Chinese Journal of Magnetic Resonance ›› 2023, Vol. 40 ›› Issue (4): 376-384.doi: 10.11938/cjmr20233061

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Hydrothermal Crystallization of Niobium Oxide Nanorods Studied by 93Nb Nuclear Magnetic Resonance

SHEN Changzhi,ZHANG Linlin,LI Xin*(),SHEN Wanling#()   

  1. College of Chemistry and Chemical Engineering, Henan University of Technology, Zhengzhou 450001, China
  • Received:2023-03-27 Published:2023-12-05 Online:2023-05-15
  • Contact: * Tel: 0371-67756718, E-mail: lixin_chemi@haut.edu.cn;# Tel: 0371-67756718, E-mail: wshen@haut.edu.cn.

Abstract:

The crystallization process of hydrothermally synthesizing niobium oxide nanorods with ammonium niobium oxalate precursor was investigated using 93Nb NMR, combined with X-ray powder diffraction, transmission electron microscopy and quantum chemistry calculations. The results showed that the hydrothermal crystallization of ammonium niobium oxalate underwent a hydrolysis-polymerization reaction, starting with the hydrolysis of ammonium niobium oxalate, followed by the polymerization of the niobium-oxide monomers by condensation, resulting in dimers, trimers and multimers, and finally generating solid niobium oxide nanorods with disordered intra-layer and ordered inter-layer structures. The mechanism of crystallization process is “liquid phase nucleation”, with the layer-structured niobium oxide nanorods being produced within 1 h at 180 ℃. The subsequent hydrothermal treatment does not lead to significant growth of the nanorods, and new solid products are continuously generated independently from the solution.

Key words: 93Nb NMR, nano niobium oxide, ammonium niobium oxalate, hydrothermal, crystallization mechanism

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