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Effect of Sodium on Microstructures and Thermoelastic Properties of Calcium Aluminate Cement–Bonded Refractories
Author(s) -
Alex Jennifer,
Vandeperre Luc,
Lee William E.,
Touzo Bruno,
Parr Chris
Publication year - 2016
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/jace.14046
Subject(s) - aluminate , materials science , sintering , spinel , crystallization , sodium aluminate , sodium , microstructure , thermal expansion , calcium , cordierite , phase (matter) , aluminium oxides , chemical engineering , mineralogy , cement , composite material , ceramic , metallurgy , aluminium , chemistry , catalysis , organic chemistry , engineering , biochemistry
The effect of sodium on refractory phase formation in a model Calcium Aluminate Cement–bonded refractory was investigated from 700°C to 1500°C. Sodium reacts with α‐alumina to form sodium β‐alumina (β‐Al 2 O 3 ) via the intermediate NaAlO 2 . Formation of β‐Al 2 O 3 disrupts the reaction path of calcia with alumina, delaying crystallization of calcium hexaluminate, CaO·6Al 2 O 3 , from 1350°C to 1500°C. β‐Al 2 O 3 is also shown to reduce Young's modulus and delay sintering. The presence of NaAlO 2 and β‐Al 2 O 3 result in an increase in internal friction. Increased linear expansion of up to 47% is observed when 1 wt% Na is added. The expansion is shown to scale with the amount of dopant with only 0.3 wt% Na leading to an additional 31% linear expansion. On cooling, the presence of β‐Al 2 O 3 can be demonstrated by a peak in internal friction between 1200°C and 1000°C which could be caused by Na + ion hopping along the spinel‐like planes.