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

Abstract

Abstract Spark plasma sintering (SPS) was applied to consolidate the nano-Al 2 O 3 , TiO 2 , MgO powders and plasma-sprayed metastable Al 2 TiO 5 powder. The fully dense ceramics had been prepared successfully. It was found that the starting nano-Al 2 O 3 reacted with nano-TiO 2 powder to form the Al 2 TiO 5 phase after SPS consolidation at 1150 °C under a pressure of 63 MPa. The starting plasma-sprayed Al 2 TiO 5 was stable above 1150 °C after SPS under 63 MPa, though in oxidizing atmospheres under the ambient air pressure, the stable temperature range of Al 2 TiO 5 was above 1280 °C. There was a fast decomposition rate for plasma-sprayed Al 2 TiO 5 at 1000 °C during SPS, whereas in oxidizing atmospheres under the ambient air pressure at 1000 °C 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 Al 2 TiO 5 . The addition of MgO advanced the formation of Mg 0.3 Al 1.4 Ti 1.3 O 5 along with MgAl 2 O 4 in the ceramics prepared both from plasma-sprayed powder and from nano-powder. In comparison with the composition of the ceramics without MgO additive, α-Al 2 O 3 , TiO 2 , and Al 2 TiO 5 , the ceramics with MgO additive consisted of only two phases, Mg 0.3 Al 1.4 Ti 1.3 O 5 and MgAl 2 O 4 spinel. The small equiaxed MgAl 2 O 4 spinel grains were distributed in a matrix of Mg 0.3 Al 1.4 Ti 1.3 O 5 with a large grain size.