Grain Size of Ceramics: Why Larger is Smaller for Diffusivity

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SUMMARY

The discussion centers on the relationship between grain size and diffusivity in ceramics, specifically noting that larger grain sizes result in reduced grain-boundary contributions to diffusivity. This occurs because larger grains have fewer grain boundaries and less grain boundary surface area. The linear intercept method is identified as a key technique for measuring grain size in polycrystalline materials, correlating the number of intercepted grain boundaries with mean grain size. Additionally, it is established that grain boundaries possess higher entropy due to the presence of a mixture of different types of atoms.

PREREQUISITES
  • Understanding of grain boundary phenomena in materials science
  • Familiarity with polycrystalline materials
  • Knowledge of the linear intercept method for grain size measurement
  • Basic concepts of entropy in materials
NEXT STEPS
  • Research the linear intercept method for grain size determination in detail
  • Explore the impact of grain boundary characteristics on material properties
  • Study the relationship between entropy and grain boundaries in ceramics
  • Investigate methods to manipulate grain size for improved diffusivity
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Materials scientists, ceramic engineers, and researchers focused on the properties of polycrystalline materials and their diffusivity characteristics.

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Why is it that the larger the grain size, the smaller the grain-boundary contribution to diffusivity?
 
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The larger the grain size, the less grain boundaries and the less grain boundary surface area.

One method of determining grain size in polycrystalline materials is the linear intercept method. On can draw a straight line and determine how many grain boundaries are intercepted. This has been correlated with a mean grain size.
 
The grain-boundary has higher entropy, because it has a mixture of different type of atoms, is that correct?
 

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