Chapter 18 Chemistry and Materials

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Chapter 18 Chemistry and Materials
Diamond Paper, plastic, metals, glass, ceramics
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18.1 Paper is made of cellulose fibers

• Paper was first made in China as early as AD 100,
  of mulberry bark, and then introduced to Western
  world by Arabs in eighth century. The first paper
  mills were built in Spain in 11th century.

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• The use of wood to produce paper was started in
  USA.
• Additives such as rosin (??) and alum (??) were
  added to strengthen paper and make it accept ink
  well. Chlorine as used to bleaching paper and
  titanium dioxide (???)was used to make the paper
  white.
• Acidic paper, acid-free paper and alkaline paper
• Plants alternative to trees willow (?), kenaf
  (?). They usually have high fiber content and
  grow fast.
• 70 million tons of paper are used in USA one
  person 230 kilograms or six trees.

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18.2 The development of plastics involved
experimentation and discovery

• The search for a lightweight, nonbreakable,
  moldable material began with the invention of
  vulcanized rubber (????).

isoprene
polymerization
polyisoprene
Fig18.5 isoprene molecules react with one another
to form polyisoprene, the fundamental chemical
unit of natural rubber, which comes from rubber
trees
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Charles Goodyear discovered the rubber
vulcanization in 1837.
Polymer strands
Fig18.6 (a) when stretched, the individual
poly-isoprene strands in natural rubber slip past
one another and the rubber stays stretched. (b)
when vulcanized rubber is stretched, the sulfur
cross-links hold the strands together, allowing
the rubber to return to its original shape
Stretched with little tendency to snap back to
original form
(a) Original form
Polymer strands
Stretched with great tendency to snap back
because of cross-links
(b) Original form with disulfide cross-links
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Nitrocellulose and celluloid
Nitrate group
Fig 18.7 nitrocellulose, also known as cellulose
nitrate, is highly combustible because of its
many nitrate groups, which facilitate oxidation
Nitrocellulose (cellulose nitrate)
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Bakelite and phenolic resin (????)
Fig 18.9 the molecular network of bakelite shown
in two dimensions. The actual structure projects
in all three dimensions. The first handset
telephones were made of bakelite
Polymers win in World War IISynthetic rubber,
radar, tank and tentPolymer and environment
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18.3 Metals come from the Earths limited supply
of oresMetallic bond is responsible for the high
conductivity and high gross.
Fig18.14 metal ions are held together by freely
flowing electrons. These loose electrons form a
kind of electronic fluid that flows through the
lattice of positively charged ions
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The form in which a metal is most likely to be
found in nature is a function of its position in
periodic table.
Fig 18.19 which compound of a metal is most
prevalent in nature is related to the metals
position in the periodic table
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Metal-containing compounds can be converted to
metals
Transforming the metal-containing compound to a
metal is less energy intensive Transforming the
metal-containing compound to a metal is more
energy intensive
Sheets of impure copper
Sheets of pure copper
Solution containing CuSO4
Fig 18.21 high-purity copper is recovered by
electrolysis. Pure copper metal deposits on the
negative electrode as copper ions in solution
gain electrons. The source of these copper ions
is a positively charged electrode made of impure
copper
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Some metals are most commonly obtained from metal
oxides
Fig 18.22 a mixture of iron oxide ore, coke, and
limestone is dropped into a blast furnace, where
the iron ions in the oxide are reduced to metal
atoms
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Steel Manufacturing via the Oxygen Process
(oxidation process)
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External pressure
Pure iron is fairly soft and malleable because of
voids between atoms
Fe
void
Fig 18.24 steel is stronger than iron because of
the small amounts of carbon it contains
External pressure
When the voids are filled with carbon atoms, the
carbon helps hold the iron atoms in their
lattice. This is strengthened metal is called
steel
C
Metal resources are not unlimited
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18.4 Glass is made primarily of silicates18.5
Ceramics are hardened with heat

• brittle, but withstand extremely high temperature
• Ceramic engine and superconductors (???)

Fig 18.32 Engine parts made of Ceramic Silicon
Nitride ,which is a High-strength material
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18.6 Composites (????) combine fibers and a
thermoset medium
wood
Rocket cone
Fiberglass
Graphite fiber composite
Fig 18.34 a few examples of composite materials
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Fig 18.35 the all-composite voyager airplane
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More Important!

• The properties of materials are decided by their
  chemical structure.
• (Structure Property Relationships)
• Features of each type of material.
• (Advantages and shortcomings)
• Selection of materials!

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• Type Metals Ceramics Polymers
• Chemical structure Metal bond Covalent
  bond Covalent bond
• Change of atom position easy difficulty easy
• Hardness medium high low
• Toughness tough brittle tough
• Thermal stability medium high low
• Chemical stability low high medium
• Moldability high low high
• Processing cost medium high low
• Ability to form film medium hard easy
• Conductivity high low low
• Cost medium high low
• Recycleability high low medium

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Property requirement and Selection of materials

• Valve hard, friction resistance, metal
• Valve in contact with chemicals?
• Plane metal or alloy
• Supersonic planes?
• Tennis racket wood is not strong enough and too
  heavy, so?

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Composites

• To combine the advantages of different materials
• Expansive!
• Difficulty to recycle!
• So any new type of composites?