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Y1 Materials and Manufacturing - Sem 2 > Lectures 1-2 > Flashcards

Lectures 1-2 Flashcards

1
Q

Ceramics are

A

non-metallic, inorganic materials

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2
Q

Most ceramics are composed of

A

Si, C, or metal elements combined with O, C or N.

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3
Q

Crystalline ceramics have a —– arrangement of atoms

A

regular

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4
Q

Amorphous ceramics have an —– arrangement of atoms

A

irregular

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5
Q

Bonded ceramics are … . Includes examples of …. .

A

a combination of crystalline and amorphous structures, clay materials

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6
Q

Ceramics usually have a —- Young’s Modulus.

A

high

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7
Q

Ceramics are better in —– rather than in —–.

A

compression, tension

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8
Q

Ceramics have —– melting points

A

high

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9
Q

Ceramics, due to their melting points, are useful in what type of application

A

high temp applications

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10
Q

Ceramics do not have —— bonds, so are useful as —-

A

metallic, insulators

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11
Q

Ceramics often have —– —— conductivity

A

poor thermal

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12
Q

Ceramics are often environmentally —–, meaning they do not —— or ——-

A

stable, corrode, degrade

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13
Q

Crystalline ceramics with an edge dislocation. Why are they difficult to dislocate?

A

Due to the extra bonds with the ions that are between the larger atoms, unlike a simple crystalline metal.

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14
Q

Glass is used when talking about

A

a non-crystalline (amorphous) solid

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15
Q

Metals can form amorphous structures if they are….

A

cooled extremely rapidly, or processed carefully

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16
Q

Crystalline sillica forms a —— shaped structure

A

tetrahedral

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17
Q

Crystalline silica can form three structures;

A

quartz, crystabolite, and tridymite

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18
Q

Amorphous forms of silica are called

A

silica glasses

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19
Q

Pure forms of amorphous silica are…. (two)

A

fused silica or vitreous silica

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20
Q

Viscosity is a measure of

A

the resistance of a fluid to flow

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21
Q

Viscosity can be defined as the ratio of the

A

applied shear stress to the shear strain rate.

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22
Q

Increasing temperatures in a material, the viscosity becomes —-

A

lower (more flowy)

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23
Q

On a Volume-temp graph for a crystalline material solidification, the upper gradient represents …..

A

a low viscosity fluid aka liquid

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24
Q

On a Volume-temp graph for a crystalline material solidification, the middle vertical line represents …..

A

the material solidifying and gaining a regular structure

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25
Q

On a Volume-temp graph for a crystalline material solidification, the lower gradient line represents ….. . The upper end of the lower gradient represents …… and the lower end of the lower gradient represents …… .

A

the material becomes a solid

a solid at a high temperature
a solid at a low temperature

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26
Q

On a Volume-temp graph for an amorphous material, the upper gradient line represents …..

A

liquid at a high temperature

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27
Q

On a Volume-temp graph for an amorphous material, the lower gradient line represents ….. (two things)

A

lower temperature above T g => less compact structure

lower temperature below T g => more compact structure

28
Q

T g for Amorphous materials is the

A

glass transition temperature

29
Q

At the T g, what happens to the appearance of the material?

A

becomes glassy

30
Q

What features does the material below the T g have in terms of properties?

A
  • brittle
  • relatively hard
31
Q

Glass at a high temperature has a —- viscosity

A

high

32
Q

“frozen-in” used in the context of glass cooling is talking about the

A

atoms having insufficient time to diffuse and the disordered structure (amorphous) is “frozen-in”

33
Q

Glass does not have a definite …

A

temperature where it transforms from a solid to a liquid

34
Q

A glass material becomes —- and —–, without ——-

A

hard, rigid, crystallising

35
Q

Glass materials are often considered as ———- liquids

A

supercooled

36
Q

The strain point is

A

the temp at which internal stress is relieved within several hours

37
Q

The annealing point is

A

temperature at which internal stress is relieved within a few minutes

38
Q

What approx. viscosity does the softening point have

A

4 x 10^6

39
Q

Melting point for a glass is not when it becomes fully liquid, but is when the glass has a ….

A

low viscosity t

40
Q

How does the glass react when it is at the softening point

A

glass slumps under its own weight

41
Q

Working point for a glass means

A

it is soft enough to be formed into shape

42
Q

Point defects in ceramics example

A

vacancies

43
Q

—– can be found in ceramics but —— is extremely difficult due to the …

A

dislocations, slip, repulsion of ions with the same charge in the crystal structure

44
Q

A thermal shock in a ceramic is caused by

A

uneven rapid cooling and heating

45
Q

What happens when thermal shock is induced in a ceramic

A

the exterior cools more rapidly than the interior, placing the exterior under tension

46
Q

The tension in the exterior of the ceramic through thermal shock can lead to

A

crack initiation and rapid fracture

47
Q

In a clay, there are —— which contain strong —- and —– bonds but the layers are bonded together by ….

A

layers, ionic covalent, weaker van der waals forces

48
Q

How does the water make the clay moldable?

A

The water molecules get in between the layers of the clay

49
Q

Diffusion is a —— / —— depenedent phenomenon

A

time / temp

50
Q

Higher temperature = —— diffusion

A

faster

51
Q

If a material is loaded in tension it can begin to … . This is due to the process of ——

A

plastically deform over time, creep

52
Q

In a ceramic, edge dislocations are more likely to become —– than —— deforming.

A

fractures, plastically

53
Q

How would they commonly use a ceramic eg tungsten carbide for a tougher blade/drill? Why do they use it in this quantity?

A

A small section that is attached onto the edge where the blade/drill will come into contact with the material being worked, only used in small quantities as the ceramic is tough but brittle so could cause whole blade to fracture

54
Q

By adding different elements to the initial composition of glass, the material becomes …. (two points)

A
  • more easy to work
  • lower working temp
55
Q

With an amorphous glass material, the solidification process follows what sort of trend?

A

It is less defined and happens over a longer period of time compared to a crystalline which solidifies at a defined temperature

56
Q

Creep is faster at (2)

A
  • higher temp
  • higher applied stress
57
Q

Creep rate =

A

C σ^n exp ( -Qc / R T )

C - constant
n - constant
σ - stress
R - gas constant
Qc - activation energy for creep
T - temp

58
Q

Fatigue is when a material is

A

subjected to repeated application and removal of stress below its yield strength

59
Q

After fatigue has set in, failure is typically ——– to the stress direction

A

perpendicular

60
Q

Ntoches, scratches and indentations are classed as —– —–

A

stress raisers

61
Q

Wear occurs when

A

components are in contact and there are only a small contact points that take the whole load

62
Q

Adhesive wear is

A

when the asperties are plastically deformed and welded together, which leads to them being torn away from the surfaces

63
Q

Asperities are

A

the small contact points between components

64
Q

Abrasive wear occurs when

A

hard particles of grit are between the surfaces which cause material to be removed

65
Q

Corrosive wear is

A

chemical or electrochemical damage of the material surface combined with adhesive or abrasive wear

Y1 Materials and Manufacturing - Sem 2 (9 decks)

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