10 Questions
How do external surfaces differ from atoms in the bulk of a material?
The number of neighbors (coordination) at the surface is less, resulting in unsaturated bonds and surface energy.
What are some examples of meta-stable imperfections in materials?
External surfaces, grain boundaries, twin boundaries, stacking faults, phase boundaries
What are grain boundaries and how are they characterized?
Grain boundaries separate grains in crystalline solids, with a mismatch of orientation on either side. Low angle grain boundaries have slight misalignments (< 10°).
How do materials tend to reduce their energy in relation to external surfaces?
Materials tend to minimize, if possible, the total surface area to reduce surface energy.
What causes the surface energy in materials?
Unsaturated bonds of surface atoms give rise to surface energy.
What is the main characteristic of low angle grain boundaries?
They have slight misalignments on the order of few degrees (< 10°).
How are tilt boundaries different from twist boundaries?
Tilt boundaries are formed by edge dislocations, while twist boundaries are formed by screw dislocations.
Describe the role of grain boundaries in crystalline solids.
Grain boundaries separate grains in crystalline solids and have a mismatch of orientation on either side.
How do external surfaces affect the lattice spacing of materials?
External surfaces can lead to lattice spacing relaxation or crystal structure reconstruction to reduce energy.
What is the significance of the clustering of line defects into a plane in materials?
It gives rise to meta-stable imperfections like external surfaces, grain boundaries, and other surface distortions.
Test your knowledge on Ernest Rutherford's model of the atom, developed in 1911, which proposed a small nucleus with a high positive charge. Explore the key concepts and experiments that led to the advancement of atomic theory.
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