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Characterization of Phase Separation and Thermal History Effects in Magnesium Silicate Glass Fibers by Nuclear Magnetic Resonance Spectroscopy
Author(s) -
Stebbins Jonathan F.,
Kim Namjun,
Andrejcak Michael J.,
Boymel Paul M.,
Zoitos Bruce K.
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.1551-2916.2008.02844.x
Subject(s) - materials science , silicate , magnesium , spectroscopy , impurity , phase (matter) , relaxation (psychology) , analytical chemistry (journal) , magnetic separation , nuclear magnetic resonance spectroscopy , paramagnetism , nuclear magnetic resonance , chemical engineering , chemistry , chromatography , metallurgy , organic chemistry , physics , quantum mechanics , psychology , social psychology , engineering
Liquid–liquid immiscibility, leading to the separation of silica‐rich and silica‐poor domains, is a common phenomenon in binary silicate glasses, but can be difficult to detect and characterize when rapid cooling results in nano‐scale domain dimensions. 29 Si nuclear magnetic resonance (NMR) spectroscopy can be very useful for detecting such phase separation, because the exclusion of paramagnetic impurity ions from the silica‐rich regions can greatly slow their spin‐lattice relaxation rates. Properly designed experiments can therefore largely isolate the NMR signals from high‐silica and low‐silica domains, and thus provide information about their proportions, compositions, and short‐ to intermediate‐range structures. We demonstrate this approach here for fiber glasses that are predominantly magnesium, or calcium‐magnesium silicates, with minor contents of alumina. For bulk compositions within the known region of stable liquid immiscibility, phase separation occurs even when extremely rapid cooling yields fibers less than 1 μm in mean diameter. Slower cooling increases the extent of separation, while the addition of small amounts of alumina reduces it.