C15.4 Glass, ceramics and composites Flashcards
What is glass mainly out of?
Sand - limestone = sodium carbonate
What is the most common form of glass?
Called soda - lime glass
How is glass made?
The raw materials heated to 1500 degrees
They melt and react form molten gas. As the glass turns into a solid - this particles do not form a regular pattern. It is as if the particles in the molten glass are frozen in place
How can different types of glass be made?
Can be made by varying the glass - making mixture or by incorporating other material into the glass
What is borosilicate glass used for?
Used for ovenware and test-tubes
What are some examples of ceramics?
Titles - bricks - bathroom sinks
What are the properties of ceramics?
Hard but generally brittle
Electrical insulators and resistant to chemical attack
Made by moulding wet clay into the desire shapes - and the heating them in a furnace to around 1000 degrees
What does clay contain?
Compounds of metals such as aluminium and pottasium - and non-metals such as silicon and oxygen
What type of bonding is present in Ceramics?
Ionic and covalent bonding
How are ions and atoms arranged in ceramics?
Arranged in a giant structure that form layers
What happens when the clay is wet?
Water molecules get between the layers of clay and make it slimy (as on a potter’s wheel)
What happens when the clay is fired up in a furnance?
Water is driven out and strong bonds form between the layers in the giant structure - changing the properties dramatically
What happens if there is a high temperature in the furnace?
The higher the temperature inside the kiln or furnace - the harder the ceramic formed
Why are ceramics brittle?
Because a sharp blow can distort layers in their structure so that ions with like charges are adjacent and repel each other away - cracking the ceramic object
What is a composite made up of?
2 materials - making a product with improved properties for a particular use. With one material acting as a binder for the other material - improving a desirable property that neither of the original materials could offer alone
What is reinforcement?
One material surrounding and binding together fibres or fragments of the other material
What are the properties of composite glass-ceramic?
Hard and very tough - No longer brittle as the glass melts between the crystals in the ceramics - so any cracks cannot spread through the whole structure
Why can a polymer layer be added to a materials surface?
Makes the surface waterproof - harder - stronger
How can the properties of concrete can be improved?
By reinforcing it with steel rods or mesh
What is the compressive strength?
A measure of how well a material resists being crushed when a force is applied
What is the tensile strength?
The tension a material can withstand without breaking
How can concrete be made?
From cement - stand and gravel mixed with water and left to set
Concrete is a very hard composite and is very strong in compression
How can concrete be made more resistant?
Can be made more resistant to bending forces by setting it around a matrix of steel rods - forming reinforced steel
