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Chemical Degradation of Si 3 N 4 ‐Bonded SiC Sidelining Materials in Aluminum Electrolysis Cells
Author(s) -
Wang Zhaohui,
Skybakmoen Egil,
Grande Tor
Publication year - 2009
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2009.03020.x
Subject(s) - electron microprobe , microstructure , materials science , degradation (telecommunications) , silicon , rietveld refinement , electrolysis , chemical composition , aluminium , chemical reaction , cathode , chemical engineering , x ray crystallography , mineralogy , analytical chemistry (journal) , diffraction , metallurgy , crystallography , chemistry , crystal structure , electrode , physics , organic chemistry , telecommunications , optics , chromatography , computer science , electrolyte , engineering , biochemistry
A thorough analysis of a silicon nitride (Si 3 N 4 )‐bonded SiC sidelining material from a Hall‐Heroult electrolysis cell is reported. Phase composition before and after chemical degradation of the material is obtained by quantitative analysis using Rietveld refinement of X‐ray diffraction data and chemical analysis. The main degradation products as a result of the oxidation of Si 3 N 4 binder phase are Si 2 ON 2 in the upper part and Na 2 SiO 3 in the lower part of the sidelining. The microstructure of α‐Si 3 N 4 (needle) and β‐Si 3 N 4 (shell) as well as the degradation products Si 2 ON 2 (fiber) and Na 2 SiO 3 (flake) were revealed by electron microprobe analysis. Chemical reactions and degradation mechanisms are proposed based on the presented findings. The degradation in the lower part is more severe than that in the upper part because Na diffusion from the cathode enhances the oxidation of Si 3 N 4 . The degradation changes the physical properties of Si 3 N 4 ‐bonded SiC such as density and porosity.