查看更多>>摘要：? 2022 Elsevier B.V.Traditional hollow-fiber membranes (HFM) in the oxygenator are in short supply due to their complicated manufacturing process, high price, and tight production capacity. To address these challenges, herein we designed a simplified molecular dynamics (MD) model that mimics the working procedure of HFM to explore whether carbon ene-yne (CEY) and other two carbon-based 2-dimensional (2D) materials: γ-graphyne and graphdiyne (GDY) could be used in an oxygenator. With the aid of the Density Functional based Tight Binding (DFTB) method, Density Functional Theory (DFT), Adaptive Steered Molecular Dynamics (ASMD), and NVT molecular dynamics (MD) simulations, the penetration barriers of the O2, CO2, and H2O molecules through these three 2D membranes are estimated. Furthermore, their permeance under various differential pressures are also discussed. According to our simulations, the CEY membrane can provide a much better performance for O2 and CO2 exchange than the most commonly used HFM material. CEY should be a promising candidate as O2 and CO2 exchange membrane working in the oxygenator.
查看更多>>摘要：? 2022 Elsevier B.V.Zn0.5Ni0.5Fe2O4 nanopowders as heating agents could be used for hyperthermia due to their magnetic characteristics. However, due to the lack of suitable surface properties, magnetic ferrites do not have proper drug absorption capacity and sometimes show cytotoxicity. These concerns limit their application in medical use. A simple one-step method to synthesize the Zn0.5Ni0.5Fe2O4/carbon nanocomposite is an effective strategy to solve these issues. Metal salts and citric acids were dissolved in water and heated till combustion was taken place. In this procedure, the synthesis of magnetic material and carbonization occurred simultaneously. The results showed that Zn0.5Ni0.5Fe2O4 nanoparticles were uniformly engulfed into carbon produced by a self-propagating combustion method. Magnetic properties of Zn0.5Ni0.5Fe2O4/C nanocomposite showed the ferrimagnetic characteristics with the saturation magnetization of about 54 emu/g. The specific loss power (SLP) values of the samples heat-treated at 100 and 400 °C were 14 and 42 W/g, respectively. The produced samples were loaded with cephalexin. The cephalexin-loaded Zn0.5Ni0.5Fe2O4/C nanocomposite demonstrated controlled drug release, efficient antibacterial characteristics against Staphylococcus aureus, and Escherichia coli, and significant hyperthermia ability. Therefore, the synthesized nanocomposites might open up a way for efficient hyperthermia and drug release applications and have a prospective use in medical science.
查看更多>>摘要：? 2022 Elsevier B.V.Volatile organic compounds (VOCs) are among the primary concerns due to their practical threatening on living environment and human health. This work aims at examining the physical adsorption behavior of four representative VOC species on hydroxyl-functionalized CNTs in terms of molecular dynamics simulations. Simulation results indicate that the adsorption affinities of these four VOC species follow the order of toluene > ether > acetone > methanol for both the unfunctionalized and hydroxyl-functionalized CNTs. This adsorption preference is endorsed by the binding energy calculations based on the umbrella sampling algorithm. The surface modifications due to the introduction of hydroxyl groups affect both the adsorption mechanism and equilibrium configuration. The hydrogen-bond network near the adsorption region is rebuilt for stabilizing the adsorption kinetics. Compared to the dominant van der Waals interaction, the electrostatic interaction between the charged hydroxyl groups and the VOC molecules are found to be much less significant. With the increase of hydroxyl concentration, the adsorption affinity decays for all four VOC species. This conclusion is confirmed by both the binding free energies and the number of successfully adsorbed VOC molecules. The fundamental mechanism is due to the reduction of the originally hydrophobic area of CNTs surface and the additional bonding competition from water molecules. This work presents a molecular insight on the interaction between VOC molecules and hydroxyl-functionalized CNTs in aqueous solution. It can also benefit the development and design of smart filtration devices of VOC molecules for their early removal in aqueous solutions.
查看更多>>摘要：? 2022 Elsevier B.V.The interactions between H2O, O2, H2O + O2 and graphene carbon nitride (g-C3N4) surface were investigated by using first-principle method. The results indicated that the N atoms near the bridge sites and vacancies for g-C3N4 surface have high activity, which can promote the dissociation of water molecules and form hydrogen bonds after water and oxygen adsorption. The H2O and O2 molecules are not dissociated for only H2O or O2 molecules adsorption on g-C3N4 surface, and the hydrogen bonds are formed after H2O molecule adsorption. Two oxygen atoms of O2 molecule are bonded to carbon and nitrogen atoms of g-C3N4 surface respectively after O2 adsorption. There are two stable configurations for H2O + O2 co-adsorption on g-C3N4 surface (MA and MC), and their adsorption energies are ?57.35 kJ/mol, ?61.10 kJ/mol, respectively. For the MA, two oxygen atoms of O2 molecule are bonded to C and N atoms of g-C3N4 surface, respectively, and one hydrogen bond is formed between H2O and O2 molecules. As for the MC, three hydrogen bonds are formed in the interface of H2O + O2 and g-C3N4 surface. H2O molecule is dissociated, and O2 molecule turns to superoxide radical by gaining electrons. The formation of superoxide radical contributes to the degradation of organic pollutants for g-C3N4.
查看更多>>摘要：? 2022 The AuthorsThe impacts of nitrogen (N) doping on the lateral growth mode during two-dimensional (2D) nucleation, on the growth rate, and the incorporation of nitrogen (concentration [N]) of (111)-oriented diamond films were investigated by modulating the [N2]/[CH4] gas admixture ratio. The 2D nucleation density first increased with increasing [N2]/[CH4] ratio between 0.02 and 20%. Further increase of the [N2]/[CH4] ratio to up 200% caused a decrease of the nucleation density. The growth rates showed the similar N-doping dependence as the nucleation density variation. This is attributed to an initial increase of CN radicals in the regime 0.02 to 20%, followed by a reduction of CHx radicals in the regime 20 to 200%. The nitrogen incorporation concentration increases with increasing the [N2]/[CH4] ratio. The highest nitrogen concentration with 2 × 1020 atoms/cm3 is detected with [N2]/[CH4] = 200% and a relatively low nucleation density is achieved. These results are beneficial for the optimized formation of nitrogen-vacancy centers used in a quantum metrology and for device application such as inversion-channel diamond MOSFETs.
查看更多>>摘要：? 2022Reliable lubrication is the key to ensure the safe service of space equipment moving parts, but the tribological performance of most lubricating materials in a vacuum environment is substantially degraded. Therefore, graphene/diamond-like carbon (DLC) coatings were prepared on 9Cr18 bearing steel substrates using a combination of radio frequency (RF) magnetron sputtering preparation of DLC coatings and airbrush coating graphene layers, and the structural characteristics and tribological properties of the coatings were comparatively investigated for the different times of graphene layer spraying. The results shows that the graphene surface layer formed a stable bond with the DLC substrate, but there were local wrinkles in the graphene sheets deposited by the airbrush, and the surface roughness of the coating increased with the increase of the spraying times. The graphene/DLC coating with 3 times spraying has relatively excellent tribological properties in vacuum, with an average coefficient of friction of about 0.08 and a wear rate of 4.59 × 10?7 mm3N?1 m?1. Based on the tribological testing results, the mechanism of the friction-reduction and wear reduction of the graphene/DLC coatings in vacuum were analyzed. In general, the graphene/DLC coatings have excellent tribological properties in vacuum and hold significant promise for applications in moving parts of aerospace equipment.
查看更多>>摘要：? 2022 Elsevier B.V.Nitrogen doped diamonds with great application potentials can be synthesized by using different doping sources (i.e., urea and N2), effects of which on growth behavior and properties of diamond films on WC-Co substrates were presented in this paper. The doping efficiency of urea was always higher than 0.12, much higher than that of N2 (always lower than 0.04). The sufficient N2 addition could increase growth rate, and induce apparent grain nanocrystallization, by modifying reactant gas phase chemistry. The grain nanocrystallization contributed more to the reduction of the surface roughness, and degradation of the diamond purity and mechanical properties. On the contrary, the urea doping resulted in much less degradation of the diamond purity and mechanical properties, while providing sufficient N incorporations into the diamonds. Besides, urea doping promoted the formation of the diamond (220) planes on the polycrystalline diamond surfaces, which had a close relationship with the actual N doping concentration in the diamond. The controllable adjustment of the growth and properties of diamond films, by selecting the doping source and optimizing the doping ratio, could help to meet distinctive application requirements, and balance the machining efficiency and application performance of diamond coated components.
查看更多>>摘要：? 2022 Elsevier B.V.The lignin based phenolic resin microspheres were prepared by using lignin to partially replace phenol and react with formaldehyde, namely LPR microspheres. The lignin based phenolic resin carbon microspheres prepared by carbonization of LPR microspheres were applied in electrochemical capacitors, namely LPRC microspheres. The results showed that the introduction of lignin reduced the particle size of LPR microspheres significantly. When the amount of lignin replacing phenol was 50% (mass fraction, the same below), the LPR microspheres with particle size distribution of 5 μm to 10 μm were carbonized at different temperature, namely 0.5-LPRC microspheres. Then the 0.5-LPRC microspheres were applied to electrochemical capacitors. The specific surface area and capacitance of 0.5-LPRC materials was 1859.61m2 g?1 and 298F g?1 of 1.0A g?1 at the carbonization temperature of 900 °C separately, which indicated that the LPRC materials had excellent capacitance performance.
查看更多>>摘要：? 2022 Elsevier B.V.Graphene-based poly(2-ethyl-2-oxazoline) (PEOX) and polyvinylpyrrolidone (PVP) blend-matrix nanocomposites were prepared employing different weight percentages of graphene nanoplatelets as filler by ultrasonication assisted solution casting method. These nanocomposites were explored for their thermal, electrical, dielectric, and mechanical properties, and antimicrobial efficiency. Thermogravimetric analysis demonstrated that graphene operates as a barrier to limit thermal diffusion across the PEOX-PVP blend matrix, and hence, improve thermal stability of nanocomposites. The dielectric and electric properties such as dielectric constant, dielectric loss, loss tangent and electrical conductivity of PEOX-PVP-10 wt% graphene nanocomposite were found to increase with temperature. The presence of semi-circles in the Cole-Cole plot indicated the existence of a relaxation process in the conduction mechanism of the nanocomposite. AC electrical conductivity, σAC, of PEOX-PVP-10 wt% graphene nanocomposite was found to obey Jonscher's power law. The temperature-dependent behavior of frequency exponent, s, of σAC discusses the applicability of correlated barrier hopping (CBH) model. The extracted DC conductivity from AC conductivity studies was found to be temperature-dependent and obey Arrhenius relation with activation energy of conduction, Ea, of 0.41 eV and 0.39 eV in the lower and higher temperature regions, respectively. The mechanical properties of nanocomposites were enhanced dramatically when graphene loading was increased, demonstrating that a better interaction exists between graphene and the PEOX-PVP blend matrix. PEOX-PVP-15 wt% graphene nanocomposite showed superior mechanical properties (tensile strength: 9.18 MPa and Young's modulus: 3.19 MPa) among the synthesized nanocomposites. Further, the antibacterial activities of these nanocomposites against Gram-negative (E. coli) and Gram-positive (E. facecalis) bacteria revealed differential action.
查看更多>>摘要：? 2022 Elsevier B.V.In this paper, we propose a tunable dual band perfect absorption structure based on cross four split ring resonator (CFSRR). The structure presented uses SiO2 as an isolation layer to separate the bottom silver layer from the top cross four split ring resonator, with which can capture more light energy and provide possibility to realizing perfect absorption. The finite difference time domain (FDTD) method is used to simulate the calculation, and some significant phenomena and conclusions are obtained. The simulation results show that the proposed structure can achieve dual band perfect absorption, and the performance of absorber can be tuned to any selected wavelength within the specified wavelength range by carefully designing the structural parameters (such as R, r, P, L, W, etc.) of the absorber. In addition, changing the Fermi level of graphene with the method of applying voltage gate can dynamically tunable the absorption performance of the structure without rebuilding a new structure. In this way, the manufactural cost is greatly saved. Finally, by changing the refractive index of the surrounding medium, the sensing performance of the structure is studied, and the sensing performance of the short wavelength and long wavelength can reach 20.48 μm/RIU and 25.77 μm/RIU, respectively. And the maximum value of FOM 4.55 and Q-factor reaches 10.84. This work has important reference value for the application of modulator, sensor and photoelectric device in practice.
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