Carbon Films Research Articles

Polymer-like hydrogenated amorphous carbon thin films fabricated by plasma-enhanced chemical vapor deposition of cyclohexane precursor

Hydrogenated amorphous carbon (a-C:H) films were fabricated by plasma-enhanced chemical vapor deposition (PECVD) of a cyclohexane precursor at ambient temperature at varying deposition pressures from 19.73 to 38.00 Pa and varying plasma powers from 20 to 80 W. The deposition rate of the a-C:H films was strongly dependent on the deposition conditions. The films were all optically transparent with extinction coefficient below 0.0042. The refractive index as an indicator of the film's density varied depending on the deposition conditions. Their surfaces were all hydrophobic regardless of the deposition conditions. The a-C:H films had wide optical bandgaps ranging from 3.09 to 3.69 eV. The refractive index and FTIR spectra were consistent with those of polymer-like a-C:H films. As the deposition pressure decreased and plasma power increased, the intensity of a dominant peak of CHx stretching mode in the FTIR spectra decreased. The relative hydrogen content of the a-C:H films was estimated from an FTIR analysis and determined to have an inverse relationship with refractive index. These results indicated that the formation of more energetic plasmas during deposition at lower pressures and higher plasma powers led to the a-C:H films with reduced hydrogen content and increased density. The observed film properties could be advantageous for several applications, particularly as protective, wear-resistant, low-friction, or anti-reflective coatings for optical windows.

Improving corrosion and conductivity of Ti-doped amorphous carbon film coated on 316L stainless steel bipolar plates by nitrogen atoms doping

Amorphous carbon films have recently attracted extensive attention as surface functional films for bipolar plates with excellent conductivity and anti-corrosion properties. In this research, to determine the influence of the amorphous carbon film doped with titanium and nitrogen on the efficiency of proton exchange membrane fuel cells (PEMFCs) and clarify the effect of N atoms on Ti doped amorphous carbon, a series of Ti, N co-doped amorphous carbon films are built on 316L stainless steel at different N2 flow rates. This study provides detailed research about the influence of N atoms content on the microstructure, morphology evolution, corrosion resistance and interfacial contact resistance (ICR) of Ti, N co-doped amorphous carbon films. The results reveal that the N doping of the Ti-doped amorphous carbon film has the potential to enhance the C-sp2 content and refine the grain. The characterization results indicate that introducing N atoms into Ti doped amorphous carbon can reduce the ICR of the film to 2.38 mΩ cm2. The introduction of N atoms can also enhance the anti-corrosive characteristics of the titanium singly doped amorphous carbon film. The Ti, N co-doped film can be used as candidate materials applied to metal bipolar plates.

Atomic-scale understanding on the influence of sliding angle on the interfacial structure and friction behavior of textured amorphous carbon films

Textured amorphous carbon (T:a-C) films have received great attention in the fields of hard drives, MEMS, and NEMS due to their excellent tribological properties. However, there is still a lack of research on the dependence of its friction behavior on different sliding angles. Especially, owing to the limitations of in-situ characterization in capturing the friction interface information, the potential friction mechanisms are still unclear. Hence, in this work T:a-C film with a rectangular shape was constructed and the impact of different sliding angles on friction behavior under dry friction condition was mainly explored through reactive molecular dynamics simulation. Results unveil that the friction properties of T:a-C films are closely dependent on the sliding angle. When the sliding angle increases from 0° to 45°, the decrease in the number of CC covalent bonds at the friction interface weakens the interfacial crosslinking effect, leading to a decrease in the friction coefficient by 20.11 %. However, as the sliding angle further increases from 45° to 90°, an increase in friction coefficient is observed, which is due to the increase of unsaturated bond content, weakening the interface passivation effect. These results reveal the friction mechanism of T:a-C films, induced by sliding angle, and effectively guide the design and technical application of textured a-C films.

Effect of temperature on the friction behavior and mechanism of DLC film in CO2 foam fracturing environment

Diamond-like carbon (DLC) film is considered to be an attractive candidate material for reducing friction and wear in oil and gas equipment due to its low friction and high wear resistance. This study investigated the evolution of friction interfaces and tribochemical reaction at three different temperatures through reactive molecular dynamics simulations. The results reveal that the synergistic effect of atomic transfer layer and chemical passivation of DLC film leads to the decrease of friction force with increasing ambient temperature. The cumulative atomic transfer layer with increasing ambient temperature also contributes to the increase of wear amount, while the atomic lattice transition dominates friction temperatures. More importantly, the phenomenon of increased sp3 carbon atoms in DLC film is also temperature dependent.

Ultrathin carbon film as ultrafast rechargeable cathode for hybrid sodium dual-ion capacitor

The development of electrochemical energy storage devices has a decisive impact on clean renewable energy. Herein, novel ultrafast rechargeable hybrid sodium dual-ion capacitors (HSDICs) were designed by using ultrathin carbon film (UCF) as the cathode material. The UCF is synthesized by a simple low temperature catalytic route followed by an acid leaching process. UCF owns a large adsorption interface and number of additional active sites, which is due to the nitrogen doping. In addition, there exists several short-range order carbons on the surface of UCF, which are beneficial for anionic storage. An ultrafast rechargeable remarkable performance, remarkable anion hybrid storage capability and outstanding structure stability is fully tapped employing UCF as cathode for HSDICs. The electrochemical performance of UCF in a half-cell system at the operating voltage between 1.0 and 4.8 V, achieving an admirable specific discharge capacity of 358.52 mAh·g−1 at 500 mA·g−1, and a high capacity retention ratio of 98.42% after cycling 2500 times at 1000 mA·g−1, respectively. Besides, with the support of ex-situ TEM and EDS mapping, the structural stability principle and anionic hybrid storage mechanism of UCF electrode are investigated in depth. In the full-cell system, HSDICs with the UCF as cathode and hard carbon as anode also presents a super-long cycle stability (80.62% capacity retention ratio after cycling 1300 times at 1000 mA·g−1).

Interfacial tribochemical kinetics: A new perspective on superlubricity of diamond-like carbon films

Interfacial tribochemical kinetics: A new perspective on superlubricity of diamond-like carbon films

The mechanical and tribological properties of polyether ether ketone coated by diamond-like carbon film with plasma-induced transition layer

Polyether ether ketone (PEEK) has been broadly utilized in aerospace due to its excellent properties. Nevertheless, when applied as sealing components in harsh environments, virgin PEEK still faces defects in mechanical behavior and wear resistance. To address these issues, the deposition of diamond-like carbon (DLC) films has been employed as a viable solution. In this study, the DLC film with plasma-induced transition layer was fabricated on PEEK via direct current magnetron sputtering technology. Compared with previous studies, the evolutions of interfacial structures and plasma-induced layer were investigated, and their roles on the tribological performance of PEEK/DLC were analyzed in detail. Results show that an increase in etching duration promotes the formation of cauliflower pits and enhances the hardness of plasma-induced layer on PEEK, which are facilitated by high-energy plasma bombardment. When the etching time comes to 20 min, these features endow PEEK/DLC with good interfacial adhesion and mechanical properties. Besides, the cauliflower pits could fill debris and help to form graphitized transfer films. The friction coefficient and wear rate of PEEK/DLC both exhibit a declining trend as the etching duration prolongs. Notably, compared to virgin PEEK, the tribological performance of PEEK/DLC with 20-min etching displays lower friction coefficient of 0.2 and lower wear rate of 1.22 × 10−8 mm3/N·m. Finally, a wear failure mechanism for PEEK/DLC with 20-min etching was proposed. This provides a simple and effective approach to improve the tribological behavior of carbon-based films applied on PEEK, it also assists in the development of efficiently wear-resistant materials for aerospace.

Chemometric Raman Spectral Analysis of Diamond-like Carbon Films Deposited by Plasma Discharge

Chemometric Raman Spectral Analysis of Diamond-like Carbon Films Deposited by Plasma Discharge

Revealing the low-temperature friction behavior and mechanisms of hydrogenated amorphous carbon films with Al/Cr/Si doping

Hydrogenated amorphous carbon (a-C:H) film has emerged as a significant contender for solid lubrication applications in low-temperature environments. Here, a set of a-C:H films doped with varying contents of elements (Al, Cr, Si) (AlCrSi/a-C:H) were fabricated, and their low-temperature frictional evolution pattern and mechanisms were explored. The results revealed that the films maintained a superlubricity state as the temperature decreased to − 40 °C, and when the temperature further decreased, the coefficient of friction increased followed by a significant fluctuation. It was related to the competition between shear graphitization, abrasive wear, transfer film formation, and film embrittlement in different low temperature ranges. This work provides new evidence for understanding the carbon film low-temperature friction behavior.

270 MHz passively mode-locked Er-doped fiber laser using single walled carbon nanotube polymer film.

We demonstrated a short-cavity mode-locked erbium-doped fiber laser based on single walled carbon nanotube polymer composite film saturable absorber with a maximum fundamental repetition rate of 270.5 MHz. To the best of our knowledge, this is the highest fundamental repetition rate among mode-locked erbium-doped ring fiber lasers based on nanomaterial polymer composite films. Samples with non-saturable loss range from 13.2% to 60% and modulation depth from 1.63% to 7.08% are prepared by controlling carbon nanotube concentration and film thickness. We systematically investigate the impacts of saturable absorbers on mode-locking repetition rate. Our results show that when the laser repetition rate continuously increases from 15.45 MHz to 270.5 MHz, samples with higher non-saturable loss will push forward the mode-locking threshold and eventually lose mode-locking. In addition, the increased modulation depth will enhance the pulse shaping ability and result in a shorter pulse. Our results may help for high repetition rate mode-locked fiber laser design and improve the laser characteristics. The demonstrated laser may support applications such as frequency comb, etc.

Challenges in Chemical Vapour Deposition of Graphene on Metallurgical Alloys Exemplified for NiTi Shape Memory Alloys

Atomically-thin two-dimensional (2D) materials like graphene have been suggested as ultimately thin corrosion barriers and functional coatings for modern metallurgical alloys. The challenges of chemical vapour deposition (CVD) of such 2D materials, particularly graphene, on modern metallurgical alloys are discussed and reviewed here, focusing on the key problems with the metallurgical alloys’ often limited catalytic activity towards 2D materials growth and the key need to preserve the metallurgical alloys’ bulk properties during the high temperature 2D materials CVD processes. Using graphene CVD on NiTi (Nitinol) shape memory alloys as a case study, we illustrate the constraints arising from low catalytic activity and tendency to form oxides due the Ti in the NiTi alloy in terms of graphene growth results. We show that, by using a scalable low-temperature CVD process at 650 to 750 °C, we can deposit fully covering carbon films on the NiTi, albeit at limited structural quality. Notably, we also demonstrate that our CVD process does not degrade the bulk microstructure of the NiTi during carbon deposition and, importantly, leaves the crystallographic shape memory effect evolution intact. This underscores the potential of CVD for depositing graphene films on NiTi alloys while emphasizing the necessity for further exploration of CVD conditions to achieve high-quality graphene deposits akin to those on prior widely investigated dedicated (often sacrificial) high-purity metal substrates such as Ni.

Hydrothermal synthesize of bi-functional interface structure modified LiMnPO4@LiFePO4/C nanorods as cathode materials for lithium-ion batteries

Olivine-structured LiMnPO4-based cathodes have generated enormous development prospects due to their high energy density, good structural stability, and low cost. However, their scale of application is limited by high electronic and ionic insulativity. In this study, we designed and synthesized a bi-functional interfacial modified composite, 0.9LiMnPO4@0.1LiFePO4/C (0.9LMP@0.1LFP/C), using mechanochemical activation-assisted hydrothermal technology. The innovative Li-storage structure consists of a high-energy density LiMnPO4 (LMP) core, a uniformly coated LiFePO4 (LFP) layer with improved ionic conductivity as the secondary outer shell, and an in-situ coated carbon film with high conductivity as the outermost functional skin. As anticipated, the 0.9LMP@0.1LFP/C composite exhibits outstanding Li-storage properties, demonstrating discharge capacities as high as 157.1 mAh g−1 and 146.7 mAh g−1 at 0.1 C and 1 C rates, respectively. Moreover, it exhibits an ultrahigh capacity retention of 92.5 % after 500 charge and discharge cycles.

Quantification of the sp3 content in Diamond-Like carbon Films: Effects of Ne plasma addition in Deep Oscillation Magnetron sputtering

Diamond-like carbon (DLC) films are a class of amorphous carbon materials with unique properties, including high hardness and wear resistance, making them attractive for aerospace and automotive applications. Recently, High Power Impulse Magnetron Sputtering (HiPIMS) has emerged as a new route for magnetron-sputtered hard DLC films. The authors have previously demonstrated that adding Ne to the plasma significantly improves the properties of DLC films deposited by Deep Oscillation Magnetron Sputtering (DOMS), a HiPIMS variant. In this study, the sp3 content evolution with DLC film thickness was measured by Electron Energy Loss Spectroscopy (EELS) and Near Edge X-ray Absorption Spectroscopy (NEXAFS). The sp3 content in the top section of the film deposited in Ar + Ne plasma is close to 40 % and remains constant across the film thickness. Conversely, in films deposited in pure Ar plasma, the sp3 content decreases from approximately 30 % to 18 % towards the surface. Ne addition increases the sp3 content by enhancing the carbon ion flux and counteracting the atomic shadowing effect. These findings provide novel insights into the role of Ne in reducing the atomic shadowing effect and improving the overall quality of DLC films, paving the way for their optimized industrial use.

PECVD technology deposition of high hardness a-C:H films on micro-drill surfaces: Substrate bias voltage effects

The plasma enhanced chemical vapor deposition (PECVD) technique was utilized to produce hydrogenated amorphous carbon (a-C:H) films. The overall structure of the films consists of a Cr/WC transition layer, a WC/a-C:H transition layer, and an a-C:H functional layer. The study investigated the effects of substrate bias voltages (SBVs) of −580 V, −660 V, −740 V, −820 V, and −900 V on the microstructure, mechanical, and tribological properties of a-C:H films. The findings indicate that different SBVs influence the ionic energy during the deposition of a-C:H films, consequently affecting the film growth. In this case, when the SBV is -820 V, C+ with sufficient energy will penetrate beneath the initial layer in the form of shallow injection. Therefore, compared to other experimental groups, the a-C:H films prepared under this condition have the lowest Ra value (0.42 nm), the highest sp3 CC bond content (39.88 %), the maximum hardness (31.6 GPa), the lowest friction coefficient (0.052), and the smallest wear rate (7.48 × 10−8 mm3/(N·m)), demonstrating significantly better mechanical and tribological properties. The a-C:H films, prepared at different SBVs, are deposited on micro-drill surfaces for hole drilling tests. The experimental results indicate that a-C:H films prepared at SBV of −820 V exhibit the satisfactory drilling performance due to the better mechanical and tribological properties. This is evident not only in the minimal surface wear of the film micro-drill after different drilling quantities but also by the satisfactory quality of the corresponding machined holes. The a-C:H film micro-drill prepared at SBV of −820 V exhibited larger process capability index (CPK) values for the machined holes at 500, 1000, and 2000 hole numbers of 5.449, 3.693, and 3.263 respectively. During the 2000th drill on the printed circuit board (PCB) surface, the hole wall roughness (Rz) and nail head values of the machined hole were measured to be 10.6 μm and 1.3, respectively.

Regulating the structure and performance of amorphous carbon-based films by introducing different interlayers for applications in PEMFC bipolar plates

In this work, the effects of inserting an interlayer on the anti-corrosion performance of amorphous carbon (a-C) films in a simulated Proton Exchange Membrane Fuel Cell (PEMFC) environment have been systematically studied. Four a-C films with different interlayers, namely CCr, C-Cr-N, CrN and Cr, were prepared on 316L stainless steel substrates using unbalanced magnetron sputtering. The surface/fractural morphologies, carbon bonding structure and the anti-corrosion performance of the 4 films were observed/characterized in detail. The nanostructure and composition evolution from the film surface down to the film-substrate interface before and after electrochemical tests were also analysed via high resolution transmission electron microscopy (HRTEM). Results indicate that a-C films with CCr and C-Cr-N interlayers display superior corrosion resistance compared to undoped samples and those lacking an interlayer, with the lowest self-corrosion current density (i.e. 2.1 × 10−7 A/cm2, C-Cr-N interlayer) being nearly two orders of magnitude lower than that of the substrate (i.e. 1.1 × 10−5 A/cm2). The doped C-Cr-N interlayer plays a vital role in the corrosion resistance of the samples by accelerating oxidation of surface defect locations, inhibiting the continuous penetration of electrolyte, and improving corrosion resistance. Additionally, a-C films with a C-Cr-N interlayer exhibited an outstanding interface contact resistance (ICR) value (~3.5 mΩ/cm2) than that with a CrN interlayer (~30 mΩ/cm2) or the 316L substrate (~100 mΩ/cm2) at a typical contact pressure of 1.5 MPa. All 4 films demonstrate obviously improved hydrophobicity (contact angles against distilled water under room temperature up to 94.2°) compared to the substrate (75.8° under identical condition). In a word, this study proves that the strategy of inserting an appropriately designed interlayer (with the ternary C-Cr-N being most promising) to a-C films could alter and enhance the anti-corrosion, ICR and hydrophobic properties of 316L, proposing valuable solutions for high-performance bipolar plates (BPs) in the PEMFC industry.

Processing and analysis of friction vibration signal of diamond-like carbon film microtextured dry gas seal rings

PurposeThis paper aims to analyze the characteristics of friction vibration signals and identify the vibration excitation source at the start and stop stage of microtextured end face of dry gas seals.Design/methodology/approachThe friction pair consists of a diamond-like carbon (DLC) film microtextured seal ring and a spiral groove seal ring. Friction vibration signal feature extraction method based on harmonic wavelet packet and spectrum analysis was proposed. Signals were collected using acceleration sensor, acquisition card and LabVIEW software. Vibration acceleration signal was decomposed into 32 frequency bands using MATLAB wavelet packet transformation. The 32nd band coefficient was extracted for reconstruction, time-domain and spectral waveforms were obtained and spectra before/after denoising were compared.FindingsThe end face of the DLC film microtextured seal ring generates a good dynamic pressure effect, and the friction and vibration reduction effects are obvious. The harmonic wavelet packet can decompose the vibration signal conveniently and precisely. In the case of this experiment, the frequency of vibration of the seal ring is 7500 HZ.Originality/valueThe results show that the method is effective for the processing of friction vibration signal and the identification of vibration excitation source. The findings will provide ideas for the frictional vibration signal processing and basis for further research in the field of tribology of dry gas seal ring.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2024-0084/

Synthesis, characterization, and application of PVDF-PZT composite thin film separator for self-charging supercapacitors

This work utilizes a simple ball milling and heating process to synthesize lead zirconium titanate (PZT). The thin film PVDF-PZT separator is fabricated with the use of dimethyl sulfoxide (DMSO) solvent. The separator's characterization is accomplished by using conventional characterization tools to examine its crystallinity, morphology, chemical composition, and other parameters. According to X-ray diffraction (XRD), Energy dispersive spectroscopy (EDS), and Elemental mapping, the separator is extremely pure and free of any impurities. The separator's surface is found to be uniform with minimal porosity. An analysis of the application of the fabricated thin film separator in a supercapacitor is conducted by placing it in between the previously prepared carbon and NiO thin film electrodes. Upon bending, twisting, and applying force, the device displayed output voltage. Twisting results in a maximum output potential of 140 mV, which is higher than some previously reported works. The results show that the PVDF-PZT thin film separator could potentially be utilized in self-charging supercapacitor applications.

Colossal conductivity anisotropy in 3D metallic carbon films

Harnessing the phenomena of quantum coherence and destructive interference, we have successfully engineered and synthesized a three-dimensional (3D) graphene-based film exhibiting remarkable properties, including metallic thermal conductivity (κ ≈ 150 Wm⁻1K⁻1) and electrical conductivity (σ ≈ 320 kSm⁻1) at room temperature. Notably, these films demonstrate colossal transport anisotropies, reaching approximately 103 for thermal and 105 for electrical conductivity. This places them among the conducting materials with the highest anisotropies known to date, surpassing even the performance of one-dimensional (1D) carbon nanotubes and two-dimensional (2D) materials like h-BN and MoS₂. These films are synthesized by self-assembly and cross-linking of edge-hydrolyzed graphene flakes. The electron transport between flakes is phonon mediated and at low temperatures the films present quantum critical behavior of a metal to Anderson insulator transition. We measure the electron transport properties in a Hall bar geometry and extract the critical exponents as a function of the sample mobility.

MgNiO2 as a Ceramic Additive To Improve the Durability of Lithium Metal Anode.

Ceramic materials are the most popular additives to regulate the reinless interfacial reaction between lithium and the electrolyte by strengthening the SEI layer or tuning lithium deposition. Here, we propose an exceptional material, MgNiO2, abbreviated as MN, which can improve the durability of lithium metal anode. Since it is undecomposed up to 0 V vs Li/Li+, the MN's particles give some semiconductive characteristics to the SEI layer to tune the interfacial reactions. The addition of MgNiO2 in the protective films lowers interfacial resistance, which is responsible for the improved durability of Li|Cu cells: ∼210 cycles, which is 4 times longer than that of the control. Furthermore, this ceramic is used to modify the carbon film woven with carbon nanofibers (CNF @ MN). The cells with this modified 3-D host present excellent operational lives, as high as ∼2400 h in Li|Li symmetric cells and ∼280 cycles in the Li|NCM811 cells. Our approaches demonstrate that MN is an effective ceramic for stabilizing the lithium anode. It also indicates that the inert nature of the semiconductor to lithium is worth exploring thoroughly.

An ultrafast rechargeable hybrid potassium dual-ion capacitor based on carbon quantum dot@ultrathin carbon film cathode

An ultrafast rechargeable hybrid potassium dual-ion capacitor based on carbon quantum dot@ultrathin carbon film cathode