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Microstructure and evolution of a magnesium lithium aluminosilicate matrix composite
Author(s) -
RUTERANA P.,
KERVADEC D.,
MAUPAS H.,
CHERMANT J. L.
Publication year - 1995
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.1995.tb03558.x
Subject(s) - spodumene , materials science , crystallite , microstructure , aluminosilicate , transmission electron microscopy , lithium (medication) , cordierite , composite material , amorphous solid , carbon fibers , mineralogy , composite number , chemical engineering , ceramic , crystallography , metallurgy , nanotechnology , chemistry , catalysis , medicine , biochemistry , endocrinology , engineering
Summary The microstructure of a magnesium lithium aluminosilicate glass ceramic composite has been investigated by scanning electron microscopy and analytical transmission electron microscopy. Attention was focused on the as‐received material, showing that there is a non‐uniform distribution of the major silicate phases inside the matrix. The largest part is made of spodumene‐type crystals containing more than 4wt% Mg. A minor part of the matrix is made of micrometre‐sized crystallites of spodumene and cordierite. The spodumene is always sensitive to the electron beam irradiation. The morphology of the amorphized spodumene areas indicates that it may have crystallized during a later stage of the matrix formation, filling the gaps between cordierite crystallites. The third component of the matrix is made of carbon‐rich areas. They can be as large as 10 μm and they always include amorphous Mg‐rich silicates. However, they are mainly small (a few tens of nanometres in width) when located at grain boundaries of spodumene crystals. In this case the turbostratic carbon patches are also intimately mixed with an Mg‐rich amorphous silicate. The interface between the matrix and the fibres has also been analysed, its thickness changes from one to the other, and it is sometimes empty due to decohesion. When it is filled, its outer part contains mainly tubostratic carbon and the inner part is a mixture of silicon oxide and probably carbon. After creep at 1373K, the spodumene‐type crystals are larger and they are no longer sensitive to the electron beam. The cordierite areas appear to shrink and the amorphous patches which were mixed with carbon transform into small crystallites (1–10 μm). The areas next to the fibres are found to extend irregularly into the matrix, probably as a result of a chemical reaction.