Ceramics Flashcards
Composition of Ceramics
Compounds formed between metallic and nonmetallic elements
Natural ceramic minerals
Contain oxygen ( Al2O3, ZrO2)
7 general qualities of ceramics
- Extreme hardness good wear resistance
– Ceramic coatings for cutting tools, punches, dies
* A few microns of TiN coating extends tool life to 7 times
longer - Extreme brittleness low impact strength
- High temperature resistance high melting point
- Low coefficient of thermal expansion good thermal
stability, dimensional stability, and thermal shock resistance - Low electrical and thermal conductivity good electrical &
thermal insulator - High corrosion/chemical resistance
- High porosity and low density except for advance ceramics
Cutting tool materials
Cemented Carbide: WC + Co
Cermet: TiC, TiN
Most common: TiN coated WC
Mechanical Characteristics of Ceramics
Excellent compression strength
Low tensile strength
High servicable temp
Density can be adjusted thru manufacturing processes
Two types of Ceramics
Traditional: Non-technical
Advanced: Technical, Engineering, Structural
Traditional Ceramics
Silicate Ceramics
Mainly clay based, consumer products
Advanced Ceramics
Non-Silicate Ceramics
High density
High purity
Small grit size
Mostly Man-made
Main Silicates
SiO2 (Quartz)
KAlSi3O8
Non-Silicates
Oxide: Al2O3, ZrO2
Carbide: SiC, WC
Nitride: Si3N4, TiN
Applications of Ceramics
Electrical (Resistors, Capacitors, Piezoelectric Sensors)
Cutting Tools
Abrasives
Flooring
Building Materials
Carbon/Graphite
Structural Shapes
Glasses
Refractories
Traditional Ceramic Applications
Clay products
Refractories
Glasses
Cements
Abrasives
Trad. Raw Materials
Clay (silicates)
Size of clays
Minerals with particle size <= 2 micro meters
Clay Comp.
Silicon
oxygen
one or more metals
Earth’s crust composition of silicates
95% silicates
+60% quartz (SiO2) and feldspar (KAlSi3O8)
ManuProc of Tradition Ceramics
1) Powder prep
2) Forming (Dry and Wet Systems)
3) Drying (Wet system only)
4) Sintering ( Firing/densification)
5) Glazing (optional)
- Comminution (Powder Prep)
minerals crushed and grounded into powder
Rock crusher (Larger particles)
Ball Mill (Fine particles)
- Forming
Powders mixed with water or organic binders and formed into shape
Produces Green Compacts
Powder injection molding
ceramic powder containing large amounts of organic binder (no water) is injected into a mold
Slip Casting
using water absorption plaster (plaster of paris)
molds with ceramic slurry
Extrusion
using wet paste or clay
Powder Pressing Methods
Uniaxial Pressing - Pressing powder in one direction
Cold Isostatic pressing (CIP) - powder enclosed in a rubber
envelope and pressed by fluid or gas from all directions
Drying
(Wet system only)
Large dimensional change
controled temp and humidity
Machining after drying
