Metal-containing Diamond-like Carbon Research Articles

Metal-Containing Diamond-Like Carbon Coatings with Increased Temperature Stability for Wear Protection of Nitrided Hot Forging Dies

In cold forging processes, diamond-like carbon (DLC) coatings have become established as a wear protection for forging dies, featuring high hardness and advantageous friction properties. This counteracts the particular critical abrasive tool wear and increases tool life. A major disadvantage of DLC coatings is their low thermal stability. In this study, the influence of metallic elements (niobium, tungsten and chromium) in the treatment atmosphere of the coating process is investigated with the aim of increasing the temperature resistance of the DLC coating and enabling its application as a wear-protection measure for hot forging dies. Preliminary studies were carried out to investigate the influence of different treatment atmospheres on wear-reducing properties such as high hardness and coating adhesion depending on prior nitriding processes. The most promising metal-doped DLC coating, with 30 % tungsten in the treatment atmosphere, was used in serial forging tests. At a blank temperature of 1,200 °C and a moderate count of 100 forging cycles, wear was reduced by up to 60 % compared to the nitrided reference tool.

Surface Structuring of Diamond-Like Carbon Films by Chemical Etching of Zinc Inclusions

A diamond-like carbon (DLC) film with a nanostructured surface can be produced in a two-step process. At first, a metal-containing DLC film is deposited. Here, the combination of plasma source ion implantation using a hydrocarbon gas and magnetron sputtering of a zinc target was used. Next, the metal particles within the surface are dissolved by an etchant (HNO3:H2O solution in this case). Since Zn particles in the surface of Zn-DLC films have a diameter of 100–200 nm, the resulting surface structures possess the same dimensions, thus covering a range that is accessible neither by mask deposition techniques nor by etching of other metal-containing DLC films, such as Cu-DLC. The surface morphology of the etched Zn-DLC films depends on the initial metal content of the film. With a low zinc concentration of about 10 at.%, separate holes are produced within the surface. Higher zinc concentrations (40 at.% or above) lead to a surface with an intrinsic roughness.

Antimicrobial and anti-biofilm properties of polypropylene meshes coated with metal-containing DLC thin films.

A promising strategy to reduce nosocomial infections related to prosthetic meshes is the prevention of microbial colonization. To this aim, prosthetic meshes coated with antimicrobial thin films are proposed. Commercial polypropylene meshes were coated with metal-containing diamond-like carbon (Me-DLC) thin films by the magnetron sputtering technique. Several dissimilar metals (silver, cobalt, indium, tungsten, tin, aluminum, chromium, zinc, manganese, tantalum, and titanium) were tested and compositional analyses of each Me-DLC were performed by Rutherford backscattering spectrometry. Antimicrobial activities of the films against five microbial species (Candida albicans, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis) were also investigated by a modified Kirby-Bauer test. Results showed that films containing silver and cobalt have inhibited the growth of all microbial species. Tungsten-DLC, tin-DLC, aluminum-DLC, zinc-DLC, manganese-DLC, and tantalum-DLC inhibited the growth of some strains, while chromium- and titanium-DLC weakly inhibited the growth of only one tested strain. In-DLC film showed no antimicrobial activity. The effects of tungsten-DLC and cobalt-DLC on Pseudomonas aeruginosa biofilm formation were also assessed. Tungsten-DLC was able to significantly reduce biofilm formation. Overall, the experimental results in the present study have shown new approaches to coating polymeric biomaterials aiming antimicrobial effect.

Influences of Interfacial Carbonization on the Structure and Mechanical Properties of Multilayered Cr-Containing Diamond-Like Carbon Films

Regarding metal-containing diamond-like carbon (Me-DLC) multilayered films, current research has focused on the influences of macroelements in the transition layer on the mechanical properties. The understanding of influences of microinterfacial structures on the mechanical properties is far from enough. One example is the structure pattern due to carbonation around the layer-to-layer interfaces in the Me-DLC films. In this work, multilayered Cr-DLC films with three modulation periods (Λ) were deposited using midfrequency dual-magnetron sputtering, and the film microstructures and mechanical properties were investigated. Along with changes in Λ, interfacial carbonization induces microstructure changes, and the microstructures include carbon bond, phase compositions, and internal stresses. The microstructure changes affect the mechanical properties, including hardness, elastic modulus, fracture toughness, and adhesion. The results reveal that variation of mechanical properties is involved with the influenc...

Preparation of Metal-Containing Diamond-Like Carbon Films by Magnetron Sputtering and Plasma Source Ion Implantation and Their Properties

Metal-containing diamond-like carbon (Me-DLC) films were prepared by a combination of plasma source ion implantation (PSII) and reactive magnetron sputtering. Two metals were used that differ in their tendency to form carbide and possess a different sputter yield, that is, Cu with a relatively high sputter yield and Ti with a comparatively low one. The DLC film preparation was based on the hydrocarbon gas ethylene (C2H4). The preparation technique is described and the parameters influencing the metal content within the film are discussed. Film properties that are changed by the metal addition, such as structure, electrical resistivity, and friction coefficient, were evaluated and compared with those of pure DLC films as well as with literature values for Me-DLC films prepared with a different hydrocarbon gas or containing other metals.

Nanoparticles as a Metal Source in Plasma Processes

When a metal is added to a layer of diamond-like carbon (DLC), the resulting particle size of the metal within the film usually depends on the metal content. To be more flexible in influencing the size of the particles that result when using a plasma based preparation process two different approaches were tested: on the one hand the combination of a gaseous precursor with magnetron sputtering, where a nanostructured coating is applied on top of the sputter target in advance; on the other hand, the addition of preformed metallic nanoparticles to a liquid. In both cases, the nanoparticles or -structures were prepared by a wet chemical process, whereas the DLC layer was prepared by a plasma process. The produced metal-containing DLC films were characterized regarding their metal content and distribution as well as regarding possible contaminations from the chemical preparation process.

Controlled Distribution and Clustering of Silver in Ag-DLC Nanocomposite Coatings Using a Hybrid Plasma Approach.

Incorporation of selected metallic elements into diamond-like carbon (DLC) has emerged as an innovative approach to add unique functional properties to DLC coatings, thus opening up a range of new potential applications in fields as diverse as sensors, tribology, and biomaterials. However, deposition by plasma techniques of metal-containing DLC coatings with well-defined structural properties and metal distribution is currently hindered by the limited understanding of their growth mechanisms. We report here a silver-incorporated diamond-like carbon coating (Ag-DLC) prepared in a hybrid plasma reactor which allowed independent control of the metal content and the carbon film structure and morphology. Morphological and chemical analyses of Ag-DLC films were performed by atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The vertical distribution of silver from the surface toward the coating bulk was found to be highly inhomogeneous due to top surface segregation and clustering of silver nanoparticles. Two plasma parameters, the sputtered Ag flux and ion energy, were shown to influence the spatial distribution of silver particles. On the basis of these findings, a mechanism for Ag-DLC growth by plasma was proposed.

Measurement of Thin-film Coating Hardness in the Presence of Contamination and Roughness: Implications for Tribology

Standard nanoindentation measurements on commercially available TiAlN, CrN, metal-containing diamond-like carbon, and TiN coatings, deposited on steel substrates were performed to determine coating hardness and elastic modulus. It was found that the coating surface roughness/morphology present after deposition can significantly affect the measurements of nanomechanical properties so that measurements of these properties on the as-deposited coating surface may be significantly different from the bulk. In addition, a surface measurement may produce a lower nanohardness due to the existence of a soft surface contamination layer. A simple method was developed to enable accurate measurement of the nanomechanical properties of coatings, while avoiding errors introduced by surface topography and the presence of superficial contamination layers on thin films. Friction and wear behavior, as well as the wear mechanisms in dry reciprocating sliding contact of the various coatings with a steel ball can be correlated to the surface attributes of each coating in terms of roughness and the presence of contamination layers, both of which are shown to also affect the nanohardness measurements.

Adhesion Reduction of Diamond-Like Carbon Films Based on Different Contact Geometries by Using an AFM

The effect of reducing adhesion force by coating with a metal-containing diamond-like carbon (DLC) film has been studied by recording force–displacement curves with an atomic force microscope. A flat tip, a spherical tip, and some sharp tips were applied to mimic the different contact geometries. The results show that both under ambient conditions and in dry nitrogen, the DLC film can effectively reduce the adhesion force for different contact geometries. The reduction of the adhesion force was attributed to the decrease of the surface free energy and the increase of the contact angle for water. The reduction ratio of adhesion is closely related to contact geometry, the roughness of DLC film, material characteristics paired with DLC film and the environment. These factors are mutually coupled to determine the final reduction ratio. Under both conditions, the DLC film also plays a role in reducing the wear and tear when measuring the adhesion forces.

138 金属を含む非晶質炭素腹の繰り返し歪みに伴う疲労特性評価

138 金属を含む非晶質炭素腹の繰り返し歪みに伴う疲労特性評価

Characterization of Cr Doped Diamond-Like Carbon Films and Research on Mechanical Properties

Diamond-like carbon (DLC) films have been extensively studied for more than a decade due to their unique combination of properties. The internal compressive stress affects their adhesion and preventing wide usage of these films. Metal-containing DLC films are expected to relax internal stress. The present work focused on the synthesis, chemical bond and mechanical property characterization of Cr-containing DLC films. The films thickness, internal stress and composition were characterized by scanning electron microscopy, optical interferometry and X-ray photoelectron spectroscopy respectively. Incorporation of Cr into DLC causes an initial internal stress reduction and subsequent stabilization around 0.5 GPa. The hardness behavior was found to depend on Cr content. Films with less than 7.36 at.% Cr (no formation of C-Cr bond) showed a dramatically hardness reduction compared to pure DLC films. Above 7.36 at.% Cr (C-Cr bond formed) the hardness increases above 12 GPa.

Optical and elastic properties of diamond-like carbon with metallic inclusions: A theoretical study

A tough material commonly used in coatings is diamond-like carbon (DLC), that is, amorphous carbon with content in four-fold coordinated C higher than ∼70%, and its composites with metal inclusions. This study aims to offer useful guidelines for the design and development of metal-containing DLC coatings for solar collectors, where the efficiency of the collector depends critically on the performance of the absorber coating. We use first-principles calculations based on density functional theory to study the structural, electronic, optical, and elastic properties of DLC and its composites with Ag and Cu inclusions at 1.5% and 3.0% atomic concentration, to evaluate their suitability for solar thermal energy harvesting. We find that with increasing metal concentration optical absorption is significantly enhanced while at the same time, the composite retains good mechanical strength: DLC with 70–80% content in four-fold coordinated C and small metal concentrations (<3 at. %) will show high absorption in the visible (absorption coefficients higher than 105 cm−1) and good mechanical strength (bulk and Young's modulus higher than 300 and 500 GPa, respectively).

Metal-Containing DLC: Toward a Smart Coating on Smart Materials

NiTi shape memory alloys (NiTi-SMA or Nitinol) have successful application thanksto their excellent and unique material properties. However, considering the practical applicationto human body, elution from the toxic Ni ions into human body should be taken into account.Many researchers have dealt with the issue and already proposed various surface treatmenttechniques including the surface oxidation and ion implantation.Our focus is to enhance thefunctionality of Nitinol. We have been developing the smart sensor utilizing metal-containingDiamond-like Carbon (Me-DLC) thin coating. Emphasis can be made on the unique propertiesof Me-DLC deposited on the Nitinol. Strong adhesive strength has been obtained in Me-DLCand Nitinol system. In this paper, we propose a novel Me-DLC coating with multifunctionalityof the suppression of the toxic Ni ions. The paper includes deposition technique, performanceof the coating concerning adhesive strength and suppression of the toxic Ni ions, and finallymultilayered structure aiming at multifunctionality.

Bias voltage effect on the structure and property of the (Ti:Cu)-DLC films fabricated by cathodic arc plasma

Titanium copper–diamond-like carbon (Ti:Cu)-DLC films were deposited onto silicon via cathodic arc evaporation process using titanium (Ti) and copper (Cu) target arc sources to provide Ti and Cu in the metal containing diamond-like carbon (Me-DLC) film systen. Acetylene reactive gases served as the carbon sources, which were activated at 180 °C at 20 mTorr. Varying substrate bias voltages from − 80 to − 250 V were used in order to provide the (Ti:Cu)-DLC structure. The structure, interface, and mechanical properties of the produced film were analyzed by transmission electron microscope (TEM), IR Fourier transform (FTIR) spectra, and Rockwell C hardness. The process parameters were compared by studying the various mechanical properties of the films, such as microhardness and adhesion. The results showed that the Ti-containing a-C:H/Cu coatings exhibited an amorphous layer of Ti-DLC layer as well as a nanocrystalline layer of Cu multilayer structure. The mechanical properties of the coatings, as determined by Rockwell C indents testing and the ball-on-disc test, varied with the the applied negative DC bias voltage. These (Ti:Cu)-DLC coatings are promising materials for soft substrate protective coatings.

Granular metals: From electronic correlations to strain-sensing applications

An analysis scheme is presented that allows for a quantitative description of the sensitivity of granular metal based strain sensors. The scheme draws on recent advances in the understanding of charge transport mechanisms in granular metals. How to deduct the relevant model parameters from temperature-dependent conductivity measurements is demonstrated by using recently published data for fcc-packed gold nanoparticle multilayers. Based on this model parameter set the intrinsic strain gauge factor is calculated as function of the intergrain coupling strength for different transport regimes. General trends for strain gauge factor optimization are identified. The absolute values for the calculated gauge factor are in good correspondence with typical values obtained for metal-containing diamondlike carbon thin film strain sensors.

Metal-Containing Diamond-Like Carbon Coating as a Smart Sensor

A new type of smart sensor based on metal-containing diamond-like carbon (DLC) coatings is presented. DLC coatings are widely used as protective coatings to improve the surface properties of objective materials; for example, to increase hardness and chemical stability. With the addition of metal clusters into DLC coatings, electrical conduction appears to depend on the microstructure. Such coatings can be used in fabricating resistive sensors. In this paper, we present tungsten-containing DLC (W-DLC) as a possible strain sensor. The strain sensitivity is greatly affected by the deposition condition. We also fabricate a double-layered DLC/W-DLC coating. The double-layered structure is expected to be used as a smart coating having functionality as a sensor with a protective DLC overcoat.

107 医療応用を目的とした形状記憶合金上に作製した金属含有ダイヤモンドライクカーボン膜の機械的特性評価(学生賞II,一般講演)

107 医療応用を目的とした形状記憶合金上に作製した金属含有ダイヤモンドライクカーボン膜の機械的特性評価(学生賞II,一般講演)

Activation energy in metal-containing DLC films with various metals of various concentrations

The activation energy of (Co, Mo, W)-containing diamond-like carbon (DLC) films with different metal concentrations was investigated. The films were deposited onto silicon substrates by radio frequency discharged methane plasma and a co-sputtering of the metal target. The structure of the films was analyzed by Raman spectroscopy and using a transmission electron microscope. The results indicated that crystalline metal clusters are dispersed in amorphous carbon insulating matrix, and hence the metal-containing DLC films investigated can be classified as granular films. The temperature dependence of the resistance was also measured. From the temperature dependence, the activation energy was calculated numerically using σ = σ 0exp(− E / kT). The calculated activation energy rapidly decreases as the metal concentration increases. This is because of the increase in the average size of the metal clusters. A detailed discussion is presented in terms of the radius of the metal clusters inside the films.

Boundary Lubrication Characteristic of Metal-Containing Diamond-Like Carbon (DLC) Films with Poly Alpha Olefin (PAO) Lubricant

The effects of metals such as cobalt (Co), cerium (Ce), magnesium (Mg), nickel (Ni) and titanium (Ti) added to diamond-like carbon (DLC) films on boundary lubrication properties were investigated using a ball-on disk tribometer. The boundary lubrication properties of metal-containing DLC films are improved compared with those of DLC films without metal under poly alpha olefin (PAO) lubricant with and without glycerol mono-oleate (GMO) additives. Moreover, under boundary lubrication using PAO with GMO, DLC films with an appropriate quantity of Co-added show the lowest friction coefficient of μ= 0.02 among all the tested metal-containing DLC films. The friction product layers were formed on the sliding surface of Co-containing DLC films. Lower-nanofriction layers formed on the sliding surface were observed by force modulation methods of atomic force microscopy (AFM).

Preparation and properties of W-containing diamond-like carbon films by magnetron plasma source ion implantation

W-containing diamond-like carbon (DLC) films were prepared on silicon wafers by a process combining reactive magnetron sputtering with plasma source ion implantation (PSII). A tungsten disc was used as a target for the sputter source. Ar/C 2H 2 mixed gas was introduced into the discharge chamber. Superposed negative high voltage pulses (− 10 kV, 100 Hz, 100 μs and DC − 0.5 kV) were applied to the substrate holder. The chemical composition of the films was determined using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Surface morphology was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The film structure was characterized by Raman spectroscopy, X-ray diffractometry and high resolution transmission electron microscopy (HREM). Sheet resistivity of the films was measured by a four-point probe method. Furthermore, a ball-on-disc test was employed to obtain information about the frictional properties and sliding wear resistance of the films. The structure of the films changed from metal-containing DLC to a composite of metal-containing DLC and metal carbides with increasing metal content in the films. WC 1− X carbides were observed for films composed of higher amounts of W than 20 at.%. Around 10 nm diameter nanocrystallites of WC 1− X were observed by HREM. The sheet resistivity of the films decreased drastically with increasing metal content in the films. The tribological properties of the films were improved by metal element doping. A low friction coefficient 0.09 was derived for 0.5 at.% W-containing DLC film.