Glass

GLASS AND CERAMICS Name of glass Fused glass

Properties •

• • •

•

Soda lime glass

•

• •

• • Borosilicate glass

•

•

• • •

Chemical composition

Uses

Very high softening point ( 1700 ºC ) hence highly heat – resistant Transparent to ultraviolet and infrared light Difficult to be made into different shapes Does not crack when temperature changes ( very low thermal expansion coefficient ) Very resistant to chemical reactions

SiO2 (99%)

Telescope mirrors,

B2O3 (1 %)

Lenses, optical fibres and laboratory glass wares

Low softening point ( 700 ºC ) hence does not withstand heating Breaks easily Cracks easily with sudden temperature changes ( high thermal coefficient of expansion ) Less resistant to chemical reactions Easy to make into different shapes Quite high softening point ( 800 ºC ) hence it is heat – resistant Does not crack easily with sudden change in temperature Transparent to ultraviolet light More resistant to chemical reactions Does not break easily

SiO2 (70%)

Bottles, window – panes, light bulbs, mirrors, flat glass, glass – plates and bowls. ( The most widely used type glass)

Na2O (15%) CaO (10%) Others (5%)

SiO2 (80%) B2O3 (15%) Na2O (3%) AI2O3 (1%)

Laboratory apparatus, cooking utensils, electrical – tubes and glass pipelines.

Lead glass

• • • •

Low softening point ( 600 ºC ) High density High refractive index Reflects light rays and appears sparkling

SiO2 (55%) PbO (30%)

Decorative items, crystal glasswares, lens, prisms and chandeliers

K2O (10%) Na2O (3%) AI2O3 (2%)

THE DIFFERENT TYPES, COMPOSITION, PROPERTIES AND USES OF GLASS