6.1b Alloys Onwards Flashcards
What are alloys
Steel
What is tensile strength
A mixture of two or more elements can eithe r e bith metal like bronze brass or metal non entlang like steel which is iron and carbon
Steel thus has mixture of both , high tensile but also ductile . Stronger than iron, resist corrosion etc
3) how string a metal is when stretched ; maximum a material can resist when being stretched before dying
Solder
Made from
Melting point
What this means (advantages of solder)
Made from tin copper (or lead tin)
- has low melting point of 227 (less than both tin and copper 1085)
- MAKES IT USEFUL FOR JOINING electrical components without damaging them as not too hot
- solidifies gradually as it cools down , so hot solder liquid can flow into gaps between components and then solidify which is more EASY TO WORK AROUND
-obviously cinducts electricity so can rejoin components in circuit
Brass and bronze
What are they bith made from
What Properties do they now bith habe they wouldn’t before
What is brass used for
Bronze used for?
Brass = copper and zinc Bronze = copper and tin
Brass (and bronze) is harder than copper and zinc indicfulsly because the different sized atoms joined means it is harder for layers of copper atoms to slide over each other (as zinc atoms interfere). This makes layers of atoms not slide other Esch other when stretched = very hard
+Brass conduct electricity like copper, but stronger
+ brass and bronze both resist corrosion and stronger and harder
Brass used for musical instrument and electrical pins in plugs
Bronze used for propeller in ship (resist corrosion ) snd bells and used in art
What is difference between rusting snd corrosion?
How silver corrode
Rusting
What doesn’t corrode
Corrosiom is a restcion if a metal with substance in the surroundings. Silver can corrode in the Presence of hydrogen sulfide gas turning black , any metal can be oxides and corrode but
Rusting is when IRON AND STEEL CORRODE (still corrosion tho) (only iron produce rust , other metals still corrode)
Unrrsctive metals like gold platinum don’t corrode
Equation for rusting , what type of reaction is it ?
What cinditons must iron be in for rust to happen (remember it’s just corrosion again…)
What eventually happens to iron
Redox (iron gains and oxygen loses electrons)
Iron + oxygen + water = HYDRATED iron (III) oxide
Remember it only rusts in presence of BOTH oxygen and water
Rust is ten iron oxide orange brown .
It easily flakes away from surface of object opposing fresh underneath which rust again.
Rusting can continue until it completely corrode away
How to do rust experiment to prove water and oxygen needed?
What increase rate of rusting?
Set up three boiling tubes
1) has anhydrous calcium chloride which absorbs vapour keeping dry. Bung too . No air and water = no rust
2) has full water but bung so no oxygen. water but no air= no rust
3) has water half filled and oxygen . Water + oxygen = rust
Salt, so in ships it corrode quickly because salt in seawater …
What are 4 ways of preventing rusting?
How do basic first two work
Problem with paint ?
Where both used in
Paining Costing with oil, grease or plastic Tin plating Zinc plating (galvanise ) (Also just huge blocks of sacrificial )
Painting and costing stops air and water reaching the metal in the first place . Painting is colourful and good for small objects , while for moving parts oil and grease more better.
But if pain gets broken corrosion can happen UNDER the metal. Paint flakes away and fresh metal exposed until everything corrodes…
Sacrifice proteticon of huge blocks?
Why has to be more reactive
Where used
Involves metal more reactive then iron like magnesium or zinc, which sacrifices itself by cording first and protecting the iron.
Has to be more reactive metal so it readily loses electrons and oxides in PREFERENCE to iron…
Useful for when painting is difficult
Used in ships, where zinc magnesium blocks are bolted onto hulls corroding fist. Have to be replaced eventually .
How does metal plating of tin and galvanising zinc work?
What difference between tin and zinc (galvanise )
Zinc galvanising involves dipping object into molten zinc, which create a thin layer of zinc around iron
= acts as barrier stopping water and air from reaching iron.
= sacrificial metal so object is protected EVEN if zinc layer damaged (because will more readily lose electrons and oxide first as more reactive)
However while tin Platin also involves dipping into molten tin and acts as barrier to oxygen and water, if tin breaks (as tin is LESS reactive then iron), iron will act as a sacrifice layer for tin, reverse intuitive 😭
Buckets fences all galvanised…
What are ceramics
What types are there
What Properties do they have
Hard non metal,if materials such as BRICK, CHINA and PORCELAIN, and GLASS,
- they either form giant joint/ covalent structures so have their typical properties =
1) high melting points
2) hard and stiff , but BRITTLE (remember enough pressure and all covalent binds break
3) poor conductors if electricity and heat
As mostly oxides they are
4) unresctive too
How are some ceramics made
Glass (structure of glass?)
Bricks from clay
Porcelain China from clay
Glass= melting sand and allowing it to cool and solids (mouldable when hot not when cold). Glass has irregular giant structure without crystals and is transparent
Bricks etc made from clay= heat clay to high temps , tiny crystals form, joined together by glass
Then after this for China and porcelain they are glazed and reheated, forming smooth hard and waterproof surface
Composite materials
Cotton
Fibres in Resin?
Fibreglass, carbin fibre uses
Composite material made firm two or more materials combined together, each with different properties (as result resultant will have different properties to ones that msde it)
Polyester cottton:
- cotton by itself is comfortable but not durable
- polyester fibre weaves with cotton = polyester cotton which is comfortable AND HARDER WEARING, easier to wash and dry
- Most composite is fibres embedded in polymer RESIN.
- fibres los density but high tensile strength , whereas composite material is harder with but nit string.
- resin ploy,er + fibre = lightweight , string and hard wearing - Fibreglass = glass fibres in resin= canoes boats etc
- Carbon fibre = carbin fibres in resin = sport equipment race cars etc
Steel reinforced concrete ? (Composite metal)
Qualities of bith by own
Also how concrete made
Why good for foundations
Concrete already composite = aggregate (small stones, sand and cement
- water added then they combine and has HIGH CIMPRESSIVE STRENGTH, so good for foundation (resist squashed )
- HOWEVER tensile strength low
- steel has high tensile strength
THUS. Steel + concrete= steel reinforced concrete
= High compressive (from concrete) and high tensile (from steel)
Put steel rods in
Wood composite material (plywood)
Why Kevlar based composited good ?(what is Kevlar)
Wood = natural with long fibres parallel to each other making “grain”
- wood is stringer ALONG grain rather than across (horizontal better).
- thus PLYWOOD= wood glued at 90 ° allowing it to resist effectively in both directions = stringer
= thus floors and walls
2, Kevlar is a polymer and Kevlar composted Give strength without weight do =tennis racquets and cycling helmets for example
How are each material (polymers, ceramics, metals and composites) good for a job
Polymer= mouldable, cheap, less dense so used when low mass needed, but degrade so not long lasting
Ceramics = insulators, brittle and stiff but STRONG and last long . Don’t corrode, so we use glass as windy instead of plastic
Metal= conductors, malleable and less brittle. Can corrode but if msde resistant minor
Composted= different functions based on resin and material.
- chacrtedisitcs can be whatever but EXPENSIVE
