Glass Flashcards
Structure of Glass
Amorphous
Is Glass in a meta-stable state?
Yes
What is Glass commonly made out of
Silicates
Properties of Glass (mechanical) (3)
Hard, Brittle, Perfectly elecastic
What does perfectly elastic mean
There is little or no plastic deformation
Glass Properties(Density)
Polymers- higher
metals- lower
Glass (compressive strength)
Surprisingly high
Tensile stregth
not great but stronger for anealed
Youngs modulus
medium
Thermal expansion
low
Why can you see through glass
Energy levels wide enough that visible light is not absorbed
Why is sio2 forming crystals when cooling bad?
because then its less see through
What effect do impurities have in glass
Make less transparent but nice colours
Why do we sometimes add impurities to glass
to disrupt the crystal order
How do we make sure glass is amorphous?
Impurities and Quenching(cooling really fast)
Why use a glass former
It readily forms an amorphous structure
Why use a modifier?
it encourages an amorphous structure
Why use a intermediates
used with modifiers to form a glass
Glass manufacture- pressing
Pressing hot glass into shape
Glass manufacture- Press and blow
pressing into shape and then blowing to expand shape
Glass Manufacture- Drawing
Get strings of the glass and they cool
GLass manufacture- rolling
Roll out then anneal
Glass manufacuture- floating on molten tin
helps keep it flat and cools quick
Glass tempering
Heat between softening and melting point then quickly cool to reduce stress
What is a glass ceramic?
Recrystalysed glass
Why are glass cermanics so good(2)
strong and low thermal expansion
How do you recrystalisze glass?
By heating it up so nucleation and crystals can grow
