查看更多>>摘要：? 2022 Elsevier B.V.Graphitization of porous carbon at low temperature has always been an extremely challenging problem without destroying its porous structure. In this study, the porous graphite carbon is successfully prepared through sawdust as a carbon source and bimetal nickel and molybdenum as the catalyst at the temperature of 750 °C. The results show that the graphitization degree of catalyzed porous carbon by bimetallic nickel and molybdenum increased by 9.4% compared with that of porous carbon prepared without catalyst. Nitrogen adsorption and desorption analysis show that the structure of the porous graphite carbon is dominated by 1–2 nm micropores with few mesopores. The porous graphite carbon exhibits a high specific capacitance of 267 F g?1 at 1 A g?1. The rate performance of such porous graphite carbon reaches 77.2% at 10 A g?1, which increased by 34.7% compared with that of the porous carbon obtained by the metal-free catalyst. The assembled symmetric supercapacitor displays a remarkable energy density of 19.8 Wh kg?1 at a power density of 452.9 W kg?1 in Na2SO4 electrolyte. Additionally, the device exhibits a long-term cycling stability with a 94.8% retention rate after 10,000 cycles. This study not only provides a new route for preparing porous graphitized carbon without destroying the porous structure, also gives a new choice for preparing porous carbon with high rate performance as an electrode of supercapacitor.
查看更多>>摘要：? 2022 Elsevier B.V.We have investigated the electronic and optical properties of ultra-small (3,3), (4,4) and (5,5) armchair single walled nanotubes carbon (C-SWNTs) and boron nitride (BN-SWNTs) using three density functional methods of different categories, namely, PBE, TB-mBJ and hybrid functional YS-PBE0. A density functional theory (DFT) within the full-potential linearized augmented-plane wave (FP-LAPW) method, was used to study the structures, electronic and optical properties of these nanotubes. The calculation of optical properties has been performed under electric fields polarized both parallel and perpendicular with respect to the nanotube axis. The results show that the hybrid functional YS-PBE0 perform the best for calculations of band gap of BN-SWNTs (5.27–5.54 eV), while for C-SWNTs the PBE and TB-mBJ functionals obtain band gap range (0.16–0.28 eV) with smaller errors compared to experimental values and confirming the semiconducting behavior of the studied C-SWNTs. The dielectric function is anisotropic for all tubes and is larger in the parallel direction. The results show also that for C-SWNTs, the static refractive index is higher than those of BN-SWNTs and it has an inverse correlation with the C-SWNTs diameter. This proves that for optoelectronic applications, it is improve to use the BN-SWNTs doped than intrinsic.
查看更多>>摘要：? 2022 Elsevier B.V.In this paper, the WC(001)/diamond(111) interface properties are calculated by the first principles considering the C- and W-terminated WC(001) surfaces, the WC(001)/diamond(111) calculation model is established. Analyze its adhesion work, interface energy, electron density difference, Mulliken population and density of states. The results showed that: from the interface energy, the surface energy of the C-terminated WC(001) structure is always higher than that of the W-terminated, which the W-terminated WC(001) structure is more stable than the C-terminated; from the adhesion work, the C-terminated WC(001)/diamond (111) surface configuration has the larger adhesion work and smaller interface energy; according to the electron density difference, Mulliken population and density of states, the C[sbnd]C bond of the C-terminated WC (001) interface is attributed to the hybridization of C-2p orbital and has a strong covalent bond, while the interface W[sbnd]C bond of the W-terminated interface comes from the hybridization of C-2p orbital and W-3d orbital and has a mixed bond (ionic bond and weak covalent bond).
查看更多>>摘要：? 2022 Elsevier B.V.A 3D Kinetic Monte-Carlo (KMC) model is implemented and used to simulate the growth of (1 0 0)-oriented diamond films. The model considers four processes: adsorption and desorption of CH3 radicals, etching of carbon atoms and migration of adsorbed radicals. The atomic structure of diamond is taken into account including the formation of dimer rows on the surface. The model correctly reproduces the step-flow growth mechanism of diamond (1 0 0) surfaces and the obtained growth rates are close to experimental data. The propagation of the steps shows a clear anisotropy. Steps are usually two atomic layers high but step bunching can be observed in presence of defects. The model thus can be used as a predictive tool to obtain growth rates and to understand the effect of atomic interactions on the film morphology.
查看更多>>摘要：? 2022For tribological applications, adding Si or W to hydrogen-free a-C or hydrogenated a-C:H is highly beneficial to tailor the film properties. Hence, a direct comparison between Si- and W-containing a-C and a-C:H considerably enhances the understanding of both the interaction between Si or W and the hydrogenation state as well as its effect on the structure and tribo-mechanical properties of these films. Therefore, non-modified a-C(:H), Si-containing a-C(:H):Si, and W-containing a-C(:H):W films were systematically grown in a mid-frequency magnetron sputtering process. The formation of W-based nanocrystallites within a-C(:H):W is identified by x-ray diffraction, whereas a-C(:H):Si still possesses an amorphous character. Raman scattering spectra show higher I(D)/I(G) ratios for hydrogen-free a-C(:X) films compared to the respective a-C(:H):X, indicating a higher number and larger sizes of sp2 clusters in the carbon network. For the hydrogenated a-C:H:X films, the reduced number of sp2 clusters is related to the presence of terminating C[sbnd]H bonds, which were detected as stretching modes. Among the different films, a-C:W has the highest I(D)/I(G) ratio, while a-C:H and a-C:H:Si exhibit the lowest I(D)/I(G) values. While a-C:Si and a-C:H:Si are characterized by comparable hardness values of (18.7 ± 1.3) and (18.4 ± 1.1) GPa, a-C:W has a lower hardness of (13.8 ± 1.0) GPa compared to a-C:H:W with (17.5 ± 0.9) GPa. Among all modified a-C(:H):X films, a-C:Si and a-C:H:Si reveal the lowest coefficients of friction, but show highest wear rates in dry sliding against 100Cr6 steel. Contrarily, a-C:W has higher friction and wear than a-C:H:W. Consequently, the Si-containing a-C(:H):Si films demonstrate comparable tribo-mechanical properties, while the hydrogenation state leads to different tribo-mechanical properties of a-C(:H):W.
查看更多>>摘要：? 2022 Elsevier B.V.Energy storage devices such as supercapacitors with flexible electrodes are used in new technologies of the modern printed electronics system. These flexible energy stores can power systems containing chips, microcontrollers and others. For the development of these flexible electrodes, carbon fiber felt (current collector) with polyaniline (active material) form a composite material with high performance of transport and storage of charges, lightness and flexibility. So, to obtain an electrochemical performance of the electrode, in this work the carbon fiber surface was modified by thermal and electrochemical treatment (insertion of heteroatoms of oxygenated groups in the fiber) to enhance conductivity and the anchor of the polyaniline, respectively. After the carbon fiber felt underwent heat treatment at temperatures of 1250 °C, 1500 °C and 1900 °C, half of the fiber felt samples underwent a chronoamperometric activation process in a sulfuric acid at 1 mol L?1. Subsequently, polyaniline was electrodeposited onto the fibers via square wave voltammetry, and the materials were characterized by: scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry (CV), electrochemical impedance spectrometry (EIS) and Raman scattering. The composite in which the fiber was thermally treated at 1250 °C without electrochemical activation obtained a specific capacitance of 386.6 F g?1. The carbon fiber treated at higher temperature (1900 °C) and with electrochemical functionalization, obtained improved electrolyte/electrode interaction, which favored the PANI electrodeposition and specific capacitance (345.1 F g?1).
查看更多>>摘要：? 2022 Elsevier B.V.To avoid the complex transfer progress of graphene with the traditional chemical vapor deposition (CVD) method, we have developed a Cu nanoparticles (NPs) assisted-catalysis CVD process to directly deposit graphene on insulating substrates. It allows to controllably grow graphene by atmosphere pressure CVD according to regulating the distribution of Cu NPs. The fundamental growth conditions have been systematically investigated and the obtained graphene has preferable photoelectrical performance. Compared with a whole coated distribution of Cu NPs on the substrate, the transmittance of controllably deposited graphene significantly increases by 8.25% with decreased sheet resistance simultaneously. We further regulated the distribution of Cu NPs on the insulating substrate with a designed mask and directly prepared the patterned graphene with good achievement. This approach provides a facile and cost-effective way to directly prepare high-quality patterned graphene on target substrates and opens up a novel idea for fabricating various functional electronic devices.
查看更多>>摘要：? 2022 Elsevier B.V.To achieve automatic cutting of cast stainless steel risers, a brazed diamond saw blade is developed, and cutting 304 stainless steel tests are performed on the CNC machine tool. The temperature of the blade-debris contact zone for both dry and wet cutting is measured. The vibration signal during cutting is collected and analyzed. Wear characteristics and mechanism of diamond grinding particles and processed surface quality are studied. The results indicate that the cutting temperature was low, the vibration amplitude of the system was small and the surface quality of the cut was high during wet automatic cutting of 304 stainless steel. Low cutting temperature suppressed chemical wear of diamond abrasive grains, and small vibration improved the surface quality of the cut. However, poor results were achieved when dry cutting stainless steel. It is feasible that 304 stainless steel was wet cut using brazed diamond saw blades on CNC machine tool.
查看更多>>摘要：? 2022 Elsevier B.V.C60 has been the focus of many studies since its discovery, but the mechanical properties of this unique molecule remain poorly known. To remedy that, we performed density functional theory molecular dynamics calculations of the compression of C60 at finite temperature, within a large strain range. The possible recovery of the molecule after unloading was also investigated with first principles accuracy, for two different modes. We found that the behavior of C60 follows three regimes depending on the compression strain. Up to 0.48 ± 0.02, the deformation is elastic with a small but distinct influence of the compression orientation. A relation between the electronic gap and the orientation is also revealed. The second regime starts for larger strains up to 0.75 ± 0.02, after a 30–32 nN force plateau. It is characterized by stochastic carbon bond breakings. Although bonds rupture is generally the fingerprint of plastic deformation in materials, we found that the C60 structure can be dynamically recovered in a significant fraction of cases, following a fast unloading. This mode also yields defected structures with low energies compared to a slow unloading mode. Finally, the third regime corresponds to irreversible deformation of the molecule, for strains larger than 0.75 ± 0.02.
查看更多>>摘要：? 2022 Elsevier B.V.The current study offers an electroanalytical investigation and a novel voltammetric approach for the quantitative analysis of famciclovir (FCV) utilizing an unmodified boron-doped diamond (BDD) electrode. An irreversible, well-defined, diffusion-controlled anodic peak was observed at approximately +1.27 V (vs. Ag/AgCl) in acetate buffer solution (ABS, 0.1 mol L?1, pH 4.7) when the agent was tested using cyclic voltammetry. The voltammetric signals of the oxidation peaks are pH dependent (ranging from 2.0 to 7.0). Using square-wave mode, a good linear response was obtained for FCV quantification in 0.1 mol L?1 ABS (pH 4.7) solution at +1.26 V (vs. Ag/AgCl). Wide dynamic range was found for 0.1 to 50.0 μg mL?1 (3.11 × 10?7-1.56 × 10?4 mol L?1), with a low detection limit of 0.029 μg mL?1 (9.02 × 10?8 mol L?1). Applicability of the proposed method for the determination of FCV was demonstrated in the pharmaceutical formulation and model serum samples.
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