Abstract
With the combined merits of both metals and ceramics, including good electrical and thermal conductivity, ready machinability, exceptional damage tolerance, light weight, high rigidity, etc., the ternary layered MAX compounds have attracted much attention in the world. For the synthesis and consolidation of MAX phases, the relatively novel spark plasma sintering (or SPS in short) represents a very competitive technique for its high efficiency and energy saving. Since 2000’s, SPS has been extensively used for this propose, especially in Ti3SiC2 and Ti3SiC2-based composites. The present general results indicate that Ti/Si/TiC is the most appropriate powder mixture and Al is a good aid for the synthesis of high purity Ti3SiC2 by SPS. Various Ti3SiC2-based composites have also been consolidated by SPS and the related properties were improved, such as hardness, strength, fracture toughness and conductivity. It is very important to notice that, Ti3SiC2 phase can also be in situ synthesized in its composites as the commercial Ti3SiC2 powder is hardly available. A few other MAX phases have also been synthesized and consolidated by SPS in one step using various powder mixtures. However, much work should be done to clarify the synthesis mechanism and various processing windows for MAX phases by SPS technique. Lowering the fabrication cost and finding appropriate applications of MAX phases are also eagerly expected.
TopBackground
The general formula, Mn+1AXn (or MAX in short), represents a new class of thermodynamically stable nano-laminated compounds of the ternary carbides and nitrides (Barsoum, 2000; Zhang et al., 2009; Sun, 2011). Herein, n =1, 2, 3, M is an early transition metal, A is an A-group (mostly IIIA or IVA) element and X is C or N. The MAX phases have attracted much attention from the scientists all over the world due to their combined merits of both metals and ceramics, including electrical and thermal conductivity, ready machinability, exceptional damage tolerance, light weight, high rigidity, and so on. Among the MAX phases, Ti3SiC2 is a representative one and has been studied extensively in recent years (Barsoum et al., 1996; Zhou et al., 1998; El-Raghy et al., 1999; Zhang et al., 2003; Zhang et al., 2007; Zhang et al., 2009). Figure 1 shows that layered Ti3SiC2 consists of a layered structure with a double Ti-C block, each made up of two edge-sharing CTi6 octahedra (Arunajatesan et al., 1994; Barsoum, 2000). A square-planar Si sheet separates the double Ti-C blocks (Zhang et al., 2009).