WEB Enhanced thermal stability of metal matrix nanocomposites by nanocarbon reinforcements
Metal matrix nanocomposites reinforced by nanocarbon materials are very promising materials suitable for a large number of functional and structural applications. In this study, nanodiamond (ND) reinforced silver - and carbon nanotubes (CNT) reinforced nickel matrix nanocomposites are synthesized from powder blends of pure silver, nickel, ND and CNT powders by a combination of two severe plastic deformation methods, ball-milling and high-pressure torsion (HPT). Using HPT deformation, matrix grain refinement to an ultrafine grained or even nanocrystalline microstructure was possible and the microstructure was thoroughly analysed by scanning and transmission electron microscopy. Particular emphasis is given to the characterization of the nanocarbon reinforcement–metal interfaces, which also affects the deformation mechanism and thus the mechanical properties of the metal matrix nanocomposites. The main focus of this study is on the influence of the amount, type and distribution of the nanocarbon reinforcements on thermal stability. It is shown that the microstructural stability is less influenced by the amount of added nanocarbon reinforcements than by the nanocarbon reinforcement type and its distribution in the metal matrix. Only a low volume fraction of NDs is needed for thermal stabilization even at high homologous temperature.