Why with increase in temperature Grain size increases in MgWo4 sample ?
The answer relies on the surface versus bulk Gibbs free energy contribution to the global Gibbs free energy how dependence upon the surface area to volume ratio of the poly- crystalline materials. That amounts to the continuous mass transfer from the small grains to the large grains through the bulk and surface diffusion, which are strongly dependent upon the temperature. The higher the temperature higher would be the rate of diffusion-Exponential dependence_ Actually at the stationary state the whole polycrystalline sample turns out to be a single crystal having spheroidal in shape if the material would be isotropic.
This problem can be treated rigorously by using the irreversible thermodynamics of surfaces and interfaces including the embedding bulk phase, according to the theory and numerical implementation set by Ogurtani and his coworkers as a special case.
you can check wikipedia link:
https://en.wikipedia.org/wiki/Grain_growth
Dear Sonali Biswas
Have a nice day and good times
Yes, the grain size increases with increasing the annealing temperature. This is because increasing the temp. leads to increase the crystallinity of the material and hence increases the number of crystallites. As a result, this leads to increase the agglomeration of these crystallites which consist the grain size. So, this increase the grain size.
l hope this help you.
Good luck
The answer relies on the surface versus bulk Gibbs free energy contribution to the global Gibbs free energy how dependence upon the surface area to volume ratio of the poly- crystalline materials. That amounts to the continuous mass transfer from the small grains to the large grains through the bulk and surface diffusion, which are strongly dependent upon the temperature. The higher the temperature higher would be the rate of diffusion-Exponential dependence_ Actually at the stationary state the whole polycrystalline sample turns out to be a single crystal having spheroidal in shape if the material would be isotropic.
This problem can be treated rigorously by using the irreversible thermodynamics of surfaces and interfaces including the embedding bulk phase, according to the theory and numerical implementation set by Ogurtani and his coworkers as a special case.
Dear colleagues
To the down voter,
Please give your explanations to the reasons of why did you vote against our replies of the given question? give your objections.
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Dear Ahmed, SORRY! even ı didn't evaluate your answer by giving you any mark but you haven't presented any plausible scientific answer, which may be acceptable by any person who have had few courses from the physical metallurgy enforced by one quarter course from the metallurgical thermodynamics.
What happens if the grain boundary interfacial Gibbs free energy would be a negative quantity, which is the case for the type II-superconductors, where the formation of the flux line cell structure occurs by the fragmentation of the few large domains that preexist before the whole body enters into the super conducting state.
@Ahmed Saeed Hassanien
As I see, in your post you said
"leads to increase the crystallinity of the material and hence increases the number of crystallites. As a result, this leads to increase the agglomeration of these crystallites which consist the grain size".
It's just a nonsense.
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