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Graphene (G), as a typical two-dimensional material, is often used as an additive for liquid lubricants. However, graphene is mostly added to liquid lubricants in a one-time manner in friction; it mainly exists in the form of multilayer agglomerated structures due to the π−π stacking between graphene sheets, making it unable to fully exert the synergistic lubrication function. Herein, we propose a new macroscopic superlubric system of graphene/potassium hydroxide (G/KOH) solution; and the graphene additive involved is exfoliated in-situ from graphene/epoxy (G/EP) friction pair by friction, continuously providing freshly-peeled graphene into KOH solution and minimizing the adverse effects of graphene agglomeration. Moreover, the in-situ produced graphene additive has thinner thickness and better anti-aggregation ability, which provide more graphene to accommodate OH−, form more stacked sandwich structures of OH−/graphene/OH− between friction pairs (i.e., equivalent to a moving pulley block with more wheels), and finally realize superlubricity. This study develops a new liquid superlubric system suitable for alkaline environments, and at the same time proposes a new way to gradually release graphene additives in situ, rather than adding them all at once, deepening the understanding to liquid superlubricity mechanism, and paving the experimental foundation for the practical application of macroscopic superlubricity.

Though amorphous carbon films are kinds of most distinguished lubricant materials, the friction coefficients of commercial amorphous carbon films are in the range of 0.05–0.40. To reduce the friction coefficients of those amorphous carbon films from the order of 0.01 to 0.001 range is still a big challenge. In order to solve the problem, in present work, a new strategy, called catalytic superlubricity, is proposed and carried out to achieve superlubricity by in-situ formation of graphene via introducing gold onto hydrogenated amorphous carbon (Au@a-C:H) film during friction. The results show that mulilayer graphene along with oriented polyolefin-like structures are formed due to the catalysis of Au nanoparticles, which is embedded in amorphous carbon matrix. Furthermore, the density functional theory calculations indicates that interlayer binding energy between graphene and the hydrogenated amorphous carbon (a-C:H) films’ surface is comparable to that between graphene layers, resulting in low interfacial interactions between sliding interfaces for low friction. Then, the low interfacial interactions lead to superlubricity with a friction coefficient of 0.003. This study opens up a new routing for facile and scale up fabrication of superlubricant a-C:H films in industrial applications.

Diamond-like carbon (DLC) films directly deposited on rubber substrate is undoubtedly one optimal option to improve the tribological properties due to its ultralow friction, high-hardness as well as good chemical compatibility with rubber. Investigating the relationship between film structure and tribological performance is vital for protecting rubber. In this study it was demonstrated that the etching effect induced by hydrogen incorporation played positive roles in reducing surface roughness of DLC films. In addition, the water contact angle (CA) of DLC-coated nitrile butadiene rubber (NBR) was sensitive to the surface energy and sp2 carbon clustering of DLC films. Most importantly, the optimum tribological performance was obtained at the 29 at% H-containing DLC film coated on NBR, which mainly depended on the following key factors: (1) the DLC film with appropriate roughness matched the counterpart surface; (2) the contact area and surface energy controlled interface adhesive force; (3) the microstructure of DLC films impacted load-bearing capacity; and (4) the generation of graphitic phase acted as a solid lubricant. This understanding may draw inspiration for the fabrication of DLC films on rubber to achieve low friction coefficient.

Material and energy losses caused by friction and wear hinder the development of mechanical systems. An effective way to solve the problem is to reduce friction coefficient and wear. Here, we proposed in-situ formation of graphene nanoribbons via gold-catalyzed reconstruction of amorphous hydrogenated carbon matrix to achieve engineering superlubricity. And we called this method “catalytic superlubricity”. In detail, amorphous hydrogenated carbon (a-C:H) films were grown by plasma chemical vapor deposition (PECVD), and gold (Au) films on steel balls were obtained by electroless chemical deposition. Comparing study on the tribology properties of the couple pairs of a-C:H/Au and a-C:H/GCr15 was carried out via home-made Tribometer 3. The results show that, compared with the couple pairs of a-C:H/GCr15 ( μ ~0.032 and wear depth of 128 nm ), the couple pairs of a-C:H/Au show a friction coefficient of 0.008 and wear depth of 40 nm, respectively. The reason of superlubricity of the couple pairs of a-C:H/Au is that, based on the catalysis of gold, the graphene nanoribbons formed in-situ during friction. The ordered structure is conducive to the occurrence of incommensurate contact, and effectively reduces the interfacial shear force and thus lowers the friction coefficient.

Diamond-like carbon (DLC) films embedded with crystalline graphite and multilayer graphene have been fabricated on silicon substrates by a simple electrochemical route from methanol and C60-1, 2-ethylenediamine (C2H8N2) derivatives as an incorporating reagent at atmospheric pressure. The structure and sheet resistivity of the as-obtained films were characterized by x-ray photoelectron spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, and four-point probe measurements, respectively. The structure of the as-prepared films with crystalline graphite and multilayer graphene consisted of sp2 C, sp3 C, C–N, C–H, and N–H bonds. After introducing crystalline graphite and multilayer graphene, the conductivity of the DLC films was evidently improved and the sheet resistivity drastically decreased from 108 Ω cm to about 80 Ω cm.

Fullerene-like hydrogenated carbon (FL-C:H) films hold superlubricity properties at room condition, which important for saving energy, for engine use, however, high temperature serving (below 500 °C) are needed considering. In this paper, FL-C:H films were annealed with protecting of nitrogen. The tribological test show that all films have superlubricity properties, of which friction coefficient are 0.008 (200 °C), 0.005 (250 °C), 0.004 (300 °C), 0.005 (400 °C), 0.004 (500 °C), respectively. In addition, the hardness is incremental when the annealed temperature increased from 200 to 300 °C, and decremental from 300 °C to 500 °C. Interestingly, the changes of hydrogen content can be neglect in present work. Combined HRTEM, Raman spectra and XPS results, one can speculate that the degree of order for FL-C:H films increase along with the argument of annealed temperature, but competition of growth and ordering of short-chain hydrocarbon and graphene stacks that determine the hardness and H3/E2 ratio, which further influences the wear volumes. However, the friction coefficient only depends on curved grahene which can formation scroll graphene between contact surface to low friction force.

The introduction of curved graphite fragments into hydrogenated amorphous carbon films has been studied, and their contents are always estimated by TEM and Raman. Here, we detailedly discussed the advantage and disadvantage of TEM and Raman fit method. Combined with FTIR results, we claified the chemical structures of the structural films and the bonded sites of doped H. The curved graphite structures included hexahydric carbon rings, and amorphous carbon (a-C) structures had rich olefinic groups and H. Finally, the differences among TEM, Raman, FTIR and H analysis in terms of the contents of curved graphite fragments were discussed.

Recycling carbon dioxide (CO2) for weakening the greenhouse effect is still an outstanding question. Although many chemical methods have been designed for CO2 conversion, they is still a need to develop new ways for CO2 recycling. Plasma methods were employed to convert CO2 into energy molecules, with the addition of H2, H2O and so on. Non heavy elements, like Ti, Cr, Si and Mo and so forth, were employed to take part in a reactive process, which might be very interesting for special scientific interest. In this work, magnetron sputtering method was used not only for igniting the plasma but also for providing Ti elements involved in reactions, via the selected Ti target. One can confirm that the TiCxOy films were successfully grew via sputtering a Ti target in CO2 atmosphere with Ar as dilute gas, which proved that CO2 is a key player in the matter of the involvement of excited CO2+, CO+, CO3&minus, and so on, in the growth process reacting with Ti ions. The TiCxOy films exhibit the highest hardness (20.3 GPa), lowest friction coefficient (0.065) and the best corrosion resistance. The growth of the TiCxOy films are not only a new strategy for consuming CO2 but also a good way for reusing it for preparing TiCxOy films with high hardness for anti-corrosion and reducing friction. Moreover, reducing CO2 emissions via energy saving (through reducing friction and corrosion resistance) and recycling existing CO2 are both important for mitigating the greenhouse effect.

Superlubricity from two dimensional (2D) materials has aroused increasing interest in recent years; however, it can only be achieved below millinewton loads under ambient condition. How to obtain high load-bearing and ambient robust superlubricity remains a challenge but is highly desirable. Here, we use the deformation of highly elastic fullerene-like hydrogenated carbon (FL-C:H) substrate on a large area, to disperse high contact pressure applied on graphene/MoS2 heterojunctions and avoid structure destruction caused by stress concentration. The contact pressure diffusion ensures the structural integrity of 2D materials and promotes their heterointerfacial contact, resulting in high load-bearing superlubricity. Moreover, the maintenance of structural integrity, combined with the preparation of graphene with few defects by using a vacuum ball-shearing exfoliated graphene (BSEG) technique, remarkably weakens environmental chemical interaction to reach ambient robust superlubricity. The BSEG/MoS2/FL-C:H system achieves macroscale superlubricity under vacuum (0.009) and ambient conditions (0.007 at 20% RH, 0.009 at 40% RH) and at engineering load of 15 N. The applied load is far higher than 35 mN that is the known largest values. Atomistic simulations reveal the overall link between contact stress dispersion and experimental observations. This work reveals a novel principle of achieving high load-bearing and ambient robust superlubricity based on contact stress dispersion, and helps to bridge structural superlubricity to practical applications, potentially dramatically reducing energy dissipation.

The emergence and development of macroscale superlubricity for carbon films are an application-oriented process, which is expected to greatly help to solve the increasing energy and environmental problems in the 21st century.The recent scientific results in the structure-bestowed superlubricity for carbon films (such as fullerene-like, graphite-like and nanodiamond etc.) have been presented here, and the common superlubricity mechanism behind such carbon nano-structural films has been analyzed and summarized. The problems of realizing a stable superlubricity behavior and the future development direction of carbon films’ superlubricity are also discussed.

Driven by the advent of fullerenes, carbon nanotubes and graphene, designing or tailoring sp2-rich carbon clusters in carbon based films attains very interesting properties which can be ideal in various applications. Depositing sp2-rich clusters evolve toward a three-dimensional arrangement (composed of extended, bent, and cross-linked graphite basal planes, i.e. fullerene-like carbon (FLC)) or nanocrystalline planar graphitic configurations with the promotion in size and ordering of six-membered ring clusters (i.e. graphite-like carbon (GLC)). However, the films are studied separately and their structure effects on sliding-induced structure changes has never enjoyed elaboration. Here we built the self-mated friction groups of single structural films coated at two sliding surfaces, and designed a smart device to gather the transformed products under different load and sliding cycles. Super-low friction was realized under higher load by low-shear strength from graphene formed at the GLC interface (0.005), or reduced contact area from spherical nanoparticles with outer graphite shells produced at the FLC interface (0.009), resulting by different rehybridization pathways from different film structures. The role of film and rehybridized structures under super-low friction contact was discussed. The results could enrich the understanding of friction-induced rehybridization mechanism and help to deposit suitable films to significantly reduce friction.

Onion-like carbon films were prepared by constant current high-frequency dual-pulsed plasma enhanced chemical vapor deposition technique. Owing to the unique carbon onions both in bulk and debris of nanostructured carbon matrix, the films not only showed a super-high elastic recovery up to 92%, but also obtained a super-low friction coefficient below 0.01 and wear rate about 6.41 × 10−18 m3/Nm in ambient atmosphere. The carbon onions achieved an incommensurate contact and played as “molecular bearing” in the friction process, resulting in both super-low friction and wear rate.

Fullerene-like hydrogenated carbon films deposited by plasma enhanced chemical vapor deposition (PECVD) as compared with other methods can attain super-low friction and wear. But they often have bad adhesion to steel substrate and their structures are tailored by non-metal elements as F, N etc. In this work, we have prepared the films on steel balls by the combination of PECVD and plasma nitriding, among which iron nitride particles are sputtered and introduced in the films. The films have longer wear life and better adhesion to the steel substrate due to the N diffusion from iron nitride particles to the atom matrix of the ball.

In this study, we carried out the transition experiments of graphite-like (GL) to fullerene-like (FL) structures by placing high temperature steel substrates in the depositing environment which can form FL hydrogenated carbon films. We investigated the changes of bond mixtures, H content, aromatic clusters and internal stress at the transition process, and proposed the transformation mechanism inferred from Raman, TEM cross-section, FTIR and XPS results. It was found that the size of aromatic clusters and accordingly graphene planes and the formation of edge dangling bonds were the key steps. H+ bombardment leaded to the splitting of large graphene planes (at GL stage) into more and smaller planes (at FL stage) and the formation of edge dangling bonds; Some of these dangling bonds were reduced by the formation of pentagons and subsequent curving of the smaller planes, which were an indicator of FL structures.

Although nickel has a lower standard electrode potential than copper, nickel-sulfur coatings were successfully deposited on copper through one-step immersion plating method, which was carried out in the aqueous solution consisting of NiSO4·6H2O and Na2S2O3·5H2O at room temperature. The open circuit potential tests demonstrated that copper had a more negative potential than nickel in Na2S2O3·5H2O solutions, which made the deposition of nickel on copper through immersion plating feasible. Because of the decomposition of sodium thiosulfate, sulfur could be codeposited with nickel and the nickel-sulfur coatings were finally obtained. The surface morphology and composition of the coatings were characterized with SEM, EDS, XPS and XRD analyses, and the results indicated the coatings were mainly composed of metallic nickel and Ni3S2. The deposition process of the nickel-sulfur coatings was investigated by analyzing the morphology evolution of copper substrates. The as-prepared nickel-sulfur coatings possessed good anticorrosion ability for its compact structure and could lower the corrosion current density of copper in 3.5 wt% NaCl solution to its 1/20.

Fullerene-like hydrogenated carbon films have outstanding mechanical and frictional properties, but their structures have never enjoyed elaboration. In this study, we investigate the relation between nano-hardness and elasticity and fullerene-like clusters by changing energy supply form (direct current and pulse) and H2 concentration in the feedstock. It is found that the films have a network of H-rich amorphous carbon and H-poor or -deficient fullerene-like carbon, and the network change can affect hardness and elastic recovery. This is due to the energy minimization process of the film growing system in a very short pulse period at low temperature.

Epoxy resin (EP) as a friction material suffers from serious friction and wear in high temperatures. Adding various carbon fillers into EP to form carbon/EP composites is one of the solutions to this concern. However, the correlation between the filler's dimensionality and their friction properties under high temperature conditions is missing. Herein we construct a comparable dimensional model system of carbon fillers (i.e., one- to three-dimensional carbon nanocage assemblies) to reveal the dimensional effect in high temperature lubrication. Compared with EP, a merely 0.10 wt% of one-dimensional filler can reduce the composite's friction coefficient and wear rate by 36% and 95% at 30 °C, respectively; while for those filled with other dimensionalities, the corresponding decreases are less than 24% and 60%. Even at very close to EP's glass transition temperature of 150 °C, it still maintains a low friction coefficient only with a slight increase in wear. The enhanced high temperature lubrication performance is first attributed to the advantage of one-dimensional fillers to suppress the EP matrix's creep and then easily sliding in the softened transfer film. This study provides a new view for the design of carbon fillers used in EP-based high temperature lubrication composites.

For the purpose of extensive application of superlubritic solid films material, the steel substrate as the most widely used engineering material should be taken into consideration instead of lab-used Si substrates. In present work, the bilayer a-C:H/MoS2 film was grown on a 9Cr18Mo steel substrate with a Ti/TiN/TiCN transition layer to assure strong interfacial adhesion. A steady state of superlubricity (friction coefficient ~ 0.008) was obtained under high normal loads (beyond 15 N) in open atmosphere not only on Si substrate but also on 9Cr18Mo steel substrate, though the roughness of which is 10 times higher than that of the Si substrates. Compared to the naked 9Cr18Mo steel, the introduction of the a-C:H/MoS2 film can reduce the friction coefficient and wear rate to nearly 1/50 and 1/6, respectively. Detailed experimental studies reveal that realization of ultralow friction is attributed to low contacting stress (5 N and 11 N) induced structure of oriented molybdenum disulfide in wear debris. Further, amorphous molybdenum disulfide accelerates the formation of oriented graphene ribbon under high contacting stress (15 N and 20 N) at the contact interfaces helping to achieve superlubricity. Thus, our work here provides a strategy for design an industrial scale superlubricity friction system.

In this study, tribological properties of hydrogenated and hydrogen free diamond-like carbon films at various relative humidity (RH) were investigated to understand the friction mechanism in the presence of water molecules. At normal load of 2N, DLC-H film’s friction coefficient was 0.06 at RH14% while DLC film’s friction coefficient was 0.19 at RH17%. With the increase of RH, their friction coefficient converged to about 0.15. This character remained unaltered when the normal load was 5N. Results show that low friction of DLC-H film at low RH was attributed to the low shear force aroused by graphitic tribofilm at wear care center. However, the high friction of DLC film was mainly endowed by the high adhesive force aroused by σ dangling bonds. At high RH, solid-to-solid contact was isolated by water molecules confined between the counterfaces, where capillary was a dominant factor for friction. In addition to the capillary force, the absence of tribofilm was also accountable. These two factors lead to the level off of friction coefficient for DLC-H and DLC films. Moreover, for both DLC-H and DLC films, tribo-oxidization was proved to be closely related to wear rate with the assist of H 2 O molecules during sliding.

In this study, we prepared hydrogenated amorphous carbon films on steel balls and Si substrates (steel ball- and Si substrate-films) with different deposition time, and discussed their carbon nanostructural evolutions and tribological behaviors. The steel ball-film structure started to be graphite-like structure and then gradually transformed into fullerene-like (FL) structure. The Si substrate-film structure began in FL structure and kept it through the thickness. The difference may be result from the competition between high starting substrate temperature after additional nitriding applied on the steel balls (its supply power is higher than that in the film deposition), and relaxation of compressive stress from energized ion bombardment in film deposition process. The FL structural film friction couples could achieve ultra-low friction in open air. In particular, the Si substrate-film with 3 h, against the steel ball-film with 2 h and 3 h, exhibited super-low friction (∼0.009) and superlong wear life (∼5.5 × 10 5 cycles). Our result could widen the superlubricity scope from previously high load and velocity, to middle load and velocity.

Carbon quantum dots (CQDs) and ionic liquid (IL) nanoparticles were fabricated by simple modification. The structures and properties of these particles were measured with HRTEM, FTIR, Raman Spectrometer and friction test. More importantly, IL-modified CQDs as lubricant material demonstrated excellent tribological performance and obtained a super-low friction coefficient about 0.006 and wear rate about 0.7 × 10 −14 m 3 /Nm with the CQDs content of 3.6%. The results revealed that IL-modified CQDs might provide a new idea to investigate various lubricant materials to achieve super-low friction and could be intensively studied for other practical applications.

Graphene has been regarded as a promising candidate in microwave absorption field but still faces some major challenges, including the limitation of mass production and poor impedance matching. Here, we demonstrate a simple approach to fabricate multilayer graphene in a kilo-mass/hour (≥2.5 kg/h) scale through an oxidation-thermal expansion-air convection shearing process. The subsequent incorporation of hexagonal boron nitride nanoparticles (h-BNNPs) can effectively tailor the dielectric and magnetic properties of the as-obtained multilayer graphene, which can significantly boost its microwave absorption performance. The as-obtained multilayer graphene/h-BNNP hybrid with 40 wt.% of h-BNNPs, exhibits extremely low reflection loss value of −67.35 dB at 8.04 GHz when the absorber thickness is 3.29 mm, ranking it as one of the most attractive absorbers reported to date. Moreover, the multilayer graphene/h-BNNP hybrids possess low densities less than 0.45 g/cm3, making them very attractive for practical microwave absorption application.

Hexagonal boron nitride nanosheets (h-BNNSs), with a crystal lattice structure similar to graphene by over 98%, exhibit good lubrication properties as lubricant additives. However, the poor dispersibility in solvents has limited their wide practical applications as lubricant additives. In the present report, water dispersible Pebax functionalized h-BNNSs (Pebax-BNNSs) have been prepared through a one-step solvent-free mechanical exfoliation process which relies on a simple exfoliation of h-BN layers by shearing force in molten Pebax at 200 °C. In this process, Pebax molecules can synchronously react with the dangling bonds formed during the exfoliation process to achieve in situ functionalization of h-BNNSs. The reciprocating friction tests demonstrate that the as-obtained Pebax-BNNSs possess excellent antifriction and antiwear performance as water-based lubricant additive with a low concentration of 0.3 mg/mL under atmospheric condition. The friction coefficients can be h-BNNSs can achieve superlubrication as water-based lubricant additives via facile surface modification, making them very promising candidates as lubricant additives in practical applications.

Fullerene-like hydrogen carbon films with a thin film grown on a NaCl substrate are usually employed to show the nanostructure of films (usually of hundred nanometers thick grown on Si substrates) under high resolution transmission electron microscopy (HRTEM) tests because it is easier floated off, where dependability and reasonability has never been seriously contested. Thus, in this paper, thin and thick hydrogen carbon films have been deposited on NaCl (thin films) and Si (thick films) substrates and annealed under room temperature to 500 &deg, C, of which nanostructures have been investigated by HRTEM, Raman spectroscopy, and X-ray photoelectron spectroscopy, to verify the dependability and reasonability of the NaCl method. The results showed heating induced graphitization but with hydrogen content nearly unchanged. HRTEM results revealed that under annealing of 200, 250, and 300 &deg, C, the curved graphene structures gradually increase in films. However, beyond 400 &deg, C, onions structures are present. However, both Raman and XPS spectra show us that after annealed treatment, for original films, both thin and thick films have the near sp2 bonding content and size, but with the annealing temperature increase, sp2 bonding content increases more quickly for thick FL-C:H films due to the higher internal stress compared to thin films. In one word, the NaCl method used for nanostructure detection for films might be a good choice for an easier and quicker analysis, but it is still insufficient, because the heating effect induced by plasma cannot be ignored.

Epoxy resin (EP) nanocomposite materials with excellent tribological properties are highly desired for many engineering applications requiring low friction and wear. Adding carbon nanofiller is regarded as one of the most potential solutions to solve the serious dry wear problem of epoxy matrix. Herein, we report a new filler of carbon nanocages (CNC) prepared by the method of MgO templates to improve its dry friction performance through filling epoxy into the internal hollow space of CNC. Relative to neat epoxy, the friction coefficient (0.249) and wear rate (7.98 × 10−7 mm3 Nm−1) are reduced by 55.6% and 51.9% for the optimized CNC/EP nanocomposites, respectively. Even compared to typical graphene/epoxy nanocomposites, the wear rate is also reduced by up to 21.8%, as well as greatly enhancing the mechanical properties, thereby effectively protecting epoxy matrix and improving its dry friction. Such great tribological performance is attributed to unique structure of CNC, enabling the multi-functional collaboration of physical confinement, self-lubrication and wear-debris collection for CNC fillers, and making it the most potential carbon-based nanofiller for EP-based nanocomposite material system. More than that, it also provides insights for designing other advanced carbon-based nanofillers.

Fullerene-like nanostructural hydrogenated amorphous carbon (FL-C:H) films were prepared by dc- and pulse- plasma enhanced chemical vapor deposition technique (PECVD). Both the films exhibit relatively stresses (0.63 GPa) in spite of their FL features and nanostructural bonding configurations, especially the pentagonal carbon rings. The creation of pentagonal rings is not fully driven by thermodynamics, but is closely related to compressive stress determined by the ion bombardment at the discharged state of the pulse- and dc- discharged plasmas methods. The dc method leads to FL's basal planes which contain less cross-linkages, and causes amorphous strongly hydrogenated structures.

The fullerene-like (FL) nanostructure is extremely important for fullerene-like hydrogenated carbon (FL-C:H) films that exhibit excellent mechanical properties and ultralow friction in ambient air, but the details of the contributing nanostructures are not well understood. We have prepared FL-C:H films with different morphologies and contents of FL nanostructures through tailoring the pulse bias duty cycle, and have investigated the contribution of the FL nanostructures. It is found that the straighter graphitic nanostructures in FL-C:H films could form under a high pulse bias duty cycle, and the low pulse bias duty cycle could increase the five-membered ring fractions, which results in more curved FL nanostructures with a larger curvature radius. Further investigation proved that the FL nanostructures with the more curved morphology could increase the mechanical properties and improve the tribological performance of the FL-C:H films. This work established a convenient controlling method to prepare FL-C:H films with tailored structures and performance.

Although MoS2 film plays an important role in reducing friction, however, it will collapse down at higher loads. To prevent the failure of MoS2 under higher load, in present work, structure bilayer a-C:H/MoS2 films were prepared via PVD/PECVD hybrid method. The component, bonding structure, morphology as well as trichology and mechanical properties of the films were investigated, respectively. The results show that MoS2 film stack uniformly on a-C:H film's surface. Due to the special design of the structure, the bilayer a-C:H/MoS2 film show a sufficient decrease of friction coefficient compared with that of a-C:H film. In addition, the superlubricity state was achieved at very high loads, which can be ascribed to the low shear force and incommensurability contact between adjacent MoS2 layers. And a-C:H film here plays as foundation stone of supporting MoS2 film and enforcing its adhesion on silicon substrates, which inhibits slipping away of MoS2 film under shear force. Our work can open a new mind to help design the high loads capability of MoS2 based films, which can break the deadlock of the bad loading ability and achieve superlubricity at even higher loads for MoS2 based films.

Diamond like carbon (DLC) films are considered as exciting candidates for biomaterials owing to high hardness and chemical inertness. However, the high resistivity of pure DLC films limited further applications in bioelectronic field. The palladium and phosphorus doped DLC film was fabricated by electrochemical deposition from the ethanol solution of Tetrakis (triphenylphosphine) platinum. The structure of the film was composed of C P, C P, C H, sp2–C, sp3–C bonds and Pd nanoparticles. The resistivity was evidently reduced due to the introduction of palladium and phosphorus, and the biocompatibility simultaneously enhanced. It will open up a new application direction for bioelectronic devices.

Both nitrogen and silicon-doped carbon (a-CNx:H and a-CSi:H) films show superlubrcity properties in distinguished sliding conditions, but most running machines are required to serve in humidity air atmosphere. Therefore, we aim to explore N and Si doping effects on tribology of a-C:H films and reveal the basic factors of superlubricity in open atmosphere with a humidity of 41%. In present work, three kinds of films (a-C:H, a-CNx:H and the a-CSi:H films) were prepared on n-Si(100) substrates by plasma-enhanced chemical vapor deposition (PECVD). The thickness, element distribution, bonding topolograph and nanostructure of all films before and after friction test, including wear debris, tracks and debris, were detected by means of XPS, Raman, HRTEM and SEM, etc.. Compared with hydrogenated carbon film (a-C:H), the highest COF (0.089) and wear rate (3.61 × 10−7 mm3/Nm) of a-CNx:H film are attributed to forming Fe3C, Fe2O3 and Cr2O3 on the slide surface due to the chemical reaction with moisture atmosphere, which caused by the emission of N element via the broken C N structure that induced more activity dangling bonds. However, the silicon-doped carbon film (a-CSi:H) exhibited extremely low COF (0.007) and extremely low wear rate (4.76 × 10−8 mm3/Nm), which can be ascribed to the Si which is more reactive with moisture atmosphere, prohibiting the oxidization of carbon matrix and helping to forming more curved graphene structures to low the friction force.

Convenient integration of high-purity graphene film on industrial-sized silicon wafer is highly desired for on-chip electronics such as pulse energy harvesting capacitors. However, current graphene materials usually need costly additional purification procedures to remove metallic impurities before use. Herein, a purification-integration technique is explored for graphene oxide (GO) by using the reverse migrations of metal ions and negatively charged GO sheets in water under electric fields, and corresponding films are successfully deposited on 6-inch anodic silicon wafers in one step. Nearly ~90% of metallic impurities (e.g., Fe, Mn, and Cr) could be removed for the electric-field purified reduced graphene oxide film (EPGF) with the content of Cr as low as ~10 ppm. Owing to the high purity and the robust interface contact to silicon substrates, the EPGF as capacitor electrodes delivered the minimal self-discharging current of ~0.11 μA and the highest working frequency of 18420.7 Hz (i.e., up to 10 kHz-level at −73.5°) for graphene capacitors reported to date, as well as maintaining normal areal capacitance. In contrast to the common strategy by increasing ion rate, this study focuses on the improvement of electron rate by optimizing electronic interface contact, which provides new insights for fabricating kilohertz graphene capacitors.

A gaseous plasma source for materials surface modification has been developed and investigated in detail. The operating pressure range was 6.7 × 10−2 ÷ 2.5 × 10−1 Pa. At discharge current of 10 A and discharge voltage of 100 V the maximum plasma density was up to 3·1010 cm−3 in the volume up to 0.1 m3 in DC mode. The possibility of independent control of the current of injected electrons and their energy, makes it possible to choose the optimal parameters to ensure high energy efficiency of plasma generation (up to 150 eV/ion) according to process requirements and material properties. Using Hughes–Rojansky electrostatic analyzer and moveable Langmuir probe, an electron and ion energy spectra and plasma distribution were measured in the region of substrate location. The source was used for NBR surface modification in the ambient of noble gases, nitrogen, oxygen and acetylene. It has been shown that plasma treatment leads to a decrease in the coefficient of friction of NBR by 2–3 times.

Amorphous carbon films with perfect corrosion resistance have attracted scientific interest for years, but the corrosion behaviors of these films under heat shock conditions have rarely been reported. To reveal these behaviors, the corrosion properties of hydrogenated amorphous carbon (a-C:H) films at temperature of 200–400 °C are evaluated by Electrochemical tests and the variation of its structure detected via Raman spectroscopy, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy and scanning electron microscopy. Under all inspected temperatures, the corrosion properties of the films are better than those of bare silicon due to the chemical inertness of the a-C:H films. In detailed, the corrosion properties improve with increasing temperature up to 250 °C, because of the densification and crystallization of the a-C:H films. Above 250 °C, the corrosion properties weakened a litter as the temperature increased, which can be attributed graphitization induced porosity and promoted the number of ion channels. In a word, the films that annealed at a temperature of 250 °C have optimal corrosion resistance. Interestingly, the surface energy of a-C:H films has little effect on corrosion behaviors. Our result shows that the a-C:H films have superior corrosion resistance even under heat shock conditions.

W/Ti-doped diamond-like carbon (DLC) films were fabricated on Si substrates by co-sputtering W and Ti targets in methane and argon mixture atmosphere. The composition and the microstructure, internal stress, mechanical and tribological properties of the films were measured by X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), Raman spectra, BGS 6341 type film stress tester, nano-indentor and reciprocating ball-on-disc tester, respectively. The results indicated all films showed the amorphous structural characteristics and a constant thickness value of ∼600 nm (195 ± 15 nm Ti interlayer was designed in order to minimize the influence of Ti interlayer), and the Ti content increased from 0 to 34.5% as the W target current increased from 0 A to 14 A. As the W concentration increased from 0 to 2.6 at.%, the hardness increased to 12.7 GPa and the internal stress maintained at a low value and almost no change. Meanwhile, the friction coefficient and wear rate showed the lowest value (0.023 and 1.2 × 10 −8 mm 3 /N m, respectively). With the W content increased to 34.5 at.% further, the internal stress, friction coefficient and wear rate of film are dramatically increased.

Fullerene-like hydrogenated carbon films were deposited on Si substrate by plasma-enhanced chemical vapor deposition. The microstructures of films were characterized by high-resolution transmission electron microscopy and Raman spectrum. The tribological performance of films was tested by reciprocating ball-on-disc tester under 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid. The surface morphology and chemical composition of wear tracks and wear rates were investigated by optical microscope, X-ray photoelectron spectroscopy, and 3D surface profiler. The results indicated that the film with a typical fullerene-like structure embedded into the amorphous sp2 and sp3 carbon networks could be prepared successfully, and the film shows a higher hardness (26.7 GPa) and elastic recovery (89.9%) compared with the amorphous carbon film. Furthermore, the film shows a lower friction coefficient at low contact load and friction frequency, and excellent wear-resistance performance at high load and frequency under ionic liquid lubrication. Meanwhile, the wear life of fullerene-like hydrogenated carbon films could be improved significantly using ionic liquid as a lubrication material. Copyright © 2015 John Wiley & Sons, Ltd.

Fluorine easily substitutes hydrogen in DLC films due to its monovalence and high electronegativity. The peculiarities of fluorine bestow low surface energy, low inner stress, good thermal stability, preeminent tribological properties and biocompatibility on fluorine-containing, diamond-like carbon (F-DLC) films. Although there are some reviews that introduce the important advances in DLC films, they are not particularly focused on the promising F-DLC films. In this review, we mainly concentrate on the mechanical and tribological properties of F-DLC films. The mechanical properties, including hardness, modulus, and inner stress, will be discussed thoroughly. More importantly, the eminent tribological properties of F-DLC films would be emphasized based on the surface passivation and repulsive forces induced by fluorine atoms from the surface chemical and micro-mechanical viewpoints. Finally, some existing challenges and promising breakthroughs about F-DLC films are also proposed. It is expected that these films would be produced on a large scale and applied extensively in industrial applications such as micro-electro-mechanical systems, ultra-large scale integrated circuits, thin film transistor liquid crystal displays and biomedical devices.

Fullerene-like hydrogenated carbon (FL-C:H) films that exhibit ultra-low friction and wear in humid conditions have been the subject of extensive researches, but the structure–performance relationship such as the evolution of FL structures under friction is not well understood. We have prepared FL-C:H films with different FL content, and have addressed a detailed investigation on the relationship. It is found that with the increase in FL content, the friction and wear of FL-C:H films can reach as low as 0.011 and 1.48×10 _ 8 mm 3 /Nm, respectively. Examination of the corresponding wear tracks by Raman spectroscopy reveals that not graphitization but friction-induced promotion of FL structures causes the ultralow friction and wear of FL-C:H films. We therefore claim that FL structures are in close positive relations with the excellent tribological performance of FL-C:H films.