Spark plasma sintering (SPS) consolidated ceramic composites from plasma-sprayed metastable Al_2TiO_5 powder and nano-Al_2O_3, TiO_2, and MgO powders

摘要

Spark plasma sintering (SPS) was applied to consolidate the nano-Al_2TiO_5, TiO_2, MgO powders and plasma-sprayed metastable Al_2TiO_5 powder. The fully dense ceramics had been prepared successfully. It was found that the starting nano-Al_2O_3 reacted with nano-TiO_2 powder to form the Al_2TiO_5 phase after SPS consolidation at 1150℃ under a pressure of 63 MPa. The starting plasma-sprayed Al_2TiO_5 was stable above 1150℃ after SPS under 63 MPa, though in oxidizing atmospheres under the ambient air pressure, the stable temperature range of Al_2TiO_5 was above 1280℃. There was a fast decomposition rate for plasma-sprayed Al_2TiO_5 at 1000℃ during SPS, whereas in oxidizing atmospheres under the ambient air pressure at 1000℃ 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_2TiO_5. The addition of MgO advanced the formation of Mg_(0.3)Al_(1.4)Ti_(1.3)O_5 along with MgAl_2O_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_2O_3, TiO2, and Al_2TiO_5, the ceramics with MgO additive consisted of only two phases, Mg_(0.3)Al_(1.4)Ti_(1.3)O_5 and MgAl_2O_4 spinel. The small equiaxed MgAl_2O_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.