Fabrication of Ceramic Matrix Composites by Slurry Infiltration

Dr. Dmitri Kopeliovich

Slurry is a dispersion of ceramic particles in a liquid carrier, which may also contain additives such as binders and wetting agents.

Slurry Infiltration method of fabrication of Ceramic Matrix Composites utilizes a slurry percolating into a porous reinforcing preform. The infiltration process is driven by the capillary forces.
After the infiltration process has completed, the preform is dried and hot pressed forming a ceramic matrix composite.

• Ceramic matrices produced by Slurry Infiltration
• Slurry Infiltration process
• Advantages and disadvantages of Slurry Infiltration

Slurry Infiltration is used for fabrication of ceramic, ceramic-glass and glass matrices:

• Alumina (AL₂O₃);
• Silica (SiO₂);
• Glass;
• Mullite (3AL₂O₃*2SiO₂);
• Silicon carbide (SiC);
• Silicon nitride (Si₃N₄).

The method of fabrication of ceramic matrix composites by Slurry Infiltration technique is similar to Sol-Gel Infiltration. However Slurry Infiltration produces denser structure with smaller shrinkage during processing due to higher content of solids.

Pressure or vacuum assisted Slurry Infiltration allows further increase of the density of the resulting ceramic composite.

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• Slurry infiltration. The reinforcing fibers passe through a slurry, which penetrates into the porous structure of the reinforcing phase. The driving force of the infiltration is capillary effect but the process may be enhanced by vacuum or pressure.
• Lay-up. The prepreg (infiltrated fibers) is wound onto a mandrel. Then it is dried, cut and laid-up. After drying they are cut and laid-up on a tooling (mold).
• Hot pressing. Hot pressing (sintering, densification) is performed at high temperature and increased pressure, which enhance the diffusion of the ceramic material between the particles incorporated into the fibers structure. The particles consolidate resulting in a low porosity densified composite.

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Advantages of Slurry Infiltration:\

• Low porosity;
• Good mechanical properties.

Disadvantages of Slurry Infiltration:

• The reinforcing fibers may be damaged by the high pressure applied in the hot pressing stage.
• Hot pressing operation requires relatively expensive equipment;
• Relatively small and simple parts may be fabricated.

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• Ceramic Matrix Composites (introduction)
• Classification of infiltration methods of ceramic composites fabrication
• Reinforcing fibers for ceramic composites
• Interphases
• Fabrication of Ceramic Matrix Composites by Polymer Infiltration and Pyrolysis (PIP)
• Fabrication of Ceramic Matrix Composites by Chemical Vapor Infiltration (CVI)
• Fabrication of Ceramic Matrix Composites by Liquid phase Infiltration
• Fabrication of Ceramic Matrix Composites by Liquid Silicon Infiltration (LSI)
• Fabrication of Ceramic Matrix Composites by Direct Oxidation Process
• Fabrication of Ceramic Matrix Composites by Sol-gel process
• Self-lubricating ceramic composites
• Carbon-Carbon Composites

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