Abstract
Spontaneous infiltration of molten metal alloys into porous, particulate ceramic preforms is becoming a popular process for producing ceramic-metal composites. Due to the non-cylindrical shape of pores, spontaneous infiltration typically requires a critical wettability corresponding to contact angles much less than 90°, depending on particle packing and other particle characteristics. Even when spontaneous infiltration occurs, however, it may not be complete in real preforms, which contain non-uniform porosity distributions and packing defects. Indeed, model experiments on spontaneous infiltration of preforms containing large spherical pores indicate that large pores are not filled due to non-cylindrical geometry effects. Numerical modeling using Surface Evolver shows that pressures on the order of only 0.5 atm are required to force a liquid having θ=30° and γ IV =1 N/m to engulf the surface and fill large pores bound by 5 μm particles. The calculations are in good agreement with the experimental result that 1 atm pressure applied after vacuum infiltration was sufficient to fill the large pores.
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