A New Sight on the Influence of Molten Salt in the Preparation of (Ta, Nb, Ti) C Nanopowder

The molten salt method (MSM) is an effective approach for obtaining multicomponent carbide nanopowders at low temperatures. However, the presence of impurities limits its application in the lower-temperature domains. To address this issue, (Ta, Nb, Ti) C nanopowders are fabricated by the MSM at 1100-1400 degrees C, and the dual-route synthesis mechanism is revealed. Results indicate that the synthesis temperature of pure (Ta, Nb, Ti) C nanopowders can be decreased with the addition of molten salt, which is determined by the formation and decomposition of the intermediates. During the synthesis process, the molten salt can provide the liquid-phase environment for the combination reaction between metal powders and carbon, facilitating the formation of homogeneous and nanosized powders. Meanwhile, the molten salt reacts with impurities to generate intermediates including KTaO3 and K1.04Ti8O16 at low temperatures, which subsequently form carbides through thermal reduction. This transformation can decrease the energy barrier of the synthesis process. Herein, a dual-route synthesis mechanism of preparing (Ta, Nb, Ti) C nanopowders by molten salt method is unveiled. Besides, the molten salt provides a liquid-phase environment, it is found that the formed intermediates (e.g., K1.04Ti8O16 and KTaO3), which remove impurities in the finished powder, also promote the formation of nanopowders.image (c) 2024 WILEY-VCH GmbH