Preparation of Ti3AlC2 Bulk Ceramic via Aqueous Gelcasting Followed by Al-rich Pressureless Sintering

Abstract Ti3AlC2 bulk ceramics were prepared via aqueous gelcasting followed by C-rich and Al-rich pressureless sintering. The optimized pH value, zeta potential, dispersant content, and solid loading content were determined to be 10, 72.6 mV, 1.6 wt%, and 52 vol%, respectively. Impurities at ppm level containing in the flowing argon could cause severe decomposition of gelcasted bulk Ti3AlC2, forming whiskers of Al2OC and Al4O4C and floccule of AlN. C-rich pressureless sintering resulted in the delamination of a duplex layer of Ti(CO) and Ti3(AlO)Cx-Ti(O,C). The channels formed after debinding facilitated the outward diffusion of Al and the inward diffusion of O and C, and thereby promoting the decomposition of C-rich sintered Ti3AlC2. The combined effect of the unclosed channels and the porous reaction Ti3(AlO)Cx-Ti(O,C) layer brought a catastrophic reduction in the density and mechanical properties of the C-rich sintered Ti3AlC2 ceramic. While the Al-rich pressureless sintering system isolated C, CO and N2 and supplied a closed Al-rich atmosphere, thereby suppressing the decomposition reactions and promoting the sintering densification and ultimately leading to the superior in mechanical properties. The density, hardness, flexural strength and fracture toughness of the Al-rich sintered ceramic reaches 4.13 g/cm3, 4.36 GPa, 345 MPa, 4.79 MPa·m1/2, respectively.