Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Kinetics of Materials > Nucleation, Crystallization, and Growth > Flashcards

Nucleation, Crystallization, and Growth Flashcards

1
Q

Nucleation

A

Initial formation of one phase inside another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

All nucleation processes have:

A

Energetic barrier against formation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Two types of nucleation

A

Homogeneous, heterogeneous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Homogeneous nucleation

A

Spontaneous particle formation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Heterogeneous nucleation

A

Formation of particle on a seed of foreign material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Why seed important in heterogeneous nucleation?

A

Seed provides lower barrier to formation at interface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Majority of nucleation processes are of what type

A

Heterogeneous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Understanding nucleation rate diagram

A

Heterogeneous nucleation peaks at a higher temperature so it is easier. Supercooling is required to initiate homogeneous nucleation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why nucleation limited on diagram?

A

Lowered concentration of nucleating material after phase change, and also atoms prefer to grow on existing nuclei.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Weaker bond energies in a material mean (wrt supercooling)

A

More supercooling is needed to induce homogeneous nucleation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What limits nucleation in slightly undercooled liquids?

A

Surface tension of small particle radius

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What produces nucleation in slightly undercooled liquids?

A

Bulk fluctuations overcoming surface tension barrier to nucleation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Undercooled liquid is considered to be (wrt stability)

A

metastable phase – free energy not minimum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The free energy change of nucleation is labeled:

A

\DeltaG_r

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

The free energy change of phase formation is labeled:

A

\DeltaG_v

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Critical radius, how labeled

A

r*

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How r* derived

A

Maximum value of free energy of nucleation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What controls surface tension of particles

A

Fluctuations in bulk or seed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

\sigma in nucleation equations

A

Surface tension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Nr*/N

A

Number of particles of critical radius compared to total number of particles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Nr*/N implications for density

A

Higher density results in less nucleation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Nr*/N implications for phase transformation energy

A

Higher phase transformation energy change increases particles of critical radius

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Nr*/N unincluded effect

A

More prior particles result in more collisions resulting in more nucleation

24
Q

Nr*/N implication for temperature

A

Decrease of temperature increase Nr* because of increase in undercooling which increases phase transformation change in free energy

25
Q

Example of liquid mobility effect on undercooling

A

High atom mobility in molten metal means that undercooled metals nucleate rapidly.

26
Q

Undercooling in glass

A

Glass is viscous and has low mobility, resulting in fewer clusters forming.

27
Q

Nucleation rate is labeled:

A

I

28
Q

Rate at which atoms reach the critical nucleus is labeled:

A

R_(r^*)

29
Q

Crystallization

A

Phase transition of a disordered fluid to a crystal

30
Q

When crystallization starts

A

As soon as nucleation seeds form

31
Q

Types of crystallization

A

Cooling, evaporation, precipitation

32
Q

Cooling crystallization

A

Result of decrease in temperature dependent solubility of a solute

33
Q

Evaporation crystallization

A

Result of evaporation of solvent

34
Q

Two types of precipitation

A

Reactive crystallization, anti-solvent

35
Q

Reactive crystallization

A

Chemical reacts with solute causing insoluble solid to form

36
Q

Anti-solvent

A

A solvent which binds better to a solute than the initial, causing the first solvent to crystallize

37
Q

Mechanism by which polymers can locally crystallize

A

Chain folding

38
Q

What kind of polymer structures crystallize better?

A

Linear polymer structure

39
Q

Two types of polymer crystallization

A

Solution, melt

40
Q

Solution crystallization

A

Caused by chain folding

41
Q

Melt crystallization

A

Happens across molecules by the lineup of chains

42
Q

Vi

A

Rate of crystallization for component i

43
Q

Rate of crystallization for component i

A

Vi

44
Q

Growth in solution vs. growth in melt

A

Solution growth is slow; melt growth is fast

45
Q

Why solution growth slow

A

Large density diff. b/t solution and crystal

46
Q

Why melt growth fast

A

Comparable density b/t solution and crystal

47
Q

What controls growth in solution

A

Atomic movements from solution to crystal (i.e. diffusion)

48
Q

What controls growth in melt

A

Heat flow controls growth in melt

49
Q

Two examples of crystal growth

A

Bridgman growth & Czochralski growth

50
Q

Bridgman growth

A

Single seed crystal is cooled at one end of a container.

51
Q

Czochralski growth

A

Liquid is undercooled; crystal is pulled up at rate of growth. Interface between crystal and melt is effectively stationary.

52
Q

Growth rate of CZ process determined by

A

Undercooling at interface

53
Q

Undercooling at CZ interface controlled by

A

Heat flow, via conduction heat transfer (crucible) and convection (liquid), heat loss from crystal

54
Q

Changes occurring during CZ process

A

Crystal surface area expands, so heat loss from crystal changes, and liquid level drops, so coupling between heater and melt changes

55
Q

Coarsening growth

A

Particles smaller than r* shrink and larger than r* grow

56
Q

What controls surface tension of particles

A

Fluctuations in bulk or seed

Kinetics of Materials (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions