powders was effective in making nanosized alumina powders. In addition, the content and degree of polymerization of the PVA affected the development of crystallization and powder properties. In this study, the simple polymer technique and milling process for the fabrication of nanosized alumina powders are introduced, and the effects of PVA on the property of the synthesized alumina powders are observed. For the study, the characterizations of the synthesized powders are conducted by using XRD, TEM, particle size analyzer, and nitrogen gas adsorption.

scholarly journals Chemical Synthesis of Silver Nanoparticles Using Tri-sodium Citrate, Stability Study and Their Characterization

2020 ◽  
pp. 37-50
Author(s):  
Prem Santhi Yerragopu ◽  
Sharanagouda Hiregoudar ◽  
Udaykumar Nidoni ◽  
K. T. Ramappa ◽  
A. G. Sreenivas ◽  
...  
Keyword(s):  
Particle Size ◽  
Silver Nanoparticles ◽  
Sodium Citrate ◽  
Structural Characteristics ◽  
Average Particle Size ◽  
Stability Study ◽  
Average Particle ◽  
Ag Nps ◽  
Stirring Time ◽  
Absorbance Peak

The present work was aimed to study the synthesis of silver nanoparticles (Ag NPs) using Tri-Sodium Citrate (TSC), stability study of synthesized Ag NPs and their characterization. Synthesis of Ag NPs has been carried out by maintaining different conditions such as TSC concentration (0.50, 1.00 and 1.50%), AgNO3 concentration (0.50, 1.00 and 1.50 mM) and stirring time (10, 15 and 20 min). The stability study of synthesized Ag NPs conducted for 30 days without adding any stabilizing agents. The characterization of synthesized Ag NPs was carried out for different parameters like particle size and zeta potential using particle size analyzer, absorbance peak by UV-Visible spectrophotometer, morphology by Scanning Electron Microscope (SEM), crystallinity by X-Ray Diffractometer (XRD) and material structural characteristics by Atomic Force Microscope (AFM). The stable chemically synthesized Ag NPs were obtained at C20 (AgNO3 concentration of 1.5 mM, TSC 1.5% and stirring time 20 min) (desirability 99.97%), with average particle size of 22.14 nm and average absorbance peak of 449.85 nm.

scholarly journals Fluidized-Bed Granulation of Probiotics-Encapsulated Spray-Dried Skim Milk Powder: Effects of a Fluidizing Aid, Moisture-Activation and Dehydration

Foods ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1600
Author(s):  
Dong-Hyun Lim ◽  
Andres Letona ◽  
Minjeong Lee ◽  
Dayoung Lim ◽  
Nam-Soo Han ◽  
...  
Keyword(s):  
Particle Size ◽  
Fluidized Bed ◽  
Average Particle Size ◽  
Milk Powder ◽  
Lactobacillus Rhamnosus ◽  
Skim Milk ◽  
Fold Increase ◽  
Skim Milk Powder ◽  
Average Particle ◽  
Spray Dried

A probiotic powder of poor flowability with high dust content, prepared by spray drying reconstituted skim milk fermented with Lactobacillus rhamnosus GG (LGG), was granulated by fluidized-bed granulation (FBG). The effects of the addition of skim milk powder (SMP) as a fluidizing aid, and of simple moisture-activation with or without dehydration, were investigated with respect to the performance of the FBG process. A fine, poorly fluidizable LGG powder (Geldart Group C) could be fluidized and granulated, with a 4- to 5-fold increase in particle size (d4,3 = 96–141 μm), by mixing with SMP (30–50%), which has larger, fluidizable particles belonging to Geldart Group A. Moisture-activation after the mixing, followed by fluidized-bed dehydration with hot air to remove excess moisture, further improved the FBG; the yield of the granules increased from 42% to 61% and the particle size distribution became much narrower, although the average particle size remained almost the same (d4,3 = 142 μm). These granules showed a popcorn-type structure in scanning electron microscopy images and encapsulated a sufficient level of viable LGG cells (1.6 × 108 CFU g−1). These granules also exhibited much better flowability and dispersibility than the spray-dried LGG powder.

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