Hard Carbon Films Research Articles

Contact fatigue of thin hard diamond-like carbon films on M50 steels under cyclic spherical micro-indentation

Contact fatigue behaviors of thin hard diamond-like carbon (DLC) films on M50 steels during cyclic spherical micro-indentations were investigated. The stress-strain evolution of the entire system was analyzed by finite element methods. The film fracture mechanisms and interfacial bearing responses under monotonic and repeated contacts were comprehensively explored. Concentrated tensile and shear stresses were found to, respectively, govern the initiation and propagation of the surface ring cracks. Elevated tensile stresses at the initiation and epilogue of each indentation cycle enhanced bottom radial cracking. At the interfaces, the maximum tensile (σnmax) and shear (σtmax) stresses occurred at the end of unloading and loading processes, respectively. With increasing maximum indentation forces, σnmax initially increased and then gradually decreased, while σtmax increased monotonically.

Pulse length selection in bipolar HiPIMS for high deposition rate of smooth, hard amorphous carbon films

Amorphous carbon films were deposited by bipolar HiPIMS, as a function of negative and positive voltage pulse lengths (50-175 μs and 0-175 μs respectively), using argon as sputter gas. The deposition rate, compressive stress, sp3 fraction and mechanical properties of the films were investigated and the results compared with those of amorphous carbon films deposited by conventional unipolar HiPIMS. We found minimum threshold positive and negative lengths are required in bipolar HiPIMS to enhance the sp3 fraction above 45 % and reduce the argon content. In addition to increasing the flux and energy of depositing ions by electrostatic control, bipolar HiPIMS also increases the flux ratio of depositing ions to sputter ions and thus reduces the probability of sputter gas incorporation into the growing amorphous carbon layers. Reduced argon content in the coatings correlates with high residual stress, high hardness and evidently enhanced tool cutting functionality.

Nano- and Micro-Scale Impact Testing of Hard Coatings: A Review

In this review, the operating principles of the nano-impact test technique are described, compared and contrasted to micro- and macro-scale impact tests. Impact fatigue mechanisms are discussed, and the impact behaviour of three different industrially relevant coating systems has been investigated in detail. The coating systems are (i) ultra-thin hard carbon films on silicon, (ii) DLC on hardened tool steel and (iii) nitrides on WC-Co. The influence of the mechanical properties of the substrate and the load-carrying capacity (H3/E2) of the coating, the use of the test to simulate erosion, studies modelling the nano- and micro-impact test and performing nano- and micro-impact tests at elevated temperature are also discussed.

Use of Raman Spectroscopy to Qualify Carbon Materials

In the last 30 to 40 years, various new types of carbon materials have been engineered for multiple industrial uses. It is now well-known that the Raman spectrum is sensitive to the structure, even though the spectrum is rather uncomplicated. Because Raman spectroscopy now has a reputation for providing good information, potential users of Raman equipment can request information on the quality of their sample. However, they are often not able to define clearly what they mean by “quality.” If they are growing diamond films, they may or may not want interstitial sp2 carbon to glue polycrystalline diamond together. If they are growing hard diamond-like carbon (DLC) films, they may want to correlate the spectral characteristics with physical characteristics of the film. In this column, I explain how the Raman characteristics can aid in characterization of carbon materials.

Tribolayer‐dependent origin of ultralow friction in nanocrystalline diamond films sliding against Si3N4 ball

This study investigates the role of sliding counterbodies, which significantly affect the wear properties and friction of nanocrystalline diamond (NCD) film. The bearing steel balls exhibit a high friction coefficient of 0.12, whereas a ceramic ball of Si3N4 achieves an ultralow friction coefficient of 0.06. The evolution of different friction coefficients with different counterbodies is associated with the formation of a tribolayer at the sliding interface. The decreased friction coefficient in NCD films sliding against Si3N4 ball is likely linked to the occurrence of lubricating nanostructures, especially the silica‐like oxide compounds and graphite‐like carbon phases. The findings of this study may provide new avenues for the design and development of wear‐resistant and environment‐friendly hard carbon films.

Self‐standing hard carbon anode derived from hyper‐linked nanocellulose with high cycling stability for lithium‐ion batteries

AbstractThe utilization of binders has severely hindered ionic diffusion and electron transfer in the traditional lithium‐ion battery. Herein, a self‐standing hard carbon film using nanocellulose as precursor has been constructed as binder‐free electrodes via two‐step thermal treatment. The cyclization and aromatization of small molecular fragments promote the formation of hyper‐crosslinked framework with abundant welded junctions. Importantly, carbon nanofibers not only serve as an inter‐connected conductive network for fast electron transfer, but also as an interlinked mechanical skeleton for convenient Li+ diffusion and electrode structural stability. Furthermore, the optimized carbon film, with accessible redox‐active carbonyl groups (CO) and abundant micropores, is beneficial for Li+ accommodation. It exhibits high reversible capacity of 513.1 mAh g−1 at 50 mA g−1 and excellent cycle stability to extend over 1000 cycles without signs of decay. This study provides an efficient strategy for the design of high‐performance biomass‐derived anode materials with stable‐structure for alkaline batteries.image

Synthesis of hard diamond-like carbon films by double-pulse high-power impulse magnetron sputtering

Hard diamond-like carbon (DLC) films were prepared by a double-pulse high-power impulse magnetron sputtering (HiPIMS) at an Ar gas pressure of 0.6 Pa and average power of 90 W. The objective was to increase the sp3 C content in the films, in comparison to single-pulse HiPIMS. The first HiPIMS plasma temporally evolved during a pulse-on time of the voltage source with a width of about 15 μs and the discharge current reached 50 A corresponding to 1.8 A/cm2. After the application of the first-pulse voltage for HiPIMS, a second-pulse voltage was applied to produce the second HiPIMS from the afterglow plasma. External setting parameters such as the time interval between the first pulse and second pulse and the target current in the second HiPIMS were varied. The fraction of sp3 C–C bonds was estimated from the ratio of the peak intensity related to sp3 C–C bonds to the total peak intensity of C1s core spectrum in X-ray photoelectron spectroscopy. The fraction of sp3 C–C bonds in the DLC film prepared by double-pulse HiPIMS reached 52% with a hardness of 36.5 GPa.

Crack evolution in diamond-like carbon films on steel substrates during nano-indentation

Fracture behaviors of thin hard diamond-like carbon (DLC) films were investigated considering the effects of plastic deformation of steel substrates. Nano-indentation tests for DLC films on SUS304 and M50 steels were conducted. The nucleation and propagation of film cracks were analyzed using the extended finite element method (XFEM). The ultimate tensile strength, fracture energy release rate and toughness of the films were evaluated. Results showed that cracks in DLC films on M50 steel substrates nucleated on the top surface of the films during nano-indentation; however, the first crack initiated at the bottom surface of DLC films on SUS304 steel because of its low yield strength. Large plastic deformation of the steel substrate was generated under nano-indentation, leading to consequent high tensile stress that concentrated first at the bottom surface of the films due to the film bending effect.

MXene‐Bonded Flexible Hard Carbon Film as Anode for Stable Na/K‐Ion Storage

AbstractHard carbon (HC) is a promising anode material for sodium‐ion batteries (SIBs) and potassium‐ion batteries (PIBs), but the volume change during the insertion/extraction of Na+ or K+ limits the cycle life, especially for PIBs due to the large ion size of K+. Moreover, the conventional anodes fabricated through the coating method cannot satisfy the requirement of flexible devices. Here, it is shown that 2D carbide flakes of Ti3C2Tx MXene can be used as multifunctional conductive binders for flexible HC electrodes. The use of MXene nanosheets eliminates the need for all the electrochemically inactive components in the conventional polyvinylidene fluoride–bonded HC electrode, including polymer binders, conductive additives, and current collectors. In MXene‐bonded HC electrodes, conductive and hydrophilic MXene 2D nanosheets construct a 3D network, which can effectively stabilize the electrode structure and accommodate the volume expansion of HC during the charge/discharge process, leading to an enhanced electrode capacity and excellent cycle performance as anodes for both SIBs and PIBs. Benefiting from the 3D conductive network, the MXene‐bonded HC film electrodes also present improved rate capability, indicating MXene is a very promising multifunctional binder for next‐generation flexible secondary rechargeable batteries.

Mechanism on the Frictional Properties of Hard Carbon Films Derived from Consideration of Frictional Properties of CN<sub>x</sub> Film

Mechanism on the Frictional Properties of Hard Carbon Films Derived from Consideration of Frictional Properties of CN<sub>x</sub> Film

Investigation of parameters of plasma generated by high-power impulse magnetron sputtering (HiPIMS) of graphite

High-power impulse magnetron sputtering (HiPIMS) of graphite is used for deposition of hard and wear-resistant amorphous carbon films, because tetragonal diamond-like carbon (DLC) bonds produced under subplantation mechanism at negative substrate bias voltage more intensive in the case of high-density plasma. In scientific literature one can find the fact that DLC films are more hard (37 GPa) in the case of short (7 μs) magnetron discharge pulses comparing to long (50 μs) ones (17 GPa) in HiPIMS of graphite. Likely, it is connected with denser plasma and more effective carbon subplantation in the case of short discharge pulses compared to long ones. To confirm this, it is necessary to investigate dependencies of plasma parameters (ion concentration, electron temperature, plasma and floating potentials) generated by HiPIMS of graphite on discharge pulse width. It was shown that electron temperature increased from 5.34 to 10.27 eV, and plasma density increased from 1.2⋅1010 to 2.2⋅1010 cm−3 while pulse width decreased from 100 to 15 μs. It can be explained by increase of plasma disequilibrium since pulse current and power density increased to 250 A and 39.4 W/cm2, respectively.

Facile synthesis of free-standing, flexible hard carbon anode for high-performance sodium ion batteries using graphene as a multi-functional binder

The use of reduced graphene oxide (rGO) as an environmentally friendly, multi-functional conductive binder is proposed as a novel strategy for manufacturing free-standing, flexible, high-performance hard carbon anodes for sodium ion batteries (NIBs). Compared with the conventional electrodes fabricated with insulating, fluorine-containing polymer binder (PVDF), the unique two-dimensional structure enable rGO can act as a strong binder and flexible backbone, resulting in free-standing, flexible hard carbon film, which can be directly used as anode for sodium ion batteries without any current collector. What's more, rGO also acts as active material, providing Na-storage capacity, as well as conductive addition to construct 3D conductive network, improving the rate performance of hard carbon. The obtained rGO-bonded hard carbon film with excellent flexibility can deliver a high reversible electrode capacity up to 372.4 mA h g−1. After 200 charging/discharging cycles, the capacity loss is only 9%. The good electrochemical performance and excellent flexibility, combined with its facile fabrication approach make it to be a promising electrode candidate for developing next-generation flexible and environmentally friendly energy storage devices.

Microstructures and tribological properties of GLC coated 100Cr6 bearing steels

Low friction and hard amorphous carbon films were fabricated on 100Cr6 bearing steels via the unbalanced magnetron sputtering method. This paper studied the effect of graphite-like carbon (GLC) coatings on the wear resistance of 100Cr6, which are widely used in textile rings. The microstructures of the GLC coatings were investigated using scanning electron microscope (SEM), atomic force microscope (AFM), energy dispersive Spectrometer (EDS) and Raman. A comparative analysis using a ball-on-disc tribometer was carried out on 100Cr6 bearing steels with GLC coatings and those that had chromium-electroplated coatings. It was demonstrated that the GLC films on 100Cr6 presented better tribological properties, and the corresponding wear mechanisms were investigated. The tribological properties of GLC films under cryogenic treatment (−196 °C), annealing at temperatures of 300 °C and 350 °C were characterized. It was revealed that the friction coefficients decreased after using three kinds of treatments above.

Structure and friction properties of laser-patterned amorphous carbon films

In the paper we report on laser surface modification of super hard micrometer-thick tetrahedral amorphous carbon (ta-C) films in the regime of single-shot irradiation with KrF laser pulses (wavelength 248nm, pulse duration 20ns), aimed at investigations of the laser-induced changes of the structure and surface properties of the ta-C films during graphitization and developing ablation processes. Based on the analysis of surface relief changes in the laser-irradiated spots, characteristics of the single-shot graphitization and ablation of the 2-μm-thick ta-C film are determined. Using Raman spectroscopy, it is found that during the graphitization regime the structure transformation and growth of graphitic clusters occur according to the relationship I(D)/I(G)∝La2, but after reaching the ablation threshold the Tuinstra-Koenig relationship I(D)/I(G)∝1/La describes further growth of the graphitic cluster size (La) during developing ablation of the ta-C film with nanosecond pulses. The maximal size of graphitized clusters is estimated as La=4–5nm. The studies of nanomechanical properties of laser-patterned ta-C films using the lateral force microscopy and force modulation microscopy have evidenced lower friction forces (between diamond-coated tips and film surface) and lower stiffness in the laser-graphitized areas. The laser-produced graphitic layer acts as a solid lubricant during sliding of the diamond-coated tips on the ta-C film surface in ambient air (~50% RH); the lubricating role of adsorbed water layers is suggested to be significant at low loads on the tips. The results of this work demonstrate that the UV laser surface texturing in the regime of graphitization is a promising technique to control the friction and surface elasticity of super hard amorphous carbon films on the micro and nanoscale.

The Role of Ambient Gas and Pressure on the Structuring of Hard Diamond-Like Carbon Films Synthesized by Pulsed Laser Deposition

Hard carbon thin films were synthesized on Si (100) and quartz substrates by the Pulsed Laser Deposition (PLD) technique in vacuum or methane ambient to study their suitability for applications requiring high mechanical resistance. The deposited films’ surface morphology was investigated by scanning electron microscopy, crystalline status by X-ray diffraction, packing and density by X-ray reflectivity, chemical bonding by Raman and X-ray photoelectron spectroscopy, adherence by “pull-out” measurements and mechanical properties by nanoindentation tests. Films synthesized in vacuum were a-C DLC type, while films synthesized in methane were categorized as a-C:H. The majority of PLD films consisted of two layers: one low density layer towards the surface and a higher density layer in contact with the substrate. The deposition gas pressure played a crucial role on films thickness, component layers thickness ratio, structure and mechanical properties. The films were smooth, amorphous and composed of a mixture of sp3-sp2 carbon, with sp3 content ranging between 50% and 90%. The thickness and density of the two constituent layers of a film directly determined its mechanical properties.

Protective double-layer coatings prepared by plasma enhanced chemical vapor deposition on tool steel

Hydrogenated diamond-like carbon films were prepared on high-speed steel substrates using low pressure radio-frequency capacitively coupled discharge (13.56MHz) using methane mixed either with hydrogen or argon. A dc self-bias was induced by the rf discharge and accelerated the ions towards the substrates during the whole deposition process. Prior to the carbon film deposition and to improve the adhesion, the substrates were subject to plasma nitriding and coated with a silicon oxide layer using the same reactor. The deposited films were optically characterized (UV-IR) and by using a combination of Rutherford backscattering spectroscopy and elastic recoil detection the atomic composition was determined. The carbon films high hardness (~18GPa) was assessed from indentation tests. Adhesion tests revealed critical loads up to 13.6N for the carbon films deposited on steel substrates using silicon oxide interlayer. Friction coefficient varied from 0.02 against diamond and 0.23 against steel counterpart. The results suggest that hard carbon films can be deposited on steel substrate using a silicon oxide intermediate layer deposited by the same plasma process with commercial potential.

Plasma Treatments for Metallic Surface Modification to Obtain Highly Adherent Diamond-Like Carbon Coatings

The obtained results of the deposition of hard and adherent diamond-like carbon (DLC) films on four metal substrates, stainless steels AISI 304 and ASTM F138, carbon steel AISI 1020, and Ti6Al4V alloy, are presented. The DLC films were deposited using a modified pulsed-dc plasma enhanced chemical vapor deposition technique. With the aim to improve the film adhesion, surface modification like nitriding, carbonitriding, and carburizing were used previously to DLC film depositions. Strong DLC films' stress dependence of the plasma treatments was observed. The stress reduction suggests an increase in the DLC films adherence to metallic substrate. Tribological tests also confirmed these results.

The effect of oil temperature and additive concentration on the wear of non-hydrogenated DLC coating

Diamond-like carbon (DLC) coatings are amorphous hard carbon films which offer excellent mechanical and tribological properties. Recently, these coatings have been applied to engine and powertrain components in passenger cars, including those under boundary lubricated conditions. Tribological performance of DLC coatings in oil lubricated conditions and their interaction with various lubricant additives are very complex due to the variety of DLC coatings and lubricants. In this study, the effects of oil temperature and additive concentration on the wear and friction performance of non-hydrogenated tetrahedral amorphous carbon (ta-C DLC) coating have been investigated. Tribological tests were conducted using a pin-on-disc tribotester with ta-C DLC coated steel pins sliding against non-coated steel discs. Tribological tests were also carried out between DLC coated pin against germanium disc in base oil for clarification of wear mechanism. The ta-C coating gave very low boundary friction with base oil at 50°C but the coating experienced limited durability with increased wear rate at higher temperature against steel disc. Organic friction modifier glycerol-mono-oleate was able to preserve low friction behavior of the coating at higher temperature with enhanced durability. The anti-wear additive Zinc Dialkyldithiophosphate (ZnDTP) provided excellent wear protection for the ta-C coating due to the formation of thick pad-like tribofilm on steel counterpart at all temperature ranges but rubbing in ZnDTP additivated oil lead to higher friction coefficient. The results obtained at high temperature show the significant and beneficial influence of oil additives on the wear performance of the coating. Based on the obtained results and analysis, the wear performance of non-hydrogenated DLC was found to have a clear dependence on the concentration of the lubricant additives, test temperature and counter material.

Principles for designing sputtering-based strategies for high-rate synthesis of dense and hard hydrogenated amorphous carbon thin films

In the present study we contribute to the understanding that is required for designing sputtering-based routes for high rate synthesis of hard and dense amorphous carbon (a-C) films. We compile and ...

W261003 硬質炭素膜の摺動特性とはく離の評価([W26100]標準事業委員会,機素潤滑設計部門,機械材料・材料加工部門企画,コーティング全般の評価方法・標準化の現状と課題)

W261003 硬質炭素膜の摺動特性とはく離の評価([W26100]標準事業委員会,機素潤滑設計部門,機械材料・材料加工部門企画,コーティング全般の評価方法・標準化の現状と課題)