Stabilizing effect of the carbon shell on phase transformation of the nanocrystalline alumina particles

Ilya V. Yakovlev, Alexander M. Volodin, Vladimir I. Zaikovskii, Vladimir O. Stoyanovskii, Olga B. Lapina, Aleksey A. Vedyagin

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Intensive phase transformations of alumina are known to occur at temperatures above 1000 °C. In the present work, high temperature behaviour of pure Al2O3 and the carbon coated Al2O3@C sample with core-shell structure was comparatively studied using low-temperature nitrogen adsorption, transmission electron microscopy, powder X-ray diffraction (XRD) analysis and solid-state nuclear magnetic resonance (NMR). The solid-state NMR 27Al method has allowed us to identify and estimate the concentration of all phases appeared during the transformation of pseudoboehmite γ-Al2O3 into corundum α-Al2O3. The data obtained correlate well with the results of XRD analysis and low-temperature nitrogen adsorption. It is shown that the deposition of carbon coating with formation of core-shell Al2O3@C system stabilizes the size of oxide core and prevents the formation of corundum phase until the temperatures of 1350–1400 °C, which are close to the temperature of carbothermal reduction of alumina. The stabilization of the size of the oxide core nanoparticles was considered as a main factor preventing the formation of corundum phase at high temperatures. At the same time, the carbon coating does not affect the phase transformation of γ-Al2O3 to δ-Al2O3.

Original languageEnglish
Pages (from-to)4801-4806
Number of pages6
JournalCeramics International
Volume44
Issue number5
DOIs
Publication statusPublished - 1 Apr 2018

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Keywords

  • Alumina
  • Carbon coating
  • Core-shell structure
  • Phase transformations
  • Solid-state NMR
  • Stabilization effect

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Process Chemistry and Technology
  • Surfaces, Coatings and Films
  • Materials Chemistry

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