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Here, we review the benefits of low-temperature pulsed plasma technology on the synthesis of amorphous and diamond-like carbon (DLC) films, nanocrystalline diamond (NCD) films, and carbon nanomaterials, such as graphene and carbon nanotubes. Physical and chemical vapour depositions of strong carbon materials are dominated in industry by magnetron sputtering and vacuum arc. At research stage, carbon deposition can be accomplished by many techniques involving pulsed discharges in vacuum or atmospheric pressure. Either by pulsed-DC glow discharge, high-power impulse magnetron sputtering (HiPIMS), filtered cathodic vacuum arc (FCVA), or anodic arc discharge, the structural and mechanical properties of carbon-based samples can be tailored by adequately adjusting "plasma knobs", namely peak power, pulse duration, and duty cycle. Milestones such as tuning surface properties via ion bombardment, enhancing plasma ionisation through energetic pulses, and stabilization of plasma processes for industrial implementation, are discussed. Also, pulsed plasma technology arises as an excellent laboratory to train machine learning algorithms thanks to the large variety of material properties. In conclusion, nonequilibrium plasmas operated with pulsed power provide exciting opportunities for (1) fabrication of new carbon architectures with desired functional properties for many applications, and (2) advancing our knowledge on carbon plasma chemistry via artificial intelligence resources. [Display omitted] [ABSTRACT FROM AUTHOR]

The tribological behaviour of diamond-like carbon (DLC) and graphene nanoplatelets (GNP) nanocomposite has not been previously explored in a lubricated environment, with some previous studies reporting only on graphene materials on the surface of the DLC. In this study DLC-GNP nanocomposite films with various GNP coverages were synthesised by a 3 step process: spin coating a GNP suspension, heat treatment, and DLC deposition. In this study, the effect of the GNP coverage on the mechanical properties, and tribological response of the DLC-GNP nanocomposite film were studied at elevated temperatures against a cast iron pin in a base-oil lubricated environment. The study shows decrease in friction and wear of the DLC-GNP nanocomposites as the GNP coverage increased, with the lowest friction (COF ∼0.03) and wear (∼1.6 × 10−19 m3/Nm−1) achieved with a 4.5% coverage. This study reports the addition of GNP into the DLC matrix reduced both friction and wear by creating a highly graphitic transfer film on the counter-body, but for higher GNP coverages agglomeration during the spin coating of GNP islands were recorded, leading to removal of the GNP during sliding wear negating the friction reduction effect of the GNP. [Display omitted] [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) has been under the research spotlight as an exceptional solid lubricant. Its friction performance is depending on a well-developed transfer layer upon its counterparts. Nowadays, iron-and brass-based metals have been utilized as the counterpart against DLC, however, it is reported their friction behaviors are somewhat inferior compared to titanium alloys. In this study, we tried to improve their friction behaviors and modified the contact interface from Fe/C to C/C by Ti addition in DLC. It was revealed that Ti, which has good adhesion for Fe and C, promoted the development of carbon transfer on Fe-based counterpart. Furthermore, Ti built-up a thick carbonous transfer layer and make better the friction performance of DLC sliding against Fe. [Display omitted] [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) film is undoubtedly one excellent self-lubricating solid film to improve the fretting behavior due to its ultralow friction as well as high-hardness. Investigating the evolution laws of fretting running state with operating condition and the friction reduction mechanism of DLC film under fretting is vital for reducing friction and wear. Here, the fretting performance of self-mated hydrogen-containing DLC (H-DLC) and Cr-doped DLC (Cr-DLC) was studied under different normal loads and amplitudes. In addition, the mechanism of friction reduction for transfer film and the cause of discrepancy in fretting behavior were clarified through a control experiment. The results demonstrate that as the normal load increases, the relative slip decreases, the elastic deformation increases, and the fretting regime develops towards the partial slip regime, while the increasing amplitude moves the fretting regime towards slip regime. During fretting, the third body layer will transfer to the counterface, and form a uniform and graphitized transfer film. The difference in the length of run-in period and the sp2/sp3 hybrid carbon content of DLC films influences the formation rate and the graphitized degree of the transfer film, which induces the discrepancy of fretting behavior of H-DLC and Cr-DLC films. Thus, this study not only clarifies the evolution on fretting regime of DLC film with changes in working conditions, but also demonstrates the key role of highly graphitized transfer film in fretting performances of self-mated DLC films. This work demonstrates the controllability and potential of self-mated DLC films in the field of fretting. [Display omitted] • The evolution of fretting regime can be completed by adjusting the operating conditions, which can realize the reduction of friction and wear. • The control experiment explained the formation mechanisms of transfer film, and proved the relationship between graphitization and the fretting behavior. • The doping elements of DLC film will affect the hybrid carbon content of sp2/sp3 and the length of run-in period under fretting. [ABSTRACT FROM AUTHOR]

Hydrogenated diamond-like carbon (HDLC) has drawn significant interest as a solid lubricant coating due to its superlubricity. However, HDLC exhibits drastically different frictional behavior depending on hydrogen (H) content or sp2/sp3 carbon ratio. Various structural aspects of HDLC can be analyzed with Raman spectroscopy; but analyzing the wear track on the HDLC surface could not provide insightful information about the shear plane structure because the probe depth of Raman is not shallow enough to discriminate the contribution from the bulk film. When a dissimilar material is rubbed on HDLC, the transfer film is always formed on the counter-surface. Since the transfer film is the direct outcome of frictional shear, one can assume that analyzing the transfer film can depict characteristic features of the shear plane during friction without convolution from the bulk contribution. This study employed microscopic Raman analysis to capture hyperspectral images of the entire transfer films on a stainless-steel counter surface formed from HDLCs with different endogenous H-contents (30 and 40 at.% in the film) in gas environments of N 2 and H 2 (exogenous supply). This analysis provided statistically meaningful data showing how the degrees of graphitization and hydrogenation of the shear plane during the run-in and steady-state friction periods vary with the HDLC structure as well as the environment condition, which is critically needed information to understand how the superlubricity is induced and altered when HDLC is used as a solid lubricant film. [Display omitted] [ABSTRACT FROM AUTHOR]

Silver-doped diamond-like carbon (Ag-DLC) films are considered as promising materials for the surface modification of mechanical components and biological implants. The long-term stability of Ag-DLC films is essential for their commercial use and requires intensive investigation. In this study, DLC and 10.0 at.% Ag-DLC films were prepared using a hybrid deposition technique, and the existence and evolution of Ag atoms over time were systematically studied. The results show that Ag atoms with a lower Ehrlich–Schwoebel barrier than that of C atoms are more prone to interlaminar diffusion, refining the columnar structure of DLC films and thereby creating a compact structure. In the as-deposited Ag-DLC film, Ag atoms mainly existed as fine nanocrystals with sizes ranging from 3 to 5 nm. Ag elements diffused with time during its long-time service, and fine Ag nanocrystals agglomerated to form large nanocrystals. The calculation results by density functional theory confirmed that the proximity of Ag atoms can lower the system energy, rendering agglomeration thermodynamically stable. Molecular dynamics simulations verified the spontaneous migration and agglomeration behaviors of Ag atoms over time. This study was focused on the evolution of Ag-DLC films over time and would provide guidance for their use in long-term applications. [Display omitted] • Ag atoms are more prone to interlaminar diffusion than C atoms. • Ag nanocrystals in Ag-DLC film agglomerate during its long-time service. • Proximity of Ag atoms in Ag-DLC film is thermodynamically stable. • Ag atoms in Ag-DLC film spontaneously agglomerate over time. [ABSTRACT FROM AUTHOR]

In this work, the macroscopic superlubricity with an extremely low coefficient of friction (COF) of 0.004 was achieved on the friction pair of the steel/amorphous carbon (a-C) film with the lubrication of 3-hydroxypropionic acid aqueous solution (3HPA (aq)). The excellent lubrication performance was ascribed to the solid-liquid synergistic lubrication effect between the a-C film and the 3HPA. The triboreaction occurred on the friction pair, resulting in the chemisorption of 3HPA molecules on the a-C film and the steel surface. The hydrated water layer was formed on the chemisorption layer through the hydrogen bonding with water, which contributed to the reduction of COF. Moreover, the feasible graphitization of the a-C film also played an important role on the achievement of superlubricity. This work presented a novel approach for achieving superlubricity on the diamond-like carbon (DLC) and provided support on the development of DLC lubrication in industrial applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Silicon-containing diamond-like carbon (DLC) is a class of thin-film materials with excellent mechanical properties, high thermal stability, and good tribological performance over a wide range of environmental conditions. While non-alloyed/non-doped DLCs also exhibit good biocompatibility and bioinertness, our understanding of the effect of silicon in DLCs on biomolecules/DLC interactions is still elusive. Here, we evaluated the structural, mechanical, and tribological properties of Si-containing DLC coatings with silicon content fraction of 11% and 16%. Tribological tests, performed by sliding a stainless steel pin on the coatings in water, indicated a low friction response (steady-state coefficient of friction <0.11), while quartz crystal microbalance experiments indicated no adsorption of a model biomolecule, namely adenosine triphosphate (ATP), on Si-containing DLCs. Near-edge X-ray absorption fine structure spectromicroscopy analyses performed after tribological experiments provided evidence for an increase in the fraction of silanol surface terminal groups formed in the worn region upon sliding in water without any significant sp3-to-sp2 rehybridization of carbon atoms. The fraction of surface hydroxyl groups in the worn region increases with the silicon content in Si-containing DLC, which leads to a decrease in friction. This tribologically-induced change in surface termination did not lead to the adsorption of ATP upon incubation of tribotested samples in ATP solutions for several hours. These findings open the path for the use of Si-containing DLC in applications requiring good tribological properties in aqueous solution and an excellent resistance to biomolecule surface adsorption that is maintained even after tribologically-induced variations in surface termination. [Display omitted] • Si-containing DLC coatings with [Si] fraction between 11% and 16% were grown. • Increasing [Si] in DLC decreases friction in water. • Sliding in water leads to an increase in silanol surface terminal groups. • No adsorption of ATP occurs on Si-DLCs independently of the surface termination. [ABSTRACT FROM AUTHOR]

Superlubricity between steel/diamond-like carbon (DLC) film could be achieved at vacuum or nitrogen condition, but it would be failed at ambient conditions. In this work, the macroscale superlubricity was achieved at ambient conditions by introducing ethyl lactate into ethylene glycol as lubricant additive for the friction pairs of silicon-doped diamond-like carbon (Si-DLC)/steel. Stable friction coefficient (μ = 0.002) and wear rate of friction pairs with the introduction of ethyl lactate could be respectively reduced by 99 % and 35 %. The characterization tests and density functional theory (DFT) calculation both demonstrated that the partial ethyl lactate was hydrolyzed into lactic acid due to the catalysis effect of steel surfaces. The molecular dynamics (MD) simulation result showed that the lactic acid molecules could be chemically adsorbed on the surfaces of friction pairs, forming a tribofilm through hydrogen bond with ethylene glycol molecules, which led to a significant reduction in the friction coefficient. This work presents a novel approach to achieve superlubricity on Si-DLC film with liquid, providing a great support for industrial application of superlubricity on DLC film. [Display omitted] [ABSTRACT FROM AUTHOR]

The application of hydrogenated diamond-like carbon (H-DLC) with superlubricity can significantly decrease friction and largely save energy dissipation in mechanical systems. Thus, the realization of the near-frictionless state at the engineering scale in both inert and active atmospheres for H-DLC film is of interest. However, the film can achieve the state only under inert and vacuum conditions, while it fails in active atmospheres, such as oxygen and moist air, which seriously hinders wide application of the superlow friction. In previous studies, we have successfully solved this challenge by combining H-DLC film with MoS 2 flakes. Nevertheless, the life of the superlubricity achieved by the MoS 2 /H-DLC composite in an inert gas was extremely short, which was attributed to the failure of MoS 2 -rich transfer films. To establish the near-frictionless state in various atmospheres, graphene oxide with numerous oxygen-containing groups was used to prepare a GO/MoS 2 /H-DLC triple composite in this study. The tribological performances were investigated systematacially. The results demonstrated that the triple composite could establish superlubricity in inert gases and ultralow friction in active atmosphere by forming robust transfer films at sliding interfaces. The structures at frictional interfaces including wear tracks and scars were thoroughly investigated. This work provides a valuable approach for the H-DLC composite to achieve an extremely low friction in various atmospheres and can guide the application of superlow friction in engineering fields. [Display omitted] [ABSTRACT FROM AUTHOR]

Diamond and diamond-like carbon (DLC) coatings are well-known for their exceptional combination of tribological and mechanical properties, such as low friction coefficients and wear rates, together with high hardness and elastic modulus. A significant limitation in their employment concerns their spallation from the substrate; it is thus interesting to explore how DLCs adhesion can be tuned through chemical modifications of its surfaces. We employ ab initio simulations to study the effect of surface reconstruction and chemical species intercalation (B, P, O, F, N, S, H) on the adhesion of non-reconstructed and Pandey-reconstructed C(111)/Cu(111) interfaces. We found that the increment of graphitization at the diamond surface decreases the adhesion. Moreover, when a high degree of surface graphitization is present the best way to increase adhesion is to select atoms able to act as chemical bridges (e.g., B and N), compensating for the lack of interaction between the surfaces. Conversely, adhesion reduction of ∼ 100% can be achieved, regardless of the degree of surface graphitization, by intercalating an atomic species that does not bond with the countersurface and prevents the interaction between the slabs, i.e. F and S. [Display omitted] • Adhesion tuning of DLC coatings is needed to prevent spallation from the substrate. • Effects of surface reconstruction and dopant intercalation are studied using DFT. • Increment of diamond surface graphitization decreases the adhesion. • B and N enhance adhesion when high diamond surface graphitization is present. • F and S cause a drop in adhesion regardless of the level of surface graphitization. [ABSTRACT FROM AUTHOR]

Tribological performance of diamond-like carbon (DLC) films is significantly influenced by relative humidity (RH), especially for applications in harsh environments. This study was aimed to achieve low tribological humidity sensitivity of DLC films via doped FeCrNi medium-entropy alloy (MEA), and reveal the effect mechanism of FeCrNi MEA dopant on DLC films. Experimental and first-principles simulation results show that the friction coefficient of the DLC films without doped FeCrNi MEA changes greatly under different relative humidity levels. However, the friction coefficient of DLC film with FeCrNi MEA target current of 0.6A can continue to stabilize and converge to about 0.16. Under low relative humidity, FeCrNi MEA dopant can exhibit in-situ catalytic effect to promote the more ordered sp2 clusters of the film during friction process. Meanwhile, the chemical reaction inertness of carbon atoms on the contact interface under high humidity can be improved and the generation proportion of high-bond-energy oxygen-containing groups can be reduced with the doped FeCrNi MEA. The above dual action of FeCrNi alloy dopant can lead to a low tribological humidity sensitivity of DLC films under different levels of relative humidity. [Display omitted] [ABSTRACT FROM AUTHOR]

Coal stands poised to emerge as the primary material for sodium-ion battery anode fabrication, owing to its cost-effectiveness and carbon content. Unlike other feedstocks with well-defined structural formulae, coal-based carbon framework commonly presents a mixed state of high-graphitized crystalline and amorphous carbon structure, greatly hindering sodium-ion rapid transport. To overcome the rate bottleneck of coal-based carbon, herein, the thermal conversion pathway of coal is altered by rapid switching of heating and cooling states, thereby reducing amorphous carbon and high-graphitized crystalline in the obtained carbon structure and endowing sodium-ion storage with improved rate capability. Mechanistically, thermal shock accelerates amorphous carbon depolymerization, accompanied by rapid release of gas-phase products, thereby rearranging crystalline growth and promoting pore connectivity. The obtained carbon with optimized crystalline distribution and porosity connectivity alleviates the diffusion resistance of sodium-ions in hard carbon, enabling a greatly improved rate capability (achieving 161 mAh g−1 at a high rate of 2.0 C). Moreover, the fabricated full-cell exhibits an energy density of 236 Wh kg−1 comparable to commercial hard carbon systems, while reducing energy consumption for anode manufacturing by approximately 80 %. This work lays groundwork for regulating amorphous carbon in coal-based anodes and provides an energy-saving production strategy for high-performance hard carbons. [Display omitted] [ABSTRACT FROM AUTHOR]

The unsatisfactory wear resistance and lubrication performance of CoCrNi multi-principal elements alloys (MPEAs) have emerged as critical challenges, impeding their extensive utilization as advanced engineering materials, despite their desirable mechanical and physical properties. Incorporating graphite to obtain MPEAs-based self-lubricating composites is believed to improve the wear resistance. However, it is challenging to prepare composites with high strength, large plasticity, and excellent anti-friction performance simultaneously. The present study reports the fabrication of novel CoCrNi MPEA-based self-lubricating composites, consisting of in-situ graphite and high-hardness silicides/carbides as reinforcement, prepared by powder metallurgy and reactive sintering. The 20.6 vol% Gr@CoCrNi–SiC composite exhibits an optimal trade-off between strength and ductility, along with anti-friction and wear resistance which is superior to the reported composites with different solid lubricants. The wear mechanism is attributed to the coordinated deformation mechanism between the CoCrNi FCC matrix and silicides/carbides, and the stabile lubrication effect supported by the structural transformation from the original polycrystalline lattice structure to core-shell nanocomposite structure (similar to diamond-like carbon) of the in-situ graphite. This simple, economical and practical strategy contributes to the development of MPEA self-lubricating composites with excellent comprehensive properties. [Display omitted] [ABSTRACT FROM AUTHOR]

Flexible supercapacitors (SCs) based on carbon nanomaterials are one of the promising energy storage devices for wearable electron devices. However, their low energy density and cycle stability severely restrict further practical applications. The development of unique capacitor electrodes is expected largely to overcome these challenges. Herein, vertical 3D diamond/graphite (DG) composite films are directly grown on carbon cloth (CC) using a microwave plasma chemical vapor deposition (MPCVD) technique. Thin, straight nanosheets, consisted of diamond as core and graphite as shell, are interlaced with each other to form a 3D porous structure. As a binder- and additive-free electrode material, the DG/CC electrodes are used to construct electrical double layer capacitors (EDLCs) in diluted H 2 SO 4 solution and pseudocapacitors (PCs) using Fe(CN) 6 3−/4- redox electrolytes. Both EDLCs and PCs exhibit large specific capacitance and high capacitance retention. When assembled as all-solid-state flexible symmetric SCs, they offer high full-cell capacitances of 30.4 and 143.6 mF cm−2 at 10 mV s−1 for EDLCs and PCs, respectively. The power densities are 6.3 μW cm−2 and 3.0 mW cm−2 for EDLCs and PCs, together with their energy densities of 3.7 and 86.2 μWh cm−2, respectively. As flexible SCs, the specific capacitance can be completely recovered for EDLCs and has only about 6.7% loss for PCs even after the U-shape bending state. Such vertical 3D porous DG films are thus promising for the construction of high-performance battery-like SCs for an intelligent wearable energy supplier. [Display omitted] • Vertical 3D diamond/graphene composite films were synthesized on carbon cloth to construct battery-like flexible SCs. • In-situ electrochemical anodic polarization treatment remarkably enhanced the electrochemical performance. • High energy densities with large power densities were obtained in the battery-like SCs. [ABSTRACT FROM AUTHOR]

We describe the formation of highly uniform Quenched-carbon (Q-carbon) layers by plasma-enhanced chemical vapor deposition (PECVD) followed by low-energy Ar+ ion bombardment to achieve wafer-scale integration of Q-carbon films. After PECVD, 9 nm and 20 nm thick silicon-doped diamond-like carbon (Si-DLC) films showed complete conversion into Q-carbon using 250eV Ar+ ions via negative biasing. However, this conversion was only partial for 30 nm thick films. Detailed EELS, XPS, Raman, and EDS studies were carried out to confirm the formation of Q-carbon by this method. We discuss the mechanism of Q-carbon formation as a result of low-energy ion bombardment during PECVD of thin films. These ions during negative biasing are energetic enough to create Frenkel defects, which support the conversion of the three-fold coordinated sp2 carbon units in as-deposited carbon into sp3 bonded five-atom tetrahedron units in Q-carbon. This process enhances the atomic number density and fraction of sp3 bonded carbon. These diamond tetrahedra are randomly packed and provide easy nucleation sites for diamond. If the underlying substrate can provide an epitaxial template for diamond growth via domain matching epitaxy, then wafer-scale growth of diamond epitaxial films can be achieved for wafer-scale integration and next-generation novel device manufacturing from diamond-related materials. [Display omitted] • New method for the formation of uniform, wafer-scale silicon-doped Q-carbon (Si-Q-carbon). • Via low-energy ion bombardment, conversion of Si-DLC into Si-Q-carbon was performed. • Ion bombardment provided the energy for the formation of Frenkel pairs. • Frenkel pairs converted 3-fold coordinated sp2 carbon units Si-DLC into sp3 bonded 5-atom tetrahedron units in Si-Q-carbon. [ABSTRACT FROM AUTHOR]

We present the first in situ transmission electron microscope (TEM) study of extended sliding of diamond-like carbon (DLC) on diamond. We show how the tribological properties of amorphous carbon (a-C) reach their limit by exploring the onset of wear for the harsh condition of sliding against diamond in vacuum. A particularly hard, hydrogen-free member of the DLC family, a-C is of wide technological interest, but the mechanisms by which damage occurs during tribological contact are not well understood. Real-time TEM imaging of the nanoscale contact area provides insight into wear mechanisms and damage. We show that at high normal stresses with full sliding contributing to additional shear stress, the initially low adhesion of the a-C-diamond interface rapidly increases at a rate greater than is seen in similar silicon-diamond contact studies. We propose that high contact stresses wear away a relatively low surface energy sp2-rich layer on the outer a-C surface, exposing sp3-rich sub-layers which can form covalent bonds that require more tensile force to be broken, leading to higher adhesion and an acceleration of wear. [Display omitted] • The first in situ TEM study of extended sliding of DLC on diamond. • Revealed real-time TEM imaging of sliding-induced wear. • Disclosed dependency of adhesion on stress and speed. • The initially low adhesion of the a-C-diamond interface rapidly increases. • High contact stresses wear away sp2-rich layer on the a-C surface. [ABSTRACT FROM AUTHOR]

Environmentally friendly thermal interface materials (TIMs) with bidirectional high thermal conductivities have aroused considerable interests for addressing the heat dissipation issue in integrated circuits. Although graphene-based TIMs exhibit excellent in-plane thermal conductive performance, their through-plane thermal conductivity is commonly less than 3 Wm−1K−1 owing to the vast interfacial phonon scattering, significantly limiting their practical applications. In this study, a strategy aimed at building TIMs with controllable heat transfer pathways both along the in-plane and through-plane directions is proposed by incorporating micron-diamonds (MDs) in graphene nanoplatelets/nanofibrillated cellulose (GNPs/NFC) composite film via a facile and green self-assembly method. The morphology of the obtained MDs@GNPs/NFC composite film can be precisely tailored from a hierarchical structure to a 3D solid foam-like structure to tailor heat transfer paths. By adjusting the loading and particle size of MDs, a through-plane thermal conductivity of 8.85 Wm−1K−1 was achieved accompanied with a simultaneously high in-plane thermal conductivity of 32.01 Wm−1K−1. The excellent bidirectional thermal conductive performance is integrated with high-efficiency Joule heating capability, outstanding nonflammability, as well as superior electromagnetic shielding performance, showing a promising future in advanced electronic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Doping enhances diamond like carbon (DLC) coatings for extreme high-temperature applications. However, understanding the enhancement mechanism is elusive. This study employs a novel system integrating Raman spectroscopy and depth-sensing indentation with a heating chamber to monitor chemical structural, and mechanical properties of doped and un-doped hydrogenated DLC films, with temperature. This in-situ investigation represents extreme working conditions, revealing how doping enhances DLC films thermal stability. It is shown that the thermal stability of the a-C:H:Si films could be maximized by increasing the Si content. The film with the highest Si content was stable until 650 ̊C while the films with lower Si or No–Si content graphitized at lower temperatures. This study presents hardness measurement under high-temperature conditions that were not available before. In-situ observations reveal how Si doping correlates with stability of mechanical properties at elevated temperatures. The correlation of the mechanical properties with W G reveals that the mechanism of thermal stability is that Si doping makes the film resistant to graphitization by promoting sp3 hybridization. Furthermore, our in-situ approach makes it possible to conduct characterization that emulates real service conditions, and therefore, our results show great potential of the industrial application of DLC coatings in extreme thermal conditions. [Display omitted] • In-situ thermal stability analysis of the a-C:H:Si films with temperature rise. • Thermal stability of a-C:H:Si films is greatly enhanced by increasing Si content. • The film with the highest Si content was stable until at least 650 ̊C. • The films with lower Si or no Si content graphitized at much lower temperatures. • Hardness of the films is measured under high-temperature conditions. [ABSTRACT FROM AUTHOR]

We predict the three-dimensional structure of amorphous carbon generated by heating diamond superlattice at 6000 K with rapid quenching from the liquid phase for densities ranging from 2.0 to 3.5 g/cm3, in comparison with 2.26 and 3.54 g/cm3 for bulk graphite and bulk diamond, respectively. These predictions are based on reactive dynamics (RD) simulations using the ReaxFF reactive force field. Here, we simulate the graphitization of amorphous carbon at high temperature to calculate physical properties relevant to conductive carbon supports useful for electrocatalysts. The low-density graphitic materials mostly oriented in the (002) plane with a main X-ray diffraction (XRD) peak between 26 and 28°, as observed experimentally. For low density carbon (2.0–2.5 g/cm3), we find >90% sp2 character with ∼2-1% sp and <8% sp3. While for higher density carbon, the amount of sp2 fraction decreases with density and find 70.0% sp3 with 29.7% sp2 and 0.3% sp for 3.4 g/cm3 density, which can be compared to DLC of 3.24 g/cm3 density resulting good agreement with XPS experiments. Based on the simulated 3D structure, we create 2D surface slab consisting of various defective sites within the surface. The 2D surface dominates with hexagonal carbon ring along with few pentagon and heptagon rings in the graphitic structure that may be useful as electrocatalysts for different energy conversion reactions. [Display omitted] • Reactive dynamics (RD) simulations were carried out to describe graphitization process at high temperature using ReaxFF. • The low-density carbon consists of more than 90% sp2 character while higher density produce majority (>70.3%) sp3 character. • We predicted 2D graphite surface consisting various pattern layers with many defects including 4–8 ring member carbon. • The carbon structures were properly described using measurable properties and interpreted with experimental literatures. • Moreover, our predicted structure could be used as carbon electrode supports for electrocatalysis. [ABSTRACT FROM AUTHOR]

In this study, different types of carbon films, including diamond-like carbon (DLC), fullerene-like carbon (FLC), and nanocrystalline diamond (NCD) films, were studied in detail. The film structural and property changes before and after heavy-ion irradiation with increased displacement damage were investigated. The results reveal that radiation-induced structural changes result in heavily degraded lubricant properties of DLC and FLC films but can help improve the lubricant properties of NCD films. The displacement damage of 2.0 dpa was a threshold parameter above which the nanocomposite NCD films stepped into a quasi-saturation state to create an amorphous structure with an ultralong lifetime (more than 6.0 × 105 cycles) and excellent antiwear properties (magnitude of 10−7 mm3/N‧m), which is of great importance for the application of NCD films in nuclear reactors. The radiated NCD films could produce tribofilms configured in an amorphous structure, which provided superior lubricant properties to the graphitic tribofilms of DLC and FLC films. The results also contribute to a novel principle for prolonging the lifetime of solid lubricant films in ion-radiation environments, based on the significant tribological properties of the radiation-produced amorphous layer in a quasi-saturation state. [Display omitted] • Heavy-ion irradiation is beneficial in improving lubricant properties of NCD films. • Quasi-saturated NCD films exhibit excellent anti-wear properties than DLC films. • Radiated NCD films produce amorphous tribofilms with good antiwear properties. • A novel principle prolongs the lifetime of NCD films in irradiation environments. [ABSTRACT FROM AUTHOR]

The influence of corrosion upon the nanoscale topography and friction response of a hydrogenated amorphous carbon film (a-C:H) was investigated. Electrochemical atomic force microscopy was used to characterise topographical changes to the coating at two oxidative potentials. Corrosion of the coating at 1.5 V (corrosion rate 0.5 nm h−1) resulted in no changes to the nanoscale topography; whereas corrosion at 2.5 V (corrosion rate 26.4 nm h−1) caused the root mean square roughness of the a-C:H film topography to decrease, but the local fine-scale irregularity or 'jaggedness' of the surface to increase. X-ray photoelectron spectroscopy revealed that corrosion at both potentials oxidised the a-C:H surface to form alcohol, carbonyl and carboxyl groups. Lateral force microscopy and adhesion force measurements showed that both the friction force and surface adhesion of the coating increased upon corrosion. The outcome was attributed to the surface oxidation that had occurred at both oxidative potentials, resulting in several potential mechanisms including increased attractive intermolecular interactions and capillary forces. The highest friction coefficient was observed for the a-C:H film corroded at 2.5 V, and identified as a consequence of the jagged surface topography promoting an interlocking friction mechanism. [Display omitted] [ABSTRACT FROM AUTHOR]

Lubrication by graphene from nanoscale to macroscale has attracted increasing interest in recent years. However, the graphene can only withstand load of 2 N (corresponds to Hertzian contact stress of 0.41 GPa) during sliding. In this work, a composite of graphene and sodium carbonate coating shows an improved load-carrying capability during lubricated contacts. Compared to the pure graphene deposited coating, the composite can reduce the friction from 0.6 to 0.16 and wear by one order of magnitude at 1.29 GPa, and can provide an effective lubrication even at the high load of 40 N (corresponds to maximum Hertzian contact stress of 2.06 GPa). The improved lubricating property by the composite of sodium carbonate and graphene results from the stronger adhesion of the composite on the steel surface and the sliding induced soft tribofilm formed at the rubbing interface. Interface observation indicates a high sp2 fraction of carbon at the top of the tribofilm which contributes to the easy slippery. This study provides a new approach to widen the applications of graphene to lubricated contacts under heavier loads. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon-based materials including diamond-like carbon (DLC) and graphene have been demonstrated as extraordinary lubricating materials due to its specific structure and weakness of the interlayer interactions. In this work, the extreme coefficient of friction (COF = 0.002) was achieved on the silicon-doped hydrogenated amorphous carbon (a-C:H:Si) film by lubrication with graphene oxide (GO) nanosheets as additives in ethylene glycol. The tribochemical reactions occurred on the Si 3 N 4 surface and a-C:H:Si film, leading to the formation of the silica colloid layer on both Si 3 N 4 and a-C:H:Si surfaces. In the meantime, the physical adsorption of GO nanosheets on the friction surfaces makes the shear plane transfer from Si 3 N 4 /a-C:H:Si interface to GO/GO interface, which results in a further reduction of shear stress. The mechanism and modelling of a-C:H:Si and GO nanosheets synergistic lubrication effect was finally established to reveal the design principle of superlubricity at macroscale. [Display omitted] [ABSTRACT FROM AUTHOR]

The origins of low friction of hydrogenated diamond-like carbon (H-DLC) films depending on unidirectional and reciprocating motions were detected by the analyses of transmission electron microscopy (TEM), Raman spectroscopy and atomic force microscopy (AFM). Under the comparable experimental conditions, the reciprocating sliding of H-DLC films against a steel ball in humid air enables the stable friction coefficient to lower more than 70% but the surface wear to increase 50% compared to the unidirectional sliding. The uniformity and structure of transfer layer and worn H-DLC surface strongly depend on sliding motions. Two-way movements in the reciprocating sliding help to keep the transfer layer within contact region, enhancing its graphitization. TEM image of transfer layer shows the formation of abundant graphene nanoscrolls in reciprocating sliding but only few graphite layers in unidirectional sliding. AFM results and Raman spectra suggest that not only the transfer layer but also the graphitization of the rough worn H-DLC surface induced by high alternating stress plays a significant role in the low friction under reciprocating motion. Combining the atomic-scale, nanoscale and macroscale results, a comprehensive model is proposed for the statement of low friction sliding contact of H-DLC films depending on the sliding motions. Image 1 • Reciprocating motion enables lower COF but larger wear than unidirectional motion. • Abundant nanoscrolls and graphene in transfer layer formed in reciprocating motion. • Graphitization of worn H-DLC surface contributes to low COF in reciprocating motion. • Two-way movements in reciprocating motion confine transfer layer in contact region. • Alternating stress in reciprocating motion leads to a rougher worn H-DLC surface. [ABSTRACT FROM AUTHOR]

Despite several theoretically proposed two-dimensional (2D) diamond structures, experimental efforts to obtain such structures are in initial stage. Recent high-pressure experiments provided significant advancements in the field, however, expected properties of a 2D-like diamond such as sp3 content, transparency and hardness, have not been observed together in a compressed graphene system. Here, we compress few-layer graphene samples on SiO 2 /Si substrate in water and provide experimental evidence for the formation of a quenchable hard, transparent, sp3-containing 2D phase. Our Raman spectroscopy data indicates phase transition and a surprisingly similar critical pressure for two-, five-layer graphene and graphite in the 4–6 GPa range, as evidenced by changes in several Raman features, combined with a lack of evidence of significant pressure gradients or local non-hydrostatic stress components of the pressure medium up to ≈ 8 GPa. The new phase is transparent and hard, as evidenced from indentation marks on the SiO 2 substrate, a material considerably harder than graphene systems. Furthermore, we report the lowest critical pressure (≈ 4 GPa) in graphite, which we attribute to the role of water in facilitating the phase transition. Theoretical calculations and experimental data indicate a novel, surface-to-bulk phase transition mechanism that gives hint of diamondene formation. Image 1 [ABSTRACT FROM AUTHOR]

In this work, we designed three series of tribo-couples based on amorphous carbon films including GLC, DLC and PLC that were modified by graphene quantum dots (GQDs). The tribo-testing environment was controlled at harsh conditions (like heavy load and high speed) in dry nitrogen atmosphere using bare and film-coated bearing steel balls as counterbodies, respectively. Through the tribochemical interactions, the self-mated DLC system obtained a surperlubricity state (μ = 0.01). During the whole sliding, the contact surface of the upper counterfacing ball was covered by 2D-layered carbon and graphitic lubricants induced via structural transformation of GQDs. Meanwhile, the tribofilm of the disc wear track was composed of a silica-like SiO x boundary layer and a multicomponent mixed-layer induced by tribochemistry. Compared to the self-mated DLC system, the structural boundary enriched with SiO x compounds was not formed at the bottom region of the tribofilm for the bare steel system; meanwhile, the disc wear track was covered by a thicker tribofilm containing plenty of degraded GQDs. This inferred the fact that the formation of a nanostructured sliding interface was the key to realize superlubricity. These discoveries successfully afforded a lubrication mechanism of GQDs for solid lubricant in applications of engineering and industry. Image 1 • Graphene-quantum-dots lubricants with effective friction-reducing effects are achieved. • The lubricity depends strongly on the tribo-couple materials and surface strucutre. • The nanostructured tribofilms formed on the contacts govern the superlubricity mechanisms. [ABSTRACT FROM AUTHOR]

Creation of the hybrid nanostructures with superior properties that combine the advantages of hardest diamond and flexible graphite remains challenging in experiment. Here we report a new strategy for the synthesis of diamond-graphite hybrid nanocomposite from multi-walled carbon nanotubes fibers by laser heating diamond anvil cell. A combined theory experiment approach confirms the formation of diamond-graphite hybrid structure with the coherent interface consisted of covalent bonds between diamond and graphite. This opens an avenue for the synthesis of diamond-graphite hybrid structure, which may be extended to generate new carbon nanocomposites using other suitable carbon precursors by high pressure. Image 1 [ABSTRACT FROM AUTHOR]

Diamond and diamond-like carbon coatings are used in many applications ranging from biomedicine to tribology. A wide range of dopants have been tested to modify the hydrophilicity of these surfaces, since this is central to their biocompatibility and tribological performance in aqueous environments. Despite the large number of experimental investigations, an atomistic understanding of the effects of different dopants on carbon film hydrophilicity is still lacking. In this study, we employ ab initio calculations to elucidate the effects of B, N, and O dopants in several mechanisms that could modify interactions with water molecules and thus hydrophilicity. These include the adsorption of intact water molecules on the surfaces, minimum energy pathways for water dissociation, and subsequent interactions of hydrogenated and hydroxylated surfaces with water molecules. We find that all of the dopants considered enhance hydrophilicity, but they do so through different means. Most notably, B dopants can spontaneously chemisorb intact water molecules and increase its interactions in H-bond networks. Image 1 • The microscopic mechanisms for interaction between water molecules and B-, N-, and O-doped diamond were elucidated. • All dopants presented mechanisms to enhance hydrophilicity. • B dopants chemisorb intact water molecules and enhance their participation in the H-bond network. • N dopants increase wettability through polar N–C and N–H bonds. • O dopants in bridge locations increase wettability through induced dangling bonds in an unsaturated surface. [ABSTRACT FROM AUTHOR]

Compared with traditional impact-resistant materials, nanocarbon materials have the advantages such as light weight, large specific volume for energy dissipation and their exceptional thermal stability for the extreme-environmental working potentials. However, based on the commonly used fabrication method, the general nanocarbon structures (e.g. carbon nanotube (CNT) array) are always constructed with the weak interaction between units. Therefore, when they are subjected to impact, the impact energy cannot be transferred throughout the whole loose and discontinuous structure efficiently, which results in the degradation of their impact-resistant capabilities. To address the above issue, we fabricated a nanocarbon "cushion" with the combination of a diamond like carbon (DLC) film and multi-wall CNT (MWCNT) array. The DLC film was deposited successfully onto the as-grown MWCNT array through enhanced glow discharge plasma immersion ion implantation and deposition (EGD-PIII&D) method to form a continuous upper layer which is vital to distribute and transfer the impact energy loading. The new nanocarbon system has high specific dissipated energy up to ∼2.22 kJ/m3, which is almost twice as much as that of the commercial polyurethane sponge. We anticipate that this study will provide new insights to develop novel nanocarbon materials for impact resistance in high-tech edge applications. Image 1 • A nanocarbon "cushion" by combining a diamond like carbon film and a multi-wall CNT array was firstly reported. • The structure design of nanocarbon cushions enables the release of impact energy throughout the whole material. • The specific dissipated energy of nanocarbon cushions is about 2-fold higher than that of commercial polyurethane sponges. • The nanocarbon cushions are promising to address the protective issues in the specific high-tech fields. [ABSTRACT FROM AUTHOR]

Constructing more efficient air/solid/solution tri-interface for carbon-based oxygen reduced reaction (ORR) electrodes and evaluating the effects of layer numbers of graphene supporter loaded with defects on ORR performance are never explored before. We have successfully assembled vertical graphene sheets (VGs) with edge defects as catalyst centers on separated papillary granules formed (SPF) nanocrystalline diamond films (NCD) and firstly prepared high hydrophobic and high sticky carbon-based electrodes with highly efficient ORR performance. The results show that we regulate the VGs from lying to erect, providing hydrophobic surface to super-hydrophobic surface with high sticky. As the surfaces with medium static contact angle (SCAs)(130°∼140°) and high stickiness produce appropriate negative pressure to drag enough electrolyte to soak the VGs and still leave air pockets among SPF to form quantities of air/solid/liquid tri-interface, the VG-on-SPF-NCD electrodes possess better ORR performance. We firstly combine the I D' , I 2D /I G and FWHM 2D values from Raman spectra to express the defects loaded on fewer layers of graphene. It is a more precise way to assess the ORR catalytic active defects on carbon materials. Our results supply a simple way to construct catalytically active VGs on SPF nanocrystalline diamond films. Image 1 [ABSTRACT FROM AUTHOR]

In this study, we prepared Q-carbon by adjusting the sp 3 content in diamond-like carbon (DLC) films and the laser energy density of pulsed laser annealing (PLA). The amorphous DLC films were fabricated on sapphire Al 2 O 3 (0001) substrates using a pulsed laser deposition technique with a KrF excimer laser (λ = 248 nm). The sp3 content in the films varied between 20% and 42% by changing the laser energy density. Subsequently, PLA was performed on the DLC films by using the KrF excimer laser with energy densities between 0.5 and 1.2 J/cm2. The prepared films were characterized using scanning electron microscopy, Raman spectroscopy, and magnetization measurements. Consequently, for the combination of 20% sp 3 content and laser density of 1.0 J/cm2, as well as 42% sp 3 and 0.5 J/cm2, the films showed the characteristic features of Q-carbon: filamentary nanostructures, the presence of a T band in the Raman spectrum, room-temperature ferromagnetic behavior, and ∼80% sp 3 content. The results indicate that Q-carbon can be obtained by using a proper combination of sp 3 content in DLC films and an appropriate PLA energy density. This study provides important guidance for establishing a preparation method for Q-carbon. Image 1 [ABSTRACT FROM AUTHOR]

The presence of sp2 bonded carbon on a diamond or doped diamond surface, as a result of growth or processing, can affect material properties negatively, hence removal processes must be developed. Using boron doped diamond (BDD) we investigate the effectiveness of different removal methods via electrochemistry and transmission electron microscopy. We focus on two BDD surfaces, one processed by ns laser micromachining and the second which contains sp2 bonded carbon as a result of chemical vapour deposition (CVD) growth. After micromachining a layer of ordered graphite sits on the BDD surface, topped by fissured amorphous carbon (total thickness ∼ μm). Oxidative acid treatment at elevated temperature cannot remove all the sp2 bonded carbon and much smaller clusters of perpendicularly-orientated graphite (tens of nm in diameter), capped with a thinner layer of amorphous carbon – that we term "denatured graphite" – remain. In contrast, thermal oxidation in air at 600 °C is capable of all cluster removal, and can also be used to remove sp2 bonded carbon from as-grown CVD BDD. Such understanding is important to any application where sp2 bonded surface carbon resulting from CVD growth or laser processing is detrimental for the intended application, e.g. in diamond quantum technology, photonics and electrochemistry. Image 1 [ABSTRACT FROM AUTHOR]

Diamond is the hardest superhard material with excellent optoelectronic, thermomechanical, and electronic properties. Here, we have investigated the possibility of a new synthesis technique for diamane and diamond thin films from multilayer graphene at pressures far below the graphite → diamond transformation pressure. We have used the Molecular Dynamics technique with reactive force fields. Our results demonstrate a significant reduction (by a factor of two) in the multilayer graphene → diamond transformation stress upon using a combined shear and axial compression. The shear deformation in the multilayer graphene lowers the phase transformation energy barrier and plays the role of thermal fluctuations, which itself promotes the formation of diamond. We revealed a relatively weak temperature dependence of the transformation strain and stresses. The transformation stress vs. strain curve for the bulk graphite drops exponentially for finite temperatures. Image 1 [ABSTRACT FROM AUTHOR]

The single layer diamond – diamane, a two-dimensional (2D) form of diamond with a bilayer sp3 carbon nanostructure, has been initially predicted in 2009, while its experimental synthesis has only been reported very recently. This work carries out a comprehensive study on the vibrational properties of diamane nanoribbon (DNR) targeting the ultra-sensitive sensing applications. Based on in silico studies, it is found that the DNR resonator possesses a higher natural frequency and a large quality factor (Q-factor) on the order of 105 higher than those of a bilayer nanoribbon resonator. Under pre-tensile strain, the natural frequency of the DNR resonator receives a remarkable increase and its Q -factor maintains a high magnitude yielding to an extremely high figure of merit on the order of 1015. It is further found that the randomly distributed surface hydrogenation exerts negligible influence on the vibrational properties of the DNR resonator. However, an unevenly distributed hydrogenation results in out-of-plane deformation and significantly changes its vibrational properties. It is additionally found that the stacking configuration of the diamane leads to negligible influence on its vibrational properties. This study reveals that the DNR resonator has excellent vibrational properties, which are promising for the construction of ultra-sensitive resonator-based sensors. The single layer diamond – based mechanical resonator shows excellent properties compared with other 2D materials-based resonator. Image 1 [ABSTRACT FROM AUTHOR]

Ultrahard nanotwinned diamond (nt-D) is an ideal material for next-generation high-precision, high-efficiency cutting tools, due to its high hardness, enhanced fracture toughness, and increased oxidation resistance temperature, when compared with natural diamond. However, a critical problem that limits the application of such material is the grinding and polishing of nt-D material into suitable shapes. In this study, we confirmed the feasibility of classical mechanical polishing for nt-D through amorphization transition. The effect of mechanical loading and the catalysis of Fe nano-particles work together, promoting the transformation of nt-D into a hard sp 2- sp 3 amorphous carbon. The surface of the amorphous carbon layer and the interface between amorphous carbon and nt-D were both smooth after polishing. The results are valuable for the mechanical processing and further applications of ultrahard nanotwinned diamond. Image 1 [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) films are capable of offering low friction coefficient and high wear resistance when rubbed in both dry and lubricated interfaces. However, the inherent mechanisms governing fretting wear in DLC films with temperature are still not well comprehended. Herein, atomic-scale analysis was conducted to unveil the relationship between interfacial tribofilms and the fretting wear behaviors. The results emphasize the determining role of the interaction between the tribo-sintered tribofilms and the transferred carbon tribofilms, as well as the structural evolution in the DLC film with temperature. The room temperature (RT) fretting experiment establishes a bilayer nanostructured tribofilm with a C-rich transfer layer on a Fe-rich tribo-sintered layer. As the fretting temperature elevates the graphitization degree of the tribofilms exacerbates, surface oxidation and hydrogen effusion arise in the DLC film, resulting in higher friction coefficients and wear rates. Chromium outward diffusion at 500 °C establishes a Cr-rich interlayer in the tribofilm, which forms interfacial chromium-carbon bonds, promotes adhesive carbon transfer, and leads to the sharp increase of the friction force and wear rate. These findings provide new insights into the fretting wear mechanisms, and provide guidance for the application of DLC films in elevated-temperature fretting scenarios such as aero-engines tenon and spline connections. [Display omitted] •Carbon transfer layer established on Fe-rich tribo-sintered layer in fretting. •Chromium out-diffusion at high temperature generates Cr-rich interlayer. •Cr-rich layer boosts carbon transfer and forms sandwich structured tribofilm. •Cr–C interaction, graphitization, and hydrogen loss deteriorate fretting wear. [ABSTRACT FROM AUTHOR]

Superlubricity, a fantastic lubrication sate where friction or resistance to sliding nearly vanishes, has become one of the most important approaches to combat friction-induced energy consumption and devices failures. Emerging carbon nanostructures endow the research community with unprecedented opportunities to realize superlubricity across different length scales. This review provides an overview of the state-of-the-art of nanostructured carbon-based superlubricity, with a specific emphasis on unusual properties and new phenomena in representative carbon materials including layer carbon structure, diamond-like carbon, onion-like/fullerene-like carbons, ultra-nanocrystalline diamond and carbon nanotubes. The scientific fundamentals and technical routes to achieve superlow friction are highlighted for each individual carbon nanostructure. Perspectives on current challenges are put forward, and the possible future directions to guide the development of this field are suggested. Image 1 [ABSTRACT FROM AUTHOR]

Despite recent literature reporting the remarkable electrochemical CO 2 reduction reaction (CO2RR) performance of nitrogen-doped graphitic carbon materials (sp 2 -carbon) and nitrogen-doped diamond materials (sp 3 -carbon), no systematic studies have been conducted on the catalytic activities of hybrid carbon nanomaterials between diamond and graphitic extremes. In this study, nitrogen-doped ultra-nanocrystalline diamond thin films were prepared by a microwave-assisted chemical vapor deposition technique. The ratio of sp 2 -carbon phase to sp 3 -carbon phase was controlled by varying growth conditions. Our results confirm that nitrogen-doped sp 2 -carbon (graphitic) rich electrodes have better selectivity for the CO2RR products over the nitrogen-doped sp 3 -carbon rich electrodes, indicating that the host structure of nitrogen dopants is crucial for the catalytic activity. Nitrogen-doped sp 2 -carbon electrodes present Faradaic efficiency for CO production up to 82% with excellent activity and selectivity. The vital role of the host structure and the potential catalytic sites were detailed by density functional theory (DFT) calculations. Image 1 [ABSTRACT FROM AUTHOR]

Hydrogenated amorphous carbon (a-C:H) is subjected to abnormal high friction in ambient air, and the possibility to retain an ultra-low friction state remains as a great challenge. Here, nanodiamond and graphene were used as solid lubricants to improve the tribological properties of two representative types of a-C:H films with 20 at.% and 40 at.% hydrogen contents, respectively. The results emphasize the exceptionally synergetic lubrication effect of nanodiamond + graphene composite with a mass ratio of 1:1 and a solution-processed concentration of 0.1 mg/mL. An ultra-low friction coefficient of ∼0.02 was achieved for a-C:H (20 at.% H) film, and more strikingly, a dramatic reduction in COF from 0.52 to 0.07 was realized in a-C:H (40 at.% H) film. Meanwhile, the wear rates of the counterparts in both cases are significantly reduced in the presence of nano-lubricants. The lubricity mechanisms are mainly based on the in-situ growth of nanostructured tribolayers. The roles of a-C:H film bonding characteristic and the tribo-induced structural evolution of nano-lubricants in the build-up of anti-friction and wear-resistant tribolayers are discussed. These findings can enrich the understanding of surface modification pathways to a-C:H films via low-dimensional nano-lubricants and help to develop more adaptive and robust solid carbon films. Image 1 [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) is one of the most promising solid lubricants for sliding against other materials, such as steel, alumina, and silicon carbide (SiC). During sliding, a DLC transfer film is usually formed on the counterpart surface, affording a low friction coefficient. It is well known that hydrogen in DLC strongly promotes the formation of the DLC transfer film. To further improve the lubricity of DLC, we investigate the formation mechanisms of the DLC transfer film on amorphous SiC and the influence of hydrogen on transfer film formation using reactive molecular dynamics simulations. In addition to the conventional transfer mechanism induced by surface adhesion, we herein propose the new transfer mechanism of "hydrocarbon-emission-induced transfer". In the proposed transfer mechanism, hydrocarbon molecules are emitted from the DLC surface and subsequently adsorb on the counterpart surface during the continuous grinding of the sliding interface, ultimately generating the DLC transfer film. Furthermore, the addition of hydrogen atoms to DLC slightly increases the adhesion-induced transfer and greatly accelerates the "hydrocarbon-emission-induced transfer", collaboratively contributing to substantial DLC transfer film formation. Thus, we suggest that the experimentally observed promotion of DLC transfer film formation by hydrogen is largely attributable to our proposed mechanism of "hydrocarbon-emission-induced transfer". Image 1 [ABSTRACT FROM AUTHOR]

Ti-doped diamond-like carbon nanocomposite thin films with different Ti contents are prepared by closed field unbalanced magnetron sputtering. Designed Ti target current increases from 0.3A to 1.0A. The effect of Ti content on microstructures and properties is investigated. The phases of nano-TiC and amorphous carbon are confirmed. The film (containing less than 50% sp3 C content) deposited with a Ti target current of 0.4A obtains the highest hardness of 44.6 GPa, which is rarely reported. Besides, the film with a Ti target current of 0.3A exhibits the lowest the friction coefficient of 0.02 and 99.10% reduction in wear rate compared with the untreated specimen due to its lubricating effect and the gradient multilayer structure. Moreover, the films have a high open-circuit corrosion potential, a low anodic current density and a wide passivation range, indicating its enhanced corrosion resistance. Most importantly, these inspiring results demonstrated that the excellent mechanical, tribological and anti-corrosion properties can be realized simultaneously by introducing the as-deposited films with the merits of high hardness, self-lubricating and chemical inertness. Image 1 [ABSTRACT FROM AUTHOR]

The construction of simple and low-cost light-emitting diode (LED) based on carbon dots (CDs) powder is an important and challenging task. Here, diamond-like carbon (sp3C) structure-doped carbon dots (D-CDs) powder was prepared within 8 min via a one-step microwave-assisted pyrolysis route with a high production yield of 67.8%. The obtained D-CDs powder emits bright solid-state fluorescence without any other additional solid matrices and exhibits a quantum yield of 67.7%. Self-quenching effect caused by direct π-π interactions and fluorescence resonance energy transfer is strongly suppressed by the sp3 and sp2 carbon hybrid structure and the single energy level in the D-CDs powder. The D-CDs powder was directly employed as phosphors in LED, and bright blue LED was successfully constructed with maximum luminance achieving 3922 cd m−2. More importantly, the introduction of diamond-like carbon (sp3C) structure opens a new era for the preparation of CDs powder with solid-state fluorescence. Image 1 [ABSTRACT FROM AUTHOR]

The phase stabilities as well as some intrinsic properties of hydrogenated diamondized bilayer graphenes, 2-dimensional materials adopting the crystal structure of diamond and of lonsdaleite, are investigated using a first-principles approach. Our simulations demonstrate that hydrogenated diamondized bilayer graphenes are thermodynamically stable with respect to bilayer graphene and hydrogen molecule even at 0 GPa, and additionally they are found to withstand the physical change in structure up to at least 1000 K, ensuring their dynamical and thermal stabilities. The studied hydrogenated diamondized bilayer graphenes are predicted not only to behave as direct and wide band gap semiconductors, but also to have a remarkably high resistance to in-plane plastic deformation induced by indentation as implied by their high in-plane elastic constants comparable to those of diamond and of lonsdaleite. The mechanical stability of the materials is confirmed though the fulfilment of the Born stability criteria. Detailed analysis of phonon vibrational frequencies of hydrogenated diamondized bilayer graphenes reveals possible Raman active and IR active modes, which are found to be distinctly different from those of hydrogenated diamond-like amorphous carbon and defective graphene and thus could be used as a fingerprint for future experimental characterization of the materials. Image 1 [ABSTRACT FROM AUTHOR]

The interfacial thermal transport (ITT) between vertically aligned carbon nanotube (VACNT) arrays and heat sink is the dominant barrier blocking the path towards practical application of VACNT arrays as nano-thermal interface materials (nTIMs). Although developing VACNT arrays with homogeneous heights and larger diameters could lower the thermal contact resistance between the arrays and heat sink (R c), little effect is achieved at present stage. Here, by using Plasma Enhanced Chemical Vapor Deposition approach, we attain DLC/TiN-coated VACNT arrays, which gives up to 50 times reduction in R c from 15 mm2 K/W to 0.3 mm2 K/W. Microscopic morphological analyses confirm that the remarkably expanded contact area brought by coatings can promote the ITT and also retain the high phonon transmission rate within individual CNTs. These novel structures are significantly in favor of fulfilling a nTIM function. It is also intriguing to note that R c is no longer linearly dependent on CNT height variations once CNT diameters become large enough. This indicates that the contact area with heat sink is dominant in influencing R c instead of the surface roughness. The above findings fuel future effort towards industrial realization of high-performance VACNT array-based nTIM and high-efficiency thermal management in microelectronic and nanoenergy fields. Image 1 [ABSTRACT FROM AUTHOR]

Q-carbon, a quenched form of carbon, is a recently discovered carbon structure that has tremendous properties, compatibility, and potential for use in device fabrication and other electronic and mechanical applications. However, the non-equilibrium nature of the synthesis process and a very small window of growth parameters have limited the formation of Q-carbon to only low thermal conductive substrates. This study aims to overcome these limitations through extensive tuning of the parameters of diamond-like-carbon (DLC), the base structure required for the formation of Q-carbon. The as-deposited DLC films demonstrate I D /I G ratios ranging from 0.12 to 1.67, which are obtained through the optimization of laser energy density, rep rate, and deposition temperature during pulsed laser deposition. Utilizing Simulation of Laser Interaction with Materials, pulsed laser annealing (PLA) was used to directly transform the DLC films into Q-carbon while varying the PLA energy density from 0.3 J/cm2 to 1.2 J/cm2. Findings of Q-carbon formation on sapphire using different DLC films assisted in the preparation of a roadmap for overcoming the substrate limitations for Q-carbon formation. Further, Q-carbon is formed on AlN substrates for the direct deposition of diamond films without the requirement of a non-carbon interfacial layer or nanodiamond seeding layer. The large-area and uniform diamond growth on Q-carbon shows well-faceted and five-fold twinned growth with a 70 % improvement in the residual compressive stress of diamond on AlN. Such a method of diamond deposition on AlN provides the opportunity to address the thermal management issues in wide- and ultra-wide bandgap high-power electronic devices. [Display omitted] • The sp2-sp3 carbon composition in the DLC films is entirely tunable using PLD. • Q-carbon is formed on sapphire using different DLC films by controlling laser fluence. • Low thermal conductive substrate limitation of Q-carbon formation has been overcome. • DLC precursor and PLA parameters are crucial for any Q-carbon formation. • Diamond is deposited on AlN using a Q-carbon interlayer for thermal management. [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) films were tribochemically formed from ambient hydrocarbons on the surface of a highly stable nanocrystalline Pt-Au alloy. A sliding contact between an alumina sphere and Pt-Au coated steel exhibited friction coefficients as low as μ = 0.01 after dry sliding in environments containing trace (ppb) organics. Ex situ analysis indicated that the change in friction coefficient was due to the formation of amorphous carbon films, and Raman spectroscopy and elastic recoil analysis showed that these films consist of sp 2 /sp 3 amorphous carbon with as much as 20% hydrogen. Transmission electron microscopy indicated these films had thicknesses exceeding 100 nm, and were enhanced by the incorporation of worn Pt-Au nanoparticles. The result was highly wear-resistant, low-friction DLC/Pt-Au nanocomposites. Atomistic simulations of hydrocarbons under shear between rigid Pt slabs using a reactive force field showed stress-induced changes in bonding through chain scission, a likely route towards the formation of these coatings. This novel demonstration of in situ tribochemical formation of self-lubricating films has significant impact potential in a wide range of engineering applications. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) are among the most promising candidates for large-scale electrical energy storage devices owing to the low cost, abundance, and widespread of sodium resources. However, finding a suitable anode material is a critical necessity to uphold the commercialisation of SIBs. Herein, we report a facile synthesis process to prepare hard carbons derived from date palm biomass consisting of direct pyrolysis of seeds or pulp at different heat treatment temperatures in the range between 800 and 1400 °C. The electrochemical performances of the prepared hard carbons were investigated in SIBs and exhibited high reversible capacity of 300 mAh g −1 and promising initial coulombic efficiency (ICE) of 88.4%, which is the highest ICE reported for hard carbon materials to date. This work is the first to report a successful implementation of date palm as precursor to prepare low cost and high performance hard carbon anode materials for SIBs. [ABSTRACT FROM AUTHOR]

Carbon atom coordination at diamond-like carbon (DLC) film surfaces and in sub-surface regions has been determined nondestructively from high-energy resolved C 1s photoelectron spectra, X-ray induced C KVV Auger electron spectra, and angular-resolved C 1s spectra (ARXPS) aided by maximum entropy method (MEM). The spectra were recorded from hydrogen-free DLC films prepared by a pulsed laser deposition under medium energy Ar ion beam assisted growth. The sp 3 and sp 2 fractions determined from C 1s and C KVV spectra recorded at the normal emission angle differ substantially. This indicates an inhomogeneous depth-resolved distribution of the fractions. The result is validated by the analysis of angular-resolved C 1s spectra using the MEM approach. In-depth reconstructions of the carbon bonding states show that sp 2 coordination is dominant at the surfaces. We found that Ar ion beam assisted growth induces a C sp 2 peak beneath the surface. The peak shifts towards the surface and is growing with Ar ion energy. C sp 3 hybridization is dominant in deeper layers. The in-depth reconstruction is further supported by the depth-dependent mass density determined from the low-loss electron spectra excited at various primary electron energy. The results are discussed within the subplantation model. [ABSTRACT FROM AUTHOR]