Is sintering enhanced under non-isothermal conditions?

Several authors have claimed that the sintering rate of a powder compact is enhanced during a heating ramp. Their experimental results show that: (a) at any temperature the shrinking rate increases with heating rate; (b) during a heating ramp between two isothermal periods, the shrinking rate curve reaches a maximum value; and (c) rapid reduction of the shrinking rate is observed when an isothermal period is suddenly reached after a heating ramp. These features were tentatively explained by introducing some new mechanisms, which interfere with mass transport. Here, however, we report that these experimental observations can be explained within the framework of the standard theory of sintering. It is not necessary to include any dependence of the mass transport mechanisms on the heating rate in order to describe the observed behaviour.