✅ C6.1.13-6.1.16 materials Flashcards
Ceramics are what
Hard, non-metallic materials
4 examples of ceramic materials
Brick, china, porcelain, glass
What do ceramics contain
Metals + non-metals, combined to form giant ionic lattices or giant covalent structures .
4 typical properties of ceramics
- high melting points
- hard and stiff, but brittle
- poor conductors of electricity + heat
Reactivity of ceramics and why?
The compounds in ceramics are mostly oxides, and this makes them unreactive
Glass
- how made?
- made by melting sand, then allowing it to cool
Glass
- structure?
3
- glass has an irregular giant structure without crystals, and is usually transparent
Other ceramics - how are they made
Other ceramics are produced differently (to glass)
- they are made by heating clay to very high temperatures
- tiny crystals form, joined together by glass
- china and porcelain are usually coated in a glaze and reheated
- the glaze forms a smooth, hard, and waterproof surface
Desirable qualities for the material chosen for an overhead electrical cable?
(4)
So what type of material might be suitable ?
- good conductor of electricity
- lightweight
- strong, so does not stretch or snap easily
- resist corrosion
- Metals are good conductors of electricity
PIC - TABLE 1
Which metal best as an electrical cable?
- Copper best electrical conductor, but tensile strength low = it is not as strong when stretched as aluminium/steel
- also has highest density, so a copper cable will be very heavy
- Aluminium chosen.
- although it is not as strong as steel, it is a better conductor and less dense than steel
Desirable property for a material chosen to be an insulator ?
What kind of material (2)?
- insulators must prevent an electric current passing from the cable to the pylon
- should be poor conductor of electricity
- e.g. ceramics/polymers, rather than metals
Compressive strength vs tensile strength
compressive strength- A measure of how well a material resists being crushed when a force is applied.
tensile strength- The tension a material can withstand without breaking.
Basically, squashed vs stretched
ADD PIC TABLE 2
Which material should be chosen for an insulator?
- poly(propene) is a tough, flexible polymer
- it has the poorest electrical resistance of the three materials, and its tensile strength is the lowest = it would snap easily when stretched
- it also has the lowest compressive strength, so it would squash easily
- porcelain has a lower resistance than glass, but it has a higher compressive strength
- from the data in table, porcelain would be the most suitable for insulators where cables are fixed on top of a structure
Tell me about composite materials
- what is it?
- its properties? - and an example
- A composite material is made from two or more materials combined together, each with different properties
- The properties of a composite material are different from those of the materials it contains
- for example, it may be stronger, less dense, or cheaper than its separate components alone
- Your clothes are likely to be made from __ materials.
- Cotton fabric is __ and __ to wear, but it is not very __.
- Your clothes are likely to be made from composite materials.
- Cotton fabric is lightweight and comfortable to wear, but it is not very hardwearing.
- Polyester-cotton is a __ material made by weaving __ thread with __ fibre, an __ p__.
- it is still __, but __ wearing than cotton and easier to __ and __
- Polyester-cotton is a composite material made by weaving cotton thread with polyester fibre, an artificial polymer.
- it is still comfortable, but harder wearing than cotton and easier to wash and dry
Many composite materials consist of
Fibres + what polymer
- and so…. A + B = ?
- many composite materials consist of fibres embedded in a polymer resin
- these fibres have low density and high tensile strength but are brittle, whereas resin is hardwearing but is not strong
- the composite material is lightweight, strong, and hard
Fibreglass
- consist of?
- used for? (3)
- fibres glass consist of glass fibres in a resin
- it is used for canoes, boats, surfboards
Carbon fibre
- consists of?
- price vs fibreglass
- uses (3)
- consists of carbon fibres in a resin
- more expensive than fibre glass
- sports equipment, racing cars, aircraft parts
HOW COMPOSITES USED IN BUILDINGS:
Concrete
- consists of?
- hows it made?
- Concrete is a composite material that consists of aggregate (small stones), sand and cement
- when water is added to this mixture, chemical reactions happen that bind the ingredients together
Concrete + steel - composite material
- Compressive + tensile strengths of concrete?
- strengths of steel?
- so we do what?
- concrete gas a high compressive strength - it resists being squashed, so it is useful for foundations
- however, it’s tensile strength is low - concrete beams crack and break if you put heavy loads on them
- on the other hand, steel has a high tensile strength —
— by embedding steel rods in concrete as it sets, you het a composite material called steel-reinfected concrete. — THIS HAS high compressive strength and high tensile strength
WOOD - strength (GRAIN)
+ solution
- wood is a natural material consisting of long fibres lying side by side to make a ‘grain’
- wood is stronger along that grain, than across
- Plywood is a composite material in which thin sheets of wood are glued together in layers
- the grain in each layer is set at right angles to the layer below — this produces a composite material that resists bending in both directions, so it is useful for floors and walls
Glass ceramics
Glass is made by melting __, then allowing the molten liquid to __ and __. Glass is transparent and hard, but it is __.
Glass is made by melting sand, then allowing the molten liquid to cool and solidify. Glass is transparent and hard, but it is brittle.
Clay ceramics
Clay ceramics include __, __ and __. They are made by heating __ to __ temperatures, which causes __ to form and __ together. Clay ceramics are often coated with a __, which hardens on __ to form a h__, s__, o__ and w__ layer.
Clay ceramics
Clay ceramics include brick, china and porcelain. They are made by heating clay to high temperatures, which causes crystals to form and join together. Clay ceramics are often coated with a glaze, which hardens on heating to form a hard, smooth, opaque and waterproof layer.
Metals
Metals are __ and __, so they can be bent into shape or made into wires without shattering. Unlike glass and clay ceramics, metals are good electrical conductors.
Metals are malleable and ductile, so they can be bent into shape or made into wires without shattering. Unlike glass and clay ceramics, metals are good electrical conductors.
Polymers are __ conductors of electricity and heat, but their other properties vary depending upon the __ polymer. For example, they can be transparent or __. They are often tough and f__, but some are hard and b__.
Different polymers have different properties. This means that different polymers have different u__.
Polymers are poor conductors of electricity and heat, but their other properties vary depending upon the particular polymer. For example, they can be transparent or opaque. They are often tough and flexible, but some are hard and brittle.
Different polymers have different properties. This means that different polymers have different uses.
PIC OF COMMON POLYMERS