Soda Lime glasses Flashcards
1
Q
What characterizes soda lime glasses?
A
~ additions of CaO to Na2O-SiO2 glass
2
Q
What effects does adding CaO to Na2O-SiO2 have?
A
~ increased viscosity and chemical durability
3
Q
What happens chemically in soda lime glasses?
A
~ Ca2+ is more polarizing to O2- (more covalent) and charge compensates 2 NBO’s
~ the Ca2+~O2- bond is harder to shear than the Na+~O2- bond
~ electrical conductivity decreases as Ca2+ is LESS MOBILE and blocks migration of Na+
4
Q
What are the effects of Al2O3 additions to soda lime glass?
A
~ increase durability
~ reduce NBO’s (increase index of refraction) by reverting the role of Na+ to CHARGE COMPENSATOR for AlO4- tetrahedra