Effect of solid loading on properties of reaction bonded silicon carbide ceramics by gelcasting

Reaction bonded silicon carbide (SIC) ceramics were successfully fabricated by gelcasting using a new non-aqueous, low-toxicity gel system based on the polymerization of a phenol-formaldehyde resin and furfuryl alcohol. The effect of solid loading on the rheological properties of slurries, and the properties of green bodies and sintered ceramics, have been systematically investigated. The solid loading of a suspension able to meet the requirements of the casting process is as high as 70 wt%. The drying shrinkage and green strength of the SiC/polymer network green bodies decrease with solid loading ranging from 55 to 70 wt% because of the reduction of pre-mixed solutions. On the other hand the fracture toughness and bending strength of the sintered ceramics increase with increase in solid loading. The highest values of strength and toughness were observed at 378 ± 16 MPa and 4.22 ± 0.13 MPam1/2, respectively, for composites produced at a solid loading of 70 wt%.