Model experiments on initial stage of microwave sintering of nickel powder showed anomalous neck-growth rate during isothermal soaking, which is not the case for conventional sintering. Neck growth was determined as a function of time. Values for the neck growth exponent in the neck growth equation, (x/a)n = Bt, of 5.2, 5.4, 5.8, and 5.9 were found for within the temperature range 700-950 °C, respectively. The evidences of formation of liquid phase during microwave sintering have been revealed, that may support enhancement of mass transfer during sintering process. The activation energy of 48 kJ mol-1 was found for microwave sintering of nickel, according to sphere-to-sphere model. Value revealed is significantly lower then values for conventional sintering (136 kJ mol-1), and is on same level with activation energy for diffusion of metals in liquid state. An explanation and analysis of this phenomenon has been attempted.
- Microwave heating