查看更多>>摘要：? 2022 Elsevier B.V.The 316L stainless steel was widely used in medical, surgical instruments and human implant medical materials. The diamond-like carbon (DLC) films were deposited on 316L stainless steel by varying temperature, CH4:H2 flow rate, and deposition time in a microwave plasma chemical vapor deposition (MPCVD) system to improve their biocompatibility. The morphology and composition of deposited films were investigated using a scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscope. The results showed that with the increase in deposition temperature and the decrease in gas flow ratio, the structure of the film gradually became compact and smooth, and the graphite phase structure of the film tended to change to diamond phase. In addition, the island-like structure gradually grew into a sheet, and the defects in the films were reduced with the enhanced bonding force between the films and the stainless steel matrix. The optimum temperature and gas flow ratios were 900 °C and 10:190, respectively. Medical stainless steels containing DLC films had better bone-forming ability and biocompatibility than untreated.
查看更多>>摘要：? 2022 Elsevier B.V.The band gap of reduced graphene oxide, playing a key role in many application fields, could be controllably tuned by oxygen group. Otherwise, up to now, it is unclear for the relation between these two. Herein, it was addressed by analyzing the thermogravimetric analysis, fourier infrared spectroscopy, and in-situ infrared spectroscopy, a nonlinear variable band gap was confirmed by fitting Tauc plot and also by light responses of RGO detective devices. The results showed that the reduction of oxygen group strongly relies on the annealing temperature. Different oxygen groups were lost at different temperatures. The hydroxyl group and carboxyl groop was lost before 200 °C, the epoxy group and carbonyl group was lost between 200 and 400 °C, the C-OH was lost at 400–600 °C, which exactly led to nonlinear variable band gap from 1.9 eV to 0.9 eV. In addition, the nonlinear photoelectric response of RGO light detective device further proved that trend of band gap. Our work pave a way to deeply apply RGO into electronic fields.
查看更多>>摘要：? 2022In this work, various amine groups (ethylenediamine; EDA, tetraethylenepentamine; TEPA and polyethylenimine; PEI) functionalized 3D body-centered cubic mesoporous carbon materials (FDU16) were prepared to host sulfur to form FDU16-EDA/S, FDU16-TEPA/S and FDU16-PEI/S cathode materials for high performance Li[sbnd]S batteries. The materials were characterized by XRD, SAXS, SEM, TEM, Raman, EA, BET, CV and RRDE. The results showed that FDU16-PEI/S exhibited the largest initial discharge capacity of 1266 mAg g?1 at 0.1C and presented a lower capacity fading rate of 0.26% per cycle for the 100 cycles in comparison with the capacity fading rate of FDU16/S (0.41%), FDU16-EDA/S (0.31%) and FDU16-TEPA/S (0.29%). During the RRDE experiments, all samples revealed similar RRDE profiles in all disk voltage (DV) regions, suggesting they resemble the dissolution behavior of the LiPS intermediates during the cycling process. The FDU16-PEI/S owned a smaller slope value of ring current change in the DV II region, indicating a lower dissolution of LiPS intermediates from the sulfur electrode. The order of LiPS adsorption efficiency was shown to be PEI > TEPA > EDA. This study demonstrated carbon materials functionalized with large amine groups provide strong affinities with LiPS intermediates, resulting in notably improving cycle performance in Li[sbnd]S batteries.
查看更多>>摘要：? 2022Coal liquefaction pitch is a byproduct rich in polycyclic aromatic hydrocarbon generated during coal liquefaction process, and can be used to prepare porous carbon electrodes for electric double-layer capacitors. However, the effects of the proportion of pore volume in different pore size ranges on the electrochemical properties of porous carbon are still not well investigated. Herein, porous carbon was fabricated from liquefaction pitch and KOH at a mass ratio of 1:2 and activation temperatures of 600–900 °C. The results showed an increase in both specific surface area and total pore volume of the samples with the activation temperature, inconsistent with the changing trend of the specific capacitances due to well-stored electrolyte ions in micropores. In particular, micropores with pore volume diameter below 1 nm greatly impacted the specific capacitance performance of porous carbon. The pore volume with pore width below 1 nm first increased and then decreased with the activation temperature. Among samples, porous carbon prepared at activation temperature of 700 °C delivered the highest specific capacitance of 329 F g?1 at a specific current of 0.5 A g?1, and retained 254 F g?1 of specific capacitance at 20 A g?1 in 6 mol L?1 KOH electrolyte. The reason for this was related to the largest pore volume with pore width below 1 nm (0.43 cm3 g?1). Afterward, the optimized sample was assembled into a symmetrical supercapacitor and test results showed that 96.37% of the initial capacitance was retained after 10,000 cycles at 1 A g?1, suggesting good cycling stability. In sum, the as-prepared porous carbon is very promising for use as electrode material for supercapacitors.
查看更多>>摘要：? 2022 Elsevier B.V.Recently, specially-designed printed circuit board (PCB) milling cutters with specific cutting edge structures have been extensively applied. Hot filament chemical vapor deposition (HFCVD) diamond coatings uniformly deposited on cemented carbide (WC-Co) cutters can effectively improve their performance. To improve the coating uniformity, the complex cutters were precisely modeled and the temperature field generated by the HFCVD setup was simulated, using the finite volume method (FVM), taking spiral milling cutters as a reference for comparison. Temperature measurements revealed deviations between simulated and measured temperatures smaller than 4%, verifying the accuracy of the constructed model. Effects of some critical HFCVD setup parameters, including the filament height (Hf), the material and height of the sample holder (Ms and Hs), the material and dimensions of the heat insulating block (Mh, Hh and Ah), and the surface convection coefficient (h), were studied by the control variable method. Under the optimized conditions, the axial temperature deviation on cutting edges dropped from 193.3 °C to 64.3 °C for a PCB milling cutter, and from 53.3 °C to 29.6 °C for a spiral cutter, ensuring appropriate temperature ranges for fabricating high-quality diamond films. Besides, the two-dimensional plane temperature field and received radiation field of a cutter were both calculated by MATLAB. The results showed that heat conduction hindrance and heat convection reduction could effectively reduce energy consumption and improve the uniformity of substrate temperature. With the aim to study the specific cutting-edge structures, cross-sectional temperature distributions were further examined by presenting both simulations and numerical calculations. It was seen that the temperature distribution for PCB milling cutters was complicated, which was attributed to the densely-distributed cutting edges and long flute. Lastly, under the optimized HFCVD setup parameters, it was found that the grain size and thickness uniformity of diamond coatings, at different positions along the axial direction, were significantly improved, revealing the effectiveness of simulation as an optimization method.
查看更多>>摘要：? 2022 Elsevier B.V.In recent years, a single-layer two-dimensional (2-D) carbon material, penta-graphene, with an unusual negative Poisson's ratio and ultrahigh ideal strength has been gaining traction. Surprisingly, however, this excellent 2-D material is still in the conceptual stage, even the T12?carbon for the synthesis of penta-graphene has not received proper attention. Herein, the finite-size scaling effects of the chemically induced transformation of the T12?carbon structure with a stacking fault (AA-T12 carbon) is investigated using first-principles calculations. The results show that the AA-T12 carbon structure can very easily form a cage structure under the action of chemical induction, and the AA-T12 carbon-cage structure displayed satisfactory mechanical properties (Vickers hardness values of ≈62 GPa and a Young's modulus of 882 GPa). More importantly, the molecular dynamics simulation further indicates that this AA-T12 carbon cage@penta-graphene composite structure (which is named Y26, and composed with layered penta-graphene and AA-T12 carbon cage) can be used as excellent particle reinforcement material. This excellent result can be attributed to the AA-T12 carbon cage can provide high impact strength and high wear resistance, penta-graphene may provide the toughness and Poisson's ratio, and the gradient structure between the two phases may prevent the peeling of the hard phase. Therefore, we believe that Y26 provides a new path for penta-graphene and T12?carbon applications.
查看更多>>摘要：? 2022 Elsevier B.V.Boron-doped diamond layers have been grown by MW PECVD on substrates with a misorientation over the range of 0 to 90° relative to the (100) crystalline plane while keeping all other growth conditions constant. Deposited layers were characterized by scanning electron microscopy, atomic force microscopy, and Raman spectroscopy. The deposition rate, surface roughness, and boron incorporation vary according to the substrate misorientation. These results show the essential need for rigorous control of the substrate crystalline orientation in the synthesis of doped diamond for electronic applications. Thick, smooth, and free of surface defects boron-doped epitaxial diamond layers were obtained over a broad range of crystalline orientations at high growth rates and high boron incorporation efficiency. Novelty statement: This work reports on the effect of the substrate crystalline orientation on the morphology, growth rate, and boron incorporation in epitaxial diamond layers deposited by plasma-enhanced chemical vapor deposition.
NSTL
Elsevier