Surface chemistry, dispersion behavior, and slip casting of Ti 3AlC2 suspensions
The surface chemistry and dispersion properties of aqueous Ti3AlC2 suspension were studied in terms of hydrolysis, adsorption, electrokinetic, and rheological measurements. The Ti3AlC2 particle had complex surface hydroxyl groups, such as ≡Ti–OH,=Al–OH, and −OTi–(OH)2, etc. The surface charging of the Ti3AlC2 particle and the ion environment of suspensions were governed by these surface groups, which thus strongly influenced the stability of Ti3AlC2 suspensions. PAA dispersant was added into the Ti3AlC2 suspension to depress the hydrolysis of the surface groups by the adsorption protection mechanism and to increase the stability of the suspension by the steric effect. Ti3AlC2 suspensions with 2.0 dwb% PAA had an excellent stability at pH=∼5 and presented the characteristics of Newtonian fluid. Based on the well-dispersed suspension, dense Ti3AlC2 materials were obtained by slip casting and after pressureless sintering. This work provides a feasible forming method for the engineering applications of MAX-phase ceramics, wherein complex shapes, large dimensions, or controlled microstructures are needed.
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