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Abstract Modification of micro-particle size during cathodic arc deposition is an important issue for the preparation of hard coatings and nanomaterials. In this work, a coil winding and permanent magnets were applied to adjust the magnetic field of a cathodic arc source. The motion of luminous group spots was investigated through high speed imaging method. The average size of the spots was reduced with the decrease of arc current. When the arc current was higher than 80 A, the size probability distributions of the spots presented as bimodal functions. But it turned into unimodal functions at lower arc currents. By changing the coil current three kinds of spots position distributions were observed, such as centered distribution, intermediate and periphery annulus distributions. Their corresponding spots movements were stochastic, spiral and circular motion dominated. The influence of magnetic field on the spots motion was discussed. Although the average spots size was reduced with the increase of coil current to 2.5 A. Further increasing the coil current leaded to a gathering of spots towards the periphery region of the cathode surface, and an increase of the spots size. Finally, a relationship between the spots size and micro-particles size was established. Highlights • The motion of luminous group spots was recorded through high speed imaging. • Spot position and size distribution was found by kernel density estimation method. • Centered, intermediate and periphery annulus distributions of spots was found. • The influence of magnetic field on spot position and size distribution was analyzed. • A relationship between the spots size and micro-particles size was established. [ABSTRACT FROM AUTHOR]

Discharge behaviors of high-power impulse magnetron sputtering with different targets have been investigated. Distinct current–voltage curves and target current waveforms are observed. Breakdown voltage and the maximum target current show a periodic drop with the increase of atomic number in subgroups and periods. The target current density is found to be mainly affected by the secondary electron emission yield. Thus, its magnitude is unable to directly evaluate the ionization degree of sputtered atoms in high-power impulse magnetron sputtering (HiPIMS) process. In this paper, the interactive influence of secondary electron emission, sputter yield, and ionization energy on the ionization degree of sputtered atoms is discussed based on the analysis of the voltage and current characteristics. As a result, targets can be categorized into three sorts according to the ionization degree: 1) low ionization degree targets, such as Ag and C less than 10%; 2) intermediate ionization degree targets like Cr and Cu with 55% and 35%; 3) Ti, Zr, and Mo targets with the second ionization processes. These results provide institutive operation ranges for the state-of-the-art HiPIMS applications. [ABSTRACT FROM AUTHOR]

Regardless of used metal contact combinations, bulk-limited electrical behaviors were observed in metal/hydrogenated diamond-like carbon (DLC)/metal (MSM) devices through the study of I-V curves and temperature dependence of conductivity. For MSM devices with DLC deposited at a substrate bias of -50 V, the I-V curves exhibited ohmic electrical behaviors in the range of 0–1 V and followed the Poole-Frenkel mechanism in the range of 1–5 V. Moreover, the carrier transport was dominated by the thermally activated process with an activation energy of 0.1576 eV in the temperature range of 160–400 K. The bulk-limited behaviors of MSM devices could be attributed to the relatively high bulk resistance of the DLC layer. This result offers the fundamental insight into DLC based electrical devices and brings forward the concept to fabricate functional carbon based materials. [ABSTRACT FROM AUTHOR]

In this work, we manipulated the trace gradient W incorporation combined with a increment top-layer thickness for the hydrogenated amorphous carbon (a-C:H) coating on thermally sprayed WC-based cermet. The tribocorrosion resistance of the modified a-C:H coating was investigated in terms of structural evolution during friction under 3.5 wt% NaCl solution. Regardless of introduction of gradient W doping, although the a-C:H coating maintained the sp2/sp3 atomic bond structure, the stress reduction and plasticity increase were obtained for coatings. Moreover, the stable open-circuit potential revealed that the tribocorrosion resistance of modified coating was significantly improved, as identified by the quite low wear rate and coefficient of friction at 1.46×10−8 mm3/N·m and COF of 0.067, respectively. Different with the traditional failure of worn-out and pitting corrosion of a-C:H coating in chloride solution, the designed robust interfaces and the functional top-layer enabled the coating to withstand longest sliding distance over 2100 m at heavy contacting pressure of 1.67 GPa. These observations offer the promising strategy to fabricate advanced carbon-based coatings with required extremely strong wear resistance and anticorrosion capability for mechanical components used in harsh marine environment. [Display omitted] • The a-C:H coating with trace gradient W doping was fabricated on WC-based cermet. • Dissolved W atoms in a-C:H benefited stress reduction and plasticity elevation. • The optimized coating showed long-term tribocorrosion resistance over 2100 m. • Robust interface and thick top-layer enabled ultrahigh tribocorrosion durability. [ABSTRACT FROM AUTHOR]

Coatings are utilized to enhance the surface properties of materials. This study aimed to modify the TiN coating with a novel sandwich-zigzag intermediate layer and delve into the intricate damage mechanisms under harsh corrosion-erosion coupling environments. Due to the infiltration of NaCl into the coating and the subsequent formation of TiO 2 , the sandwich-zigzag TiN coatings exhibited a reduction in mechanical behavior and erosion resistance when exposed to salt spray at 550 °C for 50 h. Moreover, the erosion rates of the as-corroded TiN coatings displayed an opposite trend compared to that of the as-deposited coatings, showing that the erosion rate was highest at the erosion angle of 30°. Nevertheless, the presence of the zigzag-TiN intermediate layer benefited the coating by preventing stress accumulation and heterogeneous interface. This ultimately improved the erosion resistance of the coatings by more than 2 times at universal erosion angle compared to that of the substrates under the synergistic effects of corrosion and erosion. [ABSTRACT FROM AUTHOR]

The electrical characteristics and spectroscopic properties have been comprehensively investigated in a DC superimposed high power impulse magnetron sputtering (DC-HiPIMS) deposition system in this paper. The influence of superimposed DC current on the variation of target and substrate current waveforms, active species and electron temperatures with pulse voltages are focused. The peak target currents in DC-HiPIMS are lower than in HiPIMS. The time scales of the two main discharge processes like ionization and gas rarefaction in DC-HiPIMS are analyzed. When the pulse voltage is higher than 600 V, the gas rarefaction effect becomes apparent. Overall, the ionization process is found to be dominant in the initial ∼100 μs during each pulse. The active species of Ar and Cr in DC-HiPIMS are higher than in HiPIMS unless that the pulse voltage reaches 900 V. However, the ionization degree in HiPIMS exceeds that in DC-HiPIMS at around 600 V. The electron temperature calculated by modified Boltzmann plot method based on corona model has a precipitous increase from 0.87 to 25.0 eV in HiPIMS, but varies mildly after the introduction of the superimposed DC current. Additionally, the current from plasma flowing to the substrate is improved when a DC current is superimposed with HiPIMS. [ABSTRACT FROM AUTHOR]

High power impulse magnetron sputtering (HiPIMS) discharge promises high ionization fraction and energetic ions in comparison with dc magnetron sputtering discharge. But acknowledge on the characteristics of HiPIMS plasma in the near-substrate region (substrate vicinity), which is of great importance for film deposition, is still limited. Here, optical emission spectroscopy (OES) combined with the collisional-radiative modelling are developed and used to determine the electron temperature and the number density of neutral sputtered atom for the chromium HiPIMS plasma in substrate vicinity. The OES analysis demonstrated the HiPIMS discharge of Cr sputtering process in low density mode was dominated by the electron impact ionization of argon atoms and excitation of chromium atoms. As the HiPIMS plasma in the substrate vicinity is far from the local thermal equilibrium state, the relative intensities of transition lines to ArI 4p states was used to calculate the electron temperature. Subsequently, the neutral chromium atoms density about 1017 m−3 was reported in the near-substrate region. Our findings have important implications for species generation in low density HiPIMS discharge, with applications in synthesis of dense chromium coatings. [ABSTRACT FROM AUTHOR]

Abstract Grain size, growth morphology, and grain boundary were considered to affect hardness and fracture toughness of hard coatings. An effective approach is currently developed to improve their hardness and toughness via tailoring their architectures through grain boundary control. V-Al-C coatings consisting of variable architectures were prepared by reactive sputtering V 2 AlC target with different CH 4 flow rates in this study. The results indicated that, when the carbon content increased from 37.32 at.% to 71.4 at.%, the microstructure of V-Al-C coatings was tailored to span a wide changes from coarse columnar grain to fibrous columnar grains and finally to nanocomposite structure consisted of the (V, Al)C nanocrystallites and sp2-rich a-C. Especially, the maximum hardness of 28.74 GPa and the excellent toughness with high H/E value of 0.11 were obtained once the coating displayed fibrous columnar structure, such good mechanical properties benefited the lowest wear rate of 2.8 × 10−16 m3/Nm. Instead, the nanocomposite structure showed the lower fracture resistance due to the dominated amorphous carbon matrix. All coatings with nanocomposite structure exhibited low friction coefficient of ∼0.18, which was attributed to the coupling lubrication originated from both V 2 O 5 Magnéli phases and amorphous carbon formed during friction process. The enhanced mechanical and tribological properties were also discussed in terms of the columnar boundaries evolution as a function of carbon content. Graphical abstract Image 1 Highlights • Significant microstructure changes were tuned with varying the content of a-C. • Coating with fibrous columnar grain rendered enhanced mechanical properties. • The influence mechanism of boundaries on mechanical properties was discussed. • Structure zone diagram with C content was established in this study. • The synergistic lubrication of V 2 O 5 Magnéli phase and amorphous C was observed. [ABSTRACT FROM AUTHOR]

In this study, amorphous carbon (a-C) films were modified using different process sequences—H passivation followed by graphitization (a-C@H@G2000K) and graphitization followed by H passivation (a-C@G2000K@H). The friction dependence on the surface H content and the processing priority was comparatively investigated at the atomic scale, with a focus on the coupling mechanism for achieving low friction. The results indicated that the friction properties closely depended on the H content of the contacted a-C surfaces. An appropriate H content significantly improved the friction property through the coupling effect of the lubrication between surface graphitized structures and the repulsion between H atoms, resulting in a rapid decrease in the friction coefficient; however, the graphitization mechanism remained dominant. Excessive H reduced the repulsion between the contacted graphitized structures and hindered the sliding of these structures (shear susceptible), resulting in a slow increase in the friction coefficient. Most importantly, compared with the a-C@H@G2000K systems, the a-C@G2000K@H system exhibited higher effectiveness in reducing the friction coefficient, achieving a lower friction coefficient under the same surface H content; this was attributed not only to the small surface roughness and the low fraction of unsaturated bonds but also to the well stress distribution of the surface H atoms. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Cr 2 AlC MAX phase coating was obtained by hybrid DCMS/HiPIMS technique at 480 °C. • High temperature XRD confirmed that amorphous Cr-Al-C began to crystallize at 570 °C. • The coatings surface temperature increased by ∼122 °C due to ions/atoms bombardment. • The bombardment of Cr and Ar species contributes to 64% and 31% of the energy flux. In this work, highly crystallized Cr 2 AlC MAX phase coatings were successfully fabricated on Ti-6Al-4 V substrate at a temperature as low as 480 ℃, by using a hybrid direct current magnetron sputtering (DCMS)/high power impulse magnetron sputtering (HiPIMS) technique. The focus of the research was to investigate the influence of substrate temperature and bias voltage on the microstructure and mechanical properties of the coating. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images revealed that coatings deposited within the temperature range of 480 ∼530 °C consisted of uniform, densely packed, and randomly oriented grains. Additionally, grazing-incidence X-ray diffraction (GIXRD) and high-resolution transmission electron microscopy (HRTEM) confirmed pronounced crystallinity in the Cr 2 AlC coating at a substrate temperature of 480 °C without utilizing any substrate bias. For reference, an amorphous Cr-Al-C coating was synthesized by hybrid DCMS/HiPIMS on Ti-6A1-4 V substrates at room temperature without intentional heating, followed by high temperature XRD analysis to elucidate its traditional phase evolution route. The results indicated that the amorphous Cr-Al-C phase began to transform to Cr 2 AlC at 570 °C. A continuous increase in Cr 2 AlC crystallinity was observed for temperatures between 570 and 700 °C, with the coating starting to decompose at 800 °C. Subsequently, OES and Langmuir probe techniques were employed to characterize the discharge plasma and establish the relationship between the hybrid DCMS/HiPIMS plasma and the structure of the as-deposited coating. According to our calculation model, it was found that ions/atoms bombardment induced a temperature increase of ∼122 °C on the growing coating surface, with contributions from Cr and Ar ions/atoms accounting for 64 % and 31 % of the total energy flux, respectively. These findings suggest that thermally activated adatom mobility enhancement could significantly benefit high-purity, low-temperature growth of Cr 2 AlC coatings. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Cr-Al-C coatings with different crystallization states were manipulated here. • The partially crystallized Cr-Al-C coatings exhibited the best performance. • Mechanism of conductive corrosion resistance was clarified by HAADF and EPR. • Partially crystallized Cr-Al-C coatings were promising candidate in BPs protection. Metal bipolar plates (BPs) with excellent corrosion resistance and good conductivity have been becoming one of key issues to explore proton exchange membrane fuel cells (PEMFCs). Here, we fabricated the high-performance protective Cr-Al-C coatings on stainless steel 316L using a combined cathodic arc and magnetron sputtering deposition with subsequent annealing. The electrochemical measurements in 0.5 M H 2 SO 4 + 5 ppm HF solution and interfacial contact resistance (ICR) tests indicated that all the coatings exhibited enhanced corrosion resistance and excellent conductivity. As the annealing time increased, enhanced conductivity and corrosion current density were observed. Particularly, the sample annealed at 550 °C for 2 h exhibited the best comprehensive performance in balancing the corrosion current density of 3.02 × 10-7A cm−2 and ICR of 4.5 mΩ cm2 under 140 N cm−2, respectively. The present work provides the alternative strategy to apply the promising Cr-Al-C coatings for high-performance metal BPs used in PEMFCs. [ABSTRACT FROM AUTHOR]

Taking the combination of atomic bond density, in this work, the tetrahedral amorphous carbon (ta-C) layer with high sp3 bond were especially introduced into the sp2-riched graphite-like carbon (GLC) coatings, using a hybrid filtering cathodic arc and magnetron sputtering deposition technique. The focus was elaborated on the electrochemical behavior of coatings against the stimulated chloride solutions for marine applications. Results showed that inserting dense ta-C layer significantly encapsulated the intrinsic pore defects within GLC growth, thereafter enhancing the corrosion resistance remarkably. In particular, the coating porosity was reduced from 10.84 % for pristine GLC system to 3.19 % for GLC with ta-C sealing layer, accompanying with a reduction in corrosion current to 7.8 × 10−9 A/cm2 and an increment in protective efficiency to maximum value of 95.49 %. The small angle X-ray scattering (SAXS) analysis evidenced qualitatively that the coating porosity was suppressed greatly, which were well consisted with the enhanced corrosion resistance of GLC coating with ta-C sealing layer. Furthermore, the balance between pores sealing and interfacial matching could be tailored by controlling the thickness ratio of ta-C and GLC layers, enabling the achievement of both the compact structure and the superior corrosion resistance. These observations offer a new promising strategy to develop the protective coatings for harsh marine environment that required both excellent capability against corrosion and friction with long lifetime. [Display omitted] • GLC/ta-C multilayer coatings were fabricated by a hybrid arc/sputtering deposition system. • Electrochemical behavior was studied in terms of structure changes in coating. • SAXS analysis identified the decrease of pore defects due to dense ta-C layer. • Encapsulating GLC/ta-C multilayer enhanced the corrosion resistance of coating. [ABSTRACT FROM AUTHOR]

The corrosion of metallic Bipolar Plates (BPs) has become a key bottleneck in the practical application of proton exchange membrane fuel cells (PEMFCs). Environmental factors inside the PEMFCs significantly accelerate the degradation of electrical conductivity and durability of metallic BPs. In this work, we investigated the corrosion behavior and conductive properties of amorphous carbon coating (a-C) coated SS316L in a simulated PEMFC environment at various operating temperatures. The results showed that the corrosion current density (I corr) of a-C varied in a range of 2.3–8.7 nA/cm2 when subjected to a temperature range of 40–80 °C. Additionally, the interfacial contact resistance increased from 4.36 to 9.56 mΩ/cm2 with a rise in temperature. The reasons could be ascribed to two aspects. First, the a-C maintained the good chemical stability of sp2/sp3 bonds regardless of temperature changes, favoring remarkable anti-corrosion and good conductivity. Second, the higher temperatures intensified the penetration of corrosive species, accelerating the dissolution process of a-C coated SS316L and leading to substantial corrosion failure. [Display omitted] • a-C coatings were fabricated on SS316L by a hybrid magnetron sputtering technique. • a-C coated SS316L enhanced corrosion resistance and interfacial conductive resistance in a simulated PEMFCs condition. • Increasing operating temperature slightly sacrificed the protective capability of a-C due to dissolution of metallic ions. • Strongly chemical stability of a-C favored long-term durability at high running temperature. [ABSTRACT FROM AUTHOR]

Amorphous carbon (a-C) has been extensively studied as a promising candidate for microelectromechanical system (MEMS) piezoresistive sensors owing to its excellent mechanical properties and sensitivity. However, the semiconductor features of a-C films complicate achieving a high gauge factor (GF) and low temperature coefficient of resistance (TCR). In this study, we introduced micron-scale Al particulates (2.4–5.2 μm average size) by dewetting before a-C deposition, which simultaneously improved the GF and reduced the TCR of the composite structure. An atomic bond analysis revealed that applying the Al particulates favored the formation of sp2, thus reducing the localized surface potential of the a-C film. When the density of the Al particulates reached 15,000/mm2, the GF (36.9) of the a-C film significantly increased by more than 350 %, whereas the TCR decreased as the average size of the Al particulates increased. Furthermore, the composite exhibited typical Schottky contact characteristics and formed a Schottky barrier of 0.43 eV at the Al/a-C contact interface. Carrier transport between the Schottky barriers was achieved by the holes (primary carriers) via tunnelling. These significant piezoresistive properties can be explained by the variation in the Schottky barrier height. [Display omitted] • Micro-scale Al particulates with various sizes and densities were fabricated by dewetting before a-C films. • a-C films combined with Al particulates demonstrated both high GF and low TCR. • Introduction of Al particulates promoted localized formation of C-sp2 content in a-C matrix. • Three-dimensional Mott-type VRH conduction dominated carrier transport in 200–300 K. • Reduction of Schottky contact barrier in Al/a-C interface favored piezoresistive tunnelling related to hole conduction. [ABSTRACT FROM AUTHOR]

In this work, the tribocorrosion performance of hydrogenated and hydrogen-free diamond-like carbon (DLC) coated thermal sprayed WC-based cermet/carbide were investigated comparatively. The results showed that, regardless of hydrogen containing, both coatings demonstrated the improvement of anti-tribocorrosion capability of WC-based cermet in 3.5 wt% NaCl solution, by suppressing the corrosion of Ni-based binder phases. Particularly, the hydrogenated DLC coating presented the better tribocorrosion resistance under low load due to the high hardness and excellent corrosion resistance, but it suffered from the catastrophic delamination and protective degradation at heavy load arisen from the high brittleness and large residual stress. In contrast, the hydrogen-free DLC duplex coating exhibited a low COF of ∼0.06 under higher load (10 N) with long time friction (12 h), because of its gradually shearing characteristic. This work provides theoretical basis and design principles for DLC combinations with remarkable corrosion inhibition used in harsh marines. [Display omitted] • Amorphous carbon coating with and without hydrogen were deposited on WC-based cermet for tribocorrosion comparison. • a-C:H duplex coating presented the excellent tribocorrosion inhibition properties at lower load. • Poor toughness of a-C:H duplex coating caused the catastrophic delamination at higher load in chloride solution. • a-C coated WC cermet behaved the long-term tribocorrosion resistance under heavy friction due to graphitic shearing. [ABSTRACT FROM AUTHOR]

It is important and challenging to develop environment-tolerant stretchable strain sensors under some harsh environments. Here, amorphous carbon (a-C)/Polydimethylsiloxane (PDMS) sensors were fabricated with the direct-current magnetron sputtering technology, their sensing performances were optimized by adjusting the elastic mismatch between the top a-C film and used PDMS substrate, and their application under a simulated marine atmospheric environment was evaluated. The results showed that the combination of low stress a-C and low elastic modulus PDMS was favorable to improve the sensing performance, the optimal sensor exhibited the maximum gauge factor (GF) of 3026.9, large tensile strain range to 50 %, rapid response (loading delay time 92.3 ms and unloading delay time 24.6 ms), as well as high durability (>5000 cycles). After 120 h salt spray test, the sensor was quite stable and can detect various human movements with both high sensitivity and stability, such as wrist pulse, wrist bending, and finger bending. This work pioneers the elastic mismatch strategy for high-performance a-C/PDMS sensors and confirms their great potential in the practical applications under harsh environments. [Display omitted] • a-C/PDMS sensor with gauge factor over 3000 and ε of 50 % was fabricated. • Adjusting mechanical mismatch between a-C and PDMS changed sensing performance. • Low stress a-C and low modulus PDMS resulted in improved sensing performance. • The sensor can detect human motions under simulated marine atmospheric environment. [ABSTRACT FROM AUTHOR]

As an alternative strategy to fabricate high-quality graphene over a large area, metal catalysis has been attempted at elevated temperatures with solid carbon sources. However, graphene was generally fabricated on the surface of metal catalysis layer using amorphous carbon as solid carbon sources. In this study, a thin Al 2 O 3 barrier (1 nm) deposited on an amorphous-C/Ni bilayer stack is demonstrated to enable direct growth of few layer graphene (FLG) identified as 3–4 layers on substrate surface at 700 °C and 800 °C. Moreover, the obtained graphene shows a good transmittance (93%) under the light source of 550 nm. The findings provide a way to directly synthesis FLG on the required substrate at low temperature, which may dramatically broaden the applications range of graphene. • Graphene was directly achieved by annealing ta-C/Ni/Al 2 O 3 multilayered films. • The influence of Al 2 O 3 thickness on the quality of graphene was discussed here. • Graphene mainly formed on substrate surface rather than on catalysis layer surface. • The obtained graphene showed good transmittance under the light source of 550 nm. [ABSTRACT FROM AUTHOR]

In this work, Cu-containing diamond-like carbon (Cu-DLC) films were deposited using a hybrid system combining an anode-layer ion beam carbon source and DC magnetron sputtering, where the Cu content in range of 1.0– 67.7 at.% was controlled by varying sputtering current. The effect of Cu content on the electrical and piezoresistive behavior of films was investigated. Increasing the Cu content from 1.0 to 67.7 at.% enhanced the conductive sp2 phases and caused the more Cu nanoparticulates dispersed uniformly in the insulate sp3 amorphous matrix, which significantly reduced the gauge factor from 5.6 to 1.4. Meantime, the temperature coefficient of resistance demonstrated the increase from −3646 to +294 ppm/K with increasing the temperature from 100 to 350 K, indicating the electrical properties were dominated from typical semiconductor to metal-like behavior. Particularly, increasing Cu content from 20.6 to 67.7 at.% led to the threshold voltage being identified and gradually decreasing. The electrical and piezoresistive behavior of the Cu-DLC films was discussed in terms of the carrier tunneling process between conductive phases distributed in amorphous sp3 matrix. [Display omitted] • Cu-DLC nanocomposite films were deposited by the hybrid plasma process. • Piezoresistive properties and electrical behavior of Cu-DLC films were studied. • Gauge factor was strongly related with content and nanoparticulates size of Cu. • Increasing content of Cu led to transition from tunneling to percolation model. [ABSTRACT FROM AUTHOR]

Cu incorporated diamond-like carbon (Cu-DLC) films were deposited on Si/glass substrate by a hybrid ion beam deposition system, which consists of a direct current (DC) magnetron sputtering of Cu target and a linear ion source. The Cu concentration (from 0.1 to 39.7 at.%) in the Cu-DLC films was controlled by varying the sputtering current. The dependence of residual stress, microstructure and atomic bond structure upon Cu concentration was investigated systematically. Results indicated that the nanoscale Cu particles began to evolve from the carbon matrix in the Cu concentration range of 2.6–7.0 at.%. The residual stress of the Cu-DLC films (less than 0.60 GPa) showed a significant reduction compared with that of the pure carbon film (2.0 GPa). Theoretical calculations revealed that the formation of antibonding between Cu and C and the relaxation of distorted bond angles and bond length accounted for the significant reduction of residual stress caused by Cu incorporation. [ABSTRACT FROM AUTHOR]

The large-scale preparation of non-precious-metal hydrogen evolution reaction (HER) electrodes with remarkable performance was important to the energy crisis. Here, Mo-NiMo/NF (Ni Foam) electrodes were fabricated by homemade high power impulse magnetron sputtering technique with subsequent annealing. The synthesized Mo-NiMo/NF electrodes presented an exceptional electrocatalytic performance with η10 = 71 mV and prominent stability in alkaline aqueous electrolyte for the HER. The experimental data were corroborated by density functional theory (DFT) calculations. The significant catalytic performance for HER active arose from NiMo alloy and the coupling effect between Mo and NiMo alloy. The lowest value on Gibbs free energy of NiMo was − 0.027 eV, very close to the ideal value zero. The adsorption energy of hydrogen atom from heterojunction between Mo and NiMo was − 1.786 eV, which could facilitate Volmer step to further enhance HER activity. More importantly, this synthesis method reported here was scalable, which could provide a valuable strategy to engineer the electrocatalysts with the aim to improve their catalytic activities. • The Mo/NiMo/NF was successfully fabricated through HiPIMS along with vacuum annealing. • The prepared Mo/NiMo/NF cathode exhibited an excellent HER catalytic activity. • DFT calculations showed synergetic effect of NiMo and heterojunction enhanced of HER performance. [ABSTRACT FROM AUTHOR]

Polyether ether ketone (PEEK) is widely used for polymer-metal sliding pairs due to its excellent characteristics such as self-lubrication, and chemical stability. However, PEEK is prone to be worn easily when it comes to friction with metal, which is the most critical limitation for the development of PEEK/metal tribo-pairs. In this study, the tribological properties of silicon and oxygen co-doped amorphous hydrogenated carbon (a- C:H:Si:O) coating on PEEK substrates were focused, where the a-C:H was used for comparison simultaneously. Results revealed that both a-C:H and a-C:H:Si:O coated PEEK displayed a high hardness over 6 GPa and enhanced the tribological resistance. Noted that even the PEEK coated with a-C:H coating behaved the lowest wear rate of 1.82 × 10−7 mm3/Nm, co-doping Si and O improved the adhesion strength between coating and PEEK substrate together with the lubricity. In particular, the a-C:H:Si:O coatings with the concentration of 3.96– 7.49 at. % for Si and 3.07– 6.07 at. % for O showed excellent stability with a wear rate of (2.9 ± 0.4) × 10−7 mm3/Nm, due to the formed compacted tribo-film over the counterpart. The results bring forward a promising strategy to enhance the wear resistance of PEEK/metal sliding components for harsh tribological applications. [Display omitted] • a-C:H:Si:O coatings with highly controllable composition were deposited on PEEK by PECVD. • The a-C:H and a-C:H:Si:O coated PEEK obtained a high hardness over 6 GPa and an improved tribological performance. • Good mechanical properties of a-C:H:Si:O coating and dense tribofilm formed account for the good lubricity. [ABSTRACT FROM AUTHOR]

• The designing idea of coatings was mainly based on grain boundary orientation here. • Sandwich-zigzag TiN coatings were fabricated by tilting magnetron sputtering. • Sandwich-zigzag structure significantly improved solid particle erosion resistance. • The results bring forward a promising strategy to the anti-erosion PVD coatings. Titanium nitride (TiN) hard coatings have been extensively studied as candidates for the purpose of erosion protection of engine blades. However, the traditional monolayer and multilayer TiN coatings are more apt to be worn out due to their high brittleness or low fracture toughness under sand particle impaction. Here, taking the concept of designing grain boundary orientation, we deposited the multilayered sandwich-zigzag TiN coatings (TiN-zigzag coatings) by glancing angle deposition technique. Results showed that the sandwich-zigzag structure significantly improved the erosion resistance of the normal TiN coatings by enhancing energy dissipation at the crack tip and the deflected propagation of cracks in the coatings. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Ni x N on Ni foam was fabricated through plasma-enhanced discharge nitridation. • The prepared Ni x N/NF cathode exhibited an excellent HER catalytic activity. • DFT calculations showed the Ni x N/NF owned the smaller values of ΔG H* for HER. Development of high active and cost-effective non-noble metal productions was urgent for the hydrogen evolution reaction (HER) electrocatalysts in future clean energy devices. Herein, we reported a simple approach to fabrication of Ni x N (x = 3, 4) on Ni foam (NF) through plasma-enhanced discharge nitridation in nitrogen precursors. The synthesized Ni x N/NF cathode exhibited a remarkable electrocatalytic performance and long-term durability for the HER in alkaline condition. In view of the density functional calculations, it was further showed that introduction of N atoms in NF decreased the values of Gibbs free energy, especially the interfacial sites of Ni 4 N-Ni exhibited the lowest value of −0.056 eV for H adsorption–desorption, and enhanced HER catalytic activity of Ni x N/NF. More importantly, the synthesis approach reported here was scalable and eco-friendly, which could be used as to generate the other transition metal nitride for catalytic reaction. [ABSTRACT FROM AUTHOR]

Aiming to study the influence of temperature on the wear mechanism, we fabricated (Cr, V)N coating by cathodic arc ion-plated and conducted tribological experiments at 500–900 °C. The results indicated that there were two tribological behaviors, depending on the temperature. Below 600 °C, the (Cr, V)N coatings exhibited a high friction coefficient, but generated a mild wear because of the slight oxidation. Above 700 °C, the increased oxidation degree reduced adhesion of asperity contacts. However, the wear rate enhanced significantly with the temperature increasing from 700 to 900 °C due to the fast oxidation accompanied by the decrease in both hardness and adhesion strength. • Cr 0.58 V 0.14 N 0.28 coating was successfully fabricated by cathodic arc technique. • The relationship between oxidation, mechanics and friction was analyzed. • The wear mechanism from 500 °C to 900 °C was divided into two stages. • The best tribological properties of the coating were obtained at 700–800 °C. [ABSTRACT FROM AUTHOR]

V-containing solid solution was considered as a promising way to improve the mechanical and tribological properties of hard coatings due to the mechanism of solid solution as well as the induced V-based Magnéli lubricant during friction process. In this work, Cr-V-N coatings with different V contents were prepared on polished cemented carbide and P-type Si (100) wafers by cathodic arc evaporation. The microstructure, mechanical and tribological properties of the coatings with varied V content were discussed. When the content ranged from 0.32 to 31.14 at.%, V entered into the lattice of CrN crystal in the form of solid solution without affecting the coating's phase composition. CrN phase with (111) orientation was formed for all Cr-V-N coatings, and the coating with 31.14 at.% V content showed the weakest crystallinity. The introduction of V still retained the composited coatings with high toughness and excellent adhesion strength of around 100 N on cemented carbide substrates. The maximum elastic modulus and hardness reached up to 438.5 ± 5.3 GPa and 20.0 ± 1.0 GPa, respectively, with V content at 16.55 at.%. Tribological tests at room temperature demonstrated that the friction coefficient of Cr-V-N coatings was relatively low, which was between 0.26 and 0.36. The wear rate was in the order of magnitude of 10−7 mm3N−1 m−1, and the lowest wear rate was 2.5 × 10−7 mm3N−1 m−1 with V content at 0.32 at.%. The friction coefficient and wear rate both increased with the increase of V content. The wear rate of the coatings with high V content (31.14 at.%) was almost four times higher than that of low V content (0.32 at.%) coatings. • An excess of V content altered the way the coating grows. • Solid solution strengthening conferred good mechanical and frictional properties. • The surface roughness and crystallinity influenced the friction coefficient. • Limited tribo-chemical reaction restricted the improvement of friction performance. [ABSTRACT FROM AUTHOR]

The magnetron sputtering deposition of CrN coatings is environmental friendliness and has high surface gloss. Therefore it is a promising alternative to the electroplating deposition of Cr coatings as an effective method to metallize of ABS materials. Nevertheless, the coatings on the polymers suffered from cracks' initiation during temperature alternating processes, resulting in the degradation of decoration and protection function. In this work, we proposed a new application of the HiPIMS CrN coating for as the surface metallization method for ABS, and investigated its properties in comparison with the DCMS method. Based on the electric and spectroscopic characteristics of these two kinds of magnetron sputtering discharge and the resultant coating structures, the corrosion resistance, mechanical properties, as well as the weatherability of the coatings were studied and discussed. Results revealed that the HiPIMS coating had a dense nanocrystalline CrN (200) phase structure, rather than the loose amorphous/nanocrystalline composite structure of the DCMS CrN coating. Consequently, the HiPIMS CrN coating demonstrated superior corrosion resistance, mechanical properties, and meanwhile avoided the crack problem on ABS substrates. Finally, we developed a new CrN coating by HiPIMS as the protective coating for the purpose of replacing the electroplating Cr coating on polymers. • A new application of HiPIMS CrN coating for ABS surface metallization is proposed. • HiPIMS promotes forming dense nanocrystalline CrN by higher target ionization. • HiPIMS CrN presents excellent corrosion resistance and mechanical properties. • Cracking problem of CrN coatings on polymer surface is solved. [ABSTRACT FROM AUTHOR]

• The design, fabrication and testing methods of amorphous carbon force sensor were systematically studied. • The sensitivity was 9.8 μV/V/mN and non-linearity was about 2.0% FS, while it also showed a good repeatability. • In-situ depositing serious amorphous carbon films by simple, economic and green DC sputtering technic. • The piezo-resistive mechanism study result supported the thick film resistors (TFRs) theory well. The rapid growing demand of micro-electromechanical system (MEMS) sensors brings an urgent need for high performance and low cost sensitive materials. In this work, amorphous carbon (a-C) film was in-situ deposited on silicon substrate as strain sensitive component using economical direct current (DC) magnetron sputtering process and the a-C sensor was systematically designed, fabricated and tested. By adjusting the negative bias voltage in the range of 0–400 V, the gauge factor (GF) of the a-C film was adjusted within the range of 3.3–6.9. What's more, the film's sp2 cluster size played an important role in their piezo-resistive performance and conductivity, which illustrated the thick-film resistors (TFRs) theory. Additionally, CAFM results also supported the applying of TFRs theory in this work. Benefiting from the outstanding performance of a-C film, the MEMS force sensor, consisted a Wheatstone full-bridge with four a-C piezo-resistors, had a sensitivity of 9.8 μV/V/mN and non-linearity about 2.0% FS in the testing range of 0–210 mN, while it also showed a good repeatability. These investigations provided deeper insight into the piezo-resistive behavior of a-C film and contributed to the development of high performance and more economical sensitive materials for MEMS sensors. [ABSTRACT FROM AUTHOR]

• a-C films displayed strong light absorption in the ultraviolet and visible regions. • a-C films showed semiconductor behaviors with temperature range from 5 to 350 K. • Opto-electrical properties of a-C were decided by sp2/sp3 ratio and sp2 cluster. Amorphous carbon films have been considered as strongly promising semiconductor materials, due to their superior mechanical properties, specific bond structures, as well as facile deposition over large area with device integrated processes. To figure out the effect of sp2/sp3 ratio and size of sp2 clusters on opto-electrical behavior, we fabricated a series of H-free amorphous carbon (a-C) films by magnetron sputtering with a controllable deposition temperature from 30 to 400 °C. Result showed that all the films displayed a strong light absorption in the ultraviolet and visible regions, where the transmittance was less than 5% in the wavelength range of 200–750 nm, demonstrating the typical semiconductor behavior in temperature from 5 to 350 K, exhibiting a lower resistivity at higher temperature. In addition, their transmittance, optical bandgap, resistivity and activation energy showed similar tendency with increasing deposition temperature, which was discussed in terms of the evolution of sp2/sp3 ratio and sp2 cluster in the a-C films. These studies provide a new route to tune optical and electrical properties of a-C films for their opto-electrical applications. [ABSTRACT FROM AUTHOR]