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CHEM313 > TH Manufacturing Materials > Flashcards

TH Manufacturing Materials Flashcards

1
Q

What is the structure of SIO2 in quartz

A

Very clear short range order

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2
Q

What is the structure of SIO2 in glass

A

More jumbled structure than in quartz

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3
Q

How can crystalline structures be identified

A

X-ray diffraction

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4
Q

How can amorphous samples beCharacterised

A

They scatter x-rays so are more difficult to characterise

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5
Q

What is a linear polymer

A

A polymer made of straight-chain

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6
Q

What is a branched polymer

A

A straight-chain polymer with branch chains in each repeating unit

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7
Q

What is a cross-linked polymer

A

A polymer with regular links between chains

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8
Q

What is a polymer network

A

A 3-D arrangement of cross-linked polymers

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9
Q

What is a thermosetting plastic

A

A plastic that does not soften upon heating as it is cross-linked

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10
Q

What is a thermoplastic

A

A plastic that softens when heated and hardens when cooled

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11
Q

What is silicon

A

A crystalline elemental solid

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12
Q

What is silica

A

SIO2 sand quartz or glass

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13
Q

What is silicone

A

I synthetic polymer

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14
Q 
What is the stability of
SiH
SiX
SiC
SiO
A

SiH v reactive
SiX substitution reactions
SiC quite stable
SiO v. Strong

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15
Q

Is silicone thermoplastic or thermoset

A

Thermoplastic but it can be cross-linked

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16
Q

How can silicone be cross-linked

A

PDMS fabrication
peroxide curing
condensation curing

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17
Q

How does PDMS fabrication work

A

Polymer is heated with vinyl alkene and cross links

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18
Q

How does peroxide curing work

A

Polymer with methyl branches reacts with a radical and cross links

19
Q

How does condensation caring work

A

Esther at end of polymer is hydrolysed Then undergoes SNT with another Esther at a silicon to form the new polymer

20
Q

What is curing

A

The process of forming a thermosetting plastic by cross-linking

21
Q

What are the 3 methods of silica network formation

A

Fumed
Oxidation of silicon
Sol gel synthesis

22
Q

What is the reaction equation for fumes silicon network formation

A

SiCl4 + 2H2 +O2 -> SiO2 + 4HCl

23
Q

What is the reaction equation for oxidation of silicon

A

Si + O2 -> SiO2

24
Q

What is the reaction equation for sol gel synthesis

A

Si(OR)4 + 2H2O -> SiO2 + 4ROH

25
Q

What methods can be used to characterise amorphous in soluble material

A

Microscopy
Solid-state spectroscopy
EDX(energy dispersive x-ray analysis)
thermal analysis

26
Q

what are the 3 types of microscopy

A

light
TEM
SEM

27
Q

what are the pros and cons of light microscopy

A

shows colour
limited by light wavelength
interacts with all layers

28
Q

what is the main benefit of electron microscopy

A

much higher resolution

29
Q

what does SEM focus on

A

the surface of the subject

30
Q

what does TEM focus on

A

looking through the subject

31
Q

how does SEM work

A

electrons are accelerated towards sample
beam is focused and rastered
beam is scattered and observed

32
Q

how does TEM work

A

electrons are accelerated towards sample
electrons are focused as in light microscopy
transmitted through sample
observed via fluorescence or detectors

33
Q

how can TEM results be analysed

A

few electrons pass through heavy metals - appear darker

34
Q

which electron microscopy gives higher resolution

A

TEM

35
Q

what is a requirement of TEM

A

thin sample

36
Q

give an effective way to determine composition

A

energy dispersive x ray spectroscopy

37
Q

how does energy dispersive x ray spectroscopy

A

uses high energy elections to eject inner electrons
higher energy electron drops in energy to fill gap
x ray is released frequency indicates atom

38
Q

what factors should be considered when analysing elemental composition

A

incident electrons must have enough energy

needs ideal sample to give quantitative results

39
Q

what happens in electron diffractions

A

electrons interact with electron cloud atoms

40
Q

how does the structure effect electron diffraction results

A

sharp ring - crystal

broad ring - amorphous

41
Q

how are samples prepared for SEM

A

dry
deposited onto sticky carbon tab
insulating material is covered in conductive coating

42
Q

how is a sample prepared for TEM

A

sample placed on a supporting grid - usually copper

43
Q

what is a microtomy

A

device for cutting thin sections of a material

CHEM313 (5 decks)

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