Mössbauer kinetics of formation of goethite in the basic medium: Effect of the particle size of ferrous hydroxide

1992 ◽  
Vol 69 (1-4) ◽  
pp. 823-826 ◽  
Author(s):  
A. A. Olowe ◽  
J. -M. R. Génin
Keyword(s):  
Particle Size ◽  
Medium Effect ◽  
Basic Medium ◽  
Ferrous Hydroxide ◽  
Kinetics Of Formation ◽  
Kinetics Of

Studies on the formation of Graphite-Ferric Chloride complexes: Kinetics of Formation

1953 ◽  
Vol 6 (3) ◽  
pp. 302 ◽  
Author(s):  
JA Barker ◽  
RC Croft
Keyword(s):  
Particle Size ◽  
Diffusion Coefficients ◽  
Small Difference ◽  
Critical Concentration ◽  
Activation Energies ◽  
Ferric Ions ◽  
Chloride Complexes ◽  
Hexagonal Packing ◽  
Kinetics Of Formation ◽  
Kinetics Of

A study has been made of the kinetics of the diffusion of anhydrous FeC1, in graphite. I t was found that this process can be represented for stages between 50 and 100 per cent. saturation of the graphite and at temperatures in the range 200 to 360 OC by a relation of the type δc/δt = D(δ2c/δr2 + δc/δ/r), providing the diffusion coefficient D is assigned several values for concentrations of occluded FeCl3 above and below a critical concentration. The value of the latter was found to be about two-thirds the saturation concentration of FeCl3 in graphite, this value apparently being the point at which open hexagonal packing of intercalated ferric ions is complete and a closer hexagonal packing commences. Values of the activation energies of occlusion for concentrations above and below two-thirds saturation were found from the relations of corresponding values of diffusion coefficients to temper- ature. The small difference between these activation energies which were of the order of 2 to 3 kcal is attributed to a cancelling of effects, thus the energy necessary to separate carbon lamellae in early stages of occlusion is offset in later stages by hindrance imposed on diffusing molecules by those already occluded. Reduction of particle size of graphite accelerated the occlusion of FeCl3.

Structurization and Properties of Magnetoplastics Made of Mechanically Activated Amorphous-Crystalline Powder Alloys Based on the Nd-Fe-B System

2018 ◽  
Vol 284 ◽  
pp. 455-459
Author(s):  
V.G. Perederiy ◽  
B.G. Gasanov ◽  
A.A. Aganov
Keyword(s):  
Crystal Structure ◽  
Particle Size ◽  
Magnetic Properties ◽  
Melt Spinning ◽  
Crystalline Powder ◽  
Sintered Magnets ◽  
Powder Alloys ◽  
Kinetics Of Formation ◽  
Kinetics Of

The influence of the method of melt spinning on the basis of the Fe-Nd-B system on the amorphous-crystal structure of ribbons and flakes is shown. It is established that the magnetic properties of magnetoplasts depend on the powders particle size, the parameters of mechanic activation during flake milling, the kinetics of formation and growth of Fe2Nd14B phase nuclei at all stages of their preparation and processing, etc. Isotropic and anisotropic magnetoplasts and sintered magnets with magnetic properties: Br = 0.5-1.25 T, HcB = 180-700 kA/m; (BH)max = 50-280 kJ/m3.

Kinetics of cyclization of S-ethoxycarbonylmethylisothiouronium chloride to 2-imino-4-thiazolidone

1979 ◽  
Vol 44 (3) ◽  
pp. 912-917 ◽  
Author(s):  
Vladimír Macháček ◽  
Said A. El-bahai ◽  
Vojeslav Štěrba
Keyword(s):  
Hydrochloric Acid ◽  
Dilute Hydrochloric Acid ◽  
Base Catalysis ◽  
General Base ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Rate Limiting ◽  
Kinetics Of

Kinetics of formation of 2-imino-4-thiazolidone from S-ethoxycarbonylmethylisothiouronium chloride has been studied in aqueous buffers and dilute hydrochloric acid. The reaction is subject to general base catalysis, the β value being 0.65. Its rate limiting step consists in acid-catalyzed splitting off of ethoxide ion from dipolar tetrahedral intermediate. At pH < 2 formation of this intermediate becomes rate-limiting; rate constant of its formation is 2 . 104 s-1.

Cyclization and acid-catalyzed hydrolysis of O-benzoylbenzamidoximes

1986 ◽  
Vol 51 (12) ◽  
pp. 2786-2797
Author(s):  
František Grambal ◽  
Jan Lasovský
Keyword(s):  
Reaction Rate ◽  
Kinetic Isotope ◽  
Acid Base Equilibrium ◽  
Mineral Acids ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Ph Scale ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Derivatives Of

Kinetics of formation of 1,2,4-oxadiazoles from 24 substitution derivatives of O-benzoylbenzamidoxime have been studied in sulphuric acid and aqueous ethanol media. It has been found that this medium requires introduction of the Hammett H0 function instead of the pH scale beginning as low as from 0.1% solutions of mineral acids. Effects of the acid concentration, ionic strength, and temperature on the reaction rate and on the kinetic isotope effect have been followed. From these dependences and from polar effects of substituents it was concluded that along with the cyclization to 1,2,4-oxadiazoles there proceeds hydrolysis to benzamidoxime and benzoic acid. The reaction is thermodynamically controlled by the acid-base equilibrium of the O-benzylated benzamidoximes.

scholarly journals Reduction Mechanism of Fine Hematite Ore Particles in Suspension

2021 ◽  
Author(s):  
Zhiyuan Chen ◽  
Christiaan Zeilstra ◽  
Jan van der Stel ◽  
Jilt Sietsma ◽  
Yongxiang Yang
Keyword(s):  
Particle Size ◽  
Temperature Drop ◽  
Reduction Rate ◽  
Reduction Process ◽  
Reciprocal Relationship ◽  
Drop Tube ◽  
Surface Nucleation ◽  
Order Of Magnitude ◽  
Relationship Of ◽  
Kinetics Of

AbstractIn order to understand the pre-reduction behaviour of fine hematite particles in the HIsarna process, change of morphology, phase and crystallography during the reduction were investigated in the high temperature drop tube furnace. Polycrystalline magnetite shell formed within 200 ms during the reduction. The grain size of the magnetite is in the order of magnitude of 10 µm. Lath magnetite was observed in the partly reduced samples. The grain boundary of magnetite was reduced to molten FeO firstly, and then the particle turned to be a droplet. The Johnson-Mehl-Avrami-Kolmogorov model is proposed to describe the kinetics of the reduction process. Both bulk and surface nucleation occurred during the reduction, which leads to the effect of size on the reduction rate in the nucleation and growth process. As a result, the reduction rate constant of hematite particles increases with the increasing particle size until 85 µm. It then decreases with a reciprocal relationship of the particle size above 85 µm.

Effect of CTABr (surfactant) on the kinetics of formation of silver nanoparticles by Amla extract

2021 ◽  
Vol 329 ◽  
pp. 115537
Author(s):  
Nazia Iqbal ◽  
S.M. Shakeel Iqubal ◽  
Aejaz Abdullatif Khan ◽  
Tasneem Mohammed ◽  
Ali Mohamed Alshabi ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Kinetics Of Formation ◽  
Kinetics Of

Kinetics of formation and dissociation of triaza-crown-alkanoic acid complexes of cerium(III) and europium(III)

Polyhedron ◽  
1995 ◽  
Vol 14 (10) ◽  
pp. 1299-1306 ◽  
Author(s):  
Ki-Young Choi ◽  
Dong Won Kim ◽  
Choon Pyo Hong
Keyword(s):  
Alkanoic Acid ◽  
Kinetics Of Formation ◽  
Kinetics Of

The kinetics of formation of resveratrol-β-cyclodextrin-NH2 and resveratrol analog-β-cyclodextrin-NH2 supramolecular complexes

2021 ◽  
pp. 130612
Author(s):  
Eliara Acipreste Hudson ◽  
Hauster Maximiler Campos de Paula ◽  
Yara Luiza Coelho ◽  
Nícolas Glanzmann ◽  
Adilson David da Silva ◽  
...  
Keyword(s):  
Supramolecular Complexes ◽  
Kinetics Of Formation ◽  
Kinetics Of
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