ICMCTF2008 Session D3-2: Carbon-Based Nanostructured Composite and Nanolaminated Films

Thursday, May 1, 2008 8:00 AM in Room Royal Palm 4-6

Thursday Morning

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8:00 AM D3-2-1 Carbon-Based Nanocomposite Thin Films - Deposition, Structure and Properties
W. Gulbinski (Koszalin University of Technology, Poland)

Carbon based coatings are widely used for numerous applications spreading from specialized cutting tools for wood processing, through medical equipment and implants to optical instruments and data storage media. The coatings afford high hardness, low friction coefficient, high wear resistance and chemical inertness.

Their properties become still more attractive when carbon is combined with hard carbides of refractory metals (W, V, Mo, Ti). Composite coatings containing nanocrystalline carbides, embedded in relatively softer carbon matrix, show extraordinary combination of properties like low friction and wear rate, high hardness and toughness. An increase in hardness of composites in comparison to that of single phase coatings is based on the suppression of dislocation propagation. Oxidation resistance of these attractive materials can be improved by addition of silicon.

Alternatively, introduction of soft metal inclusions (Ag, Au, Cu, Ni, Co), usually inert or showing low reactivity to carbon, leads not only to intrinsic stress reduction but also results in improved adhesion to industrially accepted substrate materials. A nanocomposite structure containing conductive metal clusters (Cu, Ag, Au) in insulating, amorphous carbon matrix has shown high k properties whereas introduction of ferromagnetic clusters (Ni, Co) results in attractive magnetic properties. A large variety of methods allows deposition of carbon based nanocomposite films. Mostly used are PVD techniques (magnetron sputtering, filtered arc deposition). In parallel, several plasma enhanced CVD and hybrid methods have been developed.

8:40 AM D3-2-4 Multifunctional Nanocomposite Carbides for Electric/Mechanical Contacts
J. Lauridsen (Linköping University, Sweden); T. Joelsson, H. Ljungcrantz (Impact Coatings AB, Sweden); H. Högberg, L. Hultman (Linköping University, Sweden)

Nanocomposite thin films comprising nanocrystalline TiC embedded in an amorphous SiC matrix (nc-TiC/a-SiC) are promising as electrical sliding contacts1. The thin film material is multifunctional as it combines good electrical contact properties, ductility, chemical stability, and wear resistance. With these properties a wide range of applications for such thin films are suggested, for instance in electronics. This field requires controlled synthesis of the material preferably at low temperatures (≤300°C) to enable growth on commercial substrate materials. An outstanding question is, however, how the nanocomposite deposition process will be influenced when scaled up to an industrial level, and what will be the microstructure of the resulting thin films. In this study, we have deposited nc-TiC/a-SiC by DC magnetron sputtering in a pilot-plant scale system onto different substrate materials (including silicon, steel and electro-plated Ni on a Cu cylinder) held at 270°C from a Ti3SiC2 compound target. Deposition rates of more than 15µm/h are demonstrated which should enable a high throughput for the coated details. The resulting thin films are analyzed with respect to microstructure, resistivity and mechanical properties by using XRD, SEM, TEM, ERDA, nanoindentation, resistivity and resistance measurements. We find that the nanocomposite thin films are dense and consist of 15-23nm TiC grains with a (111) texture in a minority phase matrix of a-SiC, depending on the deposition rate.

1Per Eklund et al., J. Vac. Sci. Technol.B, 2005, Vol. 23, 2486-2495.

9:00 AM D3-2-5 Control of Morphology and Porosity in Porous Carbon with Tunable Pore Size
C.-Y. Liu (National Chiao-Tung University, Taiwan); C.-F. Chen (Mingdao University, Taiwan); J.-P. Leu (National Chiao-Tung University, Taiwan)
The study utilized with the preparation of porous carbon using 2-D hexagonal SBA-15 as hard template. The influence on morphology and texture of parent silica template and porous carbon are studied. Morphology can be tailored as randomly porous carbon or well ordered porous carbon maintained using different silica templates. On the other hand, porous carbon pore size can be varied at 3.0-4.1 nm. The silica template and the porous carbon were characterized by nitrogen sorption measurement and X-ray diffraction (XRD). Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM) show the different morphology of porous carbon. With our method, the characteristics of the silica templates have a crucial role in controlling the morphologies and porosity of porous carbon directly toward formation of different structures.
9:20 AM D3-2-6 Role of Amorphous Phase on Grain Growth in Two-Phase nc-TiN/a-(C,CNx) Nanocomposite Films
Y.H. Lu, X.J. Hu, Y.G. Shen (City University of Hong Kong)
The grain growth in two-phase nanocomposite Ti-Cx-Ny thin films grown by reactive close-field unbalanced magnetron sputtering in an Ar-N2 gas mixture with microstructures comprising of nanocrystalline (nc-) Ti(N,C) phase surrounded by amorphous (a-) (C,CNx) phase was investigated by a combination of high-resolution transmission electron microscopy (HRTEM) and Monte Carlo (MC) simulations. The HRTEM results revealed that amorphous-free solid solution Ti(C,N) thin films exhibited polycrystallites with different sizes, orientations and irregular shapes. The grain size varied in the range between several nanometers and several decade nanometers. Further increase of C content (up to ~19 at.% C) made the amorphous phase wet nanocrystallites, which strongly hindered the growth of nanocrystallites. As a result, more regular Ti(C,N) nanocrystallites with an average size of ~5 nm were found to be separated by ~0.5-nm amorphous phases. When C content was further increased (up to ~48 at.% in this study), thicker amorphous matrices were produced and followed by the formation of smaller sized grains with lognormal distribution. Our MC analysis indicated that with increasing amorphous volume fraction (i.e. increasing C content), the transformation from nc/nc grain boundary (GB)-curvature-driven growth to a/nc GB-curvature-driven growth is directly responsible for the observed grain growth from great inhomogeneity to homogeneity process.
9:40 AM D3-2-8 Enhancement of the Field Emission Property of MWNT With Amorphous Fluorinated Carbon Films
H.-D. Lin, Y.-H. Lin, U.-S. Chen, T.P. Perng, H.-C. Shih (National Tsing Hua University, Taiwan)
Recently, carbon nanotubes have been proven to be promising candidate for the field emission display (FEDs) applications because of their excellent electron field emission properties. In this work, the CVD synthesized multiwalled carbon nanotubes (MWCNTs) were synthesized on a silicon substrate and then coated with fluorinated amorphous carbon (a-C:F) films. We will further report that the turn-on field (Eto) of the MWCNTs have been decreased by the assistance of a-C:F films from 0.8 V/µm to 0.01 V/Ä. The result reveals that the fluorinated amorphous carbon films assisted MWCNTs have excellent performance on electron field emission.
10:00 AM D3-2-9 Pulsed Closed Field Unbalanced Magnetron Sputtering (P-CFUBMS) of nc:TiC/a:C Nanocomposite Thin Films
J. Lin, J.J. Moore, B. Mishra (Colorado School of Mines); M. Pinkas (Nuclear Research Center, Israel); W.D. Sproul (Reactive Sputtering, Inc.)
TiC/a:C nanocomposite thin films were prepared by reactively sputtering titanium and graphite targets in a pure argon atmosphere using a pulsed closed field unbalanced magnetron sputtering (P-CFUBMS) system. The effects of film compositions and pulsing parameters on the structure and properties of TiC/a:C thin films were studied in an effort to achieve an optimized combination of high hardness, good wear resistance, and low friction in the films. By controlling the Ti:C composition, the films show a low sliding friction coefficient (0.24) against 440C stainless steel ball and a hardness of 28 GPa when the carbon content reaches 60 at.%. Further increase in the carbon content will further decrease the friction coefficient of the film, but increase the wear rate due to a decrease in the hardness of the films. Pulsing the Ti and C targets asynchronously (100 kHz and different duty cycles) will lead to a microstructural refinement in the TiC/a:C films, accompanied by an increase in the hardness and a decrease in the wear rate. When both Ti and graphite targets were pulsed at 100 kHz and 5.0 micros, the film exhibits a high hardness of 32 Gpa, a friction coefficient of 0.28 and a low wear rate of 2.2x10-7mm3N-1m-1.
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