|
| ||
|
|
||
Carbon Coatings (carbon + coating)
Selected AbstractsZirconia,Silica,Carbon Coatings on Ceramic FibersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2004Emmanuel E. Boakye Precursors for zircon,carbon mixtures were made to coat fibers for ceramic-matrix composites. Precursors were characterized using XRD, TGA, and DTA. Zircon formed from vanadium- or lithium-doped precursors after heat treatments at ,900°C in air, but it did not form at 1200°,1400°C in argon when large amounts of carbon were added. Some precursors were used to coat NextelÔ 720 and Hi-NicalonÔ fibers. The coatings were characterized using SEM and TEM, and coated-fiber tensile strengths were measured. Although zircon formed in powders, only tetragonal-zirconia,silica mixed phases formed in fiber coatings at 1200°C in air. Loss of vanadium oxide flux to the fibers may have caused the lack of conversion to zircon. The strengths of the coated fibers were severely degraded after heat treatment at ,1000°C in air, but not in argon. The coated fibers were compared with zirconia,carbon-coated fibers made using similar methods. Mechanisms for fiber strength degradation are discussed. [source] Gas Phase Modification of Superhard Carbon Coatings Deposited by Pulsed DC-Arc-ProcessPLASMA PROCESSES AND POLYMERS, Issue S1 2009Werner Grimm Abstract The pulsed vacuum arc discharge (pulsed arc) is the most efficient PVD technology for deposition of hard amorphous carbon coatings on tools and machinery parts. Due to the pulsed arc discharge a stable evaporation process and the efficient deposition of hydrogen-free a-C type coatings is possible. This paper shows that the pulsed arc enables the deposition of ta-C and modified a-C coatings with interesting coating properties in a wide pressure range of argon, acetylene and ammonia gas atmosphere. Coatings with different gas flow rates of these gases were deposited on steel substrates. The coating properties were characterized by using different analytical methods for determination of structure, hardness, friction and wear behaviour. The changes of film properties in dependence of the kind and the rate of gas flow are compared and discussed. [source] Amorphous Carbon Coatings Inhibit Crystalline Biofilm Formation on Urological ImplantsPLASMA PROCESSES AND POLYMERS, Issue S1 2007Lisa Kleinen Abstract Biofilm formation on urological stents remains a major complication in patient care. The study focuses on the ability of different plasma-deposited amorphous carbon coatings (a-C:H) to inhibit encrustation and to reduce implant-related side effects. Film forming particle flux was controlled by variation of precursor gases, pressure and RF-power resulting in different electrochemical and topological surface properties. Optical contact angle measurements were performed to determine the surface free energies of the films. Investigations on crystal adhesion and biofilm formation were performed in vitro and in vivo. Encrustation tendency was remarkably reduced by a-C:H. Compared to commercial stents, the indwelling time could be distinctly prolonged as the implanted stents remained biofilm-free. [source] Monte Carlo Study of Quantitative Electron Probe Microanalysis of Monazite with a Coating Film: Comparison of 25 nm Carbon and 10 nm Gold at E0= 15 and 25 keVGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 2 2007Takenori Kato simulation par la méthode de Monte Carlo; microanalyse par sonde électronique (EPMA); analyse quantitative; film de revêtement; monazite Carbon (25,30 nm in thickness) is the most common coating material used in the electron probe microanalysis (EPMA) of geological samples. A gold coating is also used in special cases to reduce the surface damage by electron bombardment. Monte Carlo simulations have been performed for monazite with a 25 nm carbon and a 10 nm gold coating to understand the effect of a coating film in quantitative EPMA at E0= 15 keV and 25 keV. Simulations showed that carbon-coated monazite gave the same depth distribution of the generated X-rays in the monazite as uncoated monazite, whilst gold-coated monazite gave a distorted depth distribution. A 10 nm gold coating was 1.06 (15 keV) and 1.05 (25 keV) times higher in k -ratio between monazite and pure thorium than a 25 nm carbon coating at an X-ray take-off angle of 40 degrees. Thus, a 10 nm gold coating is a possible factor contributing to inaccuracy in quantitative EPMA of monazite, while a 25 nm carbon coating does not have a significant effect. Le carbone, avec des épaisseurs de 25 à 30 nm, est le matériel de dépôt le plus fréquemment utilisé en microanalyse par sonde électronique (EPMA) d'échantillons géologiques. Un dépôt d'or est aussi utilisé dans des cas spécifiques, pour réduire les dommages causés à la surface par le bombardement d'électrons. Des simulations par la méthode de Monte Carlo ont été effectuées pour une monazite recouverte d'une couche de carbone de 25 nm et d'une couche d'or de 10 nm, dans le but de comprendre l'effet du dépôt dans les mesures quantitatives à l'EPMA, à E0= 15 keV et 25 keV. Les simulations ont montré que la monazite recouverte de carbone avait la même distribution en profondeur de rayons X générés qu'une monazite non recouverte, tandis que la monazite recouverte d'or avait une distribution en profondeur déformée. Le dépôt de 10 nm d'or avait un k -ratio qui était 1.06 (pour 15 keV) et 1.05 (pour 25 keV) fois plus important pour la monazite et du thorium pur que le dépôt de 25 nm de carbone dans le cas d'un angle de sortie des rayons X de 40 degrés. En conséquence un dépôt d'or de 10 nm est un facteur possible d'inexactitude lors de mesures quantitatives de monazites par EPMA, alors qu'un dépôt de carbone de 25 nm n'a pas d'effet significatif sur la mesure. [source] Processing of Carbon Nanofiber Reinforced ZrB2 Matrix Composites for Aerospace Applications,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Jorge Barcena Ceramic matrix composites (CMCs) based on zirconium diboride (ZrB2) reinforced by vapor grown carbon nanofibers are a potential constituent of reusable thermal protection systems. A manufacturing procedure was devised that involved the fabrication of thin films by tape casting to obtain a layer that could be integrated into a more complex system. Higher thermal conductivities and improved toughness can be expected for nanofiber additions, as compared to the matrix alone. Consolidation by hot-pressing was more effective than pressureless sintering, in terms of the final relative density and flatness of specimens. Examination of microstructures showed that few carbon nanofibers were present in the matrix after consolidation by sintering, which was attributed to a reaction between the nanofibers and zirconium oxide present on the surface of the ZrB2 powder. As a solution, oxygen impurities from the boride powders were removed by reduction with carbon coatings derived from phenolic resin. The deleterious reaction was avoided, but residual carbon remained at the grain boundaries, likely from decomposition of the binder. The use of an alternative binder (PMMA vs. PVB) will be used in future studies to reduce the residual carbon content. Further, consolidation by Spark Plasma Sintering (SPS) will be explored to further reduce the reaction of surface oxides with the nanofibers. Finally, characterization of the microstructure at the nanometric level and further determination of the mechanical and thermal properties will be conducted as part of future studies. [source] Morphology and Growth Process of Carbon Films Prepared by Microwave,/,Radio Frequency Plasma Assisted CVD,ADVANCED ENGINEERING MATERIALS, Issue 7 2008W. Kaczorowski In this work the carbon coatings created by microwave/radio frequency plasma assisted chemical vapour deposition method were investigated. The deposition parameters were optimized in order to obtain homogeneous carbon coatings on such different substrates as AISI 316L steel and silicon. The MW/RF PACVD technique is promising for many different types of applications. [source] Tribochemistry of tetrahedral hydrogen-free amorphous carbon coatings in the presence of OH-containing lubricantsLUBRICATION SCIENCE, Issue 2 2008C. Matta Abstract Diamond-like carbon (DLC) films are gaining attention for its use in a wide range of tribological applications because of their low friction coefficient and high wear resistance. Recently, ultra-low friction or superlubricity as low as 0.006 has been observed between hydrogen-free DLC films lubricated with oil containing a glycerol mono-oleate (GMO) additive. Consequently, there are many efforts to understand their detailed tribological behaviour. In this study, first, a characterisation of a pristine hydrogen-free tetrahedral amorphous DLC coating (denoted as ta-C) is presented. The technique used for ta-C characterisation is the energy-filtered transmission electron microscopy studied on a focus ion beam cross section of the coating. Then, to simulate the action of GMO, which is used as an additive in engine oils, and to understand its mechanism of action in boundary lubrication conditions, simple and shorter molecules such as pure glycerol and hydrogen peroxide are used in friction tests. These two molecules and GMO have the same alcohol chemical function. Friction tests in the presence of pure glycerol and hydrogen peroxide are presented. Moreover, to understand the properties of these two molecules, the overtone of GMO and their reaction mechanism in boundary lubrication, liquid phase lubrication was simulated by gas phase lubrication. Results show that very low friction coefficients are obtained with no apparent wear. Finally, the mechanisms of ultra-low friction are investigated by the wetting method and the X-ray photoelectron spectroscopy (XPS) technique. These two techniques are used to identify the physical (wetting method) and chemical (XPS) changes occurring at the ta-C surface after friction. Copyright © 2007 John Wiley & Sons, Ltd. [source] Gas Phase Modification of Superhard Carbon Coatings Deposited by Pulsed DC-Arc-ProcessPLASMA PROCESSES AND POLYMERS, Issue S1 2009Werner Grimm Abstract The pulsed vacuum arc discharge (pulsed arc) is the most efficient PVD technology for deposition of hard amorphous carbon coatings on tools and machinery parts. Due to the pulsed arc discharge a stable evaporation process and the efficient deposition of hydrogen-free a-C type coatings is possible. This paper shows that the pulsed arc enables the deposition of ta-C and modified a-C coatings with interesting coating properties in a wide pressure range of argon, acetylene and ammonia gas atmosphere. Coatings with different gas flow rates of these gases were deposited on steel substrates. The coating properties were characterized by using different analytical methods for determination of structure, hardness, friction and wear behaviour. The changes of film properties in dependence of the kind and the rate of gas flow are compared and discussed. [source] Super-Hard Carbon Layers Produced on the Al2O3/Al2O3+x%SiC (whiskers) Ceramic Cutting EdgesPLASMA PROCESSES AND POLYMERS, Issue S1 2007Andrzej R. Olszyna Abstract The aim of the present study was to examine how the cutting properties of tool blades are affected by super-hard ceramic (carbon) coatings produced by the RF PECVD method. The cutting plates were made of the gradient-type Al2O3/Al2O3,+,x%SiCwhiskers composites. The highest density, the greatest bending strength and the highest stress intensity factor were obtained with the layered Al2O3/Al2O3,+,x%SiCwhiskers composite. The phase composition of the coatings was examined and the deposited carbon layers were identified to be nanocrystalline diamond (NCD) contaminated with super-finegrained graphite. The thickness, roughness, adhesion to the substrate, friction coefficient and hardness of the coatings were examined. The results evidently show that, when tested in cutting hard aluminium alloys, the carbon coatings deposited on the Al2O3/Al2O3,+,x%SiCwhiskers cutting plates by RF PECVD have advantageous cutting properties. The service life of the coated plates compared to that of uncoated plates increased by 65% with the NCD coatings. [source] Amorphous Carbon Coatings Inhibit Crystalline Biofilm Formation on Urological ImplantsPLASMA PROCESSES AND POLYMERS, Issue S1 2007Lisa Kleinen Abstract Biofilm formation on urological stents remains a major complication in patient care. The study focuses on the ability of different plasma-deposited amorphous carbon coatings (a-C:H) to inhibit encrustation and to reduce implant-related side effects. Film forming particle flux was controlled by variation of precursor gases, pressure and RF-power resulting in different electrochemical and topological surface properties. Optical contact angle measurements were performed to determine the surface free energies of the films. Investigations on crystal adhesion and biofilm formation were performed in vitro and in vivo. Encrustation tendency was remarkably reduced by a-C:H. Compared to commercial stents, the indwelling time could be distinctly prolonged as the implanted stents remained biofilm-free. [source] | ||||||||||