查看更多>>摘要：? 2022Superhydrophobic surfaces are an effective measure to achieve drag reduction in the process of water transmission. A novel superhydrophobic F and Si incorporated DLC (F&Si-DLC) film with a micro/nanoscale structure was deposited on the internal surface of 304SS pipe by reducing the pumping speed (increasing the pressure), which combined hollow cathode discharge and plasma immersion implantation. The results indicate that the water contact angle and rolling angle of the as-deposited F&Si-DLC film are 151.6° and 9.4°, respectively. The water flow shed through the superhydrophobic F&Si-DLC film surface without adhesion and no sign of wetting was observed on the surface of the F&Si-DLC film, exhibiting a good and stable superhydrophobicity. Besides, the superhydrophobic F&Si-DLC film presents better mechanical properties (hardness ~ 7.1 GPa) than traditional organic superhydrophobic film. Compared with the pure DLC film, the DLC film containing only F atoms (F-DLC), and the DLC film containing only Si atoms (Si-DLC) deposited on the inner surface of the pipe under the same conditions, it is found that the incorporation of F or Si element is an effective way to reduce the surface energy of DLC films and improve their hydrophobicity. However, the F&Si-DLC film deposition a constant pressure (F&Si-DLC (one)) does not exhibit superhydrophobic properties (the water contact angle of 90°). Therefore, an important reason for obtaining superhydrophobic F&Si-DLC films by reducing the pressure is to generate more micro/nanoscale clusters, in other words, to obtain a rough surface with micro/nanoscale. The as-deposited superhydrophobic F&Si-DLC film offers the possibility of reducing drag in water transmission.
查看更多>>摘要：? 2022The appearance of coexisting ferromagnetic and superconductive phenomena in graphite?sulfur and amorphous carbon?sulfur composites has recently attracted an important attention. In this work we propose a novel re-investigation of the carbon?sulfur doping mechanism performed by employing carbon nanotube networks (cm-scale buckypapers) and graphene-oxide films as host-materials. In the buckypaper-case, the presence of multiple sulfidation processes involving formation of 1) carbon?sulfur and 2) metal-sulfide phases was demonstrated. Presence of carbon?sulfur bonding was identified by employing both Raman spectroscopy and X-ray photoelectron spectroscopy. The conductive and magnetic properties of the sulfur-rich areas within the buckypaper were also investigated. An enhanced carbon?sulfur bonding was then identified in sulfur-doped graphene-oxide films. In this latter case we demonstrate an almost complete annihilation of ferromagnetic-signals. ESR-spectroscopy of this second-type of system revealed the appearance of a paramagnetic transition for g ~ 2.08 at T ~ 77 K, possibly originating from the carbon?sulfur bonding. A weak enhancement in the diamagnetic component could be interestingly detected below T ~ 60 K as a consequence of sulfur doping, after subtraction of the percolative ferromagnetic signals.
查看更多>>摘要：? 2022The objective of this work was to understand the textural properties of porous carbon prepared under air conditions and simultaneously construct pore surface roughness/textural properties relationships. A controlled variable method was used for performing single-factor tests. Subsequently, the pore surface roughness of coconut shell-derived porous carbons (CSPCs) was calculated and correlated with their textural properties. Within a range, CSPC obtained under air conditions had a higher specific surface area as compared to CSPC prepared under N2, CO2, and vacuum conditions. With increasing the final temperature or holding time, the pore structure of CSPC first underwent a full development stage and then underwent an over-developed stage. Meanwhile, the optimized final temperature and holding time, i.e., 850 °C and 90 min, were determined. Hysteresis loops on N2 adsorption/desorption isotherms affect pore surface roughness. The correlation coefficient (R2) value (0.92) between mesopore volume (Vmeso) and pore surface roughness was the highest, followed by the R2 value (0.91) between mesopore surface area and pore surface roughness, and the R2 value (0.85) between macropore volume (Vmacro) and pore surface roughness. Therefore, the pore surface roughness depends not only on the Vmeso but also on the mesopore surface area, Vmacro, and total pore volume (Vt).
查看更多>>摘要：? 2022 Elsevier B.V.Laser-induced graphene (LIG) is a foam-like porous material consisting of few-layer graphene obtained by laser irradiation of a wide range of carbon-containing substrates. Among these, the ability to synthesize LIG from paper and other cellulose-related materials is particularly exciting, as it opens the door to a wide assortment of potential applications in the form of low-cost, flexible, and biodegradable devices. Here, the synthesis of this material, dubbed paper-LIG, on different types of filter papers and xylan biopolymer is discussed. In particular, we report the formation of paper-LIG by single-step irradiation, providing an improvement over the conventional multiple lasing approach and giving an explanation of the conditions that allow this simplified synthesis. All the relevant process parameters are covered, assessing their effect on the resulting electrical properties, structure, and morphology. Additionally, we demonstrate the application of LIG obtained from xylan, an abundant and often underutilized biopolymer, for temperature sensing. These results provide a better understanding of the conditions required for the synthesis of highly conductive LIG from paper and related materials, paving the way for its application, with reduced cost and low environmental impact, in fields ranging from biomonitoring to consumer electronics.
查看更多>>摘要：? 2022 Elsevier B.V.This work conducted a density functional theory study on CO, C2H2, and CH4 gases adsorption on transition metal oxides (NiO, SnO2, In2O3) modified graphene monolayer. The application prospects of NiO/SnO2/In2O3 modified graphene monolayer in adsorbents and gas-sensitive materials are discussed from the aspects of modified model, band structure, synergistic effect, adsorption energy, adsorption distance, adsorption structure, electron transfer, and density of state. The three transition metal oxides are modified at three optimal positions on the graphene monolayer, which improves the conductivity of the intrinsic graphene monolayer. NiO-graphene monolayer has the largest adsorption energy for CO gas by obvious chemical interaction. The introduction of transition metal oxides on the intrinsic graphene monolayer significantly enhances the chemical interaction between the graphene monolayer and C2H2 gas. Still, it cannot increase the adsorption energy of CH4 gas. In addition, the electronic properties, desorption performance, and comparative process analysis of all adsorption structures were also studied to evaluate their potential applications for specific gas detection and removal in oil-immersed power transformers.
查看更多>>摘要：? 2022 Elsevier B.V.Chemical vapor deposition of pyrolytic carbon (PyC) onto carbon nanotube (CNT) surfaces by hydrocarbon pyrolysis can thicken the nanotube diameter until the desirable size. Vapor-induced thickening of CNTs may require no metal catalysts because the CNT-templated growth can easily convert PyC deposits into epitaxial graphene shells. However, little work has been done on the kinetics of the vapor-induced CNT thickening process during the non-catalytic pyrolysis. In this study, we discuss the growth mechanism of epitaxial PyC layers on CNT surfaces achieved by the low-pressure (≤1.5 kPa) pyrolysis of ethylene, which is distinct from previous studies using much higher gas pressures (4–100 kPa) for the PyC deposition. The average thickness of deposited PyC layers is calculated by analyzing the transmission electron microscopy images of PyC-coated CNTs. The crystallinity of PyC-coated CNTs is evaluated by Raman spectroscopy and X-ray diffraction. The thickness of PyC layers on CNT surfaces can be adjusted by simply changing the growth time under typical pyrolysis parameters (800 °C-1.5 kPa of ethylene). We find a two-stage nonlinear behavior to describe the growth kinetics of PyC layers, indicating that the radial growth rate of PyC layers can be influenced by the number of surface active sites. This study reveals the self-assembly mechanism of graphitic layers on the CNT template, which is expected to promote the diameter-controlled synthesis of CNTs.
查看更多>>摘要：? 2022 Elsevier B.V.Creation of memristors is one of the perspective directions of the development of nonvolatile memory in portable devices and neuromorphic systems. In recent years, carbon nanostructures have established themselves as promising materials for creating memristors. This paper presents the results of studies of resistive switching of strained carbon nanotube (CNT) under atmospheric and vacuum conditions. It is shown that the ratio of resistances in high and low resistance states (HRS/LRS) of strained CNTs increases 10 times under a vacuum. This fact makes it possible to exclude the influence of adsorption processes on the switching process of strained CNT. The effect of the upper electrode material (graphite, platinum and tungsten) on the HRS/LRS ratio of memristor structure based on strained CNT has been established. It is shown that tungsten is the most suitable material due to the similar values of the work function a tungsten and a multi-walled CNT. A prototype of a memristor based on strained CNT 35 nm in diameter and 747 nm in length has been made. The repeatable resistive switching of the breadboard over 500 cycles with the ratio HRS/LRS ? 2 · 102 has been shown. The obtained results represent the basis for the creation of memristors based on carbon nanotubes.
查看更多>>摘要：? 2022 Elsevier B.V.This paper reports the results obtained from the deposition of diamond-like carbon (DLC) films on glass substrates by gas injection magnetron sputtering method. The conducted studies aimed to evaluate if the plasma discharge that is generated by varying the proportions of neon?argon (Ne?Ar) gases during pulsed injections (0%–100%) would promote the synthesis of DLC films with desirable sp3 phase by means of electron impact-induced plasma interactions. The obtained DLC films showed the presence of sp3 (C[sbnd]C) hybridized bonds along the Gaussian distribution curve, which revealed that a maximum sp3 content in the range of 32%–45% was obtained along the 40% injection of Ne gas, based on the analysis of the C1s core-level spectra and Raman spectroscopy. A 25% gain in hardness (H) and resistance to cracking (H3/E2) were also observed in the sp3-rich DLC sample (24.1 ± 4 GPa and 0.29 ± 0.04), thus promoting its use in various nanomechanical systems. The change in the sp3/sp2 fraction ratio, demonstrated in this research, corresponded well to a calculated model of graded optical bandgap in the range from 0.53 to 3.01 eV. However, to further minimize the parasitic reflectance from a significant share of sp2 (C=C) domains, thin titanium dioxide (TiO2) (8–36 nm) layers were deposited on the DLC surface, which provided maximum antireflective effect due to interference shift. A significant increase in visible–near-infrared transmittance (up to 87%) was observed as a result of such an interference in DLC/TIO2 bilayers. Our results have practical applications and aid in the design of functional nanocoating structures which are tremendously favored and required to improve the toughness of commercially available glass protectors in hostile environmental conditions.
查看更多>>摘要：? 2022 Elsevier B.V.In the present work, methods of depositing gold particles of different morphologies on the facets of synthetic diamond microcrystals have been proposed. When diamond crystals with silver particles selectively deposited on the {100} facets are treated by chloroauric acid HAuCl4 solution, partial galvanic replacement of silver by gold leads to the formation of hollow porous hemispheres of an Ag–Au alloy. Upon annealing of the diamond crystals with particles, in which silver was partially replaced by gold, an Ag–Au solid solution forms on the {100} facets. Selective dissolution of silver from the Ag–Au solid solution results in the formation of nanoporous gold via a dealloying process. Gold particles can also be formed by sputtering gold on the surface of the diamond crystals with silver particles adhered to the {100} facets, annealing the modified crystals and dealloying. In that case, gold particles are found on all facets of diamond. However, the morphological features of the particles depend on the crystallographic orientation of the facet. Nanoporous gold particles are found only on the {100} facets of diamond.
查看更多>>摘要：? 2022In this study, Al-doped diamond-like carbon (DLC) films were prepared using a hybrid deposition technique combining high-power impulse magnetron sputtering and pulsed direct current magnetron sputtering. The influence of bias voltage effects on the microstructure and properties of films were investigated. The results showed that the deposition rate of the films decreased after increasing the bias voltage, and the Al content also slightly decreased in the films. All films exhibited a cauliflower-like surface morphology, which was independent of the bias voltage. The maximum values of sp2/sp3 and ID/IG were achieved without bias voltage; the ratios then monotonously decreased with an increase in the bias voltage from ?100 V to ?400 V, which indicates that the content of sp3-C bonds has improved in films. The mechanical properties and the wettability of the films were also evaluated. The results revealed that the hardness, elastic modulus and residual stress of the films increased with increasing bias voltage. The highest hardness occurred at ?400 V, and the high sp3-C fraction and residual stress were beneficial to the hardness enhancement. All films exhibited a water contact angle greater than 100°, implying that the film possessed good hydrophobic performance. Specifically, when deposited at ?300 V, the film presented a combination of superior properties, namely, a relatively high hardness and strong hydrophobic behavior.
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