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Phase Equilibria in Subsystems of the Quaternary Reciprocal System Na 2 O‐SiO 2 ‐Al 2 O 3 ‐NaF‐SiF 4 ‐AlF 3
Author(s) -
Rutlin Jørn,
Grande Tor
Publication year - 1999
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.1151-2916.1999.tb02116.x
Subject(s) - cryolite , nepheline , albite , mullite , fluoride , phase (matter) , phase diagram , inorganic chemistry , mineralogy , materials science , chemistry , metallurgy , aluminium , ceramic , quartz , organic chemistry
The phase relations in the pseudobinary system sodium fluoride‐mullite have been investigated as a model system for fluoride attack on fire clay refractories in aluminum electrolysis cells. The phase composition below the solidus temperature 857°C changes from sodium fluoride, cryolite, nepheline, and ß‐alumina to cryolite, albite, silica, and α‐alumina with increasing oxide content. Albite was not observed to crystallize and an increasing amount of glass was observed with increasing mullite content. The phase diagram of the ternary system sodium fluoride‐cryolite‐nepheline was also measured in order to describe the composition of the most stable melt along the sodium fluoride‐mullite composition join. The present findings are discussed in relation to the deterioration mechanism of fire clay refractories during fluoride attack. The formation of viscous albite‐based melts is suggested to increase the resistance toward fluoride attack due to the reduced diffusion rate of fluorides.