[show abstract][hide abstract] ABSTRACT: This paper reports the results of incorporating silver nanoparticles in DLC films to improve the solid lubricant's lifetime when atomic oxygen bombardment is present in high vacuum environments as are encountered in space. For this, etching experiments were performed in oxygen plasma operated at low pressure. DLC films were deposited on different metallic substrates and on silicon (100) with thin amorphous silicon interlayer by using a Pulsed DC-PECVD discharge. The main goals were to obtain a low etching rate in an atomic oxygen atmosphere, a low friction coefficient, a low total stress, a high degree of hardness, and very high adherence to the substrate in depositions. During etching experiments, the films were submitted to oxygen ions with energy of ∼ 84 eV in order to evaluate the process of wear of the surface in a short period (4 min). The mass spectrometry analysis shows a reduction of the volatile product species (C+, CO+ and CO2+) in the etching environment for samples with more silver nanoparticles. The results were in agreement with profilometry measurements. The results confirm DLC films are more wear resistant against oxygen attack when silver nanoparticles are incorporated. Also, a consistent method for obtaining nanoparticle size and density control will be discussed.
[show abstract][hide abstract] ABSTRACT: The coating of orthopedic prostheses with diamond like-carbon (DLC) has been actively studied in the past years, in order to improve mechanical, tribological properties and promote the material's biocompatibility. Recently, the incorporation of crystalline diamond nanoparticles into the DLC film has shown effective in combating electrochemical corrosion in acidic medias. This study examines the material's biocompatibility through testing by LDH release and MTT, on in vitro fibroblasts; using different concentrations of diamond nanoparticles incorporated into the DLC film. Propounding its potential use in orthopedics in order to increase the corrosion resistance of prostheses and improve their relationship with the biological environment.
[show abstract][hide abstract] ABSTRACT: The combination of low friction, wear resistance, high hardness, biocompatibility and chemical inertness makes diamond-like carbon (DLC) films suitable in a numerous applications in biomedical engineering. The cell viability and adhesion of L929 mouse fibroblasts was investigated using two different colorimetric assays: (i) 2-(4,5-dimethyl-2-thiazolyl)-3,5-diphenyl-2H-tetrazolium bromide (MTT), and (ii) lactate dehydrogenase (LDH). The films were growth on 316L stainless steel substrates using plasma enhanced chemical vapor deposition technique from a dispersion of TiO2 nanopowder in hexane. The increasing concentration of TiO2 nanoparticles in DLC films enhanced the mitochondrial activity and decreases the LDH activity on these samples. Fluorescence and scanning electron microscopy corroborate the results. These experiments show the potential use of DLC and TiO2-DLC films in biomedical applications.
[show abstract][hide abstract] ABSTRACT: We have analyzed the adhesion of mouse embryonic fibroblasts (MEFs) genetically modified by green fluorescence protein (GFP) gene cultured on vertically-aligned carbon nanotubes (VACNTs) after 6 days. The VACNTs films grown on Ti were obtained by microwave plasma chemical vapor deposition process using Fe catalyst and submitted to an oxygen plasma treatment, for 2 min, at 400 V and 80 mTorr, to convert them to superhydrophilic. Cellular adhesion and morphology were analyzed by scanning electron, fluorescence microscopy, and thermodynamics analysis. Characterizations of superhydrophilic VACNTs films were evaluated by contact angle and X-Ray Photoelectron Spectroscopy. Differences of crowd adhered cells, as well as their spreading on superhydrophilic VACNTs scaffolds, were evaluated using focal adhesion analysis. This study was the first to demonstrate, in real time, that the wettability of VACNTs scaffolds might have enhanced and differential adherence patterns to the MEF-GFP on VACNTs substrates.
Materials Science and Engineering: C. 01/2011; 31:1505-1511.
[show abstract][hide abstract] ABSTRACT: Crystalline diamond (CD) particles have been incorporated in diamond-like carbon (DLC) film structure in order to improve DLC electrochemical corrosion resistance. This paper shows the investigation of CD-DLC friction behavior according to the CD average sizes and concentration. The films were growth over 304 stainless steel using plasma enhanced chemical vapor deposition. The response surface methodology was used to develop a mathematical modeling of friction for these films, using the experimental results, in order to identify parameters that control friction and construct tribological maps according to the CD average sizes. The presence of bigger CD particles (250 and 500nm) increased the film roughness. Films with CD particles of 4nm presented the most homogeneous friction map, with minor variation in friction coefficient with the increase/decrease of load and sliding speed even when the CD concentration increase. This result suggests that in CD-DLC films containing CD particles of 4nm average size, the nanoparticles are better incorporated in DLC structure due to its average size (4nm) that is near than DLC grain size and could occupy the nanospaces between DLC grains.
[show abstract][hide abstract] ABSTRACT: Nanocrystalline diamond (NCD) particles are incorporated into diamond-like carbon (DLC) films in order to prevent NCD-DLC electrochemical corrosion. In the current paper, tribological behavior of NCD-DLC films under aggressive solutions is discussed. DLC and NCD-DLC coated steel disks and coated and uncoated steel ball were used under rotational sliding conditions. Raman scattering spectroscopy analyzed the film's atomic arrangements and graphitization level before and after tribocorrosion tests. The NCD-DLC films confirmed to be effective in the corrosion wear resistance under corrosive environments. The results pointed that NCD-DLC films are promising corrosion protective coating in aggressive solutions for many applications.
Surface and Coatings Technology. 01/2011; 206:434-439.
[show abstract][hide abstract] ABSTRACT: This paper discusses the seawater and saline solutions effects on the tribological behavior of diamond-like carbon (DLC) films. The adsorption of Fe on DLC surface is one of the mechanisms that is believed to be the cause of the decrease in dispersive component of the surface energy and increase of the ID/IG ratio leading to low friction coefficient and wear rate under corrosive environments. Tribological behaviors DLC films were experimentally evaluated under corrosive environments by using steel ball and DLC coated steel flat under rotational sliding conditions. The DLC films were prepared on 440 stainless steel disks by DC-pulsed PECVD using methane as a precursor gas. Two different set of tribological system was assembled, one when the liquids and the pairs were put inside of a stainless steel vessel and others inside of a PTFE. Every tribological test was performed under 10 N normal load120 mms− 1 of sliding speed. The friction coefficients were evaluated during 1000 cycles.Research Highlights► The amount of iron mass residual was inversely proportional to the wear rate. ► The DLC showed dependence behavior with salt concentration of saline solutions. ► The tribofilm on DLC surface increased the disorder of DLC film structure. ► The iron oxide residual decreased the dispersive component of DLC surface energy.
[show abstract][hide abstract] ABSTRACT: Diamond-like carbon films have unique properties for biological and medical applications due to their excellent biocompatibility, chemical inertness, and superior mechanical properties. In order to attend biomedical applications, there is an increasing interest in developing antibacterial coatings. In this paper, we investigated the bactericidal properties of diamond-like carbon films produced using plasma enhanced chemical vapor deposition. The films were deposited over 316L stainless steel substrates using a pulsed directly current discharge of methane gas. Diamond-like carbon structural quality was evaluated using Raman scattering spectroscopy. The bacterial adhesion and bactericidal activity of the coating was evaluated against Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Salmonella typhimurium ATCC 14028 and Staphylococcus aureus ATCC 25923. These tests show diamond-like carbon bactericidal activity ranged between 25 and 55%, depending on the kind of bacteria. The bacterial adhesion on diamond-like carbon surface was influenced by its structure, chemical bonds and hydrogen content. The low surface roughness did not have decisive effect on its antibacterial performance.
[show abstract][hide abstract] ABSTRACT: Superhydrophilic vertically aligned multi-walled carbon nanotubes were used as substrate to direct hydroxyapatite
electrodeposition. Conventional Nickel/Titanium alloys were used for comparison. Results show that the bath
temperature and the hydrophobicity control affect the hydroxyapatite/carbon nanotube composites obtained by
electrodeposition. These results were proved using X-ray diffraction, Energy-dispersive X-ray spectroscopy, field
emission gun scanning electron microscopy and Raman spectroscopy.
Journal of Nanomedicine & Nanotechnology. 01/2011; 8:1-6.
[show abstract][hide abstract] ABSTRACT: Diamond-like carbon (DLC) films have been the focus of extensive research in recent years due to its potential application as surface coatings on biomedical devices. It has been already reported that fluorine (F) could increase DLC antibacterial activity. In this paper we investigated the antibacterial activity of fluorinated-DLC (F-DLC) films with various F contents and its correlation with bacterial adhesion mechanism according to thermodynamic theory. F-DLC was grown on a 316L stainless steel substrate using plasma enhanced chemical vapor deposition (PECVD) by varying the ratio of carbon tetrafluoride and methane. The antibacterial tests were performed against E. coli and the influence of F content on composition, surface energy, stress and surface roughness was also investigated. As F content increased, F-DLC films presented lower stress and surface free energy. In addition, the roughness values increased and Raman G-band peak position shifted to higher wave numbers. The results show that bacterial adhesion to F-DLC films decreases with increasing F content and work of adhesion, which is consistent with the thermodynamic theory. PECVD is a simple technique to produce F-DLC films to be used in biomedical applications. Pages: 2986-2990
[show abstract][hide abstract] ABSTRACT: Crystalline diamond (CD) particles are incorporated into diamond-like carbon (DLC) films in order to prevent CD–DLC electrochemical corrosion. In this paper, the influence of the diamond particle sizes on the electrochemical corrosion resistance of CD–DLC films was investigated. The films were grown over 304 stainless steel using plasma enhanced chemical vapor deposition. CD particles with 4nm, 250nm, 500nm and 2–3µm in diameter were incorporated into DLC during the deposition process. The investigation of CD–DLC electrochemical corrosion behavior was performed using potentiodynamic method. The results show that both protection efficiency and impedance increase with the decrease of ID/IG ratio. It means the increase of sp3 bonds in DLC films reduces its electrochemical corrosion, improving the electrochemical protection efficiency and the impedance. Our results pointed out that CD–DLC films are promising corrosion protective coatings in aggressive solutions.
[show abstract][hide abstract] ABSTRACT: Diamond-like carbon (DLC) film as a solid lubricant coating represents an important area of investigation related to space devices. The environment for such devices involves high vacuum and high concentration of atomic oxygen. The purpose of this paper is to study the behavior of silver-incorporated DLC thin films against oxygen plasma etching. Silver nanoparticles were produced through an electrochemical process and incorporated into DLC bulk during the deposition process using plasma enhanced chemical vapor deposition technique. The presence of silver does not affect significantly DLC quality and reduces by more than 50% the oxygen plasma etching. Our results demonstrated that silver nanoparticles protect DLC films against etching process, which may increase their lifetime in low earth orbit environment.
Thin Solid Films 08/2009; 517(19):5739–5742. · 1.60 Impact Factor
[show abstract][hide abstract] ABSTRACT: Diamond-like carbon (DLC) films have been the focus of extensive research in recent years due to their potential applications as surface coatings on biomedical devices. Titanium dioxide (TiO2) in the anatase crystalline form is a strong bactericidal agent when exposed to near-UV light. In this work we investigate the bactericidal activity of DLC films containing TiO2 nanoparticles. The films were grown on 316L stainless-steel substrates from a dispersion of TiO2 in hexane using plasma-enhanced chemical vapor deposition. The composition, bonding structure, surface energy, stress, and surface roughness of these films were also evaluated. The antibacterial tests were performed against Escherichia coli (E. coli) and the results were compared to the bacterial adhesion force to the studied surfaces. The presence of TiO2 in DLC bulk was confirmed by Raman spectroscopy. As TiO2 content increased, I(D)/I(G) ratio, hydrogen content, and roughness also increased; the films became more hydrophilic, with higher surface free energy and the interfacial energy of bacteria adhesion decreased. Experimental results show that TiO2 increased DLC bactericidal activity. Pure DLC films were thermodynamically unfavorable to bacterial adhesion. However, the chemical interaction between the E. coli and the studied films increased for the films with higher TiO2 concentration. As TiO2 bactericidal activity starts its action by oxidative damage to the bacteria wall, a decrease in the interfacial energy of bacteria adhesion causes an increase in the chemical interaction between E. coli and the films, which is an additional factor for the increasing bactericidal activity. From these results, DLC with TiO2 nanoparticles can be useful for producing coatings with antibacterial properties.
Journal of Colloid and Interface Science 08/2009; 340(1):87-92. · 3.17 Impact Factor
[show abstract][hide abstract] ABSTRACT: Diamond-like carbon (DLC) films can be used in a numerous industrial applications, including biomedical coatings with bactericidal properties. It has been demonstrated that DLC surface can be modified with oxygen plasma treatment. The purpose of this paper is to study the wettability and bactericidal activity of oxygen plasma-treated DLC films produced by plasma enhanced chemical vapor deposition technique. The sp3/sp2 ratio increased after the treatment due to the increase in the generation of the unstable carbon bonds caused by the energetic ions, especially O–H group. The treated DLC surface becomes superhydrophilic and rougher, although the roughness values are still lower. DLC antibacterial activity did not increased with plasma treatment. Therefore, oxygen plasma treatment can be used to make superhydrophilic DLC but not to increase its bactericidal properties.
[show abstract][hide abstract] ABSTRACT: Diamond-like carbon (DLC) films have been use in numerous industrial applications due to its mechanical properties such as low friction coefficient, high hardness, and high adherence on different substrate materials. It has been demonstrated that the DLC surface can be modified with oxygen plasma treatment. The purpose of this paper is to study two kinds of surface treatments (atmospheric and low pressures) using oxygen gas for different etching exposure times in DLC films. Plasma durability along the time was also evaluated. DLC films were deposited using plasma enhanced chemical vapor deposition technique. The properties of DLC treated for both techniques in different exposure times were investigated through Raman, AFM and contact angle measurements. D band position slightly shifts toward lower wave numbers after oxygen plasma etching treatment whilst the surface becomes rougher, although the roughness values are still lower. A conventional wetting contact angle method was used to study the surface properties of DLC films with different treatments. The wetting contact angle reduced significantly due to the increase of carbon–oxygen sites on the surface.
Surface and Coatings Technology 01/2009; 204:64-68. · 1.94 Impact Factor
[show abstract][hide abstract] ABSTRACT: Diamond-like carbon (DLC) films have been the focus of extensive research in recent years due to its potential application as surface coatings on biomedical devices. Doped carbon films are also useful as biomaterials. As silver (Ag) is known to be a potent antibacterial agent, Ag–DLC films have been suggested to be potentially useful in biomedical applications. In this paper, DLC films were growth on 316L stainless steel substrates by using Plasma Enhanced Chemical Vapour Deposition (PECVD) technique with a thin amorphous silicon interlayer. Silver colloidal solution was produced by eletrodeposition of silver electrodes in distilled water and during the deposition process it was sprayed among each 25 nm thickness layer DLC film. The antibacterial activity of DLC, Ag–DLC and silver colloidal solution were evaluated by bacterial eradication tests with Escherichia coli (E. coli) at different incubation times. With the increase of silver nanoparticle layers in Ag–DLC, the total compressive stress decreased significantly. Raman spectra showed the film structure did not suffer any substantial change due to the incorporation of silver. The only alteration suffered was a slightly reduction in hardness. DLC and Ag–DLC films demonstrated good results against E. coli, meaning that DLC and Ag–DLC can be useful to produce coatings with antibacterial properties for biomedical industry.
Diamond and Related Materials 01/2009; · 1.71 Impact Factor