OneNote Test 2 Flashcards
For monolithic, what do we observe with microstructure as a result of sintering?
- shrinkage
- grains
- residual porosity 0% so density = 100% theoretical
For porous, what do we observe with microstructure as a result of sintering?
- developed grains around the porogens (struts)
- residual porosity is 0% around the struts
- keep the introduced porosity, but decrease of the porogen pore size
- shrinkage, but less than monolithic
For lattice, what do we observe with microstructure as a result of sintering?
- lower shrinkage compared to monolithic
For composites, what do we observe with microstructure as a result of sintering?
- densify together with the 2nd phase monolithic
For coatings, what do we observe with microstructure as a result of sintering?
- want residual porosity close to 0
- no delamination
- good CTE match between the substrate and the coating
What are the important things to check after the formation of the green body? How do you measure these?
- correct shape/tolerances
- visual inspection and dimensions
- green density
- Archimedes /pycnometry weight and dimensions
- particle size / surface defects/ flaws
- SEM and microscopy
- purity composition/phase
- XRD
- additives and pores
- DSC-TG
What do you need to check for and how after Drying?
- no-cracks
- visual inspection & SEM
- green density
- temperature and time profile (weight change w temp)
- microstructure flaws
**don’t need to measure purity unless there’s something with oxygen
What do you need to check after Burn-out?
- purity and characterization
- XRD/EDS/XRF
- burn-out organics
- weight change
- composition
- FTIR
- microstructure
- dimensions/shape
- caliper/ optical measurements
- maybe density
What do you want to check for after sintering?
- shrinkage -> digital calipers, dilatometer
- density -> archimedes
- microstructure (homogeneity, grain sizes, porosity) -> SEM w/EDS
- mechanical & specific properties -> 4-point bending and dilometer (CTE)
- composition -> XRD
- dimensions/shape -> digital calipers
What is cold sintering? Generally, how does it work? What is an advantage? What is an example (and its application)?
An energy efficient way to densify ceramics <400C as opposed to >1000C
Liquid is added to lower activation energy and solid-state diffusion occurs
Advantage: lower temp of sintering
Example: Barium Titanate (BT)
- good electrical properties
- Gypsum is another (used for construction)
What are shape memory ceramics? Generally, how do they work? What is an advantage? What is an example (and its application)?
stimulus-responsive intelligent materials
austenite state -> martensite transformation -> returns to normal
Advantage: higher strength & operating temps
Example: Zirconia
- energy harvesting
What are bioinspired ceramics? Generally, how do they work? What is an advantage? What is an example (and its application)?
Ceramics designed to mimic naturally occurring structures
they’re synthetic
Advantage: Mechanical integrity (can help w crack propagation)
Example: PcBN (polycrystalline boron) nitride
- military, aerospace uses
What are high entropy ceramics? What is an advantage? What is an example (and its application)?
ceramics w/ a presence of at least 5 elements w/ a 5-35% molar ratio in composition
combine all the properties to be superior
example: High entropy oxides (MgCoNiCuZn)
- Li-ion battery anodes
- high life cycle
