Reasons for properties-
Electrons are locked to ions or atoms
None are free to move, strong bonds, hard to stretch
So atoms or ions can't slip
Locks atoms in place
Properties vary depending on the metal used with the ceramic.
Ceramics that have a high % of ionic orc ovalent bond have higher melting points.
Aluminium oxide- Most common
Zirconium Oxide- Highest fracture toughness
Fused Silica- Excellent thermal insulator
Boran Carbide- Hardest material after diamond.
Ceramics can be mde much stronger
More thermally efficient- protects against fire
Tenisle strength of pottery over Alumina ceramics- much higher
Ceramics have very high compressive stength- harder than most steels and alloys- only thing harder is diamond.
10 times stronger than steel
Uses in Aero space
As insulation to protect againts fire.
Used by the military as armour plating
Jet engine components.
Future-- Air craft fusalages, turbine blades in jet engines.
Can repace heavier structural componants
less fuel uses=cheaper
Scientists have discovered that by carefully constructing nanoscale struts and joints, materials can recover after being crushed like a sponge.
Makes materials very light and strong can float through the air like a feather as they are made mostly of air.
In conventional ceramics are strong but heavy so can be used where weight matters. weight, stength and density affect eachother. Brittle- when put under pressure they shatter like glass.
At a nanoscale the rules do not apply- structural properties of ceramics become less tied to the weight.
How are they made?
Creates the structure out of a honey like polymer.
Lattice polymer is coated in a ceramic such as Alumina Al2O3.
The shape is than etched out in a strong acid to remove polymer.
The ceramic is moulded to the desired shape and bonded to other materials sometimes by vaccuming.
Possible to control of the material fails by controlling the thickness- when walls are thick ceramics shatter when put under pressure.
Trusses with thinner walls just 10 nanometers thick bukle and return to their original shape.
Key properties are high heat capacity
Low Thermal coefficient which measures how the object changes in size when heated.
Low thermal conductivity.