EXPERIMENTAL EVALUATION OF A NEW FLOCCULATION-FILTRATION MODEL FOR CERAMIC SHAPE FORMING PROCESSES

The effect of suspension rheology on the casting mechanics of 37 vol% aqueous silicon carbide slips was examined, Slip viscosities of 180, 1 20, 90, and 58 mPa . s were evaluated, The 58 mPa . s slip was conside red to be fully deflocculated; the others were underdeflocculated to v arying degrees. The fully deflocculated slip cast according to parabol ic rate behavior, while the others cast at a faster than parabolic rat e, Deviations from parabolic rate behavior were correlated with a nonu niform cake structure observed through ultrasound and mercury porosime try measurements, The observed casting behavior was explained on the b asis of a suspension flocculation-filtration model. From rheological m easurements, it was found that flocculation of the SiC particles durin g casting in the underdeflocculated suspensions caused the local void volume within the forming cake to increase as a function of cake thick ness, The fully deflocculated slip was theologically stable, and there fore cast with a uniform microstructure.