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Effects of Silica on the Combustion Synthesis and Glass Formation of TiB 2 ‐Containing Calcium Aluminate Matrix Composites
Author(s) -
Yi Hu Chun,
Guigné Jacques Y.,
Robinson Lisa A.,
Manerbino Anthony R.,
Moore John J.
Publication year - 2006
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.1551-2916.2005.00690.x
Subject(s) - materials science , microstructure , aluminate , phase (matter) , matrix (chemical analysis) , amorphous solid , combustion , calcium aluminosilicate , composite material , chemical engineering , reactivity (psychology) , mineralogy , aluminosilicate , chemistry , crystallography , catalysis , cement , organic chemistry , engineering , medicine , alternative medicine , pathology
Combustion synthesis has been used to study the combustion characteristics and microstructure in the TiB 2 –CaO–Al 2 O 3 –SiO 2 system. Both the combustion temperature and wave velocity decreased with an increase in the amount of silica. The reacted product consisted of solid crystalline TiB 2 phase and CaO–Al 2 O 3 –SiO 2 matrix. No significant reaction between the TiB 2 and the matrix was observed. It was found that the binary calcium aluminate matrix (Ca 12 Al 7 O 33 and CaAl 2 O 4 compounds) could form amorphous phase (glass) at a high cooling rate. Under a normal cooling rate, significant formation of glass in the matrix was found possible only by adding another glass‐former, e.g., silica (SiO 2 ). The addition of SiO 2 led to the formation of Gehelenite, to the reduction of the other crystal phases and to an increase in the glass phase in the matrix. A pure glass matrix was obtained for all compositions in the composition range from Ca 12 Al 7 O 33 to CaAl 2 O 4 compounds provided that an adequate amount of SiO 2 was added. The resulting glass matrix can be expressed by the formula Ca 2 (Si x Al 1− x ) 3 O, where x =0.32–0.58, depending on the composition. Effects of the TiB 2 phase on the combustion synthesis process and on the microstructure are also discussed. TiB 2 increased the reactivity and led to the formation of the molten matrix which was critical for glass formation. However, its effects on the vitrification of the matrix was considered to be minimum. The mechanism of glass formation in the matrix is discussed using the Zachariasen–Warren network theory.