Ceramics and Inorganic Glasses Flashcards
Ceramics
Covalently or ionically bonded compounds of a metal and a nonmetal
oxides, carbides, nitrides of various metals
Typical engineering ceramics
SiO2
sand, window glass in amorphous form, quartz in crystalline form
SiC
Moissanite in crystalline form
Si3N4
Al2O3
Corundum or alumina, sapphire/ruby in crystalline form
Garnet
Typical Traditional Ceramics
Stone
granite, marble
Cement
Bricks
Porcelain
Typical properties of ceramics
Very high melting temperature
Very high creep resistance
Very high oxidation resistance
Very high modulus of elasticity
Very high hardness and very high strength in compression
Brittle
Compression strength = 10x tensile strength
Low coefficient of thermal energy
Intermediate density
Low electrical and thermal conductivity
Typical applications of ceramics
Thermal insulators
Electrical insulators
Crucibles and molds for casting and handling molten metal
Abrasives
Cutting tool inserts
Processing ceramics
Processing done mostly in powder form:
- Ceramics have too high a melting temperature to melt/cast
- Ceramics are too hard and brittle to cut
- Ceramics are too brittle to form/forge
Glasses
When a material is cooled from liquid to solid state, will crystallize if cooled slowly and become an amorphous solid if cooled quickly
amorphous material will always by less dense and nearly always be less stiff and less hard than crystalline versions of a material
Strain point
Viscosity which is high enough so that a material essentially acts as a solid.
At temperatures where the viscosity is more than this, the material shows no appreciable deformation under its own weight over time
Annealing Temperature
Temperature at which the viscosity is low enough for the microscopic rearrangement necessary to relieve residual stresses, but not so low that the material deforms visibly
Working range
Range of temperatures/viscosities at which the glass flows freely
Sheet glass is manufactured in the melting range
