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In-Situ Synthesis and Formation Mechanism of Al2O3-Spinel(N) Composite in Nitrogen Atmosphere under Low Oxygen Partial Pressure
S. Tong1, Y. Li1, J. Zhao2, M. Yan1, Y. Hong1, Q. Zheng1
1 School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
2 Beijing Lier High-Temperature Materials Co., Ltd., Beijing 102200, China
received May 8, 2017, received in revised form July 13, 2017, accepted August 20, 2017
Vol. 8, No. 4, Pages 513-518 DOI: 10.4416/JCST2017-00030
Abstract
Al2O3-spinel-containing nitrogen element composite, abbreviated as Al2O3-spinel(N) composite, was prepared using white corundum, sintered magnesia and active α-Al2O3 powder as raw materials, with magnesium aluminate sol as a binder, and fired at 1600 °C for 4 h in a nitrogen atmosphere with low oxygen partial pressure. The prepared Al2O3-spinel(N) composite was characterized and analyzed by means of XRD, SEM, and EDS and the mechanism for the formation of the spinel(N) was further investigated. The results show that in nitrogen atmosphere with low oxygen partial pressure, Al2O3-spinel(N) composite is composed of alumina, spinel-containing nitrogen element and a little aluminum nitride; the spinel-containing nitrogen bonds the aggregates and matrix together, further realizing dense sintering of the Al2O3-spinel(N) composite. The mechanism for formation of the spinel(N) can be described as follows: in nitrogen atmosphere with low oxygen partial pressure, magnesia is unstable and decomposes into Mg(g). Mg(g) diffuses and transfers along the pores or gaps in Al2O3-MgO composites and reacts with corundum or spinel, forming gas aluminum at the same time. The gas metal aluminum then nitrides into aluminum nitride. The formed aluminum nitride further solid-solves into spinel, forming the spinel-containing nitrogen element.
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Keywords
Magnesia aggregates, low oxygen partial pressure, Mg(g), spinel
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