How does the number of vacancies depend on temperature?
The equilibrium concentration of vacancies increases with temperature.
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What are the two types of solid solutions?
Substitutional and interstitial solid solutions.
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What are the three types of dislocations?
Edge dislocations, screw dislocations, and mixed dislocations.
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What is the significance of defects in crystalline materials?
Defects are disruptions in the crystalline order that can lower energy and stabilize materials, and can be either desirable or undesirable.
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What is solidification in the context of casting molten material?
The process of nuclei forming solid phases which grow into grains.
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What governs the formation of substitutional solid solutions?
The Hume-Rothery rules include atomic radius similarity, proximity in the periodic table, same crystal structure, and valences.
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What is the role of grain refiners in material processing?
Grain refiners are added to produce smaller, more uniform equiaxed grains.
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What are point defects in metals?
Vacancies, self-interstitials, and substitutional impurity atoms.
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What is a key characteristic of dislocations?
Dislocations result in permanent (plastic) deformation when stresses are applied.
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What are the effects of grain boundaries in materials?
They are regions of atomic misalignment that increase atomic mobility and chemical reactivity.
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What is Boltzmann's constant?
It is a physical constant that relates the average kinetic energy of particles in a gas to the temperature of the gas.
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How can vacancies be computed in a material?
Using the Arrhenius equation: Nv/N = exp(-Qv/kT) where Nv is the number of vacancies, N is the total number of lattice sites, Qv is the activation energy, k is Boltzmann's constant, and T is the temperature.
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What are the characteristics of edge dislocations?
Edge dislocations are formed by an extra half-plane of atoms inserted in a crystal, causing misalignment of atomic planes.
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What is the difference between a solid solution and a new phase in alloys?
A solid solution consists of a homogeneous distribution of elements without altering the crystal structure, while a new phase indicates a different composition and structure.
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What is the effect of temperature on vacancy concentration?
As temperature increases, the concentration of vacancies in a material increases.
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What is Scanning Tunneling Microscopy (STM)?
A technique used to image surfaces at the atomic level by scanning a sharp tip over the surface and measuring the tunneling current.
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