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28 Cards in this Set
- Front
- Back
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N sub(v)
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equilibrium number of vacancies for a given quantity of material
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N
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total number of atomic sites
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Q sub(v)
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the energy required for the formation of a vacancy
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k
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Boltzmann's constant = 1.38*10^-23 J/(atom*K)
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For most metals, how many vacancies are there just below melting point?
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on the order of 10^-4
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self interstitial
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an atom from the crystal that is crowded into an interstitial site (not highly probable)
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what three types of point defects are likely to occur in ceramics?
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anion vacancy, cation vacancy, cation interstitial
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define Electroneutrality
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the state that exists when there are equal numbers of positive and negative charges from the ions
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defect structures
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types and concentrations of atomic defects in ceramics
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Frenkel defect
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a cation-vacancy and cation-interstitial pair
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Schottky defect
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cation vacancy-anion vacancy pair
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stoichiometry
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a state for ionic compounds wherein there is the exact ratio of cations to anions as predicted by the chemical formula
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alloy
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a metal in which impurity atoms have been added intentionally to impart specific characteristics to the material
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at 99.9999% purity, how many impurity atoms will be present in one cubic meter of material?
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on the order of 10^22 to 10^23
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solvent of a solid solution
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the host atoms
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the solute of a solid solution
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the foreign atoms (lesser concentration)
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solid solution
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forms when the crystal structure of the host atoms is maintained when solute atoms are added and no new structures are formed
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Is a solid solution compositionally homogeneous?
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yes
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what are the four factors that determine the degree of solubility?
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atomic size factor, crystal structure, electronegativity, and valences
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what are the two types of impurity point defects found in solid solutions?
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substitutional and interstitial
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what is the max radius difference solute atoms may have and still be soluble?
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15%
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below what radius difference is complete solubility seen?
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8%
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what is the probability of having two vacancies next to each other?
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like flipping a coin the same way twice in a row...
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diffusion
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the phenomenon of material transport by atomic motion
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what are the two main diffusion mechanisms?
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*vacancy diffusion
*interstitial diffusion |
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what are 3 other diffusion pathways?
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grain boundaries, dislocations, and surface
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the process whereby the atoms of one metal diffuse into another
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interdiffusion, or impurity diffusion
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diffusion in pure metals
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self-diffusion
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