Optimization of the gelcasting of a silicon nitride formulation

An optimum gelcasting condition for a silicon nitride formulation was determined using the Taguchi statistical method. An L{sub 8}(4{sup 1} {times} 2{sup 4}) design, in which the effects of one factor at four levels and four factors at two levels were evaluated in only eight experiments, was used. The factors at two levels were: the total monomer concentration, the monomer/crosslinker ratio, the initiator concentration, and the initiator/catalyst ratio; the factor at four levels was the initiator concentration per mass of the slip. The primary criterion used to determine optimum design was the green strength of the dried part, although three other parameters were measured: initial slip viscosity, time for the slip viscosity to reach 300 mPa.s. at 25 C, and time for the slip to gel at 50 C. The optimum gelcasting conditions from the designed experiments predicted 80% increase in green strength (4.3 MPa versus 2.4 MPa, the initial value). The confirmation runs showed only a 60% increase (3.8 MPa)