High-yield synthesis of multi-walled carbon nanotubes by arc discharge in liquid nitrogen

Synthesis of multi-walled carbon nanotubes (MWNTs) by arc discharge in liquid nitrogen is reported. As liquid nitrogen substituted both vacuum and cooling systems, high-quality MWNTs were produced at a low cost. The content of the MWNTs can be as high as 70% of the reaction product. Auger-spectroscopy analysis revealed that no nitrogen is incorporated in the MWNTs. This method can be an economical route for the mass production of highly crystalline MWNTs. Received: 5 July 2002 / Accepted: 8 July 2002 / Published online: 10 September 2002 RID="*" ID="*"Corresponding author. Fax: +82-54/279-8298, E-mail: ce20047@postech.ac.kr     

Morphology and electronic properties of carbon nanotubes synthesized by arc discharge in CF4gas

The morphology of carbon nanotubes synthesized by arc discharge in a CF₄gas atmosphere was investigated by scanning electron microscopy and transmission electron microscopy. The electronic properties of these nanotubes were investigated by electron spin resonance. The synthesis conditions in CF₄gas were then compared with those in CH₄, H₂and He based on these results. Furthermore, the mechanism of tube growth in CF₄gas was discussed briefly.     

Synthesis of single wall carbon nanotubes by using arc discharge technique in nitrogen atmosphere

Single wall carbon nanotubes (SWNTs) were prepared with arc discharge technique using Ni/Co carbon composite rod in He, Ar, and N₂ atmosphere, respectively. The yield and the diameter distribution of them were compared with each other. The results show that N₂ atmosphere at low pressure gives the highest yield for the formation of SWNTs, almost comparable to that obtained with laser furnace technique. It also declares that He atmosphere seems to make SWNTs having smaller diameter distribution than those obtained in N₂ and Ar atmosphere. These findings were summarized and used for the discussion related to the formation mechanism of SWNTs.     

Morphology-controlled growth of tetrapod ZnO nanostructures by direct arc discharge

A novel buttress-root shaped ZnO tetrapod-like nanostructure and a classic tetrapod ZnO nanostructure were synthesized by a direct reaction of high-purity Zn granules with oxygen using an arc discharge method. The morphology of the products could be controlled by adjusting the oxygen partial pressure. The buttress-root shaped tetrapod-like nanostructure contains three triangular nanosheets, the diameters of nanoarms vary between 50 and 80 nm, and the angle between every two arms is about 109.5°. A nanorod-centered growth model has been proposed to explain the novel nanostructure. An ultraviolet (UV) emission band located at 389 nm (3.18 eV) and a broad blue emission band centered at 484 nm (2.57 eV) were observed at room temperature.     

Effects of gravity on single-wall carbon nanotubes synthesized by arc in water

The method using arc discharge in liquid is a simple and inexpensive route for synthesis of carbon nanotubes and other related nano-materials. In this study, we report the synthesis of single-wall carbon nanotubes (SWCNTs) by means of the arc-in-water method under extremely low gravity conditions. The strong heat convection caused by the arc plasma is suppressed under such conditions. Therefore, the boiling flow behavior and temperature distribution have been stabilized in low gravity. As a result, the possibility of the chirality control of SWCNTs by applying extremely low gravity was revealed; namely, the yield of semiconducting SWCNTs was increased and several SWCNTs of specific diameters turned out to be prominent under extremely low gravity conditions. PACS 52.80.Wq; 68.37.Lp; 81.07.De; 81.70.Ha; 82.80.Gk     

Iron nanoparticles grown in a carbon arc discharge

Summary Iron particles, encapsulated by graphite layers, were produced by means of the Kratschmer arc discharge method in an iron pentacarbonyl atmosphere. The M?ssbauer effect is dominated by the vibration of the particles as a whole. Superparamegnetism is dominant for iron oxide particles. No endohedral iron fullerenes were observed, contrary to a previous report. Paper presented at ICAME-95, Rimini, 10–16 September 1995.     

含氢电极脉冲放电等离子体特性诊断

利用飞行时间质谱法诊断了含氢电极脉冲真空弧离子源放电等离子体成分、离子电荷状态及离子扩散速度等特性.实验结果表明,含氢电极脉冲真空弧离子源放电等离子体的离子成分主要由H+,Ti+,Ti2+和Ti3+组成,其中Ti2+占主要部分.当放电电流为40～80 A时,Ti离子的平均电荷数在1.95～2.13之间,随着放电电流的增...     

含氢电极脉冲放电等离子体特性诊断

利用飞行时间质谱法诊断了含氢电极脉冲真空弧离子源放电等离子体成分、离子电荷状态及离子扩散速度等特性。实验结果表明,含氢电极脉冲真空弧离子源放电等离子体的离子成分主要由H+,Ti+,Ti2+和Ti3+组成,其中Ti2+占主要部分。当放电电流为40～80 A时,Ti离子的平均电荷数在1.95～2.13之间,随着放电电流的增大,平均电荷数也会增加。同时诊断了不同离子的扩散速度,其值均在104 m/s量级,但不同离子的扩散速度有所不同。     

Parameters of free-burning arc discharge plasma in air with silver-based electrodes

We have used optical spectroscopy to study the radial temperature profiles for an electric arc plasma between silver electrodes and electrodes made from composite materials based on silver (Ag-CdO). We studied the structural changes in the working layers of the electrodes by metallography. We established that the parameters of the arc discharge plasma are determined by the condition of the electrode surface. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 3, pp. 375–379, May–June, 2006.     

Growth of small diameter multi-walled carbon nanotubes by arc discharge process

Multi-walled carbon nanotubes （MWCNTs） are grown by arc discharge method in a controlled methane environment. The arc discharge is produced between two graphite electrodes at the ambient pressures of 100 tort, 300 torr, and 500 torr. Arc plasma parameters such as temperature and density are estimated to investigate the influences of the ambient pressure and the contributions of the ambient pressure to the growth and the structure of the nanotubes. The plasma temperature and density are observed to increase with the increase in the methane ambient pressure. The samples of MWCNT synthesized at different ambient pressures are analyzed using transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. An increase in the growth of MWCNT and a decrease in the inner tube diameter are observed with the increase in the methane ambient pressure.     

Time-resolved laser-induced fluorescence of atomic nitrogen in afree-burning arc discharge

An experiment to detect ground-state atomic nitrogen in an atmospheric-pressure argon-nitrogen free-burning 200 A arc by time-resolved two-photon laser-induced fluorescence is described. The time decay of the fluorescence pulses showed that quenching of the laser-excited state is rapid. Upper bound estimates of the pulse-decay time were determined as a function of radius, and were found to be on the order of 1 ns, and to decrease with increasing radii. The implications of rapid quenching of the laser-excited state to the application of laser-induced fluorescence as a plasma diagnostic tool are discussed     

Morphology and optical properties of zinc oxide nanostructures synthesized by the methods of thermal and discharge sputtering

Zinc oxide nanostructures are obtained by the methods of electrothermal and discharge sputtering in gaseous and liquid media. Structure and phase peculiarities of synthesized samples, as well as morphology and luminescence properties of synthesized structures with and without doping are examined. The luminescence spectra of the deposited zinc oxide nanostructures have characteristic luminescence maxima (at λ = 380 and 520 nm) associated with exciton emission and defects in nanocrystals, respectively.     

Comparison between the parameters of a one-phase arc with copper and steel electrodes ignited in nitrogen and in air

The characteristics of an open one-phase arc with gas stabilization in electrode units are studied. The arc is ignited between copper and steel electrodes in nitrogen and in air. The amplitude values of the current and voltage reach 9–10 A and 650–1600 V, respectively. Current and voltage oscillograms, as well as dynamic I–V characteristics, are presented. The time variation of the conductivity, the discharge power, and the spectral composition and integral radiation losses of the arc column are compared when the electrodes are made of copper and steel.     

A novel method for synthesis of colloidal silver nanoparticles by arc discharge in liquid

This paper presents a novel, inexpensive and one-step approach for synthesis of silver nanoparticles (Ag NPs) using arc discharge between titanium electrodes in AgNO₃ solution. The resulting nanoparticles were characterized using UV–Vis spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Silver nanoparticles of 18 nm diameter were formed during reduction of AgNO₃ in plasma discharge zone. Optical absorption spectroscopy of as prepared samples at 15 A arc current in AgNO₃ solution shows a surface plasmon resonance around 410 nm. It was found that sodium citrate acts as a stabilizer and surface capping agent of the colloidal nanoparticles. SEM images exhibit the increase of reduced nanoparticles in 6 min arc duration compared with 1 min arc duration. TEM image of the sample prepared at 6 min arc duration shows narrow size distribution with 18 nm mean particle size. Antibacterial activities of silver nanoparticles were investigated at the presence of Escherichia coli (E-coli) bacteria.     

Carbon nanotubes and nanostructures grown from diamond-like carbon and polyethylene

We report a simple way to synthesize carbon nanotubes and nanostructures from the solid phase. Vacuum annealing of diamond-like carbon (DLC) films or polyethylene mixed with catalyst in argon atmosphere leads to the formation of nanotubes and nanostructures. High-resolution transmission electron microscopy studies reveal highly graphitized multi-walled nanotubes (MWNTs) or amorphous fibre-like structures, depending on the catalyst amount. This synthesis process may give a new approach to understanding the phase transition of different carbon allotropes into nanotubes or nanostructures. Received: 3 July 2001 / Accepted: 3 July 2001 / Published online: 2 October 2001     

Ultra fine carbon nitride nanocrystals synthesized by laser ablation in liquid solution

Crystalline carbon nitride nanopowders and nanorods have been successfully synthesized at room temperature and pressure using the novel technique of pulsed laser ablation of a graphite target in liquid ammonia solution. High-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and Fourier transform infrared spectroscopy (FTIR) were used to systematically study the morphology, nanostructure and chemical bonding. The experimental composition and structure of the nanoparticles are consistent with the theoretical calculations for α-C₃N₄. After 2 h ablation the particles had a size distribution ∼8–12 nm, whereas after 5 h ablation the particles had grown into nanorod-like structures with a crystalline C₃N₄ tip. A formation mechanism for these nanorods is proposed whereby nanoparticles are first synthesized via rapid formation of an embryonic particle, followed by a slow growth, eventually leading to a one-dimensional nanorod structure.