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Formation Mechanisms of the Interfaces between Different TinO2n-1 Phases Prepared by Carbothermal Reduction Reaction

Abstract

Carbothermal reduction reaction (CRR) is the most commonly ultilized method to synthesize the Magnéli phase reduced titanium oxide nanocrystals. Though the reaction process have been investigated from the perspective of thermodynamic and kinetics, research work foscused on the detailed formation mechanism of the interfaces from the reactant to product is still limited. In this work, the structures and formation mechanisms of the interfaces between different TinO2n-1 phases was investigated based on comprehensive XRD, Raman spectroscopy and TEM characterizations. Both XRD and Raman spectroscopy results indicated that the formation sequence of the TinO2n-1 phases during the CRR is TiO2→TinO2n-1 (4≤n≤9) →Ti3O5→Ti2O3→TiO regardless of the introduction method of carbon source. In addition, the surface encapsulation of polydopamine (PDA) on TiO2 precursor can effectively reduce the reaction temperature when compared with the samples that through the ball-mill mixing of TiO2 and carbon. Furthermore, the interfaces of Ti4O7/Ti5O9 and Ti3O5/Ti4O7 were obtained after the CRR under different introduction methods of the carbon source. TEM results suggested the different coherency of these interfaces, which might be due to the different formation mechanisms. By calculating the Gibbs free energies under the temperature range from 298 K to 1598 K of some involved reactions, it was noticed that the reaction between TiO2 and carbon can process spontaneously to form TinO2n-1 phases (2≤n≤10) at the whole temperature range. In contrast, the reaction between TinO2n-1 phases with differernt n values cannot be conducted spontaneously when n≤3 from 298 K to 1598 K, which further validate the oriented attachemnt growth mechanism of Ti3O5/Ti4O7 interface rather than the direct CRR. Finally, the growth mechanisms of the two types of interfaces were summarized from both atomic and nano scale.

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Publication details

The article was received on 29 Aug 2018, accepted on 14 Nov 2018 and first published on 15 Nov 2018


Article type: Paper
DOI: 10.1039/C8CE01459K
Citation: CrystEngComm, 2018, Accepted Manuscript
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    Formation Mechanisms of the Interfaces between Different TinO2n-1 Phases Prepared by Carbothermal Reduction Reaction

    F. Wang, R. Shi, Y. Lei, Z. Lei, R. Jiang, D. Wang, Z. Liu and J. Sun, CrystEngComm, 2018, Accepted Manuscript , DOI: 10.1039/C8CE01459K

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