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From Macro to Nanomagnesia: Designing the in situ Spinel Expansion
Author(s) -
Braulio Mariana A. L.,
Castro José F. R.,
Pagliosa Carlos,
Bittencourt Luís R. M.,
Pandolfelli Victor C.
Publication year - 2008
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.1551-2916.2008.02566.x
Subject(s) - spinel , materials science , grain size , thermal expansion , magnesium , ball mill , mineralogy , refractory (planetary science) , metallurgy , grain growth , chemical engineering , composite material , chemistry , engineering
Magnesia grain size affects the in situ spinel formation kinetics and expansion of alumina–magnesia refractory castables. The use of coarse grains results in a large expansion and delays the reaction's starting temperature. In this work, the addition of an MgO source with different grain sizes (from macro, D max ≤0.1 mm, to nano, D 50 ≤20 nm) led to a broad linear expansion range (6%–2%), considering the spinel and the CA 6 formation. The addition of nanomagnesia, produced by a centrifugal‐type high‐energy ball milling, to high‐alumina refractory castables affected the spinel expansion and its starting temperature. The objective to estimate the reaction starting temperature was attained, reducing it from 1200° to 900°C. Nevertheless, the decrease of spinel expansion was not totally fulfilled, as a portion of the nanoparticles partly reagglomerated before mixing and behaved as coarser magnesia grains.