Ag. Haerle et Ra. Haber, EXPERIMENTAL EVALUATION OF A NEW FLOCCULATION-FILTRATION MODEL FOR CERAMIC SHAPE FORMING PROCESSES, Journal of the American Ceramic Society, 79(9), 1996, pp. 2385-2396
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.