Heating mechanism of spark plasma sintering

According to the plasma sintering process and our theoretical calculation, we analyzed the heating mechanism of spark plasma sintering (SPS). It is proposed that the sintering temperature of conductive materials rises faster mainly due to the contribution of the direct current (DC) component in pulse current, current skin effect and eddy current in the mould and blank, Joule's heat generated by eddy current in grains, small heat capacity of the heated system and direct-contact heating. For non-conductive materials, the similar reasons can be found except for the heat effect of eddy current. By analyzing the heating mechanism of SPS, it is concluded that the temperature on the surface of a conductive green body should be higher than that on the inner surface of the die, whereas the opposite case holds for a non-conductive blank, that has already been verified by Nagae et al. [Journal of the Japan Society of Powder and Powder Metallurgy 44 (1997) 945–950] and by Sumi et al. [Journal of the Japan Society of Powder and Powder Metallurgy 45 (1998) 153–157].