EXAM Flashcards
Mer
repeatable unit in a polymer
material suitable for cladding a building
Aluminium
vinyl flooring in a building is ….
Thermoplastic
BCC
6 planes x 2 directions = 12 systems
FCC
4 planes x 3 directions = 12 systems
HCP
1 plane x 3 directions = 3 systems
Manufacturing Polymeric Materials
Ultrasonic Welding
Thermoforming
Injection Moulding
Extrusion
Metal Defects
Dislocation
Interstitial
Substitutional
Grain Boundary
Cold rolling increases number of …. in a crystalline structure.
Dislocations
Suitable method for manufacture of a Steel Beam
Rolling of a Billet
Hydration of dicalcium silicate is…
Exothermic
Teflon is a …
Polymer
Bohr Model of the atom
electrons in discrete orbitals
energies of electrons quantised
Wave-Mechanical atomic model
wave and particle like properties
position of electron as a probability
Dislocation effects on... Yield strength ductility hardness elastic modulus toughness
increases decreases increases same decreases
Ferrite
BCC, alpha iron
Austenite
FCC, gamma iron
Cementite
Iron Carbide, Fe3C
Pearlite
laminated structure of Ferrite and Cementite formed during cooling by the diffusion of Carbon
Hardenability
ease of martensite formation
Martensite
non-equilibrium phase formed during rapid cooling when diffusion is too slow to allow Pearlite formation
very hard and brittle
APFS: FCC BCC HCP SC
- 74
- 68
- 74
- 52
Defects found in crystalline solids
Point (atoms)
Line (dislocations)
Area (grains)
Volume (precipitates)
Eutectic
Liquid
Eutectoid
Solid
Glass
Crystalline
Engineered Ceramic
Non-crystalline
how does impure limestone produce cement?
heated to around 1450 ºC
Clinker phases formed during manufacture of cement
Tricalcium Silicate (Alite) initial strength
Dicalcium Silicate (Belite) late strength
Tricalcium Aluminate
Calcium alumni ferrite
Gypsum
added to cement to stop flash set from the trillium aluminate phase. forms ettrengite.
Metal properties
strong, ductile
high thermal and electrical conductivity
opaque, reflective
Ceramic properties
compounds (metallic and non-metallic)
brittle, glassy, elastic
non conducting
Polymer properties
Covalent bonding
soft, ductile, low strength and density
translucent / transparent
Atomic Mass Unit
1/12 th mass of Carbon-12 atom
Relative Atomic Mass
mass of one mol
Electropositive (left)
Electronegative (right)
give up electrons to become +ve ions
acquire electrons to become -ve ions
Ionic Bonding
ceramics
large bond energy metallic and non-metallic non-directional bonding relatively strong brittle
Covalent Bonding
polymers, glasses and ceramics
variable bond energy sharing electrons (non-metal compounds) directional bonding very strong brittle
Metallic Bonding
metals
variable bond energy valence electrons become delocalised (metals and alloys) non-directional bonding intermediate strength ductile
Van Der Waals
polymers
weak secondary bond
directional
very ductile
Hydrogen Bonding
weak secondary bond
interaction and delocalisation of hydrogen electrons
Crystalline
atoms situated in a periodic array over large atomic distances
(dense, regular packing) –> lower energy
Amorphous
no long range order, non-crystalline
non-dense, random packing
Unit Cell
basic building block unit that repeats in space to create crystal structure
Ductility
ease of plastic deformation
Anisotropic
properties vary with direction
Poisson’s Ratios:
metals
ceramics
polymers
- 33
- 25
- 40
Yield Strength
stress at which noticeable plastic deformation has occurred
Tensile Strength
max. stress that a structure can sustain
Toughness
energy to break a unit volume of material
Resilience
ability of a material to store energy
Hardness
resistance of materials to localised plastic deformation
Metal strengthening mechanisms
reduce grain size
solid-solution strengthening
precipitation strengthening
cold work
Alloy
metallic substance made up of more than one element
Low Carbon Steels
car body components, reinforced concrete
carbon <0.25wt%
unresponsive to heat
soft and weak
excellent ductility
Medium Carbon Steels
railway wheels, gears
carbon 0.25-0.6wt%
heat treatable only in thin sections
stronger, wear resistant
less ductile
High Carbon Steels
cutting tools, blades
carbon 0.6-1.4wt%
heat treatable in thick sections
strong, hard, wear resistant
least ductile
Casting
sand casting
investment casting
die casting
Forming
forging
rolling
extrusion
drawing
Joining
powder processing
welding
heat affected zone
Glass properties
brittle
low toughness
amorphous
Glass Fabrication Techniques
pressing
blowing
drawing
fibre forming
Strengthening of Glass
tempering
chemical
reinforcement
Natural Ceramics
Sedimentary rocks
Igneous rocks
Traditional Ceramics
local clays
Vitrification
formation of liquid glass which flows into pores and produces dense ceramic
Polymers
organic macromolecules made of repeating ‘mer’ units
Thermoplastic
soften on heated
linear chains
weak intermolecular bonding
ductile
Thermoset
degrade on heating
heavily cross linked
brittle
polymerisation
chemical process that causes a large number of monomers to combine to form the polymer
Elastomers
linear with some cross linking
shape retention
Cold Drawing
molecules drawn out and aligned
elastic modulus increases
tensile strength increases
ductility decreases
Concrete
composite material, aggregates held together by a cementing medium
cement paste functions
1) fill voids between aggregates
2) provide strength to hardened concrete
aggregate functions
1) cheap fill for cementing material
2) provide a mass of particles which resist loads, abrasion…
3) reduce volume change
Portland Cement raw materials
Limeston, Clay and Gypsum
super-plasticisers
high range water reducing admixtures that don’t affect setting
compressive strength
maximum stress that the concrete may carry
related to water/cement ratio
tensile strength
roughly a 1/10th of compressive strength
Mortar
paste + fine aggregate
Portland Cement Production
1) grind raw materials
2) burn in large rotary kiln at 1450º to form balls known as Klinker
3) cool klinker and grind to fine powder
4) add gypsum
Hydration (2 methods)
1) In Solution
2) Solid State
Hydration Products
Calcium Silicate Hydrate
Calcium Hydroxide
Tricalcium Aluminate Products
1) Ettringite (early stages of hydration)
2) Monosulfate (Later stages of hydration)
Cement Gel
rigid aggregation of very small particles
porosity = 28%
Water within hardened cement paste
1) chemically combines in the hydrates
2) interlayer water
3) absorbed water
4) capillary water
Pozzolanic
material containing active Silica
accelerators / retarders
increase / decrease rate of hydration
increase / decrease solubility of C3A
Aggregates
hard, strong, free from impurities
s, d, p and f block orbitals
1-2
3-12
13-18
lanthanides and actinides
valence electrons
single electron in the outer shell of an atom, can be gained or lost (incomplete outer shell)
