Transition metal dichalcogenides (TMDs) are easily oxidized in the humid atmosphere, leading to a decrease in their lubricating properties and limiting their application. In this study, a MoS
2
/WS
2
...multilayer film doped with tantalum (MoS
2
/WS
2
-Ta) is fabricated by magnetron sputtering to improve the corrosion and oxidation resistance of TMDs. Results show that doping of Ta makes the structure of the MoS
2
/WS
2
multilayer film more compact, and the MoS
2
and WS
2
crystals exhibit a stronger (0002) preferred orientation than that of un-doped sample. Such compact structure and (0002) preferred orientation of MoS
2
/WS
2
-Ta can realize a high corrosion resistance,
i.e.
, a more positive corrosion potential and a lower corrosion current density in comparison with the MoS
2
/WS
2
multilayer. Furthermore, the friction properties of MoS
2
/WS
2
multilayer film doped with 1.1 at% of Ta are improved remarkably under both of high temperature (370 °C in air) and vacuum conditions, the result is attributed to its high mechanical properties and (0002) preferred orientation. In a word, the combination of multilayer structure and doping of Ta into the films is a promising approach to accurately design the TMDs toward a wide temperature range and environmentally adaptive lubricants.
Graphical abstract
Molybdenum disulfide (MoS
2
) films are widely deployed in industrial applications owing to their inherent interlayer slip characteristics, offering energy consumption savings and prolonged ...mechanical part performance. Nevertheless, their practical utility is limited by environmental constraints and the limitations of preparation techniques, which hinder the attainment of robust superlubricity (friction coefficient < 0.01). Herein, through magnetron sputtering technology, we synthesize a core-shell-like nanocomposite composed of MoS
2
nanosheets encapsulating B
4
C. The core-shell-like structure enables the resulting films to preferentially grow crystalline MoS
2
, providing them with outstanding mechanical properties and efficient lubrication over a wide range of temperatures. Remarkably, such film achieves robust macroscale superlubricity and an ultralow wear rate (1.7 × 10
−8
mm
3
N
−1
m
−1
) under high contact stress in a mild vacuum environment. This noteworthy outcome is primarily attributable to the self- segmentation of the macroscale contact interface during the friction process, involving: (1) a large amount of wear debris is embedded into the wear track to create extensive micro-sized asperities; (2) a nanolayer of amorphous carbon enriched with oxide nanoparticles is formed on the uppermost part of these asperities; (3) numerous incommensurate nanocontacts comprising nanoparticles and highly oriented MoS
2
nanosheets are established, culminating in the achievement of robust superlubricity. Our pioneering design, coupled with the elucidation of the underlying superlubricity mechanism, holds significant promise for advancing the development of robust and high performance lubricants.
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•The wear rates were in inversely proportional to the friction coefficients of different tribo-pairs in helium at 150 °C.•All the tribo-pairs exhibited steady curves of ultralow ...friction coefficient in air at the same temperature.•Hertz analysis was used to further elucidate the frictional mechanism of DLC film under helium and air conditions.
The tribological behaviors of hydrogenated DLC film sliding against Al2O3, ZrO2, Si3N4 and WC mating balls have been comparatively investigated by a ball-on-disk tribometer at 150 °C under helium and air (RH = 6%) conditions. The results showed that the mating material influenced the friction and wear behavior remarkably in helium atmosphere, where the wear rates were in inversely proportional to the friction coefficients (COF) of those tribo-pairs. Compared to the tests in helium, the tribological performance of DLC film significantly improved in air. Scanning electron microscope (SEM) and Raman spectroscopy were performed to study the friction behavior and wear mechanism of the film under different conditions. It suggested that the severe abrasion was caused by the strong interaction between the tribo-pairs in helium atmosphere at 150 °C, whereas the sufficient passivation of the dangling bonds of carbon atoms at sliding interface by chemically active molecules, such as water and oxygen, dominated the ultralow friction under air condition. Meanwhile, Hertz analysis was used to further elucidate the frictional mechanism of DLC film under helium and air conditions. It showed that the coefficient of friction was consistent with the varied tendency of the contact radius, namely, higher friction coefficient corresponded to the larger contact radius, which was the same with the relationship between the wear rate and the contact pressure. All of the results made better understanding of the essential mechanism of hydrogenated DLC film sliding against different pairs, which were able to guide the further application of DLC film in the industrial fields of helium atmosphere.
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•BN nanofilms effectively improve anti-oxidation characteristic in AO simulation environment.•The multilayer BN nanofilms coated Cu foils show better resistance to AO than monolayer ...BN thin films and bare Cu.•Calculation results reveal AO is easily absorbed on BN film surface and stops diffusion leading no contacting with Cu.
Boron nitride (BN) nanofilm, as a structural analogue of graphene, is one of the most promising candidates for an effective anti-oxidation barrier to protect the underlying metal. Herein, the oxidation resistance of monolayer and multilayer BN nanofilms against space atomic oxygen (AO) irradiation is studied systematically. Experimental results reveal that multilayer BN coated Cu foils exhibit superior oxidation resistance against AO irradiation than that of monolayer BN coated ones and bare Cu, resulting from the high impermeability of multilayer films. Density functional theory calculations and molecular dynamics simulations indicate that AO can be absorbed spontaneously on the surface of BN plane and can't move arbitrarily. However, AO can still damage monolayer BN film after long time irradiation, leading to the oxidation of underneath Cu. In comparison to monolayer BN, the multilayer designing of BN may adsorb AO on the top layer, and increases the diffusion difficulties of AO passing layers, which enhances the barrier performance against AO. These results prove that multilayer BN have an important promising implication as one oxidation-inhibiting barrier to anti-AO in space.
Polyurea (PU) materials are widely used in civil and military fields owing to their excellent weather, wear and corrosion resistance, impact resistance and energy absorption ability. In this study, ...polyurea nanocomposites integrated with polydopamine functionalized graphene oxide (GO@PDA) were reported. The functionalization of graphene oxide (GO) with polydopamine was achieved under mild conditions to optimize the dispersion and interfacial compatibility of GO within the PU matrix, thereby reinforcing the mechanical properties of PU materials. The quasi-static and dynamic compressive behaviors of PU nanocomposites under various strain rates (0.001–7000 s−1) were comprehensively investigated through a universal testing machine and split Hopkinson pressure bar (SHPB), respectively. Results revealed a significant enhancement in the strain-rate sensitivity, flow strength, yield strength, and strain energy density with the increasing strain rate and GO@PDA content. Particularly, at a strain rate of 7000 s−1, GO@PDA1.0%/PU nanocomposite exhibited a remarkable increase of 33% and 54% in flow strength and yield strength, respectively. This remarable enhancement was closely related with the effective dispersion and superior interfacial compatibility between GO@PDA and PU matrix. Eventually, to offer a comprehensive understanding of the mechanical behavior of PU nanocomposites, a visco-hyperelastic intrinsic model was employed to accurately capture the mechanical response under various strain rates.
•The modification of the GO with PDA improves the compatibility between GO and EP.•EIS results show that the GO-PDA/EP has longer service life than blank EP.•SVET results imply that GO-PDA/EP with ...damages has better corrosion resistance.
This study reports an eco-friendly water-borne epoxy (EP) with enhanced corrosion protection performance by embedding graphene oxide (GO). For this purpose, the dispersion of the GO in ethanol is improved by modifying the GO nanosheets with hydrophilic dopamine (DA), owing to the π-π interactions between the GO and self-polymerized polydopamine (PDA) as well as the covalent bonding between DA and GO. Results obtained from transmittance electron microscopy (TEM), scanning probe microscopy (SPM) Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, UV–vis absorbance spectroscopy and X-ray photoelectron spectroscopy (XPS) reveal the successful modification of PDA on the surface of GO nanosheets. Besides, the GO/EP and GO-PDA/EP coatings are applied on the steel substrates and their corrosion protection performance is investigated via electrochemical measurements, scanning electron microscopy (SEM) and scanning vibration electrochemical technology (SVET). Results demonstrate that inclusion of well-dispersed GO-PDA nanosheets leads to the remarkable improvement in the corrosion protection performance of water-borne EP coating.
Thinking about Development of Blockchain Junyan, Han; Siming, Ren; Weichao, Liu
China Economic Transition = Dangdai Zhongguo Jingji Zhuanxing Yanjiu,
2020, 20200101, Volume:
3, Issue:
2
Journal Article
The global enthusiasm for blockchain was sparked by Bitcoin, which has been the most successful application of this technology to date. Satoshi Nakamoto's article, Bitcoin: A Peer-to-Peer Electronic ...Cash System, although specific to Bitcoin, remains the leading literature for the study of blockchain technology. This article therefore uses Nakamoto's paper as the theoretical basis, and Bitcoin as a case study, for a new analysis in the nature of blockchain.
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Carbon steel is the most widely used engineering material, and its corrosion is one of the main areas of concern in many industries. The most practical approach to control this ...problem is to use corrosion inhibitors. Currently, because of their good water solubility, excellent chemical stability, low cost and nontoxic features, carbon dots (CDs), especially heteroatom-doped CDs, have been developed as green corrosion inhibitors, but the corrosion inhibition efficiency and underlying mechanisms of single- or dual-element doping have not yet been accurately compared and analyzed. Inspired by this, eco-friendly nitrogen-doped and nitrogen, sulfur codoped CDs (N-CDs and N,S-CDs) are prepared via a one-step hydrothermal process, and a comparative study on their inhibition performance for carbon steel corrosion in strong acidic solution is performed. The results show that both N-CDs and N,S-CDs can restrain the corrosion of carbon steel, and their inhibition efficiency increases with increasing concentration and immersion time, reaching approximately 87.9% (N-CDs) and 96.4% (N,S-CDs) at 200 ppm after 1 h of immersion. Molecular dynamics simulation indicates that the strong interaction ability between N,S-CDs and the Fe substrate leads to higher corrosion inhibition performance than the single N doping case, benefiting from the multi-anchor adsorption of N,S-CDs on carbon steel in a strong acidic solution. Therefore, the facile preparation, eco-friendliness and high corrosion inhibition performance of N,S-CDs will provide a new approach for designing highly efficient carbon dots and broadening the application of carbon dots in the corrosion field.
•Corrosion of Q235 carbon steel in 1 M HCl solution is inhibited significantly by NCDs (p-CDs and o-CDs).•The inhibition efficiency is strongly dependent on the concentration of NCDs.•The adsorption ...of NCDs involves both chemisorption and physisorption.
Nitrogen doped carbon dots (NCDs) were synthesized and used for inhibiting the corrosion of Q235 carbon steel in hydrochloric acid (HCl) solution. Inhibition effectiveness in short- and long-term immersion was examined using electrochemical measurements, weight loss and surface analysis. Results revealed the inhibition efficiency was improved significantly after adding NCDs and strongly dependent on the concentration of NCDs. SVET results showed that the sample immersed in HCl solution with NCDs showed lower anodic current density mapping than that in blank HCl solution. According to the data extracted from the Langmuir adsorption, the absorption of NCDs involved both chemisorption and physisorption.
Inspired by the high water solubility and low cytotoxicity of N doped carbon dots (CDs) prepared by using antibiotic aminosalicylic acid (ASA) as precursor, we anticipate that these CDs may possess ...an excellent protective ability to inhibit the corrosion of carbon steel in aggressive solutions owing to its special structure. Therefore, the investigation on the inhibiting effect of CDs as eco-friendly corrosion inhibitor for Q235 carbon steel corrosion in 1 M HCl solution is first reported. Electrochemical techniques, weight loss, morphological and elements characterization are combined to investigate the inhibiting effect and corrosion mechanism. The results show that corrosion of Q235 carbon steel in 1 M HCl solution is significantly inhibited by the addition of CDs, which is attributed to the formation of CDs adsorption film, and the adsorption of CDs obeys a Langmuir adsorption isotherm.
Besides, the protection efficiency increases with increasing concentration of CDs and prolonged immersion time, and reaches equilibrium eventually.
•N doped CDs have the unique structure and low toxicity.•N doped CDs can inhibit the corrosion of Q235 carbon steel in HCl solution.•The reason for this inhibition is due to the formation of CDs adsorption film.•The adsorption of CDs obeys a Langmuir adsorption isotherm.
