Nanocomposites of Carbon Nanotubes Embedded in a (Ti,Al)N Coated Film

Titanium aluminum nitride ((Ti,Al)N) thin films are widely used as hard protective coating materials. Due to their remarkable tensile strength and elastic modulus carbon nanotubes (CNTs) are an ideal candidate as reinforcing components in such coatings. In this work (Ti,Al)N thin films were deposited on steel substrate by reactive magnetron sputtering and CNTs were grown on top by chemical vapor deposition (CVD). A second (Ti,Al)N film covered the CNTs in order to achieve a nanocomposite structure similar to reinforced concrete. The chemical evolution of the substrate, structure, morphology and growth of CNTs were analyzed by X-ray photoelectron spectroscopy and scanning electron microscopy. It was possible to achieve homogeneous dispersion of the CNTs within the matrix by adjusting the CVD time. Mechanical testing of the adherence and nanohardness of the (Ti,Al)N/CNT/(Ti,Al)N composite coating were performed by scratch and nanoindentation tests. The improvement of mechanical properties by CNT integration resulted in an increase of the hardness and of Young's modulus.