Diamond-like Carbon Nanocomposites Research Articles

Antiviral and antibacterial efficacy of nanocomposite amorphous carbon films with copper nanoparticles

Copper compound-rich films and coatings are effective against widespread viruses and bacteria. Even though the killing mechanisms are still debated, it is agreed that the metal ion, nanoparticle release, and surface effects are of paramount importance to the antiviral and antibacterial efficacy of the surfaces. In this work we have investigated the behavior of the reactive magnetron sputtered nanocomposite diamond-like carbon thin films with copper nanoparticles (DLC:Cu). The films were etched employing oxygen plasma and/or exposed to ultra-pure water, aiming to investigate the differences of the Cu release in the medium and changes in film morphology. The presence of metallic copper and Cu2O phases was confirmed by multiple analytical methods. Pristine films were more effective in the Cu release reaching up to 1.3 mg/L/cm2 concentration. Plasma processing resulted in the oxidation of the films which released less Cu, but after exposure to water, their average roughness increased more, up to 5.5 nm. Pristine and O2 plasma processed DLC:Cu films were effective against both model coronavirus and herpesvirus after 1-hour contact time and reached virus reductions of up to 2.23 and 1.63 log10, respectively. Pristine DLC:Cu films were more effective than plasma-processed ones against herpesvirus, while less expressed difference was found for coronavirus. The virucidal efficacy over up to 24 h exposures in the aqueous medium was validated. A bactericidal study confirmed that pristine DLC:Cu films were effective against gram-negative E. coli and gram-positive E. faecalis bacteria. After 3 h, 100 % antibacterial efficiency (ABE) was obtained for E. coli and 99.97 % for E. faecalis. After 8 h and longer exposures, 100 % ABE was reached. The half-life inactivation of viruses was 8.10–11.08 min and for E. faecalis 15.1–72.2 min.

Magnetron sputtering process for deposition of multilayered thin diamond-like carbon films with silver nanoparticles for anti-reflective coatings and refractometric sensing

Multilayered film stacks serving optical applications usually require multiple target sources for deposition. In this work, we present a convenient method for the deposition of single- and multilayered thin films with varying diamond-like carbon (DLC) and silver content employing a single magnetron in the deposition system. For this, a reactive magnetron sputtering system was utilized and the silver target was poisoned based on desired structure: clean target and argon gas resulted in a pure silver film, completely poisoned target and acetylene and argon gas resulted in a DLC film, and anything in between resulted in a nanocomposite DLC:Ag film. The films were deposited on fused quartz, crystalline silicon, and porous anodized aluminum oxide substrates. We investigated the optical properties of these films and showed their applications for anti-reflective, black-appearing coatings and refractometric sensors, both experimentally and by simulation methods.

Highly-hydrophobic, transparent, and durable coatings based on ZnO tetrapods with diamond-like carbon nanocomposite

This study investigates the wettability of ZnO tetrapod (ZnO-T) coatings in relation to surface morphology and protective diamond-like carbon nanocomposites with SiOx (DLC:SiOx) film parameters. Randomly distributed ZnO-Ts with different leg lengths were observed to have varying degrees of wettability, which also changed keeping samples in the dark at room temperature. DLC:SiOx films significantly increase the hydrophobicity of ZnO-T coatings, and their thickness influences the surface roughness and hydrophobicity of the coating, moreover DLC:SiOx films show protection not only from the abrasion but also passivate the ZnO-T coatings from light-induced effects. The results indicate that the largest size ZnO-T fraction with a 40 nm thickness of DLC:SiOx film can provide the best hydrophobicity represented by a water contact angle of 148°, while the smallest ZnO-T fraction with a 120 nm thickness of DLC:SiOx film can provide better mechanical durability. We expect that the detailed analysis of ZnO-T coatings with protective DLC:SiOx films conducted in this study will be advantageous for other nanostructures with protective coatings application in wettability control.

X-RAY DIFFRACTION STUDIES OF THE EFFECT OF PHASE COMPOSITION AND STRUCTURAL STATE CHARACTERISTICS ON THE TRIBOLOGICAL BEHAVIOR OF THE MOLYBDENUM- AND TUNGSTEN-BASED STRENGTHENING COATINGS

A comprehensive study of phase composition, structural state, parameters of fine atomic structure, mechanical and tribological properties of molybdenum-carbon and tungsten-carbon-based coatings deposited by reactive magnetron sputtering in an acetylene-argon gas mixture has been carried out. It has been shown that the resulting coatings have a nanocomposite diamond-like carbon (DLC) structure based on the metal and the metal carbide phases with close sizes of coherently diffracting domains (CDD), approximately 3–7 nm, and on hydrogenated amorphous carbon. The coating nanohardness values were 13–15 and 20–23 GPa for the Mo-DLC and W-DLC coatings, respectively. The tribological tests have demonstrated that the Mo- and W-DLC coatings can reduce friction and effectively protect the steel surfaces hardened by them both under dry friction and under boundary lubrication conditions.

High Temperature Characterization of a MIS Schottky Diode Based on Diamond-Like Carbon Nanocomposite Film

Many kind of materials have been inserted between metals and semiconductors to obtain metal–interlayer–semiconductor (MIS) Schottky diodes with higher barrier height. It is well known that the interlayer materials have to meet some requirements such as hold on the substrate, thermal stability and wear resistance. In this context, the diamond-like carbon (DLC) films seem good candidates as a material that can fulfill these requirements due to their superior properties. In this study, sulfur doped diamond-like carbon (S-DLC) nanocomposite film was deposited electrochemically, and it was used as an interlayer to fabricate an Au/S-DLC/p-Si MIS Schottky diode. An Au/p-Si metal semiconductor diode was also fabricated for comparison. The electrodeposited S-DLC film was characterized by scanning electron microscopy, Raman spectroscopy and x-ray photoelectron spectroscopy. Temperature dependence of the current–voltage (I–V) characteristic of the diodes was studied in the range of 300–700 K. The ideality factors (n) and barrier heights (Φb) were calculated from the forward bias I–V characteristics. It was observed that both parameters showed temperature dependence. Barrier height values were increased with increasing temperature, while ideality factors values were decreased. The observed non-linearity in Richardson plots were explained by Gaussian distributions of inhomogeneities of barrier heights. Modified Richardson plots were used to obtain actual values of barrier height. It was shown that S-DLC film can be a good candidate for the high temperature diode applications.

Development and Potential Application of Advanced Functional Materials in the Oil Field

The oil and gas industry places higher demands for new technologies and new materials. Advanced functional materials show broad application prospects in the oil field. Technological advances in the oil and gas sector are inseparable from the development and application of advanced functional materials. Through literature research, patent search analysis, expert consultation, some advanced functional materials with potential application in the oil field are sorted out, in order to provide inspiration and new ideas for improving the development of the oil and gas drilling technology. The nanomaterials dispersion and nanocomposites films are two of the most accessible ways to apply nanomaterials in the oil field. The cellulose nanofibers (CNF) and the diamond-like carbon (DLC) nanocomposites films would provide inspiration for the oil field chemistry and protection of downhole tools. The application of CNF and DLC nanocomposites could provide innovative ideas, research and foundation for the future development of the oil and gas drilling technology, and contribute to achieving a major technological breakthrough and improve the overall level of the oil and gas drilling technology.

Laser co-ablation of bismuth antimony telluride and diamond-like carbon nanocomposites for enhanced thermoelectric performance

A series of innovative heterogeneous nanocomposites comprising diamond-like carbon (DLC) clusters and well-aligned Bi–Sb–Te based nanoassemblies were realized for thermoelectric enhancement.

Electrical and magnetic properties of electrodeposited nickel incorporated diamond-like carbon thin films

Abstract Nanocomposite diamond-like carbon (DLC) thin films have been synthesized by incorporating nickel (Ni) nanoparticles in DLC matrix with varying concentration of nickel. DLC and Ni-DLC thin films have been deposited on ITO coated glass substrates employing low voltage electrodeposition method. Electrical properties of the samples were studied by measuring current–voltage characteristics and dielectric properties. The current approaches toward an ohmic behavior with metal addition. This tendency of increasing ohmicity is enhanced with increase in dilution of the electrolyte. The conductivity increases with Ni addition and interestingly it continues to increase with dilution of Ni concentration in the electrolyte in the range of our study. Magnetic properties for DLC and Ni-DLC thin film samples were examined by electron paramagnetic resonance (EPR) measurements and Super Conducting Quantum Interference Device (SQUID) measurements. g -Value for DLC is 2.074, whereas it decreases to 2.055 with Ni addition in the electrolyte. This decrement arises from the increased sp 2 content in DLC matrix. The magnetic moment vs. magnetic field ( m – H ) curves of Ni-DLC indicate superparamagnetic behavior which may be due to ferromagnetic contribution from the incorporated nickel nanoparticles in the DLC matrix. The ZFC curve of Ni-DLC after the blocking temperature shows a combined contribution of ferromagnetic, superparamagnetic and paramagnetic nature of the materials persisting up to 300 K.

Materials in Space: Exploring the Effect of Low Earth Orbit on Thin Film Solid Lubricants

Abstract This article considers the effect of atomic oxygen exposure in low earth orbit on thin film solid lubricants of molybdenum disulphide and diamond-like carbon nanocomposites, a silica-containing diamond-like carbon film. Advances in deposition methods over the past few decades enable dense films to be created that are more resistant to oxidative degradation and the effects of adsorbed moisture than their predecessors. Further, incorporating additional phases improves the tribological performance of the films in a range of atmospheres.

Attaining High Levels of Bearing Performance with a Nanocomposite Diamond-Like Carbon Coating

Mechanical systems that operate in agricultural, construction, and mining and mineral processing applications typically operate in debris-containing and thin-film lubrication environments. Consequently, the lives of rolling element bearings in these applications are often limited by surface fatigue arising from thin-film lubrication, damage from the debris, false brinelling, and scuffing. Traditional approaches utilizing specialized heat treatments and lubricant additives can sometimes delay the onset of early raceway fatigue, but even in these cases the actual bearing life is still usually less than that for which the bearing was designed. Bearings with a highly durable W-aC:H coating applied to the rolling elements are shown to have significantly longer fatigue lives in debris-containing and thin-film lubrication environments and are highly resistant to wear from false brinelling and scuffing.

Mechanism Behind the Formation of Self-Assembled Nano-Sized Clusters in Diamond-Like Carbon Nanocomposite

Many studies have shown that Diamond-like carbon (DLC) films with diversified material properties are obtainable through doping process but the presence of the dopants were reported to form independent nanoclusters within the carbon matrix. Using combined analysis from theoretical estimations (Saha's equation and coefficient of absorption, alpha(p)), Transport of Ions In Matter (TRIM) simulation and experimental results, this work examined the mechanism behind the formation of self-assembled nanoclusters in DLC nanocomposite. We showed that the presence of metal dopants increased the heat dissipation on DLC, which allowed the energetic metal species to diffuse and enhance the formation of nanoclusters that increased the surface roughness of the films. In addition, TRIM and X-ray Photoelectron Spectroscopy (XPS) hinted the presence of energetic species may force the carbon ions to react with the interface to form silicon carbide bonds, which may be a more dominant factor compared to internal stress reduction in improving the adhesion strength of DLC.

Synthesis of functional diamond-like carbon nanocomposite films containing titanium dioxide nanoparticles

Synthesis of diamond-like carbon (DLC) films with UV-induced-hydrophilicity function was studied by inductively-coupled plasma (ICP) chemical vapor deposition. Titanium tetraisopropoxide (TTIP) and oxygen gases were employed as the precursors to deposit diamond-like nanocomposite films containing titanium dioxide (TiO 2) nanoparticles. X-ray diffraction and high-resolution transmission electron microscopy revealed that TiO 2 nanocrystallites were formed in the DLC films when oxygen concentration was higher than TTIP concentration during deposition. The DLC nanocomposite film was hydrophobic without ultraviolet (UV) irradiation, and became highly hydrophilic under UV irradiation, exhibiting the self-cleaning effect. A very broad peak centered at 1580 cm − 1 was observed in the Raman spectra confirming the formation of DLC films. The hardness of the film was about 8 GPa with a stress of 3 GPa. ICP was essential in forming the photocatalytic TiO 2 nanoparticles in the DLC matrix.

Comparative study between erbium and erbium oxide-doped diamondlike carbon films deposited by pulsed laser deposition technique

Diamondlike carbon (DLC) films doped with the same fraction of erbium and erbium oxide were prepared by using 248 nm KrF pulsed laser deposition system. The effects of erbium and erbium oxide on the surface morphology, microstructures, and mechanical property of DLC were investigated. Transmission electron microscopy showed that both erbium and erbium oxide retained their initial oxidation states while embedded as metal or metal-oxide nanoclusters in an amorphous matrix. Atomic force microscopy showed that erbium-doped and erbium oxide-doped DLC films were smooth with rms of less than 0.2 nm and closely resembled pure DLC film. The Raman analysis showed broad peaks centering around 1550 cm−1 on both samples. The deconvoluted Raman spectra showed that the ID/IG value of DLC film increased from 0.38 to ∼0.55 in the presence of erbium and erbium oxide, and the estimated sp3 content for the DLC nanocomposite films was ∼56%–57%. X-ray photoelectron spectroscopy (XPS) confirmed that the C 1s peaks for DLC nanocomposite were slightly shifted from 285.2 eV (diamond) to 284.5 eV (graphite). The deconvolution of XPS spectra further confirmed the amount of sp3 content and revealed the presence of a higher fraction of SiC bonding in erbium oxide-doped DLC film. Microscratch tester results showed that the presence of erbium oxide improved the adhesion strength of DLC film from ∼1.72 to ∼2.19 N, which was more effective than erbium at the same concentration (∼1.89 N). The coefficients of friction of the erbium-doped DLC and erbium oxide-doped DLC films were similar to that of pure DLC. Erbium and erbium oxide showed similar influence on the surface roughness, coefficient of friction, and sp3 content on DLC films, but improved adhesion strength, which was correlated with the SiC bonding states, was observed on erbium oxide-doped DLC.

Atomic-scale structure and composition of tungsten carbide reinforced diamondlike carbon films

This study presents the true atomic-scale structure and composition of hard/lubricious nanocomposite diamondlike carbon (DLC) films. Nanocrystalline tungsten carbide (∼2–4 nm precipitates) in mixed sp3/sp2 amorphous C–H matrices was characterized using the combination of three-dimensional atom probe (3DAP) tomography and transmission electron microscopy. Excellent correspondence in structural and chemical layering was observed (alternating ∼25 nm thick carbon-rich and tungsten-rich layers) with 3DAP also revealing C32+ and C2H4+ species in the carbon-rich layers and W2+, WC2+, C+, and C2+ species in the tungsten-rich layers. 3D morphology and chemical partitioning of the WC nanoprecipitates in the tungsten-rich layers are also discussed.

Comparative surface and nano-tribological characteristics of nanocomposite diamond-like carbon thin films doped by silver

In this study we have deposited silver-containing hydrogenated and hydrogen-free diamond-like 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.

Cr-diamondlike carbon nanocomposite films: Synthesis, characterization and properties

Diamondlike carbon (DLC) films, known for exhibiting attractive combination of properties, have been extensively studied in the recent past. The inherent, internal compressive stresses affecting their adhesion and their relatively low thermal stability above 400 °C are two major drawbacks preventing wide usage of these films. Carbide formers incorporated into the carbon network have the potential to stabilize the film structure, relax internal stresses and improve their performance. The present work focuses on the synthesis, structure and mechanical and tribological property characterization of Cr-containing nanocomposite DLC films. The films were synthesized using a plasma-enhanced hybrid chemical vapor and physical vapor deposition process in a discharge composed of a mixture of CH 4 and Ar gases. The Cr content in the films varied up to 18 at.%. The film morphology and composition were characterized by scanning and transmission electron microscopy, X-ray photoelectron spectroscopy and nuclear reaction analysis. The mechanical and tribological behavior of the films was studied as a function of Cr concentration by conducting nanoindentation and pin-on-disc experiments, respectively. The results showed that the films can be either amorphous with dispersed metallic-like Cr (at low Cr content) or nanocomposite consisting of face-centered cubic metastable CrC nanoparticles dispersed in the DLC matrix. Films with low Cr content (< 5 at.%) were found to possess similar tribological characteristics with those of pure DLC films. Incorporation of more Cr (> 12 at.%) results in larger chromium carbide particles that have an adverse effect on wear resistance. The films with the low Cr content offer the opportunity to combine the excellent tribological behavior with other desirable properties deriving from the presence of the second phase.

Tribological analysis of nano-composite diamond-like carbon films deposited by unbalanced magnetron sputtering

Ti-containing nano-composite diamond-like carbon (DLC) coatings have been developed with improved tribological characteristics. These coatings were synthesized by sputtering of pyrolitic graphite and titanium targets using unbalanced magnetrons with pulsed plasma technology. Compared with the Ti-containing nano-composite DLC film, a graded Ti–C:H/TiCN/TiN film was also deposited by sputtering of titanium targets in reactive gases (nitrogen and C 2 H 2 ) using the same deposition system. The Ti/C multi-layered DLC coating deposited at a substrate rotation speed of 5 rev./min depicted an amorphous structure with 2-nm periodic thicknesses, and gave satisfactory friction performance in the pin-on-disk tests with a wear rate of 1–3×10 −17 m 3 /Nm and a friction coefficient of 0.09–0.1 against 100Cr6 steel and WC. The steady-state friction coefficient of nano-composite DLC films is lower than that of graded Ti–C:H DLC films (0.15–0.17). When sliding against soft copper ball, the friction coefficients of the DLC films were higher and increased with the sliding process from an initial friction coefficient of 0.15 with a promising wear behavior. Wear debris were primarily composed of copper mixed with surface impurities. SEM, EDX and XPS analyses depicted that the initial Ti contained C–O transfer films possess good adhesion between the sliding counterparts (100Cr6 and WC) and the coatings during the initial sliding stage. Micro-Raman spectra acquired from the nano-composite DLC coatings demonstrated a tendency of graphite formation of the transfer film. The readily transferred oxide-free graphite-like sp 2 films form a lubricious layer, which possess low shear strengths under applied loads. The XPS analysis of DLC C1s core level also suggests that transfer film is sp 2 dominated.

Tribological analysis of nano-composite diamond-like carbon films deposited by unbalanced magnetron sputtering

Ti-containing nano-composite diamond-like carbon (DLC) coatings have been developed with improved tribological characteristics. These coatings were synthesized by sputtering of pyrolitic graphite and titanium targets using unbalanced magnetrons with pulsed plasma technology. Compared with the Ti-containing nano-composite DLC film, a graded Ti–C:H/TiCN/TiN film was also deposited by sputtering of titanium targets in reactive gases (nitrogen and C 2H 2) using the same deposition system. The Ti/C multi-layered DLC coating deposited at a substrate rotation speed of 5 rev./min depicted an amorphous structure with 2-nm periodic thicknesses, and gave satisfactory friction performance in the pin-on-disk tests with a wear rate of 1–3×10 −17 m 3/Nm and a friction coefficient of 0.09–0.1 against 100Cr6 steel and WC. The steady-state friction coefficient of nano-composite DLC films is lower than that of graded Ti–C:H DLC films (0.15–0.17). When sliding against soft copper ball, the friction coefficients of the DLC films were higher and increased with the sliding process from an initial friction coefficient of 0.15 with a promising wear behavior. Wear debris were primarily composed of copper mixed with surface impurities. SEM, EDX and XPS analyses depicted that the initial Ti contained C–O transfer films possess good adhesion between the sliding counterparts (100Cr6 and WC) and the coatings during the initial sliding stage. Micro-Raman spectra acquired from the nano-composite DLC coatings demonstrated a tendency of graphite formation of the transfer film. The readily transferred oxide-free graphite-like sp 2 films form a lubricious layer, which possess low shear strengths under applied loads. The XPS analysis of DLC C1s core level also suggests that transfer film is sp 2 dominated.

Improved Tribological Properties of Diamondlike Carbon/Metal Nanocomposites

ABSTRACTOne of the many forms of carbon, diamondlike carbon (DLC), consists mainly of sp3-bonded carbon atoms. DLC coatings possess properties close to diamond in terms of hardness, atomic bonding, and chemical inertness. Unfortunately, DLC exhibits poor adhesion to metals and polymers. The adhesion of the DLC film is determined by internal stresses in the film and by interfacial bonding. This work involves processing, characterization and modeling of diamondlike composite films on metal and polymer substrates to improve adhesion and wear properties. A novel target design was adopted to incorporate metal (silver or titanium) atoms into DLC films during pulsed laser deposition. STEM of the DLC/metal nanocomposites has shown that the metals that do not form carbides (e.g., silver) form 2–10 nm inclusions within the DLC matrix. Wear resistance measurements made on these samples have demonstrated that DLC/metal nanocomposites possess exceptional wear resistance. Diamond-like carbon nanocomposites also exhibit significantly enhanced adhesion. Careful analysis of the Raman data also indicated a significant shift to shorter wavelength in DLC nanocomposite films, indicating a reduction in compressive stress within these films. The sp3 content of these films was studied using electron energy loss spectroscopy (EELS). By varying the metal concentration as a function of distance from the interface, we have created functionally gradient DLC nanocomposites. These DLC/metal nanocomposite coatings have multiple biomedical applications.

Superhard, functionally gradient, nanolayered and nanocomposite diamond-like carbon coatings for wear protection

Abstract Recent progress in the development of advanced carbon-based tribological coatings is reviewed. Pulsed laser deposition (PLD) was used to produce superhard (60–70 GPa) self-lubricating diamond-like carbon (DLC) with low friction and low wear rate. Attention was given to the improvement of coating toughness. A hybrid of magnetron sputtering and PLD was used to deposit coatings with architectures designed to withstand 1–10 GPa contact stress. This included: (1) composite coatings combining hydrogen-free and hydrogenated DLC; (2) functionally gradient metal-ceramic-DLC and nanolayered coatings with crystalline metal and carbide interlayers (about 10 nm thick) between DLC layers (about 60 nm thick); and (3) nanocrystalline-amorphous composite coatings with 10–50 nm diameter carbide particles encapsulated in a DLC matrix. The research led to the fabrication of thin (2–3 μm) DLC-based coatings for steel substrates, which could maintain friction coefficients of about 0.1 for several million cycles of unlubricated sliding at contact pressures above 1 GPa. Their scratch resistance exeeded that of conventional ceramic (TiN, TiC) coatings.