Comparative Surface and Nano-Tribological Characteristics of Nanocomposite Diamond-Like Carbon Thin Films Doped by

Abstract In this study we have deposited silver-containing hydrogenated and hydrogen-free diamondlike carbon (DLC) nanocomposite thin films by plasma immersion ion implantation-deposition methods. The surface and nano-tribological characteristics were studied by x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and nano-scratching experiments. The silver doping was found to have no measurable effect on sp 2 -sp 3 hybridization of the hydrogenated DLC matrix and only a slight effect on the hydrogen-free DLC matrix. The surface topography was analyzed by surface imaging. High-and low-order roughness determined by AFM characterization was correlated to the DLC growth mechanism and revealed the smoothing effect of silver. The nano-tribological characteristics were explained in terms of friction mechanisms and mechanical properties in correlation to the surface characteristics. It was discovered that the adhesion friction was the dominant friction mechanism; the adhesion force between the scratching tip and DLC surface was decreased by hydrogenation and increased by silver doping

Particle distribution, film formation and wear performance of brush plated Ni/WC

Nickel-matrix composite coatings with tungsten carbide particles were produced by brush electroplating using different current densities and materials of the brush. Non-abrasive materials and high current densities produce coatings with high particle content and non-uniform dispersion. Abrasive wear testing showed premature coating failure in areas with high particle concentrations (>21.3 at.% of W). Changes to the solution flow direction were undertaken to decrease ‘solution pooling’, as it was related to areas with excessive particle content. This, together with the use of abrasive brushes at lower current densities, gives Ni/WC coatings with a low and narrow composition range (from 13.2 ± 4.8 to 2.8 ± 0.8 at.% of W). Such optimized coatings minimized premature coating failure and improved the wear resistance to 1.8–4.4 times that of the original nickel matrix, achieving values similar to hard chrome coatings tested under the same conditions. Unlike other brush plated composite coatings, changes in coating morphology are not heavily influenced by processing parameters, but are sensitive to the presence of WC particles

Functional evaluation and testing of a newly developed Teleost’s Fish Otolith derived biocomposite coating for healthcare

Polymers such as polycaprolactone (PCL) possess biodegradability, biocompatibility and affinity with other organic media that makes them suitable for biomedical applications. In this work, a novel biocomposite coating was synthesised by mixing PCL with layers of calcium phosphate (hydroxyapatite, brushite and monetite) from a biomineral called otolith extracted from Teleost fish (Plagioscion Squamosissimus) and multiwalled carbon nanotubes in different concentrations (0.5, 1.0 and 1.5 g/L). The biocomposite coating was deposited on an osteosynthesis material Ti6Al4V by spin coating and various tests such as Fourier transformation infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), scratch tests, MTT reduction cytotoxicity, HOS cell bioactivity (human osteosarcoma) by alkaline phosphatase (ALP) and fluorescence microscopy were performed to comprehensively evaluate the newly developed biocoating. It was found that an increase in the concentration of carbon nanotube induced microstructural phase changes of calcium phosphate (CP) leading to the formation of brushite, monetite and hydroxyapatite. While we discovered that an increase in the concentration of carbon nanotube generally improves the adhesion of the coating with the substrate, a certain threshold exists such that the best deposition surfaces were obtained as PCL/CP/CNT 0.0 g/L and PCL/CP/CNT 0.5 g/L

Probe geometry and surface roughness effects in microscale impact testing of WC-Co

Depth-sensing repetitive microimpact tests have been performed on cemented carbide cutting tool inserts with spheroconical diamond probes with end radii of 8, 20 and 100 µm. Results were strongly dependent on the probe radius and applied load. At higher load, there was a transition to a faster damage rate marking the onset of more variability in rate and in the residual depth of the impact crater when using 8 and 20 µm probes. SEM images show the breakup of the WC skeleton at the periphery of the contact zone. Lower surface roughness slowed the initial damage rate at a higher load but did not significantly influence the final crater depth. The load-dependent fatigue mechanism displayed by the cemented carbide also has implications for the study and optimization of coatings when these are deposite

Functionalization of Hydrogen-free Diamond-like Carbon Films using Open-air Dielectric Barrier Discharge Atmospheric Plasma Treatments

A dielectric barrier discharge (DBD) technique has been employed to produce uniform atmospheric plasmas of He and N2 gas mixtures in open air in order to functionalize the surface of filtered-arc deposited hydrogen-free diamond-like carbon (DLC) films. XPS measurements were carried out on both untreated and He/N2 DBD plasma treated DLC surfaces. Chemical states of the C 1s and N 1s peaks were collected and used to characterize the surface bonds. Contact angle measurements were also used to record the short- and long-term variations in wettability of treated and untreated DLC. In addition, cell viability tests were performed to determine the influence of various He/N2 atmospheric plasma treatments on the attachment of osteoblast MC3T3 cells. Current evidence shows the feasibility of atmospheric plasmas in producing long-lasting variations in the surface bonding and surface energy of hydrogen-free DLC and consequently the potential for this technique in the functionalization of DLC coated devices

Composite coatings incorporating solid lubricant phases

The concept of incorporating a solid lubricant, silver (Ag), within a hard carbide film for vacuum tribology applications is investigated in this paper. SiC/Ag and HfC/Ag films were deposited by magnetron cosputtering at 200 degreesC onto Si and 440C steel substrates. The composition, phase structure, and morphology in these films was examined using x-ray diffraction, scanning electron microscopy, and x-ray photoelectron spectroscopy. The microstructural analysis showed that Ag was incorporated both within and on the surface of the films. There was a strong tendency for Ag to segregate to the film surface. Vacuum tribology tests were conducted using a ball-on-disk test in a vacuum of 1.33 muPa with a 1 N load for 10 000 cycles. For both the SiC/Ag and HfC/Ag films, the average friction coefficients were reduced when sufficient Ag was present. These tests show that carbide-Ag composite films hold promise for vacuum tribology applications

Magnetron sputter deposition of WC-Ag and TiC-Ag coatings and their frictional properties in vacuum environments

Thin films of WC-Ag and TiC-Ag were deposited by magnetron sputtering for the purpose of analyzing their tribological properties in vacuum. X-ray diffraction was used to determine structural properties, and energy dispersive X-ray analysis was used to determine the relative atomic content of silver in the films. Pin on disk friction tests were performed to obtain the coefficient of friction in vacuum. The deposited films showed a structure containing separate carbide/silver phases, as was desired for providing both high wear resistance and low friction. The tribological test results show a significant decrease in the friction coefficient for both TiC-Ag and WC-Ag, to a minimum value of 0.2, with increasing silver content. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved

Microstructure and vacuum tribology of TiC-Ag composite coatings deposited by magnetron sputtering-pulsed laser deposition

Composite titanium carbide-silver films have been co-deposited by magnetron sputtering-pulsed laser deposition (MSPLD) to study their friction and wear properties in vacuum. The films deposited were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), The silver content in the films ranged from 6 to 46 at.%. Structural characterization of the films revealed that Ag had a nano-crystalline structure when dispersed in the film, but larger crystallites of Ag (similar to50-200 nm) also formed on the surface. Films with higher Ag contents showed evidence of higher diffusion rates, leading to a coarser structure and greater surface coverage. Pin-on-disk friction tests were performed under vacuum to observe the friction and wear behavior of these films. Friction was lower with higher Ag content, but wear was higher; the optimal Ag concentration was found to be 15%. SEM images from the surface of the films and wear tracks were obtained to understand the morphology of this type of composite ceramic coating, and revealed Ag layers in the wear track elongated in the direction of wear. Based on these results, the significance of silver as a friction-reducing agent in vacuum environments was demonstrated. (C) 2002 Elsevier Science B.V. All rights reserved

APPLICATIONS OF INTEGRATED SOCIAL COGNITIVE THEORIES IN PREDICTING AND CHANGING HEALTH BEHAVIOR

The design of efficient and stable solar selective coatings for Concentrating Solar Power (CSP) central receivers requires a comprehensive knowledge about the incorporated materials. In this work solar selective coatings were grown by filtered cathodic vacuum arc (FCVA) deposition. The complete stacks consist of an infrared reflection layer, an absorber layer of C:ZrC nanocomposites and an antireflection layer. The Carbon-transition metal nanocomposites were studied as absorber materials because they show appropriate optical properties, i.e. high absorption in the solar region and low thermal emittance. Furthermore metal carbides are thermally and mechanically stabile in air at high temperatures. In order to optimize the absorber layer, the metal content was controlled by adjusting the pulse ratio between the two arc sources. The elemental composition of the absorber layers was determined by Ion Beam Analysis. X-Ray diffraction (XRD) measurements show the formation of metal carbides when the metal content is high enough. The optical properties of the deposited coatings were characterized by spectroscopic ellipsometry (SE). The reflectance spectra of the complete selective coating were simulated with the optical software CODE. Bruggeman effective medium approximation (EMA) was employed to average the dielectric functions of the two components which compose the nanocomposite in the absorber layer. Good agreement was found between simulated and measured reflectance spectra of the solar selective multilayer

Effect of silver on the phase transition and wettability of titanium oxide films

The effect of silver on the phase transition and microstructure of titanium oxide films grown by pulsed cathodic arc had been investigated by XRD, SEM and Raman spectroscopy. Following successive thermal annealing up to 1000 °C, microstructural analysis of annealed Ag-TiO films reveals that the incorporation of Ag nanoparticles strongly affects the transition temperature from the initial metastable amorphous phase to anatase and stable rutile phase. An increase of silver content into TiO matrix inhibits the amorphous to anatase phase transition, raising its temperature boundary and, simultaneously reduces the transition temperature to promote rutile structure at lower value of 600 °C. The results are interpreted in terms of the steric effects produced by agglomeration of Ag atoms into larger clusters following annealing which hinders diffusion of Ti and O ions for anatase formation and constrains the volume available for the anatase lattice, thus disrupting its structure to form rutile phase. The effect of silver on the optical and wetting properties of TiO was evaluated to demonstrate its improved photocatalytic performance.This work was supported by the State Secretary of Research, Development and Innovation of Spain through the FUNCOAT project, within the program CONSOLIDER INGENIO 2010 (ref. CSD2008-00023)