Synthesis and characterisation of ternary nano-laminated ceramics for emerging technologies

The research presented in this thesis describes a series of studies on new synthesis techniques which were applied to two related families of nano-laminated ternary transition metal ceramics, MAX and MAB phases. For the first time, the laser cladding process was investigated as a potential time and cost-effective method for producing MAX phase coatings in situ. The studies found that laser cladding is incredibly effective at depositing coatings in the Ti-Al-C system onto titanium substrates, producing mm-scale thick coatings in a matter of seconds to minutes, with the production of sample sizes up to ~ 90 x 90 mm2. While the direct deposition of these coatings showed some success in the in situ formation of the MAX phases, post-deposition furnace annealing treatments were also developed to improve the phase-purity. Due to the recent discovery of MAB phases as potential materials for use in demanding applications, some basic characterisation of these materials and their properties was undertaken using standard powder metallurgy techniques. In particular, experimental investigations of solid-solution (Mo,W)AlB MAB phases were completed as a way to approach the bulk synthesis of MAB phases close to the W end of the composition range. This was motivated by the fact that the WAlB MAB phase has not previously been synthesised in the bulk form and may prove to be a beneficial material for use in nuclear fusion applications. Research was also undertaken for the first time, to investigate the high temperature radiation tolerance of MoAlB and Fe2AlB2, which were found to be comparable to existing radiation-tolerant materials including MAX phases and SiC. Finally, inspired by some unusual observations during and after preparation of MAB phase samples, assessment of the electrocatalytic performance of Fe2AlB2 and MoAlB powders for the reduction of nitrogen was conducted. MoAlB was found to have a high Faradaic efficiency and cycle stability for NH3 production, offering the potential for an environmentally friendly pathway towards ambient-condition NH3 synthesis, compared with the Haber-Bosch process.