Steric and repeated-collision effects in diffusion-controlled reactions in solution: kinetics of formation of some iodine donor–acceptor complexes of sulphur compounds

1990 ◽  
Vol 86 (9) ◽  
pp. 1549-1554 ◽  
Author(s):  
Edward F. Caldin ◽  
L. de Forest ◽  
Alan Queen
Keyword(s):  
Sulphur Compounds ◽  
Diffusion Controlled ◽  
Kinetics Of Formation ◽  
Donor Acceptor ◽  
Kinetics Of ◽  
Solution Kinetics

The kinetics of formation of electron donor–acceptor complexes. A temperature-jump study

1990 ◽  
Vol 68 (2) ◽  
pp. 278-281 ◽  
Author(s):  
M. A. Zon ◽  
H. Fernandez ◽  
L. Sereno ◽  
J. J. Silber
Keyword(s):  
Electron Donor ◽  
Rate Constants ◽  
Temperature Jump ◽  
Diffusion Control ◽  
Diffusion Controlled ◽  
Kinetics Of Formation ◽  
Donor Acceptor ◽  
Eda Complex ◽  
Kinetics Of

The kinetics of the Electron Donor–Acceptor (EDA) complex between N,N,N′,N′-tetramethyl-p-phenylenediamine and m-dinitrobenzene in acetonitrile has been studied by the temperature-jump technique. The magnitude of the rate constants of association and dissociation, although relatively large, is well below the diffusion control values. The calculated rates closely coincide with those obtained by chronoamperometry. An entropy control is suggested for this reaction. The results obtained in this work are useful to demonstrate that the concept about EDA complexes being formed by diffusion-controlled reactions should not be generalized. Keywords: electron donor–acceptor complexes, m-dinitrobenzene, N,N,N′,N′-tetramethyl-p-phenylenediamine, T-jump, kinetics.

scholarly journals Study on indium leaching from mechanically activated hard zinc residue

2011 ◽  
Vol 47 (1) ◽  
pp. 63-72 ◽  
Author(s):  
J.H. Yao ◽  
X.H. Li ◽  
Y.W. Li
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Planetary Mill ◽  
Leaching Rate ◽  
Obvious Effect ◽  
Diffusion Controlled ◽  
Leaching Reaction ◽  
Kinetics Of ◽  
Positive Effect ◽  
Solution Kinetics

In this study, changes in physicochemical properties and leachability of indium from mechanically activated hard zinc residue by planetary mill were investigated. The results showed that mechanical activation increased specific surface area, reaction activity of hard zinc residue, and decreased its particle size, which had a positive effect on indium extraction from hard zinc residue in hydrochloric acid solution. Kinetics of indium leaching from unmilled and activated hard zinc residue were also investigated, respectively. It was found that temperature had an obvious effect on indium leaching rate. Two different kinetic models corresponding to reactions which are diffusion controlled, [1-(1- x)1/3]2=kt and (1-2x/3)-(1-x)2/3=kt were used to describe the kinetics of indium leaching from unmilled sample and activated sample, respectively. Their activation energies were determined to be 17.89 kJ/mol (umilled) and 11.65 kJ/mol (activated) within the temperature range of 30?C to 90?C, which is characteristic for a diffusion controlled process. The values of activation energy demonstrated that the leaching reaction of indium became less sensitive to temperature after hard zinc residue mechanically activated by planetary mill.

COMPARATIVE STUDY ON THE ADSORPTION PROCESSES OF ALKANETHIOL AND ALKANEDITHIOL ON GOLD

2010 ◽  
Vol 17 (04) ◽  
pp. 397-403 ◽  
Author(s):  
HUI HE ◽  
YAN GUO ◽  
SHOUFU WANG ◽  
YAQING JIANG
Keyword(s):  
Self Assembly ◽  
Surface Coverage ◽  
Self Assembled Monolayers ◽  
Diffusion Controlled ◽  
Assembled Monolayers ◽  
Adsorption Processes ◽  
Kinetics Of Formation ◽  
Initial Adsorption ◽  
Adsorption Rates ◽  
Kinetics Of

The kinetics of formation of self-assembled monolayers on gold generated by the adsorption of 1-octanethiol and 1,8-octanedithiol were explored by electrochemistry measurement. The time dependence of capacitance and surface coverage supported that the adsorption of thiols typically processed with a two-step adsorption consisted of a fast initial adsorption and a slowly following reorganization. From the function of surface coverage versus time, one could get rate constants of adsorption of thiols, and the adsorption process was demonstrated to follow a diffusion-controlled Langmuir model. A comparison of the adsorption rates for different concentration between 1-octanethiol and 1,8-octanedithiol revealed that their adsorption processes were almost identical and independent on the concentration, inferring that only one sulfur atom contributed to the self-assembly of dithiol molecule.

Formation kinetics of nanocrystalline Fe–4 wt.% Al solid solution during ball milling

1997 ◽  
Vol 12 (6) ◽  
pp. 1429-1432 ◽  
Author(s):  
H. G. Jiang ◽  
R. J. Perez ◽  
M. L. Lau ◽  
E. J. Lavernia
Keyword(s):  
Solid Solution ◽  
Ball Milling ◽  
Structural Evolution ◽  
Milling Process ◽  
Avrami Equation ◽  
Scanning Calorimetry ◽  
Diffusion Controlled ◽  
Interphase Boundaries ◽  
Kinetics Of Formation ◽  
Kinetics Of

Formation of nanocrystalline Fe–4 wt.% Al solid solution has been achieved through SPEX ball milling of blended elemental Fe and Al powders. Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) have been employed to follow the structural evolution during the ball-milling process. Exothermic peaks exhibited in DSC diagrams of the powders milled for 10 to 60 min yielded thermal enthalpies corresponding to the formation of Fe–4 wt.% Al solid solution, from which the kinetics of formation were found to follow the Johnson–Mehl–Avrami equation. Assessment of the kinetic parameter n reveals a diffusion controlled mechanism, in which grain and interphase boundaries may play a crucial role, during the solid solution formation of Fe–4 wt.% Al.

Kinetics of formation of sodium chlorozirconate

1967 ◽  
Vol 45 (20) ◽  
pp. 2317-2320 ◽  
Author(s):  
J. D. Dutrizac ◽  
S. N. Flengas
Keyword(s):  
Rate Constant ◽  
Parabolic Rate Constant ◽  
Zirconium Tetrachloride ◽  
Formation Reaction ◽  
Diffusion Controlled ◽  
Kinetics Of Formation ◽  
Torr Pressure ◽  
Arrhenius Rate Equation ◽  
Kinetics Of ◽  
Method Analysis

The kinetics of formation of sodium hexachlorozirconate from sodium chloride single crystals and zirconium tetrachloride vapor at about 600 Torr have been investigated by the weight-gain method. Analysis of the results showed the formation reaction to be diffusion controlled, with zirconium tetrachloride being the most probable diffusing species. The apparent energy of activation has been determined for this reaction from the variation of the rate constant with temperature, and it was found to be 12.3 ± 3 kcal/mole. The Arrhenius rate equation for the formation of Na2ZrCl6 from NaCl and ZrCl4 at 600 Torr pressure, in the temperature range 400 to 500 °C, is [Formula: see text]where the units of the parabolic rate constant, K, are (g(Na2ZrCl6))2 cm−4 h−1.

scholarly journals Effect of thermal aging on the interfacial reactions of tin-based solder alloys and copper substrates and kinetics of formation and growth of intermetallic compounds

2011 ◽  
Vol 16 (1) ◽  
pp. 86-95 ◽  
Author(s):  
J. C. Madeni ◽  
S. Liu
Keyword(s):  
Intermetallic Compounds ◽  
Thermal Aging ◽  
Intermetallic Layer ◽  
Solder Matrix ◽  
Solder Alloys ◽  
Intermetallic Growth ◽  
Diffusion Controlled ◽  
Kinetics Of Formation ◽  
Morphological Differences ◽  
Kinetics Of

The formation and growth of intermetallic compounds at the interface between four solder alloys, Sn-3.5Ag, Sn-0.7Cu, Sn-3.2Ag0.8Cu and Sn-9Zn, and Cu-plated substrates have been studied. Thermal aging tests for 20, 100, 200, 500 hours at 70, 100 and 150 ºC were carried out. As expected, results indicate that the formation of the intermetallic layer is a diffusion-controlled process. Nevertheless, migration and dissolution of Cu into the solder was observed, especially at lower temperatures. The thickness of the layer of intermetallic compound increased with increasing aging temperature and time. The Sn-3.5Ag alloy showed the smallest intermetallic growth and the Sn-9Zn alloy the highest, compared to the other alloys. The results also show definite morphological differences between the Cu/Cu3Sn, the Cu3Sn/Cu6Sn5 and the Cu6Sn5/solder-matrix interfaces.

Kinetics of formation of silicides: A review

1986 ◽  
Vol 1 (1) ◽  
pp. 205-221 ◽  
Author(s):  
F. M. d'Heurle ◽  
P. Gas
Keyword(s):  
Phase Formation ◽  
Reaction Rate ◽  
Diffusion Control ◽  
Specific Effects ◽  
Diffusion Controlled ◽  
Kinetics Of Formation ◽  
Amorphous Compounds ◽  
Silicide Growth ◽  
Rate Controlled ◽  
Kinetics Of

The kinetics of silicide growth are classified into three different categories: (a) diffusion controlled, (b) nucleation controlled, (c) others (reaction rate controlled). These are analyzed with the aim of understanding both the phenomenology of growth and the specific atomic mechanisms of phase formation. Diffusion-controlled growth is discussed with respect to the Nernst-Einstein equation. Stress relaxation is considered as a possible cause of reaction-rate control. The relative merits of two different types of marker experiments are compared. A few silicides are discussed in terms of what can be inferred about diffusion mechanisms. The competition between reaction-rate and diffusion control phenomena is shown to have specific effects on the sequence of phase formation; it is also related to the formation of some amorphous compounds. Reactions between silicon and alloyed metal films are used to illustrate the respective influences of mobility and driving force factors on the kinetics of silicide growth; they can also be used to underline the dominance of nucleation over diffusion in some silicide formation processes.

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.

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