Max Phase Ceramics

211 for m 2 ax n 1 312 for m 3 ax 2 n 2 and 413 for m 4 ax 3 n 3.

Max phase ceramics.

Max phases such as ti3 sic 2 ti 3 alc 2 ti 2 alc ti 4 aln 3 ti 2 aln nb 4 alc 3 and nb 2 alc are a new class of nanolayered hexagonal ceramics with the general formula m n 1 ax n where n 1 3 m is an early transition metal a is a group a element and x is carbon or nitrogen barsoum 2000. The max phases are layered hexagonal carbides and nitrides which have the general formula. They have an inherently nano layered structure with alternating ceramic mx and metallic a layers. 5 the density of states at the fermi level is substantial and dominated by the d d orbitals of the m element.

Due to this reason max phases fit into a wide range of applications from electronic to structural materials. The max phases comprise an early transition metal m an a group element a and either carbon or nitrogen x. Table of the known m n 1 ax n phases. It was found that both ti 3 sic 2 and ti 4 sic 3 may be obtained in good yields depending on the annealing time during the reduction step.

The blue are the a el. In addition to max phases the products. Mn 1axn where n 1 to 4 and m is an early transition metal a is an a group element and x is either carbon and or nitrogen. Sorted by stoichiometry and valence electron configuration for the m and a elements.

Click to see structural properties. Dispersion and rheology control for improved ceramic processing. So far 60 max phases have been discovered. The most oxidation resistant max phase is ti 2 alc because it forms a stable and protective al 2 o 3 layer that can withstand thermal cycling up to 1 350 c for 10 000 cycles without spallation or cracking figure 4 33 the.

1 the max phases are interesting because they exhibit a unique combination of ceramic and metallic properties. 2 4 their bonding is a combination of covalent and metallic. 5 similarly their electrical resistivity is metal like. Ti 3 sic 2 and ti 4 sic 3 max phase ceramics were fabricated through high temperature vacuum reduction of tio 2 using sic as a reductant followed by hot pressing of the products under 25 mpa of pressure at 1600 c.

These materials serve as a bridge between metals and ceramics having advantages from both classes of materials. The max phases can be classified according to their values of n. Abstract this chapter summarizes the new class of carbides and nitrides discovered in recent decades. The layered structure consists of edge sharing distorted xm6 octahedra interleaved by single planar layers of the a group element.

Elements in the periodic table that react together to form the remarkable max phases. The unique mix of both ceramic and metallic properties have made max phases a proposed material for nuclear applications. Most of these phases were discovered in powder form already in the 1960s though the synthesis of phase pure bulk samples was only achieved in 1996.