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Jon - Ceramic Properties 2 - Coggle Diagram
Jon - Ceramic Properties 2
Heat Transfer by Radiation
Important in glasses, single crystals adn porosity
Transmission of phonons
Mean free path of phonons can be limited in 2 ways
Phonon absorbed by atom vibrations or electronic transitions
Phonons scattered by fine porosity
Thermal Expansion
Change in dimensions of material as temperature changes
Comes from the bonding of atoms and the atom spacing changing with temperature
Thermal Shock :fire:
Thermal Stresses occur in a component as a result of temperature difference between different regions of the sample
Peak stress occurs at the surface during cooling according to the equation:
:arrow_up:Thermal stress and thermal expansion coeff. when :arrow_up: Delta T
(materials perspective):arrow_down: delta T by :arrow_up: thermal conductivity
(design perspective) :arrow_down: delta T by changing system design or heat transfer conditions
Microstructure and presence of cracks will affect TS resistance, small amount of porosity or cracking :arrow_up: resistance
Creep
Deformation under constant stress as a function of temperature and time
Secondary (steady state) creep is used to predict creep life
Creep mechanisms:
-Dislocation movement
-Grain boundary sliding
-Grain boundary separations
Affected by:
T
\(\delta\)
Crystal structure
Microstructure
Composition
Stoichiometry
Environment
Temp and stress
:arrow_up: = :arrow_up: creep rate
Microstructure
Porosity = :arrow_up: creep rate
glassy grain boundary phase = :arrow_up: creep rate
