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2 Journal of Achievements in Materials and Manufacturing Engineering

2 2009

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Surface modification and functionalization of nanostructured carbons

100%

Stanishevsky A. , Catledge S. A. , Vohra Y.

2009

tom Vol. 37, nr 2

348-353

Purpose: Nanostructured carbon nanomaterials (e.g., nanocrystalline diamond films and particles, carbon nanotubes, carbon onions, fullerenes, etc.) are being extensively explored for numerous biomedical applications in surgical implants, therapy, drug delivery, and biosensoring due to their interesting physical, chemical, and biological properties. Such applications of carbon nanomaterials often require specific surface functionality to be introduced for better integration of these materials with physiological environment. In the last decade, substantial progress has been made in the development of controllable surface modification methods and in the introduction of different functional groups on the surface of carbon nanomaterials. Design/methodology/approach: This paper briefly overviews the surface modification and functionalization approaches for various carbon nanomaterials, and it focuses on the plasma modification and functionalization of nanocrystalline diamond films, diamond nanoparticles, and carbon nanospheres. The results on the surface characterization using FTIR and XPS techniques, and the preliminary studies of cellular response to these modified carbon nanomaterials are presented and discussed. Findings: The results of surface modification of NCD films, detonation nanodiamonds, and carbon nanospheres, demonstrate the flexibility of nanocarbons to attain various surface functionality that can be adjusted for specific applications. It has been shown that neither of tested nanocarbon materials was cytotoxic in this study, although the attachement and proliferation of various cells was strongly affected by the specific type of surface functionalization. Research limitations/implications: At the present, it is not clear to what degree the available surface sites on NCD films or carbon nanoparticles can be occupied with functional groups. Furthermore, while there is clear selectivity of cellular response to H, O, and F surface-terminated NCD films, the role of specific type of surface groups present on carbon nanoparticles has yet to be determined. Practical implications: The development of optimal strategies to functionalize various nanocarbons will have strong impact on the design of efficient nanostructured surfaces and particles for a variety of biological and medical applications. Originality/value: This work adds new insights to the expanding research in biomedical applications of nanoscale carbon materials.

Thermal stability and mechanical properties of sputtered Chromium-Molybdenum-Nitride (CrMoN) coatings

88%

Zou Y. , Walock M. J. , Catledge S. A. , Nouveau C. , Stanishevsky A.

2009

tom Vol. 37, nr 2

369-374

Purpose: The purpose of paper is to determinate thermal stability and mechanical properties of sputtered chromium-molybdenum-nitride (CrMoN) coatings. Design/methodology/approach: We have deposited 1.8 m-thick ternary Cr0.5Mo0.5N1.0 films on a CoCrMo alloy using a RF dual magnetron sputtering system, with Cr and Mo targets and N2 as the reactive gas. These films were subjected to various thermal treatments in Ar, air, and microwave plasma. The hardness, Young’s modulus, surface roughness, microstructure, and composition of films were studied by nanoindentation, AFM, x-ray diffraction, and x-ray photoelectron spectroscopy. Findings: The as-prepared CrMoN films consist of an amorphous Cr-rich nitride matrix with Mo-rich nitride crystalline grains, about 15 nm in size. These films are thermally stable up to 600şC in air. Thermal annealing in the air at 800şC resulted in an increase in surface roughness and hardness, due to film oxidation, with Cr2O3 as the main crystalline phase. Plasma treatment in a H2/N2 gas mixture, at 800şC, did not lead to grain growth. Instead, the existing grains were reduced to about 10 nm and a new nanocrystalline phase has been formed. This leads to a decrease in the surface roughness, and an increase in the film hardness. In addition, we have further modified the film properties through a combined thermal treatment process. Thermal annealing in the air at 800şC, followed by microwave plasma treatment at 800şC resulted in a film with decreased surface roughness, and improved mechanical properties. Reversing the order of the thermal treatments resulted in a further decrease in surface roughness, but it shows a reduction in the mechanical properties. Research limitations/implications: The present investigation was carried out with only one composition, Cr0.5Mo0.5N1.0, of ternary thin-film system. Originality/value: The combination of thermal and plasma treatments can be used to control the microstructure, surface topography, and mechanical properties of ternary CrMoN films. Such post-deposition treatments can further improve the materials properties for desired application, and to produce new nanocomposite materials with technologically important combination of properties.