questions oral exam

1. MIlling Bauxite

2. Solution in NaOH

3. Filtration

4. Filtratre cooled down to allow precipitation of Al(OH)3 and Na, Na removed

5. Calcination heat treatment at 1000-1200°c transforming into al2o3 & water

6. repetition until desired purity

• Presence of liquid

  • one component needs to melt

• solid solubility in the liquid

  • possible mass transport of solid through liquid

• wettability

  • for possible recombination and creation of new matrix

The spontanious change in polarisation with an externally applied electric field

tape casting: plasticizer (doctors knife plastically (!) deforms the slurry)

slip casting: no plasticizer

• base chemical ZrSiO4

• Alcoxide Demixing

  • reaction with NaOH and removal of water

  • precipitation and removal of Natrium and calcination

• Plasma route

  • seperation of ZrO2 and SiO2 via plasma (ZrO2 solidifies faster)

• filling and plastic deformability

  • better flow properties and better shapeable due to softness

• methods:

  • spray drying (use of suspension, blow against airflow)

  • direct granulation (use of suspension in tumbeling drum)

• higher mass transfer with liquid

• capilllary tension which increases penetration of vacancies

  • wettability important

binder:

• good flow properties

• maintain mechanical stability

• no reaction with powder

• easily removeable (!)

major binder: provides flow properties and mech stability

minor binder: removed for providing space

A= geometric factor

M= grain boundary mobiity (diffusion dependant)

gamma= surface energy

t= time