Molten salt shielded synthesis of oxidation prone materials in air

Abstract

To prevent spontaneous oxidation during the high-temperature synthesis of non-oxide ceramics, an inert atmosphere is conventionally required^1,2. This, however, results in high energy demand and high production costs. Here, we present a process for the synthesis and consolidation of oxidation-prone materials, the 'molten salt shielded synthesis/sintering' process (MS³), which uses molten salts as a reaction medium and also to protect the ceramic powders from oxidation during high-temperature processing in air. Synthesis temperatures are also reduced, and the final product is a highly pure, fine and loose powder that does not require additional milling steps. MS³ has been used for the synthesis of different ternary transition metal compounds (MAX phases, such as Ti₃SiC₂³, Ti₂AlN⁴, MoAlB⁵), binary carbides (TiC) and for the sintering of titanium. The availability of high-quality powders, combined with energy and cost savings, may remove one of the bottlenecks for the industrial application of these materials.