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Materials & their properties (Composites (Examples (Fibreglass (uses…
Materials & their properties
Ceramics
non-metal solid, high mp, not C based
Can be made from clay
when dug it is soft and can be moulded
fired at high temperatures, hardens, clay ceramic
therefore ideal for pottery and bricks
Another example is glass
transparent
moulded when hot
brittle when thin
Most is soda-lime glass
mixture of limestone, sand, and sodium carbonate
(soda) heated till liquid, cools as glass
borosilicate glass
higher mp than soda-lime
made same way
mixture of sand and boron trioxide
Composites
generally 2 different materials
1 material embedded in another
Fibres or fragments (reinforcement) surrounded
by matrix acting as a binder
properties depend on materials made from
Examples
Fibreglass
fibres of glass embeded in matrix of polymer (plastics)
low density like plastic
very strong like glass
uses
skiis, surfboards, boats
Carbon fibre
polymer matrix
reinforcement
long chain of C atoms, C fibres
C nanotubes
very strong and light
uses
aerospace, sports car
Concrete
aggregate embeded in cement
aggregate - any material made from
fragments, usually sand and gravel
very strong
used in building materials
wood
natural composite
cellulose fibres held in organic polymer matrix
Polymers properties
how made. E.g
low density poly(ethene)
moderate temperature, high pressure & catalyst
flexible used for bags and bottles
HD
lower temp and pressure and different catalyst
more rigid, water tanks and drain pipes
monomers made from
these weak bonds determine the property
Thermosetting polymers
polymers that cross links between polymer chains
solid structure don' t soften when heated
strong, rigid, hard
Thermosoftening polymers
polymer chains entwined together with weak forces
can melt these are remould them
Suitablility for different jobs
Ceramics
E.g, glass, clay ceramic such as porcelain and bricks
insulator of heat and electricity
brittle - not flexibel and break easily, stiff
composite
depends on binder and reinforcer
therefore can have many different uses
Polymers
insulator of heat and electricity
can be flexible, easily moulded
many uses including clothing, insulating electrical items
Metals
malleable, good conductors of heat and electricity,
ductile - can be drawn into wires, shiny, stiff
uses, wires, car body work, cutlery
Alloys
pure metal often soft
made by adding another element
disrupts structure, making it harder
Steels
Fe & small C and sometimes other metals
low C steel
0.1-0.3% C
easily shaped
car bodies
high C
0.22-2.5%C
very hard, inflexible
blades for cutting tools, bridges
Stainless
chromium and sometimes nickel
corrosion resistant
cutlery, containers of corrosive substances
other
Bronze
Cu + Tin
harder than Cu
medals, ornaments, statues
Brass
Cu & Zn
more malleable
lower friction, water taps, door fitting
Gold Alloys
jewellery
Zn, Cu, Silver to harden gold
pure os 24 carat
18 carat is 18 / 24 75%
Alluminium
aircraft as lightweight
too soft so other metals added to make stronger
Corrosion
when metals react with substances in
the environment and are gradually destroyed
Iron corrodes easily, it rusts
only when in contact with oxygen and
water which are present in air
rust is hydrated Iron(III) oxide
only occurs on exposed to air surface
rust flakes off leaving more iron to rust
Experiment iron nail
just water
boiling water removes O2, oil on
top stop air getting in
air, no water
can place Calium
Chloride to absorb any water
Aluminium corrodes when exposed to air
not completely destroyed
aluminium oxide forms protective layer, not flake away
Rust Prevention
Barrier
Painting/Coating with plastic
Electroplating with another metal that won't crode
oiling and greasing for moving parts, e.g bicycle chain
Sacrificial method
placing more reactive metal
such as Zn or Mg with iron
Both, galvanised by spraying with coating of Zn