Investigating the Rheological Behavior of Silicon Carbide Gel Casting Suspensions and its Effect on the Silicon Carbide Bodies

In this paper, the rheological behavior of SiC suspensions, fabricated via gel-casting method, and the influence of this behavior on the mechanical properties of the sintered samples were studied. To prepare castable and stable SiC suspensions, the rheological behaviour of the suspensions was characterized and optimized. To this aim tetramethylammonium hydroxide as dispersant, acrylamide as monomer, methylenebisacrylamide as cross linker, ammonium persulfate as initiator and tetramethylethylenediamine as catalyst were used. The results indicated that for obtaining stable SiC suspensions with suitable viscosity, 0.4 wt% dispersant of tetramethylammonium hydroxide, the pH of 10.5 and mixing time of 24 h were required. It should be noted that this suspension was electrosterically stable and the presence of the monomer acrylamide decreased the viscosity. The results showed that in the optimal ratio of methylenebisacrylamide cross linker to acrylamide monomer the highest strength was obtained. The flexural strength of the gel cast bodies was 231 MPa.