Minimum Time Heating Cycles for Diffusion‐Controlled Binder Removal from Ceramic Green Bodies

Abstract

An algorithm based on variational calculus has been developed to predict the minimum time heating cycle ( MTHC ) for thermal binder removal from a ceramic green body when diffusion, as described by the free volume theory, is the governing mass transport mechanism. The algorithm uses a previously derived analytic solution for the diffusant concentration, which was obtained from the governing reaction–diffusion differential equation. Either a constraint on diffusant concentration or on the equilibrium pressure of diffusant is used to predict the MTHC for both a stationary binder model and a shrinking core binder model. For these four cases, the dependence of the MTHC has been determined on a number of model parameters, including the threshold concentration or pressure, the body size, and the reaction order of the binder degradation kinetics. The algorithm determines two important aspects of the MTHC , namely, the starting temperature of the heating cycle and how temperature varies with time during the cycle. The duration and shape of the temperature‐versus‐time heating schedule, whether increasing, decreasing, or almost constant, depends sensitively on parameters in the model.