• Improve: Toughness and Tensile strength
• Continuous fibers increase toughness more and have more desirable failure mode (they don't fracture suddenly), but are expensive.

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Glass Processing

• Amorphus structure
• Achieved by rapid cooling
• Liquid (T>T_m) > Supercooled Liquid > Glass(T<T_g)

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• Fine grained poly crystalline materials which are formed when glasses are heat treated in order to induce crystallization.
• 50-98% Crystalline structure
• Stronger than glass
• low coefficient of expansion

• Procedures:

1.  Mix ceramic powder w/ particle of whisker reinforcement
2. Press
3. Fire

Disadvantages:

-Inhomogenous mixture

-Damaged whiskers

CMC Processing: Continuous Fiber- Slurry Method

• used for glass and glass-ceramic

Processing CMC: Liquid State Processing

• Matrix Transfer Moulding

Process Limitations:

High viscosity and temperatures

Advantages:

Tube production Capabilities

Process:

1. Insert SiC wound mandrel
2. Insert glass plug
3. Plunge
4. Heat to melt
5. Eject

Processing CMC: Sol-gel

Sol- a dispersion of particles less than 100nm, which are obtained by precipitation via a chemical reaction

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Gel- same as sol except with less liquid and is thus more viscous

• Used for particle and whisker reinforcement
• Still experimental
• Provides good mixing

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• The formation of a ceramic matrix by the reaction between a molten metal and a gas.
• Grows from the surface of the metal
• The fibers and particles must not react w/ the gas

• Common production is slurry method
• Up to 25% whisker content[image]

• contains 10-20% ZrO₂
• Structure tranforms from tetragonal (t) to monolithic upon cooling (m)
• Not good in liquids
• Microcrack toughening:
  • Occurs under normal cooling
  • Increased toughness but decreases strength
• Transformation Toughening:
  • metastable tetrogonal particles transform to monoclinic
  • t>m suppressed by stabalizing oxide (Y₂O₃)
  • Increases both toughness and strength