Compositional Effects on the Chemorheological Properties and Forming Behavior of Aqueous Alumina-Poly(vinyl Alcohol) Gelcasting Suspensions

Abstract

Gelcasting suspensions were used as feedstock for solid free-form fabrication (SFF) of ceramic components. The influence of processing conditions (e.g., tip diameter, mixing rate, table speed, etc.) and suspension rheology on deposition behavior was investigated. Continuous printablity was achieved for tip diameters ranging from dt = 0.254 -- 1.370 mm for all mixing rates (Rmix 5 -- 300 rpm) and suspension compositions (i.e., fAl2O3 = 0.45, &phis;PVA = 0.275, [Ti] 0 -- 6.30 x 10--3 g Ti/ml) probed, where the minimum tip diameter for continuous printing was 0.203 mm. Printed lines were uniform with good edge definition. Line dimensions were independent of mixing rate for the given process conditions. The as-cast alumina volume fraction ( fAl2O3 ) depended on casting conditions and cross-linking agent concentration, where fAl2O3 decreased with increasing tip diameter and increased with increasing cross-linking agent concentration. Free-fomied Al2O3 components exhibited uniform particle packing and had minimal macro-defects (e.g., slumping or stair casing) and no detectable micro-defects (e.g., bubbles or cracking).