GAS–SOLID EXCHANGE REACTIONS: ZINC VAPOR AND POLYCRYSTALLINE ZINC SULPHIDE

1964 ◽  
Vol 42 (6) ◽  
pp. 1396-1400 ◽  
Author(s):  
E. A. Secco
Keyword(s):  
Zinc Sulphide ◽  
Static System ◽  
Zinc Vapor ◽  
Exchange Reactions ◽  
Polycrystalline Zinc ◽  
Diffusion Controlled ◽  
Fraction Versus ◽  
Exchange Kinetics ◽  
Kinetics Of ◽  
Initial Process

The exchange kinetics of zinc vapor with polycrystalline zinc sulphide, wurtzite structure, have been studied in a static system in the temperature range 720–960 °C.Plots of log10(1−α*), i.e. exchange fraction, versus time reveal two processes. The initial process is a rapid simple exchange, for which the data fit a first-order rate law and which persists to a depth of 15–18 molecular thicknesses. At this depth the second, slower process, which appears to be diffusion-controlled, sets in. Kinetic and structural interpretations of these results along with the existing data on Zn–ZnO exchange are discussed.

Gas–solid exchange reactions: Zinc vapor and polycrystalline zinc selenide

1968 ◽  
Vol 46 (10) ◽  
pp. 1621-1624 ◽  
Author(s):  
E. A. Secco ◽  
Chien-Huo Su
Keyword(s):  
Zinc Selenide ◽  
Static System ◽  
Zinc Vapor ◽  
Exchange Reactions ◽  
Polycrystalline Zinc ◽  
Diffusion Controlled ◽  
Initial Stage ◽  
Exchange Kinetics ◽  
Kinetics Of ◽  
Exchange Data

The exchange kinetics of zinc vapor with polycrystalline zinc selenide have been studied in a static system in the temperature range 720–800 °C.The kinetic data are consistent with a diffusion-controlled process from the initial stage, in contrast with existing exchange data on ZnO and ZnS powders. The diffusion equation is given as:[Formula: see text]

Gas–Solid Exchange Reaction: Zinc Vapor and Polycrystalline Zinc Orthosilicate

1974 ◽  
Vol 52 (23) ◽  
pp. 3932-3935 ◽  
Author(s):  
Etalo A. Secco ◽  
Hari Pada Dhar ◽  
Chien-Huo Su
Keyword(s):  
Initial Rate ◽  
Particle Growth ◽  
Static System ◽  
Zinc Vapor ◽  
Rate Laws ◽  
Zinc Orthosilicate ◽  
Polycrystalline Zinc ◽  
High Annealing ◽  
Exchange Kinetics ◽  
Kinetics Of

The exchange kinetics of zinc vapor with polycrystalline zinc orthosilicate have been studied in a static system in the temperature range 760–1000 °C.The kinetic data reveal two rate laws. The initial rate is assigned to a transport step, i.e. mobility of zinc with D = 10−8 exp (−34 ± 5 kcal/RT ) cm2 s−1. The rate at high annealing times is a composite of the initial rate and a particle growth process, e.g. sintering.

Kinetics of hexagonal–cubic phase transformation of zinc sulfide in vacuo, in zinc vapor, and in sulfur vapor

1968 ◽  
Vol 46 (18) ◽  
pp. 2881-2886 ◽  
Author(s):  
Tamas Bansagi ◽  
E. A. Secco ◽  
O. K. Srivastava ◽  
Ronald R. Martin
Keyword(s):  
Phase Transformation ◽  
Zinc Sulfide ◽  
Solid Phase ◽  
Cubic Phase ◽  
Transformation Rate ◽  
Zinc Vapor ◽  
Sulfur Vapor ◽  
Diffusion Controlled ◽  
Transformation Reaction ◽  
Kinetics Of

The kinetics of the hexagonal–cubic phase transformation of zinc sulfide have been studied in vacuo, in zinc vapor, and in sulfur vapor in the temperature range 800–900 °C by a powder X-ray diffraction technique. The transformation rate is enhanced in the presence of sulfur and zinc vapor. In vacuo and in sulfur vapor the reaction is nucleation-controlled with activation energies of 95.0 and 98.5 ± 5 kcal, respectively. In zinc vapor the reaction is diffusion-controlled with the diffusion coefficient expressed as[Formula: see text]The modes of catalytic action by sulfur and zinc vapor on the solid phase transformation reaction are discussed.

scholarly journals The mercury photosensitized exchange reaction of deuterium and phosphine

1937 ◽  
Vol 160 (902) ◽  
pp. 384-406 ◽  
Keyword(s):  
Physical Properties ◽  
Exchange Reaction ◽  
Experimental Technique ◽  
Periodic System ◽  
Atomic Hydrogen ◽  
Steric Factor ◽  
Simple Problem ◽  
Static System ◽  
Exchange Reactions ◽  
Kinetics Of

In principle, the investigation of exchange reactions of deuterium atoms with hydrides is a simple problem. In practice, however, numerous difficulties arise in the experimental technique, and thus the method chosen for the study of any individual hydride must have regard to its chemical and physical properties. Now that a number of methods exist for investigating such reactions, it becomes of interest to attempt to find how such variables as the energy of activation and steric factor vary among the lower hydrides of the periodic system. The present paper deals with the kinetics of the exchange reactions involving phosphine and trideuterophosphine. A static system was deemed most suitable for the present purpose, the atomic hydrogen being produced photo chemically in the usual way.

Gas-Solid Exchange Reactions: Zinc Vapor and Monocrystalline Zinc Telluride

1971 ◽  
Vol 49 (11) ◽  
pp. 1953-1956 ◽  
Author(s):  
E. A. Secco ◽  
Richard Swee-Chye Yeo
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Process ◽  
Single Crystals ◽  
Zinc Telluride ◽  
Static System ◽  
Rate Data ◽  
Vacancy Mechanism ◽  
Zinc Vapor ◽  
Exchange Reactions ◽  
Radioactive Zinc

The exchange reaction between radioactive zinc vapor and single crystals of zinc telluride was studied in a static system in the temperature range 760–860 °C and PZn = 0.10 atm.The experimental rate data are consistent with a diffusion process which is interpreted in terms of a simple vacancy mechanism. The diffusion coefficient is given by[Formula: see text]

Solvent Effects on Solvent Exchange Reactions at Nickel(II) Centers

1975 ◽  
Vol 53 (5) ◽  
pp. 702-709 ◽  
Author(s):  
Cooper H. Langford ◽  
James P. K. Tong ◽  
André Merbach
Keyword(s):  
Complex Formation ◽  
Linear Relationship ◽  
Solvent Effects ◽  
Solvent Exchange ◽  
Exchange Reactions ◽  
Solvent Dependence ◽  
Leaving Group ◽  
Exchange Kinetics ◽  
Kinetics Of ◽  
Solvent Properties

Several recent correlations relating kinetics of Ni(II) complex formation and solvent exchange to solvent properties are examined after collection of literature and new experiments on solvent exchange kinetics at Ni(II) when onlythesolvent is varied (entering group, leaving group, and nonlabile ligands held constant). The results indicate solvent exchange is remarkably insensitive to bulk solvent. It is suggested that this implies that the interesting correlations of complex formation rates with solvents introduced by Bennetto and Caldin provide a means to study the solvent dependence of the encounter equilibria between a Ni(II) complex and a ligand L. The linear relationship between enthalpies and entropies of activation for reactions at Ni(II) in different media is attributed to the changes in the ligands bound to the Ni(II) center but not undergoing substitution in the reaction observed.

GAS–SOLID EXCHANGE STUDIES BY THE FLOW METHOD: Zn–ZnS AND Zn–ZnO REACTIONS

1964 ◽  
Vol 42 (10) ◽  
pp. 2334-2339
Author(s):  
Allan J. MacKinnon ◽  
Ronald R. Martin ◽  
E. A. Secco
Keyword(s):  
Zinc Oxide ◽  
Exchange Rate ◽  
Zinc Sulphide ◽  
Static Method ◽  
Vapor Flow ◽  
Zinc Vapor ◽  
Flow Rates ◽  
Flow Method ◽  
Polycrystalline Zinc ◽  
Existing Data

The initial exchange of zinc vapor with polycrystalline zinc oxide and zinc sulphide has been studied by a flow method under different conditions of zinc vapor flow rates and temperature. The exchange rate was found to be independent of flow rate. Kinetic and mechanism interpretations of these results along with existing data from exchange studies by the static method are discussed.

scholarly journals Synthesis and Polymerization Kinetics of Rigid Tricyanate Ester

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1686
Author(s):  
Andrey Galukhin ◽  
Roman Nosov ◽  
Ilya Nikolaev ◽  
Elena Melnikova ◽  
Daut Islamov ◽  
...  
Keyword(s):  
Kinetic Analysis ◽  
Single Step ◽  
Polymerization Kinetics ◽  
Scanning Calorimetry ◽  
Modulated Differential Scanning Calorimetry ◽  
Diffusion Controlled ◽  
Polymerization Product ◽  
The One ◽  
Kinetics Of

A new rigid tricyanate ester consisting of seven conjugated aromatic units is synthesized, and its structure is confirmed by X-ray analysis. This ester undergoes thermally stimulated polymerization in a liquid state. Conventional and temperature-modulated differential scanning calorimetry techniques are employed to study the polymerization kinetics. A transition of polymerization from a kinetic- to a diffusion-controlled regime is detected. Kinetic analysis is performed by combining isoconversional and model-based computations. It demonstrates that polymerization in the kinetically controlled regime of the present monomer can be described as a quasi-single-step, auto-catalytic, process. The diffusion contribution is parameterized by the Fournier model. Kinetic analysis is complemented by characterization of thermal properties of the corresponding polymerization product by means of thermogravimetric and thermomechanical analyses. Overall, the obtained experimental results are consistent with our hypothesis about the relation between the rigidity and functionality of the cyanate ester monomer, on the one hand, and its reactivity and glass transition temperature of the corresponding polymer, on the other hand.

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