查看更多>>摘要：? 2022 Elsevier B.V.The SF6 decomposition products bring serious threats to the stable operation of the power systems. In this study, the adsorption properties of SO2, SOF2, and SO2F2 gases on single-molecular metal oxide (ZnO/CuO) doped graphene were investigated by density functional theory (DFT). The optimal sites of two metal oxides individually doping on graphene have been calculated, and their electrical conductivity has achieved considerable improvement compared to pristine graphene. Both ZnO-graphene and CuO-graphene have great adsorption energies for the three gases. In addition, the adsorption structures, charge transfer, band structure, density of states, and charge deformation density are analyzed to explore the feasibility of metal oxide doped graphene. For gases adsorption on ZnO-graphene the adsorption capacity is: SOF2 > SO2 > SO2F2, and for CuO-graphene the adsorption capacity is: SO2F2 > SOF2 > SO2.
查看更多>>摘要：? 2022 Elsevier B.V.Diamond-like carbon (DLC) films, deposited by dry processes, such as, physical vapor deposition and chemical vapor deposition, provide high hardness, lubricity, and wear resistance. With improvements in microfabrication technologies, tuning the microscopic surface morphology to control physical properties (such as wettability) of materials has attracted immense attention. However, the strengths of microstructures with uneven surfaces are insufficient for numerous applications. Therefore, nanoscale structures with uneven surfaces and enhanced strength were synthesized using DLC. Anodic porous alumina films with regularly aligned linear nanopores produced by anodic oxidation of Al were used as mask materials to deposit DLC films on Si substrates. Uneven structures (with uniform distributions of DLC nanoscale protrusions) were created on the substrates. Mask materials with large pore diameters and small thicknesses created DLC protrusions with large diameters and heights, respectively. The friction coefficients of nanostructured DLC surfaces with tall protrusions and normal DLC films were similar. Unevenly structured DLC surfaces were slightly more water-repellent than normal DLC films, with greater water repellency for taller protrusions. The Cassie-Baxter model was applied to analyze the surface wettability. This report describes a new, simple, and effective method of fabricating DLC nanoscale structures using anodic alumina films.
查看更多>>摘要：? 2022 Elsevier B.V.A fluorine doped graphene (FDG) film was deposited on the surface of roving fabric by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD). The micromorphology, functional group types, chemical composition, molecular structure and nanostructure image of the deposited films under different discharge power were characterized by field emission scanning electron microscope (FE-SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and transmission electron microscope (TEM). The static and rolling?water/?oil contact angle were measured by contact angle meter. The electrochemistry properties were tested using electrochemical workstation. The superamphiphobic mechanism was studied by electrochemical impedance spectroscopy (EIS) and density functional theory (DFT), and the corresponding software were Gemry Echem Analyst and Materials Studio 7.0, respectively. The results show that the obtained FDG film has the best hydrophobic and oil repellent performance under the discharge power of 80 W. F atom in the FDG film is arranged on both side and the capacitance structure (C-model) is presented in the equivalent element by EIS fitting and DFT calculation under the discharge power of 80 W. The phenomenon proves that the electron transfer of free electrons from the position of K point in the Brillouin region of graphene surface was forbidden by the F atom, which is the mechanism of superhydrophobic and oil drainage on the FDG film surface.
查看更多>>摘要：? 2022 Elsevier B.V.Degradation of unsymmetrical dimethylhydrazine (UDMH) by graphene-based semiconductor composites is an effective photocatalytic method. To make full use of the solar energy, the composites were doped by non-metal atoms. One critical issue for the composites is understanding the electronic property relating to light absorption and carrier transfer. In this study, the NG (N-doped graphene)/TiO2 composites were fabricated, characterized and deeply investigated based on the density functional theory (DFT) calculation. Particularly, the resultant new energy levels in the band structure could decrease the bandgap of semiconductor, promote charge-transfer at the interface of graphene and TiO2, improve the light absorption, and finally enhance the photocatalytic activities. An excellent agreement of electron properties is found between our theoretical calculations and the characterization analysis of UV–vis DRS and RAMAN spectra. A possible photocatalytic mechanism based on the band structure and ESR result was developed. Thus, the NG/TiO2 composite could be a promising photocatalyst for UDMH degradation under the visible light.
查看更多>>摘要：? 2022A small grinding wheel of 3.2 mm in diameter was prepared from nano-polycrystalline diamond (NPD) obtained by direct conversion sintering under high pressure and high temperature. Using this NPD wheel as a grinding blade, a new useful method for investigating the micro-scale abrasive properties of single-crystal diamonds was developed. Since NPD has an extremely high hardness of about 130 GPa, the abrasive properties of various natural and synthetic single-crystal diamonds, whose hardness is usually around 70 to 125 GPa, can be appropriately evaluated. In addition, since the wheel diameter is very small, it is possible to measure the abrasion resistance in a minute region of several tens of μm in a diamond crystal. It was confirmed that the method can accurately evaluate the abrasive properties of minute regions of single-crystal diamonds using synthetic type IIa diamond. It was also demonstrated that it is possible to investigate how the abrasive properties of synthetic type Ib and natural type Ia diamonds change depending on the distribution of impurities or crystal defects in the crystals.
查看更多>>摘要：? 2022 Elsevier B.V.We use molecular dynamics (MD) simulations to deform single crystal spherical carbon nanoparticles (NP), 4–45 nm diameter, with a hard, flat indenter, compressing along the [001] direction. There is no clear amorphization nor phase change in the NP, but there is significant deformation, with bent crystalline planes, and many atoms that retain sp3 coordination, but are no longer recognized as having diamond structure by different structure-identification methods. Machine-learning is used to improve diamond-structure identification. The NP deforms laterally, and volumetric strain is ~0.1 when the uniaxial strain is ~0.5. Poisson's ratio increases with strain, and the elastic limit is reached at 0.2–0.3 strain, at a contact pressure of ~150 GPa. For NPs above 5 nm, dislocations appear and are mostly (1/2)<110>{111} full dislocations, with a few partial dislocations for larger nanoparticles, without twinning. These results agree with the recent observation of plastic deformation in diamond nanopillars. Small NP display elastic modulus, yield stress and hardness increasing with NP size, but NPs with diameter larger than 25 nm display an approximately constant dislocation and dislocation junction density, which leads to a plateau in the hardness versus NP size, at ~150 GPa, close to bulk diamond. Diamond nanoparticles could provide high strength thin coatings, lighter than full-density nanotwinned diamond but with nearly the same strength.
查看更多>>摘要：? 2022New brazed diamond specimens were prepared by adding different types of rare earth (RE) alloys to Cu-Sn-Ti filler metal. The microstructure and mechanical properties of the filler metal were characterized, and the interfacial characteristics and grinding properties of the brazed diamond specimens were analyzed. The addition of rare earth alloy (10% Cu-La alloy, 10% Cu-Ce alloy, and 10% Cu-Nd alloy) can improve the microstructure of the filler metal, reduce the number and size of holes and cracks in the filler metal, and improve the mechanical properties of the filler metal. The results of the grinding tests showed that the addition of the three rare earth alloys could improve the holding strength of the filler metal on the diamond grains, reduce the shedding rate of the diamond grains, and improve the grinding performance of the brazed diamond specimens. Compared with the other two rare earth alloys, the addition of 10% Cu-Nd improves the mechanical properties of the filler metal most significantly, and the best grinding performance of brazed diamond samples is obtained because there is no composite undercooling and aggregation of rare earth elements. The mechanism of rare earth alloy to improve the holding strength of filler metal to diamond abrasive grains was elucidated that the rare earth elements consume Cu and Sn elements in the filler metal, and the enrichment of Ti elements at the interface increases the thickness of the TiC interfacial layer. In addition, the reduction of cracks and holes in the filler metal decreased the defects around the diamond of the brazed specimen, effectively avoiding the rapid expansion of cracks along with these defects during the grinding process.
查看更多>>摘要：? 2022 Elsevier B.V.Today, boron-doped diamond (BDD) is among the key materials for electrochemical sensing and advanced oxidation of micropollutants. Therefore, a cost-effective fabrication of large-area BDD electrodes is of high interest. We present an implementation of a liquid-phase boron precursor trimethyl borate for large-area deposition of boron-doped diamond films by linear antenna microwave plasma CVD. Trimethyl borate vapors were used not only as a source of boron for doping but also as the only source of carbon and oxygen, while completely saturating the requirements for the growth of high-quality boron-doped diamond films. However, to allow for control over the doping level through maintaining the B/C and B/O ratios, carbon dioxide was employed as an additional source of carbon and oxygen. The film morphology was controllable from microcrystalline to ultra-nanocrystalline by changing the concentrations of trimethyl borate. Using this unique precursor system, we were able to grow diamond films with a doping level in range from 8 × 1017 cm?3 to 2 × 1022 cm?3 and resistivity as low as 1.16 × 10?2 Ω·cm. Low activation energies were calculated from the Arrhenius plot and growth rates as high as up to 170 nm/h for the low pressure microwave plasma CVD were reached. The investigation of the plasma emission spectrum revealed a chemical composition similar to that of hydrogen-rich plasmas with methane, and the proposed chemical reactions indicate that the diamond growth takes place via the hydroxyl radical. The results demonstrated that trimethyl borate is a suitable source of carbon and boron for the large-area growth of highly boron-doped diamond via low pressure microwave plasma CVD methods.
查看更多>>摘要：? 2022 Elsevier B.V.The electronic structures of a series of penta-BCN monolayers with point-defect, compression and tensile strains, and heteroatom substitution were investigated by the first principle calculations. It was found that the ±10% biaxial strains on penta-BCN monolayer lead to a change in band gap from 2.65–3.37 eV. The B and N point-defects open the magnetism and a significant decrease in band gap of penta-BCN monolayer. The influences of heteroatoms on band gap of penta-BCN were also studied. It was shown that the substitution of Al and Ga lead to a significant decrease in band gap. Our study indicates that the band gap of penta-BCN can be efficiently modulated through different ways, which will expand the application of penta-BCN in photoelectric and photovoltaic fields.
查看更多>>摘要：? 2022Many attempts are being made globally to synthesize and functionalize different nanomaterials to facilitate the commercial application of polymer electrolyte membrane (PEM) fuel cells. In this work, firstly nitrogen-doped reduced graphene oxide (NRGO) was synthesized and mixed with carbon nanotubes (CNT) followed by the incorporation of Pd- and Fe-content through a combined thermal annealing and polyol process to obtain a unique nanohybrid Pd-Fe2O3 decorated NRGO-CNT to be applied as an effective electrocatalyst. The experimental analyzes suggest thorough distribution of the Pd-Fe2O3 nanoparticles over NRGO and CNT layers. The electrochemical activity of the Pd-Fe2O3/NRGO-CNT nanohybrid showed the enhanced electrochemical active surface area (ECSA) of ~44.92 m2/g than that of Pt/C ~37.86 m2/g. The developed nanohybrid also displays remarkable enhancement in their stability in contrast to NRGO-CNT/Pd, NRGO/Pd and commercially available Pt/C catalyst. These interesting features make the developed nanohybrid suitable for fuel cell applications.
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