查看更多>>摘要：? 2022Vitrified ultrafine diamond grinding wheels are ideal for machining next-generation semiconductor power device material, such as SiC etc. However, a crucial problem limiting the application of ultrafine diamond originates from the dispersion of aggregates in vitrified bond. In this study, in can be confirmed that the preparation of uniformly dispersed diamond/vitrified bond composites using sol-gel technique is feasible. Surfactants with various types and additions interactively promote the dispersion of diamond, which make both the bending strength and diamond dispersion of the composites are suitable for precision grinding. The results are valuable for the preparation of vitrified grinding wheels with ultrafine diamond for precision machining of semiconductor.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, we applied dislocation analysis to X-ray topography images to identify the complete dislocation information for two typical high-pressure high-temperature diamond crystals, IIa and Ib. Almost all dislocation line vectors of both crystals were identified for the first time. For IIa crystal, it was confirmed that up to 84% of the dislocations have 〈101〉 vectors. For Ib crystal, up to 71% of the dislocations have 〈112〉, 〈121〉, and 〈211〉 vectors. Both [110] and [1-10] with zero components of the c-axis are the major Burgers vectors. Regarding the types of dislocation, the major types were edge types, which were approximately 47% and 65% for IIa and Ib crystals, respectively. In addition, screw, 60° and 73° type on the IIa, and 30°, 35°, and 73° type on Ib were identified. Complete analysis of dislocations will give important information for the diamond growth and reduction of the dislocations.
查看更多>>摘要：? 2022Agricultural pesticides are known as the most important causes of water pollution due to their high environmental stability and production of carcinogenic products. Chlorpyrifos is broadly utilized to control pests in agricultural, residential, and commercial applications. The release of chlorpyrifos into water and wastewater sources may affect human health because of its chronic toxicity to aquatic organisms. Therefore, its degradation seems necessary. The present study aimed to investigate the photocatalytic efficiency of biochar nanocomposite based on grapefruit skin modified with Fe3O4 and CdS nanoparticles (biochar/CdS-Fe3O4) in the degradation of chlorpyrifos pesticide as an agricultural contaminant. The synthesized nanocomposites were characterized using field emission scanning electron microscopy (FESEM) with energy dispersive X-Ray spectroscopy (EDS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The synthesized nanocomposite showed excellent photocatalytic performance due to the improved separation of electrons and holes produced by CdS and the inhibition of agglomeration of these nanostructures by combining them at the biochar surface. According to the results, 97% of chlorpyrifos was degraded by the prepared nanocomposite during the photocatalytic process. The photocatalytic activity of the synthesized nanocomposite was dependent on the parameters of time, pH, pesticide concentration, amount of used photocatalyst, which were optimized. The pseudo-first-order kinetic model derived from the Langmuir-Hinshelwood equation well describes the behavior of the experimental data in this study. It was also reused several times after washing to evaluate the stability of the synthesized photocatalyst. This study introduced a new type of photocatalyst for pesticide degradation.
查看更多>>摘要：? 2022 Elsevier B.V.CNTs are decorated uniformly with nano Ni through electroless plating method (CNTs@Ni). Average contact angle with 2024 aluminum alloy reduces from 138.6° to 81.2°, significantly improving wetting of CNTs. CNTs@Ni are used as the reinforcement to fabricate 2024-CNTs@Ni composites via high-intensity ultrasonic-assisted casting method. The appropriate content of CNTs@Ni assists 2024-CNTs@Ni composites to obtain excellent microstructure, mechanical properties and electrochemical corrosion resistance. When the CNTs@Ni content is 1.5 wt%, CNTs@Ni are uniformly dispersed, uniform organization and grain refinement is most significant according to the results of scanning electron microscopy. CNTs@Ni composites exhibit more excellent mechanical properties than cast 2024 aluminum alloy. This results from a synergy of grain refinement strengthening, thermal mismatch strengthening, Orowan strengthening and load-bearing strengthening. The percentage contribution of each strengthening mechanism is calculated for composites with different CNTs@Ni content. In addition, 2024–1.5 wt% CNTs@Ni composites show better electrochemical characteristic with higher corrosion potential of ?603.792 mv and lower corrosion current density of 102.332 μA·cm?2. Cl? ions are more resisted because of Ni introduction. The large number of dislocations accelerates the diffusion of elements, which expedites formation of thicker protective films to resist corrosion. The phenomenon of “large anode - small cathode” improves the electrochemical corrosion resistance.
查看更多>>摘要：? 2022Phenolic resin was thermally cured on the melamine-based amino foam fiber to construct a nitrogen-containing composite. By employing the composite as the precursor, nitrogen doped microporous carbons were synthesized by two process schemes. One process was two-step of pre-carbonization and further activation (TNC). Another route was one-step of simultaneous activation and carbonization (ONC). Physicochemical properties of resulting carbons were characterized, and super-capacitive performances were also examined. Specific surface area of TNC and ONC were 1657 and 1223 m2 g?1, respectively. The doped nitrogen in the corresponding carbons were determined to be 2.6 and 3.1 at.%. Using the TNC and ONC as electroactive materials, in a three-electrode test configuration in 6.0 M KOH aqueous electrolyte, the electrode harvests the specific capacitance of 316.4 and 303.8 F g?1 at 1.0 A g?1 current density, respectively. When the current density increased to 10 A g?1, retention rates of the corresponding specific capacitance were 88.7 and 85.9%, respectively. In the symmetric-electrode system in aqueous electrolyte, an electrode enclosed the TNC exhibited a specific capacitance of 269.7 F g?1 at the current density of 0.5 A g?1. The assembled simulated supercapacitor delivered an energy density of 9.6 W h kg?1 with the power density of 124.9 W kg?1. The purpose of the present work was to clarify the effect of preparation procedures on the physicochemical properties and super-capacitive performances of porous carbons. Findings demonstrated that the porous carbon prepared by two-step of pre-carbonization and then reactivation showing larger specific surface area and better super-capacitive performance than that of synthesized via one-step of in situ carbonization and activation.
查看更多>>摘要：? 2022 Elsevier B.V.When the wastewater containing 4-nitrophenol is restored on an industrial scale, it is needful to find an efficient catalyst which can be used in a continuous flow apparatus. Here, graphene nanosheets loaded with Ag nanoparticles were immobilized on Ti meshes. Afterwards, their catalytic behavior was explored in a continuous flow apparatus for the reduction of 4-nitrophenol. It can be found that the Ag nanoparticles loaded graphene nanosheets immobilized on Ti meshes are an efficient catalyst for elimination of 4-nitrophenol from water which is suitable for continuous flow system. When the 4-nitrophenol solution run through the above-mentioned Ti meshes at flow velocity of 3 mL min?1, 92% 4-nitrophenol (100 mL, 1.0 × 10?4 mol L?1) could be eliminated in 150 min. Moreover, this integrated catalyst can also exhibit quite satisfactory durability. After it was used two times, its catalytic activity still could maintain 84% activity of the fresh sample in the third cycle.
查看更多>>摘要：? 2022 Elsevier B.V.Recently, lithium?sulfur batteries have attracted much more attention due to their high specific capacity, energy density and wide range of sources. Here, a simple method to prepare sulfur host material was explored. In this method, carbonized cellulose nanofibrils doped with carbon nanotubes were used as the matrix and applied in the cathode. It was found that the sample 40-CNFC with the mass ratio of carbon nanotubes to cellulose dry weight of 4:6 showed the best three-dimensional porous network structure, and its specific surface area was up to 254.4 m2 g?1. After loading sulfur, the initial specific capacity of 40-CNFC@S was 1168 mAh g?1 at 0.1C, and the initial specific capacity of 858 mAh g?1 was still up to 739 mAh g?1 after 120 cycles at 0.5C, providing an available access for designing a promising electrode material for lithium?sulfur batteries.
查看更多>>摘要：? 2022Herein, we report the development of a simple green methodology to fabricate N-doped carbon quantum dots (N-CQDs) with a high luminescence using R. graveolens leaves following the hydrothermal method. Optical, chemical, morphological, and electrochemical properties were thoroughly investigated employing a variety of analytical techniques. The fabricated N-CQDs have a spherical shape, with an average diameter of 4.5 nm. Excitation dependent emission behaviour, 18% QY and green fluorescence were all observed in the N-CQDs. They are particularly resistant to various impacts such as ionic strength, pH, continuous visible light irradiation, and storage time. Since Cr(VI) ions are highly carcinogenic and mutagenic, there is an urgent demand for sensitive, selective, and efficient sensors for monitoring and measuring the amount of Cr(VI) ion in water in the environment. Hence, we developed the prepared N-CQDs as a label-free fluorescence and electrochemical probe for detecting Cr(VI) ions selectively and sensitively in aqueous solutions. Relying on static quenching together with the inner filter effect, N-CQDs performed exceptionally well as fluorescence sensors for Cr(VI) ions. The N-CQDs exhibit a limit of detection of 300 and 5 nM in the photoluminescence and differential pulse voltammetry analysis, respectively. The detection of Cr(VI) ions in real water samples using the developed sensor through both methods presented high precision without any interference. In addition, we also developed paper sensing strips for field application by depositing N-CQD on filter paper, which has been satisfactorily evaluated for sensing Cr(VI) in solid-state and solution mediums.
查看更多>>摘要：? 2022 Elsevier B.V.Currently, epoxy-based composites are widely used in thermal management. However, with the development of complex and high power-density electronic devices, the thermal properties of the composites need to be improved. Inspired by the unique galls-leaf structure of Distylium chinense, a graphene-diamond framework (GRDF) is developed by a simple filtration method. A through-plane and in-plane thermal conductivity of 22.7 and 21.8 Wm?1 K?1, respectively, have been achieved by forming epoxy-based composites with the GRDF annealed at 3000 °C. The result is 70% higher than the best-reported value for epoxy-based composites prepared by vacuum filtration under a filler content of 43 wt%. Such high thermal conductivity remains unchanged (within 2%) in a temperature range from 25 to 100 °C. Based on various microscopic characterizations, the diamond particles evenly distribute in a framework formed by graphene sheets, which bridge the gaps in the framework and improve its structural integrity. High-temperature annealing converts most diamond particles to graphite, which further enhances the thermal properties of the composite. The observations provide a feasible way for developing polymer-based composite with high thermal conductivity, which could meet the ever-increasing demands for heat dissipation in high-power electronics.
查看更多>>摘要：? 2022 Elsevier B.V.We studied the interaction of 5-Fluorouracil (5-FU) with Au32 and C60 fullerene nanocage by Density Functional Theory (DFT). From its different active sites, 5-FU was approached to the gold surface. All geometrical and energetic parameters of the complexes were calculated with the B3LYP–D3 considering the implicit solvent effect. From the results, the interaction energy is determined ?18.91 and ? 6.23 (kcal/mol) for the Au32 and C60 respectively, which reveals that 5-FU tends to absorb stronger to the gold-fullerene rather than C60. The DFT-based results for interaction energy determination are validated against high-level quantum chemistry method. Our findings reveal also that the dispersion forces play important role in the interaction properties prediction. Electronics structures and molecular descriptors of energetically stable complexes are further evaluated. Finally, DFTB-MD simulation for considered complexes in aqueous solution and ambient conditions showed that 5-FU was attracted to the implicit water molecules and bound weakly to the gold nanocage surface while it holds its attached position in the 5-FU/C60 complex. The present finding demonstrates that both Au32 and C60 nanocages could not be functionalized with the 5-FU drug in a water environment at ambient conditions.
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