Kinetics of transformation with nucleation and growth mechanism: Diffusion-controlled reactions

1997 ◽  
Vol 82 (9) ◽  
pp. 4270-4276 ◽  
Author(s):  
Ge Yu ◽  
Y. K. L. Lai ◽  
W. Zhang
Keyword(s):  
Growth Mechanism ◽  
Nucleation And Growth ◽  
Diffusion Controlled ◽  
Kinetics Of ◽  
Nucleation And Growth Mechanism

Evaluation of Foaming and Nucleation and Growth Mechanism of Soy-Based Polyurethane Foams

2018 ◽  
Vol 913 ◽  
pp. 738-745 ◽  
Author(s):  
Xiao Zhang ◽  
Xin Xing Zhou
Keyword(s):  
Growth Mechanism ◽  
Nucleation And Growth ◽  
Polyurethane Foams ◽  
Molar Ratio ◽  
Foam Formation ◽  
Isocyanate Index ◽  
Diffusion Controlled ◽  
Key Factor ◽  
Polyether Polyol ◽  
Nucleation And Growth Mechanism

The foaming and nucleation and growth mechanism of soybean oil-based polyurethane (SPU) were determined by the degree of hydrogen bonding, and isocyanate groups. New types of SPU were prepared by the different NCO/OH molar ratio (isocyanate index) from 1.0 to 2.0 in a soy polyol/polyether polyol (MDI) system. Foaming and nucleation and growth mechanisms of SPU were studied by fluorescence microscope (FM), scanning electron microscope (SEM), energy disperse spectroscopy (EDS) and Fourier transform infrared spectroscopy (FT-IR). It indicated that the isocyanate index affected remarkably the velocity of foaming and the critical nucleation radius of SPU and the ester functional group increased with the increase of isocyanate index. The nucleation and growth phase transition were dominated by the diffusion controlled nucleation and isocyanate content was the key factor of foam formation.

Derivation of the Kinetics of Phase Transformations with Nucleation and Growth Mechanism

1997 ◽  
Vol 481 ◽  
Author(s):  
G. Yu ◽  
S. T. Lee ◽  
J. K. L. Lai
Keyword(s):  
Size Distribution ◽  
Growth Mechanism ◽  
Survival Probability ◽  
Microstructural Analysis ◽  
Nucleation And Growth ◽  
Distribution Functions ◽  
Model Systems ◽  
Individual Site ◽  
Kinetics Of ◽  
Nucleation And Growth Mechanism

ABSTRACTThe kinetics of phase transformation which follows a nucleation-and-growth mechanism was studied by using probability theory. From the calculation of the survival probability for each individual site, the general equation for describing the transformation kinetics, in which the nucleation and growth rates are considered as a function of time and space, is derived. In comparison to the classical derivation by Avrami, the new derivation is logical and transparent. The extension of the treatment by using the definition of the multiple-survival probability leads to the exact solutions of the time dependent grain size distribution functions during transformation. A new understanding of fundamental relationships for the microstructural analysis can be achieved by comparing different kinds of size distribution functions. By applying the principles of the analytical treatment to the simulation, model systems of vast size can be handled for very complicated transformation process.

Kinetics of the SRO-LRO Transformation in NI4MO

1984 ◽  
Vol 39 ◽  
Author(s):  
E. E. Stansbury
Keyword(s):  
Temperature Dependence ◽  
Experimental Evidence ◽  
Growth Mechanism ◽  
Strong Evidence ◽  
Nucleation And Growth ◽  
Initial State ◽  
Theoretical Predictions ◽  
Microdomain Structure ◽  
Kinetics Of ◽  
Nucleation And Growth Mechanism

ABSTRACTThe isothermal time-temperature dependence of the transformation from SRO to LRO as measured by resistivity changes is given. Problems of defining an initial state from which the transformation occurs are reviewed with emphasis on the microdomain structure from which the LRO structure develops. Questions of homogeneous transformation relative to heterogeneous transformation by clear nucleation and growth are addressed in terms of experimental evidence and theoretical predictions. Strong evidence for a nucleation and growth mechanism, at least above 750° C, is presented.

Formation of coherent twins in YBa2Cu3O7–δ superconductors

1989 ◽  
Vol 4 (4) ◽  
pp. 795-801 ◽  
Author(s):  
C. J. Jou ◽  
J. Washburn
Keyword(s):  
Oxygen Uptake ◽  
Growth Mechanism ◽  
Oxygen Uptake Rate ◽  
Nucleation And Growth ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Transmission Electron Microscopic ◽  
Twin Formation ◽  
Boundary Model ◽  
Nucleation And Growth Mechanism

A nucleation-and-growth mechanism for the twin formation in YBa2Cu3O7–δ superconductors based on the oxygen uptake rate curve and published transmission electron microscopic observations is proposed together with an oxygen-depleted twin boundary model. The difficulty of reaching stoichiometric YBa2Cu3O7 is explained.

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