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Questions and Answers
What is the mechanism of vacancy diffusion?
What is the mechanism of vacancy diffusion?
- An atom moves into an interstitial position, creating a new interstitial position
- An atom moves into the vacancy’s original position, creating a new vacancy in the atom’s original position (correct)
- An atom moves into the vacancy’s original position, creating a new interstitial position
- An atom moves into an interstitial position, creating a new vacancy in the atom’s original position
How does interstitial diffusion occur?
How does interstitial diffusion occur?
- Larger chemical species move between the spaces around smaller atoms
- Atoms move into the vacancies of other atoms
- Smaller chemical species move between the spaces around larger atoms (correct)
- Atoms move into the interstitial positions of other atoms
What does Fick’s First Law describe?
What does Fick’s First Law describe?
- The relationship between temperature and diffusion coefficient
- The mechanism of interstitial diffusion
- The change in concentration gradient over time
- How much of something moved and how fast did it move (correct)
What does steady-state diffusion imply?
What does steady-state diffusion imply?
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How does temperature affect diffusion?
How does temperature affect diffusion?
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Study Notes
Mechanism of Diffusion
- Vacancy diffusion: Occurs when an atom jumps into an adjacent vacant lattice site, resulting in a net movement of atoms.
- Interstitial diffusion: Takes place when an atom moves into an interstitial site, which is a space between lattice sites, without displacing any other atoms.
Fick's Laws
- Fick's First Law: Describes the rate of diffusion in a concentration gradient, stating that the flux of atoms is proportional to the concentration gradient and the diffusion coefficient.
- Fick's Second Law: Describes the change in concentration over time, stating that the rate of change of concentration is proportional to the second derivative of concentration with respect to position.
Characteristics of Diffusion
- Steady-state diffusion: Implies that the concentration gradient remains constant over time, resulting in a constant flux of atoms.
- Temperature effect: Diffusion rate increases with increasing temperature, as higher temperatures provide more energy for atoms to overcome their activation energy and diffuse.
Important Concepts
- Diffusion coefficient: A measure of the ease of diffusion, dependent on the material's properties and temperature.
- Concentration gradient: The change in concentration of atoms or molecules over a given distance.
- Flux: The rate of flow of atoms or molecules across a given area.
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Description
Prepare for the final exam in Mechanical Engineering with this review quiz covering topics such as vacancy diffusion, interstitial diffusion, and more. Test your understanding of materials science and engineering concepts.
