When was the chrystal palace built?
How large was chrystal palace?
1,848 ft long and 408 ft wide
What are the key properties of glass?
- High stiffness (young’s modulus)
- Brittle (low toughness, associated with catastrophic failure)
- Reasonable strength in compression
- Relatively low strength in tension but highly variable
- Hard, but easily damaged
- Fractures to give sharp surfaces
- Excellent corrosion resistance
- Low leaching of contaminants
What is the definition of a glass?
An inorganic product of fusion (melting) which has cooled to a rigid condition without chrystallisation
What are the key characteristics of glass?
- Non-chrystalline amorphous material with no longer range repeated order
- Typically produced from the liquid state by continuous cooling
- Exhibit a glass transition temperature
- Can be formed from certain liquids provided cooling rate is sufficiently high
What is the basic building block for most commercial glasses?
The SIO4 tetrahedron (silica tetrahedron
What type of bonding is Si-O
What is a the microstructre of glass like?
Short range order
Long range disorder
Does glass contain dislocations?
What structure does glass have?
the same amorphous strucure of a liquid phase
What happens to viscosity as temperature is reduced?
Why does glass cooling not chrystallise?
The material becomes solid before it can chrystallise (Slow vs abrupt cooling)
How many Si share each O in glass?
What happens when you add sodium to glass mixture
Disrupts the sturcture
Maintaind charge neutrality
What terms describe Si and Na?
Si is a glass former
Na is a network modifier
Name some of the raw materials used in the maufacture of glass
Silica sand (glass sand) Feldspathic sand (alumina sand) Sodium Carbonate (soda ash) Calcium carbonate (limestone) Magnesium Carbonite (dolomite) Feldspar Nepheline syenite Aplite Sandspar
What is the composition of commercial glass?
70-74% silica 12-16% sodium oxide 5-11% Calcium oxide 1-3% magnesium oxide 1-3% aluminium oxide
Name some types of special glass
Vitreous silica Alumina-silicate glass Alkali-barium silicate glass Technical glass Glass ceramic Optical glass Sealing glass
What do many special glasses contain?
Polymer layers and special coatings
What are the 5 main constituents of glass?
- Glass forming oxides
- Fluxes that reduce melting temperature
- property modifiers
- colouring (tinting) agents
- Processing agents
Give an example of a glass forming oxide
SiO2, B2O3, P2O5
Give an example of a flux
Na2O, PbO, K2O, Li2O
Give an example of a property modifier
Give an example of a colouring agent
Oxides with 3d, 4f electron structures; minor additives (<1 wt%)
Give an example of a processing agent
As-oxide, Sb-oxides, NaNO3, NaCL, fluorides, sulphates
What do property modifiers do?
Tailor chemical durability, expansion, viscosity, etc.
What does a processing agents do?
Help promote bubble removal
Minor effect on bulk properties
What is the microstructure of glass like?
Homogeneous with no interfaces to scatter light
No potential for dislocations to move
Surface cracks and defects have a high stress concentrating effect
Tensile strenght follows the same rules as ceramics
Obeys a hookean response to stress
What is the equation for K_1c of glass?
K_1c = sqrt(2Ey_i)
E = youngs modulus y_i = the fracture surface energy
What is the usual value for K_1c for glass
0.56 MPa m^1/2
What can be done to reduce surface flaws?