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Although diamond‐like carbon (DLC) films are known for their low friction and wear properties in atmospheric environments, they commonly experience failure in vacuum environments. On the other hand, MoS2 exhibits a low friction coefficient under vacuum conditions, but its columnar structure limits its load‐bearing capacity and results in high wear rates. In this study, we prepared MoS2/DLC multilayer films using a high‐power impulse magnetron sputtering (HIPIMS) technique and examined the composition, bonding structure, mechanical properties, and frictional wear of the resulting films. The study findings revealed that the multilayer film exhibits a significantly low coefficient of friction (0.04), particularly in vacuum conditions (5 × 10−3 Pa). Remarkably, compared to the pure MoS2 film, the wear rate of the multilayer film is reduced by two orders of magnitude, wear rate as low as 3.6 × 10−9 mm3/Nm. Additionally, the DLC component enhances the hardness and reduces the wear rate of the multilayer film. Furthermore, the use of nanometer thickness (17 nm) allows for the incorporation of more MoS2 and DLC layers, which promotes the formation of graphene bands and further reduces the friction coefficient and wear rate. Our findings open new avenues for the application of MoS2 and DLC in vacuum environments. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this study, we prepared a‐C:H films with different nanostructures at different methane flow rates. The effect of the methane flow rate on the tribological properties of 440 steel/a‐C:H friction pairs and a‐C:H:Ti/a‐C:H friction pairs in an atmospheric environment was studied by a reciprocating friction machine. The results show that there is no relationship between the tribological properties of 440 steel/a‐C:H friction pair and methane flow rate. The tribological performance of the a‐C:H:Ti/a‐C:H friction pair was greatly improved. In particular, in the friction pair of a‐C:H:Ti/a‐C:H with a methane flow rate of 20 sccm, superlubricity is shown, and the wear rate is only 4.04 × 10−9 mm3/Nm. After tribological experiments, Raman spectroscopy, XPS, and other characterization methods were used to study the relationship between the nanostructure and tribological properties of a‐C:H:Ti films and a‐C:H prepared with different methane flow rates. This study is great significance to the application of a‐C:H:Ti/a‐C:H friction pair in mechanical parts under atmospheric environment. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Owing to the high hardness and hydrogen passivation of carbon bonds, hydrogenated diamond‐like carbon (a‐C:H) film has shown promising potential to achieve ultra‐low friction and wear on steel surfaces. Here, a‐C:H film was successfully deposited on 9Cr18Mo steel via programmable high power pulse magnetron sputtering and potential application for industrial was evaluated. The a‐C:H films against different mating materials of GCr15 steel balls, Al2O3, Si3N4, ZrO2, and a‐C:H‐coated GCr15 balls all showed ultra‐low friction under a normal load of 5 N in a dry ambient air environment. Among them, self‐mating tribo‐system a‐C:H films on steel surfaces and a‐C:H‐coated steel balls achieve best friction performance; the principal reason is that both contacting surfaces coated with a‐C:H film have the lower electron affinities compared with other tribo‐systems. However, the differences of coefficient of friction (COF) for uncoated‐GCr15, Al2O3, ZrO2, Si3N4, and a‐C:H(GCr15) balls can be attributed to different sizes of clustering in wear debris. This work provides new insights on synthesis and industry application of the a‐C:H films with ultra‐low friction properties. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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− 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 <0.01, achieving superlubrication. Further systematical investigations on the wear traces, wear debris, and counter balls propose a "dispersion-compensation-filling repairment" friction mechanism. All these results demonstrate that 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. [ABSTRACT FROM AUTHOR]

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 °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 °C, the curved graphene structures gradually increase in films. However, beyond 400 °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. [ABSTRACT FROM AUTHOR]