Spark plasma sintering (SPS) consolidated ceramic composites from plasma-sprayed metastable Al2TiO5 powder and nano-Al2O3, TiO2, and MgO powders

Spark plasma sintering (SPS) was applied to consolidate the nano-Al2O3, TiO2, MgO powders and plasma-sprayed metastable Al2TiO5 powder. The fully dense ceramics had been prepared successfully. It was found that the starting nano-Al2O3 reacted with nano-TiO2 powder to form the Al2TiO5 phase after SPS consolidation at 1150degreesC under a pressure of 6:3 MPa. The starting plasma-sprayed Al2TiO5 was stable above 1150degreesC after SPS under 63 MPa, though in oxidizing atmospheres under the ambient air pressure, the stable temperature range of Al2TiO5 was above 1280degreesC. There was a fast decomposition rate for plasma-sprayed Al2TiO5 at 1000degreesC during SPS, whereas in oxidizing atmospheres under the ambient air pressure at 1000degreesC its decomposition is very slow. The microstructure of powder, applied pressure, and/or SPS characteristics, etc. obviously had an effect on the stable temperature and/or decomposition rate of Al2TiO5. The addition of MgO advanced the formation of Mg0.3Al1.4Ti1.3O5 along with MgAl2O4 in the ceramics prepared both from plasma-sprayed powder and from nano-powder. In comparison with the composition of the ceramics without MgO additive, alpha-Al2O3, TiO2, and Al2TiO5, the ceramics with MgO additive consisted of only two phases, Mg0.3Al1.4Ti1.3O5 and MgAl2O4 spinel. The small equiaxed MgAl2O4 spinel grains were distributed in a matrix of Mg0.3Al1.4Ti1.3O5 with a large grain size. (C) 2004 Elsevier B.V. All rights reserved.