Impact of Sintering Temperature Variation on Porous Structure of MoTiAlC Ceramics.

Mo, TiH, Al and graphite elemental powders were used as starting materials for the activation reaction sintering process, which was employed to fabricate porous MoTiAlC. The alteration of phase constitution, volume expansion, porosity, pore size and surface morphology of porous MoTiAlC with sintering temperatures ranging from 700 °C to 1500 °C were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and pore size tester. Both the pore formation mechanism and activation reaction process at each temperature stage were investigated. The experimental results illustrate that the sintered discs of porous MoTiAlC exhibit obvious volume expansion and pore structure change during the sintering process. Before 1300 °C, the volume expansion rate and porosity increase with the increment of temperature. However, with the sintering temperature above 1300 °C, the volume expansion rate and porosity decrease. At the final sintering temperature of 1500 °C, porous MoTiAlC with a volume expansion rate of 35.74%, overall porosity of 47.1%, and uniform pore structure was synthesized. The pore-forming mechanism of porous MoTiAlC is discussed, and the evolution of pressed pores, the removal of molding agents, the decomposition of TiH, and the Kirkendall effect caused by different diffusion rates of elements in the diffusion reaction are all accountable for the formation of pores.