The formation of NaMg2Al15O25 in an α-Al2O3 matrix and its effect on the mechanical properties of alumina
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An in-situ sintering reaction was designed to produce lath-like \‴-alumina in an α-alumina matrix in order to make alumina ceramics stronger and tougher. The reaction sequence to produce \‴-alumina (NaMg2Al15O25) requires the formation of \-alumina (NaAl11O17) and spinel (MgAl2O4) at around 1100 dgC followed by a solid-state reaction of these two phases to give \‴-alumina at elevated temperatures; this reaction is complete at around 1600 °C. The in-situ sintering reaction produces near-theoretically dense alumina ceramics in which lath-like \‴-aluminas are homogeneously distributed. The bending strength and fracture toughness increase to 620 MPa and 5 MPam1/2, respectively; these increases are thought to be due to the suppression of grain growth as well as the crack deflection and bridging associated with lath-like \‴-alumina.
KeywordsPolymer Alumina Mechanical Property Elevated Temperature Fracture Toughness
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