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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 required1,2. 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.

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Fig. 1: MS3 process and the synthesized/sintered materials.
Fig. 2: Thermal analysis of KBr-encapsulated Ti3SiC2 and Ti.
Fig. 3: Interaction of Ti and Ti3SiC2 with molten salt.
Fig. 4: Temperature–purity regime for different phases synthesized by conventional routes.

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The authors confirm that all the data generated and necessary to interpret the scientific findings are available within the paper. Extra data can be obtained from the corresponding authors upon request.

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Acknowledgements

This work was funded by Germany’s Federal Ministry of Education and Research (Bundesministerium für Bildung und Forschung) under the MAXCOM project (03SF0534).

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A.D. proposed the original idea and carried out the experiments. J.G.-J. supervised A.D. All authors contributed to discussion of the results and writing of the manuscript.

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Correspondence to Apurv Dash.

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Supplementary Figures 1–4, Supplementary Tables 1–3, Supplementary References 1–34

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Dash, A., Vaßen, R., Guillon, O. et al. Molten salt shielded synthesis of oxidation prone materials in air. Nat. Mater. 18, 465–470 (2019). https://doi.org/10.1038/s41563-019-0328-1

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