Test 3. Chapter 13 Flashcards
Properties of ceramics:
- ________Tm
- _____ductility; ______moduli and creep resist
- Large Tm for ceramics.
- - Small ductility; large moduli & creep resist.
what are some applications for ceramics?
– High T, wear resistant, novel uses from charge neutrality.
what are some fabrication for ceramics?
- some glasses can be easily formed
- - other ceramics can not be formed or cast.
what are some applications of ceramics?
refractories
die blanks
advanced ceramics
application: refractories
Need a material to use in high temperature furnaces.
• Consider the Silica (SiO2) - Alumina (Al2O3) system.
• Phase diagram shows:
mullite, alumina, and crystobalite as candidate refractories
what does the phase diagram show for candidate refactories of ceramics?
mullite, alumina, crystobalite
die blanks need _____________ resistant properties
wear
die surface
– 4 mm polycrystalline diamond
particles that are sintered onto a
cemented tungsten carbide
substrate.
– polycrystalline diamond helps control
fracture and gives uniform hardness
in all directions.
for heat engines what is the advantages and disadvantages for advanced ceramics
• Advantages: – Run at higher temperature – Excellent wear & corrosion resistance – Low frictional losses – Ability to operate without a cooling system – Low density
Disadvantages: – Brittle – Too easy to have voidsweaken the engine – Difficult to machine
appication as ceramic armor. What are possible materials used and why?
- Al2O3, B4C, SiC & TiB2
– Extremely hard materials
• shatter the incoming projectile
• energy absorbent material underneath
Glass properties the graph measures
specific volume (1/p) vs temperature (T)
Crystalline materials
- crystallize at melting temp, Tm
- have abrupt change in spec.
vol. at Tm
- have abrupt change in spec.
glasses
– do not crystallize
– change in slope in spec. vol. curve at
glass transition temperature, Tg
– transparent
- no crystals to scatter light
