MAX phases : Bridging the gap between metals and ceramics MAX phases : Bridging the gap between metals and ceramics

(C re d it: C re d it: R ad ov ic a nd B en ite z; T A M U .) T he term “MAX phases” was coined in the late 1990s and applies to a family of 60+ ternary carbides and nitrides that share a layered structure as illustrated in Figures 1 and 2. They are so called because of their chemical formula: Mn+1AXn —where n = 1, 2, or 3, where M is an early transition metal, A is an A-group element (specifically, the subset of elements 13–16), and X is carbon and/or nitrogen, Figure 2.1 Nowotny and coworkers2, 3 discovered most of these phases in powder form roughly 40 years ago. However, Barsoum and El-Raghy’s4 report in 1996 on the synthesis of phase-pure bulk Ti3SiC2 samples and their unusual combination of properties catalyzed renewed interest in them. Since then, research on the MAX phases has exploded. According to ISI, to date around 1,200 papers have been published on one MAX phase alone, Ti3SiC2, with roughly half of those published in the past six years. The MAX phases are a new and exciting class of carbides