Crystalline Structure

Question 1

What is the difference between crystalline and amorphous materials?

Answer 1

A crystalline material has long-range order while an amorphous material does not.

Question 2

What are the three main types of Bravais lattice in metals?

Answer 2

Body centred cubic, Face centred cubic and Hexagonal close-packed.

Question 3

What is a motif?

Answer 3

A motif is the atomic arrangement at the lattice point.

Question 4

What is the atomic packing factor?

Answer 4

The fraction of space taken by atoms

Question 5

What is Polymorphism?

Answer 5

when a material has more than one crystal structure

Question 6

What is Allotropy?

Answer 6

A specific type of polymorphism which occurs in the solids of purely one element

Question 7

What is Anisotropy?

Answer 7

To not have the same properties in different directions

Question 8

What is Isotropy?

Answer 8

To have the same properties in different directions

Question 9

What are Vacancies?

Answer 9

Where there is a space where an atom should theoretically be.

Question 10

What are Self-Interstitials?

Answer 10

Where an atom sits in a void between normal atomic sites.

Question 11

What is the Solvent?

Answer 11

Is the host material/lattice

Question 12

What is the Solute?

Answer 12

Is the impurity

Question 13

What is Substitutional?

Answer 13

Impurity atom replaces host atom.

Question 14

What is Interstitial

Answer 14

Impurity atoms fill voids or interstices among host atoms

Question 15

What are the types of linear defects?

Answer 15

1) Edge, A linear defect centred where there is an extra half plane of atoms and there is localised lattice distortion.
2) Screw, A shear distortion in the lattice such that shear and unsheared parts of the crystal are defined by a line.

Question 16

What are external surface planar defects?

Answer 16

Where the surface of a material has a high energy due to them not being able to bond on one side.

Question 17

What are grain boundary planar defects?

Answer 17

As not all atoms are fully bonded at grain boundaries the is an energy associated with the grain boundary which increases as misorientation increases.

Question 18

What are twin boundary planar defects?

Answer 18

A specific type of grain boundary that has mirror-like symmetry.

Question 19

What are stacking fault planar defects?

Answer 19

Where the normal sequence of stacking planes is disrupted.

Question 20

What are phase boundary planar defects?

Answer 20

Where there are two different phases either side of the boundary.

Question 21

What are Burgers Vectors?

Answer 21

Burgers vectors defines a magnitude and direction of lattice distortion associated with dislocations.

Question 22

What is Slip?

Answer 22

A tendency of a material’s particles to undergo plastic deformation dues to a dislocation motion within the material. Occurs in the closest packed planes as it is the lowest energy route.

Question 23

What are Slip systems?

Answer 23

A combination of close packed planes and in the most close-packed direction

Question 24

What is Miscibility?

Answer 24

A scale of how substances combine to form a homogenous solution without precipitates.

Question 25

Draw the following on cubic unit cells, [001], [211], [120], (110), (201), (111).

Answer 25

look them up

Question 26

Draw the following on hexagonal prism unit cells (0001) , (10-11),(1-100), (0-111).

Answer 26

look them up on practice exams

Question 27

What are BCC, FCC, and HCP’s axial relationships and interaxial angles?

Answer 27

BCC: a=b=c, α=β=γ=90
FCC: a=b=c, α=β=γ=90
HCP: a=b (not) c , α=β=90 and γ=120