Complete MMME1029 Lecture 2
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2. What are the main classifications of materials?
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2. What are the main classifications of materials?
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> Metals, glass and ceramics, plastics, elastomers,
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> Metals, glass and ceramics, ~~plastics, elastomers,~~ polymers, composites, and semiconductors
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3. [There are] Few Iron Age artefacts left. Why?
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3. [There are] Few Iron Age artefacts left. Why?
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2. What material properties were mentioned in the second slide set?
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2. What material properties were mentioned in the second slide set?
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> Young's modulus, specific heat, coefficient of thermal expansion
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> Young's modulus, specific heat, coefficient of thermal expansion
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# Lecture 2
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## Metals
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- Ductile (yields before fracture)
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- High UFS (Ultimate Fracture Stress) in tension and compression
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- Hard
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- Tough
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- High melting point
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- High electric and thermal conductivity
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## Ceramics and Glasses
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- Brittle --- elastic to failure, no yield
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- Hard (harder than metals)
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- Low UFS under tension
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- High UFS under compression
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- Not tough
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- High melting points
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- Do not burn as oxide ceramics are already oxides
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- Chemically resistant
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- Poor thermal and electric conductivity
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- Wide range of magnetic and dielectric behaviours
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## Polymers
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- Organic---as in organic chemistry (i.e. carbon based)
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- Ductile
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- Low UFS in tension and compression
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- Not hard
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- Reasonably tough
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- Low threshold temperature to charring and combustion in air or pure oxygen
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- Low electrical and thermal conductivity
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- There are some electrically conductive polymers
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## Composites
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- Composed of 2 or more materials on any scale from atomic to mm scale to produce properties that
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cannot be obtained in a single material
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- Larger scale mixes of materials may be called 'multimaterial'
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- Material propertes depends on what its made of
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## Organic vs Inorganic Materials
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- Organic materials are carbon based
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- From chemistry, organic compounds are ones with a C-H bond
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- Inorganic compounds do not contain the C-H bond
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## Crystalline vs Non-Crystalline Materials
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- Most things are crystalline
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- Ice
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- Sugar
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- Salt
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- Metals
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- Ceramics
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- Glasses are non-crystalline
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## Material Density
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$$\rho = \frac m v$$
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- Density if quoted at STP (standard temperature and pressure---$298$ K and $1.013\times 10^5$ Pa)
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- Metals, ceramics, and glasses are high density materials
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- Polymers are low density
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- Composites span a wide range of density as it depends on the materials it is composed of
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e.g. composites with a metal matrix will have a much higher density than those with a polymer
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matrix
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## Material Melting Points
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- Measured at standard pressure and in an intert atmosphere (e.g. with Nitrogen, Argon, etc)
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- Diamond and graphite will survive up to 4000 \textdegree{}C in an inert atmosphere but would
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burn at around 1000 \textdegree{}C in oxygen
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- High melting points -> high chemical bond strength
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## Material Corrosion
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- It's not just metals that corrode
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- Polymers
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- UV degradation
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- Water absorption can occur in degraded polymers
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- Glass
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- Leaching
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- Sodium ions can leave the glass when covered in water. If the water stays, the high pH water
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can damage the class
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## Self Quiz
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### Consolidation Questions 1
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1.
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i. Metal
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ii. Titanium
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2.
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i. Polymer
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ii. Polyester
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3.
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i. Ceramic
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ii. Alumino-silicate
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4.
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i. Composite
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ii. GFRP or CFRP
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5.
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i. Metal
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ii. Aluiminium alloy
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6.
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i. Metal
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ii. Aluiminium alloy
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7.
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i. Polymer
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ii. Acrylic
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8.
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i. Ceramimc
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ii. Glass
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9.
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i. Composite
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ii. Concrete
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### Consolidation Questions 2
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> ~~C~~ B
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