Home – Home – Jornals – Chemistry for Sustainable Development 2017 number 3

Composite materials based on α-alumina reinforced by carbon nanotubes were prepared. Synthesis of materials was performed by mechanochemical mixing of Al₂O₃ nanoparticles with pre-ultrasonicated 0.5-3 mass % multiwall or single-wall nanotubes. The resulting pressed powder was characterized by a uniform distribution of nanotubes. Green body consolidation was carried out by cold isostatic pressing followed by vacuum sintering and successive isostatic pressing at 200 MPa and temperatures not higher than 1520 °C. It was found that the density of the resulting composite material achieved under such experimental conditions was nearly theoretical and nanotubes have not been considerably damaged by the reaction between carbon and alumina. Introduction of carbon nanotubes in the alumina matrix proved to be ineffective in terms of mechanical properties (hardness, bending strength) enhancement when compared with pure alumina ceramics made of the same alumina powder. This is likely due to poor interface quality between a nanotube and the matrix. It was found that the density of the resulting ceramic material was close to theoretically possible; however, the destruction of nanotubes due to the reaction with alumina did not happen. It was demonstrated that the introduction of CNT into the alumina matrix based on nanopowders did not contribute to the improvement of mechanical (hardness, bending strength) features compared to the non-doped material. Apparently, this was due to a poor chemical interface at the phase boundary.