Phase controlled synthesis of transition metal carbide nanocrystals by ultrafast flash Joule heating.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 35017518.
- Also identified by DOI 10.1038/s41467-021-27878-1 and PMC identifier 8752793.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Nanoscale carbides enhance ultra-strong ceramics and show activity as high-performance catalysts. Traditional lengthy carburization methods for carbide syntheses usually result in coked surface, large particle size, and uncontrolled phase. Here, a flash Joule heating process is developed for ultrafast synthesis of carbide nanocrystals within 1 s. Various interstitial transition metal carbides (TiC, ZrC, HfC, VC, NbC, TaC, Cr<sub>2</sub>C<sub>3</sub>, MoC, and W<sub>2</sub>C) and covalent carbides (B<sub>4</sub>C and SiC) are produced using low-cost precursors. By controlling pulse voltages, phase-pure molybdenum carbides including β-Mo<sub>2</sub>C and metastable α-MoC<sub>1-x</sub> and η-MoC<sub>1-x</sub> are selectively synthesized, demonstrating the excellent phase engineering ability of the flash Joule heating by broadly tunable energy input that can exceed 3000 K coupled with kinetically controlled ultrafast cooling (>10<sup>4</sup> K s<sup>-1</sup>). Theoretical calculation reveals carbon vacancies as the driving factor for topotactic transition of carbide phases. The phase-dependent hydrogen evolution capability of molybdenum carbides is investigated with β-Mo<sub>2</sub>C showing the best performance.