Mechanism and kinetics of sintering highly porous fibrous structures

1988 ◽  
Vol 27 (4) ◽  
pp. 284-289
Author(s):  
Ya. E. Geguzin ◽  
Yu. I. Klinchuk
Keyword(s):  
Mechanism And Kinetics ◽  
Kinetics Of ◽  
Highly Porous

scholarly journals Mechanism and Kinetics of Malachite Dissolution in an NH4OH System

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 833
Author(s):  
Alvaro Aracena ◽  
Javiera Pino ◽  
Oscar Jerez
Keyword(s):  
Ammonium Hydroxide ◽  
Copper Recovery ◽  
X Ray Diffraction ◽  
Solution Ph ◽  
Acid Dissolution ◽  
Acid Consumption ◽  
Mechanism And Kinetics ◽  
Solid Liquid ◽  
Kinetics Of ◽  
Highly Porous

Copper oxide minerals composed of carbonates consume high quantities of leaching reagent. The present research proposes an alternative procedure for malachite leaching (Cu2CO3(OH)2) through the use of only compound, ammonium hydroxide (NH4OH). Preliminary studies were also carried out for the dissolution of malachite in an acid system. The variables evaluated were solution pH, stirring rate, temperature, NH4OH concentration, particle size, solid/liquid ratio and different ammonium reagents. The experiments were carried out in a stirred batch system with controlled temperatures and stirring rates. For the acid dissolution system, sulfuric acid consumption reached excessive values (986 kg H2SO4/ton of malachite), invalidating the dissolution in these common systems. On the other hand, for the ammoniacal system, there was no acid consumption and the results show that copper recovery was very high, reaching values of 84.1% for a concentration of 0.2 mol/dm3 of NH4OH and an experiment time of 7200 s. The theoretical/thermodynamic calculations indicate that the solution pH was a significant factor in maintaining the copper soluble as Cu(NH3)42+. This was validated by the experimental results and solid analysis by X-ray diffraction (XRD), from which the reaction mechanisms were obtained. A heterogeneous kinetic model was obtained from the diffusion model in a porous layer for particles that begin the reaction as nonporous but which become porous during the reaction as the original solid splits and cracks to form a highly porous structure. The reaction order for the NH4OH concentration was 3.2 and was inversely proportional to the square of the initial radius of the particle. The activation energy was calculated at 36.1 kJ/mol in the temperature range of 278 to 313 K.

Oil extraction from the sunflower seeds, mechanism and kinetics of the process

2020 ◽  
Vol 3 (1) ◽  
pp. 155-160
Author(s):  
Ye. M. Semenyshyn ◽  
◽  
V. M. Atamanyuk ◽  
O. Ya. Dobrovetska ◽  
T. I. Rymar ◽  
...  
Keyword(s):  
Oil Extraction ◽  
Sunflower Seeds ◽  
Mechanism And Kinetics ◽  
Kinetics Of

Studies on the Behavior Some Paints in Electro-insulating Fluid Based on Vegetable Esters

2018 ◽  
Vol 69 (5) ◽  
pp. 1139-1144
Author(s):  
Iosif Lingvay ◽  
Adriana Mariana Bors ◽  
Livia Carmen Ungureanu ◽  
Valerica Stanoi ◽  
Traian Rus
Keyword(s):  
Structural Changes ◽  
Oxidation Processes ◽  
High Oleic ◽  
Painting Materials ◽  
Insulating Paper ◽  
Different Types ◽  
Mechanism And Kinetics ◽  
Kinetics Of ◽  
Natural Ester

For the purpose of using three different types of painting materials for the inner protection of the transformer vats, their behavior was studied under actual conditions of operation in the transformer (thermal stress in electro-insulating fluid based on the natural ester in contact with copper for electro-technical use and electro-insulating paper). By comparing determination of the content in furans products (HPLC technique) and gases formed (by gas-chromatography) in the electro-insulating fluid (natural ester with high oleic content) thermally aged at 130 �C to 1000 hours in closed glass vessels, it have been found that the presence the investigated painting materials lead to a change in the mechanism and kinetics of the thermo-oxidation processes. These changes are supported by oxygen dissolved in oil, what leads to decrease both to gases formation CO2, CO, H2, CH4, C2H4 and C2H6) and furans products (5-HMF, 2-FOL, 2 -FAL and 2-ACF). The painting materials investigated during the heat treatment applied did not suffer any remarkable structural changes affecting their functionality in the electro-insulating fluid based on vegetable esters.

Mechanism and Kinetics of the Hydrogen Failure of Thermoelectric Materials during Water Electrolysis

2020 ◽  
Vol 2020 (10) ◽  
pp. 1102-1115
Author(s):  
M. A. Korzhuev ◽  
I. V. Katin ◽  
M. A. Kretova ◽  
E. S. Avilov
Keyword(s):  
Thermoelectric Materials ◽  
Water Electrolysis ◽  
Mechanism And Kinetics ◽  
Kinetics Of

Spectrocoulometry – a new spectro-electrochemical technique

1987 ◽  
Vol 52 (6) ◽  
pp. 1386-1396 ◽  
Author(s):  
Ján Mocák ◽  
Michal Németh ◽  
Mieczyslaw Lapkowski ◽  
Jerzy W. Strojek
Keyword(s):  
Optical Probe ◽  
Optical Signal ◽  
Open Circuit ◽  
Electrochemical Technique ◽  
Kinetics Of Oxidation ◽  
Hydrolytic Reaction ◽  
Experimental Errors ◽  
Mechanism And Kinetics ◽  
Kinetics Of

A spectrocoulometric macrocell with a direct-view optical probe was designed and constructed, where the optical signal is transferred by light-conducting glass or quartz fibres permitting to work at wavelengths above 410 or 300 nm. The method of measurement on the proposed equipment is described; it was tested in the study of the mechanism and kinetics of oxidation of Fe(bipy)32+ ions (bipy = 2,2'-bipyridyl) with the use of potentiostatic coulometric electrolysis with open-circuit relaxation at a suitable time. The primary product of electrolysis, Fe(bipy)33+, undergoes a follow-up hydrolytic reaction with the formation of a binuclear complex. The rate constant of the reaction of the first order involves the contributions, kBi, from all bases present in solution; the corresponding values for H2O, OH-, bipy, and CH3COO- ions at a ionic strength 0·5 mol dm-3 and 25 °C were determined as kOH = (5·0 ± 0·6) . 105 mol-1 dm3 s-1, kbipy = (1·3 ± 0·2) . 10-1 mol-1 dm3 s-1, kAc = (5·8 ± 1·0) . 10-2 mol-1 dm3 s-1, and kH2O is not significant with respect to experimental errors.

New highly efficient coulometric cell with homogenous potential distribution on the working electrode

1986 ◽  
Vol 51 (3) ◽  
pp. 636-642
Author(s):  
Michal Németh ◽  
Ján Mocák
Keyword(s):  
Chemical Reactions ◽  
Potential Distribution ◽  
Anaerobic Conditions ◽  
Highly Efficient ◽  
Working Electrode ◽  
Constant Potential ◽  
Quantitative Analyses ◽  
Mechanism And Kinetics ◽  
Kinetics Of

A highly efficient coulometric cell was designed and constructed, ensuring a constant potential over the whole surface of the working electrode and suitable for very rapid electrolysis. It consists of concentric cylindrical Teflon parts; also the working and auxiliary electrodes are cylindrical and concentric. Electrolysis can be carried out under anaerobic conditions. Functioning of the cell was tested on the oxidation of hexacyanoferrate(II) and chlorpromazine and reduction of hexacyanoferrate(III). The new cell is suitable for routine quantitative analyses and in studying the mechanism and kinetics of moderately rapid chemical reactions.

scholarly journals Unraveling the Mechanism and Kinetics of Binding of an LCI‐eGFP‐Polymer for Antifouling Coatings

2021 ◽  
pp. 2100158
Author(s):  
Dominik Söder ◽  
Manuela Garay‐Sarmiento ◽  
Khosrow Rahimi ◽  
Fabian Obstals ◽  
Sarah Dedisch ◽  
...  
Keyword(s):  
Antifouling Coatings ◽  
Mechanism And Kinetics ◽  
Kinetics Of
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