Phase controlled synthesis of transition metal carbide nanocrystals by ultrafast flash Joule heating [electronic resource]

• Ngôn ngữ: eng
• Ký hiệu phân loại: 622.338 *Oil, oil shales, tar sands, natural gas
• Thông tin xuất bản: Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2022
• Mô tả vật lý: Size: Article No. 262 : , digital, PDF file.
• Bộ sưu tập: Metadata
• ID: 267672
• Chủ đề: 1. 01 coal, lignite, and peat; 2. Electronic materials; 3. Inorganic chemistry

Tóm tắt

 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 ?-Mo<
 sub>
 2<
 /sub>
 C and metastable ?-MoC<
 sub>
 1-x<
 /sub>
  and ?-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 ?-Mo<
 sub>
 2<
 /sub>
 C showing the best performance.