Ceramics

Why the casted objects shrink during drying?

because of water/solvent removal

How water is removed from the casted object during casting to non-porous (plastic) moulds?

The water is removed from the casted thanks to rotation of the mould

Characterization of tape casting

Tape casting has been used to produce thin layers of ceramics. The Tape Casting process involves the casting the slurry onto a flat moving carrier surface. The slurry usually consists of a ceramic powder with the appropriate additions of solvents plasticisers and binders.

Why the thin ceramic foil can be produced from the viscous suspension?

Selection of the suitable composition of the suspension assures its good fl uidity and obtainment of the thin homogenous layers with the uniform structure

Which parameter control viscosity of ceramic suspension?

Amount of Solvent

Give an example of application of thin ceramic foil in industry

Fuel cells, Structural ceramics, Medical electronics

Give the principle of gel casting of ceramic slurries

Gel casting – the process is a method of forming a ceramic powder by in-situ polymerisation. Slurry is mixed with monomer, and then polymerisation begins.

Explain the term “ceramic additive manufacturing”

Ceramic component directly from CAD file. Components are produced in successive layers with a laser that polymerizes a paste made of photosensitive resin and ceramic. Time saving, cost effective (without moulds)

54. Describe stages (3) of injection moulding of ceramic slurries

• Design of the feedstock (ceramic powder, binder) • Injection forming • Debinding

Main components of ceramic slurry for injection moulding

• Main polymer • Plasticizer • Lubricant • Surfactants

Describe ceramic components made via injection moulding (examples, application)

• Al2O3; ZrO2 – Nozzles • Si3N4, sialon - Fuel injection valves, parts of shafts, rotors, valves • SiC, ZrO2 Si3N4, sialon - Parts of the fuel pumps,

List methods (3) of ceramic powder compaction

Uniaxial, isostatic, vibrational

Advantages (3) of powder uniaxial pressing in comparison to other methods of shaping

High yield, Simple, No shrinkage during drying

Disadvantages (3) of the powder uniaxial pressing in comparison to other methods of shaping

Shape limitations, Height limitations, Density non-homogeneity

List stages (3) of the powder uniaxial pressing

powder --&rt; perforation --&rt; green body