Processing of CMCs

Ceramics are commonly prepared using the following technologies:

• Sintering, Slip Casting, Chemical Vapour Deposition (CVD), Lanxide and Chemical Reaction
  
  
• Sintering
  • The ceramic powder is mixed with binder & whiskers etc and then shaped under high pressure.
  • The temperature is elevated to improve the strength and burn off the binder.
    
    
• Slip Casting - slurry is prepared by dissolving material in water (PH control), cast in a preform and then heat is applied with or without pressure.
  
  
• Slurry infiltration: Nicalon fibre, Glass Matrix
  
  
• Chemical Vapour Deposition (CVD) - Carrier Gas + Gaseous Reactant in the deposition chamber to deposit coating in fibers eg. TiCl₄ + 2BCl₃ + 5H₂ = TiB₂ + 10 HCl
  
  
• Lanxide : Reaction of Molten metal and a Gas Al +air = Al₂O₃ , Al+N - AlN : Used for small parts
  
  
• In-situ Process : In the in-situ process, both fibre and the matrix are developed simultaneously. The examples below explains the concept.
  
  2AlN+B₂ O₃ = Al₂ O₃ + 2BN - least expensive exothermic like:
  4Al+3TiO₂ +3C=2Al₂ O₃ +3TiC