Surface modification of 6150 steel substrates for the deposition of thick and adherent diamond-like carbon coatings

AbstractBecause of the high residual compressive stress normally accompanying the growth of diamond-like carbon (DLC) coatings and the large mismatch in the thermal expansion coefficient between DLC and steel, it is difficult to grow DLC coatings much thicker than 0.25μm on steels. This paper describes our attempt to overcome this thickness limitation by a sequence of carbonitriding, carburizing and equilibration pre-treatments of the steel surface, followed by DLC coating deposition, all conducted within the same deposition system without breaking vacuum. These pre-treatments resulted in a surface with a graded composition and hardness profile. Such a graded interface is expected to reduce the interfacial energy, decrease thermal mismatch between the coating and the substrate, and thus improve coating adhesion. X-ray diffraction revealed the formation of various hard carbide and nitride phases. Raman spectroscopy showed that the modified steel surface just before DLC deposition exhibits local carbon bonding characteristics similar to DLC. Pulsed dc plasma-enhanced chemical vapor deposition was used to deposit one-micron thick DLC on these steel surfaces. The coating hardness was ~18–19GPa. Its adhesion on the steel substrate was measured by scratch testing and was found to be comparable to thick, adherent DLC coatings deposited by other methods

High antibacterial properties of nanodiamond doped DLC film

Las películas DLC se utilizan en muchas aplicaciones y las nanopartículas se utilizan como materiales dopantes en una gran cantidad de películas. En esta investigación, las películas DLC dopadas con nanodiamante se depositaron sobre sustratos de Ti6Al4V. El nanodiamante de detonación (DND) se agitó en hexano con un sonicador a 750 W para obtener una suspensión, que se introdujo mediante un proceso de evaporación en un reactor PECVD para producir películas de DLC dopadas continuamente con nanopartículas. Se utilizó una capa intermedia de silicio amorfo antes de depositar el DLC sobre el sustrato Ti6Al4V. Los resultados de la espectroscopia Raman mostraron películas con un contenido de hidrógeno de alrededor del 22%. Una prueba de rayado en la aleación Ti6Al4V mostró cargas críticas cercanas a 19 N, y la resistencia a la corrosión medida mediante polarización potenciodinámica mejoró con DLC dopado sobre la del sustrato desnudo.Escherichia coli , mostrando actividad antibacteriana cercana al 95% 6 h después del contacto directo con la película. Este resultado sugirió que el DLC es un material excelente para fines biomédicos. Después de 18 h de contacto directo con la película de DLC dopada, se observó una actividad antibacteriana cercana al 25%, lo que sugirió que los nanodiamantes son capaces de mantener sus propiedades antibacterianas y producir daño a las células de E. coliDLC films are used in many applications, and nanoparticles are being used as dopant materials in a large number of films. In this investigation, DLC films doped with nanodiamond were deposited on Ti6Al4V substrates. Detonation nanodiamond (DND) was stirred in hexane with a sonicator at 750 W to obtain a suspension, which was introduced by an evaporation process into a PECVD reactor to produce DLC films continuously doped with nanoparticles. An amorphous silicon interlayer was used before depositing the DLC on the Ti6Al4V substrate. Raman spectroscopy results showed films with hydrogen contents around 22%. A scratch test on the Ti6Al4V alloy showed critical loads close to 19 N, and corrosion resistance measured via potentiodynamic polarization was improved with doped DLC over that of the bare substrate. An antibacterial test was carried out with Gram-negative Escherichia coli, showing antibacterial activity close to 95% 6 h after direct contact with the film. This result suggested that DLC is an excellent material for biomedical purposes. After 18 h of direct contact with the doped DLC film, antibacterial activity close to 25% was observed, which suggested that nanodiamonds are able to maintain their antibacterial properties and produce damage to E. coli cells.Q1Grupo de Investigación en Diseño, Análisis y Desarrollo de Sistemas de Ingeniería -GIDA

Columnar Cvd Diamond Growth Structure On Irregular Surface Substrates

Columnar grain structure is always observed in CVD-diamond growth and is an important parameter to identify the morphology of thin and thick films. Structure defects, aspects of onset nucleation and film growth mechanisms can also be related to columnar growth. In this work we focused our attention on the columnar structure of CVD-diamond grown on irregular surfaces. We observed that there is a relationship among curvature radius of the substrate surface, the spread of the column volume and the growth rate of the diamond film. Growth rates on spherical surfaces of around 0.5 mm curvature radius have been observed to be up to three times bigger than the growth rates on planar surfaces. Also, the grain size distribution on planar and on the corner surfaces as a function of the growth rate has been studied. Characterization with scanning electron microscopy (SEM) and Raman scattering spectroscopy (RSS) has been performed. © 1995.41112551259Bachmann, van Enckevort, (1992) Diamond Relat. Mater., 1, p. 1021Koidl, Klages, (1992) Diamond Relat. Mater., 1, p. 1065Buckley-Golder, Collins, (1992) Diamond Relat. Mater., 1, p. 1083Lux, Haubner, Renard, (1992) Diamond Relat. Mater., 1, p. 1035Lux, Haubner, (1991) Diamond and Diamond-like Films and Coatings, NATO-ASI Ser. B, Physics, 266, p. 579. , 5th edn., Plenum, New YorkClausing, Heatherly, Specht, More, (1991) Int. Conf. Proc. on New Diamond Science and Technology, p. 575. , MRS, Pittsburgh, PABruckner, Mantyla, (1993) Diamond Relat. Mater., 2, p. 373Jin, Graebner, Tiefl, Kammlott, (1993) Diamond Relat. Mater., 2, p. 1038Wild, Heres, Koidl, (1990) J. Appl. Phys., 68, p. 973Trava-Airoldi, Rodrigues, Fukui, Baranauskas, <title>Characterization of diamond films deposited by hot-filament CVD using CF4 as doping gas by Raman spectroscopy, FTIR spectroscopy, and atomic force microscopy</title> (1992) SPIE Proc. Diamond Optics V, 1759, p. 87. , 5th ednVan der Drift, (1967) Philips Res. Rep., 2, p. 26

Friction Coefficient Measurements By Lfm On Dlc Films As Function Of Sputtering Deposition Parameters

Diamond-like carbon (DLC) coatings are widely used as protective overcoats on space junctions, magnetic media and magnetic head sliders in hard disk-drive systems, etc. In the present work, the friction coefficient of DLC films was investigated by lateral force microscopy (LFM) as a function of sputtering deposition parameters. The lateral force acts on the pyramidal tip attached to the end of the cantilever, due to friction or viscous forces, resulting in cantilever measurable torsion and deflection, related to the friction's magnitude. The relationship among data from friction coefficient distribution on DLC films surface with flow of precursor gases, surface composition, morphology structure, hardness and elastic module parameters was evaluated. Characterization techniques such as Raman scattering spectroscopy (RSS), X-ray photoelectron spectroscopy (XPS) and nanoindentation were used. The results have showed good agreement with the literature for DLC tribological parameters. © 2002 Elsevier Science B.V. All rights reserved.113-611351138Cunningham, J.M., Marirrodriga, C.G., (1995) Proceedings of the Sixth European Space Mechanisms and Tribology Symposium, p. 374. , Technopark, Zurich, Switzerland, ESA SPBriscoe, H.M., (1990) Tribol. Int, 23 (2), p. 67Spalvins, T., (1973) ASLE Trans, 1, p. 17Lifshitz, Y., (1999) Diamond Relat. Mater, 8, p. 1659Santos, L.V., Trava-Airoldi, V.J., Iha, K., Corat, E.J., Salvador, M.C., (2001) Diamond Relat. Mater, 10, p. 1049Maillat, M., Hintermann, H.E., (1990) Proceedings of the Fourth European on Space Mechanisms and Tribology Symposium, p. 299. , Canes, France (20-22 Sep 1989), ESA SPGrill, A., Patel, V., (1993) Diamond Relat. Mater, 2, p. 597Mogne, T.L., Donnet, C., Martin, J.M., Tonck, A., Millard, J.N., (1994) Vacuum Sci. Technol, 12 A (4), p. 1998Liu, E., Blanpain, B., Shia, X., Celis, J.-P., Tan, H.-S., Tay, B.-K., Cheah, L.-K., Ross, J.R., (1998) Surf. Coat. Technol, 106, p. 72Donnet, C., Belin, M., Auge, J.C., Martin, J.M., Grill, A., Patel, V., (1994) Surf. Coat. Technol, 68-69, p. 626Grill, A., (1999) J. Res. Dev. IBM-plasma Process, 1-2, p. 43Erlandsson, R., Hadziioannou, G., Mate, C.M., McClelland, G.M., Chiangs, S.J., (1988) Chem. Phys, 89 (8), p. 5190Prioli, R., Reigada, D.C., Freire, F.L., (1999) Appl. Phys. Lett, 75 (9), p. 1317Miyake, S., Kaneko, R., (1992) Thin Solids Films, 212, p. 256Mar-tines, E., Andujur, J.L., Polo, M.C., Esteve, J., Robertson, J., Milne, W.I., (2001) Diamond Relat. Mater, 10, pp. 145-152Marti, O., Colchero, J., Mlynek, J., (1990) Nanotechnol, 1, p. 141Meyer, E., Overney, R., Brodbeck, D., Howald, L., Ltithi, R., Frommer, J., Gtintherodt, H.J., (1992) Phys. Rev. Lett, 69 (12), p. 1777Neumeister, J.M., Ducker, W.A., (1994) Sci. Instrum, 68 (8), p. 2527Hu, J., Xiao, X.-D., Ogletree, D.F., Salmerom, M., (1995) Surf. Sci, 344, pp. 221-23

Biocompatibility Differences Between Dispersed And Vertically-aligned Carbon Nanotubes: An In Vitro Assays Review

An overview about carbon nanotube (CNT) production and quality parameters will be presented, as well a review of current literature about "in vitro"assays commonly used to evaluate the biocompatibility of CNT. The limits of colorimetric assays for CNTs evaluation will be discussed, using comparisons between dispersed CNT and CNT arrays. The influence of nanotopography and wettability of CNT scaffolds for cell adhesion will be shown. Studies carried out in our laboratories with vertically-aligned carbon nanotubes (VACNT) will also be presented. We have shown the interaction among CNT (VACNT) and four cell lines: mouse fibroblasts (L-929), mouse embryo fibroblast (C57/BL6) with or without green fluorescent protein (GFP) and human osteoblast (SaOS-2). The biocompatibility tests were performed with in vitro tests on raw-VACNT and after superficial modification by O2 plasma, which changes its hydrophobic character. The non-toxicity, cell viability, proliferation and cell adhesion were evaluated by: (i) 2-(4,5-dimethyl-2-thioazoly)-3,5-diphenyl-2H-tetrazolium bromide (MTT) assay; (ii) Lactate dehydrogenase (LDH) assay; (iii) neutral red (NR) assay; (iv) Scanning electron microscopy (SEM); and fluorescence microscopy. The influence of catalyst type, VACNT density and superficial modification were evaluated by morphological, structural and superficial techniques: SEM, Transmission electron microscopy (TEM), Raman spectroscopy, contact angle (CA) and X-Ray Photoelectron Spectroscopy (XPS). High cell viability, exceptional cell adhesion and preference were achieved. © 2009 by Nova Science Publishers, Inc. 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Influencia de las capas intermedias Ti x Si y Ti x Si / a-Si: H en la adherencia de recubrimientos de carbono tipo diamante

Se estudió el efecto de dos capas intermedias diferentes sobre la adherencia de los recubrimientos DLC al acero inoxidable AISI 316 L. Se depositaron capas intermedias de titanio-silicio (Ti x Si) y capas intermedias de titanio-silicio más silicio hidrogenado amorfo (Ti x Si / a-Si: H). Ti xLas capas intermedias de Si se cultivaron con tres espesores diferentes mediante la técnica de pulverización catódica de RF, mientras que las capas intermedias de a-Si: H y los recubrimientos DLC se depositaron utilizando un sistema DC-PECVD con una pantalla activa como cátodo adicional. La caracterización microestructural de la intercapa titanio-silicio se realizó mediante técnicas de difracción de rayos X (XRD) y espectroscopía de fotoelectrones de rayos X (XPS), y el análisis químico se realizó mediante espectroscopía de rayos X de energía dispersiva (EDS) , mientras que los recubrimientos DLC se estudiaron con espectroscopía Raman. El grado de adhesión de los recubrimientos DLC a sustratos de acero inoxidable AISI 316 L se analizó mediante mediciones de carga crítica y una prueba de indentación VDI 3198. Los resultados de XRD mostraron que las nuevas fases cristalinas no estaban presentes en el Ti xIntercapa de Si. Los espectros XPS mostraron un enlace entre el Si enlace sencilloFe y el Ti-Fe-O. Los resultados de adherencia mostraron que los recubrimientos DLC depositados usando Ti x Si con un espesor de 200 nm exhibieron un valor de carga crítica de 5 N, mientras que los recubrimientos con otros espesores se deslaminaron completamente cuando se aplicó la misma carga. Estos resultados sugirieron que la baja adhesión del revestimiento DLC se debió a los óxidos formados en la interfaz Ti x Si-DLC. Para el AISI 316 L / Ti xRecubrimiento Si / a-Si: H / DLC, se determinó una carga crítica de 26 N. La formación de siliciuro de titanio, siliciuro de hierro y carburo de silicio en las interfaces permitió un aumento en la fuerza de adhesión entre las capas intermedias. Los resultados de Raman mostraron que los recubrimientos DLC exhibieron buenas propiedades microestructurales y contenidos de hidrógeno alrededor del 28% at. Los recubrimientos DLC también exhibieron una dureza de 25 GPa.The effect of two different interlayers on the adherence of DLC coatings to AISI 316 L stainless steel was studied. Titanium-silicon (TixSi) interlayers and titanium-silicon plus amorphous hydrogenated silicon (TixSi/a-Si:H) interlayers were deposited. TixSi intermediate layers were grown with three different thicknesses via the RF sputtering technique, while a-Si:H interlayers and DLC coatings were deposited using a DC-PECVD system with an active screen as an additional cathode. The microstructural characterization of the titanium-silicon interlayer was carried out through the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques, and chemical analysis was done by means of energy-dispersive X-ray spectroscopy (EDS), while DLC coatings were studied with Raman spectroscopy. The degree of adhesion of the DLC coatings to AISI 316 L stainless steel substrates was analyzed using critical load measurements and a VDI 3198 indentation test. XRD results showed that new crystalline phases were not present in the TixSi interlayer. XPS spectra showed a bond between the Sisingle bondFe and the Ti-Fe-O. The adherence results showed that the DLC coatings deposited using TixSi with 200 nm thickness exhibited a critical load value of 5 N, while the coatings with other thicknesses were completely delaminated when the same load was applied. These results suggested that the low adhesion of the DLC coating was due to the oxides formed at the TixSi-DLC interface. For the AISI 316 L/TixSi/a-Si:H/DLC coating, a critical load of 26 N was determined. The formation of titanium silicide, iron silicide, and silicon carbide in the interfaces allowed an increase in the adhesion strength between the interlayers. The Raman results showed that the DLC coatings exhibited good microstructural properties and hydrogen contents around 28 at.%. The DLC coatings also exhibited a hardness of 25 GPa.Q2Grupo de Investigación en Diseño, Análisis y Desarrollo de Sistemas de Ingeniería -GIDA