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1.
《等离子体物理论文集》2019,59(1):1-1
Schematic of the plasma species (ions and neutrals) deposition during nitrogen‐contained carbon nanofibers (N‐CNFs) growth, Fig. 1 of the paper by R. Gupta et al. 相似文献
2.
Conducting glass fiber fabrics (GFs) with double-scale roughness were fabricated by growing carbon nanofibers (CNFs) on its surfaces. The homogeneous growth of CNFs was achieved by the decomposition of C2H2 on glass fibers surfaces coated with Fe-doped mesoporous silica films at different C2H2 flow rates. The chemical composition and surface structure of the GFs before and after CNFs growth were examined by electron dispersive X-ray spectrometry (EDX), N2 full isotherms, and scanning electron microscopy (SEM). The electrical properties of the GFs were examined using a four-probe volume resistivity tester. The CNFs with a mean diameter of 50 nm grew uniformly and densely on the glass fiber surfaces. The CNFs/GFs fabrics surface exhibited excellent electrochemical properties due to the CNFs. The specific capacitance of the GFs ranged from 0.2 to 4 F/g at 1 A/g in a 1 M H2SO4 aqueous solution. 相似文献
3.
Epitaxial Growth of Urchin‐Like CoSe2 Nanorods from Electrospun Co‐Embedded Porous Carbon Nanofibers and Their Superior Lithium Storage Properties 下载免费PDF全文
Jinkai Wang Hongkang Wang Daxian Cao Xuan Lu Xiaogang Han Chunming Niu 《Particle & Particle Systems Characterization》2017,34(10)
A facile synthesis of porous graphitic carbon nanofibers (CNFs) with encapsulated Co nanoparticles (denote as Co@CNFs) via electrospinning and subsequent annealing is reported. The in situ generated Co nanoparticles (NPs) promote the CNF graphitization under a low temperature of 700 °C, which simultaneously results in the porous structure of the Co@CNFs with a large surface area (416 m2 g?1). Furthermore, urchin‐like CoSe2 nanorods are epitaxially grown from the Co@CNFs via a facile hydrothermal selenation, in which the embedded Co NPs serve as directing seeds and sacrificial Co‐source, and CoSe2 nanorods are rooted into the CNFs (denote as CoSe2@CNFs). When used as anode materials for lithium ion batteries, the CoSe2@CNFs demonstrate superior lithium storage properties, delivering a high reversible capacity of 1405 mA h g?1 after 300 cycles at a current density of 200 mA g?1. The enhanced lithium storage performance can be attributed to the novel hybrid structure, namely, the porous and graphitic CNFs can not only facilitate the charge/ion transfer but also buffer the volume changes of the electrode during lithiation/delithiation processes. More importantly, a general strategy is provided to graphitize amorphous carbon materials via the use of in situ generated transition metal nanoparticles as catalyst. 相似文献
4.
《Physica E: Low-dimensional Systems and Nanostructures》2011,43(10):2799-2803
In this study, the electrochemical capacitor characteristics of vertically aligned carbon nanotubes (VACNTs) with different nitrogen content were investigated. The pristine VACNTs and nitrogen-doped VACNTs were synthesized by thermal chemical vapor deposition (CVD) with a mixture of C2H2 and NH3 gases. The content of nitrogen doped into VACNTs played an important role in enhancing the capacitance characteristics. With increasing the NH3 pressure, the nitrogen content of VACNTs increased. However, the capacitance did not increase with the increase in nitrogen content of VACNTs entirely. There was an optimal NH3 pressure for synthesizing the nitrogen-doped VACNTs to obtain the maximum capacitance. Furthermore, for the real practice of supercapacitor, the stability of capacitance was tested for 500 cycles. The results revealed that the nitrogen-doped VACNT was a promising supercapacitance device material. 相似文献
5.
Functionalization of carbon nanofibers with elastomeric block copolymer using carbodiimide chemistry
Javed A. Mapkar 《Applied Surface Science》2009,255(9):4806-4813
Surface functionalization of carbon nanofibers (CNFs) with aminopropyl terminated polydimethylsiloxane [(PDMS-NH2)] and other organic diamines was achieved using carbodiimide chemistry. The carbodiimide chemistry provides faster reaction rate so that the reaction occurs at lower temperature compared to amidation and acylation-amidation chemistry. CNF functionalized with PDMS-NH2 fibers were further functionalized with oligomer of polyimide (6FDA-BisP) using imidization reaction. The formation of block copolymer on the surface of CNF is proposed as an effective method to engineer the interphase between the fiber and the polymer, which is essential to modulate and enhance the properties of the nanocomposite. The efficiency of the carbodiimide chemistry to functionalize amine terminated groups on CNF and the functionalization of block copolymer was characterized using thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and UV-vis spectroscopy. 相似文献
6.
Substrate‐Induced Synthesis of Nitrogen‐Doped Holey Graphene Nanocapsules for Advanced Metal‐Free Bifunctional Electrocatalysts 下载免费PDF全文
Zheye Zhang Tengfei Cao Shasha Liu Xianming Duan Li‐Min Liu Shuai Wang Yunqi Liu 《Particle & Particle Systems Characterization》2017,34(1)
The development of efficient metal‐free electrocatalysts for oxygen electrocatalysis is of great significance for various energy conversion devices. Herein, novel nitrogen‐doped holey graphene nanocapsules (NHGNs) are reported prepared by self‐assembly of graphene oxide nanosheets on the surface of amino‐functionalized silica template and NH3 activation with simultaneously enhanced nitrogen doping and etching of nanopores in graphene, followed by template etching. The silica template is demonstrated to show a substrate‐enhanced effect on nitrogen doping and etching of nanopores in graphene based on density functional theory calculations. Benefiting from the large surface area, unique pore distribution, and high surface functionality of nitrogen doping, the resulting NHGNs exhibit superior bifunctional electrocatalytic activity and durability for both oxygen reduction reaction and oxygen evolution reaction, which is similar to that of the commercial Pt/C and RuO2 electrocatalysts, respectively. This work presents an advance in developing new nitrogen‐doped graphene species for highly efficient metal‐free electrocatalysis. 相似文献
7.
The SiC/SiO2 deposition was performed to improve the oxidation resistive properties of carbon nanofiber (CNF) from electrospinning at elevated temperatures through sol-gel process. The stabilized polyacrylonitrile (PAN) fibers were coated with SiO2 followed by heat treatment up to 1000 and 1400 °C in an inert argon atmosphere. The chemical compositions of the CNFs surface heat-treated were characterized as C, Si and O existing as SiC and SiO2 compounds on the surface. The uniform and continuous coating improved the oxidation resistance of the carbon nanofibers. The residual weight of the composite was 70-80% and mixture of SiC, SiO2 and some residual carbon after exposure to air at 1000 °C. 相似文献
8.
Saumitra Saha Feng Wang Janay B. MacNaughton Alex Moewes Denalo P. Chong 《Journal of synchrotron radiation》2008,15(2):151-157
The impact of the amino fragment (–NH2) attachment on the inner‐shell structures and spectra of unsubstituted purine and the purine ring of adenine are studied. Density functional theory calculations, using the LB94/TZ2P//B3LYP/TZVP model, reveal significant site‐dependent electronic structural changes in the inner shell of the species. A condensed Fukui function indicates that all of the N and C sites, except for N(1) and C(5), demonstrate significant electrophilic reactivity (f? > 0.5 in |e|) in the unsubstituted purine. Once the amino fragment binds to the C(6) position of purine to form adenine, the electrophilic reactivity of these N and C sites is greatly reduced. As expected, the C(6) position experiences substantial changes in energy and charge transfer, owing to the formation of the C—NH2 bond in adenine. The present study reveals that the N1s spectra of adenine inherit the N1s spectra of the unsubstituted purine, whereas the C1s spectra experience significant changes although purine and adenine have geometrically similar carbon frames. The findings also indicate that the attachment of the NH2 fragment to purine exhibits deeply rooted influences to the inner‐shell structures of DNA/RNA bases. The present study suggests that some fragment‐based methods may not be applicable to spectral analyses in the inner shell. 相似文献
9.
Impact of nitrogen doping on growth and hydrogen impurity incorporation of thick nanocrystalline diamond films 下载免费PDF全文
A much larger amount of bonded hydrogen was found in thick nanocrystalline diamond(NCD) films produced by only adding 0.24% N2 into 4% CH4 /H2 plasma,as compared to the high quality transparent microcrystalline diamond(MCD) films,grown using the same growth parameters except for nitrogen.These experimental results clearly evidence that defect formation and impurity incorporation(for example,N and H) impeding diamond grain growth is the main formation mechanism of NCD upon nitrogen doping and strongly support the model proposed in the literature that nitrogen competes with CH x(x=1,2,3) growth species for adsorption sites. 相似文献
10.
Spectroscopic measurements of excited particles in a N2 gas RF plasma-assisted carbon laser ablation
M.A. Bratescu N. Sakura D. Yamaoka Y. Sakai H. Sugawara Y. Suda 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1083-1088
In this work, we investigated a carbon plasma plume produced by laser ablation of a graphite target in a nitrogen gas environment. The spatial distributions of C and N atoms were measured by time-resolved absorption spectroscopy. The spatial distributions of the relative densities of CN radicals, C2, and C3 molecules were measured using time-resolved emission spectroscopy. We determined that nitrogen gas produced an increase in carbon atom and molecule densities in the ablation plume. It was observed that the addition of RF plasma to the plume increased the CN radicals and C atom densities, and decreased the C2 and C3 molecule densities. The RF plasma changed the evolution of various fractional species of C, N, CN, C2, and C3 in the ablation plume. The chemical reactions with and without RF plasma were explained using the evolution and density of the fractional species of C, N, CN, C2, and C3in the plume. PACS 52.38.Mf; 42.62.Fi; 33.20.-t; 81.05.Uw 相似文献
11.
U. Chakravarty P. A. Naik B. S. Rao V. Arora H. Singhal G. M. Bhalerao A. K. Sinha P. Tiwari P. D. Gupta 《Applied physics. B, Lasers and optics》2011,103(3):571-577
A comparative experimental study of the X-ray emission in the water-window spectral region has been performed using carbon
nanofibers (CNFs) of different sizes and graphite plate targets, irradiated with ultra-short (Ti:sapphire) laser pulses. More
than an order of magnitude enhancement in the X-ray yield is observed from CNFs of 60-nm diameter with respect to graphite
targets. The X-ray emission from CNFs of 160-nm diameter was also high. The integrated X-ray yield of these carbon-based targets
scales with the laser intensity (I
L) as IL ~ 1.3-1.4I_{\mathrm{L}}^{\sim 1.3-1.4} in the intensity range of 4×1016–4×1017 W/cm2. The effect of the laser pulse duration on the X-ray emission from the CNFs was also studied by varying the pulse duration
from 45 fs up to 3 ps at a constant fluence of 2×104 J/cm2. The optimum laser pulse duration for maximum X-ray emission increases with the diameter of the CNFs used. The results are
explained from physical considerations of heating and hydrodynamic expansion of the CNF plasma in which resonance field enhancement
takes place while passing through two times the critical density. The results add to the efforts towards achieving an efficient
low-cost water-window X-ray source for microscopy. 相似文献
12.
Gas Chromatography Analysis of Discharge Products in N2‐CH4 Gas Mixture at Atmospheric Pressure: Study of Mimic Titan's Atmosphere 下载免费PDF全文
L. Torokova J. Watson F. Krcma V. Mazankova N. J. Mason G. Horvath S. Matejcik 《等离子体物理论文集》2015,55(6):470-480
In this paper, we report presence of various organic products formed in a flowing atmospheric glow discharge fed by gas mixture containing 1‐5 % of methane in nitrogen, which mimics the Titan's atmosphere. Gaseous products from the discharge exhaust were analysed by Gas Chromatography with Mass Spectrometry (GC‐MS). The experimental results revealed C2H2, HCN, and CH3CN as the major products. Various hydrocarbons and nitriles were the other determined gaseous products. Whilst many of these compounds have been predicted and/or observed in the Titan atmosphere, the present plasma experiments provide evidence of both the chemical complexity of Titan atmospheric processes and the mechanisms by which larger species grow prior to form the dust that should cover much of the Titan's surface. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
13.
On the Plasma Chemistry of an RF Discharge Containing Aluminium Tri‐Isopropoxide Studied by FTIR Spectroscopy 下载免费PDF全文
In Ar and Ar/N2 radio frequency (RF) discharges with admixtures of aluminium tri‐isopropoxide (ATI) the fragmentation of this metal‐organic precursor was studied by means of Fourier Transform Infrared (FTIR) spectroscopy using an optical long path cell providing an optical length of l = 17.2 m. The experiments were performed in an asymmetric capacitively coupled process plasma at a frequency of f = 13.56 MHz and at pres‐sure values in the range of p = 1–10.5 Pa. The discharge power was chosen between P = 10–100 W. Using FTIR spectroscopy the evolution of the concentrations of ATI and of six stable molecules, CH4, C2H2, C2H4, C2H6, CO and HCN, was monitored under flowing conditions at gas flows of Φtotal = 0.5–14.5 sccm in the discharge. The concentrations of the reaction products were measured tobe between 2 x 1012 molecules cm–3 as e.g. found for C2H4and C2H6, and 5 x 1013 molecules cm–3, as e.g. in the case of CO. In the plasma a complete dissociation of the precursor ATI was found at a power value of about P = 80 W independent on the admixture of Ar or N2. The fragmentation efficiency (FE) of the reaction products which originate from the ATI molecules ranges between 0.2 and 4 x 1016 molecules J–1 while the fragmentation rate (FR) reached up to 2.5 x 1018 molecules s–1. The multi component detection ability of the spectrometer served to analyse the carbon balance of the by‐product formation. For all experiments, the carbon balance never exceeded 25%. Therefore, in the plasmas the majority of the provided carbon is most likely deposited at the reactor walls or forms dust particles or higher molecular CxHy. The conversion efficiencies (CE) of the produced molecular species ranges between 0.1 x 1015 molecules J–1 for C2H4 and 5 x 1015 molecules J–1 for C2H6 depending on the discharge conditions of the RF plasma. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
14.
A Facile Strategy to Synthesize Cobalt‐Based Self‐Supported Material for Electrocatalytic Water Splitting 下载免费PDF全文
Li Gu Han Zhu DanNi Yu SongGe Zhang Jiawei Chen Juan Wang Meng Wan Ming Zhang MingLiang Du 《Particle & Particle Systems Characterization》2017,34(10)
Designing and developing active, robust, and noble‐metal‐free catalysts with superior stability for electrocatalytic water splitting is of critical importance but remains a grand challenge. Here, a facile strategy is provided to synthesize a series of Co‐based self‐supported electrode materials by combining electrospinning and chemical vapor deposition (CVD) technologies. The Co, Co3O4, Co9S8 nanoparticles (NPs) are formed in situ simultaneously with the formation of carbon nanofibers (CNFs) during the CVD process, respectively. The Co‐based NPs are uniformly distributed through the CNFs and they can be directly used as the electrode materials for hydrogen evolution reaction (HER) in acid and oxygen evolution reaction (OER) in alkaline. The Co9S8/CNFs membrane exhibits the best HER activity with overpotential of 165 mV at j = 10 mA cm?2 and Tafel slope of 83 mV dec?1 and OER activity with overpotential of 230 mV at j = 10 mA cm?2 and Tafel slope of 72 mV dec?1. The onion‐like graphitic layers formed around the NPs not only improve the electrical conductivity of the electrode but also prevent the separation of the NPs from the carbon matrix as well as the aggregation. 相似文献
15.
M. Tanemura T. Okita J. Tanaka H. Yamauchi L. Miao S. Tanemura R. Morishima 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,34(1-3):283-286
Glassy carbon plates, a Ni mesh coated with a carbon film and mechanically
polished graphite plates were Ar+ ion-bombarded with and without a
simultaneous Mo supply at room temperature. Conical protrusions were formed
on the sputtered surfaces, and in some cases carbon nanofibers (CNFs) 0.2–10 μm in length and 10–50 nm in diameter grew on the tips. The growth of CNF-tipped-cones was optimized in terms of the ion-incidence angle and the rate-ratio of sputtering and seeding. Oblique sputtering was proved to
be quite effective to grow the CNF-tipped-cones. Thus, the redeposited massive carbon atoms onto cones were thought to diffuse toward the cone tips, resulting in CNF formation. This growth mechanism was confirmed by transmission electron microscope (TEM) observation disclosing the
boundary-less structure between conical bases and CNFs. TEM observation of
CNF-tipped-cones also revealed no-hollow structure and an amorphous nature
of CNFs. Since this sputtering method is a room-temperature process and
quite straightforward, ion-induced CNFs promise to have myriad applications,
such as field emission sources for flat panel displays. 相似文献
16.
17.
The formation and decay of carbon and nitrogen atoms, CN radicals and C2 molecules were monitored using spatial‐ and time‐resolved emission spectroscopy in a plasma plume formed during laser ablation of a graphite target in nitrogen atmosphere. A simple exponential model was used to explain the effect of the individual chemical reactions and plasma dynamics on the measured kinetic characteristics. The succession of emissions C → N → CN was observed in the time‐resolved spectra, supporting the suggestion that the CN radical is formed mainly by the direct reaction C + N → CN or C2 + N2 → 2CN. The formation of CN radical was enhanced by the additional generation of atomic nitrogen through the RF discharge. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
18.
Iron sulfides are attractive anode materials for lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs) due to their high theoretical capacities, low cost, and eco‐friendliness. However, their real application is greatly hindered by the rapid capacity fading caused by the large volume changes and sluggish kinetics of iron sulfides during the charge and discharge processes. Combining with carbonaceous materials and tuning the structure at nanoscale are essential to address this issue. Here, a facile hydrothermal method coupled with a carbonization process is developed to synthesize a nano‐micro hybrid porous structure, which is composed of Fe7S8 nanoparticles embedded in nitrogen‐doped carbon framework (Fe7S8@NC‐PS). This hierarchical sphere is constructed by interconnected 2D nanowalls. The as‐prepared Fe7S8@NC‐PS electrodes reveal excellent rate capability and cycling stability in LIBs and SIBs. The remarkable electrochemical properties are attributed to the porous nano‐micro hybrid architecture and the high conductivity and structural stability of the nitrogen‐doped carbon framework. 相似文献
19.
采用等离子体增强热灯丝化学气相沉积方法,以甲烷和氢气为反应气体,在钨丝衬底上制备出准直的碳纳米纤维(CNFs),其生长密度小于10.6cm-2,长度为6—30μm,直径为60—100nm.并采用自制的双探针扫描电子显微镜系统,对所生长的单根CNF作了场发射特性研究.结果表明,其场发射开启电压约为5V/μm,相应的发射电流达到20μA/cm2,同时,对不同长度的CNFs及单根CNF不同位置的场发射研究表明,场发射电流的大小不仅与材料本身的功函数、外电场场强、材料的微观结构以及宏观的几何结构有关,而且电子在输运过程中所受到的散射也是决定场发射电流大小的关键因素.
关键词:
碳纳米纤维
化学气相沉积
场发射
扫描电子显微镜 相似文献