scholarly journals Effect of Energy and Temperature on Tetrahedral Amorphous Carbon Coatings Deposited by Filtered Laser-Arc

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2176
Author(s):  
Frank Kaulfuss ◽  
Volker Weihnacht ◽  
Martin Zawischa ◽  
Lars Lorenz ◽  
Stefan Makowski ◽  
...  
Keyword(s):  
Amorphous Carbon ◽  
High Hardness ◽  
Significant Loss ◽  
Normal Direction ◽  
Medium Temperature ◽  
Carbon Coatings ◽  
Tetrahedral Amorphous Carbon ◽  
Bias Pulse ◽  
Arc Evaporation ◽  
Amorphous Carbon Coatings

In this study, both the plasma process of filtered laser-arc evaporation and the resulting properties of tetrahedral amorphous carbon coatings are investigated. The energy distribution of the plasma species and the arc spot dynamics during the arc evaporation are described. Different ta-C coatings are synthesized by varying the bias pulse time and temperature during deposition. An increase in hardness was observed with the increased overlapping of the bias and arc pulse times. External heating resulted in a significant loss of hardness. A strong discrepancy between the in-plane properties and the properties in the film normal direction was detected specifically for a medium temperature of 120 °C during deposition. Investigations using electron microscopy revealed that this strong anisotropy can be explained by the formation of nanocrystalline graphite areas and their orientation toward the film’s normal direction. This novel coating type differs from standard amorphous a-C and ta-C coatings and offers new possibilities for superior mechanical behavior due to its combination of a high hardness and low in-plane Young’s Modulus.

Electron Emission Through Tetrahedral Amorphous Carbon Coatings on Mo and Si Emitters

1997 ◽  
Vol 498 ◽  
Author(s):  
W. B. Choi ◽  
A. F. Myers ◽  
M. Q. Ding ◽  
A. K. Sharma ◽  
J. Narayan ◽  
...  
Keyword(s):  
Amorphous Carbon ◽  
Columnar Structure ◽  
Hydrogen Atmosphere ◽  
Carbon Coatings ◽  
Field Emission Properties ◽  
Tetrahedral Amorphous Carbon ◽  
Low Field ◽  
Improved Stability ◽  
Thick Coatings ◽  
Amorphous Carbon Coatings

ABSTRACTThe field emission properties of molybdenum and silicon emitter coated with tetrahedral amorphous carbon (or amorphous diamond) were studied. The tetrahedral amorphous carbon was deposited by laser ablation and showed a uniformly coated columnar structure over the entire emitter. In general, current conditioning improved stability and increased the current density. Coatings of ta-C on Mo emitters with and without nitrogen incorporated both yielded significantly higher emissivity than uncoated emitters. Nitrogen incorporation reduced the effective workfunction and the sp3/sp2 ratio. However similar depositions on Si emitters reduced the emissivity, and may be attributable to the residual oxide at the ta-C/Si interface. Annealing in a hydrogen atmosphere enhanced emissivity from both ta-C/Mo and ta-C/Si emitters. In general, thick coatings lowered the emissivity and the slope of the I-V curves. A temperature dependence of emission was observed only in the low field regions.

scholarly journals Amorphous Carbon Coatings for Total Knee Replacements—Part I: Deposition, Cytocompatibility, Chemical and Mechanical Properties

Polymers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1952
Author(s):  
Benedict Rothammer ◽  
Kevin Neusser ◽  
Max Marian ◽  
Marcel Bartz ◽  
Sebastian Krauß ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Amorphous Carbon ◽  
Detailed Characterization ◽  
Carbon Coatings ◽  
Dlc Coatings ◽  
Total Knee Replacements ◽  
Knee Replacements ◽  
Total Knee ◽  
Amorphous Carbon Coatings

Diamond-like carbon (DLC) coatings have the potential to reduce implant wear and thus to contribute to avoiding premature failure and increase service life of total knee replacements (TKAs). This two-part study addresses the development of such coatings for ultrahigh molecular weight polyethylene (UHMWPE) tibial inlays as well as cobalt–chromium–molybdenum (CoCr) and titanium (Ti64) alloy femoral components. While a detailed characterization of the tribological behavior is the subject of part II, part I focusses on the deposition of pure (a‑C:H) and tungsten-doped hydrogen-containing amorphous carbon coatings (a‑C:H:W) and the detailed characterization of their chemical, cytological, mechanical and adhesion behavior. The coatings are fabricated by physical vapor deposition (PVD) and display typical DLC morphology and composition, as verified by focused ion beam scanning electron microscopy and Raman spectroscopy. Their roughness is higher than that of the plain substrates. Initial screening with contact angle and surface tension as well as in vitro testing by indirect and direct application indicate favorable cytocompatibility. The DLC coatings feature excellent mechanical properties with a substantial enhancement of indentation hardness and elastic modulus ratios. The adhesion of the coatings as determined in modified scratch tests can be considered as sufficient for the use in TKAs.

Amorphous Carbon Coatings for Locally Adjusted Tribological Properties in Sheet Bulk Metal Forming

2012 ◽  
Vol 504-506 ◽  
pp. 969-974 ◽  
Author(s):  
Harald Hetzner ◽  
Stephan Tremmel ◽  
Sandro Wartzack
Keyword(s):  
Amorphous Carbon ◽  
Tribological Properties ◽  
Metal Forming ◽  
Friction And Wear ◽  
Wear Properties ◽  
Carbon Coatings ◽  
Bulk Metal ◽  
Bulk Metal Forming ◽  
Friction And Wear Properties ◽  
Amorphous Carbon Coatings

In sheet bulk metal forming, locally adapted friction properties of the contact tool/workpiece are an appropriate means for the targeted enhancement of the material flow, enabling an improved form filling and lowered forming forces. However, the implementation of desirable friction conditions is not trivial. And further, friction is inseparably linked to wear and damage of the contacting surfaces. This calls for a methodological approach in order to consider tribology as a whole already in the early phases of process layout, so that tribological measures which allow fulfilling the requirements concerning local friction and wear properties of the tool surfaces, can already be selected during the conceptual design of the forming tools. Thin tribological coatings are an effective way of improving the friction and wear properties of functional surfaces. Metal-modified amorphous carbon coatings, which are still rather new to the field of metal forming, allow tackling friction and wear simultaneously. Unlike many other types of amorphous carbon, they have the mechanical toughness to be used in sheet bulk metal forming, and at the same time their friction properties can be varied over wide ranges by proper choice of the deposition parameters. Based on concrete research results, the mechanical, structural and special tribological properties of tungsten-modified hydrogenated amorphous carbon coatings (a-C:H:W) are presented and discussed against the background of the tribological requirements of a typical sheet bulk metal forming process.

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