查看更多>>摘要：Magnetic carbon nanofibers (CNFs) carbonized at different temperatures were prepared from bacterial cellulose (BC) alloyed with magnetic fluid (MF) or Fe3O4 powder to facilitate the efficient use of biomass resources. The CNFs alloyed with magnetic nanoparticles demonstrated high saturation magnetizations and coercivities up to a carbonization temperature of 800 degrees C. Iodine-treated BC alloyed with magnetic nanoparticles showed a substantial increase in the char yields with lower saturation magnetizations compared to the iodine-untreated BC. The analysis of X-ray diffraction results implies that the magnetic properties are related to the types and relative amounts of iron and iron-containing compounds, and the existence of amorphous magnetic nanoparticles in the CNFs. Scanning electron microscopy results indicated that the surfaces of the MF-alloyed CNFs possessed a fused fibrous texture with voids, and the magnetic CNFs without iodine treatment featured crystalline nanoparticles. The MF-alloyed CNFs with iodine treatment demonstrated the maximum surface area and pore volume, while the MF-alloyed CNFs without iodine treatment mainly contained mesopores.
Mehrabani, MahboubeKhatibi, Mohammad MahdiSadeghzadeh, SadeghAshory, Mohammad Reza...
8页
查看更多>>摘要：In electronics, inductive capacitors are made by two conductive plates, which are filled with non-conductive material between them. In this study, the graphene nano-sheet is utilized as capacitor plates and boron-nitride nano-sheet as its filler, and the effect of interface type of that of nanostructures on the vibrational properties of nanocapacitor has been studied using Molecular Dynamics (MD) approach. For this purpose, different interface types of graphene and boron-nitride nano-sheets are studied, including; CB66NC, CB68BC, CB88BC, CB108BC, CB1010NC, CN88NC, CN108NC, and CN1010NC. For the MD simulation, the LAMMPS software is implemented. The obtained results showed that CB66NC has the highest natural frequency and this is the most comfortable interface type to fabricate nano-capacitors, from a vibrational perspective. Furthermore, the CB66NC has the most stable because the hexagonal connection interface is more stable than the octagonal and decagonal, and the Carbon-Nitrogen bond energy which is used in the CB66NC interface type is higher than the Carbon-Boron bond energy.
Ji, QianyuWang, BowenZheng, YajuanZeng, Fanguang...
8页
查看更多>>摘要：Graphene is an upcoming field emission material. However, graphene based thin film devices are prone to irreversible damage, and the stability for long-term operation is poor. In this study, bulk graphene emitter has been proposed for the first time. The emitter was generated by cold pressing using high quality graphene. The novel bulk emitter exhibited an outstanding field emission performance with the turn-on electric field (at 100 mu A/cm(2)) and threshold electric field (at 10 mA/cm(2)) values determined to be 0.73 V/mu m and 1.09 V/mu m, respectively, along with a maximum current density of 715.51 mA/cm(2). Besides, a stable emission of 209.78 mA/cm(2) was obtained continuously for over 60 h. The self-compensation electron emission mechanism of bulk graphene was proposed based on the morphological changes and simulation results.
查看更多>>摘要：To improve the microwave absorption performances of Fe3O4@N-C composite derived from Fe-MOF, 3D-graphene particles have been successfully dotted on the surface of Fe3O4@N-C composite through pyrolyzing 3Dgraphene/Fe-MOF composites. Moreover, it is obvious that the electromagnetic parameters of the composites can be effectively adjusted by controlling the addition of 3D-graphene. Consequently, the optimal composite displays outstanding microwave absorption performances. The value of maximum reflection loss achieves-57.53 dB at 10.72 GHz with the effective absorption bandwidth of 3.92 GHz (9.18-13.10 GHz) at 2.30 mm matching thickness. In addition, the maximum effective absorption bandwidth with the value of 5.62 GHz (12.38-18.00 GHz) can be achieved at 1.81 mm matching thickness, which almost covers the whole Ku band. This work is expected to provide a reference for the mass preparation of new lightweight microwave absorption composites.
查看更多>>摘要：Single-walled carbon nanotubes (SWCNTs) are ideal candidates for transparent conductive films (TCFs) due to their excellent optical transparency and electrical conductivity. The geometry of SWCNTs, including the tube diameter, bundle length and bundle diameter, is vital to high-performance TCFs. Herein, we synthesized SWCNTs by floating catalyst chemical vapor deposition (FCCVD). The SWCNT geometries were tuned by hydrogen (H-2), and we found that the tube diameter, bundle length and bundle diameter increase with the H-2 concentration. Besides, we observed the formation of SWCNT loop at the tube ends. Both the number and circumference of loops increased with the increment of bundle length. Further, the loops were also found to affect the conductivity of SWCNT thin film. Excessive number of loops with large size could reduce the conductivity of SWCNT thin film. At the optimized H-2 concentration, we obtained the SWCNT TCF with sheet resistances of 290 and 95 omega/sq. for the pristine and AuCl3 doped SWCNT films, respectively, at 90% transmittance. Our work demonstrates the importance of H-2 for SWCNT synthesis and the critical role of loops on film conductivity, blazing new ideas for future research to obtain SWCNT TCFs with improved performance.
查看更多>>摘要：Despite a great deal of research on the basic properties of C-60 to the present, no detailed and comprehensive reports are available concerning its degradation mechanism and oxidation kinetics. However, a deeper understanding of the oxidation mechanism of the most common fullerene broadens the horizons of potential applications, especially at high temperatures. Therefore, this study attempted to investigate the fullerene oxidation process using kinetic analysis under non-isothermal conditions. Initially, the powder was structurally and morphologically characterized accurately via XRD, Raman spectroscopy, FESEM, and TEM analyses. This was followed by simultaneous thermal analysis (STA) (i.e., TG and DSC) at four different heating rates (2.5, 5, 10, and 15 ? min(-1)) in airflow, and kinetic analysis was subsequently conducted to evaluate the thermal oxidation of C-60. The activation energy as evaluated by model-free methods turned out to be almost invariant within the specified range of reaction fraction (alpha). Model-fitting methods were also employed to identify the oxidation mechanism involved, from which emerged two models (i.e., R-3 (g(alpha) = 1-(1-alpha)(1/3)) and F-1 (g(alpha) = - ln(1-alpha))) as possible reaction mechanisms. However, further investigation using the Z(alpha) master plot method revealed that the kinetic model R-3, a phase-boundary process, is the controlling mechanism of C-60 oxidation with E asymptotic to 96 kJ mol(-1) and lnA asymptotic to 9.1 min(-1). Further examinations were conducted in the neutral atmosphere, and the partial oxidation process based on TEM and FESEM images revealed that oxygen and heat applied during the process play a central role in the deagglomeration of C-60 particles and the consequent oxidation. In fact, considering the spherical morphology and the agglomerates present in the C-60 powder, the contracting sphere kinetic model (R-3) was found to capture the oxidation process due to attacks by the oxygen molecules at the interface of C-60 powder agglomerates.
查看更多>>摘要：Boron-doped diamond film which was used as microwave attenuation material was prepared by DC arc jet chemical vapor deposition (CVD) and the boron-doped diamond attenuator for W-band traveling wave tube (TWT) was fabricated. The effects of boron concentration on microstructure, mechanical property and dielectric property were analyzed. Meanwhile, the performance of boron-doped diamond attenuators was evaluated. The results showed that the fracture strength of boron doped diamond was higher than 400 MPa, although it was slight decreased with the increasing of boron content in the diamond films. Very interestingly, the fracture strength of growth side was larger than that of nucleation side, the twinning band within the grains in the growth side play a critical role for this phenomenon. With the boron concentration increasing from 6.1 x 1018 cm-3 to 23.5 x 1018 cm-3, the average loss tangent of diamond films was increased from 0.05 to 0.32 in the range of 75-110 GHz, which indicated that the complex permittivity of diamond film could be controlled by tailoring boron content. Furthermore, the return loss and insertion loss of the boron-doped diamond attenuator was below -20 dB and -40 dB, respectively. These findings indicated that the boron-doped diamond displayed low reflection and good microwave attenuation. The boron-doped diamond attenuator was promising for using in vacuum electronic device with high performance.
Dodero, G.Grau, E. NosedaRoman, G.Company, A. Diaz...
9页
查看更多>>摘要：The co-adsorption of captopril and aspirin drugs on a silicon-doped (10,0) SWCNT is investigated using DFT calculations. By Si doping, the energy gap decreases that indicates an increase in the reactivity of pristine (10,0) SWCNT. The optimization of different structures indicates that captopril drug is stronger adsorbed than aspirin. According, the energy values show a noticeable increase in the stability of aspirin after captopril adsorption. The physical nature of the aspirin adsorption represents an advantage for easy desorption of the molecule, while the stronger adsorption energy of captopril predicts a controlled desorption of the drug without any structural variation. These results confirmed that the chemical modification of (10,0) SWCNT using silicon could be an effective potential carrier for the simultaneously controlled delivery of both drugs.
Van Trinh, PhamLee, JunhoKang, ByungchulMinh, Phan Ngoc...
9页
查看更多>>摘要：6061 aluminum (Al6061) alloy matrix composites with hybrid reinforcements composed of both carbon nano tubes (CNTs) and silicon carbide particles (SiCp) were prepared by spark plasma sintering technique. SiCp, CNTs and Al6061 powder were firstly mixed by a tip-sonication mixing, then frozen the suspension in liquid N-2, and finally freeze-dried in a vacuum to obtain the uniform dispersion of SiCp and CNTs. The SiCp/CNT/Al6061 hybrid composites containing homogenously dispersed SiCp and CNTs exhibited significantly improvements in hardness, tensile strength and yield strength values of 37%, 38%, and 49%, respectively, compared with those of SiCp/Al6061 composites without CNTs. The improvements in the mechanical properties were attributed to the synergistic strengthening effects of the CNTs and SiC particulates. The coefficient of friction and specific wear rates of the hybrid composites were decreased by the addition of low-friction CNTs due to the self-lubrication effect. The CNTs did not reduce the friction coefficient and specific wear rate of the specimens as significantly with the increase of the applied load. This could be resulted from the transformation of carbonaceous structures of CNTs during the tribological testing process.
Han, Cheng LinZou, Ai LiWang, Gong-dongLiu, Yue...
11页
查看更多>>摘要：In this work, three-dimensional (3D) Fe3O4 decorated CNTs/graphene oxide (Fe3O4-CNTs/GO) composite film was used to enhance glass fiber reinforced polymer (GFRP) resulting in three excellent performances of inter laminar toughening, resistance to temperature changes, and electromagnetic interference (EMI) shielding were all achieved. The end notch bending (ENF) test results showed that Fe3O4-CNTs/GO film enhanced GFRP was 60.51% and 79.64% higher than the baseline (GFRP without reinforcement film) after RT or temperature cycle treatment, while the GFRP of pure CNTs film was 21.79% and 26.34% higher than the baseline, respectively. The change in interlaminar toughness of Fe3O4-CNTs/GO samples by temperature cycle was also lower than that of the other two samples (Fe3O4-CNTs/GO film: 4.15%, pure CNTs film:11.15%, baseline: 14.35%). The average EMI shielding effectiveness of Fe3O4-CNTs/GO films with a thickness of only 0.052 mm was 25 dB, about 500% higher than the 5 dB of the control group (ordinary CNTs/Fe3O4/GO films, thickness 0.047 mm). Scanning electron microscopy (SEM) further confirmed the existence of the 3D frame structure and interlamellar strengthening interface of Fe3O4-CNTs/GO films.
NSTL
Elsevier