TH Manufacturing Materials Flashcards
What is the structure of SIO2 in quartz
Very clear short range order
What is the structure of SIO2 in glass
More jumbled structure than in quartz
How can crystalline structures be identified
X-ray diffraction
How can amorphous samples beCharacterised
They scatter x-rays so are more difficult to characterise
What is a linear polymer
A polymer made of straight-chain
What is a branched polymer
A straight-chain polymer with branch chains in each repeating unit
What is a cross-linked polymer
A polymer with regular links between chains
What is a polymer network
A 3-D arrangement of cross-linked polymers
What is a thermosetting plastic
A plastic that does not soften upon heating as it is cross-linked
What is a thermoplastic
A plastic that softens when heated and hardens when cooled
What is silicon
A crystalline elemental solid
What is silica
SIO2 sand quartz or glass
What is silicone
I synthetic polymer
What is the stability of SiH SiX SiC SiO
SiH v reactive
SiX substitution reactions
SiC quite stable
SiO v. Strong
Is silicone thermoplastic or thermoset
Thermoplastic but it can be cross-linked
How can silicone be cross-linked
PDMS fabrication
peroxide curing
condensation curing
How does PDMS fabrication work
Polymer is heated with vinyl alkene and cross links
How does peroxide curing work
Polymer with methyl branches reacts with a radical and cross links
How does condensation caring work
Esther at end of polymer is hydrolysed Then undergoes SNT with another Esther at a silicon to form the new polymer
What is curing
The process of forming a thermosetting plastic by cross-linking
What are the 3 methods of silica network formation
Fumed
Oxidation of silicon
Sol gel synthesis
What is the reaction equation for fumes silicon network formation
SiCl4 + 2H2 +O2 -> SiO2 + 4HCl
What is the reaction equation for oxidation of silicon
Si + O2 -> SiO2
What is the reaction equation for sol gel synthesis
Si(OR)4 + 2H2O -> SiO2 + 4ROH
What methods can be used to characterise amorphous in soluble material
Microscopy
Solid-state spectroscopy
EDX(energy dispersive x-ray analysis)
thermal analysis
what are the 3 types of microscopy
light
TEM
SEM
what are the pros and cons of light microscopy
shows colour
limited by light wavelength
interacts with all layers
what is the main benefit of electron microscopy
much higher resolution
what does SEM focus on
the surface of the subject
what does TEM focus on
looking through the subject
how does SEM work
electrons are accelerated towards sample
beam is focused and rastered
beam is scattered and observed
how does TEM work
electrons are accelerated towards sample
electrons are focused as in light microscopy
transmitted through sample
observed via fluorescence or detectors
how can TEM results be analysed
few electrons pass through heavy metals - appear darker
which electron microscopy gives higher resolution
TEM
what is a requirement of TEM
thin sample
give an effective way to determine composition
energy dispersive x ray spectroscopy
how does energy dispersive x ray spectroscopy
uses high energy elections to eject inner electrons
higher energy electron drops in energy to fill gap
x ray is released frequency indicates atom
what factors should be considered when analysing elemental composition
incident electrons must have enough energy
needs ideal sample to give quantitative results
what happens in electron diffractions
electrons interact with electron cloud atoms
how does the structure effect electron diffraction results
sharp ring - crystal
broad ring - amorphous
how are samples prepared for SEM
dry
deposited onto sticky carbon tab
insulating material is covered in conductive coating
how is a sample prepared for TEM
sample placed on a supporting grid - usually copper
what is a microtomy
device for cutting thin sections of a material
