AVS 53rd International Symposium
    Advanced Surface Engineering Thursday Sessions
       Session SE2-ThM

Paper SE2-ThM9
Growth and Characterization of Diamond/CNT Nanocomposites using Hot-Filament Assisted Chemical Vapor Deposition

Thursday, November 16, 2006, 10:40 am, Room 2007a

Session: Hard and Nanocomposite Coatings: Synthesis, Structure, and Properties
Presenter: N. Shankar, University of Illinois Urbana-Champaign
Authors: N. Shankar, University of Illinois Urbana-Champaign
N.G. Glumac, University of Illinois Urbana-Champaign
M.-F. Yu, University of Illinois Urbana-Champaign
S.P. Vanka, University of Illinois Urbana-Champaign
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Superhard materials are characterized by a bulk hardness of 40 GPa or more. However this extreme hardness is often offset by their inherent brittleness. In wear application where hard materials are typically used, it may be necessary to improve the toughness of the hard coatings for improved reliability, performance and durability. Reinforcing these hard materials with a tough second phase would possibly produce hard and tough composites which have the potential to outperform conventional hard coatings. We have developed a superhard-supertough composite from diamond and carbon nanotubes (CNT) by Hot Filament assisted Chemical Vapor Deposition (HFCVD). The growth was achieved by initially pre-dispersing commercially available multiwalled CNT onto a Si(100) surface and then subsequently growing diamond over this layer. The diamond/CNT composites were characterized using SEM, TEM, and Raman Spectroscopy. It was found that at 1% CH@sub 4@ in H@sub 2@ (a typical condition for diamond growth using HFCVD) most of the CNT are destroyed by the harsh growth conditions. A parametric study of growth phase-space revealed a selective window between 2-5% of CH@sub 4@ in H@sub 2@ wherein the CNT are not destroyed and the resulting diamond film still retained a high percentage of its sp@super 3@ structure. The TEM analyses showed that nanometer sized diamond particles nucleate on the surface of the CNT and grow radially outward. Based on the detailed characterization of the composites, a growth mechanism for diamond onto the CNT has been proposed. To the best of our knowledge, this is the first time that a successful composite of diamond and multiwalled CNT has been produced with direct bonding between the diamond and CNT resulting in good load transfer at the interface between the matrix and reinforcement.