CH4 Flow Rate Research Articles

Corrosion and tribological behaviour in a 3.5% NaCl solution of vacuum arc deposited ZrCN and Zr–Cr–Si–C–N coatings

ZrCN and Zr–Cr–Si–C–N coatings were deposited on Si (100) and 316L stainless steel substrates using the cathodic vacuum arc technique in a mixed atmosphere of C2H2 and N2. The coatings were grown keeping almost constant the ratio of the C2H2 and N2 mass flow rates, substrate bias and deposition temperature at ∼0.81, −200 V and 320 ℃, respectively. The investigation carried out aimed to determine the corrosion and tribological performance of the novel Zr–Cr–Si–C–N coating obtained by Cr and Si addition to the ZrCN reference coating. The films were characterized in terms of elemental and phase composition, crystalline structure, hardness, reduced elastic modulus and adhesion. Particular attention was devoted to the investigation of coatings' corrosion resistance and tribological performance carried out in a 3.5% NaCl solution. Cr and Si addition to ZrCN coating leads to reduction in film crystallinity, finer microstructure, enhanced corrosion resistance and better tribological performance under corrosive testing conditions. In this paper, we discuss the measured mechanical and tribological properties of the two coatings in terms of various ratios of hardness and reduced elastic modulus. The coated samples exhibited high corrosion protection efficiency, reaching 97.8% for the Zr–Cr–Si–C–N coating. Both coatings improved the tribological performance of 316L steel in the saline solution. Specifically, the addition of Cr and Si into ZrCN coating results in a decrease of the wear rate of about 60%.

Electronic-structure, corrosion and mechanical properties of nc-CrC/a-C:H films deposited by multi-arc ion plating

Nanocomposite films consisting of a hard nano-crystalline chromium carbide phase and amorphous carbon matrix (nc-CrC/a-C:H) were fabricated using multi-arc ion plating system. The series of films were deposited in various acetylene (C2H2) flow rates ranging from 50 to 150 standard cubic centi-meter per minute (sccm). The ingredient contents, microstructures, corrosion properties, mechanical characteristics and tribological behaviors of the nc-CrC/a-C:H films were investigated carefully as a function of the C2H2 flow rate. X-ray and ultraviolet photoelectron spectroscopies were performed to explain the intrinsic origin of the excellent properties of nc-CrC/a-C:H films from the viewpoint of chemical bonding and electronic-structure. The results showed the films were formed as nano-scale metastable cubic CrC (grain size of 2–10 nm) embedded in the hydrogenated amorphous carbon (a-C:H) matrix. As the flow rate increased, the content of a-C sp2 increased while the content of CrC decreased. The valence charge transfer at the interface between a-C:H and nc-CrC makes parts of the C-Cr bonds more ionic. The density of such charge transfer was quantified by the C-Cr*/C-Cr ratio. The charge transfer was further verified by the valence band of the films. The results indicated an obvious impact of the density of valence charge transfer on corrosion and mechanical properties. A relatively low density of charge transfer and high work function could result in an enhanced corrosion resistance of the films. A lower vacancies density caused by valence charge transfer could also strengthen the hardness. The change of the density of charge transfer could be attributed to the metallic chromium content in the films. Thus, we can open up a new possible pathway to design the nc-CrC/a-C:H films for applications.

Enhancement of toughness and wear resistance by CrN/CrCN multilayered coatings for wood processing

The coatings applied onto woodworking tools must possess higher hardness, adhesion, and fracture toughness. The CrN/CrCN multilayered coatings are deposited on M2 high-speed steel (HSS) and Si (100) by cathodic arc evaporation with different C2H2 flow rates and characterized systematically. The addition of carbon to the CrN coatings can enhance the toughness of coatings and the H/E ratio. The H/E and H3/E2 ratios reach 0.085 and 0.176, respectively. The maximum nanohardness of the coatings is 24 GPa and the smallest friction coefficient is 0.48 together with the higher adhesion between the coating and substrate (HF1). Larger C2H2 flow rate can produce porous and loose microstructure with poor mechanical properties. The lifetime of the CrN/CrCN-coated blades made of high speed steel and cemented carbide materials is increased by about 33% and 7% respectively compared to that of CrN-coated blades, and by 170% and 110% compared to that of uncoated blades.

MICROSTRUCTURE AND DIELECTRIC PROPERTIES OF SILICON CARBONITRIDE DIELECTRIC BARRIER FILMS DEPOSITED BY SPUTTERING

Silicon carbon nitride (SiCN) films were prepared on silicon substrate by reactive magnetron sputtering of a sintered silicon carbide target in a mixture of argon, nitrogen and acetylene. Detailed studies including energy dispersive spectrometer, atomic force microscope, X-ray diffraction, Fourier transformed infrared spectrometry and [Formula: see text]–[Formula: see text] measuring instrument were performed. The as-deposited SiCN films do not exhibit obvious crystalline phase, and the SiCN films annealed at 600[Formula: see text]C show SiC crystal and graphite carbon. The SiCN films mainly consist of Si–N, Si–C, Si–O, C–C, C[Formula: see text]N, Si–Hn and N–Hn bonds, and increasing C2H2 flow rate promotes the formation of C–C, N–Hn and Si–N bonds. The SiCN film with low dielectric constant of 3.8 and compact structure was successfully prepared.

Energy analysis and optimization of hollow fiber membrane contactors for recovery of dissolve methane from anaerobic membrane bioreactor effluent

This work presents an energy analysis and optimization of the hollow fiber membrane contactors for the recovery of dissolved methane (CH4) in effluents of anaerobic membrane bioreactor wastewater treatment processes. The obtained CH4 could be merged with biogas for further purification or used with a micro-turbine for electricity generation to achieve an energy self-sufficient wastewater treatment process. A mathematical model considering simultaneous CH4 and carbon dioxide (CO2) desorption was used to estimate the membrane area required to remove the dissolved CH4, as well as quality of the outlet gas from the membrane contactor. Energy balance between electrical energy obtained from the recovered CH4 and energies consumed by vacuum and liquid pumps for the operation of membrane contactor were investigated and reported as a Net Electricity obtained per m3 of effluent or simply Net E. Results revealed that a combination of a high strip gas flow rate and slightly low vacuum condition closed to the atmospheric pressure can provide the highest Net E at 0.178 MJ/m3. This value is 85.37% of the total electrical energy that can generated from a 90% recovery of dissolved CH4 using an effluent saturated with a 60 vol% CH4 biogas and flow rate at 2 m3/day. The calculation was made based on the assumptions that 1) the membrane contactor is operated in a non-wetting mode where membrane properties remain constant, 2) flux decline due to the membrane fouling is not considered and 3) the energy required for membrane cleaning and other relevant activities are not factored into the energy analysis. Based on our results, to obtain a high CH4 mole fraction at the gas outlet, a low strip gas flow rate is recommended, however, the operating gas pressure needs to be lowered by applying a vacuum condition to improve the Net E. In addition, it was found that the Net E could be improved by increasing the number of membrane fibers, and lowering the liquid flow rate. The CH4 recovery efficiency could also be optimized to obtain an optimal Net E.

Stability map and shape of premixed CH4/O2/CO2 flames in a model gas-turbine combustor

Oxy-fuel combustion was investigated in a model combustor that mimics the geometry of operational air-fuel gas-turbine combustors implementing the LPM DLE DACRS technology (Lean Premixed, Dry Low Emissions, Dual Annular Counter-Rotating Swirlers). Premixed swirl-stabilized CH4/O2/CO2 flames were tested over ranges of equivalence ratio (φ = 0.2–1.0) and oxygen fraction (OF = 25–70%). The non-preheated flow rates of CH4, O2, and CO2 were adjusted for each flame to maintain a common bulk velocity of 5.2 m/s at burner throat throughout the entire study. The combustor stability map was identified by quantifying the flashback and blowout limits within the φ-OF space. The adiabatic flame temperature (Tad) was also mapped over the same ranges. Selected flames were imaged to analyze the effects of φ, OF, and Tad on flame shape. Interestingly, at constant inlet bulk velocity, the flashback and blowout limits were found to follow contours of constant Tad, which is a novel finding for oxy-methane flames. This indicated that Tad is a more relevant parameter choice than φ or OF to quantify the combustor stability map. It was also found that a single correlation exists between flame speed and Tad, with greater speeds at higher temperatures towards flashback. No similar correlation was found between flame speed and combustor power density, throat Reynolds number, or bulk mass flow rate. Flames of the same Tad demonstrated almost identical shapes, which is another novel finding for oxy-methane flames. OF and φ showed very similar individual effects on flame shape, because both parameters can be represented by Tad. Spanning the stable combustion zone from lower Tad values to higher ones was observed to reduce flame size significantly.

Mechanism of high growth rate for diamond-like carbon films synthesized by helicon wave plasma chemical vapor deposition

A high growth rate fabrication of diamond-like carbon (DLC) films at room temperature was achieved by helicon wave plasma chemical vapor deposition (HWP-CVD) using Ar/CH4 gas mixtures. The microstructure and morphology of the films were characterized by Raman spectroscopy and scanning electron microscopy. The diagnosis of plasma excited by a helicon wave was measured by optical emission spectroscopy and a Langmuir probe. The mechanism of high growth rate fabrication for DLC films by HWP-CVD has been discussed. The growth rate of the DLC films reaches a maximum value of 54 μm h−1 at the CH4 flow rate of 85 sccm, which is attributed to the higher plasma density during the helicon wave plasma discharge. The CH and Hα radicals play an important role in the growth of DLC films. The results show that the Hα radicals are beneficial to the formation and stabilization of C=C bond from sp2 to sp3.

Kinetics of simultaneous oxidation of CO‐CH4 over Pd‐K promoted NiCo2O4/γ‐Al2O3 catalyst

An optimum formulation of 0.1 %Pd‐2 %K40 %NiCo2O4/Al2O3 spinel catalyst was found for the total oxidation of CO‐CH4 mixture at the lowest temperature of 330 °C, which has never been reported before. No reaction kinetics have been reported for simultaneous catalytic oxidation of CO‐CH4 mixture in the literature. In this paper, intrinsic kinetics for oxidation of CO‐CH4 mixture over the spinel catalyst were presented. The experimental data were collected in a plug flow differential reactor at steady state in the kinetic controlled regime under the following reaction conditions: catalyst weight 0.1–0.5 g, flow rate of CO and CH4 1.5 mL/min each in air with total flow of 100 mL/min, temperature range 318–333 K, and reactant conversion < 15 %. The experimental data collected in the regime free from heat and mass transfer limitations were fitted adequately by the power law rate model. The orders of the simultaneous oxidation reactions were found to be 1.05 and 1.12 with respect to CO and CH4 in the mixture respectively. The apparent activation energies for CO and CH4 oxidation were 54.6 and 26.11 kJ/mol respectively.

Silicon carbonitride thin films deposited by reactive high power impulse magnetron sputtering

Amorphous silicon carbonitride thin films for biomedical applications were deposited in an industrial coating unit from a silicon target in different argon/nitrogen/acetylene mixtures by reactive high power impulse magnetron sputtering (rHiPIMS). The effects of acetylene (C2H2) flow rate, substrate temperature, substrate bias voltage, and HiPIMS pulse frequency on the film properties were investigated. Low C2H2 flow rates (<10sccm) resulted in silicon nitride-like film properties, seen from a dense morphology when viewed in cross-sectional scanning electron microscopy, a hardness up to ∼22GPa as measured by nanoindentation, and Si-N bonds dominating over Si-C bonds in X-ray photoelectron spectroscopy core-level spectra. Higher C2H2 flows resulted in increasingly amorphous carbon-like film properties, with a granular appearance of the film morphology, mass densities below 2g/cm3 as measured by X-ray reflectivity, and a hardness down to 4.5GPa. Increasing substrate temperatures and bias voltages resulted in slightly higher film hardnesses and higher compressive residual stresses. The film H/E ratio showed a maximum at film carbon contents ranging between 15 and 30at.% and at elevated substrate temperatures from 340 °C to 520 °C.

Characterization of particle generated during plasma-enhanced chemical vapor deposition on amorphous carbon layer using particle beam mass spectrometer

Nanoscale particles that can affect the process yield were generated using the plasma-enhanced chemical vapor deposition (PECVD) process. A particle beam mass spectrometer is remarkably useful to understand particle behavior in a reactor. The properties of nanoscale particles obtained from the exhaust line of PECVD during amorphous carbon layer (ACL) growth under various growth conditions were investigated. The number concentration and the size of the nanoscale particles generated were quite sensitive to growth parameters such as radio frequency (RF) plasma power, C2H2, and dopant (i.e., NH3 and B2H6) gas flow rate. For an ACL growth at higher RF plasma power, the average size of the nanoscale particles decreased as the number concentration of particles increased while they are opposingly increased in particle size and decreased in concentration for a higher C2H2 flow rate. A reduction in both the average nanoscale particle size and their number concentration occurred when NH3 gas was used for nitrogen-doped ACL. By contrast, ACL growth with increasing B2H6 gas flow for boron-doped ACL exhibited a larger average nanoscale particle size and number concentration. The particle number concentration was in the range of 106–108 cm−3 with average particle sizes of 100–400 nm. According to this study, the measurement of real-time particle size distribution can help to minimize the number of generated particles and optimize the ACL deposition process.

Optical and mass spectroscopic properties of microwave CH4/H2/Ar plasma for diamond deposition in a resonance cavity

The properties of microwave CH4/H2/Ar plasma for diamond deposition in a resonant cavity have been investigated by optical emission spectroscopy (OES) and quadrupole mass spectroscopy (QMS). Ar emission intensity decreases monotonically with gas pressure, where electron impact excitation plays an important role. Hα. CH and C2 intensities exhibit the different pressure dependences, which decrease at first and then rise with the further increasing of gas pressure, suggesting the change of electron activation mechanism to thermally driven chemistry for the formation of excited reactive hydrocarbon species at high gas pressures. The addition of small amounts of CH4 to the H2/Ar plasma causes increases in emissions of Hα and CH generated from the CH4 dissociation. With further increase of CH4 flow rate, both emissions and abundances of 2-carbon species enhance, while a reduced intensity of CH emission is observed, reflecting the complex dissociation and dimerization reactions of hydrocarbon species. The dissociation of CH4 is enhanced in plasma under higher power condition. A slight change can be observed in both emission and abundance of hydrocarbon species with increasing Ar flow rate.

Fast deposition of thick diamond-like carbon films by ion-beam technique

A diamond-like carbon film doped with TiC nanocrystallites (TiC–DLC) with a thickness of 35.8 μm was successfully prepared on a stainless steel substrate by employing a combination of metal vapor vacuum arc and filtered cathode vacuum arc techniques. A maximum deposition rate of 0.25 μm/min was achieved for TiC–DLC films. The structure and properties of the TiC–DLC films were systematically analyzed using different methods such as transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, X-ray diffraction, and friction and wear tests. The results indicated that typical a-C:H films containing nano-sized TiC grains were deposited which exhibit improved mechanical properties such as high cohesive strength, Vickers hardness, and capacity against high temperature. Parameter windows for C2H2 flow rate and solenoid current were also provided for the deposition of TiC–DLC films to meet the requirements for using the material for specific commercial applications.

Defect Emission and Optical Gain in SiCxOy:H Films.

Luminescent SiCxOy:H films, which are fabricated at different CH4 flow rates using the plasma-enhanced chemical vapor deposition (PECVD) technique, exhibit strong photoluminescence (PL) with tuning from the near-infrared to orange regions. The PL features an excitation-wavelength-independent recombination dynamics. The silicon dangling bond (DB) defects identified by electron paramagnetic resonance spectra are found to play a key role in the PL behavior. The first-principles calculation shows that the Si DB defects introduce a midgap state in the band gap, which is in good agreement with the PL energy. Moreover, the band gap of a-SiCxOy:H is found to be mainly determined by Si and C atoms. Thus, the strong light emission is believed to result from the recombination of excited electrons and holes in Si DB defects, while the tunable light emission of the films is attributed to the substitution of stronger Si-C bonds for weak Si-Si bonds. It is also found that the light emission intensity shows a superlinear dependence on the pump intensity. Interestingly, the film exhibits a net optical gain under ultraviolet excitation. The gain coefficient is 53.5 cm-1 under a pumping power density of 553 mW cm-2. The present results demonstrate that the SiCxOy system can be a very competitive candidate in the applications of photonics and optoelectronics.

Carbon Co-Deposition During Gas Reduction of Water-Atomized Fe-Cr-Mo Powder

AbstractThe water atomization of iron powder with a composition of Fe-3Cr-0.5Mo (wt.%) at 1600°C and 150 bar creates an oxide layer, which in this study was reduced using a mixture of methane (CH4) and argon (Ar) gas. The lowest oxygen content was achieved with a 100 cc/min flow rate of CH4, but this also resulted in a co-deposition of carbon due to the cracking of CH4. This carbon can be used directly to create high-quality, sinter hardenable steel, thereby eliminating the need for an additional mixing step prior to sintering. An exponential relationship was found to exist between the CH4gas flow rate and carbon content of the powder, meaning that its composition can be easily controlled to suit a variety of different applications.

In situ-grown silicon quantum dots in SiCx:H/a-C:H hetero-multilayer films prepared by plasma enhanced chemical vapor deposition method

Silicon quantum dots (Si QDs) were grown in situ in SiCx:H/a-C:H hetero-multilayer films at a low substrate temperature using a radio frequency (13.56 MHz) plasma enhanced chemical vapor deposition (PECVD) method. The component and bonding configuration of the SiCx:H/a-C:H hetero-multilayer films have been systematically investigated by Raman, FTIR and HRTEM testing techniques. The results show that there are amorphous Si QDs in SiCx:H/a-C:H hetero-multilayer films. Without high temperature post-deposition annealing treatments, as increasing CH4 flow rate, the coexistence of amorphous Si QDs and silicon nanocrystals in SiCx:H matrix layers has been confirmed by Raman, HRTEM and FTIR measurements. X-ray photoelectron spectroscopy and UV–Vis spectrometry measurements show that the a-C:H layer is mainly consisted of the sp2-bonded and sp3-bonded carbon atoms and its optical band gap is 1.63 eV. The smaller optical band gap suggested that SiCx:H/a-C:H hetero-multilayer films can reduce the barrier height between Si QDs and barrier layer in vertical direction as compared with SiCx/SiC multilayer films.

Isothermal Reaction of NiO Powder with Undiluted CH4 at 1000 K to 1300 K (727 °C to 1027 °C)

In this study, isothermal reaction behavior of loose NiO powder in a flowing undiluted CH4 atmosphere at the temperature range 1000 K to 1300 K (727 °C to 1027 °C) is investigated. Thermodynamic analyses at this temperature range revealed that single phase Ni forms at the input \( {{n_{{{\text{CH}}_{ 4} }}^{\text{o}} } \mathord{\left/ {\vphantom {{n_{{{\text{CH}}_{ 4} }}^{\text{o}} } {\left( {n_{{{\text{CH}}_{ 4} }}^{\text{o}} + n_{\text{NiO}}^{\text{o}} } \right)}}} \right. \kern-0pt} {\left( {n_{{{\text{CH}}_{ 4} }}^{\text{o}} + n_{\text{NiO}}^{\text{o}} } \right)}} \) mole fractions (\( X_{{{\text{CH}}_{ 4} }} \)) between ~0.2 and 0.5. It was also predicted that free C co-exists with Ni at \( X_{{{\text{CH}}_{ 4} }} \) values higher than ~0.5. The experiments were carried out as a function of temperature, time, and CH4 flow rate. Mass measurement, XRD and SEM-EDX were used to characterize the products at various stages of the reaction. At 1200 K and 1300 K (927 °C and 1027 °C), the reaction of NiO with undiluted CH4 essentially consisted of two successive distinct stages: NiO reduction and pyrolytic C deposition on pre-reduced Ni particles. At 1200 K (927 °C), 1100 K (827 °C), and 1000 K (727 °C), complete oxide reduction was observed within ~7.5, ~17.5, and ~45 minutes, respectively. It was suggested that NiO was essentially reduced to Ni by a CH4 decomposition product, H2. Possible reactions leading to NiO reduction were suggested. An attempt was made to describe the NiO reduction kinetics using nucleation-growth and geometrical contraction models. It was observed that the extent of NiO reduction and free C deposition increased with the square root of CH4 flow rate as predicted by a mass transport theory. A mixed controlling mechanism, partly chemical kinetics and partly external gaseous mass transfer, was responsible for the overall reaction rate. The present study demonstrated that the extent of the reduction can be determined quantitatively using the XRD patterns and also using a formula theoretically derived from the basic XRD data.

Optical emission spectroscopic study of Ar/H2/CH4 plasma during the production of graphene nano-flakes by induction plasma synthesis

Graphene nano-flakes using CH4 precursor were synthesized in a radio frequency inductively coupled plasma reactor with in-situ investigation of Ar/H2/CH4 plasma by optical emission spectroscopy at fixed H2 and Ar flow rates of 4 and 75 slpm, respectively, and at different plate powers (12 to 18 kW), pressures (400 to 700 mbar) and CH4 flow rates (0.3 to 2 slpm). Emissions from C2 Swan band, C3, CH and H2 are observed in the optical emission spectra of Ar/H2/CH4 plasma. Plasma temperature estimated analyzing the C2 Swan band emission intensities is found to be decreased with increasing pressure and decreasing plate power. The decreasing plasma temperature gives rise to increase in production rate due to increase in condensation process. The production rate is observed to be increased from 0 to 0.3 g/h at 18 kW and from 0 to 1 g/h at 15 kW with increase in pressure from 400 to 700 mbar at fixed CH4 flow rate of 0.7 slpm. Broad band continuum emission appears in the emission spectra at specific growth conditions in which the formation of vapor phase nanoparticles due to condensation of supersaturated vapor is facilitated. The production rate at 12 kW, 700 mbar, and 0.7 slpm of CH4 flow rate is found to be 1.7 g/h which is more than that at 15 and 18 kW. Thus, the broadband continuum emission dominates the optical emission spectra at 12 kW due to lower temperature and higher production rate, and is attributed to the emission from suspended nanoparticles formed in vapor phase. The synthesized nanoparticles exhibit flake like structures having average length and width about 200 and 100 nm, respectively, irrespective of the growth conditions. Nano-flakes have thickness between 3.7 to 7.5 nm and are composed of 11 to 22 graphene layers depending on the growth conditions. The intensity ratio (ID/IG) of D and G band observed in the Raman spectra is less than 0.33 which indicates good quality of the synthesized graphene nano-flakes.

Methane dissociation process in inductively coupled Ar/H2/CH4 plasma for graphene nano-flakes production

The role of hydrogen and methane dissociation process in induction plasma synthesis of graphene nano-flakes (GNF) is studied by the optical emission spectroscopy of Ar/H2/CH4 plasma. The condensation of C2 species formed due to methane decomposition produces GNF, which depends on pressure. Electron impact and dehydrogenation processes dissociate methane, which promotes and hinders the GNF production, respectively. The effect of hydrogen is insignificant on quality, size and morphology of the GNF. The CH4 flow rate has no influence on particle temperature but has effect on cooling rate at the point of nucleation and, therefore, on production rate and thickness of GNF.

Thick diamond like carbon coatings deposited by deep oscillation magnetron sputtering

Hydrogenated diamond like carbon (DLC) coatings with thicknesses up to 20μm have been deposited on metal substrates by sputtering a graphite target in argon (Ar) and acetylene (C2H2) mixture using deep oscillation magnetron sputtering (DOMS). The coatings were deposited under moderate peak target current densities (0.47 to 0.6Acm−2) and a low bias voltage of −60V, to achieve dense microstructure but avoid building up of high residual stresses. Higher peak substrate current densities and deposition rates were found when C2H2 was introduced. The effects of the C2H2 flow rate (fC2H2) on the deposition rate, microstructure, adhesion, mechanical and tribological properties of the DLC coatings were studied by means of scanning electron microscopy, Raman spectroscopy, HRC indentation, nanoindentation, dry ball-on-disk test, and block-on-ring test in SAE 10W-30 engine lubricant. The coatings showed low compressive stresses in the range of −0.5GPa to −1.8GPa. The coatings exhibited dense structure, high sp3/sp2 ratio, and excellent wear resistance when the C2H2 flow rate was in the range of 10–20sccm (4%–8% of the total gas flow). The friction and wear behavior of the DOMS DLC coatings both in the ambient air and SAE 10W-30 engine lubricant showed positive results in terms of friction and wear reduction.

The composition, microstructure and mechanical properties of Ni/DLC nanocomposite films by filtered cathodic vacuum arc deposition

In this paper, Ni/DLC nanocomposite films were deposited on the un-heated silicon (100) by the filtered cathodic vacuum arc deposition (FCVAD) under different CH4 and C2H2 flow rates. The composition, microstructure and mechanical properties of the Ni/DLC films were investigated by scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and nanoindentation. The Ni/DLC films typically consisted of nickel nanograins around 11nm, which were embedded in amorphous carbon matrix with the thickness of 0.35–2.8nm. The film structure and the mechanical properties are strongly affected by the precursor gas type and flow rate. The porous structure, with the nanopore size equaling to the nickel grain size, can be seen after the etching process of the as-deposited film, providing a possible method for the preparation of nanoporous DLC films. A maximum hardness of 13.2GPa and 21.64GPa is achieved for the Ni/DLC films under the CH4 flow rate of 30sccm and C2H2 flow rate of 40sccm, respectively, under which the maximum thickness of the amorphous carbon phase is also obtained.