Resources Flashcards
When did the first processed materials appear
16th Century
2 Most abundant elements in the universe
Hydrogen then Helium
Most abundant elements in earths crust
Oxygen, silicon, Aluminium
Info about crust and its elements
Elements are not evenly distributed, Heavier elements tended to sink under gravity. Lighter minerals in the crust.
Most elements are found as…
Minerals ( usually sulphides or oxides)
Two mechanisms in mineral formation
Dissolution and precipitation
How are small crystallites formed
Rapid Cooling i.e. Under sea volcano sites
What is an aggregate?
Sands, gravels, and clays from erosion or mechanical breakdown or rock.
Materials in cement
Limestone and Clay
What is the cooled cement mixture ground with?
Calcium Sulphate
Fine layer of needle like crystals of ___ , forms after 10 mins of cement hydration
Ettringite
How was hoover dam cooled?
Using Colorado river as a coolant
What are clays made from?
Fine sedimentary particles from weathered rocks. Formed by acidic chemical attack on igneous rocks by rain water weathering
How does ZrO2 help toughening ceramics?
When material gets damaged it switched to bulkier form and propagation of the crack is prevented
How can you control failure in ceramics?
Lower number of pores or inclusions,
Transformation toughening,
Ceramic fibre composites
Main ingredient in glass?
SiO2 (Sand), Trona was used in early glass.
What is modern glass made of?
Limestone, dolomite, soda ash
What lowers the melting point in the initial glass reaction?
Soda Ash
What is molten glass drawn out onto?
Molten tin bath
How is glass relieve of its stress after cooling?
Annealed at 200°C
How is glass cut?
Using computer controlled diamond cutters
How to overcome mechanical weakness of glass?
Lower the defects and pores,
Laminate with polymer layers,
Include metal grid between layers
Explain Copper Electrolysis
blister copper dissolves at anode and is reduced at cathode. In CuS04 solution for electrolyte
Tin usage
Tin cans prevent corrosion of iron.
Make alloys with copper,
Oxide used as pigments for paints
How is iron extracted?
Blast furnace, 40m high steel tower lined with refractory bricks. Air blasted in at base, coke burns releasing heat and CO2, CO2 is reduced to CO which reduces the ore into Pig Iron.
Pig Iron
Very brittle because of impurities, these are lowered by beating and open hearth processes
Wrought Itron
Puddling removes impurities,
Hitting with hammer drives out slag,
More malleable, less hard
How is Aluminium acquired
Caustic soda is added to Bauxite ore which causes aluminium to dissolve. It’s then re-precipitated by adding acid
What is corrosion?
When a metal reacts with oxygen and water to form a metal oxide
Galvanising
Use of zinc as sacrificial anode to passivate corrosion
Alloying
Steel with Chromium as chrome oxidises more preferentially to Iron,
Extrusion
Beads are melted and forced through a die, die shape indicates product
Blow moulding
Hollow tube of polymer goes through mould, air forces plastic to the shape of mould.
Injection Moulding
Molten plastic forced into mould under pressure, mould formed in two halves.
Making thing plastic sheets
Pressurised plastic tube is heated and blows out like a balloon, balloon is collapsed and trimmed into two layers
Methods of plastic moulding
Extruding, Blow moulding, Injection moulding, Thin plastic sheets
